Effects of catecholaminergic drugs on systems of reward and punishment in experiments on cats

A common assumption in special education is that temporal limits for a task should be expanded so that ample time is provided for completing the work. This study describes the opposite strategy of restricting temporal limits to augment academic performance. Three educable retarded children received token reinforcement contingent on the number of correct math problems answered during daily sessions. A reversal design was used to assess the effects of an abrupt reduction in time limits (20-5-20 min) and a graduated sequence of reductions (20-15-10-5-20 min). The graduated sequence resulted in rate increases of correct responding ranging from 125% to 266% and these gains endured when temporal limits were again expanded. In contrast, the abrupt shift produced interfering emotional behaviors and rate decreases in academic performance of 25% to 80%. The findings indicate that systematically restricting temporal limits for an academic task can further enhance the performance of slow learners already maintained by a token system.     

Studies in Germanium Oxide Systems: IV, Phase Equilibria in the System K,O-GeO,

Phase relations in the binary system K₂O-GeO₂ were determined by conventional quenching techniques. Three compounds, K₂O.2GeO₂, 3K₂O.11GeO₂, and K₂O.7GeO₂, exist in the composition range 65 to 100% GeOn. The compound 3K₂O.1lGeO₂ melts congruently at 1055°C, whereas K₂O.2GeO₂ and K₂O.7GeO₂ melt incongruently at 761° and 950°C, respectively. Thermal expansion data for the crystalline compounds are presented. The structure of potassium germanate glasses is discussed.     

Hormonal regulation of sex differentiated parameters in liver nodules from rats treated in the resistant hepatocyte model

Sex differentiation of liver functions has been shown to be attenuated in preneoplastic rat liver nodules. The present study was performed to investigate whether nodules from male rats are to some extent withdrawn from the normal growth hormone (GH) regulation of these functions. Male and female Wistar rats were treated according to a modified resistant hepatocyte model (RH-model), with diethylnitrosamine initiation and promotion with intragastric administration of 2-acetylaminofluorene (2-AAF) combined with partial hepatectomy (PH). Eleven months post-initiation male rats were treated with either human (hGH) or bovine growth hormone (bGH) or ovine prolactin (oPRL) by continuous infusion for 1 week. The mRNA expression of a number of genes known to be sex differentiated in liver from adult control rats was compared in nodular and surrounding tissue from nodule-bearing male, female and hormone-treated male rats. The basal mRNA expression of the female-predominant cytochrome P4502C12 (CYP2C12) was increased and the male-predominant CYP2C11 was decreased in liver nodules from male rats compared with the surrounding liver. Expression of the prolactin receptor (PRL-r; female > male) and the steroid 5 alpha-reductase (female > male) genes was decreased in male nodules, whereas no difference was observed with respect to GH-receptor (GH-r; female > male) expression in nodules versus surrounding tissue. Early nodules obtained from males treated according to the original RH-model (dietary 2-AAF, 0.02%) and isolated 2 weeks after completion of the 2-AAF/PH treatment showed significantly lower GH-r mRNA levels than the total liver tissue. In hepatocellular carcinomas from hormonally unmanipulated males 11 months post-initiation the decrease in PRL-r expression was even more pronounced than in the nodules and a significant decrease in GH-r expression was seen. In female nodules the only significant difference with respect to the sex differentiated parameters was a lower 5 alpha-reductase expression than in the surrounding tissue. Continuous infusion of both hGH and bGH feminized the expression of all the sex differentiated genes in male tissues and eliminated the previously detected differences between nodules and surrounding tissue. oPRL also eliminated the differences between nodules and surrounding tissue in males and partly feminized the expression of both the 5 alpha-reductase and the PRL-r genes.(ABSTRACT TRUNCATED AT 400 WORDS)