Kinetics of reaction of (nitrotyrosyl)cytochrome c with ligands.

The reaction of [nitrotyrosyl]cytochrome c with ligands was studied by stopped-flow techniques. At pH 7.0 the reaction with imidazole shows two distinct phases, one fast phase being concentration-dependent and a slow phase being concentration-independent. The results are consistent with the existence of two forms of [nitrotyrosyl]cytochrome c in solutions [Schejter et al. (1970) Biochemistry 9, 5118-5122]; form I, the smaller fraction, seems to be responsible for the slow first-order process.     

Sex-related differences in food and water intake and body weight changes with prolonged administration of adrenaline in the rat

Male and female rats were treated with different high doses of adrenaline for five days. Their food and water intakes and body weights were recorded. A considerable sex-difference was found on the 5th day in body weights and plasma glucose concentrations. Males had higher plasma glucose and lost more weight than females. Females ate and drank more than males throughout the experiment. The adrenaline-sensitivity of females decreased by the third day but it did not change in males. These data suggest that females are able to activate mechanisms that compensate the effects of high adrenaline levels while males are not, or their compensatory mechanisms are less efficient.     

Xylose anaerobic conversion by open-mixed cultures

Xylose is, after glucose, the dominant sugar in agricultural wastes. In anaerobic environments, carbohydrates are converted into volatile fatty acids and alcohols. These can be used as building blocks in biotechnological or chemical processes, e.g., to produce bioplastics. In this study, xylose fermentation by mixed microbial cultures was investigated and compared with glucose under the same conditions. The product spectrum obtained with both substrates was comparable. It was observed that, in the case of xylose, a higher fraction of the carbon was converted into catabolic products (butyrate, acetate, and ethanol) and the biomass yield was approximately 20% lower than on glucose, 0.16 versus 0.21 Cmol X/Cmol S. This lower yield is likely related to the need of an extra ATP during xylose uptake. When submitted to a pulse of glucose, the population cultivated on xylose could instantaneously convert the glucose. No substrate preference was observed when glucose and xylose were fed simultaneously to the continuously operated bioreactor.     

Interrelationships between the development of the gastric cytoprotective effects of prostacyclin, atropine, cimetidine and the gastric mucosal superoxide dismutase activity in rats

Gastric mucosal damage was produced by the intragastric administration of 96% ethanol or 0.6 M HCl. The cytoprotective doses of prostacyclin (PGI2) (5 micrograms/kg), atropine (0.025 mg/kg) or cimetidine (2.5 mg/kg) were given intraperitoneally 30 min before the administration of the necrotizing agents. The animals were killed 1 hr later. The number and severity of gastric mucosal lesions (ulcer) were recorded. At the time of the sacrifice of the animals, superoxide dismutase (SOD) was prepared from the gastric fundic mucosa and its activity was measured. It was found that PGI2 (5 micrograms/kg), atropine (0.025 mg/kg) and cimetidine (2.5 mg/kg) significantly decreased the number and severity of gastric mucosal lesions (ulcers) produced by the intragastric administration of 96% ethanol a 0.6 M HCl, PGI2, atropine, cimetidine, given in cytoprotective doses, significantly mounted the ethanol-induced increase of gastric mucosal SOD activity; PGI2, atropine, cimetidine, given them in cytoprotective doses significantly shunted the HCl-induced decrease of gastric mucosal SOD activity. It has been concluded that; chemically different cytoprotective agents (PGI2, atropine, cimetidine) give rise to similar tendencies in the changes of gastric mucosal SOD activity; both the significant decrease (in the ethanol-model) and the significant increase (in the HCl-model) of this enzyme seem to be involved in the development of gastric mucosal protection by PGI2, atropine and cimetidine.     

Critical threshold meal size and molt initiation in Rhodnius prolixus

The molting process and body growth in Rhodnius prolixus (Hemiptera: Reduviidae) (Ståhl, 1859) are significantly influenced by the availability and quality of food. Based on the body weight of each stage, the present study provides estimates of a potential critical weight threshold required for molt initiation in R. prolixus. In addition, a new measure given by the area under the weight curve is proposed, which encapsulates both body weight and time. It is shown that this measure is consistent with the data, and allows the estimation of a pre‐refractory period (i.e. the time interval between the moment at which the critical weight threshold is reached and the moment when no further meals are accepted). The present analysis estimates the critical weight threshold as 1.6, 5.3, 12.9, 42.0 and 97.0 mg for stages 1–5, respectively, whereas the values of the area under the curve threshold as 5, 16, 31.2, 159.7 and 329.9 mg days for stages 1–5, respectively. The results of the present study confirm the existence of a weight‐dependent mechanism for the initiation of molting in R. prolixus.