Action de l'orientation et de la qualité de la lumière sur le développement des protonémas de Bryales

Summary The radiations coming from Blanc Brillant de Luxe' fluorescent stimulate the growth and ramification of protonema ofCeratodon purpureus (Hedw.) Brid. This stimulation is caused by red light (660 nm). Multidirectional lightening is more favorable than unidirectional exposition.     

Effets de la réserpine sur le développement d'Oedipoda coerulescens L. (Acridien,Orthoptère)

Summary Inhibitory effects of reserpine on ecdysis and chromatic adaptation inOedipoda appear to be linked with changes observed in both neural and neuro-endocrine regulating systems.     

Étude cytochimique des groupes sulfhydriles au cours des modifications de la détermination embryonnaire chez l'œuf de l'oursinParacentrotus lividus

Summary A cytochemical study of the distribution of sulfhydryl groups in animalized and vegetalized embryos of the sea-urchinParacentrotus lividus has been made by use of the Bennett's reagent. The distribution of the sulfhydryl groups appears homogeneous in these embryos. No gradient has been observed in the experimental conditions used.     

Action de la triéthylènemélamie sur les mitoses de segmentation de l'œuf de Pleurodèle

Summary Triethylenemelamine (1/400 to 1/12000) induces pseudo-chiasmas and chromosome-breakage in the egg-segmentation mitoses ofPleurodeles waltlii Michah. The primitive effect is stickiness, breakages appear subsequently, but without an interval of time between: the primary physiological and the secondary genetical effect cannot be separated. There are points of breakability, which explains the symmetry of certain fragments. The action is inverted in the epidermal cells of the larvae, where spindle alterations are prominent. Cytodieresis is never inhibited.     

Effets de l'irradiation sur le métabolisme des acides nucléiques et de leurs dérivés acidosolubles chez le rat

Summary In the rat, X-irradiation leads to a decrease of the net RNA and DNA content of the spleen, without, however, increasing the low molecular weight nucleic acid derivatives in the acid-soluble fractions of the same tissue. It is suggested that an alteration of the cell membranes could account for the apparent elimination of these nucleic acid degradation products which should normally appear in the acid-soluble fraction.     

Effets comparés de laβ-propiolactone et du formol sur les propriétés inductrices de l'organisateur chez les amphibiens

Summary -propiolactone-treated dorsal lips ofAmbystoma mexicanum are grafted in the blastocele of young gastrulas. The inducing ability of dorsal lips is not altered. These results are compared with the effects of formaldehyde which suppress the inducing ability. An interpretation of these facts is proposed. The cross-linking reactions which occur between formaldehyde and proteins may be important for the suppressing of the inductive ability by this agent.     

Sur la caractérisation de dérivés guanidiques d'origine biologique par électrophorèse et chromatographie sur papier (chromatoélectrophorèse)

Summary Paper chromatography has been used in conjonction with electrophoresis in a perpendicular direction (chromatoelectrophoresis), in order to characterize various guanidoderivatives of biological interest and also citrulline. The isolation of definite spots can be obtained with a satisfactory selectivity by this procedure, at a higher speed than by bidimensional chromatography; and the use of a few coloured reactions (ninhydrine,Sakaguchi, diacetyle--naphtol andp-dimethylaminobenzaldehyde) on the same electrochromatogram has been successfully practised in this field.     

Action répressive de l'oxygène sur la biosynthèse de la fumarique-réductase d'Aerobacter aerogenes

Summary The cells obtained from anaerobic cultures ofA. aerogenes contain both a hydrogenase and a fumaric reductase, but lack one or several electron transporters necessary for the coupling of the two enzymes. It is possible to measure the fumaric reductase activity of the extracts in the presence of hydrogen, hydrogenase and benzyl viologen, using the Warburg manometric technique. In anaerobic cultures the reductase is an inducible enzyme. In aerobic cultures its formation is strongly repressed by atmospheric oxygen.     

Le rôle de l'hétérosis dans la compétition entreebony et son allèle normal

Summary Whereas in homozygous state the geneebony noticeably diminishes the sexual activity of the males, it can on the contrary increase it in heterozygous state; but this heterotic effect depends in a large measure on the direction of the crossing, and also on the genic and cytoplasmic context. It depends moreover on the temperature.The role of this activity in the populations whereebony is made to compete with its normal allel is discussed briefly.     

Déviation expérimentale de l'uretère primaire par la greffe de matériel cloacal chez le Triton

Summary A transplant consisting of the rudiment of a cloaca with some somatic material implanted at a certain distance ventral from the normal route taken by the pronephric duct can be the cause of a deviation of the duct from its normal course. The pronephric duct grows towards the secondary protodæum, whereas the duct is lacking in the part of the body behind the secondary proctodæum. It seems that the proctodæum exercises an attractive effect on the growing pronephric duct.The results of the experiments, at any rate, are in favour of the conception ofO'Connor (1938) andVan Geertruyden (1942), who found that the pronephric duct develops by its own independent growth. I cannot agree withVan Deth's opinion (1946), according to which the pronephric duct developsin situ out of the dorsal parts of the lateral plate.

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Expériences faites à Bruxelles, en avril 1947, grâce à une subvention de la « Nederlandse Commissie ter uitvoering van het Nederlands-Belgisch culturele verdrag ».     

Influences des modifications simultanées de la concentration en ions K et Ca du liquide céphalorachidien sur le système vasomoteur

Summary In dogs anæsthetized with morphine-chloralosane, the cerebral ventricles are perfused with artificial solutions. After having been warmed up to body temperature, these solutions are allowed to flow into a lateral ventricle by a needle inserted laterally through the skull, the outflow taking place through a second needle placed suboccipitally in the cisterna. An excess of potassium in the cerebral ventricles increases the vasomotor tonus and the vasomotor responses produced by faradization of the central end of the vagus in the neck and by changing the pressure in the isolated carotid sinuses. An excess of calcium depresses the tonus of the vasomotor center and its reflex responses. An excess of calcium may be neutralized by an excess of potassium. Perfusion with a solution containing no calcium increases the tonus and the responses of the vasomotor center, while the absence of potassium does not seem to have any influence on the vasomotor system. A solution without potassium and calcium produces an increase of the tonus and the responses of the vasomotor center, these effects being due to the absence of calcium.     

Les états de la matière dans la pétrogénèse profonde

Sans résumé     

Les états de la matière dans la pétrogénèse profonde

Sans résuméDoyen de la Faculté des sciences de Besançon.