Search PubMed⌕ Search

Biomedical subjects

J D Steinberg

Publications and source records attributed to J D Steinberg.

8 recordsLinked to original sources
PubMed1992

Association of sleep-wake habits in older people with changes in output of circadian pacemaker.

Many elderly people complain of disturbed sleep patterns but there is not evidence that the need to sleep decreases with age; it seems rather that the timing and consolidation of sleep change. We tried to find out whether there is a concurrent change in the output of the circadian pacemaker with age. The phase and amplitude of the pacemaker's output were assessed by continuous measurement of the core body temperature during 40 h of sustained wakefulness under constant behavioural and environmental conditions. 27 young men (18-31 years) were compared with 21 older people (65-85 years; 11 men, 10 women); all were healthy and without sleep complaints. The mean amplitude of the endogenous circadian temperature oscillation (ECA) was 40% greater in young men than in the older group. Older men had a lower mean temperature ECA than older women. The minimum of the endogenous phase of the circadian temperature oscillation (ECP) occurred 1 h 52 min earlier in the older than in the young group. Customary bedtimes and waketimes were also earlier in the older group, as was their daily alertness peak. There was a close correlation between habitual waketime and temperature ECP in young men, which may lose precision with age, especially among women. These findings provide evidence for systematic age-related changes in the output of the human circadian pacemaker. We suggest that these changes may underlie the common complaints of sleep disturbance among elderly people. These changes could reflect the observed age-related deterioration of the hypothalamic nuclei that drive mammalian circadian rhythms.

Adult↗
PubMed1992

Condensing osteitis of the clavicle: magnetic resonance imaging as an adjunct method for differential diagnosis.

Condensing osteitis of the clavicle is a benign disorder leading to osteosclerosis of the medial end of the clavicle. The differential diagnosis between condensing osteitis of the clavicle and ischaemic necrosis of the medial clavicular epiphysis (Friedrich's disease), osteoid osteoma, and low grade osteomyelitis can be difficult. In the case history reported here, magnetic resonance imaging was a useful non-invasive procedure for the diagnosis of condensing osteitis of the clavicle.

Adult↗
PubMed1991

Racial differences in drug response: isoproterenol effects before and after propranolol.

The aim of this study was to determine in young, healthy men the relative contribution of pharmacodynamic factors inherent between two groups known to respond differently to hypertensive therapy. Black (n = 10) and white (n = 10) men received an isoproterenol sensitivity test before and after propranolol (0.1 mg/kg, then 50 micrograms/min). There were greater increases (twofold) in systolic BP following the 1.0- and 1.5-microgram isoproterenol dose (P less than 0.05) in the black group. During propranolol there were no differences in free (1)-propranolol concentrations between the groups; however, propranolol decreased resting heart rate in the white group more than in the black group (P less than 0.05). Cardiac index decreased less in the black group compared to the white group (P less than 0.05). Following the second isoproterenol challenge, there again were greater increases in systolic BP in the black group at both the 10- and the 20-micrograms isoproterenol dose (P less than 0.05). Our study has highlighted the importance of cross-racial studies in evaluating drug effects.

Adult↗
PubMed1991

Influence of subject age on the inhibition of oxidative metabolism by ciprofloxacin.

Case reports suggest that the magnitude of inhibition of oxidative metabolism produced by ciprofloxacin may be greater in elderly subjects. We examined the effect of oral ciprofloxacin on antipyrine disposition in 13 young (ages, 23 to 34 years) and 9 elderly (ages, 65 to 82 years) healthy volunteers. Ciprofloxacin decreased antipyrine oral clearance in young and elderly subjects (P less than 0.05), with the average decreases being similar in both groups (23.3% for the young subjects and 27.9% for the elderly subjects). Ciprofloxacin concentrations in serum were significantly higher (mean, 57%) in the elderly. The formation clearance of 4-hydroxyantipyrine and 3-hydroxymethylantipyrine was also significantly decreased in both groups of subjects; however, norantipyrine formation, accounting for 15 to 20% of antipyrine clearance, was reduced only in the elderly. These results suggest that elderly subjects are not more sensitive to the inhibitory effect of ciprofloxacin on antipyrine metabolism. However, careful clinical monitoring is necessary with all patients, irrespective of age, taking ciprofloxacin concomitantly with drugs primarily eliminated by the cytochrome P-450 system.

Adult↗
PubMed1991

Effect of age on lymphocyte beta 2-adrenergic responsiveness.

Beta-adrenergic receptor agonists and antagonists are among the most widely used classes of agents in the US today. Heterogeneity in pharmacologic response among humans exists. This article reviews the influence of age on lymphocyte beta 2-adrenergic receptor responses. Evidence obtained in humans indicates that beta-adrenergic receptor numbers on peripheral blood cells may differ, although the direction of the change is not consistent among laboratories. Drug-induced regulation of receptors either up or down appears to be similar among age groups. The affinity of beta-adrenoceptor binding sites for isoproterenol decreases with aging. Events distal to the receptor recognition site itself exhibit age-related differences, presumably due to a decrease in the coupling of beta-adrenoceptors to adenylate cyclase. Mechanisms of decreased catecholamine responsiveness during aging remain to be defined. The precise definition of these alterations may contribute useful insights into the changes that occur with aging in response to catecholamines, other hormones, and neurotransmitters.

Adult↗
PubMed1990

Asymmetrical pulmonary changes in premature infants with surgical closure of a persistent ductus arteriosus.

The chest radiographs of 57 premature infants admitted consecutively with hyaline membrane disease and receiving respirator therapy were reviewed, comparing right and left pulmonary abnormalities. Fifteen infants (Group I) did not develop a persistent ductus arteriosus (PDA). Forty-two infants developed a PDA, which was successfully treated with indomethacin in 17 infants (Group II), while in 25 infants (Group III) the ductus was closed surgically. Analysis of the three groups showed that infants who had undergone surgical closure of their PDA developed significantly more asymmetrical broncho-pulmonary damage. Statistically significant fewer radiological findings of broncho-pulmonary damage were found on the left side in comparison with the right side in the group treated surgically.

Bronchopulmonary Dysplasia↗
PubMed1989

Racial differences in drug response: isoproterenol effects on heart rate in healthy males.

It was the purpose of this study to investigate racial alterations in beta-adrenoceptor response. Two groups of healthy, male volunteers gave their consent. There were eight black Americans (mean age, 26.1 +/- 2.5 years) and eight white/Caucasian Americans (mean age 24.4 +/- 1.8 years). Each subject underwent an isoproterenol sensitivity test. There was a significant (P less than 0.05) decrease in the ratio of Emax to ED50 in the white group (25.3 +/- 6.4) compared with the black group (37.1 +/- 12.4). Over the dose range of 0.1 to 1.0 micrograms there was a significant increase in response at both the 0.25- and the 0.5-microgram dose (P less than 0.05), with the black American group appearing to respond with a greater rate of rise in heart rate following the initial doses.

Adult↗