The chlorination of surface waters is known to form trihalomethanes. Therefore, chlorine dioxide (C1O2) is being considered as an alternative disinfectant. This study was designed to determine the effect of chlorine dioxide and its metabolites, chlorite (C1O-2) and chlorate (C1O-3), on rat fetuses exposed in utero. Female rats were administered C1O2 at 0, 1, 10 and 100 mg 1(-1) and C1O-2 or C1O-3 at 1 and 10 mg 1(-1) daily in the drinking water for 2 1/2 months prior to the throughout gestation. Rats were killed on day 20 and fetuses examined for external, skeletal and visceral malformations. Slight decreases in weight gain during pregnancy were seen in the C1O2 administered groups. A significant dose-response relationship in the decreases of the numbers of implants and live fetuses were observed in the C1O2 groups. Although there were increased incidences of resorptions in the C1O-2 and C1O-3 groups, no statistically significant increase was found in the groups. Fetal weight was significantly increased in the 100 mg 1(-1) C1O2 group. Also, fetal length was increased in the 10 mg 1(-1) C1O-2 and C1O-3 treatment groups. Skeletal defects, such as incompletely ossified or missing sternebrae, rudimentary ribs and incompletely ossified skull bones were increased in all treatment groups, but none were significantly different from the control group. A few cases of hypoplastic kidney, hydronephrosis and dextrocardia were observed in the treatment groups.
Chlorine interacts with organic materials in surface water, leading to the formation of trihalomethanes, that may be carcinogenic. Studies were conducted to investigate the pharmacodynamics and toxicity of chlorine (0, 1, 10, 100 mg 1(-1] in drinking water in rats. Blood glutathione (GSH) was significantly decreased after 6 months of treatment and this effect persisted after 1 year treatment in the 10 and 100 mg 1(-1) groups. Treatment groups showed an increase in blood osmotic fragility. The acute study revealed that GSH was significantly decreased as early as 30 min after the administration of 30 and 120 micrograms chlorine. The effect was maintained up to 1 h. However, the GSH level returned to control value by 2 h. Blood osmotic fragility of the acute exposure was incresed after 15 min and was without change after 30 min. Of the hematological parameters only the red blood cell count and hematocrit were significantly decreased in the 100 mg 1(-1) group after 3 months of treatment. An examination of blood chloroform content in all the groups after 4, 6, 9 and 12 months showed no significant difference compared with the control. Chlorine administered chronically in drinking water for 3 months increased the incorporation of 3H-thymidine into nuclei of rat kidney and testes in the 100 mg 1(-1) group.
The kinetics of chloride were studied in Sprague-Dawley rats following the oral administration of Na36Cl. The half-life for 36Cl- absorption from plasma was 19.2 h corresponding to a rate constant of 0.0361 h-1, while the half-life for 36Cl- elimination from plasma was 51.9 h, corresponding to a rate constant of 0.0134 h-1. At 120 h, radioactivity was highest in plasma, followed by kidney, lung, stomach, and spleen, and the lowest activity was observed in fat. Plasma and packed cells contained almost the same concentration of 36Cl-. Plasma protein binding of chloride was significantly higher than liver protein binding. Subcellular distribution in liver fractions revealed that most of the 36Cl- was located in the cytosolic fraction. The excretion of chloride occurred primarily by the kidney.
Monochloramine (NH2Cl) is under consideration as an alternative to chlorine as a disinfectant in public water supplies, to avoid trihalomethanes formation. This study was conducted to investigate the toxicity of NH2Cl (0, 1, 10, 100 mg/l) in drinking water. Glutathione (GSH) content in rat blood was decreased significantly after 4 mo treatment, and the decreases were consistent throughout the treatment period. Treatment groups showed a slight increase in blood osmotic fragility. After acute administration (3 ml) of 20 and 40 mg NH2Cl/l, blood GSH levels were increased as early as 15 min and the increases were consistent up to 1 h. After 2 h exposure, however, the GSH content returned to the control value. At 3 mo, red-blood-cell count and hematocrit were decreased significantly, while after 10 mo treatment significant decreases in hemoglobin concentration and mean corpuscular hemoglobin were observed. Monochloramine administered in drinking water for 3 mo increased the incorporation of [3H]thymidine into nuclei of rat kidney and spleen in the 1- and 10-mg/l groups, while the incorporation in testes was increased only in the 100-mg/l group. The body weight of rats was decreased significantly in the highest treatment group after 3 mo treatment, and the decrease persisted throughout the period studied. An examination of blood chloroform content in all the groups after 4, 6, 9, and 12 mo showed no significant changes compared to the control.
Enzymatic hydrolysis of xylan, the principal constituent of hemicellulose in most biomass residues, has been recognized as being important in the practical utilization of these substrates to produce food and fuel. Research efforts on xylan hydrolysis have been fewer than those on cellulose hydrolysis but economic viability of biomass-based processes depends on effective bioconversion of the xylan component as well as the cellulose. Xylanases are capable of hydrolysis of xylan giving high yields of xylose without the by-product formation associated with acid hydrolysis. 'Trichoderma reesei has received a great deal of attention as the organism with the highest potential for large scale production of cellulases. Under controlled fermentation conditions, T. reesei mutants have been reported to produce as much as 20 mg/mL extracellular protein' which includes cellulases (endoglucanase, cellobiohydrolase, Pglucosidase), xylanase, laminarinase, amylase, acid phosphatase, etc.' Little attention has been given to the xylanases of T. rersei which, present in the same crude enzyme preparation as the cellulases, could contribute significantly to the overall saccharification of unrefined biomass.Hemicellulose is degraded by the synergistic action of endo-1,4-P-xylanase, exo-1 ,4+-xylanase and exoglycosidases such as P-xylosidase. In our previous study,4 a significant increase in the secretion of xylanase was observed when T. reesei hypersecretory strain RL-P37 was cultivated on lactose at 37°C. The objective of this study was to determine the effects of temperature on the secretion of xylanase in Trichoderma reesei, which could have important implications in fermentation optimization. MATERIALS AND METHODS 7: reesei Strains and Culture ConditionsFor spore production, wild type T. reesei QM6a was grown on potato dextrose agar (Difco) and hypersecretory mutant RL-P37 grown on Vogel's salts5 containing 0.1% proteose peptone (Difco), 1% cellulose (Solka Floc, BW * To whom all correspondence should be addressed.200, Brown Co., Berlin, NH), and 1.5% agar. Submerged fermentation studies were carried out in Vogel's medium containing 1% lactose or xylan (Sigma). Cultures were inoculated with 14-day-old spores at a final concentration of 2 X lo5 spores/mL and incubated with shaking (250 rpm) at 25°C. After 24 h germination, the cultures were split into three flasks and incubated for an additional 72 h at 25, 30, or 37°C. At the end of incubation, the mycelia were harvested and the supernatant was assayed for secreted enzymes and protein. Dry weight was determined by washing the mycelia with distilled water and drying to constant weight at 80°C. Enzyme AssaysEndoglucanase was assayed by the methods of Mandels and co-workers6 in 0.05M citrate buffer, pH 4.8, at 50°C. Xylanase activity was determined using 0.5% xylan as substrate according to Suh and c o -~o r k e r s .~ Since the end products of xylan were not identified in this report, xylanase inferring here includes the activities of both endoand exo-xylanases. The P-xylosidase was ...
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