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Biomedical subjects

M Barg

Publications and source records attributed to M Barg.

10 recordsLinked to original sources
PubMed2001

Patterns of carpal development among anuran amphibians.

The unity and diversity of developmental processes in the vertebrate limb have singular importance in the interpretation of evolutionary hypotheses of tetrapod diversification. In anurans, the intraordinal diversity of forelimbs seems to be related to the fusion of distal carpals, whereas proximal carpals are invariable. However, there are different ontogenetic pathways involved in the differentiation of proximal carpals. This study presents a comparative analysis of early developmental features in one archeobatrachian and 23 neobatrachian species representing five families and explores the variability in the differentiation of carpal cartilages. We found new evidence supporting the presence of an embryonic intermedium that incorporates with the ulnare. Difference between the pipid Xenopus and the neobatrachians is interpreted as a change in the rate of differentiation of Distal Carpal 5 that does not affect the developmental pattern of digits. The developmental variability exhibited by the intermedium, radiale, and Element Y is combined in patterns that converge on the same adult carpal morphology among neobatrachians; these patterns appear to contain potentially useful phylogenetic information.

Animals↗
PubMed1981

Down's syndrome: percentage reporting on birth certificates and single year maternal age risk rates for Ohio 1970-79: comparison with upstate New York data.

Estimates of single year maternal age risk rates for Down's Syndrome births to White residents of Ohio over the period 1970-79 are reported. The rates were estimated from birth certificate data, which first necessitated estimating the percentage of reporting of Down's Syndrome on Ohio birth certificates. Using data from cytogenetic laboratories within the state, percentages of Down's Syndrome cases reported were found to be 36.5 (319/875) for White and 33.9 (342/1,010) overall. Final single year maternal age risk rates reported here are corrected for underreporting using these figures. They should be useful for genetic counselors and obstetricians. Comparisons of observed, uncorrected single year maternal incidence rates were made within Ohio 1970-74 vs 1975-79, and between Ohio and upstate New York for various time periods using both a hierarchial log-linear model for multiway cross-tabulations and a weighted least squares solution. All comparisons showed excellent agreement, indicating no evidence for temporal or geographic differences and implying that environmental factors are unimportant in determining single year maternal age incidence rates in Down's Syndrome for the time periods and populations studied.

Adolescent↗
PubMed1978

Haemopoietic stem cells in the foetal mouse thymus.

The presence of haemopoietic stem cells (HSC) in the foetal mouse thymus was assessed to determine whether all cells which enter the developing organ are precommitted to thymocyte differentiation, or if stem cell multipotentiality still exists. The Till and McCulloch spleen colony assay was used to delineate foetal-thymus derived HSC in lethally irradiated recipients. Of the range examined, between 13 days of gestation to birth, a peak of stem cell activity occurs in 15-day foetal thymus. The surface colonies produced by the thymus-derived HSC are small compared to colonies produced by the liver derived HSC, although well within the range of the latter. Histologically, five types of colonies were identifiable which were produced by the thymus-derived HSC, indicating that these cells retain the potential to form a wide range of differentiated colonies.

Animals↗
PubMed1978

Maternal alloimmunisation in pregnancy. In vitro studies of T cell-dependent immunity to paternal alloantigens.

A secondary in vitro allograft reaction was used to demonstrate that spleen cells derived from allogeneically mated inbred mice were immunised against paternal alloantigens. In addition to the heightened alloantigen-specific in vitro response of these spleen cells, it was also found that spleen cells froma a wide variety of syngeneically and allogeneically mated mice were nonspecifically more reactive in the in vitro allograft reaction than spleen cells from virgin mice. However, when spleen cells freshly harvested from allogeneically mated mice were tested in a direct 51Cr release assay, lysis of target cells bearing the paternal alloantigens was demonstrable in only one-third of the experiments. It is proposed that T cell immunisation to paternal alloantigens occurs in pregnancy, but that cell-mediated cytotoxicity is inhibited.

Animals↗
PubMed1977

Development of the rabbit appendix. I. Electron-microscopic observations.

The progressive lymphoepithelial development of the rabbit appendix was examined by light and electron microscopy. At 5 days postnatally, the appendix wall primitively resembles the mature organ but lacks both the discrete lymphoid organization and most cell types. The dome appears to be the first recipient of lymphoid cells. By 18 days the lymphoid nodule has become compartmentalized and lymphoid. The epithelium, although not fully developed, is in contact with the lymphocytes of the dome. The 5-week-old appendix has all the lymphoepithelial components of the adult but lacks the size of the mature organ. At all ages reported, plasma cells and dendritic cells are absent. Bacteria, thought to be essential to appendical lymphoid development, are not apparent at 5 or 18 days. The features common to central or peripheral lymphoid tissues are discussed.

Animals↗