L'action du dithizone sur la rétine du lapin Etude électrophysiologique

Summary Dithizone provokes chorio-retinal lesions in the rabbit, visible ophthalmoscopally after 12 h and microscopally after 8 h. The ERG reveals much earlier alterations, theb wave diminishes rapidly and the ERG is abolished in 3 to 4 h. In the cases where no durable lesions are noted, the ERG is nevertheless pathological, theb wave being diminished 40 to 70% of its initial value during the first day, but becoming normal once again even if a permanent diabetes results. These anomalies of the ERG are related to acute hypoglycaemia and enzymatic blockage.

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Travail subventionné par la FondationEmil Barell (Bâle).     

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 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.     

Sur l'apogéotropisme du Phycomyces

Summary Under definite conditions of culture, growth of sporangiophore of Phycomyces has been investigated by Shadowgraphic method. During sporange formation, the rate of growth is the smallest (Fig. 1). The apogeotropic sensitivity of sporangiophores is the greatest before sporange formation; presentation and reaction times increase with age and strongly with light pre-treatment (Fig. 2, 3). Auxin could be responsible for apogeotropic reactions of Phycomyces.     

Composition du suc de décongélation du muscle strié de la grenouille

Summary Because of cell membrane destruction, fluid escaping a muscle on thawing contains a large amount of proteins (myogen and globulin X). Whilst usual gradientsa, b, andc are present in the fluid, the gradientsd ande also occurring in extracts of unstimulated frog muscles are replaced by the gradientx already found in extracts of in N₂ exhausted muscles.     

Propriétés chitinolytiques du liquide exuvial du ver à soie (Bombyx mori L.)

Summary The authors add further confirmation to the hypothesis of the role played by a chitinase during the process of moulting. By ligaturingBombyx mori-larvae between head and thorax, accumulation of moulting fluid takes place between the larval and nymphal cuticles, swallowing of this fluid being prevented. The chitinolytic properties of this moulting fluid are demonstratedin vitro. The activity of chitinase at different pH is investigated: the optimum pH lying at about 5.4.     

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.     

Effet du fluoroacétate et des rayons X sur la teneur en acide citrique du foie de la souris

Summary In contrast to rats, male mice injected with sodium fluoroacetate accumulate citrate in their livers, whereas females do not. Whole-body irradiation reduces the level of accumulated citrate in the liver as well as in other tissues of the mouse.     

Diminution de radiosensibilité du rat adulte en hypothermie profonde

Summary Using an appropriate technique, we put adults rats of both sexes under deep hypothermy (rectal temperature of 14–15°C). Under these conditions, the respiration and the cardiac rhythm are definitely slowed down.(1) Rats irradiated in a state of deep hypothermy with lethal doses of 800 and 900 r of X-rays, are partially protected. 50% of these animals survived more than 30 days, whereas all control animals died after 17 days.(2) The same degree of protection is obtained if the cooling is made in the presence of oxygen or under an air pressure of 1.25 atmosphere.     

Actions de la néostigmine,du D.F.P. et du 3318 CT sur la sensibilité du rectus de grenouille aux esters acétique,propionique et butyrique de la choline

Summary The potentiating effects of Neostigmine, D.F.P. and 3318 CT (a selective true cholinesterase inhibitor) on acetylcholine (ACh), propionylcholine (PrCh), butyrylcholine (BuCh) and amyltrimethylammonium (AmT), have been studied using the frog's rectus abdominis. Neostigmine increases the actions of the three esters much more than that of AmT. Low concentrations of D.F.P. potentiate maximally BuCh but have practically no effect on ACh, PrCh, and AmT. 3318 CT potentiates AcCh and PrCh but inhibits BuCh and AmT.These results indicate the specificity of the hydrolysis of pharmacologically active doses of BuCh, on the one hand, of AcCh and PrCh, on the other hand, by different enzymes or the frog's rectus.Results obtained with high concentrations of D.F.P. and with association of the different anticholinesterases indicate that a maximal or nearly maximal potentiation of one of these esters is already obtained with the specific inhibitor concerned; the supplementary inhibition of the non-specific enzymes thus appears to have no or only a poor effect.     

Relations du « métabolisme respiratoire » des bactéries et du type de bactériophage avec l'activité de substances antiphages

Summary Quantitative determination of bacteriolysis with different T_1–7-phages confirms earlier observations that with substances inhibiting the action of T₁-phage the normal respiratory metabolism of the protected bacteria is quantitatively restored in every detail.With T₂-phage, showing a different respiratory course of bacteriolysis, no effect is obtained with the same substance, either on the respiration of the bacteria or on the typical course of respiration during bacteriolysis. The action of the phage inhibiting substance against T₁-phage is therefore an effect of definite specificity.     

Conception nouvelle du galvanotropisme animal Expérience sur les Planaires

Zusammenfassung Die Galvanotaxis der Tiere ist fast immer kathodisch: Orientierung und Fortbewegung zur Kathode. SeitLoeb gehen die Erklärungen dahin, diese Reaktion nur mit Hilfe physiko-chemischer und physiologischer Begriffe zu erklären, jedoch ohne Erfolg. Ausgehend von einer Hypothese vonBohn über die Rolle der inneren Polarität der Organismen bei der Bestimmung ihrer polaren Bewegungen, zeigt der Verfasser, dass im Körper von Strudelwürmern zwei Typen von Anisotropie vorhanden sind bei Verwendung sehr schwacher galvanischer Ströme in Richtung der Längsachse der Tiere: Eine Anisotropie der elektrischen Stromleitung (grössere Leitfähigkeit bei homodromer — Kopf gegen Kathode — als bei antidromer Lage — Kopf gegen Anode); eine Erregungsanisotropie (grössere Erregung durch den elektrischen Strom bei homodromer als bei antidromer Lage). Die elektrische Anisotropie der Gewebe bestimmt die Erregungsanisotropie des Organismus. Die Richtung der Galvanotaxis wird bestimmt durch das Gesetz der maximalen Erregung: das Tier orientiert sich immer so, dass es durch den elektrischen Strom maximal erregt wird. Hieraus die kathodische oder homodrome Orientierung. Die gleichen Resultate ergaben sich auch mit Teilstücken des Strudelwurmes, ebenso mit dem isolierten Rüssel. Experimentell lässt sich die elektrische Anisotropie eines Strudelwurmes umkehren; es erfolgt darauf eine Umkehrung seiner Erregungsanisotropie und seiner Galvanotaxis, die anodisch wird.Die Anodenreaktionen von Echinodermen (zweiphasische Galvanotaxis) und der Wirbeltiere können wahrscheinlich durch das Optimum-Gesetz erklärt werden: Aufsuchen der minimalen Erregungsstellung (Scheminsky, Canella). Im Determinismus des Verhaltens spielen jedoch immer, ob die Galvanotaxis dem Gesetz der maximalen Erregung oder dem Gesetz des Optimums unterliegt, psychologische Faktoren eine Hauptrolle.     

Étude sur le choc produit par le polysaccharide du bacille du colon chez le rat porteur de tumeur (Note préliminaire)

Summary Aged preparations of polysaccharide fromE. coli were highly effective in inducing a lethal shock in rats bearing a tumor. This effect may be increased by some medications, while various steroid hormones afforded an efficient protection.     

Fixation et inclusion du matériel nucléaire deEscherichia coli

Zusammenfassung In Abhängigkeit vom pH der Fixierungsflüssigkeit und vorhandener Kationen zeigt der Bakterienkern in Dünnschnitten entweder eine grobe oder aber eine feine Innenstruktur. Die als Chromosomenstrukturen gedeuteten Koagulationsbilder werden erneut in Frage gestellt.     

Relations entre les taux cétoniques du plasma et des organes

Summary Ketone levels in the rat's organs (liver, muscle, lung, kidney, brain) do not seem to be correlated with the ketone level in the blood plasma. On the other hand, there are significant and high correlations between the ketone levels of different organs. These findings are not inconsistent with the generally accepted theory according to which blood distributes hepatic ketone bodies to the periphery. But ketone levels of the organs seem to be regulated not by variations of the plasma ketones, but by another common factor. At present, it is impossible to say how this regulation is effected.     

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.     

Le rôle du scientifique dans la conservation de la nature

Summary The concept of nature conservation has greatly varied in recent years. Instead of forbidding any human interference with nature the modern conservationnists think that man must control the natural balance in the protected areas through appropriate measures.This action must be under the permanent control of ecologists, who have the task of determining, among many other data, the carrying capacity of the area, the evolution of habitats under physical and biological influences, the structure of animal populations and the rate of reproduction.In the case of large animals, this new concept leads to substituting game management for static protection. Thus conservation of natural resources will need more and more cooperation from scientists, especially in the field of ecology and population studies.     

Essais d'inhibition de l'action inflammatoire cutanée du chloroforme chez le rat

Summary (1)—In the rat, total extracts of cortex, cortisone and A.C.T.H. do not retard the fixation of a vital colorant at the level of a cutaneous zone irritated by chloroform.(2)—Phenergan prolongs the delay in the appearance of the blue.(3)—Sodium salicylate selectively inhibits the inflammatory cutaneous action of chloroform, even after adrenalectomy.     

Action du LiCl sur de jeunes blastodermes de poulet cultivésin vitro

Summary The young blastoderms cultivatedin vitro, by the method ofNew, slightly modified, grow abnormally on a medium of albumen mixed with LiCl solution. It acts in the first place upon the morphogenesis, secondarily upon the differentiation of organs, if they are able to develop.

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