Biomedical subjects

R A Segal

Publications and source records attributed to R A Segal.

4 recordsLinked to original sources

PubMed1992

Changes in neurotrophin responsiveness during the development of cerebellar granule neurons.

Neurotrophins and their receptors are widespread in the developing and mature CNS. Identifying the differentiation state of neurotrophin-responsive cells provides a basis for understanding the developmental functions of these factors. Studies using dissociated and organotypic cultures of rat cerebellum demonstrated that the neurotrophins brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) affect developing granule cells at distinct stages in differentiation. While early granule neurons in the external germinal layer responded to BDNF, more mature granule cells responded to NT-3. BDNF, but not NT-3, enhanced survival of granule cells in cultures of embryonic cerebella. Thus, BDNF and NT-3 have distinct sequential functions that are likely to be critical in the development of the cerebellum. BDNF may promote the initial commitment, while NT-3 may direct the subsequent maturation of granule cells.

Analysis of Variance↗

PubMed1991

Monozygotic twins with seizures. Shared characteristics.

Eleven sets of monozygotic twins with idiopathic seizure disorders seen at Children's Hospital, Boston, Mass, were reviewed Nine twin pairs were concordant for seizures. A marked correlation in the precise timing of onset of seizures was found; three sets of twins had their first clinical seizures within a 24-hour period of one another. The clinical features of the seizures and the electroencephalographic patterns, including the location of focal discharges, were strikingly similar in the twin pairs. The significance of these findings in suggesting aberrant processes that may contribute to epileptic syndromes is discussed.

Brain↗

PubMed1978

Studies on intercellular LETS glycoprotein matrices.

Intercellular matrices secreted by chick embryo fibroblasts in culture were studied by scanning electron microscopy. Cell-cell contact is a prerequisite for the expression of such matrices. The smallest fiber detected by transmission electron microscopy is 5--10 nm in diameter. These matrix fibers tend to cluster to form bundles. Immunofluorescence and immunoferritin procedures reveal that LETS protein is one of the components of the matrices. The matrices are isolated from other cellular organelles by detergent treatment. More than 90% of the proteins in cell-free matrices are LETS protein, suggesting that the matrices are probably made of only one component--LETS protein. Since the solubilization of matrices requires beta-mercaptoethanol, LETS protein matrices may be the first known polymer system in nature to use disulfide linkage as an intermolecular polymerization vehicle. Collagen does not appear to be involved in such matrices. The LETS protein matrix supports the morphological conversion of rounded cells into spindle-shaped, and also promotes myoblast fusion. It does not, however, exert an effect upon cell growth, the rate of glucose uptake or protease production.

Cell Count↗

PubMed1977

Differences in the responsiveness of splenic, lymph node, and peripheral blood lymphoid cells to tumor membrane extracts.

The blastogenic response of normal spleen, lymph node, and peripheral blood lymphoid cells to tumor-associated antigens (TAA) derived from two syngeneic C57BL/6J tumors was measured by [3H]thymidine incorporation. Peripheral blood cells were responsive to TAA from B16 melanoma and from BW10232 mammary carcinoma at both a high (10(-1) to 10(-3) mg/ml) and a low (10(-5) to 10(-6) mg/ml) concentration of antigen. While peripheral blood cells always responded to TAA, spleen cells and lymph node cells did not. When spleen and lymph node cells did respond, they sometimes responded at different concentrations of TAA than did the peripheral blood cells. Spleen cells generally responded to "low" concentrations of TAA, while lymph node cells responded to "high" concentrati-ns of TAA. These data suggest two subpopulations of lymphoid cells capable of response to TA.. Spleen cells from mice bearing the BW10232 mammary carcinoma became responsive to BW10232 TAA at low concentrations of antigen. Lymph node cells became responsive at high concentrations of BW10232 antigen. The response of both subpopulations to BW10232 TAA was amplified in peripheral blood cells. Spleen cells were 30 times more responsive in the tumor bearer than in normal animals, while lymph node cells were only 3 times more responsive. It is shown that lymphoid cells taken from different areas or "lymphoid compartments" do not always show similar responses and should not be considered equivalent in evaluating immune responses to tumor cells.

Animals↗