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PubMed1974

Microbial water relations: features of the intracellular composition of sugar-tolerant yeasts.

Several factors contributed to differences in intracellular composition between sugar-tolerant (osmophilic) and nontolerant species of yeast. One such factor was the difference in accumulation of those nonelectrolytes whose uptake was not dominated by vigorous metabolism. In such cases (lactose and glycerol), the sugar-tolerant species had a much lower capacity for the solute than did the nontolerant species. Sucrose uptake was consistently different between all sugar-tolerant strains on the one hand and all nontolerant strains on the other. The difference was attributable in part to metabolism of sucrose by the nontolerant yeasts. The major difference between the two types of yeast, however, was the presence of one or more polyhydric alcohols at high concentrations within each of the sugar-tolerant strains but none of the nontolerant strains. In most cases the major polyol was arabitol. The solute concentration (and, hence, water availability) of the growth medium affected both the amount of arabitol produced by Saccharomyces rouxii and the proportion retained by the yeast after brief washing with water at 0 C. When the yeast was suspended in a buffer at 30 C, the polyol leaked out at a slow, constant, reproducible rate. The polyene antibiotic amphotericin B caused rapid release of polyol by the yeast, the rate being proportional to amphotericin concentration. Contact of the yeast with glucose (1 mM) caused an extremely rapid ejection of polyol which lasted less than 40 s. Some implications of these results are discussed, as is the role of the polyol as a compatible solute in determining the water relations of the yeast.

Alcohols↗
PubMed1967

Localization of indigenous yeast in the murine stomach.

Certain strains of yeast were cultured frequently from the feces of adult CFW mice and Long-Evans and Sprague-Dawley rats, but not from infants of those murine strains, or from adults or infants of NCS or NCS-D mice. When the yeasts could be cultured from the feces, they could also be grown from all areas of the digestive tracts of the animals, but especially from the stomachs, where they formed layers on the epithelium of the glandular mucosa. Three of the yeast isolates, one each from the three murine colonies, were provisionally classified in the genus Torulopsis of the asporogenous yeasts. These yeast strains failed to colonize the digestive tubes of suckling infant mice of either the CFW or NCS-D colonies. In contrast, they colonized the guts of adult NCS-D mice and formed layers in their stomachs; tests with the yeast from CFW mice revealed that this strain colonized the guts and formed layers in the stomachs of germ-free CFW mice. When established in NCS-D mice, the yeast strains did not affect qualitatively or quantitatively the growth of the animals or the composition of the bacterial flora in the gastrointestinal tracts. Moreover, they did not elicit an unusual inflammatory response in the digestive tracts; nor were they pathogenic for NCS mice when injected by the intraperitoneal or intravenous routes. The yeasts thus appear to be harmless saprophytes that are able to flourish in the environment of the surface of the secreting epithelium of the murine stomach. The findings conform with the view that some types of microorganisms of the gastrointestinal tract are not just mixed randomly but rather occupy microenvironments in almost pure culture. This concept is important to the understanding of the ecology of the gut microflora.

Journal Article↗
PubMed2005

CHROMagar Candida as the sole primary medium for isolation of yeasts and as a source medium for the rapid-assimilation-of-trehalose test.

The chromogenic medium BBL CHROMagar Candida (CAC) was evaluated as a sole primary medium for the isolation of yeasts from clinical specimens in which yeasts are the primary concern. Additionally, the reliability of the rapid-assimilation-of-trehalose (RAT) test in yielding correct results with isolates taken from CAC was assessed. A total of 270 throat, urine, and genital (TUG) specimens were streaked onto CAC, Sabouraud dextrose agar (SDA), inhibitory mold agar (IMA), and Mycosel (MYC). A total of 69 blood culture broths that were smear positive for yeast were streaked onto CAC and SDA. A 1-h RAT test (NCCLS M35-A) was performed simultaneously on isolates from CAC and SDA. A total of 112 TUG specimens yielded yeast colonies (CAC, 111 colonies; IMA, 105; SDA, 103; MYC, 91). The 69 blood culture yeasts grew on both CAC and SDA. Mixed cultures of yeasts were detected on 11 CAC plates but were unrecognized on other media. Colonies suspected of being C. glabrata on 32 CAC plates were all RAT test positive and confirmed to be C. glabrata; of 59 colonies with various characteristics of color and morphology on CAC, none were RAT positive, and all were conventionally identified as yeasts other than C. glabrata (sensitivity and specificity, 100%). The same isolates from SDA tested for RAT produced six false negatives and no false positives (sensitivity, 81%; specificity, 100%). The results show that CAC can be used as the sole primary medium for recovery of yeasts from clinical specimens. Additionally, isolates grown on CAC yield excellent results with the RAT test utilized in this study.

Candida↗
PubMed1996

Structure-function comparisons of the proapoptotic protein Bax in yeast and mammalian cells.

Expression of the proapoptotic protein Bax under the control of a GAL10 promoter in Saccharomyces cerevisiae resulted in galactose-inducible cell death. Immunofluorescence studies suggested that Bax is principally associated with mitochondria in yeast cells. Removal of the carboxyl-terminal transmembrane (TM) domain from Bax [creating Bax (deltaTM)] prevented targeting to mitochondrial and completely abolished cytotoxic function in yeast cells, suggesting that membrane targeting is crucial for Bax-mediated lethality. Fusing a TM domain from Mas70p, a yeast mitochondrial outer membrane protein, to Bax (deltaTM) restored targeting to mitochondria and cytotoxic function in yeast cells. Deletion of four well-conserved amino acids (IGDE) from the BH3 domain of Bax ablated its ability to homodimerize and completely abrogated lethality in yeast cells. In contrast, several Bax mutants which retained ability to homodimerize (deltaBH1, deltaBH2, and delta1-58) also retained at least partial lethal function in yeast cells. In coimmunoprecipitation experiments, expression of the wild-type Bax protein in Rat-1 fibroblasts and 293 epithelial cells induced apoptosis, whereas the Bax (deltaIGDE) mutant failed to induce apoptosis and did not associate with endogenous wild-type Bax protein. In contrast to yeast cells, Bax (deltaTM) protein retained cytotoxic function in Rat-1 and 293 cells, was targeted largely to mitochondria, and dimerized with endogenous Bax in mammalian cells. Thus, the dimerization-mediating BH3 domain and targeting to mitochondrial membranes appear to be essential for the cytotoxic function of Bax in both yeast and mammalian cells.

Animals↗
PubMed1997

Multicopy suppressors of phenotypes resulting from the absence of yeast VDAC encode a VDAC-like protein.

The permeability of the outer mitochondrial membrane to most metabolites is believed to be based in an outer membrane, channel-forming protein known as VDAC (voltage-dependent anion channel). Although multiple isoforms of VDAC have been identified in multicellular organisms, the yeast Saccharomyces cerevisiae has been thought to contain a single VDAC gene, designated POR1. However, cells missing the POR1 gene (delta por1) were able to grow on yeast media containing a nonfermentable carbon source (glycerol) but not on such media at elevated temperature (37 degrees C). If VDAC normally provides the pathway for metabolites to pass through the outer membrane, some other protein(s) must be able to partially substitute for that function. To identify proteins that could functionally substitute for POR1, we have screened a yeast genomic library for genes which, when overexpressed, can correct the growth defect of delta por1 yeast grown on glycerol at 37 degrees C. This screen identified a second yeast VDAC gene, POR2, encoding a protein (YVDAC2) with 49% amino acid sequence identity to the previously identified yeast VDAC protein (YVDAC1). YVDAC2 can functionally complement defects present in delta por1 strains only when it is overexpressed. Deletion of the POR2 gene alone had no detectable phenotype, while yeasts with deletions of both the POR1 and POR2 genes were viable and able to grow on glycerol at 30 degrees C, albeit more slowly than delta por1 single mutants. Like delta por1 single mutants, they could not grow on glycerol at 37 degrees C. Subcellular fractionation studies with antibodies which distinguish YVDAC1 and YVDAC2 indicate that YVDAC2 is normally present in the outer mitochondrial membrane. However, no YVDAC2 channels were detected electrophysiologically in reconstituted systems. Therefore, mitochondrial membranes made from wild-type cells, delta por1 cells, delta por1 delta por2 cells, and delta por1 cells overexpressing YVDAC2 were incorporated into liposomes and the permeability of resulting liposomes to nonelectrolytes of different sizes was determined. The results indicate that YVDAC2 does not confer any additional permeability to these liposomes, suggesting that it may not normally form a channel. In contrast, when the VDAC gene from Drosophila melanogaster was expressed in delta por1 yeast cells, VDAC-like channels could be detected in the mitochondria by both bilayer and liposome techniques, yet the cells failed to grow on glycerol at 37 degrees C. Thus, channel-forming activity does not seem to be either necessary or sufficient to restore growth on nonfermentable carbon sources, indicating that VDAC mediates cellular functions that do not depend on the ability to form channels.

Amino Acid Sequence↗
PubMed2000

Sli2 (Ypk1), a homologue of mammalian protein kinase SGK, is a downstream kinase in the sphingolipid-mediated signaling pathway of yeast.

ISP-1 is a new type of immunosuppressant, the structure of which is homologous to that of sphingosine. In a previous study, ISP-1 was found to inhibit mammalian serine palmitoyltransferase, the primary enzyme involved in sphingolipid biosynthesis, and to reduce the intracellular pool of sphingolipids. ISP-1 induces the apoptosis of cytotoxic T cells, which is triggered by decreases in the intracellular levels of sphingolipids. In this study, the inhibition of yeast (Saccharomyces cerevisiae) proliferation by ISP-1 was observed. This ISP-1-induced growth inhibition was also triggered by decreases in the intracellular levels of sphingolipids. In addition, DNA duplication without cytokinesis was detected in ISP-1-treated yeast cells on flow cytometry analysis. We have cloned multicopy suppressor genes of yeast which overcome the lethal sphingolipid depletion induced by ISP-1. One of these genes, SLI2, is synonymous with YPK1, which encodes a serine/threonine kinase. Kinase-dead mutants of YPK1 did not show any resistance to ISP-1, leading us to predict that the kinase activity of the Ypk1 protein should be essential for this resistance to ISP-1. Ypk1 protein overexpression had no effect on sphingolipid biosynthesis by the yeast. Furthermore, both the phosphorylation and intracellular localization of the Ypk1 protein were regulated by the intracellular sphingolipid levels. These data suggest that the Ypk1 protein is a downstream kinase in the sphingolipid-mediated signaling pathway of yeast. The Ypk1 protein was reported to be a functional homologue of the mammalian protein kinase SGK, which is a downstream kinase of 3-phosphoinositide-dependent kinase 1 (PDK1). PDK1 phosphotidylinositol (PI) is regulated by PI-3,4,5-triphosphate and PI-3,4-bisphosphate through the pleckstrin homology (PH) domain. Overexpression of mammalian SGK also overcomes the sphingolipid depletion in yeast. Taking both the inability to produce PI-3,4, 5-triphosphate and PI-3,4-bisphosphate and the lack of a PH domain in the yeast homologue of PDK1, the Pkh1 protein, into account, these findings further suggest that yeast may use sphingolipids instead of inositol phospholipids as lipid mediators.

Fatty Acids, Monounsaturated↗
PubMed2004

Vaginal yeast colonisation, prevalence of vaginitis, and associated local immunity in adolescents.

OBJECTIVES: To evaluate point prevalence vaginal yeast colonisation and symptomatic vaginitis in middle adolescents and to identify relation of these yeast conditions with reproductive hormones, sexual activity, sexual behaviours, and associated local immunity. METHODS: Middle adolescent females (n = 153) were evaluated for sexually transmitted infections (STIs), asymptomatic yeast colonisation, and symptomatic vulvovaginal candidiasis (VVC) by standard criteria. Also evaluated were local parameters, including vaginal associated cytokines, chemokines, and antibodies, vaginal epithelial cell antifungal activity, and Candida specific peripheral blood lymphocyte responses. Correlations between yeast colonisation/vaginitis and local immunomodulators, reproductive hormones, douching, sexual activity, condom use, and STIs were identified. RESULTS: Rates of point prevalence asymptomatic yeast colonisation (22%) were similar to adults and similarly dominated by Candida albicans, but with uncharacteristically high vaginal yeast burden. In contrast with the high rate of STIs (18%), incidence of symptomatic VVC was low (<2%). Immunological properties included high rates of Candida specific systemic immune sensitisation, a Th2 type vaginal cytokine profile, total and Candida specific vaginal antibodies dominated by IgA, and moderate vaginal epithelial cell anti-Candida activity. Endogenous reproductive hormones were in low concentration. Sexual activity positively correlated with vaginal yeast colonisation, whereas vaginal cytokines (Th1, Th2, proinflammatory), chemokines, antibodies, contraception, douching, or condom use did not. CONCLUSION: Asymptomatic vaginal yeast colonisation in adolescents is distinct in some ways with adults, and positively correlates with sexual activity, but not with local immunomodulators or sexual behaviours. Despite several factors predictive for VVC, symptomatic VVC was low compared to STIs.

Adolescent↗
PubMed1988

Interaction of Candida albicans with genital mucosa: effect of sex hormones on adherence of yeasts in vitro.

Findings from our previous studies revealed a correlation between the level of adherence in vitro of Candida albicans to human exfoliated vaginal epithelial cells (VEC) and the hormonal status of the cell donors. In the present study we investigated the effect of the sex hormones estradiol, estriol, progesterone, and testosterone on the binding of the yeasts to HeLa cell lines and VEC in vitro. Monolayers of HeLa cells were exposed to the hormones and yeasts under controlled conditions. The number of adherent yeasts per square millimetre of HeLa cell monolayers and the percentage of VEC with adherent yeasts was estimated by microscopic counts. The results showed that the tested sex hormones affected at various degrees the adhesion of yeasts to HeLa cells or VEC. Progesterone had the most marked effect, leading to a significant increase in the number of adherent yeasts to HeLa cells or in the percentage of adhesion of VEC. In addition, VEC were separated on Percoll gradients into the two cell types: superficial (S) and intermediate (I), cell types which appear physiologically under increased serum levels of estradiol or progesterone, respectively. Adhesion assays with the separated cell populations revealed an increased binding capacity of the I cells. The finding that progesterone increased the adherence of yeasts to genital mucosa and that VEC of the I type have a higher capacity to adhere the yeasts is compatible with our previous observation that increased numbers of I cells, appearing under high level of progesterone, are found in situations known to have predisposition to vaginal candidiasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Candida albicans↗
PubMed1996

Changes in glutathione metabolic enzymes during yeast-to-mycelium conversion of Candida albicans.

Candida albicans is a dimorphic yeast capable of producing alternate morphological forms (yeast or mycelium) in response to environmental changes. The intracellular level of glutathione, which helps to maintain the redox potential of the cell, is decreased significantly during the thermal induction of yeast-to-mycelium conversion. The reason for the decline of glutathione in the mycelial form is not understood. We have, therefore, investigated the levels of glutathione reductase, glutathione S-transferase, gamma-glutamyltranspeptidase, and glutathione peroxidase, four key enzymes involved in glutathione metabolism, in the yeast and mycelial forms. Yeast cells of C. albicans 3153A were induced in Lee's medium (pH 6.5) at 37 degrees C for 3 h to produce germ tubes. Cell lysates were prepared from yeast and mycelial cells, and glutathione reductase, glutathione S-transferase, gamma-glutamyltranspeptidase, and glutathione peroxidase were assayed spectrophotometrically. There was a 640% increase of the level of gamma-glutamyltranspeptidase in the germ tubes as compared with the yeast cells. No other significant alteration of the levels of enzymes was noted. This increased activity of gamma-glutamyltranspeptidase, which cleaves the glutamic acid residue of glutathione (Glu-Cys-Gly) appears to be, at least in part, responsible for the rapid decrease of the intracellular glutathione in C. albicans during the yeast-to-mycelium conversion.

Amino Acid Sequence↗
PubMed2003

Differences in the way a mammalian cell and yeast cells coordinate cell growth and cell-cycle progression.

BACKGROUND: It is widely believed that cell-size checkpoints help to coordinate cell growth and cell-cycle progression, so that proliferating eukaryotic cells maintain their size. There is strong evidence for such size checkpoints in yeasts, which maintain a constant cell-size distribution as they proliferate, even though large yeast cells grow faster than small yeast cells. Moreover, when yeast cells are shifted to better or worse nutrient conditions, they alter their size threshold within one cell cycle. Populations of mammalian cells can also maintain a constant size distribution as they proliferate, but it is not known whether this depends on cell-size checkpoints. RESULTS: We show that proliferating rat Schwann cells do not require a cell-size checkpoint to maintain a constant cell-size distribution, as, unlike yeasts, large and small Schwann cells grow at the same rate, which depends on the concentration of extracellular growth factors. In addition, when shifted from serum-free to serum-containing medium, Schwann cells take many divisions to increase their size to that appropriate to the new condition, suggesting that they do not have cell-size checkpoints similar to those in yeasts. CONCLUSIONS: Proliferating Schwann cells and yeast cells seem to use different mechanisms to coordinate their growth with cell-cycle progression. Whereas yeast cells use cell-size checkpoints, Schwann cells apparently do not. It seems likely that many mammalian cells resemble Schwann cells in this respect.

Animals↗
PubMed1986

Unexpected presence of estrogens in culture medium supplements: subsequent metabolism by the yeast Sacchromyces cerevisiae.

We have previously shown the presence of 17 beta-estradiol in extracts of commercially prepared Saccharomyces cerevisiae ss well as the production of estradiol by yeast grown in the laboratory. In our current study, yeast grown in a chemically defined medium synthesized estradiol in only small amounts, (less than 500 pg/liter). We have analyzed a variety of media commonly used for growing yeast and found that substantial estradiol production (greater than 5 ng/liter) was obtained when yeast were grown in medium supplemented with Bacto-peptone. The peptone was shown to contain significant amounts of estrone, and the results of the experiments establish a precursor-product relationship where estrone from the medium is metabolized to estradiol by S. cerevisiae. Studies with added [3H]estrone demonstrated rapid conversion into [3H]estradiol and a 3H-labeled nonpolar estrogen derivative. The commercially obtained yeast used previously had been grown in a molasses medium. We demonstrate here that the molasses medium contains substantial amounts of estrone and estradiol. We conclude that the conversion of estrone in a culture medium to estradiol in laboratory grown yeast and estrone and estradiol present in the commercially grown yeast medium account for the majority of estradiol found in yeast.

Chromatography, High Pressure Liquid↗
PubMed1992

Ligand-dependent and -independent function of the transactivation regions of the human estrogen receptor in yeast.

The estrogen receptor (ER) is a transcription factor involved in steroid hormone signal transduction in higher eukaryotes. The receptor also functions as a ligand-dependent transcriptional activator when introduced into Saccharomyces cerevisiae (baker's yeast), which suggests that at least some of the components of the signal transduction pathway are conserved between yeast and mammalian cells, and, moreover, allows the possibility of using this simple eukaryotic organism to dissect receptor function. However, whether the ER actually activates transcription in a mechanistically similar fashion in yeast and mammalian cells is unclear, since it has been reported that the transactivation function within the hormone binding domain (TAF-2) does not function in yeast. In this report, we have characterized the activity of the transactivation functions of the ER in yeast. Our results indicate that both TAF-2 and the N-terminal transactivation region (TAF-1) are functional in yeast and contribute synergistically to the receptor's total activity. These results are consistent with those obtained in mammalian cells. Furthermore, we show that in yeast the antagonistic effects of the antiestrogen nafoxidine arise from a modulation of the synergistic interactions of TAF-1 and TAF-2, and not simply from an inactivation of TAF-2 by antihormone. Finally, we characterize the effect of ER deletion mutants on chromatin structure in yeast. Our data lend support to the view that the formation of competent transcriptional initiation complexes requires a precise disruption of chromatin structure.

Animals↗
PubMed1994

Unusual chromosome structure of fission yeast DNA in mouse cells.

Chromosomes from the fission yeast Schizosaccharomyces pombe have been introduced into mouse cells by protoplast fusion. In most cell lines the yeast DNA integrates into a single site within a mouse chromosome and results in striking chromosome morphology at metaphase. Both light and electron microscopy show that the yeast chromosome region is narrower than the flanking mouse DNA. Regions of the yeast insert stain less intensely with propidium iodide than surrounding DNA and bear a morphological resemblance to fragile sites. We investigate the composition of the yeast transgenomes and the modification and chromatin structure of this yeast DNA in mouse cells. We suggest that the underlying basis for the structure we see lies above the level of DNA modification and nucleosome assembly, and may reflect the attachment of the yeast DNA to the rodent cell nucleoskeleton. The yeast integrant replicates late in S phase at a time when G bands of the mouse chromosomes are being replicated, and participates in sister chromatid exchanges at a high frequency. We discuss the implications of these studies to the understanding of how chromatin folding relates to metaphase chromosome morphology and how large stretches of foreign DNA behave when introduced into mammalian cells.

Anaphase↗
PubMed2006

Sake yeast suppresses acute alcohol-induced liver injury in mice.

Brewer's and baker's yeasts appear to have components that protect from liver injury. Whether sake yeast, Saccharomyces cerevisiae Kyokai no. 9, also has a hepatoprotective effect has not been examined. Here we show that sake yeast suppresses acute alcoholic liver injury in mice. Male C57BL/6 mice that had been fed a diet containing 1% sake yeast for two weeks received three doses of ethanol (5 g/kg BW). In the mice fed sake yeast, ethanol-induced increases in triglyceride (TG) and glutamate pyruvate transaminase (GPT) were significantly attenuated and hepatic steatosis was improved. In addition, sake yeast-fed mice showed a smaller decrease in hepatic S-adenosylmethionine (SAM) level and a smaller increase in plasma homocysteine (Hcy) level after ethanol treatment than the control mice, suggesting that a disorder of methionine metabolism in the liver caused by ethanol was relieved by sake yeast. These results indicate that sake yeast protects against alcoholic liver injury through maintenance of methionine metabolism in the liver.

Acute Disease↗
PubMed2000

Expanding world of ballistosporous yeasts: Distribution in the phyllosphere, systematics and phylogeny.

Ecological and systematic aspects of ballistosporous yeasts inhabiting the phyllosphere of the Asia-Pacific region were reviewed in the light of recent advances. In the past 20 years, the extensive isolation studies of ballistosporous yeasts were carried out in the Asia-Pacific region, and the following new species were found in the phyllosphere of the main island of Japan, of the Ogasawara Islands in the Pacific Ocean, and of Thailand, New Zealand, and the Yunnan Province of China: Bensingtonia ingoldii, B. intermedia, B. miscanthi, B. naganoensis, B. musae, B. sakaguchii, B. subrosea, B. thailandica, and B. yamatoana; Bullera boninensis, B. coprosmaensis, B. hannae, B. huiaensis, B. miyagiana, B. mrakii, B. oryzae, B. penniseticola, B. pseudoalba, B. schimicola, B. sinensis, B. unica, B. variabilis, and B. waltii; Kockovaella imperatae, K. machilophila, K. phaffii, K. sacchari, K. schimae, and K. thailandica; Sporobolomyces blumeae, S. coprosmae, S. coprosmicola, S. dimmenae, S. draycophyllus, S. falcatus, S. griseoflavus, S. inositophilus, S. lactophilus, S. linderae, S. novazealandicus, S. nylandii, S. oryzicola, S. poonsookiae, S. ruber, S. sasicola, S. subbrunneus, S. taupoensis, S. vermiculatus, S. xanthus, and S. yunnanensis; and Udeniomyces megalosporus. Yeast species containing Q-10(H(2)), a monohydrated ubiquinone, have long been considered to be rare yeasts; however, these yeasts were proved to be common in the tropical and subtropical phyllosphere of Asia. The chemotaxonomic and molecular phylogenetic studies based on the sequence analysis of 18S rDNA revealed the heterogeneity of ballistosporous yeasts, which comprised species with polyphyletic phylogenetic origins. A new phylogenetic cluster, Subbrunneus, was newly found in the class Urediniomycetes as the fifth phylogenetical cluster of this class, based on the analysis of 18S rDNA sequences. The Subbrunneus cluster comprises four ballistosporous yeast species found in the phyllosphere of Japan and New Zealand. The future perspectives of basidiomycetous yeast systematics are discussed.

Journal Article↗
PubMed1980

Beneficial effect of chromium-rich yeast on glucose tolerance and blood lipids in elderly subjects.

Twenty-four volunteers, mean age 78, including eight mildly non-insulin-dependent diabetics, were randomly allocated to one of two groups and were fed (daily for 8 wk) 9 g of either chromium-rich brewers' yeast (experimental) or chromium-poor torula yeast (control). Before and after yeast supplementation, the serum glucose and insulin response to 100 g oral glucose was measured at 30 min intervals for 2 h. Fasting serum cholesterol, total lipids, and triglycerides were also determined. In the total experimental group (normals + diabetics) and in both the diabetic and nondiabetic experimental subgroups, glucose tolerance improved significantly and insulin output decreased after supplementation. Cholesterol and total lipids fell significantly after supplementation in the total experimental group. The cholesterol decrease was particularly marked in hypercholesterolemic subjects (cholesterol > 300 mg/dl). In the control group, no significant change in glucose tolerance, insulin, triglycerides, or total lipids was found. Cholesterol was significantly lowered in the nondiabetic but not in the diabetic group. Thus, chromium-rich brewers' yeast improved glucose tolerance and total lipids in elderly subjects, while chromium-poor torula yeast did not. An improvement in insulin sensitivity also occurred with brewers' yeast supplementation. This supports the thesis that elderly people may have a low level of chromium and that an effective source for chromium repletion, such as brewers' yeast, may improve their carbohydrate tolerance and total lipids. The improvement in serum cholesterol in some control subjects, as well as in the total experimental group, also suggests the presence of a hypocholesterolemic factor other than chromium in both brewers' and torula yeast.

Aged↗
PubMed2002

Influence of yeast culture on ruminal microbial metabolism in continuous culture.

A continuous culture study was conducted to evaluate the effect of two different yeast cultures on ruminal microbial metabolism. The treatments were a) control lactation ration, b) yeast culture 1 (YC1, Diamond-V XP) and c) yeast culture 2 (YC2, A-Max), both fed at an equivalent of 57 g/head per day. The results showed that both yeast culture products increased dry matter (DM) digestion, propionic acid production, and protein digestion compared with the control. Yeast culture 1 demonstrated an increase in molar percentage of propionic acid, a reduction in acetic acid, and a lower mean nadir (daily low) pH compared with YC2. Ruminal cultures treated with YC digested more protein and contributed less bypass N than control. Supplementing YC2 resulted in a tendency for higher microbial N/kg DM digestion than YC1. Yeast culture 1 resulted in production of rumen microbes containing less protein and more ash than YC2. These results support previous research findings that yeast culture does influence microbial metabolism, and specific yeast cultures may have different modes of action.

Acetic Acid↗
PubMed2004

Cytochrome C oxidase III interacts with hepatitis B virus X protein in vivo by yeast two-hybrid system.

AIM: To screen and identify the proteins which interact with hepatitis B virus (HBV) X protein in hepatocytes by yeast two-hybrid system and to explore the effects of X protein in the development of hepatocellular carcinoma (HCC). METHODS: With HBV X gene amplified by polymerase chain reaction (PCR), HBV X bait plasmid, named pAS2-1-X, was constructed by yeast-two hybridization system3 and verified by auto-sequencing assay. pAS2-1-X was transformed into the yeast AH109, and X-BD fusion protein expressed in the yeast cells was detected by Western blotting. The yeast cells cotransformed with pAS2-1-X and normal human liver cDNA library were grown in selective SC/-trp-leu-his-ade medium. The second screen was performed with beta-gal activity detection, and false positive clones were eliminated by segregation analysis, true positive clones were amplified, sequenced and analyzed with bioinformatics. Mating experiment was performed to confirm the binding of putative proteins to X protein in the yeast cells. RESULTS: Bait plasmid pAS2-1-X was successfully constructed and pAS2-1-X correctly expressed BD-X fusion protein in yeast AH109. One hundred and three clones grew in the selective SC/-trp-leu-his-ade medium, and only one clone passed through beta-gal activity detection and segregation analysis. The inserted cDNA fragment showed high homology with Homo sapiens cytochrome C oxidase III (COXIII). Furthermore, mating experiment identified that the binding of COXIII to X protein was specific. CONCLUSION: COXIII protein is a novel protein that can interact with X protein in vivo by yeast two-hybrid system, and may contribute to the development of HCC through the interaction with X protein.

Carcinoma, Hepatocellular↗