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Biomedical subjects

D L Davis

Publications and source records attributed to D L Davis.

At least 235 records · Page 13Linked to original sources
PubMed1973

Influence of Temperature on Sterol Biosynthesis in Triticum aestivum.

Sitosterol, campesterol, stigmasterol, and cholesterol were isolated from green wheat (Triticium aestivum var. Monon) seedlings. Sitosterol was the predominant sterol extracted from the shoot, root, and crown tissue. Cholesterol accounted for less that 1% of sterol in shoot tissue with only trace amounts in the root. A temperature change from 10 to 1 C resulted in a general decrease in sitosterol, stigmasterol, and campesterol in the shoot tissue. The cholesterol level was not altered significantly by the temperature change. The sterols in the root responded in a manner very different from those in the shoots. With the reduction in temperature, sterols first decreased and then recovered over a period of 7 to 14 days to levels that were equal to or exceeded the original levels. From these experiments, it would appear that root tissue can acclimate to the lower temperatures and continue sterol synthesis at the normal rate. The level and response of sterols in the crown tissue were intermediate between the root and shoot tissue. At 10 C the crown response was similar to that of root tissue, whereas, at 1 C the response more closely resembled that of the shoot.

Journal Article↗
PubMed1972

Calcium as mediator of isoproterenol-induced myocardial necrosis.

Isoproterenol (ISO), a drug which causes an increased strength of myocardial contraction when administered to animals in mug/kg doses, causes myocardial necrosis when given mg/kg doses. Previous studies suggested that necrosis might be due to flooding of the heart muscle cells by calcium. To determine if this is true, and to distinguish between flooding due to release of Ca from sequestered intramyocardial compartments and increased influx from the blood, we have measured total myocardial calcium ([Ca](m)) after ISO administration. The concentration of myocardial calcium, measured by atomic absorption spectroscopy after dry ashing, increased within 10 minutes of the intraperitoneal injection of ISO in rats. After 10 minutes the [Ca](m) remained constant at its new level for at least 50 minutes if the dose of ISO was 10(2) mug/kg or less but continued to rise at a slower rate than noted during the first 10 minutes if the ISO dose was 10(3) mug/kg or more. As measured 1 hour after ISO administration, the increase in [Ca](m), was proportional to the dose, up to 10(2) mug/kg. At higher doses there was no further increase until the dose exceeded 2 x 10(3) mug ISO/kg. Since the amount of necrosis is proportional to dose from about 10(2) to 10(5) mug/kg, while the changes in [Ca](m) are not proportional to dose over this entire range, it is concluded that ISO-induced myocardial necrosis is not mediated exclusively by flooding of heart muscle with plasma-derived calcium, although this is undoubtedly an important factor. This conclusion was further supported by experiments showing that propranolol, at doses which completely suppressed the increase in [Ca](m) due to ISO, did not completely prevent necrosis.

Animals↗
PubMed1971

Changes in Sterol Composition during Greening of Etiolated Barley Shoots.

THE FOLLOWING STEROLS WERE IDENTIFIED IN BARLEY SHOOTS: stigmasterol, beta-sitosterol, campesterol, and cholesterol. The total sterol content of green and etiolated tissue was 2.84 and 3.20 milligrams per gram dry weight, respectively. The free sterols accounted for most of the difference in total sterol content. The sterol ester, sterol glycoside, and acylated sterol glycoside contents of green and etiolated barley shoots were essentially the same. Etiolated tissue had twice as much total beta-sitosterol as stigmasterol, while green tissue had equal amounts of these two sterols. The campesterol and cholesterol content was the same in green and etiolated tissue. This same sterol composition pattern held true for the free, glycosidic, and acylated glycosidic sterols; however, the sterol ester fraction had a completely different composition pattern. The esterified stigmasterol content was quite low in green and etiolated tissue, and campesterol was the second largest esterfied sterol component in etiolated tissue. Etiolated barley seedlings exposed to light had a shift in the ratio of free stigmasterol to beta-sitosterol in favor of stigmasterol; however, no correlation was observed between chlorophyll synthesis and shift in sterol composition.

Journal Article↗