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Biomedical subjects

M Baudry

Publications and source records attributed to M Baudry.

At least 253 records · Page 14Linked to original sources
PubMed1978

[Effect of thryoidectomy on the properties of rat liver mitochondria during liver regeneration].

The properties of regenerating rat liver mitochondria are not changed by the thyroidectomy. Thus, hepatectomy induces, in thyroidectomized rats as in normal ones, a decrease in the activity of the outer membrane enzymes, a stimulation of oxidative phosphorylations and an increase of the turn over rate of mitochondrial proteins. Thyroid hormones do not seem to have a major effect upon the liver regeneration mechanism.

Animals↗
PubMed1977

[Facilitation of a stereotyped motor behavior (climbing behavior) by previous stimulation of dopaminergic receptors: hyposensitivity of autoreceptors?].

The sensitivity of dopamine receptors in Mouse striatum has been evaluated both behaviourally (responsiveness to apomorphine as regarviour) and biochemically (striatal level of homovanillic acid and its decrease induced by apomorphine) After a single administration of apomorphine (0.25 mg.kg-1 or 5 mg.kg-1) or piribedil, another dopamine agonist, a state of "behavioural facilitation" develops which differs from the state of hypersensitivity following blockade. This state of facilitation is characterized by a lower threshold dose of apomorphine eliciting the stereotyped behaviour, without modification of the response to higher doses. In contrast with the state of hypersensitivity, the level of homovanillic acid is not modified and the decrease of this level by a low dose of apomorphine is less important. The hypothesis is put forward that "behavioural facilitation" results from the hyposensitivity of a class of dopamine receptors, possibly autoreceptors, mediating an impaired activity of dopaminergic neurons and, consequently, inhibitory behavioural effects.

Animals↗
PubMed1976

Modulation in the sensitivity of noradrenergic receptors in the CNS studied by the responsiveness of the cyclic AMP system.

Various characteristics of the altered responsiveness to noradrenaline (NA) of the cyclic Amp (cAMP) generating system of cortical brain slices have been studied in rat after chronic reserpine treatment and in mice after chronic D-amphetamine treatment. Supersensitivity of the cAMP system to NA following reserpine treatment and subsensitivity after D-amphetamine treatment exhibit many common features. Firstly, in both cases the modified responsiveness to NA occurs rapidly after the beginning of the treatment (one day for reserpine and 5 h after amphetamine) and recovers slowly after the end of the treatment. Additionally, the altered states of sensitivity of the cAMP system to NA are the result of a modification of the maximal response rather than of an altered affinity of the system to NA. Since, following D-amphetamine treatment the change of sensitivity is still apparent in the presence of a potent phosphodiesterase inhibitor, the involvement of a gross alteration of phosphodiesterase activity is unlikely. In this case too, while the response to adenosine is slightly decreased, the responses to dopamine and serotonin of the cAMP system observed in brain slices following D-amphetamine treatment is not detected in a cell-free preparation. Thus, it appears that drug treatments, modifying synaptic transmission in opposite directions, lead also to changes in opposite directions of the responsiveness of the cAMP system to NA. The hypothesis that the mechanisms underlying such phenomena are related to a modified number of functional noradrenergic receptors is discussed.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1975

Histamine synthesis in the developing rat brain: evidence for a multiple compartmentation.

Subcellular fractionation techniques, radio-labeling by the 3H-precursor and pharmacological approach applied to the developing rat indicate the presence of at least two types of histamine-containing cells in brain. The presence of the histamine synthesizing enzyme in neurons is suggested by its developmental pattern: there is a 4- to 5-fold increase in enzyme activity from birth to adulthood, with a time-course paralleling the synaptogenesis in whole brain as well as in the 4 regions studied (medulla-pons, midbrain, hypothalamus and forebrain). As is the case for different transmitter synthesizing enzymes such as tyrosine hydroxylase, there is a shift in the subcellular distribution of histidine decarboxylase (H.D.) activity from the soluble fraction at birth to the synaptosomal fraction in the adult brain. On the other hand, several lines of evidence indicates that a portion of histamine is localized, at least in the noenatal rat brain, in mast cells: (a) the high level of histamine in the neonatal rat brain is, like in peripheral mast-cells, associated with a low enzyme activity; (b) the half-life of [3H]histidine injected s.c. at birth was about 4 days, a value close to that found in skin (a tissue rich in mast cells), but contrasting with that in adult brain (less than 1 h); (c) after subcellular fractionation, the endogenously formed [3H]histamine was recovered in the crude nuclear fraction as was the amine from peritoneal mast cells added to the brain homogenate; (d) the mast cell degranulators, compound 48/80 and polymyxin B, induce a small but significant release of the amine from incubated neonatal brain slices. Thus it appears that cerebral histamine is localized in at least two cell types. Its presence in neurons is compatible with a neurotransmitter function and its release from mast cells might represent some primitive form of cell-to-cell communication.

Animals↗
PubMed1975

[Influence of thyroid status on the electrophoretic pattern of rat liver mitochondrial proteins].

Liver mitochondria were isolated from normal and thyroidectomized rats and their protein components analyzed by polyacrylamide gel electrophoresis. In whole mitochondria 35 protein fractions with MW ranging from 10,000 to 135,000 were characterized. In the absence of thyroid hormone secretion, the amount of a MW 54,000 fraction was always decreased. Injection of small doses of 3,5,3'-triiodo-L-thyronine to the thyroidectomized animal restored the quantity of that protein fraction to normal. Isolated outer mitochondrial membranes showed the presence of 20 protein fractions. These fractions revealed no change after thyroidectomy. The mitoplast, which contained 35 fractions, exhibited a decrease of the MW 54,000 component in thyroidectomized rats. The mitoplast was separated into several fractions. Water soluble matrix proteins presented molecular weights ranging between 40,000 and 55,000. Proteins, which were slightly bound to the inner mitochondrial membrane and could be extracted by KCl, presented molecular weights between 25,000 and 45,000. Structural proteins showed a principal specific component of MW equals 23,000. Electrophoretic patterns obtained with these submitochondrial fractions were similar in normal and thyroidectomized animals. The mitoplast fraction which contained the insoluble cytochromes (a, a3, b, c1) was isolated ; its principal constituent, of MW 54,000 was significantly decreased after thyroidectomy. Thus, the lack of thyroid hormone secretion lowered the level of a protein constituent bound to the inner membrane of liver mitochondria. The synthesis of this constituent could be controlled by mitochondrial nucleic acids.

Animals↗