Age-dependent population diffusion with external constraint

We present a simple model for age dependent population diffusion when the dynamics is submitted to external constraints. Existence, uniqueness and dependence on the parameters of the solution are discussed.This work has been done within the framework of the cultural agreement between the Universities of Bordeaux and Rome     

Substitution of the flavin chromophore with lipophilic side chains: A novel membrane redox label

Summary The synthesis of amphiphilic flavins substituted with C₁₈-hydrocarbon sidechains in positions 3, 5, 7, 8 and 10 is described. 3-, 7-, and 10-amphiflavins were obtained by new total syntheses. Furthermore, 3-amphiflavin was obtained by C₁₈-alkylation of natural flavin in the oxidized state, whereas 5-amphi(dihydro)flavin was obtained by alkylation under reducing conditions.In the course of these studies, a novel, selective oxidation reaction was found taking place with the 8-methyl group of natural flavins. In this way lumiflavin and riboflavin derivatives could be converted directly to flavin-8-nor-8-carboxylic acids or the corresponding alkyl esters.The new flavin derivatives lend themselves for incorporation into lipid vesicles, thus yielding the basis for model studies of anisotropic flavin chemistry and redox transfer through membranes, as described in the concomitant paper (Schmidt, W., Hemmerich, P. 1981).J. Membrane Biol. 59:129. The new flavins are characterized by means of absorption, fluorescence, and proton nuclear magnetic resonance spectroscopy.     

Influence du traitement sylvicole sur la flore forestiere: Cas de la futaie et du taillis-sous-futaie

Summary In a previous study, 772 floristics relevés, made in a large forest on calcareous soils (north-east France), had been treated by factorial analysis of correspondences in order to establish a site typology. The third axis separated chiefly Fagus and Quercus, which are very common in the forest, and various other ligneous or herbaceous species (see fig. 1). Two groups of relevés, homogeneous as for edaphic conditions, were choosen, having a significant position on this axis (with either positive or negative values). From this, floristic tables have been elaborated; they show clearly the influence of silvi culture (here high forest or coppice-with-standards) on part of both ligneous and herbaceous flora. Considering plant sociology, it appears that treating a stand as a coppice-with-standards can convert a Melico-Fagetum typicum (Eu-Fagion) into a Querceto Carpinetum typicum (Fraxino-Carpinion), and a Carici-Fagetum (Cephalanthero-Fagion) into a Querceto-Carpinetum primuletosum (Fraxino-Carpinion). Fortunately a large number of species are not influenced by the silviculture; this allows the identification of isopotential sites. Possible ecological causes are briefly discussed.

Nomenclature suivant: P. Fournier, 1961. Les quatre flores de France. Edition P. Le Chevalier, Paris. 1154 p.     

On the nature of biochemically generated hydroxyl radicals. Studies using the bleaching of p-nitrosodimethylaniline as a direct assay method.

An efficient scavenger for radiolytically generated hydroxyl (OH) radicals, p-nitrosodimethylaniline, was used to try to substantiate the presence of this oxygen radical species in several biochemical systems. Most of these systems which were investigated had previously been assumed to generate OH radicals, e.g. the autoxidation of 6-hydroxydopamine, the hydroxylating system NADH/phenazine methosulfate, and the oxidation of xanthine or acetaldehyde by xanthine oxidase. We did not observe inhibition of the bleaching of p-nitrosodimethylaniline in oxygenated solutions by other scavengers of OH radicals nor, in the case of xanthine/xanthine oxidase, by catalase and superoxide dismutase. We therefore conclude that, under biochemical conditions as opposed to radiolysis or photolysis, no freely diffusable OH radicals are formed. Rather, a strongly oxidizing OH-analogous complex is considered to represent the p-nitrosodimethylaniline-detectable species formed under these conditions.     

Separation and biological properties of Phaseolus vulgaris isolectins

Two isolectins (L₄E₀-PHA and L₀E₄-PHA) from red kidney beans (Phaseolus vulgaris) were isolated by affinity chromatography on immobilized thyroglobulin and by chromatography on hydroxyapatite. The L₄E₀-PHA siolectin was not retarded on the affinity column and was eluted from the hydroxyapatite column with a 0.1 M Phosphate buffer. This isolectin had no erythroagglutinating activity but had high lymphoagglutinating and lymphocyte stimulating activities. The L₀E₄-PHA isolectin was adsorbed on the affinity column and was eluted from the hydroxyapatite column with a 0.25 M Phosphate buffer. This isolectin has a high erythroagglutinating activity, a very low lymphoagglutinating activity and no lymphocyte stimulating activity. These two isolectins are shown however to be closely related with respect to their oligomeric structure and reactivity towards anti-PHA antibodies. The lack of mitogenic activity of the L₀E₄-PHA isolectin suggests that in the other isolectins, the E monomer is not responsible for their mitogenic activity and that the membrane glycoproteins, which contain the E monomer — specific oligosaccharide, are not involved in the process inducing mitosis.     

Composition en lipides et acides gras de deux esèces de Taphrina parasites de Prunus domestica

Four strains of both Taphrina pruni and T. institiae were cultivated under identical conditions and and lipids and fatty acids were quantitatively analysed at two stages of their development. Tri- and diglycerides are the major neutral lipids in both species. Phosphatidylcholine and phosphatidylethanolamine are the most abundant polar lipids. Qualitatively, the two species show identical fatty acid contents, except for margaric acid (17:0) which was only found in Taphrine pruni. Quantitatively there are several differences: palmitoleic acid (16:1) occurs in reasonable amounts regularly and only in Taphrina pruni. The ratios 16:0/18:0 and 18:1/18:2 are generally higher for T. insititiae whereas the degree of unsaturation of fatty acids is higher in the former. The results are discussed with regard to data on other fungal species.