Modification of the valve of the French pressure cell.
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Cell-Free System↗
Biomedical subjects
J R Walters
Publications and source records attributed to J R Walters.
Tricyclic antidepressants: effects on the firing rate of brain noradrenergic neurons.
The spontaneous activity of the norepinephrine-containing cells of the locus coeruleus was recorded in chloral hydrate-anesthetized rats. The effect of seven tricyclic antidepressants on the firing rate of single cells in the locus coeruleus was studied. All the drugs tested, except iprindole markedly decreased the rate of firing of the noradrenergic cells. Antidepressants having a secondary amine in the side chain, desipramine, nortriptyline and chlordesipramine, were more potent than their respective tertiary amine analogues, imipramine, amitriptyline and chlorimipramine. Alteration of the rate of drug metabolism by pretreatment with SKF-525A or phenobarbital did not change the doses of tertiary antidepressnats required to decrease norepinephrine cell firing. Depletion of the norepinephrine stores by pretreatment with alpha-methyl-p-tyrosine and reserpine markedly increased the dose of desipramine required to depress the norepinephrine cells. The results are in good agreement with previous studies showing that secondary amine antidepressants are more potent than their tertiary amine homologues in blocking the uptake of norepinephrine into brain and peripheral tissues. Despite their lower potency it is concluded that tertiary antidepressants act on noradrenergic neurons in their unchanged form and not via secondary amine metabolites formed during the recording experiments since alterations in liver metabolism did not influence the response. The findings are consistent with the suggestion made from studies on transmitter turnover that antidepressants by inhibiting reuptake of norepinephrine cause a stimulation of postsynaptic receptors which decreases the activity of the presynaptic neurons by a feed-back mechanism. This view is further supported by the finding of an inverse relation between the norepinephrine content of the brain and the dose of desipramine required to decrease the firing rate of the noradrenergic neurons.
Animals↗
The investigation of iron deficiency anemia--a hospital based audit.
BACKGROUND/AIMS: Iron deficiency anemia (IDA) is associated with an increased incidence of malignancy. Our aim was to audit the management of patients with IDA seen in a teaching hospital gastroenterology unit, and to assess the role of upper and lower gastrointestinal endoscopy as well as mesenteric angiography in improving the diagnostic yield. METHODOLOGY: A retrospective review of all outpatient letters and in-patient discharge summaries in an 11 month period in 1996 was used to identify anemic patients. All endoscopic and radiological procedures were documented on these patients. RESULTS: 98 cases (46 male) of IDA were identified. Of these, 94% had upper GI endoscopy with a yield for potential bleeding sources of 54% (including 4 malignancies) and 84% had lower GI investigation by colonoscopy or barium enema with a diagnostic yield of 37% (including 3 malignancies and 10 adenomatous polyps). Combined endoscopic and barium examinations provided a positive diagnosis in 69%, and 12.2% had significant co-existent upper and lower GI pathology. Thirty-three patients underwent visceral angiography (27 of who had no positive endoscopic diagnosis). Twenty-seven studies revealed a bleeding source (yield 82%). Overall an underlying diagnosis was made in 92% of patients. CONCLUSIONS: The incidence of significant dual pathology in patients with IDA was high. Investigation of the lower GI tract should be performed in all patients unless a malignancy is found on upper GI endoscopy. Mesenteric angiography has a high diagnostic yield, and is a useful investigation in patients with resistant or transfusion dependent anemia in whom endoscopic or barium studies are normal.
Adult↗