1,721,039 research outputs found
Induction of germ-tube formation by N-acetyl-D-glucosamine in Candida albicans.Uptake of inducer and germinative response.
No full textA number of strains of Candida albicans were tested for germ tube formation
after induction by N-acetyl-D-glucosamine (GlcNAc) and other simple (proline,
glucose plus glutamine) or complex (serum) compounds. A proportion of strains
(high responders) were induced to form germ tubes evolving to true hyphae by
GlcNAc alone or by proline or glucose plus glutamine mixture. The majority of
strains were low responders because they could be induced only by serum or
GlcNAc-serum medium. Two strains were found to be nonresponders: they grew
as pseudohyphae in serum. Despite minor quantitative differences, all strains
efficiently utilized GlcNAc for growth under the yeast form at 28°C. They also had
comparable active, inducible, and constitutive uptake systems for GlcNAc.
During germ tube formation in GlcNAc, the inducible uptake system was
modulated, as expected from induction and decay of GlcNAc kinase. Uranyl
acetate, at a concentration of 0.01 mM, inhibited both GlcNAc uptake and germ
tube formation and was reversed by phosphates. Germinating and nongerminating
cells differed in the rapidity and extent of GlcNAc incorporation into acidinsoluble
and alkali-acid-insoluble cell fractions. During germ tube formation
induced by proline, GlcNAc was almost totally incorporated into the acidinsoluble
fraction after 60 min. Moreover, hyphal development on induction by
either GlcNAc or proline was characterized by an apparent "uncoupling"
between protein and polysaccharide metabolism, the ratio between the two main
cellular constituents falling from more than 1 to less than 0.5 after 270 min of
development. The data suggest that utilization of the inducer for wall synthesis is
a determinant ofgerm tube formation in C. albicans but that the nature and extent
of inducer uptake is not a key event for this phenomenon to occur
Modulations of proteins synthesis associated with temperature shift in the pathogenic fungs Candida albicans.
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Nutrition-dependent modulations of proteins synthesis in Candida albicans during germ-tube formation or maintenance of the yeast form in N-acetyl-d-glucosamine media.
No full textAbstract Stationary phase, yeast-form cells of Candida albicans grown in glucose-yeast extract medium were shifted to N-acetylglucosamine (GlcNAc) and/or glucose medium, and the pattern of protein synthesized under conditions of a progressive decrease in the rate of total protein synthesis was analyzed by SDS-PAGE and autoradiography.
Marked temporal modulations in the rate of synthesis of some cytoplasmic proteins were detected both in cells forming germ-tubes (at 37°C) and in yeast cells (at 28°C). The major modulated components showed molecular weights of 63, 53, 48 and 34 kDa. These products could not be qualified as heat-shock or heat-stroke proteins, because analogous modulations were observed on shifting cells from 28°C to 37°C or from 28°C to 28°C. However, no marked modulations in the synthesis of specific proteins were detected when amino acids were added to the medium fostering germ-tube formation under conditions of unimpaired overall rate of protein synthesis.
It is suggested that the modulations observed in cells incubated in GlcNAc-glucose medium could represent a response to a nutritional stress
Low levels of both xanthine dehydrogenase and cellular retinol binding protein are responsible of the retinoic acid deficiency in malignant human mammary epithelial cells (abstract)
No full textProtective Effect of Sildenafil against Estradiol-induced ROS production
No full textSeveral reports suggest that xanthine dehydrogenase (XDH) and its oxidase form (XO) play an important role in various forms of ischemic and vascular injuries. Recently we have demonstrated that 17β-estradiol (E2) induces a significant decrease of the expression and activity of XDH and its conversion to XO in human mammary epithelial cells. E2 is known to induce upregulation of eNOS gene expression in aortic endothelial cells. In light of the ability of XO-derived O2• ̄ to combine with •NO to yield ONOO ̄, and considering that ONOO ̄ converts XDH to XO, it is important to protect tissues against the XO increased activity and ROS increased production, that would in turn react with •NO to augment ONOO ̄ production, thus creating a vicious cycle of oxidative stress. Our previous studies have indicated that sildenafil has a protective effect on human mammary epithelial cells as a consequence of the inhibition of XO and of the resulting decrease of free oxygen radical that may influence the expression of NADPH oxidase and PDE-5. We report that the contemporary inhibitory effect played by sildenafil on XO and PDE-5 is due to the structural modification induced by O2• ̄, which involves the release of a piperazine group able to inhibit XO
Estradiol Decreases Xanthine Dehydrogenase Enzyme Activity and Protein Expression in Non-Tumorigenic and Malignant Human Mammary Epithelial Cells
No full textThe retinoic acid deficiency in breast tumour epithelial cells has been ascribed to an insufficient expression of either the enzyme(s) involved in its biosynthesis or the cellular retinol binding protein (CRBP) or both. In an attempt to define the mechanisms underpinning retinoic acid deficiency in these cell model systems, we have investigated the potential regulatory effect of oestrogen (17b-estradiol) on one key player in retinoic acid biosynthesis, the xanthine dehydrogenase (XDH). This enzyme is consistently expressed and very active in non-malignant human mammary epithelial cells (HMEC), as opposed to tumour MDA-MB231 and MCF7 cells. In these latter two cell lines, as opposed to
HMEC cells, we observe a residual ability of XDH to produce retinoic acid from retinaldehyde and the inability to use retinol, as a consequence of a deficit in CRBP. In addition, estradiol treatment of MDA-MB231 and MCF7 cells decreases protein expression and activity of the enzyme, with no modification of the mRNA transcript levels, eventually leading to deteriorate further retinoic acid production
Produzione di biofilm (slime layer) in isolati clinici ed ambientali di Candida Parapsilosis: studio della variabilità ed analisi ultrastrutturale (M.E.S.).
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