The idiographic study of inconsistent condom use behavior of persons living with HIV.

A pilot study was conducted to assess the feasibility of using, in a multiply disadvantaged population, an electronic daily diary to test hypotheses linking affective states to variability in psychosocial determinants of condom use. Twenty-one mostly non-Caucasian individuals reporting profound economic disadvantage, heavy alcohol use and HIV infection completed a 5-7 minute interactive voice response (IVR) telephone-based survey daily for three weeks. Potentially affect-related within-person variability was observed in HIV-preventive attitudes, intentions and self-efficacy. Surprisingly, in this sample, HIV-preventive attitudes, intentions and self-efficacy exhibited as much, or greater, variability within persons as compared to between persons. Positive affect was found to significantly co-vary with self-efficacy to practice safer sex B=0.20, t((199))=2.14, p=0.03. For each unit increase in daily positive affect, daily self-efficacy increased by 0.20. Results suggest that a daily diary methodology is both feasible in a high-risk population and may offer new insights into understanding unprotected sexual behavior.

Design enhancement of a solid ankle-foot orthosis: real-time contact pressures evaluation.

The purpose of our study was to evaluate all contact pressures between the molded ankle-foot orthosis (MAFO) and the subject during activities of daily living. The MAFOs studied are used clinically to reduce plantar contact pressures associated with foot ulcers in adult neuropathic diabetic subjects, alleviating abnormal pressures by redistributing them to low-pressure plantar regions. While effective, MAFOs are often not used by the subject due to weight and comfort issues. An understanding of the contact pressures between the subject and the orthosis is a first step in improving basic MAFO design. Four nonimpaired, young adult males were tested in this study. A right-side MAFO was custom-molded and fitted for each subject by the same orthotist. Real-time pressures were obtained for the entire contact area using the F-Scan pressure measurement system. The data obtained demonstrated high contact pressures along the metatarsals of the foot, around the heel and ankle, and adjacent to the strap attachment sites. No contact pressures were noted along the posterior calf region during any of the activities performed. These data suggest the calf region would be a suitable site for material removal for weight reduction and increased comfort, especially in warm weather. In addition, these data may be useful to orthotists in improving the basic design and to researchers as a starting point for performing complex finite element analysis on the MAFO.

White matter abnormalities in mobility-impaired older persons.

OBJECTIVE: To investigate the relationship between white matter abnormalities and impairment of gait and balance in older persons. METHODS: Quantitative MRI was used to evaluate the brain tissue compartments of 28 older individuals separated into normal and impaired groups on the basis of mobility performance testing using the Short Physical Performance Battery. In addition, individuals were tested on six indices of gait and balance. For imaging data, segmentation of intracranial volume into four tissue classes was performed using template-driven segmentation, in which signal-intensity-based statistical tissue classification is refined using a digital brain atlas as anatomic template. RESULTS: Both decreased white matter volume, which was age-related, and increased white matter signal abnormalities, which were not age-related, were observed in the mobility-impaired group compared with the control subjects. The average volume of white matter signal abnormalities for impaired individuals was nearly double that of control subjects. CONCLUSIONS: This cross-sectional study suggests that decreased white matter volume is age-related, whereas increased white matter signal abnormalities are most likely to occur as a result of disease. Both of these changes are independently associated with impaired mobility in older persons and therefore likely to be additive factors of motor disability.

Stance perturbation-evoked potentials in old people with poor gait and balance.

OBJECTIVE: Cerebral cortical potentials can be evoked by stance perturbation, and there is speculation that they represent the activation of supraspinal centers in preparation for the control and coordination of motor movements that maintain balance. We sought to determine if these potentials differed in old people at risk of falls. METHODS: Cortical potentials were generated by the sudden forward translation of a weight-bearing platform in 8 healthy young subjects and in 33 old subjects stratified by their functional capacity. Dependent measures were compared with non-parametric tests of significance. RESULTS: Perturbing the stance of young subjects produced a biphasic scalp potential centered at the vertex with an early positive peak at 60 ms and a larger, 45 microV, negative peak at 123 ms. In old subjects the response was delayed and the vertex-negative component was smaller and bifid. The interval between the two components of the negative peak was prolonged in a subgroup of old subjects with reduced mobility. CONCLUSIONS: Delays in sensory conduction may play a role in subsequent maladaptive motor responses to stance perturbation that can result in falls and injury in old people.

Quantitative analysis of long-term potentiation in the hippocampal dentate gyrus of the freely-moving 15-day-old rat.

The magnitude and duration of long-term potentiation (LTP) of perforant path/dentate granule cell synapses was examined in freely moving rats beginning at 15 days of age. Measures of dentate granule cell population EPSP slope and population spike amplitude (PSA) obtained before and after tetanization were used to evaluate the level of LTP. Tetanization resulted in significant enhancement of both the population EPSP slope (approximately +75%) and PSA (approximately +40%) measures. This enhancement was maintained without significant change for 18 h, after which both measures began a steady and continuous rise. Daily input/output response measures from age-matched nontetanized animals were used to factor out enhancement related to normal development. Under this schema, tetanization-induced enhancement of both EPSP slope and PSA measures decayed slowly, beginning 18-24 h after tetanization, returning to baseline 5 days after tetanization. Enhancement obtained from 90-day-old animals decayed to baseline 24 h after tetanization. The longer duration of LTP obtained from preweanlings is discussed with regard to the development of inhibitory systems modulating granule cell excitability.

Maturation of long-term potentiation in the hippocampal dentate gyrus of the freely moving rat.

The ability of the perforant path/dentate granule cell synapse of the hippocampal formation to establish and maintain enhanced levels of synaptic transmission in response to tetanization (long-term potentiation, LTP) was investigated in freely moving rats at 15, 30, and 90 days of age. Measures of 1) the slope of the population excitatory postsynaptic potential (EPSP), and 2) the population spike amplitude (PSA) obtained before, and at several times following tetanization, were used to evaluate the magnitude and duration of LTP as a function of age. Significant enhancement of both EPSP slope and PSA measures was obtained from animals of all three ages in response to perforant path tetanization. The initial degree of enhancement was essentially the same across the age groups, ranging from +27% to +38% of pretetanization levels for EPSP slope measures and +60% to +75% of pretetanization levels for PSA measures, obtained 15 min after tetanization. The duration of this enhancement obtained from animals of the preweaning group was significantly longer than that obtained from either 30- or 90-day-old animals. Enhanced measures of both EPSP slope and PSA decayed to baseline levels in these older animals 18 to 24 h after tetanization, while animals tetanized at 15 days of age maintained potentiated levels of both measures for a period of 5 days following tetanization. Tetanization of 15-day-old animals resulted in a significant reduction in the latency to EPSP onset without affecting the time-based relationships among the other measured parameters, which included latency of the population spike onset, population spike minimum, and population spike offset.(ABSTRACT TRUNCATED AT 250 WORDS)