Reliability of psychophysiological responding as a function of trait anxiety.

This study examined the temporal stability of three psychophysiological responses (frontal electromyographic activity, hand surface temperature, and heart rate) recorded over four sessions (days 1, 2, 8, and 28) on 34 subjects, 17 with high Spielberger Trait Anxiety Inventory scores and 17 with low scores. Each session consisted of a 20-minute adaptation period, a baseline condition, and two stressors (one cognitive, the other physical). Two forms of reliability coefficients were employed, intraclass correlations and Pearson Product Moment; the two types of reliability coefficients arrived at the same conclusions. Results indicated that reliability coefficients for the two anxiety groups did not differ on frontal EMG or heart rate responses; however, hand surface temperature responding was considerably less reliable for high anxious individuals than low anxious individuals. Reliability coefficients on absolute scores were, for the most part, reliable. Treating the responses as relative measures (percent change from baseline or simple change scores from baseline) produced smaller and less reliable coefficients. Magnitudes of the three physiological responses did not significantly differ as a function of high or low trait anxiety. Findings are discussed in terms of their clinical, as well as basic psychophysiological, importance.

Temporal stability of psychophysiological stress profiles: a re-analysis using intraclass correlation coefficients.

This is a re-analysis of data from a previous study which examined the temporal stability of three psychophysiological responses [frontal electromyographic activity (EMG), hand surface temperature, and heart rate]. Each response was recorded on 64 subjects over four sessions, each of which consisted of a 20-min, adaptation period, a baseline condition, and two stressors (one cognitive, the other physical). Rather than using Pearson product-moment correlations, as nearly all psychophysiological test-retest reliability studies have, we have now analyzed the data using intraclass correlation coefficients. This type of correlation allows one to incorporate more than two test-retest values on the same subjects. Analysis indicated that, with the exception of EMG during the physical stressor, the absolute values of the responses had quite significant reliability (.70 or greater). Treating the responses as relative measures (percent change from baseline or simple change scores from baseline) produced smaller and frequently less stable coefficients. It is concluded that statistical estimates of psychophysiological response reliability are functions of the design and particular reliability analysis employed.

Does HIV "piggyback" on CD4-like surface proteins of sperm, viruses, and bacteria? Implications for co-transmission, cellular tropism and the induction of autoimmunity in AIDS.

Coinfections of human immunodeficiency virus (HIV), EBV, and HTLV or sperm proteins act synergistically to enhance infectivity and replication and expand cellular tropism. While some aspects of these synergisms are understood, others are not. We have found that membrane or surface proteins of CMV, HTLV, EBV and sperm proteins share large regions of similarity with the CD4 protein of T-helper lymphocytes. Since HIV uses CD4 as a receptor, it may bind to CD4 homologues on CMV, HTLV, EBV or sperm proteins. HIV could then "piggyback" with these viruses into cells with which it normally has no tropism. Similarly, HIV may expand the cellular tropism of CMV, or EBV. Such a piggyback mechanism may provide insight into the formation or presentation of CD4-like antigens from CMV, HTLV, EBV and sperm proteins with class II MHC-like antigens on HIV (gp160 and Nef proteins) and may break immunological tolerance, inducing the autoimmunity observed against both CD4+ and class II MHC+ T cells in AIDS patients.

Differences in cyclophosphamide-induced suppression of cricket predation in selectively bred strains of taste-aversion prone and resistant rats.

Cyclophosphamide-induced conditioned suppression of cricket predation was observed in taste-aversion-prone (TAP) but not in taste-aversion-resistant (TAR) rats. These TAP and TAR strains had been selectively bred for efficient or inefficient acquisition of cyclophosphamide-induced saccharin taste aversions (TAs). Equivalent preconditioning cricket predation was practiced by nonfasted subjects of both strains. TAR rats that ate crickets before a cyclophosphamide injection were thereafter voracious predators as were saline-injected and pseudoconditioning controls of both strains. However, conditioned TAP rats subsequently displayed a marked suppression of cricket predation. Predation can provide a deprivation-free and species-natural consummatory response for studies of strain differences in TA conditionability of TAP and TAR rats. In addition, the present results indicate that TAP and TAR strain differences in TA conditionability are not restricted to the saccharin solution that was the conditioned stimulus basis of prior strain development.

A Monte Carlo simulation of convective dispersion in the large airways.

A numerical model describing the local interactions between convection and diffusion in the first 11 generations (0 to 10) of the human bronchial tree is presented. The model, based on a Monte Carlo procedure, is used to investigate the effects of four velocity profiles: (i) parabolic, (ii) asymmetrical, (iii) asymmetrical with swirling and (iv) flat. Behavior was investigated for three diffusivities: (i) 0.75 cm2/s (He/air), (ii) 0.25 cm2/s (N2/O2) and (iii) 0.1 cm2/s (SF6/air) on the convection-diffusion interaction. The results of these simulations showed that 'Taylor dispersion' is an important effect, with respect to tracer segregation, and that it is of major significance only in the largest airways. By generation 10, molecular diffusion begins to dominate over Taylor dispersion. It was also found that use of a parabolic velocity profile, or application of the Gill-Sburamanian dispersion theory seriously overestimates axial dispersion. On the other hand, the use of a flat velocity profile underestimates dispersion.

Response-contingent stimuli and DRL performance after septal lesions in rats.

An experiment was conducted to assess the effectiveness of providing response-contingent stimuli in improving the performance of rats with septal lesions on a DRL schedule of reinforcement. Groups of operated and control animals were given no stimulus, a light flash, or footshock in conjunction with all noncriterion lever presses. Footshock, but not light, was found to substantially ameliorate the lesion-induced DRL deficit. Improved schedule efficiency appeared to result from the punishing aspects of the shock and not to a response-feedback function.