Possible role of calcium in phospholipid synthesis of Microsporum gypseum.

The effect of calcium on lipid synthesis in Microsporum gypseum was examined by growing these cells in calcium supplemented (1 mM to 10 mM) medium. Maximum incorporation of [14C]acetate into total lipids and phospholipids was observed in cells grown with 6 mM calcium. This was probably due to a 3-fold increase in total calcium levels as incorporation of label was inhibited in total lipids (33%) and phospholipids (20.5%) in calcium-grown cells which were preincubated with the calcium specific chelator ethylene glycolbis (beta-aminoethyl ester) N,N,N',N',-tetracetate (EGTA). Increased incorporation of [14C]acetate into phospholipids was further supported by increase in the activity of key phospholipid biosynthetic enzymes (glycerolkinase and glycerol-3-phosphate acyltransferase) as well as the increase in phospholipid content in calcium-grown cells, which suggests a correlation between increased calcium levels and phospholipid biosynthesis in M. gypseum.

Effect of supplementation of ergosterol on miconazole action in vivo and in vitro in Candida albicans.

Ergosterol was observed to alter the lipid composition of C. albicans 3153 selectively, resulting in steep rise in ergosterol content with marginal changes in other lipids content. Supplementation of ergosterol in presence or absence of cerulenin made cells more protective towards the miconazole drug. However, when the same experiments were carried out with liposomes prepared from the lipid extracts of control and supplemented cells, the pattern obtained show a little deviation from the in vivo experiments thus indicating that in addition to lipids, other cell components like proteins also affect interaction of miconazole with C. albicans.

Lipids of Candida albicans: subcellular distribution and biosynthesis.

Lipids constituted around 5% of the dry weight in Candida albicans 3153, while sterols and phospholipids accounted for 1.2% and 1.1% respectively. Phospholipids were mainly localized in the microsomal fraction; phosphatidylserine (PS), phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) were the major phospholipids. Incorporation studies with [14C]acetate and [32P]orthophosphoric acid demonstrated that PS was synthesized at the highest rate followed by PC, PE and PI. There was little difference in either the content of the rate of biosynthesis of PC, PE and PI. Incorporation of labelled serine, ethanolamine and choline revealed serine to be a precursor for PC, PE and PS, ethanolamine for PC and PE, and choline for PC biosynthesis only.

Subcellular localization of enzymes of phospholipid metabolism in Candida albicans.

The intracellular location of various enzymes involved in the metabolism of phospholipids of Candida albicans was studied. Among the biosynthetic enzymes, phosphatidylserine synthetase was found to be localized in the microsomes; choline kinase and ethanolamine kinase were cytosolic; acyltransferase was localized in the particulate fraction and glycerol kinase and phosphatidic acid phosphatase were distributed in both the microsomal and cytosolic fractions. Phospholipase A and phospholipase C were abundant in the microsomes and phospholipase C was also detected in the cytosol. Lysophospholipase and glycerophosphocholine diesterase were distributed mainly in the mitochondria. Lipase activity was also detected in this fungus. Based on the enzymes detected in this study we have postulated pathways of phospholipid metabolism in C. albicans.

Influence of lipid composition on the sensitivity of Candida albicans to antifungal agents.

Cerulenin, a specific inhibitor of fatty acid and sterol biosyntheses, inhibited growth and lipid synthesis in C. albicans, which on supplementing the growth medium with optimum concentrations of fatty acids was reversed. Significant changes in the levels of phospholipids and sterols were observed in fatty acid-supplemented cells. Altered phospholipids and their fatty acid profile rendered cells more resistant to miconazole and thereby more permeable to [3H]proline. Thus it appears that fatty acid composition plays an important role in determining the permeability susceptibility of C. albicans to drugs.

Effect of an Ayurvedic compound preparation on the ability of rat urine to influence mineral phase formation.

Rat urine could inhibit not only the in vitro initial precipitation of calcium and phosphate/oxalate ions as mineral phase but also the subsequent growth of the preformed mineral phase. Oral administration of the aqueous extract of a commercially available Ayurvedic compound preparation to rats, was found to significantly increase the ability of the urine samples to inhibit both the initial mineral phase formation and its subsequent growth.