Macles et déséquilibre cristallogénétique

Summary A case of twin formation (Fig. 1) in rock-salt is crystallographically studied and a structural interpretation is proposed (Fig. 2). The twinning is produced experimentally by supersaturation of sodium chloride solutions, and appears as an outstanding case of the complications in the process of crystallization caused by desequilibrium during genesis and growth.     

Dégénérescence rétinienne expérimentale provoquée par le fluorure de sodium

Zusammenfassung Die Einspritzung von NaFl beim Kaninchen verursacht Netzhautveränderungen, welche derRetinitis pigmentosa ähnlich (Fundus, ERG, Histologie), aber auf einen Bezirk beschränkt sind.     

L'acide thymonucléique polymérisé, principe paraissant susceptible de déterminer la spécificité sérologique et l'équipement enzymatique des bactéries. Signification pour la biochimie de l'hérédité

Summary Interactions between two types of bacteria can produce either inhibition of the growth of one of these bacteria or transformation of their biochemical or antigenic properties. Authors have shown and studied one case of induction of a new serological specificity and a new enzymic equipment in aBacterium coli. This induction was produced through a substance liberated, during autolysis, by an otherBacterium coli. Active principle is a thymonucleic acid which, maybe, results from a solubilisation of chromosomes of the inductor bacteria. Hypothesis appears likely.     

Hypertension expérimentale et protéines sériques

Summary The authors investigated the distribution of serum proteins, especially the ₂ fraction, in rats with artificially induced hypertension (A), in similar rats made normotone by choline-free diet (B), and in a control group (C). A rise in the ₂ fraction of groupA andB was found, without a significant change of the other serum proteins.     

La biologie des hématinoprotéides oxygénables

Summary The author reviews a series of biological aspects of the study of oxygenable hematinoproteids, particularly with respect to evolution and adaptation. After a statement of some fundamental concepts of comparative biochemistry and of possible evolutionary relations between oxidation catalysts and oxygen carriers, the natural distribution of hemoglobins is reviewed and their specific characters are enumerated.A review is made of the data relating to the shape of the oxygen-dissociation curves and to the affinity of hæmoglobin for oxygen. It appears, generally speaking, that hyperbolic or almost hyperbolic curves and high affinity for oxygen are characteristic of primitive or embryonic hæmoglobins.A study of the function of hæmoglobin in the respiratory cycle of several animal species shows the vital importance of the oxygen carrier as well as the adaptation of the shape and position of the dissociation curve to the character of the respiratory function in the animal considered.The function of hæmoglobin in invertebrates, as oxygen carrier as well as providing a store of oxygen, is emphasized by a review of experimental data.The function of oxygen in the transport of carbon dioxide is reviewed from the standpoint of comparative biochemistry, and the lack of our knowledge is deplored.The characteristics of chlorocruorin show it to be a chemical mutation of an Annelid hæmoglobin.Our lack of knowledge in the field of the comparative biochemistry of hæmoglobin and chlorocruorin metabolism is pointed out.

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Conférence principale, présentée à la Société suisse de biologie médicale lors de la 127^e Assemblée générale de la Société helvétique des sciences naturelles à Genève, le 31 août 1947.     

Les propriétés mécaniques du caoutchouc

Summary A survey of recent work on the theories of the peculiar mechanical behaviour of substances with rubber-like properties is given. All the theories are based on the assumption that these substances (including rubber itself) are composed of very long, flexible chainmolecules. Any segment of a chain is linked to two neighbouring segments by bonds similar to those which are present in typical solids and to all other neighbours by linkages like the bonds prevailing between the particles of liquids. The chain molecules are intermingled so as to form a kind of a felt.This state of aggregation is intermediate between the solid and the liquid; it is called the rubber-like state (état gommoïdal). Elasticity, viscosity and plastic flow as well as the influence of crystallization, vulcanization and degradation are discussed in terms of this theory.     

Propriétés phytobiologiques de la sérotonine

Summary The serotonin (5-hydroxytryptamin) which shows a slight influence upon the growth of plant tissues, acts upon water uptake by regulating cellular permeability (latter is activated in the case of K⁺).     

Aspects biochimiques de la Régénération

Summary A survey of the biochemistry of regenerating animals has been made: after a critical discussion ofChild's metabolic gradients theory, the relative importance of respiration rate, carbohydrates, proteins and nucleic acids metabolism are stressed. The similarities between biochemical processes in the embryo and the regenerating organism are pointed out.

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Une grande partie de cet article est la reproduction d'un chapitre de notre livre « Embryologie chimique » (Masson, Paris, etDesoer, Liége); nous tenons à remercier les éditeurs de l'ouvrage qui ont bien voulu marquer leur accord. On y trouvera une bibliographie étendue sur les modifications chimiques dont l'organisme en régénération est le siège.     

Propriétés antiacétylcholinestérasiques du diiodométhylate debis-(diméthylamino-3-phénoxy)-1-3 propane,de ses dérivés phénoliques et des esters carbamiques correspondants

Summary Thein vitro anti-acetylcholinesterase properties ofbis-(dimethylamino-3-phenoxy)-1-3 propane dimethiodide (2842 CT) of two phenolics derivatives (3443 CT and 3116 CT) and of the two corresponding carbamic esters (3152 CT et 3113 CT) have been compared using human red blood corpuscles as enzyme source; under specified conditions, the Cl-50 are respectively 8 × 10^–7 M for 2842 CT, 3.5 × 10^–9 for the two phenolic compounds, and 1.5 × 10^–9 for the carbamic esters. The potencies of these phenols are very close to those of the carbamates, being a bit higher or lower depending on the concentration of the inhibitor and on the time of the readingThe two phenolic compounds, like 2842 CT, react readily with the enzyme contrarily to the carbamic esters which combine slowly. On the other hand the inhibition by the phenolic derivatives is as stable against washing as that by the carbamates. The carbamates, but not the phenols, show the slow displacement phenomenon.Some of these characteristics are compatible with the hypothesis that carbamic compounds could act through liberated phenolic functions but others indicate that carbamic groups have a role of their own.     

Photolyse ultraviolette et photoréactivation des bactéries — Aspects de dépolymérisation et repolymérisation des acides nucléiques bactériens

Summary Electrophoretic analysis of bacterial substance proves the departure, from UV irradiated microbes screened from light for a certain time, of substances which were responsible for increasing the charge density by surface unit during the first moments which follow the irradiation by UV rays. Spectrophotometric analysis of liquids having contained these bacilli proves concommitantly the diffusion of those substances from the bacterial substance to the aqueous phase and reveals their nature. The photoreactivity which is possible during the first moments following the UV irradiation of bacilli, due to the presence of the fragments of depolymerisation of nucleic acid macromolecule in the bacterial substance, becomes impossible after the departure (diffusion) of those fragments to the aqueous phase. These observations seem to show that the phenomenon of photo-reactivity is connected with the repolymerisation of the macromolecule primitively divided of desoxyribonucleic acid.     

Microméthode potentiométrique pour la détermination de la cholinestérase

Sans résumé     

Microméthode potentiométrique pour la détermination de la cholinestérase

Summary A simple very sensitive and usefull method is described for the potentiometric micro-determination of the cholinesterase of blood serum, globules and tissues, using an ordinary potentiometer and an antimonium electrode. This method makes it possible to determine the cholinesterase in solutions of acetylcholine down to 3 mg %.     

Contribution à l'étude d'une propriété répétitive du cerveau

Summary While pursuing the study of cortical functioning by the EEG. and after-image methods, we have come to believe that every stimulation evokes in the corresponding area of the cortex not only a simultaneous excitation but also acontinued action, i.e. after stimulation, several successive excitations of progressively diminishing intensity appear in the same area of the cortex.We have investigated the continued groups appearing on corticographical tracings taken from different cortical areas of the experimental animal (the rabbit) after various forms of stimulation (auditory, electrical, and visual). By comparing them with the after-images seen by human subjects in EEG. experiments, we have been led to identify the two phenomena.In order to carry this study further, we have undertaken two series of corticographical experiments, recording tracings takensimultaneously from the parietal and striate areas of the rabbit. The first series was intended to study the effects on the tracings of visual stimuli. The second was concerned with the effects on the same tracings of weak electrical stimuli.

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Nous avons consacré à cette propriété répétitive du cerveau une note parue dans les Comptesrendus de l'Académie des Sciences, Juillet 1955, Paris — dont le présent article constitue le développement.     

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.     

Substances régulatrices de la croissance végétale

Zusammenfassung Durch Einwirkung von Simazin wird bei Elodea die Photosynthese gehemmt, der Sauerstoffverbrauch durch Atmung erhöht und keine Zerstörung der Zellbestandteile beobachtet. In Gegenwart von Simazin bleiben die Deshydrasesysteme der Zelle aktiv.

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5^e communication (voir les travaux précédents deA. Gast etB. Exer).     

Paléontologie et expérimentation

Summary Since the morphogenesis of teeth is ruled by organizers (inductors) the change of position of one of them could have brought about an evolution of the denture such as is found in theCreodontia and Carnivores. Modern techniques of organ cultivation will perhaps solve some other paleontological problems (reappearance of teeth whose germs miscarry, modification of the size of the canines, which would permit us to suppose a certain reversibility).