Revue rapide: 381 sujets impuissants,explores en 2 ans,dont 207 avec Prostaglandine E1

During the last two years, 381 impotent patients have been tested, 174 with papaverine and 207 with prostaglandin E1 (PGE1: Alprostadil). More positive responses were obtained using PGE1 (76.8%) than papaverine (44.8%), and some patients whose response to an initial PGE1 test was negative demonstrated a positive effect after a second injection. Two non-responders to PGE1 showed a positive response to papaverine+phentolamine. Tolerance of PGE1 was extremely good, provoking fewer prolonged erections than papaverine. Pain following intracavernosal injection of PGE1 was distressing in 10% of cases, all young men with psychogenic impotence. A therapeutic trial of repeated injections, carried out in 49 selected patients with mild organic dysfunction but strong psychogenic inhibition, typically showed a rapid clinical improvement. Moreover, 16 patients with cavernosal sclerosis and vascular impotence who were treated by injections two or three months apart (instead of having a prosthetic implant) showed a recovery of sexual activity. Consequently, during these two years only 35 patients (9.1%) were treated surgically, 21 by the implantation of hydraulic prostheses. The significant benefits of PGE1, especially the ease of self-administration, demonstrate the need for new therapeutic trials.     

Biosynthesis of bacillomycin D by Bacillus subtilis. Evidence for amino acid-activating enzymes by the use of affinity chromatography.

Bacillomycin D is an antifungal lipopeptide produced by B. subtilis. The formation of the peptidyl bonds of bacillomycin D occurs non-ribosomally, as demonstrated by the use of chloramphenicol, an inhibitor of protein biosynthesis. Amino acid-activating enzymes were found in B. subtilis cell lysates purified by affinity chromatography on a gel containing L-Pro, an amino acid of bacillomycin D. Presence of ATP during this purification increases the binding of enzymatic proteins and their activity. An enzyme, with an apparent molecular weight of 230 kDa, catalyzed ATP-PPi exchange reactions, which were mediated by specific amino acids, corresponding to a partial sequence of bacillomycin D.     

Interactions of surfactin,a biosurfactant fromBacillus subtilis,with inorganic cations

Summary The properties of surfactin, a biosurfactant lipopeptide, were highly modified in the presence of inorganic cations. The micellization of surfactin was favoured by monovalent and, especially by divalent cations with a modification of the molecular area at the air-water interface. Haemolysis of erythrocytes by surfactin was enhanced by low concentrations of divalent cations with an increase of the binding of the lipopeptide to membrane. Inorganic ions induced conformational rearrangements probably due to ion-surfactin associations which modify the surface-active properties.     

Characterization of the multiple forms of β-xylanase produced by a Streptomyces sp. growing on lignocellulose

Summary Streptomyces sp. strain EC10 degraded efficiently the hemicellulose fraction of wheat straw. Three forms of -xylanases detected in the culture filtrate were purified by precipipation with ammonium sulphate, chromatography on DEAE-Sephadex A-50 and gel filtration on Sephadex G-100. The three purified enzymes (X _ia , X _ib and X _ii ) were homogeneous by polyacrylamide gel electrophoresis. The enzymes were typical non-debranching endo--xylanases (1,4--d-xyla xylanohydrolases; E.C.3.2.1.8) with respective relative molecular weights of 32,000, 22,000 and 21,000 and isoelectric points of 6.8, 8.9 and 5.2. The enzymes were highly specific for xylans and showed optimal activity at pH 7.0–8.0 and 60°C. The preparations were completely free from cellulolytic activity (endoglucanase) and showed high thermal stability. No synergy between the three enzymes was detected for complete xylan hydrolysis of deacetylated arabino- and glucuronoxylans.Offprint requests:to: M. J. Penninckx     

In situ spectroradiometric estimation of microalgal biomass in first-year sea ice

Summary First- and multi-year sea ice are colonized by microalgae, whose biomass modifies the spectral distribution of underice downwelling irradiance. It is proposed that an index of algal biomass in the first-year ice may be derived from the ratio of underice irradiance at a wavelength where absorption by chlorophyll a is high to a wavelength where absorption by the photosynthetic pigments is low and transmission through the ice is high. In southeastern Hudson Bay (Canadian Arctic), the irradiance ratio (671540 nm) accounts for 55% of the variance in chlorophyll a, indicating that the in situ biomass of algae in first-year ice can be estimated from spectral measurements of underice downwelling irradiance.Contribution to the programme of GIROQ (Groupe interuniversitaire de recherches océanographiques du Québec)     

Oxysterol activation of arachidonic acid release and protaglindin E2 biosynthesis in NRK 49F cells is partially dependent on protein kinase activity

We previously demonstrated that the oxysterol potentiation of arachidonic acid release and prostaglandin biosynthesis induced by foetal calf serum activation of normal rat kidney (NRK) cells (fibroblastic clone 49F) was not related to a direct effect of oxysterols on cell free Ca²⁺ level. Since both Ca²⁺ variations and protein C are involved in arachidonic acid release in some models, we looked for a possible modulation by protein C in the oxysterol effect on arachidonic acid release. We show that when the phorbol ester 12-O-tetradecanoyl-phorbol-13acetate (TPA), a protein kinase C activator, was added to the culture medium, the oxyterol effect on arachidonic acid release and prostaglandin synthesis clearly increased. Moreover, the effect of TPA was dose-dependent and TPA EC₅₀ (4 × 10⁻⁹ M) was unchanged in the presence of the oxysterol. Preincubation of cells with TPA for 24 h prevented the arachidonic acid release induced by TPA alone, whereas the oxysterol effect was decreased but not abolished. In the absence of serum, TPA and ionomycin added together induced the same noticeable (arachidonic acid) release and PGE₂ synthesis as serum alone. Nevertheless, the potentiating effect of cholest-5-ene-3β,25-diol was much higher when serum itself was used to activate NRK cells than it was in the present serum-mimicking experimental conditions. Thus, the presence of growth factors is probably required to obtain a full oxysterol effect. We conclude that the oxysterol effect was synergistic with, but not fully dependent on, protein kinase C and Ca²⁺ ion fluxes, therefore oxysterols could affed earlier events triggered by serum growth factor binding to their cell membrane receptors.     

Analysis of nuclear sugar-binding components in undifferentiated and in vitro differentiated human promyelocytic leukemia cells (HL60)

The nuclear sugar-binding components (i.e., lectinlike molecules) were analyzed using isolated and membrane-depleted nuclei after incubation in the presence of fluorescein-labeled neoglycoproteins. This analysis was performed before and during the in vitro differentiation of HL60 cells into monocytes by PMA treatment and into granulocytes by DMSO treatment. The nucleoli of undifferentiated and differentiated HL60 cells were not labeled, unlike the nucleoli of other mammalian cells studied so far. This peculiarity allowed us to quantitatively analyze by flow cytometry the changes in the lectin activity associated with the extranucleolar territories enriched in ribonucleoprotein complexes. The neoglycoprotein binding was found to be significantly lower in differentiated than in undifferentiated cells. The decrease in neoglycoprotein binding was observed within the first 24 h of DMSO or PMA treatment, just before the arrest of DNA synthesis. Taking into account that the granulocytic differentiation required 72 h of chemical treatment, the extra-nucleolar lectins might be involved in modulation of the DNA synthesis rather than in phenotypic differentiation. These data are discussed in an attempt to reconcile the association of lectins with RNP complexes and their possible involvement in modulation of HL60 cell proliferation.     

The conformation of single-stranded nucleic acids tDNA versus tRNA

Conformational analyses using the single-strand-specific nuclease from mung bean and restriction endonucleases have been performed on a series of DNA fragments related to the sequence of the yeast initiator tRNA(Met). Mung bean nuclease cleaves DNA fragments exclusively in some, but not all, single-stranded regions as predicted by RNA secondary structural rules. Comparison of cleavage patterns of yeast initiator tRNA(Met), tDNA(Met) (a DNA oligomer having the sequence of tRNA(Met] and the anti-tDNA(Met) (the complement of tDNA(Met] suggests that the conformation of the three molecules is very similar. Furthermore, both tDNA and anti-tDNA are cleaved by HhaI and CfoI restriction endonucleases at two GCG/C sites which would be in double-stranded regions (the acceptor and dihydrouridine stem), if the two molecules adopt the tRNA cloverleaf structure. On the other hand, minor cleavage products show that the core region, i.e. the extra loop area, is slightly more exposed in tDNA and in anti-tDNA than in tRNA. Therefore, we submit that the global conformation of nucleic acids is primarily dictated by the interaction of purine and pyrimidine bases with atoms and functional groups common to both RNA and DNA. In this view the 2'-hydroxyl group, in tRNA at least, is an auxiliary structural feature whose role is limited to fostering local interactions, which increase the stability of a given conformation.     

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