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Biomedical subjects

A J Riddell

Publications and source records attributed to A J Riddell.

7 recordsLinked to original sources
PubMed1990

Effect of calcitonin-gene-related peptide on postoperative neurological deficits after subarachnoid haemorrhage.

An infusion of calcitonin-gene-related peptide (CGRP) at progressively increased concentrations was given to 15 patients with neurological deficits after intracranial aneurysm surgery for subarachnoid haemorrhage. In 9 of the patients the deficits, quantified by a modified Glasgow coma scale, improved with no adverse effects; after a placebo infusion only 2 of the 15 patients showed improvement. If CGRP can reverse cerebral ischaemia after early intracranial aneurysm surgery, its use may improve the safety of such early surgery, remove the need for late surgery with its increased risk of death from rebleeding, and reduce overall morbidity and mortality of aneurysmal subarachnoid haemorrhage.

Adult↗
PubMed1989

A comparison of the effects of human alpha calcitonin gene-related peptide and glyceryl trinitrate on regional blood velocity in man.

1. Human alpha calcitonin gene-related peptide (h alpha CGRP) is a potent vasodilator which in doses up to 1.5 micrograms min-1 i.v. produces little or no fall in blood pressure in normal volunteers, but does cause a substantial tachycardia. 2. We have explored the underlying mechanism of this effect by comparing h alpha CGRP infused so as to maintain heart rate 25-30% above baseline with glyceryl trinitrate (GTN) in a dose sufficient to maintain a throbbing headache. 3. Ten normal volunteers were studied. In addition to blood pressure and heart rate, blood velocity and pulsatility index (PI) were determined from Doppler signals recorded from the internal and external carotid, renal and femoral arteries. 4. Following h alpha CGRP blood pressure (mean +/- s.d., mm Hg) did not significantly change: 120 +/- 10/70 +/- 7 before compared with 121 +/- 12/67 +/- 7 during h alpha CGRP infusion. Heart rate (mean +/- s.d., beats min-1) increased from 62 +/- 8 to 86 +/- 10 (P less than 0.0001). In contrast the blood pressure fell following GTN: 124 +/- 12/74 +/- 8 before compared with 111 +/- 13/62 +/- 6 following treatment (P less than 0.02). Heart rate did not change following GTN: 64 +/- 9 compared with 69 +/- 10. 5. GTN significantly increased PI (mean +/- s.d.) in the common carotid artery from 2.8 +/- 0.5 to 3.4 +/- 0.5 (P less than 0.003) while h alpha CGRP increased PI in the internal carotid from 1.3 +/- 0.2 to 2.1 +/- 0.4 (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1975

Inhibitory action of oestrogen on calcium-induced mitosis in rat bone marrow and thymus.

In the male rat injections of CaCl-2 and MgCl-2 stimulated mitosis in bone marrow and thymus tissue. The magnesium salt was also mitogenic in the normal female, but calcium only exerted its mitogenic effect after ovariectomy. Oestradiol, but not progesterone replacement therpy abolished calcium-induced mitosis in the ovariectomized rat. The inability of calcium to stimulate cell division was also apparent in the thyroparathyroidectomized female rat, suggesting the oestradiol blockage did not operate via some indirect action on the calcium homeostatic hormones calcitonin or parathyroid hormone. When thymic lymphocytes derived from male or female rats were isolated and maintained in suspension, increased calcium or magnesium concentrations in the culture medium stimulated the entry of cells into mitosis. Addition of oestradiol to the culture medium abolished the mitogenic effect of increased calcium levels, but had no effect on magnesium-induced proliferation. These experiments suggested that oestradiol might act at the cell surface to prevent the influx of calcium but not magnesium ions into the interior of the cell and thus to block the sequence of biochemical events which led to the initiation of DNA synthesis and culminate in mitosis.

Animals↗