Deuterium oxide effects upon three parameters characterizing the activity of glycerol-extracted muscle: phosphate release, ATP-induced shortening, and 22Na+ distribution

ATP splitting activity is progressively reduced with increasing heavy water (D2)) concentration. In contrast, sarcomere shorteining inhibition produced by D2O does not significantly depend on its concentration. Even at low concentration, the presence of D2O does reduce the excessive accumulation of radioactive sodium within glycerinated frog muscle. These heavy water effects on muscular contraction and soidum distribution can be interpreted to indicate adsorbed water within the cells. Evaluation of these experimental results in terms of Gibbs free enthalpy of binding at the adsorption sites of D20 or H20 is in good agreement with the data in the literature.     

Ultrastructure de l'œuf de Triatoma infestans Klug

Summary The thick rigid chorion of the egg of Triatoma secreted by the follicle cells shows two porous layers: an aerial layer in the exochorion, an alveolar one in the endochorion. The anterior part of the eggshell is closed up by an operculum which is heaved up by the hatching larva. The operculum has no alveolar layer. The air enters through the numerous holes of the shell surface into the aerial layer and through the micropyles into the alveolar layer. The egg has no respiratory plastron.The follicle cells produce also a vitelline envelope whose structure shows a rapid condensation at fertilization time. During its development the embryo secretes two layers: serosal and embryonic cuticle.At high humidities, at low temperatures the egg is able to increase its weight during the early stages of embryogenesis, and this increase stops when the serosal cuticle is secreted. In a dry atmosphere the egg loses water but can develop if the temperature is higher than 20°C.The little permeability of the egg is related to the structure of its envelopes. The chorion and the vitelline envelope prevent the water from getting out of the egg. The serosal cuticle seems to be opposed to the penetration of the water into the egg. The role of the embryonic cuticle is probably limited in the transit of water.

Nous remercions Messieurs les Professeurs Maillet et Folliot qui ont mis le microscope R.C.A. à notre disposition, Madame Allo et Mademoiselle Le Gac, technicienne au microscope à balayage J.S.M. S1, pour leur collaboration technique.     

Phylogenetic relationships of annual and perennial wild rice: probing by direct DNA sequencing

Summary The phylogenetic relationships between Asian wild rice strains were analyzed by direct sequencing of PCR-amplified DNA fragments. The sequence of three introns located in the phytochrome gene was determined for eight strains of the Asian wild rice, Oryza rufipogon, and one strain of the related African species, Oryza longistaminata. The number of nucleotide substitutions per site between various strains within a single species, O. rufipogon, ranged between 0.0017 and 0.0050, while those between two related species, O. rufipogon and O. longistaminate, were 0.043–0.049 (23–26 within 532 bp). Taken together with the sequence differences of the 10-kDa prolamin gene, a model is proposed for the phylogenetic relationships and evolutionary history of annuals and perennials within O. rufipogon.     

Polychromatism in eggshell or domestic quail (Coturnix coturnix japonica). IV. Porphyrin biosynthesis in uteri of phenotypes belonging to the dominant form]

With the introduction of delta-aminolevulinic acid, uterin extracts, in vitro, can synthesize porphyrins (uroporphyrin, 62%; coproporphyrin, 27%; and protoporphyrin, 11%). At the stage where the uterus contains a white egg, various phenotypes in the dominant form are capable of synthesizing with the introduction of delta-aminolevulinic acid, the same quantity of porphyrins. These results are interpreted, assuming the existence of differences in the activity of the enzymes involved during the laying cycle.     

1, 2-propanediol from the Pacific Ocean fish Ctenochaetus striatus

(±) 1, 2-propanediol has been isolated from the fish Ctenochaetus striatus. Obtained a first time as the free alcohol with a high yield, it has been found in smaller amount and esterified, in specimens of a different location. The possible origin of this compound is discussed.     

Valuing environmental functions in developing countries

The interface between ecology and economics is the valuation of environmental goods, services and attributes. The total economic value of an ecosystem is derived by estimating monetary values for it's direct use, indirect use, option and non-use values. Recent advances have been made in the economic valuation of direct, option and non-use values. Much less attention has been paid to measuring the indirect use value provided by environmental functions. These values may be particularly significant in developing countries. This paper details the challenge presented by valuing environmental functions to ecologists and economists and synthesizes the methodological advances that have occurred. Using tropical forests, wetlands and biodiversity as illustrations, the application of this methodology to valuing the functions of complex natural systems is investigated and existing studies reviewed. Conclusions on further research are presented.