Membrane fluidity and lipid composition of fluconazole resistant and susceptible strains of Candida albicans isolated from diabetic patients / Fluidez e composição lipídica da membrana de cepas de Candida albicans resistentes e sensíveis ao fluconazol, isoladas de pacientes diabéticos

Ten clinical isolates of Candida albicans, five strains belonging to each of fluconazole resistant and susceptible groups isolated from diabetic patients, were studied for the membrane fluidity and lipid composition. Compared to fluconazole susceptible strains, fluconazole resistant ones exhibited enhanced membrane fluidity as measured by fluorescence polarization technique. The increased membrane fluidity was reflected in the decreased p-values exhibited by the resistant strains. On the other hand, susceptible isolates contained higher amount of ergosterol, almost twice as compared to resistant isolates which might have contributed to their lower membrane fluidity. However, no significant alteration was observed in the phospholipid and fatty acid composition of these isolates. Labeling experiments with fluorescamine dye revealed that the percentage of the exposed aminophospholipid, phosphatidylethanolamine was highest in the resistant strains as compared to the susceptible strains, indicating a possible overexpression of CDR1 and CDR2 genes in resistant strains. The results presented here suggest that the changes in the ergosterol content and overexpression of ABC transporter genes CDR1 and CDR2 could contributeto fluconazole resistance in C. albicans isolated from diabetic patients.

Dez isolados clínicos, sendo cinco resistentes e cinco sensíveis ao fluconazol, obtidos de pacientes diabéticos, foram estudados quanto à fluidez e composição química da membrana. Quando comparados aos isolados sensíveis ao fluconazol, os isolados resistentes apresentaram fluidez de membrana aumentada, conforme mensurado pela técnica de polarização fluorescente. A fluidez de membrana aumentada refletiu-se pelos valores mais baixos de p. Por outro lado, os isolados sensíveis continham quantidades mais elevadas de ergosterol, quase o dobro dos isolados resistentes, o que pode ter contribuído para a fluidez de membrana mais baixa. Entretanto, não se observou alteração significativa na composição fosfolipídica e de ácidos graxos nesses isolados. Experimentos de marcação com corante fluorescamina indicaram que a porcentagem de aminofosfolípides e fosfatidiletanolamina expostos foi mais elevada nos isolados resistentes do que nos sensíveis, indicando uma possível superexpressão dos genes CDR1 e CDR2 nos isolados resistentes. Os resultados aqui apresentados sugerem que alterações no teor de ergosterol e superexpressão dos genes ABC transportadores CDR1 e CDR2 podem contribuir na resistência ao fluconazol em isolados de C. albicans de pacientes diabéticos.

The effect of exposure to low temperature on the metabolism of carbohydrates, lipids and protein in the larvae of Philosamia ricini.

Exposure of the silkworm (Philosamia ricini) larvae to cold temperature (2°C) and subsequent exposure to room temperature (29° C) resulted in the mortality of the larvae. Cold exposure brought about significant decrease in enzymic activity of proteases, aminotransferases, diacylglycerol lipase and in the amounts of some haemolymph sugars and polyols. However, glycerol increased sharply in response to severe cold exposure. There was also a marked increase in the levels of protein, pyruvate, total free amino acids, total lipid, phospholipid and triacylglycerols. In the colder environment, carbohydrates served as the energy source. Glycerol appears to have conferred cryoprotection to the cold-stressed Philosamia ricini larvae.