Quelques commentaires sur les méthodes de culturein vitro de jeunes blastodermes de poulet

Summary The relationship between yolk entoblast and the nutritional medium in cultures of chicken blastoderm, classical type, was studied. In addition, some refinements to the research ofNew ^5–7, and some modifications permitting operations from the dorsal side, are proposed.

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Travail subventionné par le Fonds national suisse de la Recherche scientifique.     

Polarité électrique de fragments de Carotte cultivésin vitro

Summary The determination of PD's on carrot fragments growingin vitro has shown an electrical polarity of primary and secondary cultures of these tissues. The neoformations are negative in relation to the basis of the fragment. Controls, whether turned upside down or not, exhibit a similar polarity, which is influenced by the medium. The relation between electrical and morphological polarity cannot be stated at present.

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Grâce à un subside du Fonds national pour la Recherche scientifique, j'ai pu m'initier aux techniques récentes de culture de tissus dans le laboratoire deM. Gautheret, à Paris, que je remercie ici, ainsi que le Comité du Fonds (P.E.P.).     

Analyse expérimentale du développementin vitro des germes plumaires de l'embryon de poulet

Zusammenfassung Die Differenzierung der Dunen des Hühnerembryos lässt drei Phasen erkennen: 1. Eine der Haut fremde Anregung löst im Corium die Bildung der Dunenanlagen aus; 2. diese Dunenanlagen üben eine kurzfristige induzierende Wirkung aus, die die Epidermis zur Ausbuchtung der Dunen veranlasst; 3. die auswachsende Dunenepidermis kommt dann selber zur Induktionsaktivität und bewirkt das Eindringen der Coriumzellen in den in die Länge wachsenden Epidermiszylinder.     

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.     

Sur l'action de l'acide 2,4-dichlorophénoxyacétique sur la croissance des racines deZea mays et dePisum cultivéesin vitro

Summary (1) A response ofZea mays andPisum roots cultured aseptically to 2,4-dichlorophenoxyacetic acid has been observed.Depending on the concentrationZea mays shows an increase of the growth rate (optimal concentration 10^–11 mol) which turns over to an inhibition (above 10^–7 mol). The curve is similar to that obtained by 3-indoleacetic acid, which proves the phytohormonal character of 2,4-D.(2) ThePisum root is more sensitive than theZea mays root. A concentration of 10^–7 molinhibitsPisum in a high degree, whileZea mays is no more inhibited, thus demonstrating the selective herbicidal action of 2,4-D against isolated roots of Dicotyledons culturedin vitro.     

Action d'un inhibiteur de la carboanhydrase,l'acétazolamide,sur l'excitabilité du cortex,du thalamus et du rhinencéphale

Summary The electrical activity induced by stimulation of the cortex, diencephalon and rhinencephalon was studied in the rabbit under the influence of a carbonic anhydrase inhibitor, acetazolamide or Diamox. A significant decrease of the excitability was found in the diencephalon.The rapidity and the electivity of this action, as well as the blood pH variations simultaneously registered, suggest a specific inhibition of cerebral carbonic anhydrase by Diamox, although a participation of the metabolic acidosis cannot be fully excluded.     

Action d'un hépatome ascitique du rat sur les acides nucléiques du pancréas et du rein

Summary Animals having an ascites hepatoma show an increase in the incorporation of P³² into ribonucleic acid and desoxyribonucleic acid of the pancreas, whereas no change is seen in the kidneys. The variations noted in the pancreas may be compared with those observed previously in the liver and the adrenals. It can therefore be presumed that a substance which stimulates biosynthesis or disrupts the normal metabolic balance is produced by the ascites cells.

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Travail effectué avec l'aide matérielle de l'Institut National d'Hygiène.     

Action de l'eau oxygénée sur un anaérobie strict

Summary A quantitative study on the action of H₂O₂ uponCl. saccharobutyricum shows that the primary action is produced upon a first substance X, very likely an enzyme, following a mechanism such as one equivalent of oxygen gives a reversible combination, and two equivalents an irreversible combination.     

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.     

L'action de l'hypoglycémie sur l'électrorétinogramme du lapin

Summary Hypoglycaemia in the rabbit due to an intravenous injection of insulin results in an important diminution of the value of theb wave in the ERG (up till 80%). Nevertheless, this phenomenon does not follow directly upon the lowering of the blood glucose level but takes place, on the average, about 2 h later. This fact is explained by the enormous energy reserves of the retina, the lowering of the ERG taking place only when these reserves are exhausted.

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Travail subventionné par la FondationEmil Barell (Bâle).     

L'action du 2,4-dichlorophénoxyacétate de sodium sur les végétaux

Zusammenfassung 0,5prozentige Lösungen von 2,4-dichlorophenoxyessigsaurem Natrium verhindern das Keimen vonAgrostemma Githago, Hordeum vulgare undTriticum vulgare. Das Wachstum junger Pflanzen der drei Arten wird durch Verpflanzen auf mit 0,5prozentigen Lösungen dieses Stoffes getränktem Sand gehemmt. Schwächere Lösungen gestatten das Wachstum, es ist aber verlangsamt und die Pflanzen tragen Mißbildungen verschiedener Art, die an die nach Einwirkung von Colchicin und Heteroauxin beschriebenen erinnern. Stark verdünnte Lösungen (5·10^–6) beschleunigen das Wachstum und regen die Wurzelbildung an; diese Wirkung ist beiHordeum vulgare besonders deutlich.     

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.     

Action duCorynebacterium parvum sur les taux de lysozyme (muramidase) sérique

Summary An i.v. injection of 548 g of killedCorynebacterium parvum into C57B1 mice leads to significant changes in serum lysozyme (muramidase) levels. After an initial fall at 24 h, the activity of the enzyme increased progressively, reached a peak on the 9th day and returned to control range after the 15th day.     

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.     

Action du becaptan (β-mercapto-éthylamine) sur la radiosensibilité des cellules vaginales du rat femelle

Summary The authors studied the lesions observed in the vaginal smears of the rat after a local irradiation.They observed that an injection of cysteamine before the irradiation strongly diminishes the ratio of damaged cells.

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L. Darcis, Aspirant du F. N. R. S.     

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.     

Dans quelles conditions l'amnios de l'embryon de poulet peut-il se former en culturein vitro?

Summary The amnion was never before observed to formin vitro culture. A slight modification of the classic method ofNew consists in cultivating the blastoderm in its normal position, the ventral side against the medium. In this new position, the amnion develops normally.

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Travail subventionné par le Fonds national suisse de la Recherche scientifique.