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Biomedical subjects

J Stewart

Publications and source records attributed to J Stewart.

At least 505 records · Page 28Linked to original sources
PubMed1982

Diarrhoea in dairy calves reduced by feeding colostrum from cows vaccinated with rotavirus.

Forty-two dairy calves remained with their dams for two days after birth, and then were removed to a calf rearing shed. Calves were allocated to three groups for the next 14 days, and received twice daily either whole milk, whole milk with a 10 per cent supplement of pooled normal bovine colostrum or whole milk with 10 per cent supplement of colostrum from cows vaccinated with rotavirus. A natural outbreak of diarrhoea occurred, affecting 28 of the 42 calves. Feeding immune colostrum delayed the onset of diarrhoea, and reduced its incidence, duration and severity. Live weight gains were consequently improved. The group fed normal colostrum had diarrhoea intermediate in severity between that of control calves and those fed immune colostrum. The aetiology of the diarrhoea was complex, with calves excreting rotavirus, enteropathogenic Escherichia coli and cryptosporidia.

Animals↗
PubMed1982

Scintigraphic demonstration of ventriculo atrial conduction in the ventricular pacemaker syndrome.

A patient with the sick-sinus syndrome was evaluated because of symptomatic deterioration after insertion of a ventricular demand pacemaker. Clinical features of the ventricular pacemaker syndrome were recognized and confirmed by electrophysiological and hemodynamic studies. Phase analysis--a new technique for detecting patterns of cardiac emptying from gated cardiac blood-pool scintigrams--demonstrated a pattern consistent with 1:1 ventriculo-atrial conduction. Phase analysis of the gated cardiac blood-pool scintigram may be useful in the assessment of patients with ventricular demand pacemakers who complain of fatigue and effort intolerance.

Aged↗
PubMed1981

Temporal and environmental cues in conditioned hypothermia and hyperthermia associated with morphine.

The effectiveness of temporal and environmental cues in eliciting conditioned hypothermia and hyperthermia was studied in male Wistar rats using as an unconditioned stimulus an IP injection of 20 mg/kg of morphine sulfate. The relevance of temporal stimuli was minimized in Experiment 1 by administering morphine at irregular times on alternate days. For one group (Cond) morphine injections were preceded and followed by periods in distinctive environments. Group Pseudo animals, though exposed to the environments, received morphine on the intervening days in the home cage; group Saline received only saline. All animals receiving morphine showed a non-specific hypothermia when not under the direct influence of morphine. A "conditioned hyperthermia" was evident in group Cond animals in the distinctive environments. In Experiment 2, in which animals remained in their home cages at all times, the relevance of temporal cues was emphasized by administering morphine at exactly 24 h intervals. These animals became hypothermic only around the time of the expected injection. Animals in another group that received morphine at irregular times showed the non-specific hypothermia seen previously. There was no evidence for a conditioned hyperthermia in this second experiment.

Animals↗
PubMed1981

Reinstatement of cocaine-reinforced responding in the rat.

Non-contingent "priming" drug injections and conditioned stimuli associated with drug injections led to reinstatement of responding after a period of extinction. Rats implanted with intravenous catheters were trained to self-administer cocaine 1 mg/kg/injection), and then given daily test sessions consisting of a period of self-administration followed by extinction conditions. Test drug injections or conditioned stimuli were presented during extinction and the latency to the first response and the total number of responses following the treatment were measured. Cocaine injections of 0.5, 1.0, and 2.0 mg/kg restored responding during extinction, regardless of the duration of the extinction period (between 10 min and 180 min) since drug self-administration. Amphetamine, apomorphine, and morphine but not ethanol, heroin, or methohexital reinstated previously cocaine-reinforced responding. Amphetamine, cocaine, and morphine did not increase responding in animals trained to bar press only for food reinforcement, suggesting that the reinstatement effect is specific to drug-reinforced responses. The statement effect is specific to drug-reinforced responses. The final experiment showed that a tone that had been paired with drug infusions acquired a statistically significant tendency to facilitate responding when tested during extinction but this effect disappeared after the first test presentation of the tone.

Animals↗
PubMed1981

Conditioned temperature effects using amphetamine as the unconditioned stimulus.

Three groups of male Wistar rats received daily IP injections of either 1, 2 or 5 mg/kg amphetamine at 11:15 h; a fourth group received saline injections throughout. Rectal temperature was measured in the home cage, in a pre-injection environment in which animals were placed for a period of time before the daily injection, and in an injection environment in which animals remained following the injection. Conditioned hyperthermia, a response that mimicked the unconditioned effect of amphetamine, was elicited by cues of the injection environment both during conditioning and after the drug-free period. During conditioning, hypothermia occurred at 10:30 h regardless of where the animals were, but could not be elicited at other times of day. The results with amphetamine parallel those found previously with morphine (Eikelboom and Stewart 1979, 1981).

Amphetamine↗
PubMed1981

An inverse correlation between serum levels of desmethylimipramine and melatonin-like immunoreactivity in DMI-responsive depressives.

The relationship between plasma levels of the tricyclic antidepressant desmethylimipramine (DMI) and plasma levels of melatonin-like immunoreactivity was studied in 32 endogenously depressed patients. An inverse correlation between plasma levels of DMI and plasma levels of melatonin-like immunoreactivity was found in the group of clinical responders to the chronic administration of the drug. The nonresponders had higher levels of melatonin-like immunoreactivity at comparable levels of DMI. This finding is consistent with the hypothesis that chronic high plasma levels of DMI may down-regulate the beta-adrenergic receptors in man. However, some other homeostatic mechanisms may be involved in the clinical response.

Adolescent↗
PubMed1981

Monoamine oxidase inhibitors in bipolar endogenous depressives.

Clinical lore suggests that monoamine oxidase inhibitors (MAOIs) are not effective in endogenous depression. A review of previous placebo-controlled trials of MAOI in patients with endogenous depression neither refutes nor confirms their utility in this patient group. We present patients in the depressive phase of bipolar illness refractory to treatment with tricyclics who have responded to MAOI. These open trials require confirmation in controlled studies. Bipolar illness may be a heterogeneous disorder. Presence or absence of X-linkage, low platelet MAO, or response to MAOI may indicate different forms of the disorder.

Bipolar Disorder↗