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Biomedical subjects

J Thibault

Publications and source records attributed to J Thibault.

At least 127 records · Page 7Linked to original sources
PubMed1985

Molecular approach to thermogenesis in brown adipose tissue: cDNA cloning of the mitochondrial uncoupling protein.

The uncoupling protein (UCP) of mammalian brown fat is a specialized and unique component responsible for energy dissipation as heat. Translation and immunoprecipitation from sucrose-fractionated mRNA indicated that the mRNA of UCP sedimented at 14-16 S. A recombinant cDNA library prepared from mRNA of thermoactive brown fat enriched for UCP mRNA has been constructed and cloned in Escherichia coli. Recombinant plasmids were screened by differential colony hybridization to a cDNA probe complementary to poly(A)+ RNA isolated from thermogenic or from weakly thermogenic brown fat. Several differentially hybridizing plasmids were shown to contain UCP cDNA sequences by their ability to select a mRNA coding for an in vitro translation product that was immunoprecipitable with antibodies against UCP. Blot hybridization of brown fat mRNA to a 32P-labeled UCP cDNA probe revealed two major species of mRNA (15S and 18S). As compared to non-thermogenic tissue, a strikingly increased hybridization to the probe was observed with brown fat mRNA from thermoactive tissue. Moreover, hybridization was observed with RNA of brown adipose tissue from rat, hamster, or mouse but not with RNA from rat or mouse liver.

Adipose Tissue, Brown↗
PubMed1984

Rapid increase of mitochondrial uncoupling protein and its mRNA in stimulated brown adipose tissue. Use of a cDNA probe.

The increase in mitochondrial uncoupling protein in brown adipose tissue during acute stimulation by exposure of animals to cold was examined. Uncoupling protein level increased during the first hours of tissue stimulation. Use of a cDNA probe shows that synthesis of uncoupling protein mRNA was quickly stimulated. Animals treated with propranolol exhibited neither increase in uncoupling protein mRNA nor increase in the protein itself.

Adipose Tissue, Brown↗
PubMed1984

Increased level of mRNA for the uncoupling protein in brown adipose tissue of rats during thermogenesis induced by cold exposure or norepinephrine infusion.

We have studied by in vitro translation the mRNA population from rat brown fat in two situations where the thermogenic activity of the tissue is stimulated. Both cold exposure of rats and the presence of pheochromocytoma result in marked alterations among the polypeptides synthesized. Notably, in these two situations there was an increased labeling of polypeptides of the size of the heat-shock proteins and an increased labeling of the 32,000-dalton uncoupling protein of brown fat mitochondria, which is responsible for energy dissipation as heat. Stimulation of the thermogenic activity of brown fat thus results in a high level of mRNA encoding the uncoupling protein. Chronic delivery of norepinephrine mimicked the increase of mRNA for the uncoupling protein observed in animals exposed to cold or bearing pheochromocytoma. Thus, a neuromediator such as norepinephrine is able to trigger the induction of the mRNA encoding the mitochondrial uncoupling protein and is able to stimulate mitochondriogenesis.

Adipose Tissue, Brown↗
PubMed1984

Existence of dopaminergic neurons in the preoptic region of the goldfish.

Three morphofunctional techniques for the detection of biogenic monoamines have been used in order to find evidence for the presence of dopaminergic neurons in the preoptic region of the goldfish. The formaldehyde-induced fluorescence technique and the immunohistochemical demonstration of tyrosine hydroxylase allowed the detection of cell bodies containing catecholamines in the ventral and lateral walls of the preoptic recess of the goldfish. Specific antibodies indicated that at least part of these perikarya contain dopamine. Evidence for the projection of these neurons to the pituitary are given. These results support the assumption that dopamine, originating from the preoptic region, may act as a gonadotrophin release-inhibiting factor in goldfish.

Animals↗
PubMed1984

Putative dopamine-containing cells in the retina of seven species demonstrated by tyrosine hydroxylase immunocytochemistry.

Immunocytochemistry with antibodies to catecholamine synthesizing enzymes has revealed cells in the retina of chick, mouse, hamster, rat, guinea-pig, piglet and marmoset which contain tyrosine hydroxylase but not dopamine beta-hydroxylase. These findings suggest that the cells in question produce dopamine but that catecholamine synthesis does not proceed further to noradrenaline. Tyrosine hydroxylase-containing amacrine cells, located in the innermost part of the inner nuclear layer, were present in all the species studied. Some species showed atypically located amacrine cells in the inner plexiform or ganglion cell layer. In the rodents, the existence of tyrosine hydroxylase-containing interplexiform cells was suggested by the presence of a few short immunoreactive ascending processes. Three different morphological types of putative dopamine-containing cells were classified according to the level of ramification.

Animals↗
PubMed1984

Ultrastructural morphology of dopaminergic nerve terminals and synapses in the striatum of the rat using tyrosine hydroxylase immunocytochemistry: a topographical study.

Structures immunoreactive for TH were examined in the rat striatum (including caudate-putamen, nucleus accumbens and globus pallidus) by electron microscopy using the indirect peroxidase-labeled antibody method. Axon profiles and nerve terminals were the only structures stained by DAB precipitates in the axoplasm. The reactive boutons frequently contained a population of large pleomorphic vesicles (40-60 nm in diameter) but their interiors remained free of reactions. The synaptic contacts formed belonged principally to the symmetric type 2 of Gray while asymmetric Gray's type 1 synapses were rarely observed. The former were mostly apposed to dendritic trunks (rarely to perikarya) and the latter to dendritic spines. In addition, numerous immunoreactive nerve terminals were often found in close contact with small structures identified as the neck of dendritic spines. The active zone of these presumed synapses was characterized by a prominent thickening of the presynaptic membrane but the post-synaptic thickening was lacking. For similar reasons, it was difficult to assert the existence of one axo-axonic synapse when a positive nerve terminal was closely apposed to another one (generally unreactive). The exact morphology of dopaminergic synapses, or even their existence, have not been firmly established owing to large discrepancies between previous reports. No synapses, or synaptic contacts of either asymmetric or symmetric type were described according to the technique used. Our work was undertaken to elucidate further this problem, and in particular, we thought that regional differences in the synaptic organization might explain the divergent data. However, regional quantitative analysis performed in this study did not show significant differences in the percentage of either kind of synapses in the various striatal regions.

Animals↗
PubMed1984

[Local and regional complications of a fixed partial denture].

Local and regional complications of the partial dentures are rare and usually benign. Their effects are variable and include: pain, mobility, elocution difficulties, metallic or burnt taste, nausea, esthetic problems or repeated fractures. They are, to a great extent, avoidable if the prosthesis has been well conceived and produced from models studied on a parallelizer, and if occlusion was investigated in all its positions. Their numbers can be reduced by regular surveillance.

Denture Retention↗
PubMed1983

Molecular approach to thermogenesis in brown adipose tissue. Cell-free translation of mRNA and characterization of the mitochondrial uncoupling protein.

In order to develop a molecular approach of the thermogenesis mechanism in brown adipose tissue, cell-free translation was performed with mRNA obtained from control or thermoactive brown adipose tissue. Alterations were observed on analysis of the newly synthesized proteins and in particular at the 32,000 dalton level. Experiments using antibodies against the purified characteristic 32,000-dalton uncoupling protein of brown fat mitochondria were carried out. They indicated that the uncoupling protein was synthesized in the reticulocyte lysate with the same apparent molecular weight as the mature form. It is suggested that the development of the thermogenic capacity of brown fat cells is accompanied by an increase in specific mRNA coding for the uncoupling mitochondrial protein and that such a system could be an interesting one for study of mitochondrial membrane biogenesis.

Adipose Tissue, Brown↗
PubMed1983

Induction of oligodendrocyte-like properties in a primitive hypothalamic cell line by cholesterol, an eye derived growth factor and brain extract.

A serum-free medium has been devised which permits proliferation of the mouse primitive nervous cell line F7. When cholesterol, eye-derived growth factor and brain extract are added in this medium for 48 h, 80-90% of oligodendrocyte-like cells are generated. These cells have diminished substrate adhesion. They acquire the capacity to synthesize carbonic anhydrase II and myelin basic protein, two specific proteins of oligodendrocytes. These observations suggest that F7 clonal cell line, which has been previously shown to be a neurophysin cell precursor, is also a precursor for oligodendrocytes, and represents a bipotent stem cell line for both neuronal and glial cell lineages.

Animals↗
PubMed1983

Development and activation of brown fat in rats with pheochromocytoma PC 12 tumors.

To study the neurohormonal determinism of cellular growth and differentiation and mitochondrial development in brown adipose tissue (BAT), this organ was analyzed in rats bearing uncloned or cloned (PC 12) pheochromocytoma; comparison was made with cold adaptation. Both uncloned and PC 12 tumors induced an enlargement of tissue weight and DNA total content, although smaller than during cold adaptation. The following striking modifications were observed in rats bearing PC 12 tumors: strong vasodilation, increase in protein and phospholipid percentage, alteration of the fatty acid composition of phospholipids, increase in mitochondrial protein, large increase of the GDP binding to isolated mitochondria, and marked rise in specific amount of 32,000-dalton uncoupling protein (ascertained using immunological approach). It is concluded that secretions of PC 12 tumors can induce the same alterations in BAT as does the sympathetic system during cold adaptation of animals. An important contribution of norepinephrine to these effects is evidenced, but a specific function of other trophic factors secreted by PC 12 cells and by sympathetic nerves can be postulated.

Acclimatization↗
PubMed1982

Use of isografts and homografts in reconstruction of the nasal pyramid.

A technique for the reconstruction of the nasal pyramid using nasal auto and homografts is presented. It permits the correction of functional problems and of the nasal appearance at the same time. In cases of autografts alone, the results have been satisfactory. In cases of homografts, 10% resorption has been experienced to date. However, since the authors complete with alar swing and nose lift procedures, they have had no significant nasal depression so far. Only the future will tell if this last technique is valuable.

Adolescent↗
PubMed1980

Selective action of colchicine on protein synthesis and release in a clonal line of rat glial cells.

The effect of colchicine on protein synthesis and secretion in stationary cultures of clonal rat glial cells C6 was examined. Colchicine inhibited the synthesis of the brain specific S100 protein in intact cells but not in a cell-free protein synthesizing system derived from these cells. There was no demonstrable effect of the drug on the synthesis of any of the several hundred proteins resolved by a two-dimensional electrophoretic analysis. However, colchicine specifically enhanced the secretion of several proteins of molecular weighs of 30,000 and of 200-300,000 into the medium. Two of the high molecular weight proteins were apparently membrane proteins whose release into the medium was stimulated by the drug.

Animals↗
PubMed1980

Identification of rat brain polysomes synthesizing the brain specific enolase (14.3.2 protein), S100 protein and alpha and beta tubulin subunits.

Polysomes prepared from frozen rat brain powder were fractionated by centrifugation in a sucrose gradient. Individual fractions were used to program a reticulocyte lysate in a run-off reaction. The products of cell-free synthesis were assayed for the brain-specific enolase (14.3.2 protein) and S100 protein by immunoprecipitation with specific antisera and for tubulin by two-dimensional electrophoresis in polyacrylamide slab gels. The relative synthesis of these proteins by unfractionated free brain polysomes were 0.1 per cent, 0.05 per cent and 0.7 per cent respectively. After centrifugation in a sucrose gradient polysomes synthesizing S100 protein were separated from those synthesizing the other two markers. There was a threefold enrichment in the specific messenger RNA activity for each of the three proteins studied in their respective peak fractions of polysomes.

Animals↗
PubMed1979

Immunization of adult rats against 2.5 S NGF: effects on the peripheral sympathetic nervous system.

The biochemical and morphological changes effected by immunization of adult rats with 2.5 S mouse nerve growth factor (NGF) were studied in sympathetic ganglia and in representative target organs. This immunization procedure maintains high levels of circulating anti NGF-antibody for periods of months. Morphological analysis revealed a general reduction in the size of the adrenergic neurons in the superior cervical ganglion (SCG) which was also reflected at the biochemical level by a 30% decrease in total protein content and a 50--60% reduction in the total activities of all norepinephrine-synthesizing enzymes. However, there was no change in total choline acetyltransferase activity. The biochemical and morphological changes observed in the SCG seem to be confined to the neuronal cell body, since at any stage of immunization target organs (the submandibular and the pineal gland) remained unaffected. All sympathetic ganglia investigated--except the superior mesenteric ganglion--responded in a similar way to the immunization against 2.5 S NGF. These changes in the adrenergic cell bodies were largely reversible. The recovery of normal enzyme activities followed closely the decrease of the antibody titer after cessation of immunization boosting. This indicates that cell death is not caused by anti NGF-antibodies in ganglia of adult animals. Thus, in contrast to adrenergic neurons from newborn animals, which depend on NGF or a crossreacting NGF-like material for survival, differentiated adrenergic neurons need this factor for the maintenance of their normal function but not for survival.

Animals↗