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Reyes MP, Cuenca JA, Heatter J, Martin PR, Villalobos DHD, Nates JL. Tribulations of conducting critically ill cancer patients research: Lessons from a failed septic shock trial and Murphy's law. Med Intensiva 2022; 46:582-585. [PMID: 36155682 DOI: 10.1016/j.medine.2021.10.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Accepted: 10/31/2021] [Indexed: 06/16/2023]
Affiliation(s)
- M P Reyes
- Department of Critical Care Medicine, Division of Anesthesiology, Critical Care, and Pain Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - J A Cuenca
- Department of Critical Care Medicine, Division of Anesthesiology, Critical Care, and Pain Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - J Heatter
- Department of Critical Care Medicine, Division of Anesthesiology, Critical Care, and Pain Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - P R Martin
- Department of Critical Care Medicine, Division of Anesthesiology, Critical Care, and Pain Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - D H D Villalobos
- Department of Critical Care Medicine, Division of Anesthesiology, Critical Care, and Pain Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - J L Nates
- Department of Critical Care Medicine, Division of Anesthesiology, Critical Care, and Pain Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA.
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Ali F, Whitwell JL, Martin PR, Senjem ML, Knopman DS, Jack CR, Lowe VJ, Petersen RC, Boeve BF, Josephs KA. [ 18F] AV-1451 uptake in corticobasal syndrome: the influence of beta-amyloid and clinical presentation. J Neurol 2018; 265:1079-1088. [PMID: 29497818 DOI: 10.1007/s00415-018-8815-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Revised: 02/09/2018] [Accepted: 02/26/2018] [Indexed: 12/12/2022]
Abstract
Corticobasal syndrome (CBS) is a phenotypic manifestation of diverse pathologies, including Alzheimer's disease and 4-repeat tauopathies. Predicting pathology in CBS is unreliable and, hence, molecular neuroimaging may prove to be useful. The aim of this study was to assess regional patterns of uptake on [18F] AV-1451 PET in CBS and determine whether patterns of uptake differ according to beta-amyloid deposition or differing clinical presentations. Fourteen patients meeting criteria for CBS underwent Pittsburgh Compound B (PiB) and [18F] AV-1451 PET. Seven patients presented as CBS and seven presented with apraxia of speech (AOS) and later evolved into CBS. A global PiB summary was calculated and used to classify patients as PiB (-) or PiB (+). AV-1451 uptake was calculated in fourteen regions-of-interest, with values divided by uptake in cerebellar crus grey matter to generate standard uptake value ratios. AV-1451 uptake was considered elevated if it fell above the 95th percentile from a group of 476 cognitively unimpaired normal controls. Six of the 14 CBS patients (43%) were PiB (+), with three of these patients showing strikingly elevated AV-1451 uptake across many cortical regions. Of the eight PiB (-) patients, only those with AOS showed elevated AV-1451 uptake in supplementary motor area and precentral cortex compared to controls. No region of elevated AV-1451 uptake were observed in PiB (-) typical CBS patients without AOS. These results suggest that regional [18F] AV-1451 is variable in CBS and depends on the presence of beta-amyloid as well as clinical presentation such as AOS. PiB (+) CBS does not necessarily reflect underlying Alzheimer's disease; however, the possibility some of these patients will evolve into Alzheimer's disease over time cannot be excluded.
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Affiliation(s)
- F Ali
- Department of Neurology, Mayo Clinic, 200 1st St SW, Rochester, MN, 55905, USA.
| | - J L Whitwell
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | - P R Martin
- Department of Health Sciences Research (Biostatistics), Mayo Clinic, Rochester, MN, USA
| | - M L Senjem
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | - D S Knopman
- Department of Neurology, Mayo Clinic, 200 1st St SW, Rochester, MN, 55905, USA
| | - C R Jack
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | - V J Lowe
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | - R C Petersen
- Department of Neurology, Mayo Clinic, 200 1st St SW, Rochester, MN, 55905, USA
| | - B F Boeve
- Department of Neurology, Mayo Clinic, 200 1st St SW, Rochester, MN, 55905, USA
| | - K A Josephs
- Department of Neurology, Mayo Clinic, 200 1st St SW, Rochester, MN, 55905, USA
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Rohwer VG, Bonier F, Martin PR. Conflict between biotic and climatic selective pressures acting on an extended phenotype in a subarctic, but not temperate, environment. Proc Biol Sci 2016; 282:20151585. [PMID: 26490789 DOI: 10.1098/rspb.2015.1585] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Climatic selective pressures are thought to dominate biotic selective pressures at higher latitudes. However, few studies have experimentally tested how these selective pressures differentially act on traits across latitudes because traits can rarely be manipulated independently of the organism in nature. We overcame this challenge by using an extended phenotype-active bird nests-and conducted reciprocal transplant experiments between a subarctic and temperate site, separated by 14° of latitude. At the subarctic site, biotic selective pressures (nest predation) favoured smaller, non-local temperate nests, whereas climatic selective pressures (temperature) favoured larger local nests, particularly at colder temperatures. By contrast, at the temperate site, climatic and biotic selective pressures acted similarly on temperate and subarctic nests. Our results illustrate a functional trade-off in the subarctic between nest morphologies favoured by biotic versus climatic selective pressures, with climate favouring local nest morphologies. At our temperate site, however, allocative trade-offs in the time and effort devoted to nest construction favour smaller, local nests. Our findings illustrate a conflict between biotic and climatic selective pressures at the northern extremes of a species geographical range, and suggest that trade-offs between trait function and trait elaboration act differentially across latitude to create broad geographic variation in traits.
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Affiliation(s)
- V G Rohwer
- Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6
| | - F Bonier
- Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6
| | - P R Martin
- Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6
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Pietersen ANJ, Cheong SK, Solomon SG, Tailby C, Martin PR. Temporal response properties of koniocellular (blue-on and blue-off) cells in marmoset lateral geniculate nucleus. J Neurophysiol 2014; 112:1421-38. [DOI: 10.1152/jn.00077.2014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Visual perception requires integrating signals arriving at different times from parallel visual streams. For example, signals carried on the phasic-magnocellular (MC) pathway reach the cerebral cortex pathways some tens of milliseconds before signals traveling on the tonic-parvocellular (PC) pathway. Visual latencies of cells in the koniocellular (KC) pathway have not been specifically studied in simian primates. Here we compared MC and PC cells to “blue-on” (BON) and “blue-off” (BOF) KC cells; these cells carry visual signals originating in short-wavelength-sensitive (S) cones. We made extracellular recordings in the lateral geniculate nucleus (LGN) of anesthetized marmosets. We found that BON visual latencies are 10–20 ms longer than those of PC or MC cells. A small number of recorded BOF cells ( n = 7) had latencies 10–20 ms longer than those of BON cells. Within all cell groups, latencies of foveal receptive fields (<10° eccentricity) were longer (by 3–8 ms) than latencies of peripheral receptive fields (>10°). Latencies of yellow-off inputs to BON cells lagged the blue-on inputs by up to 30 ms, but no differences in visual latency were seen on comparing marmosets expressing dichromatic (“red-green color-blind”) or trichromatic color vision phenotype. We conclude that S-cone signals leaving the LGN on KC pathways are delayed with respect to signals traveling on PC and MC pathways. Cortical circuits serving color vision must therefore integrate across delays in (red-green) chromatic signals carried by PC cells and (blue-yellow) signals carried by KC cells.
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Affiliation(s)
- A. N. J. Pietersen
- Australian Research Council Centre of Excellence for Integrative Brain Function, University of Sydney, Sydney, Australia
- Save Sight Institute, University of Sydney, Sydney, Australia
| | - S. K. Cheong
- Australian Research Council Centre of Excellence for Integrative Brain Function, University of Sydney, Sydney, Australia
- Save Sight Institute, University of Sydney, Sydney, Australia
| | - S. G. Solomon
- School of Medical Sciences, University of Sydney, Sydney, Australia
- Department of Experimental Psychology, University College London, London, United Kingdom; and
| | - C. Tailby
- School of Medical Sciences, University of Sydney, Sydney, Australia
- Florey Institute of Neuroscience and Mental Health, Heidelberg, Australia
| | - P. R. Martin
- Australian Research Council Centre of Excellence for Integrative Brain Function, University of Sydney, Sydney, Australia
- Save Sight Institute, University of Sydney, Sydney, Australia
- School of Medical Sciences, University of Sydney, Sydney, Australia
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Jones HE, Heil SH, O'Grady KE, Martin PR, Kaltenbach K, Coyle MG, Stine SM, Selby P, Arria AM, Fischer G. Smoking in pregnant women screened for an opioid agonist medication study compared to related pregnant and non-pregnant patient samples. Am J Drug Alcohol Abuse 2010; 35:375-80. [PMID: 20180667 DOI: 10.1080/00952990903125235] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND Little is known about the prevalence and severity of smoking in pregnant opioid dependent patients. OBJECTIVES To first characterize the prevalence and severity of smoking in pregnant patients screened for a randomized controlled trial, Maternal Opioid Treatment: Human Experimental Research (MOTHER), comparing two agonist medications; and second, to compare the MOTHER screening sample to published samples of other pregnant and/or patients with substances use disorders. METHODS Pregnant women (N = 108) screened for entry into an agonist medication comparison study were retrospectively compared on smoking variables to samples of pregnant methadone-maintained patients (N = 50), pregnant opioid or cocaine dependent patients (N = 240), non-pregnant methadone-maintained women (N = 75), and pregnant non-drug-addicted patients (N = 1,516). RESULTS Of screened patients, 88% (n = 95) smoked for a mean of 140 months (SD = 79.0) starting at a mean age of 14 (SD = 3.5). This rate was similar to substance use disordered patients and significantly higher compared to general pregnant patients (88% vs. 22%, p < .001). CONCLUSION AND SCIENTIFIC SIGNIFICANCE Aggressive efforts are needed to reduce/eliminate smoking in substance-abusing pregnant women.
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Affiliation(s)
- H E Jones
- Department of Psychiatry, Johns Hopkins University, Baltimore, Maryland, USA.
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Martin PR, Tailby C, Szmajda B, Buzas P, Lee BB. Contribution of blue (S) cone signals to classical and extraclassical receptive fields in the lateral geniculate nucleus. J Vis 2010. [DOI: 10.1167/8.17.10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Clifford CW, Spehar B, Solomon SG, Martin PR, Zaidi Q. Colour-luminance interactions in human orientation perception. J Vis 2010. [DOI: 10.1167/2.7.215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Abstract
The standard clinical advice for individuals who suffer from recurrent headaches is that the best way to prevent headaches is to avoid the triggers. This editorial challenges that advice from a number of perspectives. First, there is little empirical support for such advice. Second, cognate literatures in the fields of chronic pain, stress and anxiety raise concerns about avoidance as a strategy. Third, studies have demonstrated that short exposure to a headache trigger results in increased sensitivity and prolonged exposure results in decreased sensitivity. Conclusions include that one aetiological pathway to developing a primary headache disorder may be via attempts to avoid triggers resulting in increased sensitivity to triggers. Also, clinicians need to become more flexible in the advice they give pertaining to triggers, namely they should think ‘coping with triggers’ rather than avoiding all triggers, as avoidance will sometimes be the preferred strategy, but often it will not be.
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Affiliation(s)
- PR Martin
- Monash University, Division of Psychological Medicine, Melbourne, Vic., Australia
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Abstract
This study concerns the transmission of short-wavelength-sensitive (S) cone signals through the primate dorsal lateral geniculate nucleus. The principal cell classes, magnocellular (MC) and parvocellular (PC), are traditionally segregated into on- and off-subtypes on the basis of the sign of their response to luminance variation. Cells dominated by input from S-cones ('blue-on and blue-off') are less frequently encountered and their properties are less well understood. Here we characterize the spatial and chromatic properties of a large sample of blue-on and blue-off neurons and contrast them with those of PC and MC neurons. The results confirm that blue-on and blue-off cells have larger receptive fields than PC and MC neurons at equivalent eccentricities. Relative to blue-on cells, blue-off cells are less sensitive to S-cone contrast, have larger receptive fields, and show more low-pass spatial frequency tuning. Thus, blue-on and blue-off neurons lack the functional symmetry characteristic of on- and off-subtypes in the MC and PC pathways. The majority of MC and PC cells received no detectible input from S-cones. Where present, input from S-cones tended to provide weak inhibition to PC cells. All cell types showed evidence of a suppressive extra-classical receptive field driven largely or exclusively by ML-cones. These data indicate that S-cone signals are isolated to supply the classical receptive field mechanisms of blue-on and blue-off cells in the LGN, and that the low spatial precision of S-cone vision has origins in both classical and extraclassical receptive field properties of subcortical pathways.
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Affiliation(s)
- C Tailby
- National Vision Research Institute of Australia, Corner of Keppel and Cardigan Streets, Carlton, Victoria 3053, Australia
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Rees G, Martin PR, Macrae FA. Screening participation in individuals with a family history of colorectal cancer: a review. Eur J Cancer Care (Engl) 2008; 17:221-32. [PMID: 18419625 DOI: 10.1111/j.1365-2354.2007.00834.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Literature regarding screening behaviour in individuals with a family history of colorectal cancer was reviewed, in order to determine the prevalence of screening in this population and identify factors associated with screening participation. Four electronic databases were searched from 1994. Thirty papers met the inclusion criteria, including 3 community surveys, 13 studies on first-degree relatives of colorectal cancer patients, and 14 studies on genetic services for colorectal cancer risk assessment. Individuals with a family history of colorectal cancer, who have not received risk assessment, frequently have never had any form of screening for colorectal cancer. Uptake of endoscopic screening when offered to individuals identified as being at increased risk was generally high (often >60% participation). Having a medical recommendation to screen, a stronger family history and perceiving fewer barriers to screening were identified as predictors of screening behaviour. Existing data suggest that use of screening tests in individuals with a family history of colorectal cancer is variable, and our understanding of factors associated with screening behaviour is limited. A number of methodological problems in research to date were identified, and further research is needed in order to inform interventions to support sustained screening participation in this population.
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Affiliation(s)
- G Rees
- Centre for Eye Research Australia, University of Melbourne, Victoria, Australia.
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Martin PR, Berdychevski RE, Subramanian U, Blakely WF, Prasanna PGS. Sample Tracking in an Automated Cytogenetic Biodosimetry Laboratory for Radiation Mass Casualties. RADIAT MEAS 2007; 42:1119-1124. [PMID: 18037985 DOI: 10.1016/j.radmeas.2007.05.021] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Chromosome aberration-based dicentric assay is expected to be used after mass casualty life-threatening radiation exposures to assess radiation dose to individuals. This will require processing of a large number of samples for individual dose assessment and clinical triage to aid treatment decisions. We have established an automated, high-throughput, cytogenetic biodosimetry laboratory to process a large number of samples for conducting the dicentric assay using peripheral blood from exposed individuals according to internationally accepted laboratory protocols (i.e., within days following radiation exposures). The components of an automated cytogenetic biodosimetry laboratory include blood collection kits for sample shipment, a cell viability analyzer, a robotic liquid handler, an automated metaphase harvester, a metaphase spreader, high-throughput slide stainer and coverslipper, a high-throughput metaphase finder, multiple satellite chromosome-aberration analysis systems, and a computerized sample tracking system. Laboratory automation using commercially available, off-the-shelf technologies, customized technology integration, and implementation of a laboratory information management system (LIMS) for cytogenetic analysis will significantly increase throughput.This paper focuses on our efforts to eliminate data transcription errors, increase efficiency, and maintain samples' positive chain-of-custody by sample tracking during sample processing and data analysis. This sample tracking system represents a "beta" version, which can be modeled elsewhere in a cytogenetic biodosimetry laboratory, and includes a customized LIMS with a central server, personal computer workstations, barcode printers, fixed station and wireless hand-held devices to scan barcodes at various critical steps, and data transmission over a private intra-laboratory computer network. Our studies will improve diagnostic biodosimetry response, aid confirmation of clinical triage, and medical management of radiation exposed individuals.
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Affiliation(s)
- P R Martin
- Uniformed Services University of Health Sciences, Armed Forces Radiobiology Research Institute, 8901 Wisconsin Avenue. Bethesda, MD 20889-5603, USA
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Abstract
The increase in diversity towards the equator arises from latitudinal variation in rates of cladogenesis, extinction, immigration and/or emigration of taxa. We tested the relative contribution of all four processes to the latitudinal gradient in 26 marine invertebrate orders with extensive fossil records, examined previously by David Jablonski. Coupling Jablonski's estimates of latitudinal variation in cladogenesis with new data on patterns of extinction and current distributions, we show that the present-day gradient in diversity is caused by higher rates of cladogenesis and subsequent range expansion (immigration) at lower latitudes. In contrast, extinction and emigration were not important in the creation of the latitudinal gradient in ordinal richness. This work represents one of the first simultaneous tests of the role of all four processes in the creation of the latitudinal gradient in taxonomic richness, and suggests that low tropical extinction rates are not essential to the creation of latitudinal diversity gradients.
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Affiliation(s)
- P R Martin
- Department of Biology, University of Washington, Seattle, WA, USA.
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Abstract
This study concerns the properties of neurons carrying signals for colour vision in primates. We investigated the variability of responses of individual parvocellular lateral geniculate neurons of dichromatic and trichromatic marmosets to drifting sinusoidal luminance and chromatic gratings. Response variability was quantified by the cycle-to-cycle variation in Fourier components of the response. Averaged across the population, the variability at low contrasts was greater than predicted by a Poisson process, and at high contrasts the responses were approximately 40% more variable than responses at low contrasts. The contrast-dependent increase in variability was nevertheless below that expected from the increase in firing rate. Variability falls below the Poisson prediction at high contrast, and intrinsic variability of the spike train decreases as contrast increases. Thus, while deeply modulated responses in parvocellular cells have a larger absolute variability than weakly modulated ones, they have a more favourable signal: noise ratio than predicted by a Poisson process. Similar results were obtained from a small sample of magnocellular and koniocellular ('blue-on') neurons. For parvocellular neurons with pronounced colour opponency, chromatic responses were, on average, less variable (10-15%, p<0.01) than luminance responses of equal magnitude. Conversely, non-opponent parvocellular neurons showed the opposite tendency. This is consistent with a supra-additive noise source prior to combination of cone signals. In summary, though variability of parvocellular neurons is largely independent of the way in which they combine cone signals, the noise characteristics of retinal circuitry may augment specialization of parvocellular neurons to signal luminance or chromatic contrast.
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Affiliation(s)
- J D Victor
- Department of Neurology and Neuroscience, Weill Medical College of Cornell University, New York, NY 10021, USA
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Chan TL, Martin PR, Clunas N, Grünert U. Bipolar cell diversity in the primate retina: morphologic and immunocytochemical analysis of a new world monkey, the marmoset Callithrix jacchus. J Comp Neurol 2001; 437:219-39. [PMID: 11494253 DOI: 10.1002/cne.1280] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The aim of this study was to identify the bipolar cell types in the retina of a New World monkey, the common marmoset, and compare them with those found in the Old World macaque monkey. Retinal whole-mounts, sections, or both, were stained by using DiI labeling and immunohistochemical methods. Semithin sections were analyzed by using quantitative methods. We show that the same morphologic types of bipolar cell as described for the Old World macaque monkey by Boycott and Wässle (Boycott and Wässle [1991] Eur. J. Neurosci. 3:1069-1088) are present in marmoset retina: two types of midget bipolar cells, six type of diffuse bipolar cells, a blue cone bipolar cell, and one type of rod bipolar cell. The pattern of staining with different immunohistochemical markers ("fingerprint") of each bipolar cell type in marmoset was also the same as described for macaque, with one exception: the flat midget bipolar cell (FMB) class is labeled by antibodies to recoverin in macaque but is labeled by antibodies to CD15 in marmoset. The labeled FMB cells in marmoset make contact with multiple cone photoreceptors throughout most of the extrafoveal retina. The spatial density of bipolar cells in marmoset is shown to be sufficient to support one-to-one connectivity of midget bipolar and ganglion cells in the fovea and to allow for parallel pathways to ganglion cells throughout the retina. Quantitative differences in the morphology and receptor connectivity between marmoset and macaque can be related to differences in cone and rod photoreceptor density between the species. We conclude that bipolar cell diversity is a preserved feature of the primate retina.
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Affiliation(s)
- T L Chan
- Department of Physiology F13, Institute for Biomedical Research, The University of Sydney, Sydney 2006, Australia
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White AJ, Solomon SG, Martin PR. Spatial properties of koniocellular cells in the lateral geniculate nucleus of the marmoset Callithrix jacchus. J Physiol 2001; 533:519-35. [PMID: 11389209 PMCID: PMC2278639 DOI: 10.1111/j.1469-7793.2001.0519a.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.3] [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: 10/18/2000] [Accepted: 01/25/2001] [Indexed: 11/30/2022] Open
Abstract
1. The receptive field dimensions, contrast sensitivity and linearity of spatial summation of koniocellular (KC), parvocellular (PC) and magnocellular (MC) cells in the lateral geniculate nucleus (LGN) of 11 adult marmosets were measured using achromatic sinusoidal gratings. 2. The receptive field centre diameter of cells in each (PC, KC and MC) class increases with distance from the fovea. There is substantial overlap in centre size between the three cell classes at any eccentricity, but the PC cells have, on average, the smallest centres and the KC cells have the largest. Some PC and KC cells did not respond at all to the grating stimulus. 3. The contrast sensitivity of the receptive field centre mechanism in KC cells decreases in proportion to the centre area. A similar trend was seen for the surround mechanism. These characteristics are common to PC and MC cells, suggesting that they originate at an early stage of visual processing in the retina. 4. The KC cells showed, in general, lower peak evoked discharge rates than PC or MC cells. The spontaneous discharge rate of KC cells was lower than that of PC cells and similar to that of MC cells. 5. The majority of cells in all divisions of the LGN show linear spatial summation. A few cells did show non-linear spatial summation; these cells were predominantly located in the MC and ventral KC layers. 6. The ventral KC layers below and between the MC layers contain cells with larger and more transiently responding receptive fields than cells in the more dorsal KC layers. 7. We conclude that many of the contrast-dependent spatial properties of cells in the marmoset LGN are common to PC, MC and KC cells. The main difference between KC cells and the other two classes is that there is more variability in their response properties, and they are less responsive to high spatial frequencies.
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Affiliation(s)
- A J White
- Department of Physiology and Institute for Biomedical Research, University of Sydney, NSW 2006, Australia
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Abstract
This study tested two contrasting theories of how trigger factors acquire the capacity to precipitate headaches. The sample consisted of 110 participants, of whom 48 suffered from regular headaches. Participants were exposed to a validated headache trigger factor for one of five exposure durations. The trigger used was "visual disturbance" (flicker, glare and eyestrain) induced by a very bright, stroboscopic light. Response to the stimulus was measured by participant ratings of the degree of visual disturbance and head pain caused by the stimulus. As expected, the headache sufferers experienced more visual disturbance and head pain in response to the stimulus than the non-headache individuals. Longer exposure to the stimulus was associated with a subsequent reduction in pain ratings in response to the stimulus. This desensitization effect supported an avoidance model of how trigger factors acquire the capacity to precipitate headaches. The findings of this study have implications for the etiology of headache disorders. Also, the findings imply that the traditional clinical advice that the best way to prevent migraine and headache is to avoid the factors that trigger them, may be counterproductive, as any short-term gains may be more than wiped out by decreased tolerance for the trigger factors.
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Affiliation(s)
- P R Martin
- School of Psychology, University of New England, Armidale, NSW, Australia.
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Abstract
Thiamine is required for all tissues and is found in high concentrations in skeletal muscle, heart, liver, kidneys and brain. A state of severe depletion is seen in patients on a strict thiamine-deficient diet in 18 days, but the most common cause of thiamine deficiency in affluent countries is alcoholism. Thiamine diphosphate is the active form of thiamine, and it serves as a cofactor for several enzymes involved primarily in carbohydrate catabolism. The enzymes are important in the biosynthesis of a number of cell constituents, including neurotransmitters, and for the production of reducing equivalents used in oxidant stress defenses and in biosyntheses and for synthesis of pentoses used as nucleic acid precursors. Because of the latter fact, thiamine utilization is increased in tumor cells. Thiamine uptake by the small intestines and by cells within various organs is mediated by a saturable, high affinity transport system. Alcohol affects thiamine uptake and other aspects of thiamine utilization, and these effects may contribute to the prevalence of thiamine deficiency in alcoholics. The major manifestations of thiamine deficiency in humans involve the cardiovascular (wet beriberi) and nervous (dry beriberi, or neuropathy and/or Wernicke-Korsakoff syndrome) systems. A number of inborn errors of metabolism have been described in which clinical improvements can be documented following administration of pharmacological doses of thiamine, such as thiamine-responsive megaloblastic anemia. Substantial efforts are being made to understand the genetic and biochemical determinants of inter-individual differences in susceptibility to development of thiamine deficiency-related disorders and of the differential vulnerabilities of tissues and cell types to thiamine deficiency.
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Affiliation(s)
- C K Singleton
- Department of Biological Science, Vanderbilt University, Nashville, TN 37235, USA.
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Abstract
Visual abilities change over the visual field. For example, our ability to detect movement is better in peripheral vision than in foveal vision, but colour discrimination is markedly worse. The deterioration of colour vision has been attributed to reduced colour specificity in cells of the midget, parvocellular (PC) visual pathway in the peripheral retina. We have measured the colour specificity (red-green chromatic modulation sensitivity) of PC cells at eccentricities between 20 and 50 degrees in the macaque retina. Here we show that most peripheral PC cells have red-green modulation sensitivity close to that of foveal PC cells. This result is incompatible with the view that PC pathway cells in peripheral retina make indiscriminate connections ('random wiring') with retinal circuits devoted to different spectral types of cone photoreceptors. We show that selective cone connections can be maintained by dendritic field anisotropy, consistent with the morphology of PC cell dendritic fields in peripheral retina. Our results also imply that postretinal mechanisms contribute to the psychophysically demonstrated deterioration of colour discrimination in the peripheral visual field.
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Affiliation(s)
- P R Martin
- Department of Physiology and Institute for Biomedical Research, University of Sydney, NSW 2006, Australia.
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Abstract
The distribution and morphology of CD15-immunoreactive bipolar cells were studied in the retina of macaque monkey. Labelled cells have a large dendritic tree contacting several cones and a narrowly stratified axon terminal that ends deep in the inner plexiform layer, close to the ganglion cell layer. The morphology of the labelled cells corresponds to that of the diffuse bipolar cell type named DB6 by Boycott & Wässle (1991; Eur. J. Neurosci., 3,1069). We conclude that CD15 is a marker for DB6 bipolar cells, enabling the quantitative analysis of the distribution and connectivity of this diffuse bipolar cell type.
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Affiliation(s)
- T L Chan
- Department of Physiology and Institute for Biomedical Research, The University of Sydney, NSW 2006, Australia
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21
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Abstract
Members of the family Pasteurellaceae are classified in part by whether or not they require an NAD supplement for growth on laboratory media. In this study, we demonstrate that this phenotype can be determined by a single gene, nadV, whose presence allows NAD-independent growth of Haemophilus influenzae and Actinobacillus pleuropneumoniae. This gene was cloned from a 5.2-kb plasmid which was previously shown to be responsible for NAD independence in Haemophilus ducreyi. When transformed into A. pleuropneumoniae, this cloned gene allowed NAD-independent growth on complex media and allowed the utilization of nicotinamide in place of NAD on defined media. Sequence analysis revealed an open reading frame of 1,482 bp that is predicted to encode a protein with a molecular mass of 55,619 Da. Compared with the sequence databases, NadV was found to have significant sequence homology to the human pre-B-cell colony-enhancing factor PBEF and to predicted proteins of unknown function identified in the bacterial species Mycoplasma genitalium, Mycoplasma pneumoniae, Shewanella putrefaciens, Synechocystis sp., Deinococcus radiodurans, Pasteurella multocida, and Actinobacillus actinomycetemcomitans. P. multocida and A. actinomycetemcomitans are among the NAD-independent members of the Pasteurellaceae. Homologues of NadV were not found in the sequenced genome of H. influenzae, an NAD-dependent member of the Pasteurellaceae, or in species known to utilize a different pathway for synthesis of NAD, such as Escherichia coli. Sequence alignment of these nine homologues revealed regions and residues of complete conservation that may be directly involved in the enzymatic activity. Identification of a function for this gene in the Pasteurellaceae should help to elucidate the role of its homologues in other species.
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Affiliation(s)
- P R Martin
- Department of Microbiology, Michigan State University, East Lansing, Michigan 48824-1101, USA
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22
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Encalada SE, Martin PR, Phillips JB, Lyczak R, Hamill DR, Swan KA, Bowerman B. DNA replication defects delay cell division and disrupt cell polarity in early Caenorhabditis elegans embryos. Dev Biol 2000; 228:225-38. [PMID: 11112326 DOI: 10.1006/dbio.2000.9965] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [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: 11/22/2022]
Abstract
In early Caenorhabditis elegans embryos, asymmetric cell divisions produce descendants with asynchronous cell cycle times. To investigate the relationship between cell cycle regulation and pattern formation, we have identified a collection of embryonic-lethal mutants in which cell divisions are delayed and cell fate patterns are abnormal. In div (for division delayed) mutant embryos, embryonic cell divisions are delayed but remain asynchronous. Some div mutants produce well-differentiated cell types, but they frequently lack the endodermal and mesodermal cell fates normally specified by a transcriptional activator called SKN-1. We show that mislocalization of PIE-1, a negative regulator of SKN-1, prevents the specification of endoderm and mesoderm in div-1 mutant embryos. In addition to defects in the normally asymmetric distribution of PIE-1, div mutants also exhibit other losses of asymmetry during early embryonic cleavages. The daughters of normally asymmetric divisions are nearly equal in size, and cytoplasmic P-granules are not properly localized to germline precursors in div mutant embryos. Thus the proper timing of cell division appears to be important for multiple aspects of asymmetric cell division. One div gene, div-1, encodes the B subunit of the DNA polymerase alpha-primase complex. Reducing the function of other DNA replication genes also results in a delayed division phenotype and embryonic lethality. Thus the other div genes we have identified are likely to encode additional components of the DNA replication machinery in C. elegans.
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Affiliation(s)
- S E Encalada
- Institute of Molecular Biology and Department of Biology, University of Oregon, 1370 Franklin Boulevard, Eugene, Oregon 97403, USA
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24
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Lin B, Martin PR, Solomon SG, Grünert U. Distribution of glycine receptor subunits on primate retinal ganglion cells: a quantitative analysis. Eur J Neurosci 2000; 12:4155-70. [PMID: 11122328] [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] [Indexed: 02/18/2023]
Abstract
This study investigates the distribution of inhibitory neurotransmitter receptors on sensory neurons. Ganglion cells in the retina of a New World monkey, the common marmoset Callithrix jacchus, were injected with Lucifer yellow and Neurobiotin and subsequently processed with antibodies against one (alpha1), or against all subunits, of the glycine receptor, or against the anchoring protein gephyrin. Immunoreactive (IR) puncta representing glycine receptor or gephyrin clusters were found on the proximal and the distal dendrites of all ganglion cell types investigated. For both parasol and midget cells, the density of receptor clusters was greater on distal than proximal dendrites for all antibodies tested. In parasol cells the average density for the alpha1 subunit of the glycine receptor was 0.087 IR puncta/microm of dendrite, and for all subunits it was 0.119 IR puncta/microm of dendrite. Thus, the majority of glycine receptors on parasol cells contain the alpha1 subunit. For parasol cells, we estimated an average of 1.5 glycinergic synapses/100 microm2 dendritic membrane on proximal dendrites and about 9.4 glycinergic synapses/100 microm2 on distal dendrites. The segregation of receptors to the distal dendrites appears to be a common feature of inhibitory neurotransmitter input to parasol and midget cells, and might be associated with the receptive field surround mechanism.
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Affiliation(s)
- B Lin
- Department of Physiology F13 and Institute for Biomedical Research, The University of Sydney, NSW 2006, Australia
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25
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Lee BB, Silveira LC, Yamada ES, Hunt DM, Kremers J, Martin PR, Troy JB, da Silva-Filho M. Visual responses of ganglion cells of a New-World primate, the capuchin monkey, Cebus apella. J Physiol 2000; 528:573-90. [PMID: 11432364 PMCID: PMC2270155 DOI: 10.1111/j.1469-7793.2000.00573.x] [Citation(s) in RCA: 32] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
1. The genetic basis of colour vision in New-World primates differs from that in humans and other Old-World primates. Most New-World primate species show a polymorphism; all males are dichromats and most females trichromats. 2. In the retina of Old-World primates such as the macaque, the physiological correlates of trichromacy are well established. Comparison of the retinae in New- and Old-World species may help constrain hypotheses as to the evolution of colour vision and the pathways associated with it. 3. Ganglion cell behaviour was recorded from trichromatic and dichromatic members of a New-World species (the capuchin monkey, Cebus apella) and compared with macaque data. Despite some differences in quantitative detail (such as a temporal response extended to higher frequencies), results from trichromatic animals strongly resembled those from the macaque. 4. In particular, cells of the parvocellular (PC) pathway showed characteristic frequency-dependent changes in responsivity to luminance and chromatic modulation, cells of the magnocellular (MC) pathway showed frequency-doubled responses to chromatic modulation, and the surround of MC cells received a chromatic input revealed on changing the phase of heterochromatically modulated lights. 5. Ganglion cells of dichromats were colour-blind versions of those of trichromats. 6. This strong physiological homology is consistent with a common origin of trichromacy in New- and Old-World monkeys; in the New-World primate the presence of two pigments in the middle-to-long wavelength range permits full expression of the retinal mechanisms of trichromatic vision.
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Affiliation(s)
- B B Lee
- Neurobiology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
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26
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Macri J, Martin PR, Grünert U. Distribution of the alpha1 subunit of the GABA(A) receptor on midget and parasol ganglion cells in the retina of the common marmoset Callithrix jacchus. Vis Neurosci 2000; 17:437-48. [PMID: 10910110 DOI: 10.1017/s0952523800173109] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [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: 11/07/2022]
Abstract
The inhibitory neurotransmitter gamma aminobutyric acid (GABA) has been shown to influence the responses of ganglion cells in the mammalian retina. Consistently, GABA(A) receptor subunits have been localized to different ganglion cell types. In this study, the distribution of the alpha1 subunit of the GABA(A) receptor on the dendrites of midget and parasol ganglion cells was investigated quantitatively in the retina of a New World monkey, the marmoset. Ganglion cells were injected with Neurobiotin in a live in vitro retinal whole-mount preparation. Retinal pieces were then processed with an antibody against the alpha1 subunit of the GABA(A) receptor. Strong punctate immunoreactivity indicative of synaptic localization is present in the ON and OFF sublamina of the inner plexiform layer. Many of the immunoreactive puncta coincide with the dendrites of both midget and parasol ganglion cells. Immunoreactive puncta are present on distal and proximal dendrites of ON and OFF cells of both ganglion cell types. On average, parasol cells show a slight increase in the spatial density of immunoreactive puncta with distance from the soma, whereas the density of immunoreactive puncta on midget cells stays even. Parasol ganglion cells show a slightly higher average density of immunoreactive puncta (0.083 puncta/microm dendrite) than midget cells (0.054 puncta/microm dendrite).
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Affiliation(s)
- J Macri
- Department of Physiology and Institute for Biomedical Research, The University of Sydney, NSW, Australia
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27
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Martin PR, Grünert U, Chan TL, Bumsted K. Spatial order in short-wavelength-sensitive cone photoreceptors: a comparative study of the primate retina. J Opt Soc Am A Opt Image Sci Vis 2000; 17:557-567. [PMID: 10708037 DOI: 10.1364/josaa.17.000557] [Citation(s) in RCA: 25] [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] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We compared the spatial distribution of short-wavelength-sensitive (SWS or blue) cone photoreceptors in the retinas of eight primate species. The regularity of the SWS cone array was quantified with a statistic (packing factor) that varies between a random distribution (0) and a triangular array (1). We find wide variability among species, with packing factors varying between 0.06 and 0.3. The SWS cone array in at least two New World monkey species is indistinguishable from a random array. The SWS cone density gradient across the retina was measured in the capuchin monkey Cebus apella and the squirrel monkey Saimiri sciureus. Both species show a peak density of 5,000-8,000 cells/mm2 at the fovea and a 50-fold central-peripheral density gradient. In contrast to the wide variation in local regularity, the spatial density and the topography of SWS cones are well preserved across primates.
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Affiliation(s)
- P R Martin
- Department of Physiology and Institute for Biomedical Research, University of Sydney, NSW, Australia.
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28
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Abstract
The evolutionary causes of small clutch sizes in tropical and Southern Hemisphere regions are poorly understood. Alexander Skutch proposed 50 years ago that higher nest predation in the south constrains the rate at which parent birds can deliver food to young and thereby constrains clutch size by limiting the number of young that parents can feed. This hypothesis for explaining differences in clutch size and parental behaviors between latitudes has remained untested. Here, a detailed study of bird species in Arizona and Argentina shows that Skutch's hypothesis explains clutch size variation within North and South America. However, neither Skutch's hypothesis nor two major alternatives explain differences between latitudes.
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Affiliation(s)
- T E Martin
- U.S. Geological Survey Biological Resources Division, Missoula, MT 59812, USA.
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29
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Abstract
A fate map has been constructed for the shoot apical region of the embryo of the dicotyledonous plant Arabidopsis thaliana using spontaneously arising clonal albino sectors caused by the chloroplast mutator 1–2 mutation. Chimeric seedlings exhibiting albino sectors shared between the cotyledons and first true leaves revealed patterns of organ inclusion and exclusion. Frequencies of clone sharing were used to calculate developmental distances between organs based on the frequency of clonal sectors failing to extend between different organs. The resulting fate map shows asymmetry in the developmental distances between the cotyledons (embryonic leaves) which in turn predicts the location of the first post-germination leaf and the handedness of the spiral of leaf placement around the central stem axis in later development. The map suggests that embryonic leaf fate specification in the cotyledons may represent a developmental ground state necessary for the formation of the shoot apical meristem.
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Affiliation(s)
- R Woodrick
- Department of Biology, Loyola University of Chicago, Chicago, IL 60626, USA
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30
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Abstract
This study sought to experimentally validate two reported precipitants of chronic headaches, namely, negative affect (anxiety, anger, depression) and visual disturbance (flicker, glare, eyestrain), and to investigate whether they triggered common or different physiological mechanisms. Twenty-two male and 68 female subjects (46 with migraine, 29 with tension-type headache, and 15 controls) were submitted to antecedent challenges in the laboratory which induced negative affect or visual disturbance and to a control challenge. The results demonstrated that negative affect and visual disturbance can indeed precipitate headaches, and that the physiological responses associated with these antecedents differ, but the findings were not conclusive as to whether one or more physiological mechanisms are operative. Follow-up revealed that the antecedent challenges had significant effects on headache activity 48 to 72 hours after termination.
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Affiliation(s)
- P R Martin
- School of Psychology, University of New England, Armidale, NSW 2351, Australia
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31
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Hartmann SL, Parks MH, Martin PR, Dawant BM. Automatic 3-D segmentation of internal structures of the head in MR images using a combination of similarity and free-form transformations: Part II, validation on severely atrophied brains. IEEE Trans Med Imaging 1999; 18:917-926. [PMID: 10628951 DOI: 10.1109/42.811273] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Studies aimed at quantifying neuroanatomical differences between populations require the volume measurements of individual brain structures. If the study contains a large number of images, manual segmentation is not practical. This study tests the hypothesis that a fully automatic, atlas-based segmentation method can be used to quantify atrophy indexes derived from the brain and cerebellum volumes in normal subjects and chronic alcoholics. This is accomplished by registering an atlas volume with a subject volume, first using a global transformation, and then improving the registration using a local transformation. Segmented structures in the atlas volume are then mapped to the corresponding structures in the subject volume using the combined global and local transformations. This technique has been applied to seven normal and seven alcoholic subjects. Three magnetic resonance volumes were obtained for each subject and each volume was segmented automatically, using the atlas-based method. Accuracy was assessed by manually segmenting regions and measuring the similarity between corresponding regions obtained automatically. Repeatability was determined by comparing volume measurements of segmented structures from each acquisition of the same subject. Results demonstrate that the method is accurate, that the results are repeatable, and that it can provide a method for automatic quantification of brain atrophy, even when the degree of atrophy is large.
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Affiliation(s)
- S L Hartmann
- Department of Biomedical Engineering, Vanderbilt University, Nashville TN 37235, USA
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32
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Martin PR, Mulks MH. Cloning and characterization of a gene encoding an antigenic membrane protein from Actinobacillus pleuropneumoniae with homology to ABC transporters. FEMS Immunol Med Microbiol 1999; 25:245-54. [PMID: 10459579 DOI: 10.1111/j.1574-695x.1999.tb01349.x] [Citation(s) in RCA: 10] [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: 11/28/2022]
Abstract
Actinobacillus pleuropneumoniae is a pathogenic bacterium responsible for a highly contagious and often fatal form of bronchopneumonia in swine. Survival from a natural infection generally results in immunity from further infection by all 12 common serotypes, suggesting the presence of common protective antigens. We have identified one of the antigenic membrane proteins from A. pleuropneumoniae serotype 5, and cloned the gene which encodes it. This gene is found in all 12 serotypes, and encodes a protein with a predicted molecular mass of 30 kDa. Sequence analysis revealed that this antigen has a typical signal sequence characteristic of lipoproteins, and is likely to be secreted and inserted into the periplasmic side of the inner membrane. The gene shows high homology to the surface antigen CjaA of Campylobacter jejuni and to solute binding proteins of the ABC transporter family. The probable role of this protein in substrate binding and transport was supported by the presence of an upstream gene with significant homology to ATP binding proteins of the same family. In Escherichia coli, the cloned gene produced a protein which reacted strongly with convalescent sera from swine infected with A. pleuropneumoniae serotype 5, and weakly with sera from swine infected with serotype 1A or from swine vaccinated with a killed bacterin of serotype 1A or 5. It thus appears that this antigen displays some crossreactivity between serotypes, and may be less exposed in bacterins than in live cells. This protein, designated ApaA, may have an important role in nutrient acquisition and in the pathogenesis of infections caused by A. pleuropneumoniae.
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Affiliation(s)
- P R Martin
- Department of Microbiology, Michigan State University, East Lansing 48824-1101, USA
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33
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Onaivi ES, Chaudhuri G, Abaci AS, Parker M, Manier DH, Martin PR, Hubbard JR. Expression of cannabinoid receptors and their gene transcripts in human blood cells. Prog Neuropsychopharmacol Biol Psychiatry 1999; 23:1063-77. [PMID: 10621950 DOI: 10.1016/s0278-5846(99)00052-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
1. This study shows that the human cannabinoid receptors and their gene transcripts can be analyzed in blood samples when combined with polymerase chain reaction. The results also demonstrate that the expression of the cannabinoid receptors is dependent on gender and ethnic background. 2. Normal human volunteers who do not use marijuana have genes that encode for the marijuana (cannabinoid) receptor proteins. 3. Primer pairs from CB1 and CB2 cDNA coding region sequences showed identical amplified DNA band sizes in both DNA-PCR and reverse PCR, with human templates. This suggests that the CB1 and CB2 genes are intronless at least in their coding regions. 4. An advantage of the coding region being intronless may be that the expression of these genes will have one major RNA processing event to skip, thus making the conditions of their expression relatively quick and simple. This advantage may have implications related to the biological functions of these proteins. 5. We therefore concluded that the existence of human cannabinoid receptors and genes along with the discovery of endogenous cannabinoids (endocannabinoids) may be useful markers in elucidating the role(s) and mechanism(s) of action of cannabinoids.
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Affiliation(s)
- E S Onaivi
- Department of Psychiatry, Vanderbilt University School of Medicine, Nashville, TN, USA.
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34
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Luo X, Ghosh KK, Martin PR, Grünert U. Analysis of two types of cone bipolar cells in the retina of a New World monkey, the marmoset, Callithrix jacchus. Vis Neurosci 1999; 16:707-19. [PMID: 10431919 DOI: 10.1017/s0952523899164101] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Two types of cone bipolar cells, the blue cone bipolar cell and the diffuse bipolar cell (DB3), were labelled immunohistochemically and investigated in the retina of a New World monkey, the marmoset. Blue cone bipolar cells were labelled with an antiserum against cholecystokinin. Short-wavelength-sensitive (SWS) cones were labelled with an antiserum against the SWS cone opsin. The DB3 cells were labelled with antibodies to calbindin. Blue cone bipolar cells in marmoset do not form a regular mosaic but instead follow the random distribution of the SWS cones. Nevertheless, the SWS cone to blue cone bipolar cell connectivity in marmoset is very similar to that previously described for macaque. In contrast to the blue cone bipolar cells, the DB3 cells form a regular mosaic. The synaptic connectivity of DB3 cells in the inner plexiform layer was analyzed. They make output synapses onto ganglion cells and amacrine cells, and gap junctions with each other. Our results provide further evidence for the existence of parallel bipolar cell pathways in the primate retina and support the view that the retinae of Old World and New World primates have common neuronal connectivity. The random distribution of SWS cones and blue cone bipolar cells is an exception to the general rule of a regular mosaic distribution of cell populations in the retina.
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Affiliation(s)
- X Luo
- Department of Physiology and Institute for Biomedical Research, The University of Sydney, NSW, Australia
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35
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Solomon SG, White AJ, Martin PR. Temporal contrast sensitivity in the lateral geniculate nucleus of a New World monkey, the marmoset Callithrix jacchus. J Physiol 1999; 517 ( Pt 3):907-17. [PMID: 10358129 PMCID: PMC2269368 DOI: 10.1111/j.1469-7793.1999.0907s.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [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] Open
Abstract
1. The temporal contrast sensitivity of koniocellular, parvocellular and magnocellular cells in the lateral geniculate nucleus (LGN) of nine adult marmosets was measured. The receptive fields of the cells were between 0.3 and 70 deg from the fovea. The stimulus was a large spatially uniform field which was modulated in luminance at temporal frequencies between 0.98 and 64 Hz. 2. For each cell group there was a gradual increase in modulation sensitivity, especially for temporal frequencies below 8 Hz, with increasing distance from the fovea. At any given eccentricity, magnocellular cells had the greatest sensitivity. In central visual field, the sensitivity of koniocellular cells lay between that of parvocellular and magnocellular cells. In peripheral visual field (above 10 deg eccentricity) koniocellular and parvocellular cells had similar sensitivity. 3. The contrast sensitivity of each cell class was dependent on the anaesthetic used. Cells from animals anaesthetized with isoflurane were less sensitive than cells from animals anaesthetized with sufentanil. This effect was more marked for temporal frequencies below 4 Hz. 4. These results are incompatible with the notion that the koniocellular pathway is functionally homologous to a sluggish, W-like pathway in other mammals. At least in terms of their temporal transfer properties, many koniocellular cells are more like parvocellular cells.
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Affiliation(s)
- S G Solomon
- Department of Physiology and Institute for Biomedical Research, University of Sydney, NSW 2006, Australia
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36
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Abstract
The distribution of short wavelength-sensitive (SWS or "blue") cone photoreceptors was compared in primates with dichromatic ("red-green colour blind") and trichromatic colour vision. We compared a New World species, the marmoset (Callithrix jacchus), with an Old World species, the macaque monkey (Macaca nemestrina). The SWS cones were identified by their immunoreactivity to an antiserum against the human SWS cone opsin. A single retina from a male capuchin monkey (Cebus apella) also was studied. The SWS cones make up less than 10% of all cone photoreceptors throughout the retina of all animals studied. In marmoset, the peak spatial density of SWS cones is close to 10,000/mm2 at the foveola. In macaque, the peak spatial density of SWS cones, close to 6,000/mm2, is at the fovea, but SWS cones are absent within 50 microm of the centre of the foveola. In both species, the density of SWS cones is higher on the nasal retinal axis than at corresponding eccentricities on the other retinal axes. The SWS cones in macaque are arranged in a semiregular array, but they are distributed randomly in marmoset. There is no difference in the spatial density or local arrangement of SWS cones between dichromatic and trichromatic marmosets. The results suggest that the SWS cone photoreceptor system is subject to different developmental and evolutionary constraints than those that have led to the formation of the red-green photoreceptor systems in primate vision.
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Affiliation(s)
- P R Martin
- Department of Physiology and Institute for Biomedical Research, The University of Sydney, New South Wales, Australia.
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37
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Silveira LC, Lee BB, Yamada ES, Kremers J, Hunt DM, Martin PR, Gomes FL. Ganglion cells of a short-wavelength-sensitive cone pathway in New World monkeys: morphology and physiology. Vis Neurosci 1999; 16:333-43. [PMID: 10367967 DOI: 10.1017/s0952523899162138] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [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: 11/06/2022]
Abstract
We have studied the morphology and physiology of retinal ganglion cells of a short-wavelength-sensitive cone (SWS-cone) pathway in dichromatic and trichromatic New World anthropoids, the capuchin monkey (Cebus apella) and tufted-ear marmoset (Callithrix jacchus). In Old World anthropoids, in which males and females are both trichromats, blue-ON/yellow-OFF retinal ganglion cells have excitatory SWS-cone and inhibitory middle- and long-wavelength-sensitive (MWS- and LWS-) cone inputs, and have been anatomically identified as small-field bistratified ganglion cells (SB-cells) (Dacey & Lee, 1994). Among retinal ganglion cells of New World monkeys, we find SB-cells which have very similar morphology to such cells in macaque and human; for example, the inner dendritic tree is larger and denser than the outer dendritic tree. We also find blue-on retinal ganglion cells of the capuchin to have physiological responses strongly resembling such cells of the macaque monkey retina; for example, responses were more sustained, with a gentler low frequency roll-off than MC-cells, and no evidence of contrast gain control. There was no difference between dichromatic and trichromatic individuals. The results support the view that SWS-cone pathways are similarly organized in New and Old World primates, consistent with the hypothesis that these pathways form a phylogenetically ancient color system.
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Affiliation(s)
- L C Silveira
- Departamento de Fisiologia, Universidade Federal do Pará, Belém, Brazil
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38
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Abstract
Colour vision in the majority of humans is trichromatic, relying on a comparison of the quantal absorption in three different types of cone photoreceptors. The first steps in this comparison process take place at an early level of the visual system, in the retina. This topical review will highlight recent experiments which have advanced our understanding of how cone signals are compared to generate cone-opponent responses in the primate retina.
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Affiliation(s)
- P R Martin
- Department of Physiology and Institute for Biomedical Research, University of Sydney, NSW 2006, Australia.
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39
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Abstract
Longitudinal magnetic resonance spectroscopy (MRS) studies require accurate repositioning of the volume of interest (VOI) over which measurements are made. In this work we present and evaluate a method for the image-guided repositioning of brain volumes of interest. The point-based registration technique we developed allows the repositioning to be performed on-line (i.e. while the patient is in the scanner). MR image volumes were acquired from six subjects, three scans each over the course of a month. During the first scan, two spectroscopy VOIs are visually selected: one in the frontal white matter, the other in the superior cerebellar vermis. The coordinates of 13 internal brain landmarks are also identified. During both subsequent scans, the same 13 landmarks are identified, and the transformation that registers the first set of landmarks to the subsequent set is computed. This result is used to automatically map the position of the spectroscopy VOIs from the first volume to the current volume. For the six subjects evaluated to date, we show an average repositioning error of the spectroscopy VOIs in the order of 1 mm. This accuracy allows us to conclude that any variations in the MR spectra are unlikely to be due to repositioning error.
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Affiliation(s)
- S L Hartmann
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37325, USA.
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40
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White AJ, Wilder HD, Goodchild AK, Sefton AJ, Martin PR. Segregation of receptive field properties in the lateral geniculate nucleus of a New-World monkey, the marmoset Callithrix jacchus. J Neurophysiol 1998; 80:2063-76. [PMID: 9772261 DOI: 10.1152/jn.1998.80.4.2063] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.2] [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: 11/22/2022] Open
Abstract
The lateral geniculate nucleus (LGN) in humans and Old-World monkeys is dominated by the representation of the fovea in the parvocellular (PC) layers, and most PC cells in the foveal representation have red-green cone opponent receptive field properties. It is not known whether these features are both unique to trichromatic primates. Here we measured receptive field properties and the visuotopic organization of cells in the LGN of a New-World monkey, the marmoset Callithrix jacchus. The marmoset displays a polymorphism of cone opsins in the medium-long wavelength (ML) range, which allows the LGN of dichromatic ("red-green color blind") and trichromatic individuals to be compared. Furthermore, the koniocellular-interlaminar layers are segregated from the main PC layers in marmoset, allowing the functional role of this subdivision of the LGN to be assessed. We show that the representation of the visual field in the LGN is quantitatively similar in dichromatic and trichromatic marmosets and is similar to that reported for macaque; the vast majority of LGN volume is devoted to the central visual field. ON- and OFF-type responses are partially segregated in the PC layers so that responses are more commonly encountered near the external border of each layer. The red-green (ML) opponent cells in trichromatic animals were all located in the PC layers, and their receptive fields were within 16 degrees of the fovea. The koniocellular zone between the PC and magnocellular layers contained cells that receive excitatory input from short wavelength sensitive cones ("blue- cells") as well as other nonopponent cells. These results suggest that the basic organization of the LGN is common to dichromatic and trichromatic primates and provide further evidence that ML and SWS opponent signals are carried in distinct subdivisions of the retinogeniculocortical pathway.
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Affiliation(s)
- A J White
- Department of Physiology and Institute for Biomedical Research, The University of Sydney, New South Wales 2006, Australia
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Swan KA, Severson AF, Carter JC, Martin PR, Schnabel H, Schnabel R, Bowerman B. cyk-1: a C. elegans FH gene required for a late step in embryonic cytokinesis. J Cell Sci 1998; 111 ( Pt 14):2017-27. [PMID: 9645949 DOI: 10.1242/jcs.111.14.2017] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.5] [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] Open
Abstract
A maternally expressed Caenorhabditis elegans gene called cyk-1 is required for polar body extrusion during meiosis and for a late step in cytokinesis during embryonic mitosis. Other microfilament- and microtubule-dependent processes appear normal in cyk-1 mutant embryos, indicating that cyk-1 regulates a specific subset of cytoskeletal functions. Because cytokinesis initiates normally and cleavage furrows ingress extensively in cyk-1 mutant embryos, we propose that the wild-type cyk-1 gene is required for a late step in cytokinesis. Cleavage furrows regress after completion of mitosis in cyk-1 mutants, leaving multiple nuclei in a single cell. Positional cloning and sequence analysis of the cyk-1 gene reveal that it encodes an FH protein, a newly defined family of proteins that appear to interact with the cytoskeleton during cytokinesis and in the regulation of cell polarity. Consistent with cyk-1 function being required for a late step in embryonic cytokinesis, we show that the CYK-1 protein co-localizes with actin microfilaments as a ring at the leading edge of the cleavage furrow, but only after extensive furrow ingression. We discuss our findings in the context of other studies suggesting that FH genes in yeast and insects function early in cytokinesis to assemble a cleavage furrow.
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Affiliation(s)
- K A Swan
- Institute of Molecular Biology, University of Oregon, Eugene, OR 97403, USA
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Goodchild AK, Martin PR. The distribution of calcium-binding proteins in the lateral geniculate nucleus and visual cortex of a New World monkey, the marmoset, Callithrix jacchus. Vis Neurosci 1998; 15:625-42. [PMID: 9682866 DOI: 10.1017/s0952523898154044] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.9] [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: 11/07/2022]
Abstract
Antibodies directed against the calcium-binding proteins, parvalbumin and calbindin, can be used to label distinct neuronal subgroups in the primate visual pathway. We analyzed parvalbumin immunoreactivity (P-IR) and calbindin immunoreactivity (C-IR) in the lateral geniculate nucleus (LGN) and visual cortex of the marmoset, Callithrix jacchus. We compared marmosets which were identified as having dichromatic or trichromatic color vision. Within the LGN, the density of P-IR neurones is highest in the parvocellular and magnocellular laminae, but C-IR neurones are found mainly in the koniocellular division of the LGN, that is, the interlaminar zones and S laminae. Not all interlaminar zone cells are C-IR. In the visual cortex, P-IR neurones are present in all laminae except lamina 1, in areas V1 and V2. Neurones which are strongly C-IR are mainly located in laminae 2 and 3 in V1 and V2. Lightly C-IR neurones are concentrated in lamina 4, and are more numerous in V1 than in V2. Quantitative analysis showed no differences in the density or distribution of IR neurones in either LGN or visual cortex when dichromat and trichromat animals were compared. We conclude that this functional difference is not associated with differences in the neurochemistry of calcium-binding proteins in the primary visual pathways.
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Affiliation(s)
- A K Goodchild
- Department of Physiology and Institute for Biomedical Research, University of Sydney, NSW, Australia
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Pekovich SR, Martin PR, Singleton CK. Thiamine deficiency decreases steady-state transketolase and pyruvate dehydrogenase but not alpha-ketoglutarate dehydrogenase mRNA levels in three human cell types. J Nutr 1998; 128:683-7. [PMID: 9521628 DOI: 10.1093/jn/128.4.683] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [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: 02/06/2023] Open
Abstract
Reductions in the levels and activities of enzymes that utilize thiamine diphosphate (ThDP) as a cofactor are thought to be responsible for the tissue damage suffered during thiamine deficiency. Although loss of cofactor can account in part for loss of enzyme activity, thiamine and its phosphorylated derivatives may also regulate the expression of the genes encoding these proteins. To examine this possibility, steady-state mRNA levels for three ThDP-dependent enzymes were measured in human fibroblasts, lymphoblasts and neuroblastoma cells cultured under conditions of thiamine sufficiency and deficiency. In all three cell types, the mRNA levels of transketolase and the E1beta subunit of pyruvate dehydrogenase complex were lower in thiamine-deficient cultures. In contrast, mRNA levels for a ThDP-binding subunit of alpha-ketoglutarate dehydrogenase, the E1 subunit did not differ. These results indicate that thiamine or a thiamine metabolite regulates the expression in humans of some, but not all, genes encoding ThDP-utilizing enzymes.
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Affiliation(s)
- S R Pekovich
- Department of Molecular Biology, Vanderbilt University, Nashville, TN 37235, USA
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MacDiarmid SA, Goodson TC, Holmes TM, Martin PR, Doyle RB. An assessment of the comprehension of the American Urological Association Symptom Index. J Urol 1998; 159:873-4. [PMID: 9474172] [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] [Indexed: 02/06/2023]
Abstract
PURPOSE We determine the reading grade level of the American Urological Association (AUA) symptom index, and assessed patient ability to read and understand the index using a standardized reading and IQ test. MATERIALS AND METHODS The reading grade level required to read and understand the AUA symptom index was determined using the Spache and Dale-Chall readability formulas. A total of 202 men a mean of 66.1 years old completed the AUA symptom index, Wonderlic personnel test and scholastic level examination, and revised Ohio literacy test. Patients were instructed to report any difficulty in reading or understanding the AUA symptom score. RESULTS According to the Spache and Dale-Chall readability formulas, the AUA symptom index requires a grade 6 reading level. Of the 202 patients 30 (14.9%) did not complete the symptom index due to an inability to read it (28, 13.9%) and poor comprehension (2, 1%). Tested mean IQ and reading grade level was 91.7 and 11, respectively. CONCLUSIONS A grade 6 reading level is required to read and understand the AUA symptom index. A significant percentage of patients cannot read the index and require assistance from others for its completion. This assistance may introduce significant interviewer bias, potentially altering study outcome.
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Affiliation(s)
- S A MacDiarmid
- Department of Urology, University of Arkansas College of Medicine, Little Rock, USA
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Abstract
This study sought to experimentally validate 2 self-reported trigger factors of headaches, namely negative affect (anxiety, depression, and anger) and hunger, and to investigate whether these triggers activated the same or different physiological mechanisms. Students (38 women and 18 men) who had suffered from frequent headaches (migraine or tension type) for 6 months or more were randomly assigned to 4 conditions, which involved manipulating hunger by means of 19 hr of food deprivation and negative affect by means of a stressor (difficult to solve anagrams). The findings were consistent with self-reports that hunger and negative affect can precipitate headaches in individuals who suffer from both migraine and tension-type headaches. The physiological responses to the experimental conditions differed, but the findings were not conclusive with respect to whether the trigger factors operated by means of a common biological pathway.
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Affiliation(s)
- P R Martin
- Department of Psychology, University of Western Australia, Perth, Australia
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Wang JJ, Martin PR, Singleton CK. Aspartate 155 of human transketolase is essential for thiamine diphosphate-magnesium binding, and cofactor binding is required for dimer formation. Biochim Biophys Acta 1997; 1341:165-72. [PMID: 9357955 DOI: 10.1016/s0167-4838(97)00067-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Active human transketolase is a homodimeric enzyme possessing two active sites, each with a non-covalently bound thiamine diphosphate and magnesium. Both subunits contribute residues at each site which are involved in cofactor binding and in catalysis. His-tagged transketolase, produced in E. coli, was similar to transketolase purified from human tissues with respect to Km apps for cofactor and substrates and with respect to cofactor-dependent hysteresis. Mutation of aspartate 155, corresponding to a conserved aspartate residue among thiamine diphosphate-binding proteins, resulted in an inactive protein which could not bind the cofactor-magnesium complex and which could not dimerize. The results are consistent with the suggestion that aspartate 155 is an important coordination site for magnesium. In support of this interpretation, binding of cofactor by wild type apo-transketolase required the presence of magnesium. Additionally, monomeric apo-his-transketolase required both magnesium and cofactor binding for dimer formation.
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Affiliation(s)
- J J Wang
- Department of Molecular Biology, Vanderbilt University, Nashville, TN 37235, USA
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Welch LW, Nimmerrichter A, Gilliland R, King DE, Martin PR. "Wineglass" confabulations among brain-damaged alcoholics on the Wechsler Memory Scale-Revised visual reproduction subtest. Cortex 1997; 33:543-51. [PMID: 9339334 DOI: 10.1016/s0010-9452(08)70235-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [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] [Indexed: 02/05/2023]
Abstract
Confabulation is a clinically well-documented accompaniment of selective types of memory impairment, especially in brain-damaged alcoholics. This study reports specific occurrences of visual confabulation consisting of spontaneous alterations of Card D of the Visual Reproduction subtest of the Wechsler Memory Scale-Revised. The resemblance of a wineglass was fashioned by a 90-degree rotation into a "bowl and stem", observed in six of 30 brain-damaged alcoholics. There were no such instances in 132 other patients, including alcoholic controls, those with Parkinson's Disease, temporal lobe epileptics (pre- or post-surgery), and those with neurotoxic exposure. When asked, the subjects who identified the figure as a wineglass or similar drinking instrument reported that they had drawn it as originally shown to them. "Wineglass" confabulators had shorter periods of abstinence, longer drinking histories and lower intellectual functioning than their brain-damaged peers or an alcoholic control group. These findings lend support for the association of alcohol-related confabulation with visual, as well as previously-documented verbal material among brain-damaged alcoholics.
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Affiliation(s)
- L W Welch
- Vanderbilt University Medical Center, Dept. of Psychiatry, USA
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Abstract
This study sought to experimentally validate 2 self-reported trigger factors of headaches, namely negative affect (anxiety, depression, and anger) and hunger, and to investigate whether these triggers activated the same or different physiological mechanisms. Students (38 women and 18 men) who had suffered from frequent headaches (migraine or tension type) for 6 months or more were randomly assigned to 4 conditions, which involved manipulating hunger by means of 19 hr of food deprivation and negative affect by means of a stressor (difficult to solve anagrams). The findings were consistent with self-reports that hunger and negative affect can precipitate headaches in individuals who suffer from both migraine and tension-type headaches. The physiological responses to the experimental conditions differed, but the findings were not conclusive with respect to whether the trigger factors operated by means of a common biological pathway.
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Affiliation(s)
- P R Martin
- Department of Psychology, University of Western Australia, Perth, Australia
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Abstract
Colour vision in primates is mediated by cone opponent ganglion cells in the retina, whose axons project to the dorsal lateral geniculate nucleus in the visual thalamus. It has long been assumed that cone opponent ganglion cells project to the parvocellular layers of the geniculate. Here, we examine the role of a third subdivision of the geniculocortical pathway: the interlaminar or koniocellular geniculate relay cells. We made extracellular recordings in the dorsal lateral geniculate nucleus of the common marmoset Callithrix jacchus, a New World monkey in which the interlaminar cells are well segregated from the parvocellular layers. We found that one group of colour opponent cells, the blue-on cells, was largely segregated to the interlaminar zone. This segregation was common to dichromatic ('red-green colour-blind') and trichromatic marmosets. The result calls into question the traditional notion that all colour information passes through the parvocellular division of the retino-geniculo-cortical pathway in primates.
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Affiliation(s)
- P R Martin
- Department of Physiology and Institute for Biomedical Research, University of Sydney, NSW, Australia
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Abstract
The influence of breeding habitat on the evolution of song structure was examined in four wood warbler species of the sub-family Parulinae. The effects of song degradation on the ability of territorial paruline males to estimate distance by means of acoustic cues was also investigated. Song transmission characteristics of paruline breeding habitats were compared in southeastern Ontario, Canada; songs native to the habitat in which they were broadcast did not degrade less than foreign songs. The response of territorial paruline males to playback of 'near' (undegraded) and 'far' (degraded) conspecific songs broadcast from the same position within the territory at the same amplitude were then compared. Males responded to near songs as they would to a conspecific territorial intruder and with less intensity to far songs, suggesting that males may use cues from song degradation to estimate distance to vocal conspecifics. Our results from transmission and playback experiments are discussed with respect to the ranging hypothesis, which proposes that selection should favour males that structure songs to minimize their degradation, so that songs function to disrupt or intimidate rivals by providing unreliable distance cues.
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