Ergosterol distribution

Plasma levels of 3—5 p.g/mL are obtained two hours after adraiinistration of 200 mg ketoconazole. No accumulation in the bloodstream was noted after a 30-wk treatment with this dose. The half-life is approximately eight hours. When ketoconazole is taken with meals, higher plasma levels are obtained. Distribution studies using radioactive ketoconazole in rats show radioactivity mainly in the Hver and the connective tissue. Radioactivity is also present in the subcutaneous tissue and the sebaceous glands. After one dose of 200 mg in humans, ketoconazole is found in urine, saUva, sebum, and cenimen. Like miconazole, the mode of action is based on inhibition of the cytochrome P-450 dependent biosynthesis of ergosterol. This results in disturbed membrane permeabiUty and membrane-bound enzymes (8,10,23,25). 

Mechanism of Action An antifungal agent that inhibits ergosterol synthesis. Therapeutic Effect Destroys cytoplasmic membrane integrity of fungi. Fungicidal. Pharmacokinetics Low systemic absorption. Absorbed and distributed in each layer... 

Selective reduction of ergosterol and its derivatives has been carried out using electron transfer reduction. Product distribution depends on the hydroxy substituent as well as on the solvent and the metal used (Scheme 86). ... 

In yeast, however, the 7a-hydrogen is lost in the A A step. This reaction is inhibited in bramble tissue cultures by the fungicide AY9944. The wide distribution in fungi of considerable amounts of A - -sterols such as ergosterol (12-H) may be due to the absence or low activity of the A reductase in these organisms. The existence of lichesterol (II), a A -sterol has not yet been rationalized biosynthetically. 

Carbon—carbon double bonds which are conjugated to other multiple bonds can also be reduced selectively by dissolving metals. For example, in the selective reduction of ergosterol (7) the distribution of the regioisomers depends on the hydroxy substituent, as well as on the solvent and the metal employed 1 °. Excellent yields of the (ran. -fused product 8 are obtained when sodium in /erf-butyl alcohol/tetrahydrofuran is used. Only a trace of the epimeric civ-product, formed as a result of / -face protonation, is found. The isolated double bond is not affected under the reaction conditions. 

Our initial plan was to make a systematic investigation of the structural features of ergosterol by replacing the ergosterol with other sterols which either lacked a particular feature,, the -unsaturation, or had some other Interesting aspect to them, e. ., altered stereochemistry. The contribution of the feature was then to be assessed by evaluation of the number of cells after three days. The cell population could be measured both visually and by means of a 16-channel Coulter counter which also permits determination of the distribution of cell sizes and volumes. In addition, extraction of the cells, or subcellular fractions, would permit us to examine the amount, distribution, and metabolism of the added sterol. 

Although the composition and structure of mammalian (mainly erythrocyte and myelin) membranes has received extensive study, little attention has been paid to the membranes of yeasts, fungi and protozoa. Extraction of lipids from these organisms suggest similarities in overall structure, although cholesterol, which has an almost universal distribution in mammalian cells was replaced by other sterols, e.g. ergosterol (14) in yeasts and fungi [126]. The presence of... 

The provitamins are more abundant in nature than the pure vitamins. Ergosterol is found in plants and yeast. 7-Dehydrocholesterol is the provitamin of man it is also found in animal skins. The most concentrated source, however, is in the snail Baccinum undatum, which contains about 27 percent 7-dehydrocholesterol in its dry weight. The D-vitamins themselves are not very widely distributed in nature. The richest sources are fish-liver oils, milk, and bird eggs. In consequence, the main source of the vitamins D2 and D3 is by irradiation of the corresponding pro-... 

Lang-Yona N, Dannemiller K, Yamamoto N, Burshtein N, Peccia J, Yarden O, Rudich Y (2012) Annual distribution of allergenic fungal spores in atmospheric particulate matter in the Eastern Mediterranean a comparative study between ergosterol and quantitative PCR analysis. Atmos Chem Phys 12 2681... 

Jasinghe, V.J. and Perera, C.O. 2005. Distribution of ergosterol in different tissues of mushrooms and its effect on the conversion of ergosterol to vitamin D2 by UV irradiation. Food Chemistry, 92(3), 541-546. 

Vitamin D can be viewed as a prohormone which arises by the action of ultraviolet light in the two-step process pictured in Fig. 20. Irradiation of 7-dehydrocholesterol in the skin can provide adequate amounts of vitamin D3 (cholecalciferol or calciol). The closely related vitamin D2 (ergocalciferol) arises from irradiation of the plant sterol ergosterol. This form of the vitamin has been widely used in fortification of milk. However, the natural vitamin D3 is more active in preventing rickets. The term vitamin Di was dropped when it was found to be a mixture of D2 and D3. The principal function of vitamin D is in the control of calcium metabolism. This control is exerted by polar, hydroxylated compounds of which the most important is la, 12-dihydroxy vitamin D3 (calcitriol). This hormone is distributed to all parts of the body. In cells of the intestinal lining it promotes uptake of calcium ions. It promotes reabsorption of both calcium and phosphate ions in the kidney tubules and increases blood calcium and depositon of calcium ions in bone. 

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