Génétique et évolution des Nématodes libres. Perspectives tirées de l'étude deCaenorhabditis elegans

Summary Free-living nematodes are endowed with a set of properties that make them specially attractive for experimental work. Geneticists and evolutionists may be especially interested in their easy cultivation, great fecundity and polymorphism. As an example, some results are brought concerningCaenorhabditis elegans and related species: (1) Sex determination occurs as the expression of a genic balance involving differences in the number of chromosomes. The alternatives gynogenesis, amphimixis, or auto-heterofecundation take a prominent place in the reproductive processes of these species. (2) Polyploidy may be obtained by heat-shock, giving rise to individuals showing characteristic chromosomal unbalance and variability. (3)C. elegans, which cannot normally be raised at a higher temperature than 22°C, has been gradually adapted to temperatures up to 24.5°C. This acclimatization implies an adaptive transformation of the ovarian physiology; this effect is obtained after long training, taking more than 1000 generations. Study of the process of acclimatization shows that its genetical basis may be partly of a non-genic nature, partly of a genic type. Hypotheses are developed for explaining this phenomenon and for the understanding of the evolution from free-living to parasitic nematodes.     

Histochemical localization of lipids in the nuclei of human blood and haemopoietic cells

Zusammenfassung Die Anwesenheit von Lipiden im Kern der Zellen des Blutes und der hämopoetischen Organe wurde histochemisch nachgewiesen. Die Lipide scheinen ausschliesslich oder stark überwiegend in der Kernmembran und in den Nukleolen lokalisiert zu sein.     

Potentiation of the immunosuppressive effects of cytoxan by hyperbaric oxygen

Zusammenfassung Die intermittierende Anwendung hyperbarischen Sauerstoffs erhöht die die Antikörper unterdrückende Wirkung von Cytoxan bei Mäusen, die vorher mit Ochsenserum-Albumin und Freunds Adjuvans immunisiert worden waren. Der Wirkungsmechanismus des Sauerstoffs wird als Verhinderung der Transformation von kleinen Lymphocyten in immunbiologisch aktive Stammzellen gedeutet.

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Supported by U.S. Atomic Energy Commission Contract No. RLO-1927-13.     

Riboflavin in human milk

Zusammenfassung Riboflavin ist in der Muttermilch in Form von Flavin-adenin-dinucleotid anwesend, was für eine Komplexform spricht. Ferner wurden in der Milch zwei Flavoproteine, die DPN-Cytochrom C-Reduktase und DPN-Diaphorase reduzierten, gefunden.     

The effects of follicle-stimulating hormone on the uptake of labelled glycine by the chick embryo

Résumé On a étudié par autoradiographie l'incorporation de la glycine-1-C¹⁴ par l'embryon du poussin. L'incorporation était la plus élevée dans le tissu neural et puis dans le notochorde et les somites. Après traitement avec le FSH, une incorporation plus grande s'est produite dans les mésodermes chordal et somitique. On propose qu'il peut s'agir d'un effet morphogénétique. Il est particulièrement significatif que le mésoderme axial, qui joue un rôle si important dans l'induction du système nerveux, paraît être également le point d'action de l'hormone.

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Supported by Grant No. DRG-913 from the Damon Runyon Memorial Fund for Cancer Research and also by grants from the Medical Research Council, British Empire Cancer Campaign for Research and the U.S. Public Health Service to the Chester Beatty Research Institute (Institute of Cancer Research: Royal Cancer Hospital). The authors also wish to thank the National Institutes of Health, USA for the FSH preparations.     

Correlation between sensitivity to trypaflavine and DNA base composition in mutants ofBacterium paracoli 5099

Bacterium paracoli 5099 , , .