Comptes rendus des seances de l'Academie des sciences. Serie D, Sciences naturelles最新文献

A subconvulsive bilateral stimulation of the lateral entorhinal cortex has been applied in BALB/c mice at different time intervals after an appetitive operant conditioning task. 24 hrs later, compared to the control subjects, the performance was improved only in animals stimulated 30 min. after the first learning session. No change was observed in animals stimulated 30 sec. or 3 hrs. post-trial. These results suggest that entorhinal cortex is involved rather late in memory processes.

Polysome level was measured in Escherichia coli cells grown in the presence of sublethal doses of four different aminoglycosides which all induce mistranslation: streptomycin, neomycin, kanamycin and gentamycin. No significant variation was noticed as referred to the level of polysomes in normally growing cells. This observation indicates that the erroneous incorporation of amino acids into polypeptide chains does not necessarily result in the release of ribosomes from messenger RNA molecules.

The brain of the vertebrates contains three isozymic forms of the glycolytic enzyme enolase, two of which are neuron specific. These proteins could therefore be utilized as biochemical markers for various studies of neurons. We have devised a separation procedure which allows the measurement of the three enolase forms from minute amounts of tissue (50 to 100 microgram total protein). We show that this method can be applied to studies of brain microstructures, in vivo and in vitro (clonal cell lines) neural differentiation, and in measurements in biological fluids.

When orally administered, 5-(3-diméthylamino propyliden)-benzofuro [2,3-c] benzoxepin-1, which antagonizes several biogenic amines, is slightly sedative and has also endocrinological properties in the Rat, induces the appearance of localized lesions of uterine stroma in 2 to 16% of the animals. The cytological picture could suggest a tumorogenesis. In fact, these lesions represent a non-tumoral reactional hyperplasia with nuclear abnormalities due to a hormonal stimulation.

Processus of bone dedifferentiation have been shown in Mouse after amputation of the end of digits. Their meaning and their control have been searched for. Chemical sclerosis experiments on blood-vessels and ligature of the superficial femoral artery allowed to show they depended on the blood flow in the limb.

By immunofluorescent and immunoperoxidase techniques and with the use of highly purified antibodies, tubulin and its associated proteins, MAP1 and MAP2 have been identified and precisely localized in human spermatozoa. In relation to well known structural elements, tubulin appeared localized to the region of the axoneme, the centriolar adjunct and the equatorial part of the acrosome, in contrast MAP1 and MAP2 were localized to the post-nuclear region and in the fibrous sheath of the principal piece of the flagella.

The crystallization of the complex formed between aspartic acid tRNA from the yeast Saccharomyces cerevisiae and homologous aspartyl-tRNA synthetase is described. Crystals were obtained, using the vapour phase diffusion technique and ammonium sulphate as the precipitant agent.

An enzyme which catalyzes the phosphorolytic cleavage of thymidine, and whose behaviour is characteristic of thymidine phosphorylase, was purified 130 times from human blood platelets. The results obtained by chromatography and electrophoresis, enable us to consider the existence of a dimeric form of this enzyme.

Recording from convergent neurones--i. e. those responding to both non-noxious and noxious cutaneous stimuli--in the dorsal horn of the intact anaesthetized Rat, two distinct effects are seen after application of noxious stimuli: there is an activation of units of the segmental pool, along with a very powerful inhibition of the remaining neuronal population (diffuse noxious inhibitory controls, DNIC). Morphine at doses inadequate to directly depress the activity of these units specifically blocks the inhibition. Since DNIC is dependent upon supraspinal mechanisms, these observations show that morphine is capable of depressing certain descending inhibitory controls, at least when these are induced by noxious peripheral stimuli.

The administration of paraoxon, an organophosphate inhibitor of cholinesterases, elicits theta rhythms, fast rhythms and paroxystical alterations on the electrocorticogram of the Rat. The disappearance of these abnormalities of the cortical activity after administration of aromatic oximes seems to be in good correlation with the restoration of cerebral cholinesterase activity revealed by histochemical method.