Effects of transdermal nicotine on learning, memory, verbal fluency, concentration, and general health in a healthy sample at risk for dementia.

Nicotinic receptor loss has been implicated in the pathogenesis of Alzheimer's disease. The present study investigated the effects of chronic low-dose transdermal nicotine in a cohort of nondemented, healthy volunteers (mean age 63 years). The majority of subjects (85%) had a first-degree relation with dementia. Subjects were tested using a before, during, and after design on a battery of tests known to be sensitive to early cognitive decline. A mixed pattern of results was seen, with significant changes occurring with verbal learning, object learning, delayed recall, and word retrieval. Nicotine had no effect on measures of concentration or psychomotor speed. The effects were most noticeable in subjects at the lower end of baseline test performance on the tasks used. The results are discussed with reference to the relationship between strategic nicotinic receptor loss and measurable psychometric change. The potential therapeutic role of nicotinic agonists in preclinical "at risk" individuals is supported by the results of this study.

Depression in early adolescence: relation to externalising and internalising behaviour.

The relationship between depression, on the one hand, and externalising and internalising behaviour, on the other, in 151 adolescents (79 boys and 72 girls) was examined with respect to the possible moderating role of sex-role stereotyping. The Reynolds Adolescent Depression Scale, the Achenbach Teacher Report Form, and the Australian Sex-Role Scale were used to assess the hypothesis that adolescents adapt to the experience of depression in gender-appropriate ways. A regression analysis indicated that the pattern of relationships was different for boys and girls. The hypothesis was supported for boys and externalising behaviour but not for girls and internalising behaviour.

Shuttling behavior and intracranial self-stimulation reward: behavioral changes as a function of intensity and independence of on/off times.

The correlation between "on" time and "off" time in intracranial self-stimulation shuttling behavior under continuous reinforcement was examined. The results showed that if a tendency for positive trend in the data was accounted for, no consistent correlation could be found between within-trial on time and the succeeding or preceding off time either as a function of intensity or number of trials. However, mean on and off times showed a significant positive correlation at low to moderate intensities. Total charge, total time, and proportion of time on remain relatively constant over a series of trials despite significant changes in on time, off time, and crossing rate. The results indicate the importance of selecting suitable measures in the study of shuttling behavior.

The protease and gag gene products of the human immunodeficiency virus: authentic cleavage and post-translational modification in an insect cell expression system.

Three recombinant baculoviruses which are capable of expressing human immunodeficiency virus (HIV) protease, p55gag, and both products simultaneously in insect cell culture have been constructed. Upon co-infection of cells with the protease and p55gag-expressing viruses, authentic processing of the gag precursor is observed to take place. This processing could be reproduced in vitro using mixtures of cellular lysates containing the expressed proteins. When expressed alone, uncleaved p55gag precursor appears to form retroviral core-like particles within the cytoplasm of infected cells. Metabolic labeling studies of the baculovirus-expressed gag products have demonstrated that p17 is myristylated at its amino terminus, and that p24 is phosphorylated. In these respects, the insect cell system is evidently capable of carrying out post-translational processing resembling that which occurs in authentic HIV-1 replication.