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Ly VT, Baudin PV, Pansodtee P, Jung EA, Voitiuk K, Rosen YM, Willsey HR, Mantalas GL, Seiler ST, Selberg JA, Cordero SA, Ross JM, Rolandi M, Pollen AA, Nowakowski TJ, Haussler D, Mostajo-Radji MA, Salama SR, Teodorescu M. Picroscope: low-cost system for simultaneous longitudinal biological imaging. Commun Biol 2021; 4:1261. [PMID: 34737378 PMCID: PMC8569150 DOI: 10.1038/s42003-021-02779-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 10/05/2021] [Indexed: 01/02/2023] Open
Abstract
Simultaneous longitudinal imaging across multiple conditions and replicates has been crucial for scientific studies aiming to understand biological processes and disease. Yet, imaging systems capable of accomplishing these tasks are economically unattainable for most academic and teaching laboratories around the world. Here, we propose the Picroscope, which is the first low-cost system for simultaneous longitudinal biological imaging made primarily using off-the-shelf and 3D-printed materials. The Picroscope is compatible with standard 24-well cell culture plates and captures 3D z-stack image data. The Picroscope can be controlled remotely, allowing for automatic imaging with minimal intervention from the investigator. Here, we use this system in a range of applications. We gathered longitudinal whole organism image data for frogs, zebrafish, and planaria worms. We also gathered image data inside an incubator to observe 2D monolayers and 3D mammalian tissue culture models. Using this tool, we can measure the behavior of entire organisms or individual cells over long-time periods.
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Affiliation(s)
- Victoria T Ly
- Department of Electrical and Computer Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA.
| | - Pierre V Baudin
- Department of Electrical and Computer Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Pattawong Pansodtee
- Department of Electrical and Computer Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Erik A Jung
- Department of Electrical and Computer Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Kateryna Voitiuk
- Department of Biomolecular Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Yohei M Rosen
- Department of Biomolecular Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Helen Rankin Willsey
- Department of Psychiatry and Behavioral Sciences, Weill Institute for Neurosciences, University of California San Francisco, San Francisco, CA, 94143, USA
| | - Gary L Mantalas
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Spencer T Seiler
- Department of Biomolecular Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - John A Selberg
- Department of Electrical and Computer Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Sergio A Cordero
- Department of Electrical and Computer Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Jayden M Ross
- The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California San Francisco, San Francisco, CA, 94143, USA
- Department of Anatomy, University of California San Francisco, San Francisco, CA, 94143, USA
| | - Marco Rolandi
- Department of Electrical and Computer Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Alex A Pollen
- The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California San Francisco, San Francisco, CA, 94143, USA
- Department of Neurology, University of California San Francisco, San Francisco, CA, 94143, USA
| | - Tomasz J Nowakowski
- The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California San Francisco, San Francisco, CA, 94143, USA
- Department of Anatomy, University of California San Francisco, San Francisco, CA, 94143, USA
| | - David Haussler
- Department of Biomolecular Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
- Howard Hughes Medical Institute, University of California Santa Cruz, Santa Cruz, CA, 95064, USA
- UC Santa Cruz Genomics Institute, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Mohammed A Mostajo-Radji
- The Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California San Francisco, San Francisco, CA, 94143, USA
- Department of Neurology, University of California San Francisco, San Francisco, CA, 94143, USA
- UC Santa Cruz Genomics Institute, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Sofie R Salama
- Department of Biomolecular Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
- Howard Hughes Medical Institute, University of California Santa Cruz, Santa Cruz, CA, 95064, USA
- UC Santa Cruz Genomics Institute, University of California Santa Cruz, Santa Cruz, CA, 95060, USA
| | - Mircea Teodorescu
- Department of Electrical and Computer Engineering, University of California Santa Cruz, Santa Cruz, CA, 95060, USA.
- UC Santa Cruz Genomics Institute, University of California Santa Cruz, Santa Cruz, CA, 95060, USA.
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2
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Orton F, Svanholm S, Jansson E, Carlsson Y, Eriksson A, Uren Webster T, McMillan T, Leishman M, Verbruggen B, Economou T, Tyler CR, Berg C. A laboratory investigation into features of morphology and physiology for their potential to predict reproductive success in male frogs. PLoS One 2020; 15:e0241625. [PMID: 33175903 PMCID: PMC7657548 DOI: 10.1371/journal.pone.0241625] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 10/16/2020] [Indexed: 11/18/2022] Open
Abstract
Amphibian populations are declining globally, however, the contribution of reduced reproduction to declines is unknown. We investigated associations between morphological (weight/snout-vent length, nuptial pad colour/size, forelimb width/size) and physiological (nuptial pad/testis histomorphology, plasma hormones, gene expression) features with reproductive success in males as measured by amplexus success and fertility rate (% eggs fertilised) in laboratory maintained Silurana/Xenopus tropicalis. We explored the robustness of these features to predict amplexus success/fertility rate by investigating these associations within a sub-set of frogs exposed to anti-androgens (flutamide (50 μg/L)/linuron (9 or 45 μg/L)). In unexposed males, nuptial pad features (size/colour/number of hooks/androgen receptor mRNA) were positively associated with amplexus success, but not with fertility rate. In exposed males, many of the associations with amplexus success differed from untreated animals (they were either reversed or absent). In the exposed males forelimb width/nuptial pad morphology were also associated with fertility rate. However, a more darkly coloured nuptial pad was positively associated with amplexus success across all groups and was indicative of androgen status. Our findings demonstrate the central role for nuptial pad morphology in reproductive success in S. tropicalis, however, the lack of concordance between unexposed/exposed frogs complicates understanding of the utility of features of nuptial pad morphology as biomarkers in wild populations. In conclusion, our work has indicated that nuptial pad and forelimb morphology have potential for development as biomarkers of reproductive health in wild anurans, however, further research is needed to establish this.
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Affiliation(s)
- Frances Orton
- School of Health and Life Sciences, University of the West of Scotland, Paisley, United Kingdom
| | - Sofie Svanholm
- Department of Environmental Toxicology, Uppsala University, Uppsala, Sweden
| | - Erika Jansson
- Department of Environmental Toxicology, Uppsala University, Uppsala, Sweden
| | - Ylva Carlsson
- Department of Environmental Toxicology, Uppsala University, Uppsala, Sweden
| | - Andreas Eriksson
- Department of Environmental Toxicology, Uppsala University, Uppsala, Sweden
| | | | - Tamara McMillan
- School of Health and Life Sciences, University of the West of Scotland, Paisley, United Kingdom
| | - Martin Leishman
- School of Health and Life Sciences, University of the West of Scotland, Paisley, United Kingdom
| | - Bas Verbruggen
- College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Theo Economou
- College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Charles R. Tyler
- College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Cecilia Berg
- Department of Environmental Toxicology, Uppsala University, Uppsala, Sweden
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3
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Kakebeen AD, Chitsazan AD, Williams MC, Saunders LM, Wills AE. Chromatin accessibility dynamics and single cell RNA-Seq reveal new regulators of regeneration in neural progenitors. eLife 2020; 9:e52648. [PMID: 32338593 PMCID: PMC7250574 DOI: 10.7554/elife.52648] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 04/25/2020] [Indexed: 12/24/2022] Open
Abstract
Vertebrate appendage regeneration requires precisely coordinated remodeling of the transcriptional landscape to enable the growth and differentiation of new tissue, a process executed over multiple days and across dozens of cell types. The heterogeneity of tissues and temporally-sensitive fate decisions involved has made it difficult to articulate the gene regulatory programs enabling regeneration of individual cell types. To better understand how a regenerative program is fulfilled by neural progenitor cells (NPCs) of the spinal cord, we analyzed pax6-expressing NPCs isolated from regenerating Xenopus tropicalis tails. By intersecting chromatin accessibility data with single-cell transcriptomics, we find that NPCs place an early priority on neuronal differentiation. Late in regeneration, the priority returns to proliferation. Our analyses identify Pbx3 and Meis1 as critical regulators of tail regeneration and axon organization. Overall, we use transcriptional regulatory dynamics to present a new model for cell fate decisions and their regulators in NPCs during regeneration.
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Affiliation(s)
| | | | | | - Lauren M Saunders
- Department of Genome Sciences, University of WashingtonSeattleUnited States
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4
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Evans BJ, Gansauge MT, Stanley EL, Furman BLS, Cauret CMS, Ofori-Boateng C, Gvoždík V, Streicher JW, Greenbaum E, Tinsley RC, Meyer M, Blackburn DC. Xenopus fraseri: Mr. Fraser, where did your frog come from? PLoS One 2019; 14:e0220892. [PMID: 31509539 PMCID: PMC6738922 DOI: 10.1371/journal.pone.0220892] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 07/23/2019] [Indexed: 01/06/2023] Open
Abstract
A comprehensive, accurate, and revisable alpha taxonomy is crucial for biodiversity studies, but is challenging when data from reference specimens are difficult to collect or observe. However, recent technological advances can overcome some of these challenges. To illustrate this, we used modern approaches to tackle a centuries-old taxonomic enigma presented by Fraser’s Clawed Frog, Xenopus fraseri, including whether X. fraseri is different from other species, and if so, where it is situated geographically and phylogenetically. To facilitate these inferences, we used high-resolution techniques to examine morphological variation, and we generated and analyzed complete mitochondrial genome sequences from all Xenopus species, including >150-year-old type specimens. Our results demonstrate that X. fraseri is indeed distinct from other species, firmly place this species within a phylogenetic context, and identify its minimal geographic distribution in northern Ghana and northern Cameroon. These data also permit novel phylogenetic resolution into this intensively studied and biomedically important group. Xenopus fraseri was formerly thought to be a rainforest endemic placed alongside species in the amieti species group; in fact this species occurs in arid habitat on the borderlands of the Sahel, and is the smallest member of the muelleri species group. This study illustrates that the taxonomic enigma of Fraser’s frog was a combined consequence of sparse collection records, interspecies conservation and intraspecific polymorphism in external anatomy, and type specimens with unusual morphology.
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Affiliation(s)
- Ben J. Evans
- Department of Biology, McMaster University, Hamilton, ON, Canada
- * E-mail:
| | - Marie-Theres Gansauge
- Max Planck Institute for Evolutionary Anthropology, Deutscher Platz, Leipzig, Germany
| | - Edward L. Stanley
- Florida Museum of Natural History, University of Florida, Gainesville, FL, United States of America
| | - Benjamin L. S. Furman
- Department of Biology, McMaster University, Hamilton, ON, Canada
- Department of Zoology, Beaty Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
| | | | | | - Václav Gvoždík
- Institute of Vertebrate Biology of the Czech Academy of Sciences, Czech Republic
- Department of Zoology, National Museum, Prague, Czech Republic
| | | | - Eli Greenbaum
- Department of Biological Sciences, University of Texas at El Paso, El Paso, United States of America
| | - Richard C. Tinsley
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
| | - Matthias Meyer
- Max Planck Institute for Evolutionary Anthropology, Deutscher Platz, Leipzig, Germany
| | - David C. Blackburn
- Florida Museum of Natural History, University of Florida, Gainesville, FL, United States of America
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5
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Kwong-Brown U, Tobias ML, Elias DO, Hall IC, Elemans CPH, Kelley DB. The return to water in ancestral Xenopus was accompanied by a novel mechanism for producing and shaping vocal signals. eLife 2019; 8:e39946. [PMID: 30618379 PMCID: PMC6324873 DOI: 10.7554/elife.39946] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 11/23/2018] [Indexed: 12/21/2022] Open
Abstract
Listeners locate potential mates using species-specific vocal signals. As tetrapods transitioned from water to land, lungs replaced gills, allowing expiration to drive sound production. Some frogs then returned to water. Here we explore how air-driven sound production changed upon re-entry to preserve essential acoustic information on species identity in the secondarily aquatic frog genus Xenopus. We filmed movements of cartilage and muscles during evoked sound production in isolated larynges. Results refute the current theory for Xenopus vocalization, cavitation, and favor instead sound production by mechanical excitation of laryngeal resonance modes following rapid separation of laryngeal arytenoid discs. Resulting frequency resonance modes (dyads) are intrinsic to the larynx rather than due to neuromuscular control. Dyads are a distinctive acoustic signature. While their component frequencies overlap across species, their ratio is shared within each Xenopus clade providing information on species identity that could facilitate both conspecific localization and ancient species divergence. Editorial note This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
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Affiliation(s)
- Ursula Kwong-Brown
- Department of Biological SciencesColumbia UniversityNew YorkUnited States
| | - Martha L Tobias
- Department of Biological SciencesColumbia UniversityNew YorkUnited States
| | - Damian O Elias
- Department of Environmental Science, Policy and ManagementUniversity of California, BerkeleyBerkeleyUnited States
| | - Ian C Hall
- Department of Biological SciencesColumbia UniversityNew YorkUnited States
| | - Coen PH Elemans
- Department of BiologyUniversity of Southern DenmarkCampusvejDenmark
| | - Darcy B Kelley
- Department of Biological SciencesColumbia UniversityNew YorkUnited States
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6
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Evans BJ, Carter TF, Greenbaum E, Gvoždík V, Kelley DB, McLaughlin PJ, Pauwels OSG, Portik DM, Stanley EL, Tinsley RC, Tobias ML, Blackburn DC. Genetics, Morphology, Advertisement Calls, and Historical Records Distinguish Six New Polyploid Species of African Clawed Frog (Xenopus, Pipidae) from West and Central Africa. PLoS One 2015; 10:e0142823. [PMID: 26672747 PMCID: PMC4682732 DOI: 10.1371/journal.pone.0142823] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 10/27/2015] [Indexed: 01/08/2023] Open
Abstract
African clawed frogs, genus Xenopus, are extraordinary among vertebrates in the diversity of their polyploid species and the high number of independent polyploidization events that occurred during their diversification. Here we update current understanding of the evolutionary history of this group and describe six new species from west and central sub-Saharan Africa, including four tetraploids and two dodecaploids. We provide information on molecular variation, morphology, karyotypes, vocalizations, and estimated geographic ranges, which support the distinctiveness of these new species. We resurrect Xenopus calcaratus from synonymy of Xenopus tropicalis and refer populations from Bioko Island and coastal Cameroon (near Mt. Cameroon) to this species. To facilitate comparisons to the new species, we also provide comments on the type specimens, morphology, and distributions of X. epitropicalis, X. tropicalis, and X. fraseri. This includes significantly restricted application of the names X. fraseri and X. epitropicalis, the first of which we argue is known definitively only from type specimens and possibly one other specimen. Inferring the evolutionary histories of these new species allows refinement of species groups within Xenopus and leads to our recognition of two subgenera (Xenopus and Silurana) and three species groups within the subgenus Xenopus (amieti, laevis, and muelleri species groups).
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Affiliation(s)
- Ben J. Evans
- Department of Biology, Life Sciences Building Room 328 McMaster University, Hamilton, Ontario, Canada
- * E-mail:
| | - Timothy F. Carter
- Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada
| | - Eli Greenbaum
- Department of Biological Sciences, University of Texas at El Paso, El Paso, Texas, United States of America
| | - Václav Gvoždík
- Institute of Vertebrate Biology, Czech Academy of Sciences, Kvetna 8, Brno, Czech Republic
- Department of Zoology, National Museum, Prague, Czech Republic
| | - Darcy B. Kelley
- Department of Biological Sciences, Columbia University, New York, New York, United States of America
| | - Patrick J. McLaughlin
- Department of Biology, Papadakis Integrated Sciences Building, Drexel University, Philadelphia, Pennsylvania, United States of America
| | - Olivier S. G. Pauwels
- Département des Vertébrés Récents, Instítut Royal des Sciences Naturelles de Belgique, Brussels, Belgium
| | - Daniel M. Portik
- Museum of Vertebrate Zoology, University of California, Berkeley, California, United States of America
| | - Edward L. Stanley
- California Academy of Sciences, San Francisco, California, United States of America
| | - Richard C. Tinsley
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
| | | | - David C. Blackburn
- California Academy of Sciences, San Francisco, California, United States of America
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Petrov P, Krachunov M, Vassilev D. A semi-automated approach for anatomical ontology mapping. J Integr Bioinform 2013; 10:221. [PMID: 23549604 DOI: 10.2390/biecoll-jib-2013-221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Revised: 03/22/2013] [Accepted: 04/03/2013] [Indexed: 06/02/2023] Open
Abstract
This paper presents a study in the domain of semi-automated and fully-automated ontology mapping. A process for inferring additional cross-ontology links within the domain of anatomical ontologies is presented and evaluated on pairs from three model organisms. The results of experiments performed with various external knowledge sources and scoring schemes are discussed.
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Affiliation(s)
- Peter Petrov
- Faculty of Mathematics and Informatics, Sofia University St. Kliment Ohridski, 5 James Bourchier Blvd., 1164 Sofia, Bulgaria
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8
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Abstract
Since the advent of computational methods in biology, the quantity of biological data has grown exponentially. These data support genomic, genetic, developmental, and other forms of biological experimentation. The number of on-line resources has kept pace with the growth in data. Xenopus has perhaps lagged some of the other model organisms in developing resources, but is now quickly catching up. There are now a number of well-established and developing resources for Xenopus. This chapter looks beyond the widely known public databases, Genbank and the EBI, and describes how the researcher can use a number of central sites such as Xenbase, UniProtKB, and major genome browsers to navigate to a variety of different resources.
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Affiliation(s)
- Jeff Bowes
- Department of Biological Sciences, University of Calgary, Calgary, AB, Canada.
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9
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Abstract
Lens regeneration among vertebrates is basically restricted to some amphibians. The most notable cases are the ones that occur in premetamorphic frogs and in adult newts. Frogs and newts regenerate their lens in very different ways. In frogs the lens is regenerated by transdifferentiation of the cornea and is limited only to a time before metamorphosis. On the other hand, regeneration in newts is mediated by transdifferentiation of the pigment epithelial cells of the dorsal iris and is possible in adult animals as well. Thus, the study of both systems could provide important information about the process. Molecular tools have been developed in frogs and recently also in newts. Thus, the process has been studied at the molecular and cellular levels. A synthesis describing both systems was long due. In this review we describe the process in both Xenopus and the newt. The known molecular mechanisms are described and compared.
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Affiliation(s)
- Jonathan J Henry
- Department of Cell and Developmental Biology, University of Illinois, Urbana, IL 61801, USA.
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10
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Gyllenhammar I, Holm L, Eklund R, Berg C. Reproductive toxicity in Xenopus tropicalis after developmental exposure to environmental concentrations of ethynylestradiol. Aquat Toxicol 2009; 91:171-178. [PMID: 18692912 DOI: 10.1016/j.aquatox.2008.06.019] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Revised: 06/26/2008] [Accepted: 06/27/2008] [Indexed: 05/26/2023]
Abstract
Reproductive disorders in wildlife and humans have been linked to developmental exposure to endocrine disrupting chemicals. In frog tadpoles, environmental concentrations of ethynylestradiol (EE(2)) disrupt gonadal differentiation which results in female-biased sex ratios at metamorphosis indicating sex-reversal of genotypic males. It is not known if developmental exposure to estrogens results in reduced reproductive success in amphibians. The objective of this work was to investigate if exposure to environmentally relevant concentrations of EE(2) during sex differentiation impairs reproductive organ development, fertility, and sexual behavior in adult frogs. A specific aim was to evaluate if testicular structure and function was affected in males that were not sex-reversed. Xenopus tropicalis tadpoles were exposed until metamorphosis to 6, 60, and 600 pM EE(2). Eight months after metamorphosis, reproductive organ morphology and fertility were evaluated. Larval EE(2)-exposure caused an increased proportion of phenotypic females indicating that sex-reversal of genotypic males is persistent. Sex-reversal was implied at concentrations as low as 6 pM (1.8 ng/l), which is comparable to levels observed in the environment. EE(2)-exposed males that were not sex-reversed had a significantly reduced fertilization rate compared with control males. Histological evaluation revealed that EE(2)-exposed males had a reduced amount of spermatozoa in the testis. Among frogs with ovaries there was a significantly higher percentage that lacked oviducts in the group exposed to 600 pM EE(2) compared with control females. No effect of EE(2) on sexual behavior was noted. The results indicate that reproduction in wild frogs might be impaired by estrogenic environmental pollutants. Similarities between the present effects and those reported in fish, birds and mammals after developmental exposure to estrogens suggest that X. tropicalis is a promising animal model for research on developmental reproductive toxicity.
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Affiliation(s)
- Irina Gyllenhammar
- Department of Environmental Toxicology, Uppsala University, Centre for Reproductive Biology in Uppsala (CRU), Norbyvägen 18A, 75236 Uppsala, Sweden.
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11
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Miura S, Hanaoka K, Togashi S. Skeletogenesis in Xenopus tropicalis: characteristic bone development in an anuran amphibian. Bone 2008; 43:901-9. [PMID: 18692165 DOI: 10.1016/j.bone.2008.07.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 06/29/2008] [Accepted: 07/03/2008] [Indexed: 10/21/2022]
Abstract
In mammals and birds, most of the skeletal bones develop via endochondral ossification. Chondrocytes in the cartilaginous anlagen undergo processes of maturation such as hypertrophy, calcification and apoptosis. Concomitantly, osteoblasts are recruited to replace the cartilage scaffold gradually with bone matrix and become osteocytes in the trabecular bones. Throughout the successive development of bones, several gene products have been identified as being the components of the molecular mechanism regulating bone development. Transcription factor SOX9 plays essential roles during developmental steps from undifferentiated mesenchymal cells to proliferating chondrocytes, meanwhile, it inhibits transition of proliferating chondrocytes to hypertrophy. Other transcription factors RUNX2 and OSTERIX are critical in osteoblast differentiation, and RUNX2 is also essential for chondrocyte maturation such as hypertrophy and matrix mineralization. GDF5, a protein belonging to the transforming growth factor beta superfamily, is involved in joint formation and chondrogenesis. The limb skeleton of one of the ancestral tetrapod, anuran amphibians also develops through cartilaginous anlagen to bones, but their skeletogenesis has some unique characteristics compared with that of mammals and birds. Anuran amphibians develop and grow with less bone trabeculae and poor epiphyseal growth plates, and its endochondral ossification was found to be a delayed process. In order to address the characteristic skeletal development of anuran amphibians, we cloned Xenopus tropicalis RUNX2 (Xt-runx2), OSTERIX (Xt-osterix) and GDF5 (Xt-gdf5) homologue, and observed expression patterns together with Xt-sox9. In X. tropicalis limbs, histological observation and section in situ hybridization analysis suggest that Xt-SOX9 is involved in chondrogenesis, Xt-RUNX2 and Xt-OSTERIX are involved in osteogenesis, and Xt-GDF5 is involved in joint formation. In the cartilaginous anlagen, Xt-runx2 expression was found in perichondrium and immature chondrocytes as seen in other vertebrates. However, Xt-runx2 expression in enlarged chondrocytes was weak and dissimilar to common hypertrophic chondrocytes. These observations suggest that weak Xt-runx2 expression in maturing chondrocytes affects characteristic bone development in X. tropicalis long bones.
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Affiliation(s)
- Shinichirou Miura
- Laboratory of Molecular Embryology, Department of Bioscience, School of Science, Kitasato University, 1-15-1, Kitasato, Sagamihara, Kanagawa, 228-8555, Japan.
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12
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Aw S, Adams DS, Qiu D, Levin M. H,K-ATPase protein localization and Kir4.1 function reveal concordance of three axes during early determination of left-right asymmetry. Mech Dev 2008; 125:353-72. [PMID: 18160269 PMCID: PMC2346612 DOI: 10.1016/j.mod.2007.10.011] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Revised: 10/05/2007] [Accepted: 10/24/2007] [Indexed: 12/23/2022]
Abstract
Consistent laterality is a fascinating problem, and study of the Xenopus embryo has led to molecular characterization of extremely early steps in left-right patterning: bioelectrical signals produced by ion pumps functioning upstream of asymmetric gene expression. Here, we reveal a number of novel aspects of the H+/K+-ATPase module in chick and frog embryos. Maternal H+/K+-ATPase subunits are asymmetrically localized along the left-right, dorso-ventral, and animal-vegetal axes during the first cleavage stages, in a process dependent on cytoskeletal organization. Using a reporter domain fused to molecular motors, we show that the cytoskeleton of the early frog embryo can provide asymmetric, directional information for subcellular transport along all three axes. Moreover, we show that the Kir4.1 potassium channel, while symmetrically expressed in a dynamic fashion during early cleavages, is required for normal LR asymmetry of frog embryos. Thus, Kir4.1 is an ideal candidate for the K+ ion exit path needed to allow the electroneutral H+/K+-ATPase to generate voltage gradients. In the chick embryo, we show that H+/K+-ATPase and Kir4.1 are expressed in the primitive streak, and that the known requirement for H+/K+-ATPase function in chick asymmetry does not function through effects on the circumferential expression pattern of Connexin43. These data provide details crucial for the mechanistic modeling of the physiological events linking subcellular processes to large-scale patterning and suggest a model where the early cytoskeleton sets up asymmetric ion flux along the left-right axis as a system of planar polarity functioning orthogonal to the apical-basal polarity of the early blastomeres.
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Affiliation(s)
- Sherry Aw
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
| | - Dany S. Adams
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
| | - Dayong Qiu
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
| | - Michael Levin
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
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13
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Abstract
This review presents the fascinating neurobiology underlying the development of the frog optic tectum, the brain structure where the two separate inputs from the two eye are combined into a single, integrated map. In the species Xenopus laevis, binocular visual information has a dramatic impact on axon growth and connectivity, and the formation of binocular connections in this system provides a rich basis for both theoretical and experimental investigations.
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Affiliation(s)
- Susan B Udin
- Department of Physiology and Biophysics, Program in Neuroscience, State University of New York, Buffalo, NY, USA.
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14
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van Grunsven LA, Taelman V, Michiels C, Verstappen G, Souopgui J, Nichane M, Moens E, Opdecamp K, Vanhomwegen J, Kricha S, Huylebroeck D, Bellefroid EJ. XSip1 neuralizing activity involves the co-repressor CtBP and occurs through BMP dependent and independent mechanisms. Dev Biol 2007; 306:34-49. [PMID: 17442301 DOI: 10.1016/j.ydbio.2007.02.045] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2006] [Revised: 02/13/2007] [Accepted: 02/16/2007] [Indexed: 12/31/2022]
Abstract
The DNA-binding transcription factor Smad-interacting protein-1 (Sip1) (also named Zfhx1b/ZEB2) plays essential roles in vertebrate embryogenesis. In Xenopus, XSip1 is essential at the gastrula stage for neural tissue formation, but the precise molecular mechanisms that underlie this process have not been fully identified yet. Here we show that XSip1 functions as a transcriptional repressor during neural induction. We observed that constitutive activation of BMP signaling prevents neural induction by XSip1 but not the inhibition of several epidermal genes. We provide evidence that XSip1 binds directly to the BMP4 proximal promoter and modulates its activity. Finally, by deletion and mutational analysis, we show that XSip1 possesses multiple repression domains and that CtBPs contribute to its repression activity. Consistent with this, interference with XCtBP function reduced XSip1 neuralizing activity. These results suggest that Sip1 acts in neural tissue formation through direct repression of BMP4 but that BMP-independent mechanisms are involved as well. Our data also provide the first demonstration of the importance of CtBP binding in Sip1 transcriptional activity in vivo.
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Affiliation(s)
- Leo A van Grunsven
- Department of Developmental Biology, Flanders Interuniversity Institute for Biotechnology and Laboratory of Molecular Biology, Celgen, Division of Molecular and Developmental Genetics, K.U. Leuven VIB, Leuven, Belgium
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15
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16
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Abstract
Research using Xenopus laevis has made enormous contributions to our understanding of vertebrate development, control of the eukaryotic cell cycle and the cytoskeleton. One limitation, however, has been the lack of systematic genetic studies in Xenopus to complement molecular and cell biological investigations. Work with the closely related diploid frog Xenopus tropicalis is beginning to address this limitation. Here, we review the resources that will make genetic studies using X. tropicalis a reality.
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Affiliation(s)
- Samantha Carruthers
- Vertebrate Development and Genetics, The Morgan Building, Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1HH, UK
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17
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Abstract
Multiphoton laser scanning microscopy (MPLSM) has become an increasingly invaluable tool in fluorescent optical imaging. There are several distinct advantages to implementing MPLSM as a Xenopus oocyte research tool. MPLSM increases signal-to-noise ratio and therefore increases image quality because there is no out-of-focus fluorescence as would be created in conventional or confocal microscopy. All the light that is generated can be collected and used to generate an image because point detection of descanned fluorescence is not required. This is particularly useful when imaging deep into tissue sections, as is necessary for Xenopus oocytes, which are notoriously large (approximately 1-mm diameter). Because multiphoton lasers use pulsed energy in the infrared wavelengths, the energy can also travel further into tissues with much less light scattering. Because there is no out-of-focus excitation, phototoxicity, photodamage, and photobleaching are significantly reduced, which is particularly important for long-term experiments that require the same region to be scanned repeatedly. Finally, multiple fluorophores can be simultaneously excited because of the broader absorption spectra of multiphoton dyes. In this chapter, we describe the advantages and disadvantages of using MPLSM to image Xenopus oocytes as compared to conventional and confocal microscopy. The practical application of imaging oocytes is demonstrated with specific examples.
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Affiliation(s)
- Angela M Prouty
- Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, USA
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18
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Abstract
The rate of somatic development of anuran amphibians is only roughly correlated with the rate of gonad differentiation and varies among species. The somatic stage of a tadpole often does not reflect its age, which seems to be crucial for gonad differentiation rate. We compared the morphology and differentiation of developing ovaries at the light and electron microscopy level, with reference to somatic growth and age of a female. Our observations were performed on 12 species of six families (Rana lessonae, R. ridibunda, R. temporaria, R. arvalis, R. pipiens, R. catesbeiana, Bombina bombina, Hyla arborea, Bufo bufo. B. viridis, Xenopus laevis, Pelobates fuscus) and compared with the results obtained by other authors. This allowed us to describe the unified pattern of anuran female gonad differentiation. Ovary differentiation was divided into 10 stages: I-III, undifferentiated gonad; IV, sexual differentiation; V, first nests of meiocytes; VI, first diplotene oocytes; VII-IX, increasing number of diplotene oocytes and decreasing number of oogonia and nests; X, fully developed ovary composed of diplotene oocytes with rudimental patches of oogonia. We distinguished three types of ovary differentiation rate: basic (most species), retarded (genus Bufo), and accelerated (green frogs of the subgenus Pelophylax genus Rana).
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Affiliation(s)
- Maria Ogielska
- Laboratory of Evolutionary and Developmental Biology of Vertebrates, Zoological Institute, Wroclaw University, 50-335 Wrocław, Poland.
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19
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Shook DR, Majer C, Keller R. Pattern and morphogenesis of presumptive superficial mesoderm in two closely related species, Xenopus laevis and Xenopus tropicalis. Dev Biol 2004; 270:163-85. [PMID: 15136148 DOI: 10.1016/j.ydbio.2004.02.021] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2003] [Revised: 02/20/2004] [Accepted: 02/20/2004] [Indexed: 11/26/2022]
Abstract
The mesoderm, comprising the tissues that come to lie entirely in the deep layer, originates in both the superficial epithelial and the deep mesenchymal layers of the early amphibian embryo. Here, we characterize the mechanisms by which the superficial component of the presumptive mesoderm ingresses into the underlying deep mesenchymal layer in Xenopus tropicalis and extend our previous findings for Xenopus laevis. Fate mapping the superficial epithelium of pregastrula stage embryos demonstrates ingression of surface cells into both paraxial and axial mesoderm (including hypochord), in similar patterns and amounts in both species. Superficial presumptive notochord lies medially, flanked by presumptive hypochord and both overlie the deep region of the presumptive notochord. These tissues are flanked laterally by superficial presumptive somitic mesoderm, the anterior tip of which also appears to overlay the presumptive deep notochord. Time-lapse recordings show that presumptive somitic and notochordal cells move out of the roof of the gastrocoel and into the deep region during neurulation, whereas hypochordal cells ingress after neurulation. Scanning electron microscopy at the stage and position where ingression occurs suggests that superficial presumptive somitic cells in X. laevis ingress into the deep region as bottle cells whereas those in X. tropicalis ingress by "relamination" (e.g., [Dev. Biol. 174 (1996) 92]). In both species, the superficially derived presumptive somitic cells come to lie in the medial region of the presumptive somites during neurulation. By the early tailbud stages, these cells lie at the horizontal myoseptum of the somites. The morphogenic pathway of these cells strongly resembles that of the primary slow muscle pioneer cells of the zebrafish. We present a revised fate map of Xenopus, and we discuss the conservation of superficial mesoderm within amphibians and across the chordates and its implications for the role of this tissue in patterning the mesoderm.
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Affiliation(s)
- David R Shook
- Department of Biology, University of Virginia, Gilmer Hall, Charlottesville, VA 22903, USA.
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20
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Abstract
The development of the first form of kidney, the pronephros, in the frog Xenopus is most attractive to study nephrogenesis in vertebrates. The formation of the pronephros can be readily analyzed during organogenesis by manipulating the activity of specific factors in the developing Xenopus embryo. In addition embryonic explants of Xenopus can be induced to pronephric differentiation in vitro by adding defined signaling molecules. The available data show that the same transcription factors and signaling molecules play a role in Xenopus pronephros differentiation as in mammalian nephrogenesis. This allows the dissection of the molecular and cellular events relevant for nephrogenesis in an easy amenable experimental system. Thus, Xenopus pronephros formation can be used to define nephrogenic regulators and to identify the morphogenetic potential of mutated factors associated with renal diseases in humans.
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Affiliation(s)
- Gerhart U Ryffel
- Institut für Zellbiologie (Tumorforschung), Universitätsklinikum Essen, Essen, Germany.
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21
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Gormley JP, Nascone-Yoder NM. Left and right contributions to the Xenopus heart: implications for asymmetric morphogenesis. Dev Genes Evol 2003; 213:390-8. [PMID: 12764614 DOI: 10.1007/s00427-003-0337-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2003] [Accepted: 04/09/2003] [Indexed: 11/24/2022]
Abstract
The left-right asymmetry of the vertebrate heart is evident in the topology of the heart loop, and in the dissimilar morphology of the left and right chambers. How left-right asymmetric gene expression patterns influence the development of these features is not understood, since the individual roles of the left and right sides of the embryo in heart looping or chamber morphogenesis have not been specifically defined. To this end, we have constructed a bilateral heart-specific fate map of the left and right contributions to the developing heart in the Xenopus embryo. Both the left and right sides contribute to the conoventricular segment of the heart loop; however, the left side contributes to the inner curvature and ventral face of the loop while the right side contributes to the outer curvature and dorsal aspect. In contrast, the left atrium is derived mainly from the original left side of the embryo, while the right atrium is derived primarily from the right side. A comparison of our fate map with the domain of expression of the left-right gene, Pitx2, in the left lateral plate mesoderm, reveals that this Pitx2-expressing region is fated to form the inner curvature of the heart loop, the left atrioventricular canal, and the dorsal aspect of the left atrium. We discuss the implications of these results for the role of left-right asymmetric gene expression in heart looping and chamber morphogenesis.
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Affiliation(s)
- Joseph P Gormley
- Department of Biology, Collegium of Natural Sciences, Eckerd College, 4200 54th Avenue South, St. Petersburg, FL 33711, USA
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22
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Schwerte T, Fritsche R. Understanding cardiovascular physiology in zebrafish and Xenopus larvae: the use of microtechniques. Comp Biochem Physiol A Mol Integr Physiol 2003; 135:131-45. [PMID: 12727550 DOI: 10.1016/s1095-6433(03)00044-8] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Zebrafish and Xenopus, genetically accessible vertebrates with an externally developing, optically clear embryo, are ideally suited for in vivo functional dissection of the embryonic development of the circulatory system. Physiological characterizations of the cardiovascular system are still imperative for a more complete understanding of the connections between genetic/epigenetic factors and cardiovascular development. Here, we review experimental tools and methods that have been developed to measure numerous cardiovascular parameters in these millimetre-sized animals.
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Affiliation(s)
- Thorsten Schwerte
- University of Innsbruck, Institute for Zoology and Limnology, Techniker Str. 25, A-6020 Innsbruck, Austria.
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23
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Grant S, Waller W, Bhalla A, Kennard C. Normal chiasmatic routing of uncrossed projections from the ventrotemporal retina in albino Xenopus frogs. J Comp Neurol 2003; 458:425-39. [PMID: 12619076 DOI: 10.1002/cne.10598] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Albino mammals lacking melanin in the embryonic retinal pigment epithelium (RPE) have abnormal retinal decussation patterns at the optic chiasm: their uncrossed projections are smaller and arise from fewer, more peripheral temporal retinal ganglion cells than in con-specific wild-types. To determine whether these abnormalities generalize to nonmammalian mutants, we used anterograde and retrograde labeling methods to compare the distribution of retinal projections to the thalamus in adult normal and albino Xenopus frogs. In both pigmentation phenotypes, crossed retinal terminations covered approximately 80% of the neuropil of Bellonci (nB) and corpus geniculatum thalamicum (cgt) and uncrossed inputs occupied, respectively, approximately 75% and 25% of these two main visual centers. In the wild-type frogs and in the albinos, ganglion cells giving rise to the crossed projections were distributed throughout the retina, whereas ipsilaterally projecting cells were confined to a specific ventrotemporal retinal division. This region comprised approximately 40% of the total retinal area, was bordered by a well-defined line of decussation, and contained an average of approximately 3,000 ipsilaterally projecting ganglion cells of equivalent soma sizes in the two pigmentation phenotypes. In summary, we found no evidence of chiasmatic misrouting in the uncrossed retinothalamic projections of albino Xenopus, even though these pathways are substantial in normal frogs and share features in common with mammalian retinogeniculate projections. Our findings suggest that congenital RPE melanin deficiency results in major defects in the development of the retina and its central projections only in mammals.
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Affiliation(s)
- Simon Grant
- Department of Optometry and Visual Science, City University, NorthamptonSquare, London EC1V 0HB, United Kingdom.
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24
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Perron M, Boy S, Amato MA, Viczian A, Koebernick K, Pieler T, Harris WA. A novel function for Hedgehog signalling in retinal pigment epithelium differentiation. Development 2003; 130:1565-77. [PMID: 12620982 DOI: 10.1242/dev.00391] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Sonic hedgehog is involved in eye field separation along the proximodistal axis. We show that Hh signalling continues to be important in defining aspects of the proximodistal axis as the optic vesicle and optic cup mature. We show that two other Hedgehog proteins, Banded hedgehog and Cephalic hedgehog, related to the mouse Indian hedgehog and Desert hedgehog, respectively, are strongly expressed in the central retinal pigment epithelium but excluded from the peripheral pigment epithelium surrounding the ciliary marginal zone. By contrast, downstream components of the Hedgehog signalling pathway, Gli2, Gli3 and X-Smoothened, are expressed in this narrow peripheral epithelium. We show that this zone contains cells that are in the proliferative state. This equivalent region in the adult mammalian eye, the pigmented ciliary epithelium, has been identified as a zone in which retinal stem cells reside. These data, combined with double labelling and the use of other retinal pigment epithelium markers, show that the retinal pigment epithelium of tadpole embryos has a molecularly distinct peripheral to central axis. In addition, Gli2, Gli3 and X-Smoothened are also expressed in the neural retina, in the most peripheral region of the ciliary marginal zone, where retinal stem cells are found in Xenopus, suggesting that they are good markers for retinal stem cells. To test the role of the Hedgehog pathway at different stages of retinogenesis, we activated the pathway by injecting a dominant-negative form of PKA or blocking it by treating embryos with cyclopamine. Embryos injected or treated at early stages display clear proximodistal defects in the retina. Interestingly, the main phenotype of embryos treated with cyclopamine at late stages is a severe defect in RPE differentiation. This study thus provides new insights into the role of Hedgehog signalling in the formation of the proximodistal axis of the eye and the differentiation of retinal pigment epithelium.
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Affiliation(s)
- Muriel Perron
- Laboratoire d'Embryologie Moléculaire, Bat. 445 Université Paris XI, 91405 Orsay, France.
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25
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Affiliation(s)
- J Gerhart
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
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26
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Abstract
Amphibia Kupffer cells (i.e., liver resident macrophages) show many common characteristics when compared with Mammalia Kupffer cells: filopodia, microvillous-like structures, lamellipodia, fuzzy coat, coated vesicles, bristled vacuoles, nonspecific esterase activity, and pinocytotic and phagocytic activity are present both in Amphibia and Mammalia Kupffer cells. On the other hand, some differences are present between Kupffer cells of both zoological classes: phagocytosed red cells and their derivatives, iron-protein complexes, and lipofuscin bodies are normally present in Amphibia Kupffer cells, but absent in the same cells of healthy mammals. Worm-like structures are not seen in Amphibia and endogenous peroxidase activity is very weak in these animals compared with Mammalia. The most important difference lies in the ability of Amphibia Kupffer cells to produce melanins: in fact the tyrosinase gene is expressed, "melanosome centers" are present, and dopa oxidase activity is demonstrable.
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Affiliation(s)
- Giovanni Sichel
- Dipartimento di Scienze Biomediche, Sezione di Biologia generale, cellulare e di Genetica molecolare, Università di Catania, Catania, Italy.
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27
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von Strandmann EP, Senkel S, Ryffel G, Hengge UR. Dimerization co-factor of hepatocyte nuclear factor 1/pterin-4alpha-carbinolamine dehydratase is necessary for pigmentation in Xenopus and overexpressed in primary human melanoma lesions. Am J Pathol 2001; 158:2021-9. [PMID: 11395380 PMCID: PMC1891999 DOI: 10.1016/s0002-9440(10)64674-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dimerization co-factor of hepatocyte nuclear factor 1 (HNF1)/pterin-4alpha-carbinolamine dehydratase (DCoH/PCD) is both a positive co-factor of the HNF1 homeobox transcription factors and thus involved in gene regulation as well as an enzyme catalyzing the regeneration of tetrahydrobiopterin. Dysfunction of DCoH/PCD is associated with the human disorders hyperphenylalaninemia and vitiligo. In Xenopus, overexpression of the protein during development induces ectopic pigmentation. In this study loss of function experiments using DCoH/PCD-specific antibodies demonstrated that the protein is also absolutely necessary for pigment cell formation in Xenopus. In normal human skin DCoH/PCD protein is weakly expressed in the basal layer of the epidermis that consists of keratinocytes and melanocytes. Whereas only 4 of 25 benign nevi reacted with DCoH/PCD-specific antibodies, high protein levels were detectable in melanoma cell lines and 13 of 15 primary malignant melanoma lesions. The comparison with the commonly used melanoma markers S100 and HMB45 demonstrated that DCoH/PCD has an overlapping but distinct expression pattern in melanoma lesions. In addition to human colon cancer, this is the second report about the overexpression of DCoH/PCD in human tumor cells indicating that the protein might be involved in cancerogenesis.
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Affiliation(s)
- E P von Strandmann
- Institute of Cell Biology and Department of Dermatology, Venerology, and Allergology, University of Essen, Hufelandstrasse, Essen, Germany
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28
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Wang H, Shi H, Zhang L, Pourrier M, Yang B, Nattel S, Wang Z. Nicotine is a potent blocker of the cardiac A-type K(+) channels. Effects on cloned Kv4.3 channels and native transient outward current. Circulation 2000; 102:1165-71. [PMID: 10973847 DOI: 10.1161/01.cir.102.10.1165] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Nicotine is a main constituent of cigarette smoke and smokeless tobacco, known to increase the risk of sudden cardiac death. This study aimed at establishing ionic mechanisms underlying potential electrophysiological effects of nicotine. METHODS AND RESULTS Effects of nicotine on Kv4.3 and Kv4.2 channels expressed in Xenopus oocytes were studied at the whole-cell and single-channel levels. The effects of nicotine on the transient outward K(+) current (I:(to)) were studied by use of whole-cell patch-clamp techniques in canine ventricular myocytes. Nicotine potently inhibited Kv4 current. The concentration for half-maximal inhibition (IC(50)) was 40+/-4 nmol/L, and the current was abolished by 100 micromol/L nicotine. The IC(50) for block of native I:(to) was 270+/-43 nmol/L. The steady-state activation properties of Kv4.3 and I:(to) were unaltered by nicotine, whereas positive shifts of the inactivation curves were observed. Of the total inhibition of Kv4.3 and I:(to) by nicotine, 40% was due to tonic block and 60% was attributable to use-dependent block. Activation, inactivation, and reactivation kinetics were not significantly changed by nicotine. Nicotine reduced single-channel conductance, open probability, and open time but increased the closed time of Kv4.3. The effects of nicotine were not altered by antagonists to various neurotransmitter receptors, indicating direct effects on I:(to) channels. CONCLUSIONS Nicotine is a potent inhibitor of cardiac A-type K(+) channels, with blockade probably due to block of closed and open channels. This action may contribute to the ability of nicotine to affect cardiac electrophysiology and induce arrhythmias.
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Affiliation(s)
- H Wang
- Department of Medicine and Research Center, Montreal Heart Institute, University of Montreal, Quebec, Canada.
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29
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Affiliation(s)
- S A Moody
- Department of Anatomy and Cell Biology, George Washington University Medical Center, Washington, DC, USA
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30
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Affiliation(s)
- C A Larabell
- Life Sciences Division, Lawrence Berkeley National Laboratory, University of California, USA
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31
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Abstract
Survival of vertebrate embryos depends on their ability to assemble a correctly patterned, integrated network of blood vessels to supply oxygen and nutrients to developing tissues. The arrangement of larger caliber intraembryonic vessels, specification of arterial-venous identity, and proper placement of major branch points and arterial-venous connections are all precisely determined. A number of recent studies in both mammalian and nonmammalian vertebrate species, reviewed here, have now begun to reveal the major role played by genetically predetermined extrinsic cues in guiding the formation of early embryonic blood vessels and determining the global pattern of the vasculature.
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Affiliation(s)
- B M Weinstein
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA
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32
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Abstract
Contrary to traditional views, molecular evidence indicates that the protostomian ventral nerve cord plus apical brain is homologous with the vertebrates' dorsal spinal cord plus brain. The origin of the protostomian central nervous system from a larval apical organ plus longitudinal areas along the fused blastopore lips has been documented in many species. The origin of the chordate central nervous system is more enigmatic. About a century ago, Garstang proposed that the ciliary band of a dipleurula-type larva resembling an echinoderm larva should have moved dorsally and fused to form the neural tube of the ancestral chordate. This idea is in contrast to a number of morphological observations, and it is here proposed that the neural tube evolved through lateral fusion of a ventral, postoral loop of the ciliary band in a dipleurula larva; the stomodaeum should move from the ventral side via the anterior end to the dorsal side, which faces the substratum in cephalo- chordates and vertebrates. This is in accordance with the embryological observations and with the molecular data on the dorsoventral orientation. The molecular observations further indicate that the anterior part of the insect brain is homologous with the anterior parts of the vertebrate brain. This leads to the hypothesis that the two organs evolved from the same area in the latest common bilaterian ancestor, just anterior to the blastopore, with the protostome brain developing from the anterior rim of the blastopore (i.e. in front of the protostome mouth) and the chordate brain from an area in front of the blastopore, but behind the mouth (i.e. behind the deuterostome mouth).
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Affiliation(s)
- C Nielsen
- Zoological Museum, Universitetsparken 15, DK-2100 Copenhagen, Denmark
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33
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Abstract
We identified a Xenopus gene closely related to mammalian bone morphogenetic protein (BMP)-7 (also termed osteogenic protein-1 or OP-1). It resembles the mammalian gene in primary structure and expression pattern much more closely than does a previously described Xenopus homologue, originally termed XBMP-7 [Nishimatsu, Suzuki, Shoda, Murakami and Ueno (1992) Biochem. Biophys. Res. Commun. 186, 1487-1495]. The novel gene has therefore been designated XBMP-7 and the gene described earlier has been renamed XBMP-7R (M. Moos and N. Ueno, unpublished work). It has a broad distribution, primarily in the anterior and posterior ventral regions during gastrulation, subsequently becoming prominent at different stages in a wide variety of structures (eyes, neural structures, heart, pronephros, posterior ventral region and other structures), paralleling the distribution of XBMP-4 closely. However, its expression begins later than that of XBMP-4 during gastrulation. Lithium treatment of embryos concentrates the XBMP-7 expression in the expanded eye and heart structures. Ventral overexpression of XBMP-7 produces large protrusions that ultimately develop colouration characteristic of haemoglobin, which is confirmed by markedly expanded expression of alpha-globin. Dorsal overexpression suppresses dorsal anterior structures. Molecular analysis of animal caps overexpressing XBMP-7 reveals induction of markers associated with ventral and haematopoietic tissue, which is consistent with whole-embryo overexpression results. Globin induction by XBMP-7 can be blocked by a truncated BMP receptor previously shown to interrupt BMP-4 signalling, indicating XBMP-7 also interacts with this receptor. Our data support the concept that XBMP-7 may play a variety of roles during embryogenesis, and suggest a possible role in haematogenesis.
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Affiliation(s)
- S Wang
- Laboratory of Developmental Biology, Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, MD 20852-1448, USA
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34
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Abstract
N-acetyl cysteine is an agent which has been shown to interrupt signal transduction processes linking a wide range of stimuli to the activation of NF-kappa B in mammalian cells. We have investigated its effect on the early development of Xenopus embryos by injecting it into blastulae, using concentrations comparable to those effective on cultured cells. High concentrations at the late blastula or early gastrula stage suppress posterior and enhance anterior development, yielding embryos with enlarged cement glands and otherwise consisting of little except head in extreme cases. Reducing the amount of N-acetyl cysteine injected leads to progressively more posterior structures developing. Injection into one- or two-cell embryos gives similar phenotypes, but of reduced severity and the cement gland is not so enlarged. Explants of animal cap cells taken several hours after injection develop to give large amounts of cement gland material. We have examined the expression of a number of genes in the anteriorised embryos. Posterior markers and Xsna are reduced. Noggin and Goosecoid mRNA are up-regulated through the gastrula and persist at these levels until at least the late neurula stage, whereas in controls Noggin is much lower and Goosecoid is absent at these stages. The most anteriorised phenotype may be a consequence of this changed expression.
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Affiliation(s)
- D Gatherer
- Department of Biological Sciences, University of Warwick, Coventry, England
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35
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Affiliation(s)
- C A Larabell
- Lawrence Berkeley National Laboratory, University of California, Berkeley 94720, USA
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36
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Abstract
In Drosophila, the proneural genes of the achaete-scute complex encode transcriptional activators that can commit cells to a neural fate. We have isolated cDNAs for two Xenopus achaete-scute homologs, ASH3a and ASH3b, which are expressed in a subset of central nervous system (CNS) neuroblasts during early neurogenesis. After expressing either ASH3 protein in developing Xenopus embryos, we find enlargement of the CNS at the expense of adjacent non-neural ectoderm. Analysis of molecular markers for neural, epidermal, and neural crest cells indicates that CNS expansion occurs as early as neural plate formation. ASH3-dependent CNS enlargement appears to require neural induction, as it does not occur in animal cap explants. Inhibition of DNA synthesis shows that additional CNS tissue does not depend on cell division--rather it reflects conversion of prospective neural crest and epidermal cells to a neural fate. The differentiation of the early forming primary neurons also seems to be prevented by ASH3 expression. This may be secondary to the observed activation of Xotch transcription by ASH3.
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Affiliation(s)
- D L Turner
- Department of Genetics, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104
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37
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Olivereau M, Olivereau JM. Immunocytochemical localization of a galanin-like peptidergic system in the brain of two urodele and two anuran species (Amphibia). Histochemistry 1992; 98:51-66. [PMID: 1385367 DOI: 10.1007/bf00716937] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Galanin-like immunoreactivity was localized in the brain of Urodela (Ambystoma, Pleurodeles) and Anura (Bufo, Xenopus) by immunocytochemistry with anti-porcine galanin antiserum. In the four species, immunoreactive perikarya were observed in the telencephalon (striatum, amygdala), diencephalon preoptic area mainly along the anterodorsal wall of the preoptic recessus, suprachiasmatic nucleus, lateral hypothalamus, ventral and dorsal infundibular nuclei, paraventricular organ, and rhombencephalon (nucleus of the solitary tract). Galaninergic fibres extended in similar regions and in the medial septum, ventral telencephalon, ventral hypothalamus, median eminence, and various mesencephalic and rhombencephalic regions. Contacts with the cerebrospinal fluid cavity occurred along the preoptic recessus (Ambystoma) and the ventral infundibular wall (all species). Fibres were scarce in the neurohypophysis. The distal and intermediate lobes of the pituitary were virtually devoid of immunoreactivity. The galaninergic system appeared more developed in adult amphibia than in young animals, suggesting the stimulating influence of sex steroids on the expression of galanin as previously described in Anguilla. The extensive distribution of the galanin-like immunoreactive neurons in amphibian brains suggests that this peptide may act as a neuromodulatur and/or neurotransmitter.
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Affiliation(s)
- M Olivereau
- Laboratorie de Physiologie, Institut Océanographique, Paris, France
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38
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Wolburg H, Berg-von der Emde K, Naujoks-Manteuffel C. Müller (glial) cells in the retina of urodeles and anurans reveal different morphology by means of freeze-fracturing. Neurosci Lett 1992; 138:89-92. [PMID: 1407671 DOI: 10.1016/0304-3940(92)90479-q] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Müller (glial) cells of the retina of various species of amphibia (urodeles and anurans) were investigated by means of the freeze-fracture technique. This was done because Müller cells in anamniotes were believed to differ from those in mammals in that they should lack the so-called orthogonal arrays of particles (OAP) which are a characteristic feature of Müller cells in mammalian retina. However, as we could demonstrate previously (Berg-von der Emde and Wolburg, Glia, 2 (1989) 458), fish retinal Müller cells also contain OAP in their membranes suggesting that OAP are a general marker of Müller cells in all vertebrates. As demonstrated in this study, Müller cells of urodeles (Batrachoseps attenuatus and Pleurodeles waltlii) are OAP-positive, whereas two anurans (Rana esculenta and Xenopus laevis) do not reveal any OAP in their Müller cell membranes. Under phylogenetic aspects, it appears very interesting that frogs are as yet the only vertebrate group that deviates from all other vertebrates in terms of Müller cell membrane morphology.
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Affiliation(s)
- H Wolburg
- Institute of Pathology, University of Tübingen, FRG
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39
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van Strien FJ, de Rijk EP, Heymen PS, Hafmans TG, Roubos EW. Demonstration of dopamine in electron-dense synaptic vesicles in the pars intermedia of Xenopus laevis, by freeze substitution and postembedding immunogold electron microscopy. Histochemistry 1991; 96:505-10. [PMID: 1769861 DOI: 10.1007/bf00267076] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The presence of dopamine in the pituitary of the clawed toad Xenopus laevis was studied by light and electron microscope immunocytochemistry, using pre- and postembedding techniques. Light microscopy showed the presence of an intricate, anti-dopamine-positive fibre network throughout the pars intermedia. In preembedded stained material, dopamine appeared to occur in varicosities which make synaptic contacts with both folliculo-stellate cells and melanotrope cells. Post-embedding immunogold staining of freeze-substituted material permitted the localization of anti-dopamine reactivity in electron-dense vesicles in these varicosities. This finding supports the hypothesis that dopamine is involved in the (inhibitory) control of melanotrope cell activity in X. laevis.
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Affiliation(s)
- F J van Strien
- Department of Animal Physiology, Faculty of Science, University of Nijmegen, The Netherlands
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40
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Akey CW. Probing the structure and function of the nuclear pore complex. Semin Cell Biol 1991; 2:167-77. [PMID: 1720335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Nucleocytoplasmic transport is a bi-directional process mediated by the nuclear pore complex (NPC), which results in a segregation of cytoplasmic and nuclear macromolecules within cells. Some progress has been made in understanding the mechanistic basis of this selective transport phenomenon. In particular, cryo-electron microscopy of frozen-hydrated nuclear envelopes coupled with image processing and labeling studies, has provided a glimpse of the transporter at the center of the NPC.
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Affiliation(s)
- C W Akey
- Department of Biophysics, Boston University School of Medicine, MA 02118-2394
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41
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Goodbrand IA, Gaze RM. Microglia in tadpoles of Xenopus laevis: normal distribution and the response to optic nerve injury. Anat Embryol (Berl) 1991; 184:71-82. [PMID: 1928746 DOI: 10.1007/bf01744263] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We have studied the distribution of microglia in normal Xenopus tadpoles and after an optic nerve lesion, using a monoclonal antibody (5F4) raised against Xenopus retinas of which the optic nerves had been cut 10 days previously. The antibody 5F4 selectively recognizes macrophages and microglia in Xenopus. In normal animals microglia are sparsely but widely distributed throughout the retina, optic nerve, diencephalon and mesencephalon (other regions were not examined). After crush or cut of an optic nerve, or eye removal, there occurs an extensive microglial response along the affected optic pathway. Within 18 h an increase in the number of microglial cells in the optic tract and tectum can be detected. This response increases to peak at around 5 days after the lesion. At this time the nerve distal to the lesion contains many microglial cells; the entire optic tract is outlined by microglia, extended along the degenerating fibres; and the affected tectum shows a heavy concentration of microglia. This microglial response thereafter decreases and has mostly gone by 34 days. We conclude that the microglial response to optic nerve injury in Xenopus tadpoles starts early, peaks just before the regenerating optic nerve axons enter the brain, and is much diminished by the time the retinotectal projection is re-established. The timing is such that the microglial response could play a major role in facilitating regeneration.
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Affiliation(s)
- I A Goodbrand
- MRC Neural Development and Regeneration Group, Department of Zoology, University of Edinburgh, UK
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42
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Affiliation(s)
- M W Klymkowsky
- Molecular, Cellular and Developmental Biology, University of Colorado, Boulder 80309-0347
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43
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Abstract
Relationships of the pipid frog genus Silurana (= Xenopus tropicalis group of some authors) are of particular interest to developmental and molecular biologists because of the purported ancestral (i.e., unduplicated) karyotype of S. tropicalis relative to the genus Xenopus. Although most previous studies have assumed that Silurana is the sister group of Xenopus, recent morphological work suggests that Silurana is more closely related both to the South American genus Pipa and to the African genera Hymenochirus and Pseudhymenochirus than it is to Xenopus. We examined 1,486 bp of relatively variable regions of the ribosomal DNA array (including portions of the 18S and 28S genes, as well as part of an internal transcribed spacer) in Hymenochirus, Silurana, and Xenopus, as well as the outgroup genus Spea, in order to test the alternative hypotheses of relationships for Silurana. Maximum-parsimony analysis using bootstrapping and an analysis using Lake's method of invariants both significantly support the sister-group relationship between Xenopus and Silurana rather than the relationship suggested by morphology. Analysis of the combined morphological/molecular data matrix also significantly supports the Xenopus-Silurana relationship. Although our results are not inconsistent with the recognition of the genus Silurana to accommodate the species formerly called X. tropicalis and X. epitropicalis, the proposed relationships do not require the recognition of this genus in order to render Xenopus monophyletic.
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Affiliation(s)
- R O de Sá
- Department of Zoology, University of Texas, Austin 78712-1064
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Zhu BS, Hiscock J, Straznicky C. The changing distribution of neurons in the inner nuclear layer from metamorphosis to adult: a morphometric analysis of the anuran retina. Anat Embryol (Berl) 1990; 181:585-94. [PMID: 2118741 DOI: 10.1007/bf00174630] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The generation and changing distribution of neurons of the inner nuclear layer (INL) in the retina of two anuran species, Bufo marinus and Xenopus laevis, were studied from metamorphosis to adult. Morphometric studies were undertaken at six developmental stages in Bufo and four in Xenopus. The number and thickness of neurons in the INL were established in 29 predetermined retinal locations from serial sections of the eyes cut vertically or horizontally. The total number of neurons in the INL increased from metamorphosis to adult from 826,000 +/- 185 to 18,760,000 +/- 562 (mean +/- SD) in Bufo and from 308,000 +/- 25 to 877,000 +/- 31 in Xenopus. Over the same period the surface area of the INL increased about 50-fold from 2 mm2 to 96 mm2 in Bufo and 5-fold from 2.5 mm2 to 13 mm2 in Xenopus. In Bufo the difference between the highest cell number (central-temporal retina) and the lowest cell number in a sample area (dorsal and ventral peripheral retina) was 2.1:1 at metamorphosis. This ratio increased to 3.4:1 in the adult. Both the cell number and cell density per sample area in the INL was found to be higher along the nasotemporal meridian of the eye overlying the visual streak of the ganglion cell layer (GCL) of the retina. The retinal distribution of neurons in the INL did not change significantly during postmetamorphic growth in Xenopus. At metamorphosis a 1.7:1 difference was found between the highest neuron number (retinal ciliary margin) and lowest neuron number (retinal centre) decreasing to 1.5:1 in the adult. Retinae were labelled with 3H-thymidine in 15 mm Bufos and examined 2, 6, 12 and 18 weeks later. Higher rates of cell addition to the nasal and temporal poles of the INL were found compared with that at the dorsal and ventral poles. The retinal radial growth at the ciliary margin of the dorsal, ventral, nasal and temporal poles between the time of isotope injection and 18 weeks survival was found to be uneven; more radial elongation occurred at the nasal, dorsal and ventral poles and less at the temporal pole. These observations suggest that (a) the neuron distribution of the INL in adult animals approximates that of the GCL and (b) the visual streak-like area of the INL in Bufo develops by a sustained differential cell addition at the temporal and nasal poles of the retina.
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Affiliation(s)
- B S Zhu
- Department of Anatomy and Histology, School of Medicine, University of South Australia, Bedford Park
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45
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Abstract
A method for the isolation of plasma membrane fractions from Xenopus oocytes has been developed, and the membranes have been characterized biochemically and morphologically. Plasma membrane complexes prepared by this procedure consisted of large sheets of the membrane, with associated vitelline envelope (a nonmembranous meshwork of fibers) and cortical (secretory) granules still attached. The morphology of cell surface microvilli and coated pits was well preserved. Cortical granules were removed by gentle homogenization in a low ionic strength medium, and integral and peripheral membrane proteins were then separated from vitelline envelopes by detergent extraction and phase separation in Triton-X-114. Biochemical characterization of the plasma membrane fractions indicated substantial levels of 5'-nucleotidase and alkaline phosphodiesterase activity associated with the oocyte cell surface, with 44-66% recovery of these markers in the final membrane preparations. Lectin blotting and lectin affinity chromatography with Concanavalin A and wheat germ agglutinin were used to characterize the major glycoprotein species associated with the plasma membrane complexes. Plasma membrane fractions prepared by this procedure should be very useful in both biochemical and morphological studies of membrane protein sorting in the Xenopus oocyte system.
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Affiliation(s)
- D A Wall
- Department of Cell Biology and Anatomy, Cornell University Medical College, New York, New York 10021
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46
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Abstract
Axon-bearing horizontal cells of the Xenopus retina were studied by intracellular injection of HRP following physiological characterization. The profile of the cell viewed in whole mount consisted of a round or oval perikaryon about 50 microns in diameter and an axon about 1 mm long which lacked a prominent terminal expansion. The axonal diameter was 0.5-1.0 microns in its proximal third but 2-4 microns in its distal portion. Along its course the axon emitted 25-40 branchlets each 0.2 micron in diameter, up to 10 micron long and terminating in a cluster of two to six synaptic knobs. Electron microscopic examination revealed that both perikaryal dendrites and axon branchlets ended in both rod and cone synaptic bases; cone contacts outnumbered rod contacts by two- to threefold. We were unable to document synapses of presumed interplexiform cells onto identified horizontal cells. Horizontal cell axons are joined in their distal portions by numerous, small (0.2 micron long) gap junctions. Other gap junctions were noted between horizontal cell processes within the synaptic endings of photoreceptors. An hypothesis is advanced whereby the cluster of axon branchlet synaptic knobs permits dynamic interaction of rod and cone synaptic inputs to the horizontal cell.
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Affiliation(s)
- P Witkovsky
- Daniel B. Kirby Eye Institute, Department of Ophthalmology, New York, New York
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47
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Fox H. Riesenzellen, goblet cells, Leydig cells and the large clear cells of Xenopus, in the amphibian larval epidermis: fine structure and a consideration of their homology. J Submicrosc Cytol Pathol 1988; 20:437-51. [PMID: 3135114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The origin, fate and fine structure of the epidermal Riesenzellen of larvae of Bufo bufo, have been described by electronmicroscopy throughout their ontogeny. Riesenzellen are uncommon in the epidermis relative to the epithelial cells. In young larvae they differentiate from basal epithelial cells, which enlarge and become rounded, lucent and glandular, some at least to open at the epidermal surface. They have disappeared by the end of metamorphosis. Among amphibian larval specialized cells of the skin, the Riesenzellen so far are known to occur only in bufonid larvae. They differ in fine structure from goblet cells but show greater similarity with them than with other specialized epidermal cells. Riesenzellen are not homologous with Leydig cells of larval urodeles and Ichthyophis among the Gymnophiona. True Leydig cells are not represented by the Riesenzellen or Kugelzellen or other large cells, for example the so-called unicellular gland of Xenopus, in the larval anuran epidermis. Leydig cells do not occur in this group, a fact that could well be of significance in any assessment of amphibian phylogeny.
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Affiliation(s)
- H Fox
- Department of Biology, University College, London, U.K
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48
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Abstract
Using a variety of neuroanatomical and histological techniques, we compare the spinal cord and peripheral nerve distribution in the tails of larvae from Xenopus laevis and three species of Rana. The relatively large, postsacral spinal cord of Xenopus contains abundant motoneurons and their axons. Spinal nerves exit from the spinal cord in a regular array, one nerve per myotome, from the cervical region to near the end of the tail. Somata of motoneurons innervating caudal myotomes are found along the entire length of the tail. In contrast, the caudal cord of Rana is reduced to a filum terminale consisting of little more than an ependymal tube; spinal nerves to all caudal myotomes leave the cord in the sacral region and reach their motor targets via a cauda equina and caudal plexus. Motoneuron cell bodies innervating caudal myotomes are found only in the sacral region. The Rana larval pattern is similar to that of adult frogs and mammals, whereas the Xenopus larval pattern is more like that of salamanders and reptiles. These gross neuroanatomical differences are not due to differences in the size or developmental stage of the tadpoles, but instead are associated with differences in the swimming behavior of the larvae. The presence of motoneurons in the caudal spinal cord of Xenopus may provide local intermyotomal control within the tail; the elongated topography of the cord appears to permit finer, rostral-to-caudal regulation of neuromuscular activity. The Rana spinal cord, on the other hand--with motoneurons clustered anteriorly--may produce concurrent firing of adjacent ipsilateral myotomes, but at the expense of fine intermyotomal regulation. The fact that nerves in the tail of Xenopus enter and exit from the spinal cord locally, as opposed to far anteriorly as in Rana, means that for tadpoles of the same size, reflex arc lengths are many times shorter in Xenopus.
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Affiliation(s)
- K Nishikawa
- Museum of Vertebrate Zoology, University of California, Berkeley 94720
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49
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Abstract
Dorsal roots are absent from the tails of Xenopus larvae. Sensory afferents instead enter the spinal cord via the ventral roots. After reaching the cord these axons travel diagonally within the lateral fasciculus of the cord to reach the dorsolateral fiber bundle in which they ascend to the hindbrain. Sensory afferents entering together in the same ventral root make this traverse individually rather than as a group, but coalesce again at the ascending tract.
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Affiliation(s)
- R H Nordlander
- Department of Oral Biology, Case Western Reserve University, Cleveland, OH 44106
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50
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Fritzsch B, Sonntag R. The trochlear nerve of amphibians and its relation to proprioceptive fibers: a qualitative and quantitative HRP study. Anat Embryol (Berl) 1987; 177:105-14. [PMID: 3434841 DOI: 10.1007/bf00572534] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The cells of origin of the trochlear nerve of urodeles, anurans and gymnophionans were labelled with HRP in order to compare the location and morphology of trochlear motoneurons and to find evidence for sensory fibers in the trochlear nerve of amphibians. Trochlear motoneuron perikarya were found in a ventral tegmental position predominantly on the contralateral side, but an ipsilateral cell was present in some specimens of urodeles and anurans. About 19 motoneurons were labelled in Ambystoma, about 60 motoneurons in Xenopus, and a maximum of 7 cells in Ichthyophis. Decussation of trochlear nerve fibers showed only in Xenopus a highly variable pattern. In urodeles, selective filling of the trochlear nerve labelled in addition to trochlear motoneurons a caudo-medical tectal group of about 20 neurons of the nucleus of the mesencephalic root of the trigeminal nerve. Gymnophionans showed also labelled cells of the mesencephalic trigeminal root in the caudal midbrain close to the trochlear nerve root. In some frogs, a few cells of the mesencephalic trigeminal root were labelled in the caudal tectum and occasionally in the velum medullare anterius. Comparison of the numbers of trochlear nerve fibers with HRP-labelled motoneurons revealed in Xenopus a proportion of 1.2:1, but of 2.7:1 in Ambystoma. However, counting both labelled motoneurons and cells of the mesencephalic trigeminal root resulted in a trochlear nerve fiber to labelled neuron proportion of 1.3:1 in Ambystoma much like in Xenopus. The numbers of superior oblique muscle fibers and of trochlear nerve fibers, but not of HRP-labelled motoneurons, increased significantly with size in Xenopus laevis. We suggest that increased peripheral branching of individual fibers within the trochlear nerve with size rather than differentiation of additional motoneurons takes place in growing postmetamorphic Xenopus. In contrast to other vertebrates studied so far, the trochlear nerve is a mixed nerve in Ambystoma and perhaps in Ichthyophis. Whether this reflects a primitive or a derived condition is at present unclear.
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Affiliation(s)
- B Fritzsch
- University of Bielefeld, Faculty of Biology, Federal Republic of Germany
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