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Biomedical subjects

D R McLeod

Publications and source records attributed to D R McLeod.

64 records · Page 4Linked to original sources
PubMed1985

Generalized anxiety disorder.

This article discusses generalized anxiety disorder in terms of its defining characteristics, its relationship to other psychiatric disorders, its psychobiology, and its treatment. Although generalized anxiety disorder is frequently encountered in general practice, it has been less systematically investigated than the more dramatic forms of anxiety disorders such as panic disorder and phobias. It is concluded that although not as sharply defined as implied by DSM-III, generalized anxiety disorder appears to be a useful diagnostic category.

Adrenergic beta-Antagonists↗
PubMed1984

Relative abuse liability of diazepam and oxazepam: behavioral and subjective dose effects.

The effects of diazepam (10-160 mg) and oxazepam (30-480 mg) were studied in volunteers with histories of drug abuse. Oral doses were administered every third day under double-blind and counterbalanced conditions. Dose-effects with area under the time-action curve data (AUC) showed diazepam to be 2.6-5.7-times more potent than oxazepam on various psychomotor, cognitive, staff-rated, and subjective measures. Comparison of relative potencies showed diazepam to be relatively more potent in producing 'liking' than in producing psychomotor and cognitive effects. Diazepam produced greater peak effects than oxazepam on a number of staff- and subject-rated measures, including liking. Onset of effect was more rapid and time to maximal effect was shorter (1-2 h versus 4-12 h) with diazepam than oxazepam, while time to offset of effect was similar for the two drugs. Diazepam was categorized as producing barbiturate-like subjective effects (38.3%) more frequently than was oxazepam (13.8%), while oxazepam was identified as placebo more often than diazepam. Repeated administration of 160 mg diazepam and 480 mg oxazepam showed that AUC liking was greater for diazepam than oxazepam and that tolerance to psychomotor and cognitive effects occurred with oxazepam but not diazepam. This study suggests that diazepam may have a higher abuse liability than oxazepam.

Adult↗
PubMed1984

Comparison of diazepam and oxazepam: preference, liking and extent of abuse.

In a residential hospital research ward setting, the effects of and preference for placebo, oxazepam (480 mg) and diazepam (40, 80 and 160 mg) were studied in human volunteers with histories of sedative drug abuse. Doses p.o. were administered every 3rd day under double-blind conditions. After an initial exposure to the letter-coded test drugs, a series of choice days was scheduled on which subjects chose between two available drug alternatives. Compared with oxazepam, diazepam produced greater liking (area under the time-action curve), peak liking and euphoria and was judged to be of greater monetary street value. Diazepam was categorized as producing barbiturate-like subjective effects more frequently than was oxazepam (54 vs. 21%), whereas oxazepam was identified as placebo more often than diazepam (32 vs. 4%). Diazepam was associated with a more rapid onset of effect than was oxazepam, and this rapid onset was repeatedly cited by subjects in poststudy written comments as being a desirable feature of the drug effect. In choice tests, 80 and 160 mg of diazepam were preferred to 480 mg of oxazepam on 62.5 and 91.7% of the choice tests, respectively. In choice tests between placebo and drug, placebo was never preferred to diazepam; however, placebo was preferred to oxazepam on 21.4% of choice tests. Overall, these results extend previous experimental observations suggesting that diazepam has a higher abuse liability than oxazepam. The results are also compatible with an analysis of epidemiological data showing that diazepam abuse uniformly exceeds oxazepam abuse on seven epidemiological measures of drug abuse.

Adult↗
PubMed1983

Human progressive-ratio performance: maintenance by pentobarbital.

Within a residential research ward, five human volunteers with histories of sedative drug abuse were exposed to progressive-ratio schedules of pentobarbital (200, 400, 600 mg) or placebo self-administration. All doses were letter-coded and administered under double-blind conditions. To obtain a single letter-coded dose, three subjects were required to press a set of buttons a specified number of times and two subjects were required to ride a stationary bicycle for a specified period of time. Only one dose could be obtained per day and the button-pressing or riding requirement for each letter-coded dose was increased over successive sessions until subjects failed to meet the progressive-ratio requirement (i.e., the subject chose not to work for the dose). Drug-effect ratings and subjective measures were taken 2 h after drug administration. Pentobarbital maintained dose-related increases in the maximum progressive-ratio requirement completed, the subject and staff ratings of drug effect, the subject ratings of drug 'liking', and the scores on the PCAG scale of the Addiction Research Center Inventory. The present study suggests that progressive-ratio schedules are sensitive and valid procedures for providing information about the relative reinforcing efficacy of drugs.

Adult↗
PubMed1976

An analysis of rats' drinking-tube contacts under tandem and fixed-interval schedules of food presentation.

Rats' lever presses and drinking-tube contacts were studied under fixed-interval schedules of food presentation and under a tandem schedule composed of three fixed intervals. One group of rats was exposed first to the tandem schedule, next to fixed-interval schedules of comparable interpellet intervals, and once again to the tandem schedule; a second group of rats was exposed first to a fixed-interval and then to the tandem schedule. Under the tandem schedule, lever presses occurred at a higher rate and were more uniformly distributed in time than under the fixed-interval schedule. Tube contacts emitted by rats exposed first to a fixed-interval schedule consisted mostly of tongue contacts, which occurred at a high rate shortly after food; tube contacts emitted by rats exposed first to the tandem schedule consisted mostly of paw contacts, which occurred at a lower rate at times other than shortly after food. Changing the schedule from fixed interval to tandem decreased the frequency of tongue contacts for all rats. Under schedules of food presentation with comparable interpellet intervals, the schedule of food presentation, rather than the rate of food delivery per se, determined the topography and temporal locus of drinking-tube contacts.

Journal Article↗
PubMedDate not supplied

Manifestations and treatment of Schimke immuno-osseous dysplasia: 14 new cases and a review of the literature.

UNLABELLED: Schimke immuno-osseous dysplasia (SIOD) is a rare autosomal recessive spondylo-epiphyseal dysplasia. The characteristic features of SIOD include 1) short stature with hyperpigmented macules and an unusual facies, 2) proteinuria with progressive renal failure, 3) lymphopenia with recurrent infections, and 4) cerebral ischaemia. Although 25 patients have been reported with this disorder, the clinical course and phenotype of SIOD are not well characterized. This report summarizes the clinical findings, course and treatment of reported patients and includes 14 additional patients with SIOD. We emphasize the high incidence of cerebral ischaemia and ocular abnormalities, define the high incidence of thyroid dysfunction and blood cytopenia, and confirm the absence of effective and durable medical therapies. CONCLUSION: Schimke immuno-osseous dysplasia is a multi-system autosomal recessive disorder with variable expression that affects the skeletal, renal, immune, vascular, and haematopoietic systems. Medical therapy is limited especially for more severely affected individuals.

Adolescent↗
PubMedDate not supplied

Generalized anxiety disorder with early and late onset of anxiety symptoms.

Some generalized anxiety disorder (GAD) patients experience subclinical or clinical levels of anxiety before adulthood, whereas others have a later onset. To determine whether patients who experienced subclinical or clinical anxiety in the first two decades of life differed from those with a later onset, we reviewed the history, ratings on various scales, and psychophysiological recordings obtained from 103 GAD patients. Early-onset patients were younger and more likely to develop GAD without a precipitating stressful event. With the exception of depression in the early-onset group, present-state measures did not differentiate the two groups. During childhood, patients in the early-onset group were exposed to more domestic disturbances, experienced more childhood fears, and were more inhibited and socially maladjusted. As adults, they scored higher on trait anxiety and neuroticism, tended to have obsessional traits, were more sensitive in interpersonal relationships, and experienced more marital difficulties. These findings may be explained by (1) constitutional traits that make early-onset GAD patients more vulnerable to stressors; (2) a more disturbed environment during childhood that adversely affects personality development; or (3) a more severe disorder with an early subclinical onset that also affects personality development.

Adult↗