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Biomedical subjects

A T Smith

Publications and source records attributed to A T Smith.

151 records · Page 9Linked to original sources
PubMedDate not supplied

Epidemiology of homicide in Allegheny County, Pennsylvania, between 1966-1974 and 1984-1993.

BACKGROUND: We compared homicide death rates and characteristics of homicide victims and perpetrators in 1966-1974, 1984-1990, 1992-1993, and 1996 in Allegheny County, Pennsylvania, in an attempt to detect possible differences in the pattern of homicides. METHODS: Data were obtained from death certificates, coroner's records, police reports and newspapers. RESULTS: In the 1990s the homicide death rate increased for 15- to 24-year-old black men. The rate was 69 per 100,000/year for black men ages 15-24 years from 1966 to 1974 and rose to 275 per 100,000 from 1992 to 1993. Currently, the rates appear to be declining again. Preliminary data from 1996 showed the number of homicide deaths excluding vehicular homicides between 1993 and 1996 to decline from 19 to 8 for white men, from 70 to 42 for black men, from 9 to 3 for white women, and from 13 to 6 for black women with little change in the population (denominator). The dramatic drop from 111 to 61 deaths over a short time is similar to changes across the United State and is characteristic of epidemic rise and fall of homicides in the community. CONCLUSIONS: Between 1966 and 1993 Allegheny County experienced two separate homicide epidemics, one between 1966 and 1976 and the other between 1990 and 1993. Epidemics of homicide occur frequently and have different characteristics. New characteristics of the most recent epidemic of homicide include more homicides out of home, among strangers; less association with alcohol; and multiple perpetrators. Drug-use-associated homicides have also increased. Guns are the primary agents of homicide epidemics.

Adolescent↗
PubMedDate not supplied

Contrast discrimination: a model and a hypothesis concerning the role of cholinergic modulation in contrast perception.

A model of contrast discrimination performance in human observers is developed and then extended to cover effects on performance of anticholinergic drugs. It is shown that it is necessary to assume that neural noise increases at high spatial frequencies in order to provide a satisfactory model of variations in discrimination performance with spatial frequency. The model results are compared with the results of empirical studies in which the effects of the muscarinic antagonist scopolamine (hyoscine) on contrast discrimination performance in human observers are examined. The purpose of the pharmacological work is to test the hypothesis that the differential contrast gain found psychophysically at different spatial frequencies might reflect differential facilitation by extrinsic cholinergic neurons. Contrast discrimination and contrast increment detection are found to be impaired by scopolamine in a manner that depends on both spatial frequency and base contrast. By comparing the empirical data with the predictions of the model, it is concluded that contrast constancy may reflect differential cholinergic modulation.

Acetylcholine↗
PubMedDate not supplied

Pharmacological separation of mechanisms contributing to human contrast sensitivity.

Two basic types of cholinergic receptor have been identified in nervous systems: nicotinic and muscarinic. In the mammalian visual system, the balance of evidence suggests that nicotinic activity is associated primarily with transmission and processing of information while muscarinic activity reflects modulatory influences arising in the brainstem and basal forebrain. We have measured contrast sensitivity functions using a two-alternative forced-choice procedure in young human volunteers with and without administration of nicotine (1.5 mg by buccal absorption) or the muscarinic antagonist scopolamine (1.2 mg orally). Scopolamine elevates contrast-detection thresholds uniformly at all spatial frequencies, consistent with blocking of a nonspecific arousal system. Nicotine, in contrast, improves sensitivity at low spatial frequencies (below about 4 cycle/deg); at higher spatial frequencies sensitivity is, if anything, impaired. Using counterphase gratings, we find that scopolamine elevates thresholds uniformly at all temporal frequencies. Nicotine lowers thresholds at high but not low temporal frequencies. The results obtained with nicotine suggest that contrast sensitivity reflects the activity of two mechanisms, or sets of spatiotemporal filters, that are pharmacologically distinct, the contrast sensitivity function reflecting the envelope of their sensitivities.

Administration, Oral↗
PubMedDate not supplied

Early mobilization versus immobilization in the treatment of lateral ankle sprains.

We conducted a prospective trial at a military medical center to determine which treatment for first-time ankle sprains, early mobilization or immobilization, is more effective. Eighty-two patients with a lateral ankle sprain were randomly selected for one of two treatment groups. The Early Mobilization Group received an elastic wrap for 2 days followed by functional bracing for 8 days. Two days after injury, this group began weight-bearing and an ankle rehabilitation program. Patients in the Immobilization Group were placed in a nonweight-bearing plaster splint for 10 days followed by weight-bearing and the same rehabilitation program. Patients in the Early Mobilization Group had less pain at 3 weeks (57% versus 87%, P = 0.02); otherwise, there were no significant differences between groups in the frequency of residual symptoms. Only one patient in each group had residual symptoms 1 year after injury. Three patients (8%) in each group resprained their ankles. Ten days after injury, patients in the Early Mobilization Group were more likely to be back to full work (54% versus 13%, P < 0.001). We conclude that in first-time lateral ankle sprains, although both immobilization and early mobilization prevent late residual symptoms and ankle instability, early mobilization allows earlier return to work and may be more comfortable for patients.

Absenteeism↗