Végétativisation de l'œuf de l'oursin par la Phénazone

Summary Phenazone employed in various concentrations on the eggs of the sea urchin,Paracentrotus lividus, has a powerful vegetalizing effect on their development. The role of the interference between phenazone and synthetic process of specific proteins is considered.     

Végétalisation de l'œuf de l'oursinParacentrotus lividus par le chloramphénicol

Summary Chloramphenicol, an inhibitor of protein synthesis, causes a strong vegetalization of whole larvae of sea urchinParacentrotus lividus. Combination of chloramphenicol and lithium causes a stronger vegetalization than either of these agents alone. Chloramphenicol suppresses the animalizing effects of Evans blue and zinc ions. The effects of chloramphenicol are compared with those of lithium and phenazone. It is suggested that vegetalizing effects of chloramphenicol are connected with its inhibitory action on protein synthesis and the perturbations of ribonucleic acid metabolism.     

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.     

Action de la ribonucléase sur les cellules du carcinome d'Ehrlich

Summary The reduced form of ribonuclease acts on the cells ofEhrlich's carcinoma by producing important changes in the RNA content of cells:(1) First, there is an important synthesis of intracellular RNA and an accumulation of free nucleotides (from the external medium). This phenomenon accompanies the necrosis of the cells.(2) After this first stage begins a rapid degradation of intracellular RNA.Simultaneously, the respiration of cells decreases whilst protein content remains unchanged.The oxidized form of ribonuclease has no action on the cells.

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Aspirant du Fonds national belge de la Recherche scientifique.     

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.     

Effets de l'actinomycine D sur le développement normal et sur les modifications expérimentales de la morphogénèse de l'oeuf de l'oursinParacentrotus lividus

Summary In the presence of actinomycin D (20–40 µg/ml), the development of the eggs of the sea urchin,Paracentrotus lividus, is slowed from the late morula and stopped at the blastula stage. The development is immediately stopped in the blastula treated with actinomycin D (20–40 µg/ml). The inhibitory effects of actinomycin D are prevented by deoxyribonucleic acid. Actinomycin D does not exert animalizing or vegetalizing effects. However, the enhancing of vegetalizing action of lithium and the weakening of animalizing effects of zinc ions and Evans blue have been observed in the presence of actinomycin D. These observations may reflect some difference in the state of dependence of differentiation of entomesodermic and ectodermic structures towards the nucleus.     

Sur le rôle de la sélection sexuellen dans l'évolution

Zusammenfassung Von Darwins Theorie der geschlechtlichen Zuchtwahl ausgehend werden einige Resultate experimenteller Forschung dargestellt, die auf neue Aspekte dieser Frage hinweisen. Es wird der qualitative Unterschied zwischen interspezifischer und intraspezifischer geschlechtlicher Zuchtwahl aufgezeigt. Die erstere hindert den Genaustausch zwischen den Arten, die letztere dagegen führt zu einem optimalen Genaustausch innerhalb einer Art. Es werden die Rolle der Weibchen und Männchen, der selektive Wert des Wildtypus verglichen mit Mutanten und die genetische Basis der Aktivität der Männchen diskutiert.     

Action des enzymes sur la gonadotropine urinaire de ménopause

Summary The action of various proteolytic and glucidolytic enzymes on the biological potency of Human Menopausal Gonadotropin was studied. Trypsin, chymotrypsin, papaïn and glucosidase attack the gonadotropin only after 6 h of digestion. Carboxypeptidase and RDE produce a rapid inactivation.     

Sur les variations stressogènes quantitatives de la sérotonine dans le cerveau

Zusammenfassung Das zerebrale Serotonin unterliegt im Verlaufe eines emotionellen Stress bedeutenden quantitativen Veränderungen. Bei Wildhasen, welche 14 Tage lang Schreckzeichen ausgesetzt waren, vermehrte sich die Menge des Serotonins und erreichte ihr Maximum am 7. Tag. Nachher sinkt die Menge unter den Normalwert, um am Ende der zweiten Woche wieder anzusteigen, wobei sie unter dem Normalwert bleibt.     

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.     

Conséquences de la thymectomie sur la formule leucocytaire chez le cobaye

Summary In infantile guinea pigs, thymectomy determined a decrease of the leucocyte count in the circulating blood, resulting essentially from the decreased number of lymphocytes.Eosinophiles increased noticeably in the same animals.Thus the consequences of thymectomy were proved to be exactly opposite to those of administration of thymus extract as described in a previous publication.     

Effet de l'hypothermie modérée sur le comportement maternel de la rate

Summary The maternal behaviour in the female white rat was ascertained by the method of spontaneous reactions to several stimuli.The observed rats were divided into two groups, and each of them was refrigerated once a day, by the method of detension, from the fourth to the seventh day after parturition, the body temperature attained being, on an average, 30°C. Females of the first group were refrigerated in recipients of the capacity of 2 1, and females of the second group in recipients of the capacity of 5 1.Disturbances of maternal behaviour were much more pronounced in the females refrigerated in recipients of the greater capacity than of those refrigerated in smaller recipients.     

L'évolution de la symbiose chez les Isoptères

Summary An attempt is made to retrace the evolution of symbiotic associations in Blattopteroidea, with particular reference to Isoptera. It seems probable that double symbiosis occured in the common ancestor of Blattids and Termites: intracellular microorganisms of bacteriocytes, xylophagous intestinal Flagellates. Where as actual Blattids, exceptingCryptocercus, have only retained the former, the primitive Termites, exceptingMastotermes, have only kept the latter. Evolved Termites (fam. Termitidae) have in turn lost the symbiotic Flagellates, but have acquired a rich and complex bacterial flora. — Some of these microorganisms, mixed with their aliments, certainly aid digestion (breakdown of cellulose), whilst others, localised at a particular level of the alimentary canal and not found in the alimentary mass, presumably play a different rôle. Furthermore, Protozoa are constantly associated with certains Termites (xylophagous Amoebae, humus-feeder Ciliates of the genusTermitophrya) and may play some rôle in the process of digestion. Finally, an association occurs between fundgus-growing Termites (subfam. Macrotermitinae) and mushrooms (Termitomyces).