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Biomedical subjects

P Hicks

Publications and source records attributed to P Hicks.

27 records · Page 2Linked to original sources

Regional uptake of [35S]-cysteine in rat brain after arterial injection.

The brain uptake index of [35S]-cysteine in ten rat brain regions and in the eye was determined by measuring [35S]-cysteine remaining in the brain regions and in the eye, five seconds after carotid injection, relative to a simultaneously injected diffusible internal standard, 3H2O and a non-diffusible internal standard Tc99m-Sn-DTPA. A statistical comparison for the regions that receive their blood supply from the internal carotid artery was done. Only the diencephalon and the septum-nucleus accumbens were found significantly higher than cortex.

Animals↗

Myoclonus in Down's syndrome. Association with alzheimer's disease.

Myoclonus and progressive intellectual deterioration developed in a 46-year-old woman with trisomy 21 (Down's syndrome) during the final stages of her illness. Her condition was clinically diagnosed as Creutzfeldt-Jakob disease, but necropsy demonstrated the changes characteristic of Alzheimer's disease and cerebrovascular amyloidosis.

Alzheimer Disease↗

Age-related alterations in the rodent brain cholinergic system and behavior.

Pre- and postsynaptic cholinergic markers were studied in various brain regions of mice and rats aged 6 to 30 months in an attempt to determine whether alterations in this transmitter system occur during the normal aging process. Reliable decreases in cholinergic receptor binding and choline acetyltransferase (CAT) activity were found in the cerebral cortex and corpus striatum. These alterations in the cholinergic system were typically more consistent and robust than changes involving glutamic acid decarboxylase, and enzyme marker for GABA neurons. No statistically significant changes in any markers were found in the hippocampus of either species. Significant age-related changes in retention of passive avoidance learning and locomotor activity were also observed in these same animals. These findings demonstrate that changes in the cholinergic system occur naturally in aged mice and rats and that both the loss of cholinergic receptors and decrease in cat activity may contribute to the motor and mental impairments that often accompany old age.

Aging↗

Studies on the hypotensive action of alpha-methyldopamine.

1. Intraventricular alpha-methyldopamine (50-200 mug) produced a dose-related fall in blood pressure in conscious spontaneously hypertensive rats. Pretreatment with intraventricular 6-hydroxydopamine prevented this hypotensive effect of alpha-methyldopamine. 2. The hypotensive effect of alpha-methyldopamine was prevented by intraventricular injection of phentolamine or desmethylimipramine, but not by intraperitoneal injection of haloperidol. 3. Pretreatment with U-14,624, a selective central dopamine-beta-hydroxylase inhibitor, prevented the hypotensive effect of alpha-methyldopamine. 4. Alpha-methyldopamine was considerably less potent than noradrenaline as a pressor agent in the pithed rat, but noradrenaline and alpha-methylnoradrenaline were found to be equipotent. 5. Alpha-methyldopamine (1-5 mg i.c.v.) reduced pressor responses elicited by electrical stimulation of the midbrain reticular formation in cats anaesthetized with chloralose. 6. It is concluded that the hypotensive action of alpha-methyldopamine in conscious animals involves intact central alpha-adrenergic neurones and a central adrenergic uptake mechanism for the formation of alpha-methylnoradrenaline.

Animals↗

Verapamil preceded by calcium in supraventricular tachycardia.

Verapamil has been shown to be effective in the management of supraventricular tachycardia (SVT). However, the utility of verapamil may be limited because of adverse effects, specifically hypotension. Several clinical observations have shown that the intravenous administration of calcium is effective in reversing the myocardial depressant effects of verapamil. We report the case of a patient with SVT and a systolic blood pressure of 80 mm Hg in which the administration of calcium chloride prior to that of verapamil may have negated verapamil-induced hypotension.

Calcium↗