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At least 811 records · Page 45Linked to original sources
PubMed1999

Trehalose hydrolysis is not required for human serum-induced dimorphic transition in Candida albicans: evidence from a tps1/tps1 mutant deficient in trehalose synthesis.

Exponential yeast-like cells of a Candida albicans wild-type strain exhibited strong capacity for germ tube formation in a glucose-containing medium (YPD) after induction with human serum at 37 degrees C, whereas the isogenic double disruptant tps1/tps1 mutant, which is deficient in trehalose synthesis, failed to produce germ tubes. In a medium without glucose (YP), the morphological transition fraction was roughly equivalent in both strains. Substitution of glucose by galactose or glycerol increased the number of wild-type proliferating cells able to enter the dimorphic program with no noticeable change in their trehalose content, while stationary cells, which accumulate a large amount of trehalose, did not form germ tubes. When fresh medium was added, a high proportion of these resting cells recovered their ability to carry out dimorphic transition. The tps1/tps1 mutant followed the same pattern of hyphae formation, despite the fact that it was unable to accumulate trehalose either during dimorphism induction or after several stress challenges. Furthermore, trehalose-6-phosphate synthase activity was barely detectable in the mutant. These results strongly suggest that serum-induced dimorphic transition does not require trehalose mobilization; they also support the idea that TPS1 is the only activity involved in trehalose biosynthesis in C. albicans.

Blood Proteins↗
PubMed1997

Synthesis and biological evaluation of potent glycosidase inhibitors: N-phenyl cyclic isourea derivatives of 5-amino- and 5-amino-C-(hydroxymethyl)-1,2,3,4-cyclopentanetetraols.

Twenty-four stereoisomers of 5-amino- and 5-amino-C-(hydroxymethyl)-1,2,3,4-cyclopentanetetraols and twenty-six of the corresponding N-phenyl cyclic isourea derivatives were assayed for inhibitory activity against six glycosidases. Among them, as has been expected for structure mimics of putative transition state glucopyranosyl cation for glycoside hydrolysis, 1L-(1,2,4,5/3)-5-amino-1-C-(hydroxymethyl)-1,2,3,4-cyclopentanetetrao l L-4 and its N-phenyl cyclic isourea derivative S-19 were shown to have strong inhibitory activity, IC50 4 x 10(-7) and 7.6 x 10(-9) M, respectively, against baker's yeast alpha-glucosidase. It has been analogously explained that compounds R,S-22 and R,S-26 possessed high inhibitory potency against Escherichia coli and bovine liver beta-galactosidases, respectively.

Animals↗
PubMed1996

Biotechnological applications of the disaccharide trehalose.

Trehalose is a disaccharide present in a variety of anhydrobiotic organisms which have the ability to promptly resume their metabolism after addition of water. It has been successfully used as a nontoxic cryoprotectant of enzymes, membranes, vaccines, animal and plant cells and organs for surgical transplants. It has been predicted that trehalose can also be used as an ingredient for dried and processed food. Therefore, the recent biotechnological applications of trehalose have imposed the standardization of methods for its production, as well as for its specific quantification.

Biotechnology↗
PubMed1997

Genetic variation at structural loci in the Glossina morsitans species group.

Gene diversity was investigated in four taxa of tsetse flies (Diptera: Glossinidae) including Glossina morsitans, G.m. centralis, G. Swynnertoni, and G. pallidipes. Histochemical tests were performed for 35-46 isozymes. Polymorphic loci were 20% in G. morsitans, 32% in G.m. centralis, 17.6% in G. swynnertoni, and 26% in G. pallidipes. Mean heterozygosities among all loci were 6.6% in G. morsitans morsitans, 6.0% in G.m. centralis, 7.1% in G. swynnertoni, and 6.8% pallidipes. Allozyme gene diversities were considerably less than those reported for many Diptera. The low gene diversities are probably related to small effective population sizes.

Animals↗
PubMed1986

Small intestinal mucosal toxicity of cis-platinum--comparison of toxicity with platinum analogues and dexamethasone.

Cis-platinum causes profound gastrointestinal symptoms in patients and these may persist for many days after drug administration. Gut mucosal toxicity may be a factor in the pathogenesis of such prolonged nausea, vomiting and anorexia. The effects of cis-platinum on mouse ileal mucosal architecture, villus epithelial cell influx and disaccharidase activity are described in comparison with dhe effects of two platinum analogues, CBDCA and CHIP. In addition the effect of dexamethasone, a useful drug in the palliation of cis-platinum-induced emesis, in combination with cis-platinum is described. Cis-platinum, CBDCA and CHIP cause profound reduction in crypt cell production rate (CCPR) and thus villus epithelial cell influx within hours of administration leading to villus stunting and diminished function. CBDCA showed the least profound effect with early rebound in CCPR by day 3. Cis-platinum and CHIP were roughly equitoxic to ileal crypts with rebound in CCPR being delayed until day 7. Similarly, CBDCA caused least reduction in disaccharidase activity with cis-platinum and CHIP being equitoxic. The addition of dexamethasone had no protective effect on the effects of cis-platinum on murine ileal mucosa and mice given the combination chronically had no weight gain over 18 weeks, their weight paralleling those receiving cis-platinum alone. The platinate compounds have differing degrees of intestinal mucosal toxicity but no direct inference can be drawn in respect to the clinical situation where CBDCA causes less gastrointestinal symptomatology than CHIP but where both cause less than cis-platinum. Dexamethasone does not act by mucosal protection to provide its useful effects in prolonged cis-platinum-induced gastrointestinal symptoms.

Animals↗
PubMed2000

The yeast A kinases differentially regulate iron uptake and respiratory function.

Yeast has three A kinase catalytic subunits, which have greater than 75% identity and are encoded by the TPK genes (TPK1, TPK2, and TPK3) [Toda, T., Cameron, S., Sass, P., Zoller, M. & Wigler, M. (1987) Cell 50, 277-287]. Although they are redundant for viability, the three A kinases are not redundant for pseudohyphal growth [Robertson, L. S. & Fink, G. R. (1998) Proc. Natl. Acad. Sci. USA 95, 13783-13787; Pan, X. & Heitman, J. (1999) Mol. Cell. Biol. 19, 4874-4887]; Tpk2, but not Tpk1 or Tpk3, is required for pseudohyphal growth. Genome-wide transcriptional profiling has revealed unique signatures for each of the three A kinases leading to the identification of additional functional diversity among these proteins. Tpk2 negatively regulates genes involved in iron uptake and positively regulates genes involved in trehalose degradation and water homeostasis. Tpk1 is required for the derepression of branched chain amino acid biosynthesis genes that seem to have a second role in the maintenance of iron levels and DNA stability within mitochondria. The fact that TPK2 mutants grow better than wild types on nonfermentable carbon sources and on media deficient in iron supports the unique role of Tpk2 in respiratory growth and carbon source use.

2-Acetolactate Mutase↗
PubMed1995

Trehalose as a possible precursor of the sulfated L-galactan in the ascidian tunic.

Among sulfated polysaccharides, those in the tunic of ascidians are unique: their major constituent sugar is galactose, which occurs exclusively in the L-enantiomeric form. Incorporation of D-[14C]glucose into tunic slices in vitro revealed that the cells epimerize D-glucose into L-galactose during biosynthesis of the sulfated polysaccharides. The interconversion of these two sugars involves exchange of hydrogen atoms at the epimerization sites with protons of the medium. Tunic cells also synthesize trehalose, although this disaccharide is not a prominent constituent of the tissue. Pulse-chase experiments using D-[14C]glucose reveal that incorporation of label into trehalose precedes the synthesis of the sulfated L-galactan. In addition, the loss of label from trehalose coincides with the appearance of label in the sulfated L-galactan. Based on these results, we speculate that trehalose in the ascidian tunic may be a precursor of the sulfated L-galactan.

Animals↗
PubMed1989

Causes and consequences of variation in energy storage in Drosophila melanogaster.

Variation in energy storage pools has a proximate cause variation in rates of influx and efflux from the pools, and it may, as an ultimate consequence, result in variation in fitness. The possibility of this chain of causal links motivates attempts to quantify the genetic correlations among pool sizes, enzyme activities and fitness components. In this report, homogenates from 83 second chromosome replacement lines of Drosophila melanogaster were analyzed to determine the amounts of stored triacylglycerols and glycogen as well as the activities of 11 enzymes in relevant metabolic pathways. The viabilities and fecundities of these same lines were determined by a segregation test using the SM5 balancer chromosome. Analysis of covariance revealed significant differences among lines in quantities of stored triacylglycerols and glycogen, as well as in activities of the assayed enzymes. Significant broad-sense genetic correlations were detected for a number of enzyme pairs. Some of the traits showed a significant correlation with viability and fecundity, including lipid and glycogen storage. Multiple regression models that fitted fitness components to linear and quadratic functions of the biochemical traits yielded highly significant fits. The partial regression coefficients indicate the shape of the selection gradient, and instances of significant directional and stabilizing selection were detected.

Analysis of Variance↗
PubMed1975

Intestinal disaccharidase and peroxidase activities in parenterally nourished rats.

The importance of the presence of food in the gastointestinal (GI) tract in maintaining normal enzyme activity in the small intestine was investigated in rats that were kept from eating for as long as 2 weeks. During this time animals were sustained on a nutrient solution administered intravenously. Enzyme activity and small bowel mass in these animals and similiar parameters in rats that were administered the same solution orally were compared with control groups fed an essentially isoenergetic diet of stock rat food and water. Disaccharidase and peroxidase levels in mucosal scrapings expressed as activity/milligram protein, activity/intestine, and activity/100 g body weight, were significantly reduced in intravenously nourished rats but not in rats receiving the solution orally. In addition to changes in enzyme activities, parenteral feeding was accompanied by a significant reduction in the small bowel weight:body weight ratio as compared with that of rats fed the stock diet or nutrient solution orally. Results support the conclusion that normal activity of intestinal enzymes spatially distributed with regard to depth within the mucosa depends on the presence of food in theGI tract and cannot be maintained at normal levels by total intravenous nutrition.

Animal Nutritional Physiological Phenomena↗
PubMed1983

The effect of severe zinc deficiency on activity of intestinal disaccharidases and 3-hydroxy-3-methylglutaryl coenzyme A reductase in the rat.

Specific activities of five enzymes were measured in intestinal mucosa of zinc-deficient rats and compared to activities in appropriate zinc-sufficient controls. Three disaccharidases were found to be significantly reduced in zinc deficiency. Alkaline phosphatase, a zinc metalloenzyme, also showed reduced activity. Activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-limiting enzyme of cholesterol synthesis, was elevated. It is possible that impaired carbohydrate digestion (reflected in disaccharidase activity) and even defective lipid absorption (reflected in reductase activity) may contribute to the poor nutrition and diarrhea of zinc deficiency.

Alkaline Phosphatase↗
PubMed2000

A rapid method for efficient gene replacement in the filamentous fungus Aspergillus nidulans.

The construction of mutant fungal strains is often limited by the poor efficiency of homologous recombination in these organisms. Higher recombination efficiencies can be obtained by increasing the length of homologous DNA flanking the transformation marker, although this is a tedious process when standard molecular biology techniques are used for the construction of gene replacement cassettes. Here, we present a two-step technology which takes advantage of an Escherichia coli strain expressing the phage lambda Red(gam, bet, exo) functions and involves (i) the construction in this strain of a recombinant cosmid by in vivo recombination between a cosmid carrying a genomic region of interest and a PCR-generated transformation marker flanked by 50 bp regions of homology with the target DNA and (ii) genetic exchange in the fungus itself between the chromosomal locus and the circular or linearized recombinant cosmid. This strategy enables the rapid establishment of mutant strains carrying gene knock-outs with efficiencies >50%. It should also be appropriate for the construction of fungal strains with gene fusions or promoter replacements.

Aspergillus nidulans↗
PubMed1976

Topographical relationship between sucrase and leucine beta-naphthylamidase on the microvilli membrane of rabbit intestinal mucosal cells.

The topographical relationship between sucrase [EC 3.2.1.26] and leucine beta-naphthylamidase (LNAase) on the microvilli membrane of rabbit small-intestinal mucosal cells was studied assuming that where enzymes with different antigenicities, A and B, are situated in close proximity on the surface of microvilli vesicles, the agglutination of vesicles by anti-A antibody is inhibited by the previous binding of monovalent fragments of anti-B antibody to enzyme B on the surface of vesicles. Like anti-sucrase antibody, anti-LNAase antibody quantitatively agglutinated microvilli vesicles. It inhibited the membrane-bound LNAase activity in the same manner as the detergent-solubilized activity. This inhibitory effect of anti-LNAase antibody was not interfered with by monovalent fragments of anti-sucrase antibody. However, the monovalent fragments inhibited vesicle agglutination by anti-LNAase antibody as well as by anti-sucrase antibody. These results indicate that LNAase is located on the outer surface of microvilli vesicles and suggest that LNAase and sucrase are situated in close proximity on the membrane surface of microvilli vesicles.

Agglutination↗