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Biomedical subjects

M Baudry

Publications and source records attributed to M Baudry.

At least 235 records · Page 13Linked to original sources
PubMed1980

Regulation of hippocampal glutamate receptors: evidence for the involvement of a calcium-activated protease.

Specific [3H]glutamate binding to rat hippocampal membranes and the calcium-induced increase in this binding are markedly temperature-sensitive and are inhibited by alkylating or reducing agents as well as by various protease inhibitors. N-Ethylmaleimide, chloromethyl ketone derivatives of lysine and phenylalanine, and tosylarginine methyl ester decrease the maximum number of [3H]glutamate binding sites without changing their affinity for glutamate. Preincubation of the membranes with glutamate does not protect the glutamate "receptors" from the suppressive effects of these agents. The proteases trypsin and alpha-chymotrypsin increase the maximum number of [3H]glutamate binding sites. The effects of calcium on glutamate binding are different across brain regions. Cerebellar membranes are almost insensitive whereas hippocampal and striatal membranes exhibit a strong increase in the number of binding sites after exposure to even low concentrations of calcium. These results suggest that an endogenous membrane-associated thiol protease regulates the number of [3H]glutamate-associated thiol protease regulates the number of [3H]glutamate binding sites in hippocampal membranes and that this is the mechanism by which calcium stimulates glutamate binding. The possibility is discussed that the postulated mechanisms participate in synaptic physiology and in particular may be related to the long-term potentiation of transmission found in hippocampus under certain conditions.

Alkylating Agents↗
PubMed1979

Regulation of glutamate receptors by cations.

Current evidence suggests that glutamate is a major excitatory neurotransmitter in the mammalian central nervous system (CNS); particularly, glutamate excites most neurones in the CNS. Until recently this effect was widely used to study glutamate receptors and to distinguish them from those of other excitatory amino acids. The development of ligand binding studies for many neurotransmitters has facilitated the study of receptors at the molecular level and using these methods we recently reported the existence in hippocampal membranes of pharmacologically distinct sodium-dependent and sodium-independent glutamate binding sites, the former related to high-affinity uptake and the latter exhibiting several characteristics of postsynaptic receptor sites. We now report that, as with other neurotransmitters, several ions regulate the Na-independent binding of glutamate; the monovalent cations induce a decreased binding while certain divalent cations enhance this Na-independent binding. Additionally, since some of these effects appear to be irreversible, we propose that the regulation of glutamate binding by cations might account for the extremely long-lasting potentiation of synaptic responses found in the hippocampus following bursts of repetitive electrical stimulation (see ref. 9 for a review).

Animals↗
PubMed1979

Early effects of thyroidectomy and triiodothyronine administration on rat-liver mitochondria.

This work was undertaken to study the action exerted by thyroid hormones on mitochondria. By day 6 after thyroidectomy, the respective activities of two inner-membrane enzymes--succinate and beta-hydroxybutyrate cytochrome c reductases--had already dropped by 32 and 50%, whereas, in the outer membrane, the activity of rotenone-insensitive NADH-cytochrome c reductase did not change significantly. The decrease in the activity of the inner-membrane enzymes closely followed the disappearance of T3 and T4 from serum. 10 h after administration of 25 micrograms/100 g T3 to thyroidectomized rats, the activity of succinate and beta-hydroxybutyrate cytochrome c reductases and the oxygen consumption rate with succinate or beta-hydroxybutyrate were significantly increased, while, in the outer membrane, the activity of monoamine oxidase and rotenone-insensitive NADH-cytochrome c reductase remained unchanged. In the thyroidectomized rat, L-[3H]leucine incorporation in vivo is diminished in all the liver mitochondrial proteins, and especially in two constituents of MW 19 000 and 28 000. The radioactivity of these two components is also decreased in the normal rat treated with chloramphenicol, a specific inhibitor of mitochondrial protein synthesis. L-[14C]leucine incorporation in isolated liver mitochondria was significantly increased in the thyroidectomized rat, 10 h after T3 treatment. Thus, thyroid hormones have an early and preferential action on the mitochondrial protein synthesizing system and on the inner-membrane enzyme activities.

Animals↗
PubMed1978

[Binding of 3,3',5'-triiodo-L-thyronine (rT3) to human serum proteins].

The rT3-binding and human serum proteins was directly studied with tracer doses of radioactive rT3. Polyacrylamide gel electrophoresis showed 125I-rT3 added to human serum was distributed among two proteins: albumin (carrying 57% of tracer rT3) and TBPA )22%). No binding was observed to TBG, protein binding T4.

Humans↗