Les genres Costa et Paleocosta (Ostracodes) du paléogène aquitain: Les structures de populations,témoins des paléoenvironnements. Description de Paleocosta aquitanica nov. sp.

Costa tricostata (Reuss) and Paleocosta aquitanicanov. sp. are polymorph species of the Paleogene Aquitaine. In this study, their constituent forms are both described and illustrated. These are particularly ornamented and show Mesogene affinites; their geographical distribution area is limited within the Aquitaine Basin and Bay of Biscaye.In bathyal environments, the spatial distribution of the Costa, reveals three domains characterized by an increase of faunal density and polymorphism and a morpho- functional adaptation through the strengthening of the shell architecture. We attribute these changes to the effects of an adaptative strategy of the populations within an environment of increasing dynamic activity either near drainage channels and/or accumulation zones of terrigenous material continentally-derived, or within highly intensive upwelling zones.In less shallow environments and/or more close tooceanic influences, the Costa and Paleocosta populations flourish but lose their polymorphism. They announce the ecologic limit of the species.     

Agrobacterium tumefaciens T-DNA gene 6b stimulates rol-induced root formation, permits growth at high auxin concentrations and increases root size

Summary All Agrobacterium tumefaciens strains studied up to now transfer an active 6b gene to plant cells. However, the role of this gene in natural tumour induction is unknown. Various effects of 6b on plant cell growth have been described, but the precise mechanism by which 6b causes these effects has not been elucidated. Earlier experiments indicated that the 6b gene might increase auxin sensitivity as do the A. rhizogenes rol genes. The 6b gene from Tm4 (T-6b) was therefore compared with the rolB and rolABC genes. Although T-6b was unable to induce root formation, it strongly interfered with root induction and root elongation. In rolABC/T-6b coinfection experiments on carrots, T-6b-transformed cells stimulated root outgrowth of rolABC-transformed cells, indicating that the biologically active T-6b product is diffusible. Carrot rolABC roots containing the T6b gene rapidly developed into unorganized calli. Nicotiana rustica roots with rolABC and T-6b continued their development, but became very large. Fragments of such roots formed callus at -naphthaleneacetic acid concentrations which inhibited growth of rolABC and normal root fragments, suggesting that the role of 6b genes in natural tumour induction may be to reduce the inhibitory effects of high auxin levels and to keep cells in an undifferentiated state.     

Correlated extinctions, colonizations and population fluctuations in a highly connected ringlet butterfly metapopulation

 The persistence of metapopulations is likely to be highly dependent on whether population dynamics are correlated among habitat patches as a result of migration between patches and spatially-correlated environmental stochasticity (weather effects). We examined whether population dynamics of the ringlet butterfly, Aphantopus hyperantus, were synchronous in an area of approximately 0.5 km², with respect to extinction, colonization and population fluctuations. Monks Wood Butterfly Monitoring Scheme transect count data from 1973 to 1995, revealed (A) a major environmental perturbation, the drought of 1976, which caused synchronized extinctions of A. hyperantus in subsequent years, (B) synchronized recolonization in years following the large number of apparent extinctions, and (C) population changes by A. hyperantus were highly correlated in many of the 14 sections of the transect, presumably reflecting similar responses to environmental stochasticity, and the exchange of individuals among sections. However, extinction and population synchrony depended on habitat type. Following the 1976 drought, A. hyperantus apparently became extinct from the most open and most shady habitats it occupied, with some persistence in habitats of intermediate shading, thus showing retraction to core populations in central parts of an environmental gradient, albeit with an average shift to relatively open habitat. Populations at extreme ends of the environmental gradient occupied by A. hyperantus fluctuated least synchronously, suggesting a potential buffering effect of habitat heterogeneity, but this was not crucial to survival after the 1976 drought. Thus, not all habitats are equally important to persistence. Correlated temporal dynamics, variation in habitat quality and the interaction between habitat quality and temporal environmental stochasticity are important determinants of metapopulation persistence and should be incorporated in metapopulation models. Received: 26 April 1996 / Accepted: 17 July 1996     

Effects of chair-restraint on gastrointestinal transit time and colonic fermentation in male rhesus monkey (Macaca mulatta)

Abstract: The incidence of an 18 day chair-restraint on the digestive physiology of male rhesus monkey was investigated for space research purposes, comparing four trained restraint subjects with two vivarium controls. Chair-restraint induced a 2.5-fold acceleration of the gastrointestinal transit time, which persisted throughout the 7 day postrestraint period, and an increase of the fecal dry matter content, which mean value rose from 40.7% to 69.6%. Fecal pH remained unaltered throughout the experiment. Modifications of fermentative metabolites produced by the colonic microflora and excreted through the breath (hydrogen and methane) or in the feces (short chain fatty acids and ammonia) could not be reliably related to chair-restraint and probably involved side-stress factors. On the whole, alterations due to chair-restraint are shown to be different from those reported in the literature, following a modification of the dietary composition. These data may help to predict the alterations of digestive physiology likely to occur in immobilized human patients.     

Amylase production by three Lactobacillus strains isolated from chicken crop

Three amylolytic Lactobacillus strains designated LEM 220, LEM 207 and LEM 202 were isolated from the chicken crop. They belonged to the subgenus Thermobacterium. Strain LEM 220 resembled Lact. acidophilus. Amylase production was more abundant in cells grown in media containing amylopectin or starch than in media containing glucose or maltose. Optimum pH and temperature of the amylase were 5.5 and 55°C respectively. Hydrolysis of amylopectin gave maltose, maltotriose and small amounts of glucose. Strain LEM 207 also resembled Lact. acidophilus , but differed from strain 220. It had a lower amylase activity. Optimum pH and temperature of the amylase were 6.4 and 40°C, respectively, and hydrolysis of amylopectin gave maltose, maltotriose and carbohydrates higher than maltopentaose. Strain LEM 202 was similar to Lact. vitelinus. It had the lowest amylase activity which was increased only in presence of maltose. Amylase properties were similar to those of LEM 220.     

Pachytene analysis in a 17;21 reciprocal translocation carrier: role of the acrocentric chromosomes in male sterility

Summary Pachytene analysis was undertaken in an infertile male, heterozygous for a 17;21 reciprocal translocation. The quadrivalent was identified by its configuration and chromomere pattern. A non-random association was found between the quadrivalent and the sex vesicle in 77% of the pachytene nuclei analysed. In 13.1% of the cells the contact with the sex vesicle was established by the terminal chromomere of the two chromosomes 21; in 63.9% of the cells, the entire region of the breakpoints was completely hidden by the sex vesicle. In some nuclei asynapsis was found in the region of the breakpoints. The nature of the contact between the quadrivalent and the sex vesicle is discussed in this paper. It is proposed that the acrocentric chromosome favours the contact between the quadrivalent and the sex vesicle, and increases the risk of sterility in male carriers of Robertsonian translocations and of reciprocal translocations involving one acrocentric chromosome.     

IFN-gamma and Fas ligand are required for graft-versus-tumor activity against renal cell carcinoma in the absence of lethal graft-versus-host disease

To determine the mechanisms of graft-versus-tumor (GVT) activity in the absence of graft-versus-host disease (GVHD) against a solid tumor, we established two allogeneic bone marrow transplantation models with a murine renal cell carcinoma (RENCA). The addition of 0.3 x 10(6) donor CD8(+) T cells to the allograft increased the survival of tumor-bearing mice without causing GVHD. The analysis of CD8(+) T cells deficient in cytotoxic molecules demonstrated that anti-RENCA activity is dependent on IFN-gamma and Fas ligand (FasL), but does not require soluble or membrane-bound TNF-alpha, perforin, or TRAIL. Recipients of IFN-gamma(-/-) CD8(+) T cells are unable to reject RENCA compared with recipients of wild-type CD8(+) T cells and, importantly, neither group develops severe GVHD. IFN-gamma(-/-) CD8(+) T cells derived from transplanted mice are less able to kill RENCA cells in vitro, while pretreatment of RENCA cells with IFN-gamma enhances class I and FasL expression and rescues the lytic capacity of IFN-gamma(-/-) CD8(+) T cells. These results demonstrate that the addition of low numbers of selected donor CD8(+) T cells to the allograft can mediate GVT activity without lethal GVHD against murine renal cell carcinoma, and this GVT activity is dependent on IFN-gamma and FasL.     

Adoptive transfer of T-cell precursors enhances T-cell reconstitution after allogeneic hematopoietic stem cell transplantation

Immunoincompetence after allogeneic hematopoietic stem cell transplantation (HSCT) affects in particular the T-cell lineage and is associated with an increased risk for infections, graft failure and malignant relapse. To generate large numbers of T-cell precursors for adoptive therapy, we cultured mouse hematopoietic stem cells (HSCs) in vitro on OP9 mouse stromal cells expressing the Notch-1 ligand Delta-like-1 (OP9-DL1). We infused these cells, together with T-cell-depleted mouse bone marrow or purified HSCs, into lethally irradiated allogeneic recipients and determined their effect on T-cell reconstitution after transplantation. Recipients of OP9-DL1-derived T-cell precursors showed increased thymic cellularity and substantially improved donor T-cell chimerism (versus recipients of bone marrow or HSCs only). OP9-DL1-derived T-cell precursors gave rise to host-tolerant CD4+ and CD8+ populations with normal T-cell antigen receptor repertoires, cytokine secretion and proliferative responses to antigen. Administration of OP9-DL1-derived T-cell precursors increased resistance to infection with Listeria monocytogenes and mediated significant graft-versus-tumor (GVT) activity but not graft-versus-host disease (GVHD). We conclude that the adoptive transfer of OP9-DL1-derived T-cell precursors markedly enhances T-cell reconstitution after transplantation, resulting in GVT activity without GVHD.