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Biomedical subjects

T Nikkari

Publications and source records attributed to T Nikkari.

At least 127 records · Page 7Linked to original sources
PubMed1976

Increased cholesterol content and esterification in rabbit aortic medial cells cultured in hyperlipidemic serum.

Cells of early atherosclerotic lesions have an increased content of cholesteryl esters and enhanced rate of cholesterol esterification. The present study was carried out to elucidate whether these changes could be reproduced in a purely in vitro system. Cultures of rabbit aortic medial cells were incubated in a medium containing 10% of either normal rabbit serum (control cells) or serum from rabbits with cholesterol-induced hyperlipidemia (hyperlipidemic cells). The incorporation rate of [1-14C]oleate into cellular cholesteryl esters increased two- to threefold after four hours' incubation with hyperlipidemic serum and remained elevated during the rest of the eight days' study. After seven days' incubation the hyperlipidemic cells incorporated significantly more (+13%) oleate into triglycerides and significantly less (-15%) oleate into phospholipids than did the control cells. Cholesteryl ester content of the hyperlipidemic cells rose steeply for about two days, with a slower rise thereafter. In hyperlipidemic cells the esterified cholesterol content was significantly higher (315 ng/mug DNA) than in the control cells (79 ng/mug DNA). Hyperlipidemic cells showed a slow but significant rise of free cholesterol as well (from 1.15 mug/mug DNA in control to 1.50 mug/mug DNA). The results indicate that lipid changes resembling those in early atherosclerotic lesions can be brought about in vitro 0y treatment of aortic cells with hyperlipidemic serum.

Animals↗
PubMed1975

Isotope kinetics of human skin cholesterol secretion.

Specific radioactivity (SA) time curves of plasma and skin surface cholesterol collected at several skin areas were recorded in 10 patients on formula diets after single intravenous injections of radioactive cholesterol. Earliest detectable radioactivity on skin surface was found in 4-6 days; depending on the skin site, SA's peaked in 13-75 days. SA's of free cholesterol were almost always higher than those of esterified cholesterol. The general forms of the SA time curves were in keeping with the idea that plasma cholesterol is carried to the skin surface in association with the epidermal and sebaceous cells, whereby (a) cholesterol synthesized de novo is mixed with derived from plasma and (b) appearances of plasma cholesterol on the skin surface is delayed by a time factor that corresponds to the movement of epidermal and sebaceous cells from the basal layer to the skin surface. The shorter mean transit times of plasma cholesterol on skin areas rich in sebaceous glands (22-24 days on the head) than on those poor in these glands (38 days on forearms and 72 days on feet) suggest that cholesterol passes faster through the sebaceous glands than through the epidermis, and faster through thin than thick epidermis. The fraction of skin surface cholesterol (f) that is derived from plasma cholesterol was estimated by three independent methods, and comparable results were obtained. Values of f were lower on skin areas rich in sebaceous glands (0.29-0.46 on forehead) than on areas poor in these glands (0.41-0.70 for forearms; 0.60 on feet) and lower for esterified (0.27-0.33) than for free (0.39-0.48) cholesterol. These data suggest that higher proportions of sebaceous gland and of esterified cholesterol, respectively, are synthesized de novo than epidermal and of free cholesterol. In two patients it was possible to calculate that f of total skin surface cholesterol was 0.49 and 0.37, respectively, and that the maximum amount of plasma cholesterol lost through the skin was 29 and 22 mg/day, respectively. Knowing the total daily excretion of total neutral and acidic steroids in feces in these patients, and assuming a total daily urinary steroid excretion 50 mg, we estimated that no more than 3.2% of total steroid excretion occurred via the skin.

Adult↗
PubMed1974

In vivo studies of sterol and squalene secretion by human skin.

This work was aimed at studying the quantity and composition of sterols and squalene secreted by the human skin. Lipids secreted by the entire skin were recovered by Soxhlet extraction of the clothing worn by a patient for 24 hr with a chloroform-methanol azeotrope and by extracting the water of a shower taken by the patient at the end of the 24-hr period. Squalene and sterols were quantified by gas-liquid chromatography. Plant sterols were separated from total sterols by thin-layer chromatography. Free and esterified cholesterol were separated by digitonin precipitation. In eight adults, seven of them with hyperlipoproteinemia, the total skin secretion of cholesterol ranged from 59 to 108 mg/day, with a mean of 88 +/- 17 (SD) mg/day. There was no difference in cholesterol secretion between the normocholesterolemic individual and the hypercholesterolemic ones, nor were there any differences according to type of hyperlipoproteinemia. Free cholesterol amounted to 54 +/- 5% of the total cholesterol. The secretion of squalene ranged from 125 to 475 mg/day in five patients. The secretion of both squalene and cholesterol was quite constant for any individual on a given diet. Cholesterol constituted 95.6 +/- 0.5% of the digitonin-precipitable total body surface sterols of eight patients, and lathosterol, the next largest fraction, 3.4 +/- 0.4%. Total plant sterols formed only 0.65 +/- 0.38% and beta-sitosterol 0.35 +/- 0.23% of the skin surface sterols in six patients whose dietary beta-sitosterol intake ranged from 230 to 3400 mg/day.

Adult↗