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Biomedical subjects

Y Boucher

Publications and source records attributed to Y Boucher.

62 records · Page 4Linked to original sources
PubMed1990

Estrogen modulated gonadotropin release in relation to gonadotropin-releasing-hormone (GnRH) and phorbol ester (PMA) actions in superfused rat pituitary cells.

The involvement of protein kinase C (PKC) in GnRH action is still a matter of controversy. We have conducted a comparative study of LH and FSH release in response to GnRH and to phorbol ester myristate acetate (PMA), an activator of PKC, by rat pituitary cells maintained in culture. The effect of E2 pretreatment coupled or not with PKC depletion was also studied. Different kinetics in the response of LH and FSH to GnRH were observed, suggesting that the intracellular pathways involved in the release process of the two hormones were somewhat different. Moreover, PMA (10 nM) stimulated LH release greatly and FSH release only slightly. Intracellular PKC depletion, obtained by a prolonged treatment (18 h) of the cells with PMA (1 microM), produced different results according to the endocrine status of the pituitary cells. GnRH (10 nM)-induced LH release was significantly decreased in PKC-depleted cells from proestrous females. For PKC-depleted cells from OVX females, it was decreased significantly only when cells had been pretreated by E2. These results suggest that the modulation of LH secretion by E2 involves PKC activation. FSH release was poorly stimulated by PMA; but, under any conditions, PKC depletion did not affect GnRH-induced FSH release.

Animals↗
PubMed1985

Transient ultrastructural variations of pulmonary lymphatic capillaries during the respiratory cycle of the rat lung.

The effect of respiratory movements on the endothelial wall of lung lymphatic capillaries was investigated by a morphometric study of their ultrastructure using a rodent model. The juxta-alveolar lymphatic capillaries from lungs were fixed in the inflated phase by vascular perfusion with aldehydes and compared to those from lungs fixed in a deflated phase. Important quantitative differences in lymphatic endothelial wall architecture were observed between the two states. The most salient finding was a marked reduction of the mean endothelium thickness from 320 +/- 55 nm in deflated lungs to 210 +/- 36 nm (P less than .01) in inflated lungs. The endothelial attenuation observed with inflated lungs was accompanied by a reduced frequency of interdigitation, the intricate pattern of intercellular contact (P less than .02), and a decreased number of lumenal and ablumenal endothelial projections (P less than .05). Despite these important variations in the dilated lymphatic capillaries, no typical open junctions (greater than 30 nm) were found among 105 intercellular contacts. The vesicular system varied slightly after lung inflation. Dilated capillaries showed a significant reduction in cytoplasmic vesicles during inspiration (P less than .01); however, the observed increases in lumenal and ablumenal vesicles were not found to be significant. As for numerical density and vesicular diameter, the fraction of cytoplasm occupied by the vesicles remains unchanged. Contrary to previous assumptions, these results suggest that intercellular clefts are not widened to the extent of open junctions (greater than 30 nm) by the mechanical movement of inspiration in normal lungs. Moreover, transient changes to the endothelial architecture seem to preclude any excessive widening of the intercellular cleft.

Animals↗
PubMed1985

Ultrastructural comparative study on lymphatic capillaries of the subendocardium, myocardium, and subepicardium of the heart left ventricle.

A comparative study, with quantitative analysis, was done on the fine structure of the lymphatic capillaries in the subepicardium, myocardium, and subendocardium of the left ventricle from dog hearts. In the three layers, the vesicular system of lymphatic capillaries was quite similar. More than 63% of the plasmalemmal vesicles are in contact with the abluminal or luminal endothelial membrane of cardiac lymphatic capillaries. Volume density measurements showed that plasmalemmal vesicles occupied between 8.0 and 9.3% of the endothelial cytoplasm. Overlapping and interdigitation contacts were frequent, whereas end to end contacts were scarce. The frequency of open junctions wider than 50 nm was inferior to 1%. The intercellular cleft was often obstructed by a focal tight junction (macula occludens). Intercellular spaces without specialized junctions were more frequent with subepicardial and myocardial lymphatic capillaries as compared with subendocardial vessels. Important quantitative variations of the fine structure were encountered on the abluminal side of the endothelial wall. In the subendocardium, the basement membrane covered 33% of the lymphatic endothelium whereas for the subepicardium and myocardium lymphatic capillaries, the values were reduced significantly to 18% (P less than 0.05) and 10% (P less than 0.001), respectively. An inverse relation was observed between the proportion of endothelium covered by basement membrane and the frequency of abluminal endothelial projections associated with the endothelial wall. Endothelial projections (EP) decreased in the following order: myocardium (19 EP/100 micron), subepicardium (15 EP/100 micron), and subendocardium (10 EP/100 micron). Quantitative morphological variations in the fine structure of lymphatic capillaries are believed to result from physiological (muscular movements, metabolic activity) and morphological (thickness of the connective tissue support surrounding lymphatic capillaries) differences existing between the three cardiac layers.

Animals↗
PubMedDate not supplied

Defining the core of nontransferable prokaryotic genes: the euryarchaeal core.

If lateral gene transfer (LGT) has affected all genes over the course of prokaryotic evolution, reconstruction of organismal phylogeny is compromised. However, if a core of genes is immune to transfer, then the evolutionary history of that core might be our most reliable guide to the evolution of organisms. Such a core should be preferentially included in the subset of genes shared by all organisms, but where universally conserved genes have been analyzed, there is too little phylogenetic signal to allow determination of whether or not they indeed have the same history (Hansmann and Martin 2000; Teichmann and Mitchison 1999). Here we look at a more restricted set, 521 homologous genes (COGs) simultaneously present in four sequenced euryarchaeal genomes. Although there is overall little robust phylogenetic signal in this data set, there is, among well-supported trees, strong representation of all three possible four-taxon topologies. "Informational" genes seem no less subject to LGT than are "operational genes," within the euryarchaeotes. We conclude that (i) even in this collection of conserved genes there has been extensive LGT (orthologous gene replacement) and (ii) the notion that there is a core of nontransferable genes (the "core hypothesis") has not been proven and may be unprovable.

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