Modulation of a lectin insecticidal activity by carbohydrates.

Lectins from plants present an insecticidal activity most probably through their carbohydrate binding properties; as a consequence, their toxicity should vary with the presence of a competitive sugar in the ingested food. In order to test this hypothesis, we performed competition experiments between insecticidal activity and carbohydrate binding. For this purpose, we used a lectin from Lathyrus ochrus and the specific carbohydrate for this protein, glucose. In toxicological tests with Drosophila melanogaster, we observed a decrease of lectin toxicity when glucose was added to the larva-rearing medium. This result suggests that the toxicity of the lectin is correlated to its ability to bind sugar in the insect digestive tract and stresses the importance of sugar composition of the nutriment used for toxicological testing of lectins or in genetically modified plants.

Synthetic hispidin, a PKC inhibitor, is more cytotoxic toward cancer cells than normal cells in vitro.

The trypanocidal activity of naturally occurring 6-(3,4-dihydroxystyryl)-4-hydroxy-2-pyrone (hispidin) prompted us to examine its cytotoxic activity toward normal and cancerous cells in culture. Hispidin synthesized in our laboratory to a high degree of purity (checked by 1H and 13C NMR spectroscopy) was shown to be cytotoxic (between 10(-3) mol/L and 10(-7) mol/L) toward normal human MRC-5 fibroblasts, human cancerous keratinocytes (SCL-1 cell line), and human cancerous pancreatic duct cells (Capan-1 cell line). Interestingly, addition of hispidin in three successive doses (between 10(-5) mol/L and 10(-7) mol/L) led to a 100-fold increase in activity with an enhanced activity on cancer cells compared to normal cells (50%). Synthetic hispidin was found to inhibit isoform beta of protein kinase C (IC50 of 2 x 10(-6) mol/L), but not E. coli and placental type XV alkaline phosphatases. The enhanced activity of hispidin toward the cancerous cell lines is discussed.

A water-soluble beta-D-glucan from Boletus erythropus.

The main component of a water extract of Boletus erythropus fruiting bodies is a M(r) 10(6) glucan. The use of classical structural analysis and HMQC (heteronuclear multiple quantum coherence) NMR experiments indicates a (1-->3) linked beta-D-glucan structure with a single glucose residue attached to O-6 of the main chain and a branching frequency of 1/3.

Insecticidal properties of mushroom and toadstool carpophores.

In order to find compounds with insecticidal or antifeedant properties from mushrooms and toadstools, a wide screening was undertaken using the non-mycophagous Drosophila melanogaster as a model insect. Powdered fruit bodies of edible and poisonous mushrooms were incorporated with the Drosophila's rearing medium, and their development was observed. Among the 175 different species of fungi tested, 79 were found to inhibit insect development, hence making the isolation of new compounds look hopeful.

Purification and characterization of a novel phospholipid transfer protein from filamentous fungi.

1. We have isolated from mycelia of Mucor mucedo, a filamentous fungus, a phospholipid transfer protein. 2. The purification steps were gel filtration, hydroxyapatite chromatography, blue affinity column and fast protein liquid chromatography on anion exchanger. 3. A purified protein was obtained with a molecular mass of 24 kDa and a pI of 5.05 and its N-terminal sequence was established. 4. This protein transfers phosphatidylinositol, as well as phosphatidylcholine and phosphatidylethanolamine.

[Enhancement of resistance of mice Toxoplasma gondii by 2 polysaccharides beta 1-3, beta 1-6 (PSAT and Scleroglucan)]. / Augmentation de la résistance des souris à Toxoplasma gondii par deux polysaccharides beta 1-3, beta 1-6 (le PSAT et le Scléroglucane).

The protective effect of PSAT and Scleroglucan (beta 1-3, beta 1-6 polysaccharides), has been studied in mice infected with different strains of Toxoplasma gondii (RH, attenuated RH or Prugniaud strains). Intramuscular or intravenous administration of PSAT before infection of mice by the attenuated RH strain, resulted in a significant enhancement of survival: 100% of survival in the treated group, compared to 33% in controls and 50% in mice pretreated with Scleroglucan (10 mg/kg, intravenously). In contrast, there was no difference in the survival rate between the group treated with PSAT (1 mg/kg, IV) and the control in mice infected with the virulent RH strain: all mice died between day 7 and day 8. In mice infected with 15 cysts of the Prugniaud strain a decrease in the chemiluminescence (CL) of peritoneal macrophages and of the number of cysts in the brain of mice were observed in mice treated either with PSAT (1 mg/kg, IM) or scleroglucan (10 mg/kg, IM).

Lipid composition of thermophilic moulds Acremonium alabamensis and Thermomucor indicae-seudaticae.

The total lipid content of Acremonium alabamensis and Thermomucor indicae-seudaticae ranged 2.6-7.3 and 8.5-13.0% of dry mycelium, respectively during development. Neutral lipid fraction increased during growth while polar and phospholipids declined. Both moulds contained palmitic, oleic, linoleic and palmitoleic acids as major fatty acid components in lipids. Degree of unsaturation of lipids of A. alabamensis was greater than that of T. indicae-seudaticae. Neutral lipids were more unsaturated than the polar lipids. The ratio of unsaturation index of polar lipids to neutral lipids was either one or less than one. The principal phospholipids of these moulds were phosphatidyl choline, phosphatidyl ethanolamine and phosphatidic acid. However, phosphatidic acid was not found in very high amounts as observed in Humicola grisea var. thermoidea.

Bioconversion and binding of sterols by thermophilic moulds.

None of the fourteen thermophilic moulds was able to break down the aliphatic side chain of sterols, viz. cholesterol, lanosterol, sitosterol, and stigmasterol so as to yield 4-androstene-3,17-dione, 1,4-androstadiene-3,17-dione and progesterone. In Acremonium alabamensis and Talaromyces emersonii, cholestenone was detected as a product of fermentation of cholesterol whereas the former yielded stigmastadienone from stigmasterol and sitosterol. Lanosterol appeared to be resistant to fungal bioconversion. All the thermophilic moulds exhibited avidity for binding sterols to the mycelium, but the ability to bind sterol seemed to depend upon the nature of the organism and the sterol.

[Lipid metabolism in Aspergillus versicolor (Vuill.) Tiragoschi. Relation to biogenesis of sterigmatocystin]. / Metabolisme lipidique chez l'Aspergillus versicolor (Vuill.) Tiraboschi. Relations avec la biogénèse de la stérigmatocystine

Aspergillus versicolor is cultivated in a synthetic medium for 22 days. Bioproduction of lipids and sterigmatocystin are compared. The fatty acids of the neutral lipid and polar lipids fractions are mainly: C 16:0, C 18:0, C 18:1, C 18:2, C 18:3. Maximal yields of dry weight, neutral lipids and sterigmatocystin occur, respectively, on the 4th, the 7th and the 20th days. These results and their comparison with other works emphasize that a fall of concentration in lipids precedes the phase of highest concentration in secondary metabolites of polyketide type; it appears that fats and particularly palmitic acid are present in biogenesis of these derivatives.