Patient-Physician Pairing: Does Racial and Ethnic Congruity Influence Selection of a Regular Physician?

Many public and private sector efforts are devoted toward increasing the training of physicians from under-represented minority groups, yet little has been documented regarding the association between physicians' racial backgrounds and the patient populations they serve. To address this question, we use 1987 National Medical Expenditure Survey to examine the impact of race/ethnicity on the matching between physician and patients. Our results show that minority patients are significantly more likely to report having a minority physician as their regular doctor. We estimate that minority patients are five times as likely as non-minorities to report that their regular physician is a member of a racial/ethnic minority. This effect is especially pronounced among Hispanics who identify a Hispanic physician as their regular provider 19 times more often than non-minorities. After controlling for other socio-economic factors, both these figures remain significant, but drop by approximately one-half. These results support the notion that minority patients tend to see minority physicians at a disproportional rate independent of other socio-economic factors.     

Magnetic susceptibility measurement of insoluble solids by NMR: Magnetic susceptibility of bone.

Measurements of the volume magnetic susceptibility of solids using the classical Gouy balance approach are hampered by variations in apparent density of the packed powder. In this paper a quantitative NMR measurement of the volume magnetic susceptibility of powdered solids is described and the volume susceptibility of bone is reported. The technique is based on the measurement of changes in incremental linewidth (1/πT₂′) induced in a marker fluid whose susceptibility can be predictably modified by changing the composition, such as by addition of a soluble diamagnetic compound. The spectroscopic linewidth of the marker fluid is determined by the susceptibility difference between the fluid and the suspended solid. Changes in the linewidth are accompanied by bulk magnetic susceptibility induced frequency shifts in the fluid resonance. Correlating the two dependencies allows measurement of the absolute volume susceptibility of the solid. The susceptibility of bovine rib bone was found to be ?0.90 ± 0.02 × ^? 10^?6 (CGS) confirming previous estimates which suggested bone to be more diamagnetic than the marrow constituents. Knowledge of the susceptibility of bone is relevant in view of the growing interest in MRI osteodensitometric techniques.     

Neurochemical mechanisms mediating the behavioral and cognitive effects of nicotine

Data are reviewed, largely from experiments in the authors'laboratory, that suggest three modes of action of systemic nicotine in producing three different types of effect upon behavior and cognitive function. (1) Preexposure of a stimulus without consequence makes it harder subsequently to form associations to that stimulus, a form of selective attention known as latent inhibition. Latent inhibition is blocked by nicotine, an effect that is apparently mediated by a nicotine-induced increase in dopamine release in the nucleus accumbens. (2) A single dose of nicotine proactively increases the partial reinforcement extinction effect measured several weeks later: that is, resistance to extinction is decreased by nicotine in animals that have been trained on a continuous reinforcement schedule, and increased in animals trained on a partial reinforcement schedule. This effect appears to be due to increased synthesis of tyrosine hydroxylase in the cell bodies of noradrenergic neurons in the locus coeruleus, followed by axonal transport to the hippocampus and increased synthesis and release of noradrenaline in that structure. (3) Nicotine improves vigilance in animals with cognitive deficits due to destruction of the forebrain cholinergic projection system, either as a consequence of excitotoxic lesions of the nuclei of origin of this system or after prolonged alcohol consumption; and also in human subjects with Alzheimer's disease (in which this system undergoes degeneration). This effect is most likely due to an action at denervated cholinergic synapses in the hippocampus and neocortex. © 1994 Wiley-Liss, Inc.     

Dietary supplements and nutraceuticals in the management of andrologic disorders.

Dietary supplements and nutraceuticals are commonly used by men with erectile dysfunction, decreased libido, BPH, and concerns about developing prostate cancer. Many preparations do not contain the advertised dosages of the active ingredient or are contaminated. Dietary supplements and nutraceuticals, particularly those addressing erectile dysfunction and libido, need to undergo rigorous testing before they can be wholeheartedly recommended.     

Positive, negative, unknown: assumptions of HIV status among HIV-positive men who have sex with men.

Serosorting (i.e., engaging in unprotected sex with partners known to be of the same serostatus) can be a difficult process for men who have sex with men (MSM) who frequently make assumptions about their partners' serostatus. This process can be further complicated by a partner's dishonesty as well as other individual and contextual factors. The present study specifically examined how assumptions of serostatus made about unknown serostatus partners impact on the sexual behavior of 110 alcohol-abusing HIV-positive MSM. Although previous research has shown that HIV-positive MSM are more likely to serosort with other known HIV-positive men than with known HIV-negative men, our data suggest that unprotected sex behavior may not be specifically driven by whether or not they made assumptions of seroconcordance or serodiscordance. The types of assumptions these HIV-positive MSM made about their unknown status sexual partners and the basis for such assumptions were also examined. Owing to the ambiguities involved in assumptions of a partner's serostatus in sexual encounters, the 'unknown status' partner category is analytically distinct from 'known status' categories, and needs to be more fully explored because of its impact on perceived serosorting, rather than actual serosorting, among HIV-positive men.