Effects of acute ischemia in the dog on myocardial blood flow, beta receptors, and adenylate cyclase activity with and without chronic beta blockade

Article Abstract:

Acute ischemia (decreased blood flow and consequent decreased oxygen supply) was produced in the hearts of dogs by placing a suture around the principle artery of the left heart chamber. Following this procedure the authors examined the animals hearts and compared the damaged and undamaged areas for Beta-Adrenergic receptors. (sites on the surface of certain cells which are able to be stimulated by nerves and by increasing the strength of the hearts pumping there by increasing the heart beat, thus increasing the demand for oxygen.) The authors failed to detect any changes in receptors when comparing damaged and undamaged areas of the heart. They followed chronic treatment with a certain type of drug known as beta adrenergic blocking agents (work to decrease blood pressure, decrease rate of strength of the heart's beat and decrease the oxygen demand of the heart and as a result increase tolerance to exercise). The authors conclude that chronic use of beta-adrenergic blocking agents may have beneficial effects during prolonged periods of ischemia of the heart.

Physiological aspects, Laboratory animals, Dogs, Ischemia, Adrenergic beta blockers, Adrenergic beta-antagonists, Dogs as laboratory animals

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A lethal variant of osteogenesis imperfecta has a single base mutation that substitutes cysteine for glycine 904 of the alpha 1(I) chain of type I procollagen. The asymptomatic mother has an unidentified mutation producing an overmodified and unstable type I procollagen

Article Abstract:

In a particular individual who inherited a lethal form of osteogenesis imperfecta, a disease of connective tissue,a unique abnormality was identified in the ability of the patients fibroblasts (cells of connective tissue which produce fibrous elements such as collagen) to produce a building block (procollagen) for collagen, a connective tissue protein. The defective procollagen which has a molecular abnormality, was found to be sensitive to heat. The results suggest that a spontaneous mutation led to the production of a lethal form of this disease and that the trait cannot be inherited.

Abnormalities, Osteogenesis imperfecta, Genetic aspects, Collagen, Collagen diseases

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