Étude biochimique des poissons: 1. Variations semestrielles de la teneur en eau et en protéines du tissu musculaire de la truite Arc-en-ciel (Salmo gairdnerii Rich)

Summary The authors have noted, during the reproductive cycle of the Rainbow trout (Salmo gairdnerii Rich), important variations concerning water and total proteins content. This study shows a great correlation between the biological process and biochemical variations.     

Étude biochimique des poissons: 2. Variations semestrielles de la teneur en glycogène,en lipides totaux et en minéraux du tissu musculaire de la truite Arc-en-ciel (Salmo gairdnerii Rich)

Summary The variations of glycogen, lipids and ashes in muscular tissue of the Rainbow trout (Salmo gairdnerii Rich.) show that during sexual cycle there are 4 periods. Each period corresponds to a particular biological activity. The sexual activity cannot explain all the modifications of glycogen content.     

La synthèse de l'ADN prémitotique et préméiotique dans les cellules germinales de l'embryon femelle de la caille japonaise (Coturnix coturnix japonica)

Summary The premeiotic DNA synthesis of the female Japanese quail embryo begins after 9 days incubation. The germ cells in premeiotic S phase present a particular structure different from the structure found in germ cells during premitotic S phase. They are the precursors of the meiocytes in leptotene stage.

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L'auteur remercie vivement le ProfesseurL. Vakaet (R.U.C.A., Anvers) pour ses suggestions très valables.     

La population germinale des gonades chez des embryons chimères obtenus par l'association de fragments de blastodermes de Caille japonaise et de Poulet domestique

Summary The experimental realization of chimerical embryos (Martin's ¹³ technic) permits a quantitative appreciation of the modalities of the colonization of quail gonads by chick germ cells. Results clearly show that nature and origin of the somatic part of the gonad areas settle the characters of the genital ridges populating, and specially the specific index of asymmetry expressed by the percentage of PGC colonizing the right gonad.     

Germline development in vertebrates and invertebrates

In all animals information is passed from parent to offspring via the germline, which segregates from the soma early in development and undergoes a complex developmental program to give rise to the adult gametes. Many aspects of germline development have been conserved throughout the animal kingdom. Here we review the unique properties of germ cells, the initial determination of germ cell fates, the maintenance of germ cell identity, the migration of germ cells to the somatic gonadal primordia and the proliferation of germ cells during development in vertebrates and invertebrates. Similarities in germline development in such diverse organisms as Drosophila melanogaster, Caenorhabditis elegans, Xenopus laevis and Mus musculus will be highlighted. Received 11 December 1998; received after revision 25 January 1999; accepted 25 January 1999     

Shedding by rod photoreceptors after sunrise in fish

Diurnal shedding by retinal rods was studied in wild cutthroat trout,Oncorhyncus clarki, hatchery rainbow trout,Oncorhyncus mykiss, and the plains killifish,Fundulus zebrinus, by counting the shed tips of rod outer segments ingested as phagosomes by pigment epithelial cells. After sunrise, phagosomes increased in all species, but fewer occurred in trout, and these were elevated from 3 to 9 hours after sunrise. Shedding occurred earlier in the light period and was more robust in killifish, with phagosomes elevated from 1.5 to 6 hours after sunset. The data suggest that both production of phagosomes by shedding and their subsequent disposal are slower at the lower temperatures experienced by trout. Otherwise, rod shedding produced under natural lighting is not appreciably different than that provoked by sudden onset of artificial light.     

La synthèse du DNA dans les cellules germinales de l'ovaire de poulet pendant la dernière semaine de la vie embryonnaire

Summary DNA synthesis in the germ cells of the ovary of the chicken embryo during the last week of incubation is studied in vivo and in vitro by tritium autoradiography.     

Sur les durées respectives du pouvoir attractif de l'épithélium germinatif et de la réactivité des cellules germinales à ce pouvoir,chez l'embryon de Poulet

Summary Experimental results of different authors show that the attractive stimulus of the germinal epithelium for the germ cells in the chick embryo lasts less long than the reactivity of these cells to the same stimulus. However, both of them (stimulus and reactivity) last far longer than the period of the incorporation of germ cells into the primordia of the gonads. Each of them disappears when an important phase of differentiation is about to start in the group of cells concerned.     

Temperature acclimation of Mg2+Ca2+-myofibrillar ATPase from a cold-selective teleost,Salvelinus fontinalis: a compromise solution

Summary Brook trout (Salvelinus fontinalis, Mitchill) were acclimated over 15 weeks to either +4°C or +24°C. The effects of temperature on myofibrillar Mg²⁺Ca²⁺-ATPase activities were investigated. In contrast to goldfish, temperature acclimation does not alter the kinetic properties of the brook trout myofibrillar ATPase. Activation energy (G^#) is lower and substrate turnover number is higher than values previously reported for cold-adapted stenotherms. Properties of brook trout ATPase appear to be a compromise enabling function across a broad temperature range. The different strategies of adapting to seasonal temperature variations are briefly discussed.The authors are grateful to the Wellcome Trust for financial support.-Correspondence should be addressed to I.A.J.     

Action du DDT sur le peuplement en gonocytes des ébauches gonadiques de l'embryon de Poulet agé de 6 jours

Summary A brief immersion of chick eggs in a DDT aqueous solution, before the incubation, provokes a strong reduction of the number of germ cells in the gonads, when the embryos are 6 days old. Some hypertrophied gonocytes are pycnotic. Hypotheses are proposed in order to explain the mechanism of DDT action.     

What leads from <Emphasis Type="Italic">dead-end?</Emphasis>

The 129 mouse strain develops congenital testicular germ cell tumors (TGCTs) at a low frequency. TGCTs in mice resemble the testicular tumors (teratomas) that occur in human infants. The genes that cause these tumors in 129 have not been identified. The defect at the Ter locus increases TGCT incidence such that 94% of 129-Ter/Ter males develop TGCTs. The primary effect of the Ter mutation is progressive loss of primordial germ cells (PGCs) during embryonic development. This results in sterility in adult Ter/Ter mice on all mouse strain backgrounds. However, on the 129 background, Ter causes tumor development in addition to sterility. Therefore, Ter acts as a modifier of 129-derived TGCT susceptibility genes. Ter was identified to be a mutation that inactivates the Dead-end1 (Dnd1) gene. In this perspective, I discuss the possible areas of future investigations to elucidate the mechanism of TGCT development due to Dnd1 inactivation. Received 29 September 2006; received after revision 29 January 2007; accepted 19 February 2007     

Sur l'origine de l'hypoblaste chez les oiseaux

Summary In the hypoblast-deprived chick embryos, with the help of carbon particle marking and tritiated thymidine labelling, it was found that the regenerated hypoblast consists of the cells invaginated through the primitive streak and those derived from the germ wall.

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

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L'auteur a bénéficié d'une bourse fédérale suisse pour les étudiants étrangers.     

Genetics of early mammalian folliculogenesis

Early ovarian folliculogenesis begins with the breakdown of germ cell clusters and formation of primordial follicles. Primordial follicles are the smallest ovarian follicle units continuously recruited to grow into primary and more advanced ovarian follicles. Genes expressed in the germ cells such as Figla, Nobox, Kit and Ntrk2, as well as genes expressed in the surrounding somatic cells such as Foxl2, Kitl and Ngf, play critical functions during early folliculogenesis. Transgenic mice continue to provide important insights into the genetic pathways that regulate early mammalian folliculogenesis. Genes critical in early folliculogenesis are important determinants of reproductive life span and represent candidate genes for human ovarian failure. Received 25 August 2005; received after revision 18 October 2005; accepted 21 November 2005     

Etude électrophorétique des variations de composition d'extraits musculaires de Lapin sous l'influence de la fatigue et de la contracture par le monobromacétate de soude

Summary Rabbit muscular globulins soluble between the ionic strengths 0.15 and 0.35 are, in an almost native state, the and myosins ofDubuisson. The extractability of both, and, by salt solutions is greatly reduced when the rabbit muscle has been stimulated to exhaustion or poisoned with the sodium salt of monobromacetic acid till a state of rigor is obtained. This reduction however does not proceed in an absolutely similar way for and, indicating probable functional differences between these two myosins. The other soluble muscular proteins are practically not affected, as far as the method permits this to be assertained.     

Étude comparée de la multiplication des cellules germinales à la fin de la première semaine de la vie embryonnaire chez trois espèces de Gallinacés (Gallus domesticus,Meleagris gallopavo,Coturnix coturnix japonica)

Summary Counts were made of the numbers of germ cells in quail embryos aged 4–7 days' incubation. The rate of growth in the population of gonocytes was compared to these of chick and turkey embryos during the same period. The increase is exponential in the three species and the rates are more similar between quail and turkey than between each of them and the chick.     

Etude autoradiographique de l'incorporation de la thymidine-3H,de l'uridine-3H et de la phénylalanine-3H dans les chloroplastes deClivia miniata etBilbergia sp.

Summary Mature chloroplasts ofClivia miniata etBilbergia sp. show the intensive incorporation of thymidine³H into DNA and uridine³H into RNA. On the contrary, phenylalanine³H is mostly incorporated in the proplastids.     

Trajectoires et Impasses de la Solution de Schwarzschild

Sans résumé Présenté par J. D. North     

The fate of intramitochondrial paracrystalline inclusion bodies in germ line cells of water frogs (Amphibia,Anura)

Summary Numerous intramitochondrial pararystalline inclusion bodies (ICIB) were observed in the germinal plasm of a mid-blastula, and in primordial germ cells (PGCs) after their migration to the germinal ridges, inRana ridibunda, R. lessonae andR. esculenta. In oogonia the number of ICIB decreases rapidly. Single ICIB are observed in the germ cells up to the leptotene stage; they have never been observed in pachytene oocytes. In diplotene oocytes that have reached a diameter of about 100 m ICIB are visible again, and their number increases concomitantly with oocyte growth.     

Etude de l'influence de la tension d'O2, de CO2et de l'anaérobiose sur la morphologie et le nombre des colonies de pneumocoque

Summary Cultivation ofStreptococcus pneumoniae is markedly favored by strict anaerobiosis if compared with relative anaerobiosis.

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Remerciements. Je remercie vivement Mme A.M. Schmidt de son assistance technique attentive et de sa collaboration à la rédaction du manuscrit.