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Biomedical subjects

D A Cook

Publications and source records attributed to D A Cook.

At least 109 records · Page 6Linked to original sources
PubMed1984

The pharmacology of cerebral vasospasm.

About 3 days after subarachnoid hemorrhage the cerebral blood vessels often undergo a sustained constriction (cerebral vasospasm) which is associated with increased morbidity and mortality. Examination of the literature suggests that interactions of hemoglobin, various prostaglandins, and perhaps some other agents are responsible for this condition, which is apparently associated with endothelial damage or other structural changes. The most promising therapy involves treatment with calcium antagonists.

Calcium Channel Blockers↗
PubMed1984

Evidence for an indirect component of the action of histamine on canine portal vein.

Histamine caused contraction of spiral strips of the canine portal vein. This is an H1 response and no evidence of any H2 receptor activity was observed. The response to histamine was blocked by the alpha-adrenoceptor antagonists phentolamine and prazosin, but not by the alpha 2-receptor blocker yohimbine. Pretreatment of the tissue with 6-hydroxydopamine significantly reduced the response to histamine and tyramine while the response to noradrenaline was unchanged. A marked tachyphylaxis developed to tyramine and histamine, but not to noradrenaline. We conclude that a component of the contractile activity of histamine on the canine portal vein involves release of endogenous catecholamines and that this response is mediated by H1 receptors.

Animals↗
PubMed1984

Tympanometric changes following nasal antigen challenge in children with allergic rhinitis.

Intranasal antigen provocation was used to study the relationship between allergic rhinitis and changes in middle ear pressure. Middle ear pressure was measured by tympanometry and nasal airway resistance by anterior rhinomanometry. Middle ear pressure became significantly more negative following antigen challenge as compared with control challenge. A subgroup of patients showed middle ear pressure changes of more than minus 50 mm water. This pressure change was rapid and was associated with increased nasal symptoms. These results indicate a role for allergy in the development of negative middle ear pressure, a key finding in otitis media with effusion.

Acoustic Impedance Tests↗
PubMed1983

Accidental inhalation of mercury vapour: respiratory and toxicologic consequences.

Four adults, including a pregnant woman, and three children were admitted to hospital following accidental exposure to mercury vapour produced by heating mercury-gold amalgam. Initial symptoms and signs included a paroxysmal cough, dyspnea, chest pain, tachypnea, nausea, vomiting, fever and leukocytosis. Pulmonary function testing performed on the second day after exposure revealed air-flow obstruction and minor restrictive defects in three patients. The diffusing capacity of the lung for carbon monoxide was reduced in two of these patients. The mean initial blood mercury level (+/- one standard deviation) for the seven patients was 30.8 +/- 1.5 micrograms/dl. A computer analysis showed mercury to behave as a two-compartment system, the compartments having half-lives of 2 and 8 days. The four adults received chelation therapy with D-penicillamine, which did not affect the urinary excretion of mercury. The pregnant woman's infant, born 26 days after exposure, had no detectable clinical abnormalities. The levels of mercury in the blood of the mother and infant at birth and 6 days later were comparable, indicating free transfer of the metal across the placenta.

Accidents↗
PubMed1981

Fecal characteristics in healthy young adults consuming defined liquid diets or a free-choice diet.

Fat and nitrogen absorption and fecal characteristics were studied in 10 healthy, young adults who ingested a free-choice diet for 12 days and then isocaloric amounts of one of two nutritionally complete liquid defined formula diets during a succeeding 12-day period. Apparent fat absorption was 98 to 99% of intake with both defined formula diets and 95% of intake on the free-choice diet. Nitrogen digestibility was determined during the liquid diet period, and averaged 95 to 98% of intake. There were no statistically significant differences between the liquid diets and the free-choice diets with respect to fecal wet or dry weight, transit time, or stool frequency. Individual stool weights averaged 83 to 96 g on the free-choice or liquid formula diets and were comparable to other values reported in the literature. These results support the theory that a critical volume of feces must accumulate in the colon before defecation occurs, regardless of diet composition.

Absorption↗
PubMed1981

Effects of various intracranial fluids on smooth muscle.

Samples of cerebrospinal fluid (CSF) drawn from patients with subarachnoid hemorrhage, subdural hemorrhage, or brain tumor, as well as control samples from patients without a known cerebral pathological condition, were tested for their ability to contract smooth muscle. Canine middle cerebral artery, canine basilar artery, and rat stomach fundus were used, and contractions were expressed as the percentage of the contraction elicited by a standard dose of 5-hydroxytryptamine. All samples that contained blood produced contractions of the smooth muscle preparations, and despite a large sample no significant differences were observed in the magnitude of the contractions either between preparations or between samples from different groups of patients. Control samples were generally without significant effect. Neither methysergide, a 5-hydroxytryptamine antagonist, nor indomethacin, an inhibitor of prostaglandin synthesis, significantly diminished the contractions induced by bloody CSF, although the calcium antagonist D600 successfully antagonized the response in all groups. D600 was a better antagonist of the action of blood-containing CSF on cerebral artery than on stomach fundus. Samples obtained from patients with angiographic evidence of vasospasm were significantly more active than those obtained from patients without vasospasm, but the latter retained considerable activity.

Animals↗
PubMed1980

Responses of rabbit renal artery to histamine: receptor type and temperature dependence.

The effects of histamine on spiral strips of rabbit renal artery have been recorded. Histamine causes dose-dependent contractions of this preparation which are not antagonized by the H2 receptor blocking agent metiamide, but which are blocked by the H1 antagonist diphenhydramine. The pA(2) for the latter agent is similar to that observed at 37 degrees C in intestinal smooth muscle. No evidence of a relaxant population of H2 receptors was encountered. Unlike that of intestinal smooth muscle, the response of strips of renal artery becomes progressively diminished at temperatures below about 20 degrees C, and the effect of reduced temperature on receptor subtype is thus more difficult to assess. It appears, however, that there is no change in type from the H1 receptor observed at 37 degrees C and thus the temperature-dependent transformation which has been reported previously does not occur in all H1 systems.

Animals↗