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Biomedical subjects

R M Stewart

Publications and source records attributed to R M Stewart.

At least 91 records · Page 5Linked to original sources
PubMed1980

Carbohydrate metabolism in phenylketonuria.

Carbohydrate metabolism was studied in 6 adult patients with phenylketonuria both on a low phenylalanine and an unrestricted institutional diet. Tolerance tests included PO glucose, PO phenylalanine, and combined glucose phenylalanine loading. Glucose, insulin, pyruvate, lactate, and phenylalanine were sampled at 0, 1/2, 1, 2, 3, and 4 hr. Fasting glucose levels were normal as were mean glucose values after challenge. Basal insulin secretion, as well as insulin response, to glucose challenge and to combined phenylalanine and glucose loading appeared normal. Insulin response to phenylalanine alone, however, was lower than expected in the phenylketonuria patients. Both off and on low phenylalanine diet, blood pyruvate and lactate were also normal. Thus, our data from blood did not show evidence of the abnormalities in glucose and pyruvate metabolism which have been proposed to occur in phenylketonuric patients but did not suggest that the potency of phenylalanine as an insulin secretagogue is diminished by chronic hyperphenylalaninemia.

Blood Glucose↗
PubMed1980

Unruptured cerebral aneurysms presenting as recurrent transient neurologic deficits.

Recurrent transient neurologic deficits were evaluated clinically in four patients. In three patients, the symptoms included recurrent transient homonymous hemianopia, episodic weakness and numbness of the left arm and leg, and recurrent sudden loss of speech and of strength in the right arm. In these three patients, the episodes were first thought to be transient ischemic attacks (TIAs). A fourth patient had repeated confusional spells, in which a recurrent musical theme excluded other thoughts. This was associated with dizziness and difficulty in naming. A partial complex seizure was thought responsible. In each of the cases the symptoms lasted less than 30 minutes and were not associated with loss of consciousness, headache, or stiff neck. Electroencephalogram (EEG), brain scan, lumbar puncture, and computed tomography (CT) scan were normal. In all patients, cerebral arteriography unexpectedly revealed an unruptured cerebral aneurysm. The locations of the aneurysms were appropriate to the symptoms, which remitted in the three patients treated surgically for the aneurysm. Although the pathophysiology is uncertain, an ischemic process may be implicated.

Adult↗
PubMed1979

Thrombocytosis, circulating platelet aggregates, and neurological dysfunction.

In 12 patients whose neurological dysfunction was associated with thrombocytosis or evidence of abnormal platelet activation, or both, correction of the platelet disorder corresponded with reversal of the neurological symptoms. This suggests that platelet abnormalities may, in certain cases, produce several syndromes of neurological dysfunction, presumably as a result of obstruction of the cerebral microcirculation.

Adolescent↗
PubMed1979

Distal airway responses to changes in oxygen and carbon dioxide tensions.

The reactivity of subpleural strips of lung parenchyma reflects primarily the tone of the smooth muscle in the peripheral airways. Lung strips taken from ten dogs relaxed when the oxygen level in the gas bubbling through the bath was reduced from 95% to 18%. Subsequent hypocapnia (carbon dioxide reduced from 5% to 0%) induced contraction of all strips. These changes were reversed when the oxygen or carbon dioxide tensions were restored to control levels. Addition of either indomethacin or meclofenamate, two chemically dissimilar inhibitors of prostaglandin synthetase, reduced the resting tone in each of six strips and prevented the hyperoxic constriction which was observed in paired, control strips (oxygen increased from 18% to 95%). Blockers of histamine and catecholamines had no effect. The reactivity of the distal airways to changes in gas tension provides a mechanism by which ventilation and perfusion can be matched. The action of indomethacin and meclofenamate indicates that a prostaglandin-like substance may be involved in the maintenance of distal airway tone and in the constriction produced by hyperoxia. The addition of prostaglandin F2 alpha or E1, after meclofenamate, in a further nine pairs of strips did not restore the hyperoxic constriction. This suggests that prostaglandins may mediate, rather than merely facilitate, the response.

Animals↗
PubMed1979

Withdrawal of chronic chlorpromazine medication: an experimental analysis.

Approximately 50% of all institutionalized, mentally retarded adults receive psychotropic medication to control inappropriate behavior. In this study, behaviors exhibited by five retarded adults were formally observed while they were on and off medication. Each subject had been receiving chlorpromazine for six or more years prior to the start of the study. The drug was withdrawn and readministered using a double-blind B-A-B (drug placebo-drug) design. Effects were highly individualized. Some desirable behavior emerged when chlorpromazine was discontinued.

Adult↗
PubMed1978

Inhibition of 5,7-dihydroxytryptamine-induced supersensitivity to 5-hydroxytryptophan in mice by treatment with cycloheximide.

Intracisternal injection of 5,7-dihydroxytryptamine (5,7-DHT) following treatment with desmethylimipramine induced development of behavioral supersensitivity to the intraperitoneally administered serotonin precursor 5-hydroxytryptophan (5-HTP) in the mouse. This behavioral syndrome, characterized by tremor and muscle twitches (myoclonus), showed a clear dose-response relationship with 5,7-DHT as well as with 5-HTP. Mice lesioned with a low dose of 5,7-DHT (20 micrograms) or a placebo were treated repeatedly with a protein synthesis inhibitor, sycloheximide (45 mg/kg, s.c., every 12 h for up to 10 days). This treatment resulted in a reversible decrease of cerebral protein synthesis varying between 70 and 20% with time between treatments. The myoclonic response to 5-HTP in animals pretreated with 5,7-DHT and by cycloheximide showed a decrease in intensity within 24 h when evaluated quantitatively by an electronic activity monitor, the results of which were confirmed by direct observation. Cycloheximide also exerted a similar, though smaller, effect following full development of sensitivity to 5-HTP over 10 days. These effects may de mediated by inhibition of rapidly turning over serotonin receptor proteins, although their interpretation is somewhat obscured by possible toxic effects of cycloheximide.

5,7-Dihydroxytryptamine↗
PubMed1978

Percutaneous liver biopsy and chronic liver disease in haemophiliacs.

Systematic screening of forty-seven haemophiliacs in Sheffield revealed abnormal liver-function tests in thirty-six (77%), with a tendency for these abnormalities to persist. To assess the importance of these abnormalities, percutaneous liver biopsy was carried out on eight symptom-free patients under factor-VIII cover. A wide spectrum of chronic liver disease was demonstrated, including chronic aggressive hepatitis and cirrhosis. The liver pathology bore no relation to clinical history or to biochemical findings. Hepatitis-B-virus markers were common, but evidence suggests that this is not the only factor contributing to the development of liver disease. The high incidence of chronic liver disease seems to be a recent development and is probably related to factor-concentrate replacement therapy.

Adult↗
PubMed1978

Ventral porencephaly: a cerebral defect associated with multiple congenital anomalies.

An infant with multiple congenital anomalies was found at autopsy to have a porencencephalic defect on the ventral surface of the left frontal lobe. The intracranial defect was seen in association with an anomalous configuration of the circle of Willis. The zone of tissue destruction corresponded to the vascular territory of the anterior choroidal and lenticulo-striate branches of the proximal middle cerebral arteries, which were absent on the left. The developmental anomaly of the circle of Willis may have predisposed to tissue destruction by compromising cerebral perfusion at midgestation, a stage of rapid brain growth.

Abnormalities, Multiple↗
PubMed1978

Effects of diet and behavior therapy on social and motor behavior of retarded phenylketonuric adults: an experimental analysis.

The effects of a low phenylalanine diet on six retarded phenylketonuric adults were assessed. An ABA individual-subject design was used in experiment I to assess the effects of a low phenylalanine diet on social and motor behavior. Following a baseline during which the subjects ingested a normal phenylalanine diet (phase A), a low phenylalanine diet (phase B) was administered in a double blind fashion. Finally, the baseline condition (phase A) was reinstated (normal diet). The low phenylalanine diet resulted in few significant behavioral changes for those subjects with which proper methodologic controls were employed. However, for two of six subjects motor behavior, including stereotypy and tremor, seem to have ameliorated. In experiment II, applied behavior analysis techniques, including differential reinforcement of other behavior and time out, were combined to radically reduce the frequency of stereotypy and self-abuse exhibited by one of the six subjects of experiment I.

Adult↗