Degradation of bisphenol A by the lignin-degrading enzyme, manganese peroxidase, produced by the white-rot basidiomycete, Pleurotus ostreatus

Degradation of 2,2-Bis(4-hydroxyphenyl)propane (bisphenol A, BPA), an endocrine-disturbing chemical, by the growing mycelia of the white-rot basidiomycete, Pleurotus ostreatus, was examined. About 80% of BPA initially present decreased in 12 days of culture with this fungus. By in vitro experiments using the lignin-degrading enzyme manganese peroxidase (MnP), BPA was metabolized to phenol, 4-isopropenylphenol, 4-isopropylphenol, and hexestrol. The degradation products of BPA were assumed to be formed by the one-electron oxidation of the substrate.     

Reduction of Feeding by the Variegated Grasshopper, Zonocerus variegatus , Following Infection by the Fungal Pathogen, Metarhizium flavoviride

The effect of infection by the fungal entomopathogen , Metarhizium flavoviride, on feeding by the tropical grasshopper pest , Zonocerus variegatus, was investigated in field - cage studies . A significant reduction in feeding , as indicated by faecal production , was recorded 2 - 3 days after inoculation for a range of spore doses (104 , 105 and 5 105 spores per insect) . This was before any mortality was recorded due to infection . All infected individuals died by day 7 . At this time , faecal production of the treated grasshoppers was equivalent to less than 2 days faecal production by grasshoppers untreated with spores . This reduction in feeding (69 , 71 and 74% total reduction by day 7 in the 104 , 105 and 5 105 doses respectively in comparison to controls) is a substantial contribution to the overall effects of the slow acting pathogen . Furthermore , the rapid reduction in feeding indicated that this effect was not simply due to invasion of the host tissues by the pathogen or production of secondary metabolites . The possibility that reduction in feeding is associated with a behavioural response in which there is a trade - off between host defence and feeding during early stages of infection is discussed     

Inhibition by maltose, isomaltose, and nigerose of the synthesis of high-molecular-weight D-glucans by the D-glucosyltransferases of Streptococcus sobrinus

Two D-glucosyltransferases are produced by Streptococcus sobrinus C211. One (GTF-S) catalyzes the conversion of sucrose into soluble alpha-(1----6)-linked alpha-(1----3)-branched D-glucans, and the other (GTF-I), of sucrose into alpha-(1----3)-linked alpha-(1----6)-branched D-glucans. These enzymes were studied by using maltose, isomaltose, and nigerose as inhibitors. Maltose and isomaltose were found to be competitive inhibitors of GTF-S, whereas nigerose has no effect on GTF-S activity. The Ki values for maltose and isomaltose were determined to be 11 and 15mM, respectively. Maltose, isomaltose, and nigerose competitively inhibit GTF-I. The Ki values for these inhibitors were found to be approximately 0.8, 2.5, and 15mM, respectively. The inhibitory properties of each disaccharide are interpreted in terms of conformational comparisons with sucrose.     

Biosynthesis of the beta-lactam antibiotic, thienamycin, by Streptomyces cattleya

Radioactive- and stable isotope-containing substrates were used to identify the biosynthetic precursors of the beta-lactam antibiotic, thienamycin, in Streptomyces cattleya. Acetate is utilized by the organism to form C(6) and C(7) of the beta-lactam ring. The two carbons of the hydroxyethyl group attached to C(6) are both derived from the methyl of methionine. The cysteaminyl side chain attached to C(2) is derived from cysteine. Selective inhibition of thienamycin and cephamycin C biosynthesis has been achieved either through the addition of metabolic inhibitors or through manipulation of the growth medium. These results suggest that the two beta-lactam antibiotics, thienamycin and cephamycin C, are formed by different biosynthetic pathways.     

Inhibition of the tempe mould, Rhizopus oligosporus, by ammonia

The hyphal extension rate of Rhizopus oligosporus NRRL 2710 was slowed in the presence of 0·42 and 0·84 mmol NH3 l⁻¹ and inhibited by 1·3 mmol l⁻¹. Sporulation was prevented at NH3 concentrations of 0·42 mmol l⁻¹ andabove. There was no evidence of toxicity due to NH⁺₄ at concentrations up to 300 mmol l⁻¹.Independent of the concentrations of NH3 or NH⁺₄, the lower the pH value, in therange 6·0–9·0, the higher was the rate of hyphal extension. It is suggested that accumulationof toxic levels of NH3 could be responsible for the cessation of mould growth in tempe.     

Chemical modification of the calmodulin-stimulated phosphatase, calcineurin, by phenylglyoxal

Chemical modification of calcineurin by phenylglyoxal was used to probe for the presence of arginine at, or in close proximity to, the catalytic site of this phosphatase. Phenylglyoxal inactivated calcineurin with a second-order rate constant of 1.5 M-1 min-1 at pH 7.5 and 30 degrees C. The inactivation reaction was extremely sensitive to Ca2+-induced conformational changes on calcineurin; removal of this metal ion from the reaction medium increased the rate of inactivation by almost 1 order of magnitude. Furthermore, significant protection of calcineurin by ADP was observed only in the presence of Ca2+, which suggests either that distinct sites are modified by phenylglyoxal in the absence and presence of Ca2+ or that the metal ion promotes binding of ADP to calcineurin. Inactivation of calcineurin by phenyl[2-14C]glyoxal resulted in the incorporation of more than 12 eq of the reagent. However, a kinetic analysis of the order of the inactivation reaction and complete protection of calcineurin by p-nitrophenyl phosphate suggest that only one of the modified residues is responsible for the loss of enzymatic activity. Protection of calcineurin by ADP was enhanced severalfold by calmodulin, which correlated well with a calmodulin-stimulated decrease in the Ki for this ligand. Protection of calcineurin from inactivation by phenylglyoxal was also observed in the presence of various other nucleotides; half-maximal protection by these poor substrates and competitive inhibitors was observed at concentrations near their respective inhibition constants. Thus, the results of this modification study indicate that at least 1 arginine residue is essential for the expression of catalytic activity of the calmodulin-regulated phosphatase.     

Reduction, by atropine, of symptomatic shock induced by PGF2 alpha in the dog

Two groups of 5 bitches different in breed, age and size were given a single dose of PGF2 alpha at a dosage of 0.25 and 0.50 mg/kg of body weight respectively. Since the administration of PGF2 alpha is usually associated with a syntomatic shock in the bitch, four bitches per group were additionally treated with a single dose of atropine (0.050 mg/kg). Two of the four bitches were injected with atropina I.M. contemporaneously with the PGF2 alpha and the other two at the beginning of the symptomatology. Both the former and the latter show a marked reduction of symptomatic shock. The AA. discuss the possible use of PGF2 alpha associated to the administration of atropine in the current therapy of some reproductive disorders of the bitch.     

Inhibition, by electro-acupuncture, of the scalp evoked potential induced by painful stimulation of the tooth in man]

Scalp potentials evoked by electrical stimulation of the tooth pulp can be diminished in amplitude by electroacupuncture. This diminution goes generally in inverse with the increase in subjective pain threshold.     

Kinetics of the inactivation of the protein-lipid complex, firefly luciferase, by sodium deoxycholate and its reactivation by phosphatidylcholine

Firefly luciferase has been shown to be a protein-lipid complex. Phospholipids and neutral lipids bound to luciferase have been identified. Sodium deoxycholate rapidly inactivated the enzyme, but an excess of phosphatidylcholine recovered luciferase activity. From the kinetics of inactivation and reactivation, a mechanism for interaction of the enzyme with detergents and phospholipids has been proposed. The substrates ATP and Mg2+ stabilized luciferase during delipidation.     

Transport of phosphorus,nitrogen, and carbon by the Apure River,Venezuela

The concentrations and transport of carbon, nitrogen, and phosphorus were studied in the Apure River, Venezuela, over a period of 21 months. The drainage basin, which is in western Venezuela, encompasses 167,000 kM², most of which has low relief and supports tropical savanna vegetation. Average runoff for the period of study was 361 mm/year. Discharge-weighted mean concentrations were 188 ug/l for total P, 957 ug/l for total N, and 9.8 mg/l for organic C. Annual transport was 0.68 kg· ha^-1· year^-1 for total P, 3.45 kg · ha^-1· year^-1 for total N, and 35.4 kg · ha^-1 · year^-1 for organic C. Particulate matter accounted for 68% of P, 54% of N, and 37% of C transport. The yield of carbon from the Apure watershed agrees well with empirical predictions, based mostly on the temperate zone, for watersheds of similar size and water yield.Seasonal patterns in chemistry are tied strongly to the hydrologic cycle. When the wet season begins, rising water flushes organic matter from side channels and produces a sharp increase in particulate C and N. Particulate P, which is associated more with mineral material, also increases during rising water. All dissolved constituents except inorganic C also increase over the rising-water phase. As the river inundates the floodplain, the concentration of nitrate declines, whereas the concentrations of dissolved organic C and N continue to rise. At high water the floodplain appears to store sediments that are later remobilized. During low water, all fractions except dissolved inorganic C tend to be at minimum concentration.Soluble reactive P, total dissolved P, dissolved inorganic C, and dissolved organic C were successfully modelled as hyperbolic functions of discharge. No significant relationships were found between concentration and discharge for any particulate fraction because the flushing and storage mechanisms affecting these fractions occurred within specific hydrologic phases, rather than as a smooth function of discharge. No significant relationships were found for any nitrogen fraction. For nitrate, and thus for total dissolved N, of which nitrate is a major component, poor conformance to standard models is explained by association of key mechanisms (e.g. uptake) with specific hydrologic phases. Particulate components and nitrate in this sense violate the continuity assumptions implicit in the standard models.