Stochastic prey-predator relationships: A random evolution approach

The formalism and results of the theory of random evolutions are used to establish and investigate a model for two randomly interacting populations. The asymptotic stability of the expected solution is studied and contrasted to that of the associated deterministic system.     

Choline acetyl transferase activity in chick embryo neuroretinas during development in ovo and in monolayer cultures

The specific activity of the enzyme choline acetyl transferase (CAT) in chick neuroretinas was investigated during in ovo development and in monolayer cultures. The enzyme activity was barely detectable on the 6th day of incubation but increased markedly between the 7th and 11th days. The activity increased sharply between the 15th and 17th days and then slowly until hatching. When cell suspensions from 6- to 7-day neuroretinas were cultured as monolayers, CAT specific activity increased rapidly. After 4–5 days in culture, the activity of the enzyme was identical to that found in the neuroretina on the 11th day of incubation. Cells from 9-day neuroretinas also differentiate in monolayer cultures, but with a more irregular pattern. These data show that cholinergic neurons from chick embryo neuroretina differentiate in monolayer cultures without a lag and at the same rate as in vivo.     

Du probleme de l'origine des Dinosauriens d'apres les donneesde l'ichnologie du Trias

With the data of the osteological paleontology and these of the ichnology, the authors attempt to restore the biotopes where lived the trackmakers, biotopes which have favoured in the Triassic the evolution and the expansion of the Archosaurs, the specialized Reptiles in the easy and rapid locomotion. They pointed out that the chirotheroid footprints cannot be attributed at all events to the Pseudosuchians and they come to the conclusion that Dinosaurs and Pseudosuchians, as separated groups, are appeared as early as the lower Triassic.     

Characterization of two gangliosides from human leukemic polymorphonuclear leukocytes.

Eight bands of gangliosides, from human polymorphonuclear leukocytes were demonstrated by thin-layer chromatography. Bands 4 and 5 were isolated and purified in sufficient amounts to allow their biochemical identification by thin-layer chromatography, gas chromatography and sequential action of glycosidases and neuraminidase. The major ganglioside was characterised as N-acetylneuraminylgalactosyl-beta-N-acetylglucosaminyl-beta-galactosyl-beta-glucosylceramide. A second ganglioside was tentatively identified as N-acetylneuraminyl-galactosyl-beta-N-acetylglucosaminyl-beta-(N-acetylneuraminyl)galactosyl-beta-glucosylceramide. Both gangliosides isolated were hydrolysed by neuraminidase. However, treatment of the intact cells with neuraminidase did not alter the ganglioside pattern.     

Capacités reproductrices et descendance de poulets ayant subi un transfert de cellules germinales primordiales durant la vie embryonnaire

Résumé Des cellules germinales primordiales de Dindon, transférées par injection intravasculaire à des embryons de Poulet préalablement stérilisés, peuvent subir une maturation complète dans les gonades de l'hôte et fournir des gamètes plus ou moins aptes à la fécondation.Les spermatozoïdes résultants ont fécondé des oeufs de poule avec une fréquence plus grande que les spermatozoïdes normaux de Dindon, mais sans permettre un développement embryonnaire plus important ou plus normal. Cependant, on n'est pas parvenu à leur faire féconder des oeufs de dinde.Les ufs résultants ont montré parfois un vitellus anormal et n'ont été pondus que durant 7 mois. Mis en présence de spermatozoïdes de coq, ils ont été quelquefois fécondés (ou peutêtre simplement activés), mais ils n'ont jamais fourni d'embryons. Fécondés par des spermatozoïdes de Dindon, ils ont fourni des embryons, parfois anormaux, qui ont atteint dans le meilleur cas le 15è jour d'incubation (stade 38 HH). Certainespraepennae de l'embryon qui a atteint ce stade montraient une pigmentation rouge brun qui ne peut pas être déterminée par le génotype du zygote (celui d'un Dindon de race blanche) et qui rappelle le phénotype de la mère nourricière (une poule rouge brun).A la suite de transferts intraspécifiques de cellules germinales primordiales, on a pu obtenir la maturation d'ovocytes de Rhode Island Red à l'intérieur d'un ovaire de Wyandotte Blanche (chez deux poules) et vice versa (chez une poule). La ponte a également été possible, mais à une fréquence souvent inférieure à la normale.Lorsqu'une poule Wyandotte Blanche, portant des ovocytes de Rhode Island Red a été accouplée à un coq Rhode Island Red normal, le duvet de leurs descendants s'est montré plus clair que celui des poussins Rhode Island Red dans un cas, mais il a été remplacé ensuite par un plumage rouge brun conforme au génotype.Lorsqu'une poule Rhode Island Red, portant des ovocytes de Wyandotte Blanche a été accouplée à un coq Wyandotte Blanche normal, le duvet de leurs descendants n'a jamais été conforme au génotype. Il présentait toujours du pigment noir plus ou moins étendu et, dans un cas, du pigment rouge brun, qui sont tous deux présents chez la mère nourricière. On ne connaît ni l'origine ni le mécanisme d'un tel transfert de pigments, qui ne représente peut-être qu'un effet transitoire affectant le duvet de la première génération. La crête, quant à elle, s'est toujours montrée conforme au génotype d'origine.

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Reproductive capacity and offspring of chickens submitted to a transfer of primordial germ cells during embryonic life

Summary Turkey primordial germ cells transfered by intravascular injection to previously sterilized chick embryos can undergo complete maturation inside the host's gonads and can give rise to gametes which are more or less suitable for fertilization.The resulting spermatozoa fertilized hen eggs at a higher frequency than normal turkey spermatozoa, but without allowing a longer or a more normal development. However, it was impossible to fertilize turkey eggs with them.The resulting eggs sometimes had an abnormal-looking yolk and were laid during the first 7 months only. Brought in contact with chicken spermatozoa, they were fertilized (or perhaps merely activated), but they never gave rise to embryos. Fertilized by turkey spermatozoa, they developed into embryos, sometimes abnormal, which in the best case reached the 15th day of incubation (stage 38 HH). Somepraepennae of the latter embryo showed a red-brown pigment which cannot be determined by the genotype of the zygote (a white turkey's) and which resembled the phenotype of the foster mother (a red-brown hen).After intraspecific transfer of primordial germ cells, maturation of Rhode Island Red oöcytes inside a Wyandotte White ovary (in two hens) and vice versa (in one hen) was achieved. Laying was also possible but often at a lower frequency than normal.When a Wyandotte White hen bearing Rhode Island Red oöcytes was mated with a normal Rhode Island cock, the down of their offspring looked brighter than Rhode Island Red chicken's in one case, but it was subsequently replaced by red-brown feathers according to the genotype.When a Rhode Island Red hen bearing Wyandotte White oöcytes was mated with a normal Wyandotte White cock, the down of their offspring was never in agreement with the genotype. It always showed a black pigment over more or less large areas and, in one case, a red-brown pigment, both of which were present in the foster mother. The origin and the mechanism of such a transfer of pigments are not understood. It might represent merely a temporary effect acting upon the down of the first generation. As far as the comb is concerned, it was always in agreement with the original genotype.

     

The enterotoxin gene (cpe) of Clostridium perfringens can be chromosomal or plasmid-borne

The location of the cpe gene, encoding the enterotoxin responsible for food poisoning in humans, has been studied in a series of enterotoxigenic Ciostridium perfringens strains by means of pulsed field gel electrophoresis of genomic DNA. The cpe gene was found at the same chromosomal locus in strains associated with food poisoning in humans and was shown to be linked to a repetitive sequence, the Hin dlll repeat, and an open reading frame, ORF3, that may be part of an insertion sequence. In contrast, when the strains originated from domesticated livestock cpe was located on a large episome where it was often close to a copy of the transposable element IS 1151. In these cases, the Hin dlll repeat was not linked to the cpe gene although this was generally preceded by ORF3.     

CHILL-COMA TOLERANCE, A MAJOR CLIMATIC ADAPTATION AMONG DROSOPHILA SPECIES

Abstract.— Most drosophilid species can be classified either as temperate or tropical. Adults of species were submitted to a cold treatment (0°C) and then brought back to ambient temperature. They generally exhibited a chill coma and the time needed to recover was measured. We found in a set of 26 temperate species that recovery was rapid (average 1.8 min, range 0.15–4.9). In contrast, a long recovery time (average 56 min, range 24–120) was observed for 48 tropical species. A few species, like Drosophila melanogaster, are cosmopolitan and can proliferate under temperate and tropical climates. In 9 of 10 such species, slight genetic differences were found: a shorter recovery in temperate than in tropical populations. Comparing physiological data to phylogeny suggests that chill‐coma tolerance has been a recurrent adaptation that is selected for in cold climates but tends to disappear under a permanently warm environment. This major climatic adaptation, evidenced in drosophilids, seems to occur in other insect groups also.     

Individual variability in tree allometry determines light resource allocation in forest ecosystems: a hierarchical Bayesian approach

Tree species differences in crown size and shape are often highlighted as key characteristics determining light interception strategies and successional dynamics. The phenotypic plasticity of species in response to light and space availability suggests that intraspecific variability can have potential consequences on light interception and community dynamics. Species crown size varies depending on site characteristics and other factors at the individual level which differ from competition for light and space. These factors, such as individual genetic characteristics, past disturbances or environmental micro-site effects, combine with competition-related phenotypic plasticity to determine the individual variability in crown size. Site and individual variability are typically ignored when considering crown size and light interception by trees, and residual variability is relegated to a residual error term, which is then ignored when studying ecological processes. In the present study, we structured and quantified variability at the species, site, and individual levels for three frequently used tree allometric relations using fixed and random effects in a hierarchical Bayesian framework. We focused on two species: Abies alba (silver fir) and Picea abies (Norway spruce) in nine forest stands of the western Alps. We demonstrated that species had different allometric relations from site to site and that individual variability accounted for a large part of the variation in allometric relations. Using a spatially explicit radiation transmission model on real stands, we showed that individual variability in tree allometry had a substantial impact on light resource allocation in the forest. Individual variability in tree allometry modulates species’ light-intercepting ability. It generates heterogeneous light conditions under the canopy, with high light micro-habitats that may promote the regeneration of light-demanding species and slow down successional dynamics.