Synthèse des protéines dans les pupes de Sphinx ligustri.

peer reviewedAT the beginning of the pupal stage of Sphinx ligustri, a lysis of larval tissues occurs. In winter, during diapause, the pupa is a bag full of blood containing a suspension of partially broken down larval tissues. In spring, diapause is broken, formation of adult tissues is speeded up and the moth becomes rapidly ready to emerge. Most of the amino-acids used for adult protein synthesis come from larval tissues; the question is whether the larval proteins are hydrolysed to free amino-acids before being used for adult protein synthesis, or whether adult proteins are built up from larger units that might be carried by phagocytes which are known to destroy the larval tissues. In order to approach an answer to this question, we decided to compare the mean specific rates of protein synthesis (rate of synthesis/amount of proteins) from one free amino-acid, namely glycine, in Sphinx ligustri pupæ, either in diapause or at the moment of the development of the adult organs. © 1957 Nature Publishing Group

Metabolism of carnitine and crotonic betaine in the chick embryo.

peer reviewe

On the conceptualization and measurement of flow

This chapter introduces in chronological order the three main measurement methods – the Flow Questionnaire, the Experience Sampling Method, and the standardized scales of the componential approach – that researchers developed and used in conducting research on the flow state. Each measurement method and underlying conceptualization is explained, and its strengths and limitations are then discussed in relation to the other measurement methods and associated conceptualizations. The analysis reveals that, although the concept of flow remained stable since its inception, the models of flow that researchers developed in conjunction with the measurement methods changed substantially over time. Moreover, the findings obtained by applying the various measurement methods led to corroborations and disconfirmations of the underlying models, and hence provided indications on how to interpret and possibly modify flow theory. The chapter then analyzes the emerging process approach, which conceptualizes and measures flow as a dynamic path rather than an object, and highlights its potential for integrating flow and creativity within the same conceptual framework. The final section outlines new directions for developing more valid and useful measurement methods that can help to advance the understanding of flow, its antecedents, and its consequences

Synthesis of 5-Methoxymethyl and 5-Ethoxymethyl-Desoxyuridines

AbstractOn a préparé, à partir de désoxyuridine, de la 5‐méthoxyméthyl‐désoxyuridine et de la 5‐éthoxyméthyl‐désoxyuridine. La pureté de ces produits a été démontrée par chromatographie sur papier dans deux systèmes différents, par un dosage des groupements alkoxyle, par la mise en évidence du désoxyribose et, enfin, par réduction catalytique en thymidine

The use of thioglycolate to distinguish between 3' AP (apurinic/apyrimidinic) endonucleases and AP lyases.

Addition of thioglycolate and DEAE-Sephadex chromatography were used to analyze the cleavage of the C(3')-O-P bond 3' to AP (apurinic/apyrimidinic) sites in DNA and to distinguish between a mechanism of hydrolysis (which would allow the nicking enzyme to be called 3' AP endonuclease) or beta-elimination (so that the nicking enzyme should be called AP lyase). For this purpose, DNA labelled in the AP sites was first cleaved by rat-liver AP endonuclease, then with the 3' nicking catalyst in the presence of thioglycolate and the reaction products were analyzed on DEAE-Sephadex: deoxyribose-5-phosphate (indicating a 3' cleavage by hydrolysis) and the thioglycolate:unsaturated sugar-5-phosphate adduct (indicating a cleavage by beta-elimination) are well separated allowing to eventually easily discard the hypothesis of a hydrolytic process and the appellation of 3' AP endonuclease. We have shown that addition of thioglycolate to the unsaturated sugar resulting from nicking the C(3')-O-P bond 3' to AP sites by beta-elimination is an irreversible reaction. We have also shown that the thioglycolate must be present from the beginning of the reaction with the nicking catalyst to prevent the primary 5' product of the beta-elimination reaction from undergoing other modifications that complicate the interpretation of the results

Contribution des acides aminés libres à la régulation osmotique intracellulaire chez deux crustacés euryhalins, Leander serratus F. et Leander squilla L.

Chez deux crevettes euryhalines (Leander serratus F. et Leander squilla L.), sont décrites les variations de concentration des acides aminés libres des tissus au cours de l'adaptation à l'eau saumâtre. L'abaissement de concentration de certains acides aminés libres intracellulaires (notamment de l'alanine, de la glutamine, du glycocolle et de la proline) contribue au mécanisme de régulation isosmotique intracellulaire, déjà observé chez d'autres Invertébrés euryalins, possédant ou non une régulation anisosmotique du milieu intérieur.The biochemical aspects of adaptation to brackish water (30 p. 100 sea water) have been studied in two species of euryhaline shrimps : Leander squilla L. and Leander serratus F. A first mechanism, consisting of an anisosmotic regulation of the blood, has been described by Pannikar in these organisms. A variation of osmotic pressure in the external medium, amounting to 1,7°C, brings about a change of only 0.°3C and 0.°6C respectively, in the blood of the two species considered. As shown by the slight change of water content of the muscles, the intracellular osmotic pressure has been approximately adjusted, in these shrimps, to the osmotic pressure of the blood. This isosmotic, intracellular regulation is accomplished for about 1/3 by the variation of concentration of a number of intracellular free amino-acids. The main rôle is played by glutamine, glycine and proline in both species. In L. serratus alanine also shows important variations. The mechanism of intracellular osmoregulation by changes of concentration of the amino-acids mentioned, has been observrd in all euryhaline Invertebrates studied so far. It appears as a general device of adaptation to changes of concentration of the internal medium, in euryhaline forms

Rôle de la variation de la composante amino-acide intracellulaire dans l'euryhalinité de Leander serratus F. et de Leander squilla L.

peer reviewe

Composition chimique du tube d'un pogonophore (Siboglinum SP.) et des formations squelettiques de deux pterobranches

peer reviewedThe chemical composition of the skeletons of two species of pterobranchs, Cephalodiscus inaequatus (Andersson) and Rhabdopleura sp. of one pogonophore, Siboglinum sp., was studied quantitatively. The tubes of Siboglinum sp. are composed of proteins (about 47 %) and chitin (about 33 %) ; these two substances are probably associated in large amounts as glycoproteic complexes. The amino acid composition suggests that these proteins belong to the class of scleroproteins. Their composition is very differtent from that of collagen and keratin. On the contrary, the coenecium of the two pterobranchs does not contain any chitin and the amounts of proteins are much lower (19 %). The proteins are characterized by a very high proportion of glycine (35 % of the total amount of amino acids).La nature chimique du tube d'un Pogonophore, Siboglinum sp., et des formations squelettiques de deux Ptérobranches, Céphalodiscus inaequatus (ANDERSON) et Rhabdopleura sp. a été étudiée au moyen de méthodes quantitatives. Les tubes de Siboglinum sp. se composent essentiellement de protéines (environ 47 %) et de chitine (environ 33 %), ces deux substances étant vraisemblablement associées en grande partie sous forme de complexes glycoprotéiques. La composition en acides aminés de les protéines s'apparente à celle des scléroprotéines et s'écarte profondément de la composition des collagènes et des kératines. Le coenecium des Ptérobranches, par contre, ne contient pas de chitine et sa teneur en protéines est beaucoup moins élevée (environ 19 %). Ces protéines sont caractérisées par la proportion remaquablement élevée de glycocolle (35 % de la somme des acides aminés d'origine protéique)