Perturbateurs endocriniens et écosystèmes

Hormonal imbalances, sexual changes and unusual behaviours are observed in wildlife. Some chemicals are implicated as endocrine disruptors (EDCs). Their dispersal into ecosphere allows them to reach biotopes isolated of emission sources and they accumulate in organisms and they cause alterations in biological functions (reprotoxicity, immunotoxicity, etc.). Beyond the individual, the community equilibrium is endangered with a potential impact on biodiversity. The organohalogen substances are historically concerned. Despite the prohibition of organochlorine pesticides and PCBs, they persist in aquatic and terrestrial habitats. But the “emerging substances” are also dangerous. Numerous examples of endocrine disruption in animal communities are described. The imposex in female of marine gastropods related to tributyltin (TBT) is one of the earliest known events. The feminization of fish in the estuary of the Seine, the hermaphroditism of some amphibians and the strange behaviour of birds, are famous facts. The cumulative effects are of concern to wild populations. These are mix of pollutants or the concomitancy of other global changes, the decline of polar bears or seals from the Baltic Sea proves it. In conclusion, endocrine disruption jeopardizes all natural biological systems and contributes in loss of biological diversity by reducing the number of sensitive species and making them vulnerable, considering the global extinction risk.     

Le système protéolytique de Penicillium roqueforti: II - Purification et propriétés de la protéase acide

An extracellular protease has been isolated from the culture medium of Penicillium roqueforti. The enzyme was purified by precipitation with ammonium sulfate, filtration on Bio-gel P 100 columns and chromatography on D.E.A.E.-cellulose columns The purified preparation was homogenous by gel filtration on Bio-gel P 60 and electrophoretical analysis at pH 9.0 and 5.0.The protease exhibited the properties of an acid protease: the optimum pH was 3.5 for casein or hemoglobin hydrolysis and for bovine trypsinogen activation; at 40°C, the enzyme is most stable in the range of pH 3.5 to 5.5; the optimum temperatures was 50°C.E.D.T.A., D.F.P. and sulfhydryl reagents induced no inhibition.The enzyme exhibited a milk clotting activity that was fifty times weaker that the activity of rennin. Its molecular weight, estimated by gel filtration was 33 400. Amino acid composition is: Lys₁₅, His₂, Arg₁, Trp₅, Asp₃₃, Thr₂₇, Glu₁₆, Pro₁₀, Gly₄₀, Ala₂₅, Cys₂, Val₂₁, Ile₂₀, Leu₂₁, Tyr₁₄, Phe₁₉.The properties of this protease were closely similar to that of P. janthinellum and Aspergillus oryzae.     

Caractères et évolution des enzymes chitinolytiques chez les vertébrés infèrieurs

The activity of chitinases extracted from various organs of different fish, amphibians and reptiles was estimated as a function of pH by using “native” chitin as substrate. Three types of chitinase activity were recorded, suggesting the existence of three different chitinase types: Type 1: (optimum pH; 4.5, no activity at pH 1.0) was found in various organs, such as intestine, pyloric caeca, pancreas, liver, spleen, etc.); Type IIa: (optimum pH; 3.0, weak activity at pH 1.0) was obtained from the gastric mucosa of fish and one species of urodele; Type IIb: (optimum pH; 3.0, strong activity at pH 1.0) was found in the gastric mucosa of reptiles and batrachian anura. Chitinase activity appears to be adapted to the pH of the digestive fluids. A tentative scheme is presented of chitinase evolution among lower vertebrates.     

Les phospholipides: relation entre leur nature et i''evolution des systèmes endomembranaires chez les champignons filamenteux

Phospholipids of two filamentous fungi, Mucor mucedo and Aspergillus ochraceus, cultivated under identical conditions, were separated by column chromatography, thin layer chromatography and identified by autoradiography. They contain mainly phosphatidylcholine (PC), phosphatidy ethanolamine (PE) and phosphatidylserine (PS). PE. is the most abundant molecule of the phospholipids in these two moulds, but the ratio PE/PC = 3,4 for M.mucedo while it is only 1.3 for A.ochraceus. Linoleic acid is more important in the latter fungus. Correlations between the phosphatidylcholine content, its evolution, the structural stage of a microorganism and the complexity of the membranary systems are suggested.     

Préparation et dosage immunonéphélémétrique du fibrinogène de lapin

Pure rabbit fibrinogen was prepared by a method involving two ammonium sulfate precipitations, one 2 M phosphate buffer precipitation, one DEAE cellulose chromatography and lastly one Sepharose 6 B chromatography. The aminoacid composition was determined and an immunonephelemetric assay was proposed. This assay allowed an accurate determination of fibrinogen concentration in a rabbit with inflammatory reaction.     

Biosynthèse de la cellulose bacterienne deutériée: étude par R. M. N. du taux d'incorporation et de la localisation du deutérium

The use of the NMR spectra (250 MHz) of cellulose triacetate allows the determination of the percentage of deuterium bonded to each of the six carbon atoms of the monomer residue (except for H_?1 and one of the protons bonded to C₆ where the signals overlap). Deuterated derivatives of D -glucose and/or deuterated water were used for the biosynthesis of bacterial cellulose by Acetobacter xylinum. Analysis of NMR spectra of acetylated samples gives the following results. About 90% of the protons linked to C₁ and C₆ come from the D -glucose used in the nutrition medium, whereas 10% are exchanged with other sources of protons. Over 40% of the protons linked to C₂, C₃, C₄, and C₅ arise from the water of the nutrition medium. Discrepancies between results of biosynthesis from deuterated water and from deuterated D -glucose can only be explained if more than one enzymatic process is involved in the biosynthesis of bacterial cellulose.