In Situ Hybridization to Identify Stem Cells in the Freshwater Sponge Ephydatia fluviatilis

Sponges (Porifera) are a large phylum that includes an enormous number of species. They are classified into four classes. Among these four classes, class Demospongiae is the largest and contains more than 90% of sponge species. In the last decade, methodologies for molecular studies and sequencing resources in sponge biology have dramatically advanced and made it possible to clearly define particular types of cells based on the genes they are expressing. Here we describe in detail the method of high-resolution WISH (whole mount in situ hybridization) and dual color fluorescent detection of in situ hybridization (dual color FISH) that we have established to detect particular types of cells, especially their stem cells known as archeocytes, in juveniles of freshwater demosponge, E. fluviatilis.

Skeleton construction upon local regression of the sponge body

We previously revealed that the mechanism of demosponge skeleton construction is self-organization by multiple rounds of sequential mechanical reactions of player cells. In these reactions, "transport cells" dynamically carry fine skeletal elements (spicules) on epithelia surrounding the inner body space of sponges (basal epithelium (basopinacoderm) and the endodermal epithelium (ENCM)). Once spicules pierce ENCM and apical pinacoderm, subsequently they are cemented to the substratum under the sponge body, or connected to other skeleton-constructing spicules. Thus, the "pierce" step is the key to holding up spicules in the temporary periphery of growing sponges' bodies. Since sponges can regress as well as grow, here we asked how skeleton construction occurs during local regression of the body. We found that prior to local basopinacoderm retraction (and thus body regression), the body became thinner. Some spicules that were originally carried outward stagnated for a while, and were then carried inwards either on ENCM or basopinacoderm. Spicules that were carried inwards on ENCM pierced epithelia after a short transport, and thus became held up at relatively inward positions compared to spicules carried on outwardly extending basopinacoderm. The switch of epithelia on which transport cells migrate efficiently occurred in thinner body spaces where basopinacoderm and ENCM became close to each other. Thus, the mechanisms underlying this phenomenon are rather mechanical: the combination of sequential reactions of skeleton construction and the narrowed body space upon local retraction of basopinacoderm cause spicules to be held up at more-inward positions, which might strengthen the basopinacoderm's attachment to substratum.

Produce, carry/position, and connect: morphogenesis using rigid materials

Animal morphogenesis can be summarized as a reconfiguration of a mass of cells. Although extracellular matrices that include rigid skeletal elements, such as cartilage/bones and exoskeletons, have important roles in morphogenesis, they are also secreted in situ by accumulated cells or epithelial cells. In contrast, recent studies of the skeleton construction of sponges (Porifera) illuminate a conceptually different mechanism of morphogenesis in which cells manipulate rather fine rigid materials (spicules) to form larger structures. Here, two different types of sponge skeleton formation using calcareous spicules or siliceous spicules are compared with regard to the concept of the production of rigid materials and their use in skeletons. The comparison highlights the advantages of their different strategies of forming sponge skeletons.

Methods for Staging Pupal Periods and Measurement of Wing Pigmentation of Drosophila guttifera

Diversified species of Drosophila (fruit fly) provide opportunities to study mechanisms of development and genetic changes responsible for evolutionary changes. In particular, the adult stage is a rich source of morphological traits for interspecific comparison, including wing pigmentation comparison. To study developmental differences among species, detailed observation and appropriate staging are required for precise comparison. Here we describe protocols for staging of pupal periods and quantification of wing pigmentation in a polka-dotted fruit fly, Drosophila guttifera. First, we describe the method for detailed morphological observation and definition of pupal stages based on morphologies. This method includes a technique for removing the puparium, which is the outer chitinous case of the pupa, to enable detailed observation of pupal morphologies. Second, we describe the method for measuring the duration of defined pupal stages. Finally, we describe the method for quantification of wing pigmentation based on image analysis using digital images and ImageJ software. With these methods, we can establish a solid basis for comparing developmental processes of adult traits during pupal stages.

Pupal development and pigmentation process of a polka-dotted fruit fly, Drosophila guttifera (Insecta, Diptera)

Various organisms have color patterns on their body surfaces, and these color patterns are thought to contribute to physiological regulation, communication with conspecifics, and signaling with the environment. An adult fly of Drosophila guttifera (Insecta: Diptera: Drosophilidae) has melanin pigmentation patterns on its body and wings. Though D. guttifera has been used for research into color pattern formation, how its pupal development proceeds and when the pigmentation starts have not been well studied. In this study, we defined the pupal stages of D. guttifera and measured the pigment content of wing spots from the pupal period to the period after eclosion. Using a transgenic line which carries eGFP connected with an enhancer of yellow, a gene necessary for melanin synthesis, we analyzed the timing at which the yellow enhancer starts to drive eGFP. We also analyzed the distribution of Yellow-producing cells, as indicated by the expression of eGFP during pupal and young adult periods. The results suggested that Yellow-producing cells were removed from wings within 3 h after eclosion, and wing pigmentation continued without epithelial cells. Furthermore, the results of vein cutting experiments showed that the transport of melanin precursors through veins was necessary for wing pigmentation. These results showed the importance of melanin precursors transported through veins and of extracellular factors which were secreted from epithelial cells and left in the cuticle.

Conserved expression of vertebrate microvillar gene homologs in choanocytes of freshwater sponges

BACKGROUND

The microvillus is a versatile organelle that serves important functions in disparate animal cell types. However, from a molecular perspective, the microvillus has been well studied in only a few, predominantly vertebrate, contexts. Little is known about how differences in microvillar structure contribute to differences in function, and how these differences evolved. We sequenced the transcriptome of the freshwater sponge, Ephydatia muelleri, and examined the expression of vertebrate microvillar gene homologs in choanocytes-the only microvilli-bearing cell type present in sponges. Sponges offer a distant phylogenetic comparison with vertebrates, and choanocytes are central to discussions about early animal evolution due to their similarity with choanoflagellates, the single-celled sister lineage of modern animals.

RESULTS

We found that, from a genomic perspective, sponges have conserved homologs of most vertebrate microvillar genes, most of which are expressed in choanocytes, and many of which exhibit choanocyte-specific or choanocyte-enriched expression. Possible exceptions include the cadherins that form intermicrovillar links in the enterocyte brush border and hair cell stereocilia of vertebrates and cnidarians. No obvious orthologs of these proteins were detected in sponges, but at least four candidate cadherins were identified as choanocyte-enriched and might serve this function. In contrast to the evidence for conserved microvillar structure in sponges and vertebrates, we found that choanoflagellates and ctenophores lack homologs of many fundamental microvillar genes, suggesting that microvillar structure may diverge significantly in these lineages, warranting further study.

CONCLUSIONS

The available evidence suggests that microvilli evolved early in the prehistory of modern animals and have been repurposed to serve myriad functions in different cellular contexts. Detailed understanding of the sequence by which different microvilli-bearing cell/tissue types diversified will require further study of microvillar composition and development in disparate cell types and lineages. Of particular interest are the microvilli of choanoflagellates, ctenophores, and sponges, which collectively bracket the earliest events in animal evolution.

How do environmental factors influence life cycles and development? An experimental framework for early-diverging metazoans

Ecological developmental biology (eco-devo) explores the mechanistic relationships between the processes of individual development and environmental factors. Recent studies imply that some of these relationships have deep evolutionary origins, and may even pre-date the divergences of the simplest extant animals, including cnidarians and sponges. Development of these early diverging metazoans is often sensitive to environmental factors, and these interactions occur in the context of conserved signaling pathways and mechanisms of tissue homeostasis whose detailed molecular logic remain elusive. Efficient methods for transgenesis in cnidarians together with the ease of experimental manipulation in cnidarians and sponges make them ideal models for understanding causal relationships between environmental factors and developmental mechanisms. Here, we identify major questions at the interface between animal evolution and development and outline a road map for research aimed at identifying the mechanisms that link environmental factors to developmental mechanisms in early diverging metazoans. Also watch the Video Abstract.

The apoptotic initiator caspase-8: its functional ubiquity and genetic diversity during animal evolution

The caspases, a family of cysteine proteases, play multiple roles in apoptosis, inflammation, and cellular differentiation. Caspase-8 (Casp8), which was first identified in humans, functions as an initiator caspase in the apoptotic signaling mediated by cell-surface death receptors. To understand the evolution of function in the Casp8 protein family, casp8 orthologs were identified from a comprehensive range of vertebrates and invertebrates, including sponges and cnidarians, and characterized at both the gene and protein levels. Some introns have been conserved from cnidarians to mammals, but both losses and gains have also occurred; a new intron arose during teleost evolution, whereas in the ascidian Ciona intestinalis, the casp8 gene is intronless and is organized in an operon with a neighboring gene. Casp8 activities are near ubiquitous throughout the animal kingdom. Exogenous expression of a representative range of nonmammalian Casp8 proteins in cultured mammalian cells induced cell death, implying that these proteins possess proapoptotic activity. The cnidarian Casp8 proteins differ considerably from their bilaterian counterparts in terms of amino acid residues in the catalytic pocket, but display the same substrate specificity as human CASP8, highlighting the complexity of spatial structural interactions involved in enzymatic activity. Finally, it was confirmed that the interaction with an adaptor molecule, Fas-associated death domain protein, is also evolutionarily ancient. Thus, despite structural diversity and cooption to a variety of new functions, the ancient origins and near ubiquitous distribution of this activity across the animal kingdom emphasize the importance and utility of Casp8 as a central component of the metazoan molecular toolkit.

Piwi expression in archeocytes and choanocytes in demosponges: insights into the stem cell system in demosponges

Little is known about the stem cells of organisms early in metazoan evolution. To characterize the stem cell system in demosponges, we identified Piwi homologs of a freshwater sponge, Ephydatia fluviatilis, as candidate stem cell (archeocyte) markers. EfPiwiA mRNA was expressed in cells with archeocyte cell morphological features. We demonstrated that these EfPiwiA-expressing cells were indeed stem cells by showing their ability to proliferate, as indicated by BrdU-incorporation, and to differentiate, as indicated by the coexpression of EfPiwiA with cell-lineage-specific genes in presumptive committed archeocytes. EfPiwiA mRNA expression was maintained in mature choanocytes forming chambers, in contrast to the transition of gene expression from EfPiwiA to cell-lineage-specific markers during archeocyte differentiation into other cell types. Choanocytes are food-entrapping cells with morphological features similar to those of choanoflagellates (microvillus collar and a flagellum). Their known abilities to transform into archeocytes under specific circumstances and to give rise to gametes (mostly sperm) indicate that even when they are fully differentiated, choanocytes maintain pluripotent stem cell-like potential. Based on the specific expression of EfPiwiA in archeocytes and choanocytes, combined with previous studies, we propose that both archeocytes and choanocytes are components of the demosponge stem cell system. We discuss the possibility that choanocytes might represent the ancestral stem cells, whereas archeocytes might represent stem cells that further evolved in ancestral multicellular organisms.

The stem cell system in demosponges: insights into the origin of somatic stem cells

The stem cell system is one of the unique systems that have evolved only in multicellular organisms. Major questions about this system include what type(s) of stem cells are involved (pluri-, multi- or uni-potent stem cells), and how the self-renewal and differentiation of stem cells are regulated. To understand the origin of the stem cell system in metazoans and to get insights into the ancestral stem cell itself, it is important to discover the molecular and cellular mechanisms of the stem cell system in sponges (Porifera), the evolutionarily oldest extant metazoans. Histological studies here provided a body of evidence that archeocytes are the stem cells in sponges, and recent molecular studies of sponges, especially the finding of the expression of Piwi homologues in archeocytes and choanocytes in a freshwater sponge, Ephydatia fluviatilis, have provided critical insights into the stem cell system in demosponges. Here I introduce archeocytes and discuss (i) modes of archeocyte differentiation, (ii) our current model of the stem cell system in sponges composed of both archeocytes and choanocytes based on our molecular analysis and previous microscopic studies suggesting the maintenance of pluripotency in choanocytes, (iii) the inference that the Piwi and piRNA function in maintaining stem cells (which also give rise to gametes) may have already been achieved in the ancestral metazoan, and (iv) possible hypotheses about how the migrating stem cells arose in the urmetazoan (protometazoan) and about the evolutionary origin of germline cells in the urbilaterian (protobilaterian).

Toward understanding the morphogenesis of siliceous spicules in freshwater sponge: differential mRNA expression of spicule-type-specific silicatein genes in Ephydatia fluviatilis

Siliceous spicules of sponges are morphologically diverse and provide good models for understanding the morphogenesis of biomineralized products. The silica deposition enzyme silicatein is a component of siliceous spicules of sponges and is thought to be the key molecule determining the morphology of spicules. Here, we focused on the silicateins of the freshwater sponge Ephydatia fluviatilis, which has two types of morphologically and functionally different spicules, called megascleres and gemmoscleres. We isolated six isoforms of silicateins and examined their mRNA expression in the cells producing megascleres and gemmoscleres. The spicule-type-specific mRNA expression of these isoforms and differential expression during spicule development suggest that the characteristic morphology of spicules is due to the specific properties and combinatory functions of silicatein isoforms.

The innate immune repertoire in cnidaria--ancestral complexity and stochastic gene loss

Analysis of genomic resources available for cnidarians revealed that several key components of the vertebrate innate immune repertoire are present in representatives of the basal cnidarian class Anthozoa, but are missing in Hydra, a member of the class Hydrozoa, indicating ancient origins for many components of the innate immune system.

Background

Characterization of the innate immune repertoire of extant cnidarians is of both fundamental and applied interest - it not only provides insights into the basic immunological 'tool kit' of the common ancestor of all animals, but is also likely to be important in understanding the global decline of coral reefs that is presently occurring. Recently, whole genome sequences became available for two cnidarians, Hydra magnipapillata and Nematostella vectensis, and large expressed sequence tag (EST) datasets are available for these and for the coral Acropora millepora.

Results

To better understand the basis of innate immunity in cnidarians, we scanned the available EST and genomic resources for some of the key components of the vertebrate innate immune repertoire, focusing on the Toll/Toll-like receptor (TLR) and complement pathways. A canonical Toll/TLR pathway is present in representatives of the basal cnidarian class Anthozoa, but neither a classic Toll/TLR receptor nor a conventional nuclear factor (NF)-κB could be identified in the anthozoan Hydra. Moreover, the detection of complement C3 and several membrane attack complex/perforin domain (MAC/PF) proteins suggests that a prototypic complement effector pathway may exist in anthozoans, but not in hydrozoans. Together with data for several other gene families, this implies that Hydra may have undergone substantial secondary gene loss during evolution. Such losses are not confined to Hydra, however, and at least one MAC/PF gene appears to have been lost from Nematostella.

Conclusion

Consideration of these patterns of gene distribution underscores the likely significance of gene loss during animal evolution whilst indicating ancient origins for many components of the vertebrate innate immune system.

Two different evolutionary origins of stem cell systems and their molecular basis

We propose two major evolutionary origins of stem cell systems in the animal kingdom. Adult pluripotent stem cell systems are found in many invertebrates and probably evolved as components of asexual reproduction. Lineage-specific stem cell systems probably evolved later and include neural and hematopoietic stem cell types. We propose that these two types of stem cell systems evolved independently. The vasa-like genes regulate reproductive stem cells, but not lineage-specific stem cells, which may be regulated by gcm genes. Here, we review the evidence for the molecular basis for the evolutionary origin of these two different stem cell systems.

Isolation of Ef silicatein and Ef lectin as Molecular Markers Sclerocytes and Cells Involved in Innate Immunity in the Freshwater Sponge Ephydatia fluviatilis

Sponges (phylum Porifera) have remarkable regenerative and reconstitutive abilities and represent evolutionarily the oldest metazoans. To investigate sponge stem cell differentiation, we have focused on the asexual reproductive system in the freshwater sponge Ephydatia fluviatilis. During germination, thousands of stem cells proliferate and differentiate to form a fully functional sponge. As an initial step of our investigation of stem cell (archeocyte) differentiation, we isolated molecular markers for two differentiated cell types: spicule-making sclerocyte cells, and cells involved in innate immunity. Sclerocyte lineage-specific Ef silicatein shares 45% to 62% identity with other sponge silicateins. As in situ hybridization of Ef silicatein specifically detects archeocytes possibly committed to sclerocytes, as well as sclerocytes with an immature or mature spicule, therefore covering all the developmental stages, we conclude that Ef silicatein is a suitable sclerocyte lineage marker. Ef lectin, a marker for the cell type involved in innate immunity, shares 59% to 65% identity with the marine sponge Suberites domuncula galactose-binding protein (Sd GBP) and horseshoe crab Tachypleus tridentatus tachylectin1/lectinL6. Since Sd GBP and tachylectin1 are known to bind to bacterial lipopolysaccharides and inhibit the growth of bacteria, Ef lectin may have a similar function and be expressed in a specialized type of cell involved in defense against invading bacteria. Ef lectin mRNA and protein are not expressed in early stages of development, but are detected in late stages. Therefore, Ef lectin may be specifically expressed in differentiating and/or differentiated cells. We suggest Ef lectin as a marker for cells that assume innate immunity in freshwater sponges.

Isolation of the choanocyte in the fresh water sponge, Ephydatia fluviatilis and its lineage marker, Ef annexin

In order to investigate the cellular system of the freshwater sponge, Ephydatia fluviatilis, we isolated a molecular marker for the most prominent cell type, the choanocyte. After feeding sponge with fluorescent beads, fluorescent-labeled choanocytes were collected by fluorescence activated cell sorting (FACS). By protein profiling choanocyte and archeocyte (stem cell)-rich fractions, proteins characteristic of choanocyte were identified. The partial amino-acid sequence of one of the proteins characteristic of choanocyte matches the deduced amino-acid sequence of sponge expression tag (EST) clones and mouse annexin VII. These EST clones overlap and encode a protein, designated Ef annexin, which includes four annexin domains. Whole mount in situ hybridization shows Ef annexin expression in chamber-forming choanocytes in 7-day-old sponge, leading us to conclude that Ef annexin can be used as a choanocyte marker. In the early development stage, Ef annexin expression can be detected in both large single cells, characteristic of archeocytes, and cells forming 2-, 4- and multiple-cell clusters. These results indicate that Ef annexin is initially expressed in the choanocyte-committed archeocyte which then undergoes several mitotic cell divisions to form a choanocyte chamber. This suggests that the single choanocyte chamber essentially originates from a single archeocyte.

[Prevalence of cervical and cerebral atherosclerosis and silent brain infarction in patients with multivessel coronary artery disease]

OBJECTIVES

This clinical study investigated the prevalence of cervical and cerebral atherosclerosis and silent brain infarction in patients with coronary artery disease.

METHODS

Cervical and cerebral magnetic resonance angiography(MRA) was performed in 133 patients (98 males, 35 females, mean age 65.3 years) with suspected coronary artery disease, who were divided into a zero- and one-vessel disease group(n = 71) and a two- and three-vessel disease group(n = 62) depending on the number of major coronary branches with 75% or more stenosis. The MRA lesion was defined as more than 50% stenosis. Magnetic resonance imaging(MRI) of the brain was performed within 1 week of MRA in 78 patients without symptomatic stroke and atrial fibrillation. Silent brain infarction on MRI was defined as a focal high intensity area on T2-weighted images larger than 3 mm.

RESULTS

The prevalence of MRA lesions was significantly greater in the two- and three-vessel group than in the zero- and one-vessel group(53% vs 14%, p < 0.01). The prevalence of MRI lesion was significantly higher in the two- and three-vessel group than in the zero- and one-vessel group(77% vs 36%, p < 0.01). The size and number of the MRI lesions were also significantly greater in the two- and three-vessel group than in the zero- and one-vessel group(p < 0.01). Neither age nor percentage of male gender was different between the groups. Diabetes mellitus was the common risk factor for coronary artery disease, MRA lesion and MRI lesion.

CONCLUSIONS

Cervical and cerebral atherosclerosis and silent brain infarction are frequently observed in patients with multivessel coronary artery disease.

Coelom formation: binary decision of the lateral plate mesoderm is controlled by the ectoderm

Most triploblastic animals including vertebrates have a coelomic cavity that separates the outer and inner components of the body. The coelom is lined by two different tissue components, somatopleure and splanchnopleure, which are derived from the lateral plate region. Thus, the coelom is constructed as a result of a binary decision during early specification of the lateral plate. In this report we studied the molecular mechanisms of this binary decision. We first demonstrate that the splitting of the lateral plate into the two cell sheets progresses in an anteroposterior order and this progression is not coordinated with that of the somitic segmentation. By a series of embryological manipulations we found that young splanchnic mesoderm is still competent to be respecified as somatic mesoderm, and the ectoderm overlying the lateral plate is sufficient for this redirection. The lateral ectoderm is also required for maintenance of the somatic character of the mesoderm. Thus, the ectoderm plays at least two roles in the early subdivision of the lateral plate: specification and maintenance of the somatic mesoderm. We also show that the latter interactions are mediated by BMP molecules that are localized in the lateral ectoderm. Evolutionary aspects of the coelom formation are also considered.

Mesodermal subdivision along the mediolateral axis in chicken controlled by different concentrations of BMP-4

Molecular mechanisms by which the mesoderm is subdivided along the mediolateral axis in early chicken embryos have been studied. When the presomitic mesoderm (medial mesoderm) was transplanted into the lateral plate, the graft was transformed into lateral plate tissue, indicating that the primitive somite was not fully committed and that the lateral plate has a cue for mesodermal lateralization. Since the lateral plate expresses a high level of BMP-4 mRNA, a member of the TGF-beta family, we hypothesized that it is the molecule responsible for the lateralization of the somite. To test this, we transplanted COS cells producing BMP-4 into the presomitic region. Those cells locally prevented the presomitic cells from differentiating into somites, converting them instead into lateral plate mesoderm, which was revealed by expression of cytokeratin mRNA, a marker for the lateral plate. The effect was dependent on the level of effective BMP-4: with a high level of BMP-4, the somite was transformed completely to lateral plate; with a low level, the somite formed but was occupied by the lateral somitic component expressing cSim 1, a marker for the lateral somite. These results suggest that different thresholds of effective BMP-4 determine distinct subtypes of the mesoderm as a lateralizer during early development.

Analysis of DNA inversions in the shufflon of plasmid R64

The shufflon, a multiple DNA inversion system in the plasmid R64, consists of four DNA segments flanked and separated by seven 19-bp repeat sequences. Site-specific recombinations mediated by the rci product occur between each inverted repeat sequence, resulting in inversions of the four segments independently or in groups. The seven 19-bp repeat sequences are classified into four types (repeat-a, -b, -c, and -d), according to their 3-bp variable sequences. We individually cloned A, B, and C segments of the R64 shufflon and determined the in vivo inversion frequency of each segment. The inversion frequencies of three segments differed greatly. The inversion frequency declined in the following order: segments A, B, and C. Synthetic 19-mer oligonucleotides corresponding to both strands of repeat-a, -b, -c, and -d sequences were inserted into appropriate sites of pBR322. The rci-mediated DNA inversion occurred between two synthetic inverted repeats, indicating that the 19-bp inverted repeat sequences are the sole elements required in cis for the shufflon system. The inversion frequencies of DNA segments flanked by various sequences indicate that the four types of repeat sequences determine the inversion frequency of the four DNA segments of the R64 shufflon. Deletion of a DNA segment flanked by direct repeat sequences could not be detected.

Binding to cadherins antagonizes the signaling activity of beta-catenin during axis formation in Xenopus

beta-Catenin, a cytoplasmic protein known for its association with cadherin cell adhesion molecules, is also part of a signaling cascade involved in embryonic patterning processes such as the determination of the dorsoventral axis in Xenopus and determination of segment polarity in Drosophila. Previous studies suggest that increased cytoplasmic levels of beta-catenin correlate with signaling, raising questions about the need for in- teraction with cadherins in this process. We have tested the role of the beta-catenin-cadherin interaction in axis formation. Using beta-catenin deletion mutants, we demonstrate that significant binding to cadherins can be eliminated without affecting the signaling activity. Also, depletion of the soluble, cytosolic pool of beta-catenin by binding to overexpressed C-cadherin completely inhibited beta-catenin-inducing activity. We conclude that binding to cadherins is not required for beta-catenin signaling, and therefore the signaling function of beta-catenin is independent of its role in cell adhesion. Moreover, because beta-catenin signaling is antagonized by binding to cadherins, we suggest that cadherins can act as regulators of the intracellular beta-catenin signaling pathway.

Inhibitory effects of d-nicotine on the responses evoked by 1-isomer in trachea and bronchus isolated from guinea-pig and rabbit

1. The effects of d-nicotine on the responses induced by 1-isomer were studied in tracheae and bronchi isolated from guinea-pigs and rabbits. In guinea-pigs trachea 1-nicotine produced a biphasic response consisting of initial contraction and following relaxation. In other airway preparations 1-nicotine produced only contraction. 2. d-Nicotine did not produce any responses except for the case of guinea-pig trachea. d-isomer produced only relaxation and relative potency was approximately 0.44 in guinea-pig trachea. 3. Pretreatment with d-nicotine (30-300 microM) reduced concentration response curves for 1-isomer in a non-competitive manner in all preparations used in this study. 4. 1-nicotine at the concentration of 3 microns, which did not produce any response itself, reduced the concentration response curve of 1-nicotine in guinea-pig trachea. 5. Inhibition by d-nicotine or 1-nicotine (3 microM) of the concentration-response curve of 1-nicotine may be due to desensitization of nicotine receptors.

Embryonic axis induction by the armadillo repeat domain of beta-catenin: evidence for intracellular signaling

beta-catenin was identified as a cytoplasmic cadherin-associated protein required for cadherin adhesive function (Nagafuchi, A., and M. Takeichi. 1989. Cell Regul. 1:37-44; Ozawa, M., H. Baribault, and R. Kemler. 1989. EMBO [Eur. Mol. Biol. Organ.] J. 8:1711-1717). Subsequently, it was found to be the vertebrate homologue of the Drosophila segment polarity gene product Armadillo (McCrea, P. D., C. W. Turck, and B. Gumbiner. 1991. Science [Wash. DC]. 254:1359-1361; Peifer, M., and E. Wieschaus. 1990. Cell. 63:1167-1178). Also, antibody perturbation experiments implicated beta-catenin in axial patterning of the early Xenopus embryo (McCrea, P. D., W. M. Brieher, and B. M. Gumbiner. 1993. J. Cell Biol. 123:477-484). Here we report that overexpression of beta-catenin in the ventral side of the early Xenopus embryo, by injection of synthetic beta-catenin mRNA, induces the formation of a complete secondary body axis. Furthermore, an analysis of beta-catenin deletion constructs demonstrates that the internal armadillo repeat region is both necessary and sufficient to induce axis duplication. This region interacts with C-cadherin and with the APC tumor suppressor protein, but not with alpha-catenin, that requires the amino-terminal region of beta-catenin to bind to the complex. Since alpha-catenin is required for cadherin-mediated adhesion, the armadillo repeat region alone probably cannot promote cell adhesion, making it unlikely that beta-catenin induces axis duplication by increasing cell adhesion. We propose, rather, that beta-catenin acts in this circumstance as an intracellular signaling molecule. Subcellular fractionation demonstrated that all of the beta-catenin constructs that contain the armadillo repeat domain were present in both the soluble cytosolic and the membrane fraction. Immunofluorescence staining confirmed the plasma membrane and cytoplasmic localization of the constructs containing the armadillo repeat region, but revealed that they also accumulate in the nucleus, especially the construct containing only the armadillo repeat domain. These findings and the beta-catenin protein interaction data offer several intriguing possibilities for the site of action or the protein targets of beta-catenin signaling activity.

Effects of ageing on regional differences in the contractile responses to acetylcholine and neurokinin A in rabbit airway

1. Experiments were designed to study the effects of ageing on muscarine and NK2 receptor mechanisms in the three different regions of rabbit airway. 2. The pD2 value of acetylcholine changed with age in three different regions while that of carbamylcholine, which is resistant to acetylcholinesterase, did not. 3. The pD2 values of neurokinin A and the activity of protease, a degradative enzyme, changed with age. However, by the pretreatment with phosphoramidon, a protease inhibitor, the regional difference and age related change of the pD2 value of neurokinin A disappeared. 4. In conclusion, the observations about age related changes and regional differences of pD2 value of acetylcholine and neurokinin A were due to the difference of their degradative enzyme activities.

[A case of acute myocardial infarction complicated with left ventricular pseudoaneurysm and ventricular septal rupture]

An 87-year-old woman was admitted to another hospital with acute inferior myocardial infarction on May 31, 1991. On the 6th hospital day she suddenly developed transient complete A-V block and ventricular tachycardia. She was transferred to our hospital for the treatment of intractable heart failure on the 18th hospital day. Two-dimensional echocardiography showed a saccular chamber with a narrow-necked connection to the left ventricle. Color Doppler echocardiography showed bidirectional blood flow between the left ventricle and saccular chamber during systole and diastole. There was 35% left to right shunt in the ventricular level on right heart catheterization. Acute myocardial infarction complicated with left ventricular pseudoaneurysm and ventricular septal perforation was diagnosed. She died on the 26th hospital day without aggressive medical treatment. Autopsy demonstrated the pseudoaneurysm in the posterior wall of the left ventricle and the connection to the right ventricle. The so-called double rupture could be diagnosed before death.

Perturbation of cell adhesion and microvilli formation by antisense oligonucleotides to ERM family members

To examine the functions of ERM family members (ezrin, radixin, and moesin), mouse epithelial cells (MTD-1A cells) and thymoma cells (L5178Y), which coexpress all of them, were cultured in the presence of antisense phosphorothioate oligonucleotides (PONs) complementary to ERM sequences. Immunoblotting revealed that the antisense PONs selectively suppressed the expression of each member. Immunofluorescence microscopy of these ezrin, radixin, or moesin "single-suppressed" MTD-1A cells revealed that the ERM family members are colocalized at cell-cell adhesion sites, microvilli, and cleavage furrows, where actin filaments are densely associated with plasma membranes. The ezrin/radixin/moesin antisense PONs mixture induced the destruction of both cell-cell and cell-substrate adhesion, as well as the disappearance of microvilli. Ezrin or radixin antisense PONs individually affected the initial step of the formation of both cell-cell and cell-substrate adhesion, but did not affect the microvilli structures. In sharp contrast, moesin antisense PONs did not singly affect cell-cell and cell-substrate adhesion, whereas it partly affected the microvilli structures. These data indicate that ezrin and radixin can be functionally substituted, that moesin has some synergetic functional interaction with ezrin and radixin, and that these ERM family members are involved in cell-cell and cell-substrate adhesion, as well as microvilli formation.

A regional difference of the effect of tachykinin on cholinergic response evoked by electrical field stimulation in the rabbit airway

1. Experiments were designed to determine whether regional differences exist in the effects of phosphoramidon (a metalloprotease inhibitor) and [D-Arg,1D-Pro,2 D-Trp,7,9Leu,11]-substance P (a tachykinin antagonist: rpwwL-SP) on contractile responses to electrical field stimulation (EFS) in rabbit airways. 2. EFS contractions were potentiated by phosphoramidon and were attenuated by rpwwL-substance P at low frequencies (less than 10 Hz). 3. Potentiating effect of phosphoramidon was more pronounced in distal bronchus than trachea and was proportional to total proteinase activity. 4. The rank order of inhibitory effect of rpwwL-SP was: trachea > proximal bronchus > distal bronchus, and inverse relationship was observed between the drug's inhibitory effect of drug and total proteinase activity in three different regions. 5. Good correlation was observed between total proteinase activity and pD2 value of neurokinin A in each airway region. 6. In conclusion, tachykinin modulates acetylcholine release in the contractile response to EFS at low frequencies (less than 10 Hz), and regional differences in the effects of the inhibitor and the antagonist on EFS-evoked contractions in the rabbit airway were suggested to be due to heterogenous distribution of the metalloprotease which metabolized tachykinins.

Nucleotide sequence and characterization of the traABCD region of IncI1 plasmid R64

A 3.6-kb BglII-SmaI segment of the transfer region of IncI1 plasmid R64drd-11 was sequenced and characterized. Analysis of the DNA sequence indicated the presence of four genes, traA, traB, traC, and traD, in this region. The expression of the traB, traC, and traD genes was examined by maxicell experiments and that of the traA gene was examined by constructing the traA-lacZ fusion gene. The introduction of frameshift mutations into the four genes indicated that the traB and traC genes are essential for conjugal transfer in liquid medium and on a solid surface. Both were also required for the formation of the thin pilus, which is the receptor for phages I alpha and PR64FS. Upstream of the traA gene, a promoter sequence for sigma 70 of E. coli RNA polymerase was identified by S1 nuclease mapping and primer extension experiments.

[Left ventricular aneurysm with normal coronary arteriogram after myocardial infarction]

Left ventricular aneurysms after myocardial infarction are generally considered one of the complications of severe coronary artery disease. Postinfarction ventricular aneurysms with normal coronary arteriogram are rare. Only a few cases have been reported previously in Japan. We examined the incidence and the clinical characteristics of postinfarction ventricular aneurysms without coronary obstruction. Among the consecutive 1800 patients studied in our laboratory with selective coronary cineangiography and left ventriography, we found 5 (4 male, 1 female) patients with left ventricular aneurysms with no or minimal coronary arterial obstruction. The patient's ages ranged from 34 to 83 with a mean of 59. Interestingly, no patient had prior anginal history, and every case occurred with a first sudden attack of chest pain. The likely mechanisms causing the development of myocardial infarction were coronary spasm and/or thromboembolic accident. One patient, in whom a coronary induction test was performed, showed positive findings. It is possible that poor collateral circulation and well preserved contraction of viable myocardium in these patients bring about the formation of left ventricular aneurysm after myocardial infarction with normal coronary arteriogram.

Regional differences of the contractile responses to acetylcholine and neurokinin A in rabbit airway: heterogeneous distribution of the metabolic enzymes

1. Experiments were designed to determine whether differences exist in the sensitivity to muscarinic and tachykinin agonists in rabbit airways. 2. The rank order of sensitivity (pD2 value) to acetylcholine was: trachea > proximal bronchus > distal bronchus, whereas no regional difference was observed in the sensitivity to carbamylcholine which is resistant to acetylcholinesterase. 3. Acetylcholinesterase activity was greater in the distal than in the proximal airway. 4. In the absence of the peptidase inhibitor, phosphoramidon, the pD2 values of neurokinin A (NKA) and substance P (SP) in trachea were significantly greater than that in bronchus, whereas no regional difference was observed in the NK1 selective agonist, substance P methyl ester (SPOMe). 5. Application of phosphoramidon (10 microM) to avoid peptide degradation abolished the regional difference of the pD2 values of SP. 6. In conclusion, regional differences in sensitivities to acetylcholine and NKA in the rabbit airway were suggested to be due to distribution to the metabolic enzymes of these drugs.

A gene family consisting of ezrin, radixin and moesin. Its specific localization at actin filament/plasma membrane association sites

Radixin is a barbed end-capping actin-modulating protein which was previously reported to be concentrated at cell-to-cell adherens junctions (AJ) and cleavage furrows. Recently, cDNA encoding mouse radixin was isolated, showing that radixin is highly homologous to but distinct from ezrin. From mouse teratocarcinoma cells we isolated and analyzed cDNA encoding another radixin-related protein. Sequence analysis has demonstrated that this protein is a mouse homologue of human moesin (98.3% identity) and that it shares 71.7% and 80.1% identity with ezrin and radixin, respectively. Translation experiments in vitro combined with immunoblot analyses led us to conclude that there is a gene family consisting of ezrin, radixin and moesin. These members are coexpressed in various types of cells. Then, by immunofluorescence microscopy, we closely analyzed their distribution using polyclonal and monoclonal antibodies, which could recognize all three members. In addition to cell-to-cell AJ and cleavage furrows, it was shown that they were concentrated at microvilli and ruffling membranes in various types of cells. Furthermore, the cell-to-substrate AJ (focal contacts) were clearly stained by anti-radixin pAb only after the apical/lateral membranes and cytoplasm were removed by the zinc method. We conclude that at least one of the members of the ezrin-radixin-moesin family is concentrated at specific regions where actin filaments are densely associated with plasma membranes.

Radixin is a novel member of the band 4.1 family

Radixin is an actin barbed-end capping protein which is highly concentrated in the undercoat of the cell-to-cell adherens junction and the cleavage furrow in the interphase and mitotic phase, respectively (Tsukita, Sa., Y. Hieda, and Sh. Tsukita. 1989 a.J. Cell Biol. 108:2369-2382; Sato, N., S. Yonemura, T. Obinata, Sa. Tsukita, and Sh. Tsukita. 1991. J. Cell Biol. 113:321-330). To further understand the structure and functions of the radixin molecule, we isolated and sequenced the cDNA clones encoding mouse radixin. Direct peptide sequencing of radixin and immunological analysis with antiserum to a fusion protein were performed to confirm that the protein encoded by these clones is identical to radixin. The composite cDNA is 4,241 nucleotides long and codes for a 583-amino acid polypeptide with a calculated molecular mass of 68.5 kD. Sequence analysis has demonstrated that mouse radixin shares 75.3% identity with human ezrin, which was reported to be a member of the band 4.1 family. We then isolated the cDNA encoding mouse ezrin. Sequence analysis and Northern blot analysis revealed that radixin and ezrin are similar but distinct (74.9% identity), leading us to conclude that radixin is a novel member of the band 4.1 family. In erythrocytes the band 4.1 protein acts as a key protein in the association of short actin filaments with a plasma membrane protein (glycophorin), together with spectrin. Therefore, the sequence similarity between radixin and band 4.1 protein described in this study favors the idea that radixin plays a crucial role in the association of the barbed ends of actin filaments with the plasma membrane in the cell-to-cell adherens junction and the cleavage furrow.

Transfer region of IncI1 plasmid R64 and role of shufflon in R64 transfer

To locate the transfer region of the 122-kiloase plasmid R64drd-11 belonging to incompatibility group I1, a series of deletion derivatives was constructed by in vitro recombinant DNA techniques followed by double homologous recombination in vivo. A plasmid designated pKK609 and bearing a 56.7-kilobase R64 sequence was the smallest transferable plasmid. A plasmid designated pKK610 and no longer possessing the 44-base-pair sequence of the R64 transfer system is located at one end. The other end of the R64 transfer region comprises a DNA segment of about 19 kilobases responsible for pilus formation. Shufflon, DNA with a novel rearrangement in R64, was found to be involved in pilus formation.

Physical and genetic analyses of IncI2 plasmid R721: evidence for the presence of shufflon

A physical map of the 75.1-kb IncI2 plasmid R721 was constructed by using 15 restriction enzymes, and the regions of several genetic determinants including the origins of replication and of conjugal DNA transfer were located on the physical map. It was found that R721 bears a DNA region which undergoes DNA rearrangement similar to the shufflon of R64.

Regeneration of endothelial cells after balloon denudation of the rabbit carotid artery and changes in responsiveness

The present experiments were carried out to determine the regrowth of endothelial cells (EC) after balloon denudation of the rabbit carotid artery and the changes in responsiveness of the artery with regenerated EC. Scanning electron microscopic findings revealed that 28.8% of the luminal surface was covered with regenerated EC at week 1. The regrowth of EC proceeded progressively, and a full lining was achieved at week 6. Regenerated EC were morphologically different from native ones; they were elongated (weeks 1 and 2) and irregularly oriented (weeks 4 and 6), and their numbers had significantly increased. Light microscopy revealed the intimal thickening and proliferation of smooth muscle cells. No accumulation of lipids in the vascular wall could be detected at any observation time. The experiments in an organ bath demonstrated that the altered appearance of EC was accompanied by depressed endothelium-dependent relaxations to acetylcholine, ADP and A23187. However, sodium nitroprusside-induced relaxation and contractile responses to noradrenaline, serotonin and histamine remained unchanged in the normal and denuded preparations, indicating that the dysfunction of the endothelium occurs at a time when the ability of the underlying vascular smooth muscle to relax or contract was unchanged. In addition, it is suggested that the impairment of the endothelium-dependent relaxation may be partly due to impairment of the synthesis and/or release of endothelium-derived relaxing factor(s) in EC.

Histological evidence of left ventricular involvement in arrhythmogenic right ventricular dysplasia

A 40-year-old female with arrhythmogenic right ventricular dysplasia (ARVD) demonstrated a reduced motion of the left ventricular (LV) apex. Specimens of LV free wall, obtained by endomyocardial biopsy, histologically revealed prominent interstitial fibrosis with sparse distribution of myocytes. The myocytes were hypertrophic and disrupted with loss of myofibrils. This is a case of ARVD, where LV involvement was histologically verified.