Anxiety-like Behavior in Female Sprague Dawley Rats Associated with Cecal Clostridiales

The relationship between the microbiota profile and exposure to stress is not well understood. Therefore, we used a rat model of unpredictable chronic mild stress (UCMS) to investigate this relationship. Depressive-like behaviors were measured in Female Sprague Dawley rats using the sucrose preference test and the Porsolt swim test. Anxiety-like behaviors were measured with the light-dark box test. Fecal corticosterone, cecal microbiota (composition and organic acids), plasma gut permeability (lipopolysaccharide-binding protein, LBP) and plasma inflammation (12 cytokines) markers were measured. Atypical behaviors were observed in female rats following UCMS, but no depressive-like behaviors were observed. Circulating concentrations of cytokines granulocyte-macrophage colony-stimulating factor and cytokine-induced neutrophil chemoattractant 1 were higher in UCMS-exposed female rats; plasma LBP and cecal organic acid levels remained unchanged. Our results reflect a resilient and adaptive phenotype for female SD rats. The relative abundance of taxa from the Clostridiales order and Desulfovibrionaceae family did, however, correlate both positively and negatively with anxiety-like behaviors and plasma cytokine concentrations, regardless of UCMS exposure, supporting the brain-to-gut influence of mild anxiety with a microbiota profile that may involve inflammatory pathways.

H. pylori Pattern Gastritis with Negative Helicobacter Immunohistochemical Stain: Does A Specific Comment in Pathology Report Impact Clinical Management?

Introduction/Objective

The clinical significance of H. pylori (HP) pattern of gastritis with a negative Helicobacter IHC stain on gastric biopsy is unclear. Some pathologists report this pattern in cases that are highly suggestive of HP infection with a comment raising the possibility of HP infection; however, the subsequent clinical management of these patients has not been well described.

Methods/Case Report

We conducted a retrospective comparison study of patients with gastric biopsy between 2016 and 2019. Group 1 included patients with chronic active or chronic inactive gastritis and negative HP IHC with a comment stating the gastritis pattern is suggestive of HP. Group 2 included patients with chronic active or chronic inactive gastritis and negative HP IHC with no comment about HP pattern.

Results (if a Case Study enter NA)

We identified 60 patients in Group 1 which were compared to 63 patients in Group 2. Group 1 more frequently had history of HP (48.3% vs. 29.1%, p<0.05). After diagnosis, Group 1 more frequently received treatment (51.7% vs. 20.6%, p<0.001). Of those who received treatment, Group 1 more frequently received HP treatment (triple or quadruple therapy; 21.7% vs. 1.6%, p<0.001). History of HP did not affect whether a patient was treated (p>0.05). Following post-biopsy HP treatment, more patients in Group 1 received fecal antigen test (23.7% vs. 5.5%, p<0.01). Age, gender, NSAID and PPI use did not differ between groups.

Conclusion

Adding the diagnostic comment raising the possibility of HP for patients with HP pattern gastritis with negative HP IHC changes clinical management and it is independent of patients’ prior HP history.

Complementary Food Ingredients Alter Infant Gut Microbiome Composition and Metabolism In Vitro

We examined the prebiotic potential of 32 food ingredients on the developing infant microbiome using an in vitro gastroileal digestion and colonic fermentation model. There were significant changes in the concentrations of short-chain fatty-acid metabolites, confirming the potential of the tested ingredients to stimulate bacterial metabolism. The 16S rRNA gene sequencing for a subset of the ingredients revealed significant increases in the relative abundances of the lactate- and acetate-producing Bifidobacteriaceae, Enterococcaceae, and Lactobacillaceae, and lactate- and acetate-utilizing Prevotellaceae, Lachnospiraceae, and Veillonellaceae. Selective changes in specific bacterial groups were observed. Infant whole-milk powder and an oat flour enhanced Bifidobacteriaceae and lactic acid bacteria. A New Zealand-origin spinach powder enhanced Prevotellaceae and Lachnospiraceae, while fruit and vegetable powders increased a mixed consortium of beneficial gut microbiota. All food ingredients demonstrated a consistent decrease in Clostridium perfringens, with this organism being increased in the carbohydrate-free water control. While further studies are required, this study demonstrates that the selected food ingredients can modulate the infant gut microbiome composition and metabolism in vitro. This approach provides an opportunity to design nutrient-rich complementary foods that fulfil infants’ growth needs and support the maturation of the infant gut microbiome.

The sugar composition of the fibre in selected plant foods modulates weaning infants' gut microbiome composition and fermentation metabolites in vitro

Eight plant-based foods: oat flour and pureed apple, blackcurrant, carrot, gold- and green-fleshed kiwifruit, pumpkin, sweetcorn, were pre-digested and fermented with pooled inocula of weaning infants’ faecal bacteria in an in vitro hindgut model. Inulin and water were included as controls. The pre-digested foods were analysed for digestion-resistant fibre-derived sugar composition and standardised to the same total fibre concentration prior to fermentation. The food-microbiome interactions were then characterised by measuring microbial acid and gas metabolites, microbial glycosidase activity and determining microbiome structure. At the physiologically relevant time of 10 h of fermentation, the xyloglucan-rich apple and blackcurrant favoured a propiogenic metabolic and microbiome profile with no measurable gas production. Glucose-rich, xyloglucan-poor pumpkin caused the greatest increases in lactate and acetate (indicative of high fermentability) commensurate with increased bifidobacteria. Glucose-rich, xyloglucan-poor oats and sweetcorn, and arabinogalactan-rich carrot also increased lactate and acetate, and were more stimulatory of clostridial families, which are indicative of increased microbial diversity and gut and immune health. Inulin favoured a probiotic-driven consortium, while water supported a proteolytic microbiome. This study shows that the fibre-derived sugar composition of complementary foods may shape infant gut microbiome structure and metabolic activity, at least in vitro.

The Microbiome-Gut-Brain Axis and Resilience to Developing Anxiety or Depression under Stress

Episodes of depression and anxiety commonly follow the experience of stress, however not everyone who experiences stress develops a mood disorder. Individuals who are able to experience stress without a negative emotional effect are considered stress resilient. Stress-resilience (and its counterpart stress-susceptibility) are influenced by several psychological and biological factors, including the microbiome-gut-brain axis. Emerging research shows that the gut microbiota can influence mood, and that stress is an important variable in this relationship. Stress alters the gut microbiota and plausibly this could contribute to stress-related changes in mood. Most of the reported research has been conducted using animal models and demonstrates a relationship between gut microbiome and mood. The translational evidence from human clinical studies however is rather limited. In this review we examine the microbiome-gut-brain axis research in relation to stress resilience.

Microbiota Composition of Breast Milk from Women of Different Ethnicity from the Manawatu-Wanganui Region of New Zealand

Human breastmilk components, the microbiota and immune modulatory proteins have vital roles in infant gut and immune development. In a population of breastfeeding women (n = 78) of different ethnicities (Asian, Māori and Pacific Island, New Zealand European) and their infants living in the Manawatu–Wanganui region of New Zealand, we examined the microbiota and immune modulatory proteins in the breast milk, and the fecal microbiota of mothers and infants. Breast milk and fecal samples were collected over a one-week period during the six to eight weeks postpartum. Breast milk microbiota differed between the ethnic groups. However, these differences had no influence on the infant’s gut microbiota composition. Based on the body mass index (BMI) classifications, the mother’s breast milk and fecal microbiota compositions were similar between normal, overweight and obese individuals, and their infant’s fecal microbiota composition also did not differ. The relative abundance of bacteria belonging to the Bacteroidetes phylum was higher in feces of infants born through vaginal delivery. However, the bacterial abundance of this phylum in the mother’s breast milk or feces was similar between women who delivered vaginally or by cesarean section. Several immune modulatory proteins including cytokines, growth factors, and immunoglobulin differed between the BMI and ethnicity groups. Transforming growth factor beta 1 and 2 (TGFβ1, TGFβ2) were present in higher concentrations in the milk from overweight mothers compared to those of normal weight. The TGFβ1 and soluble cluster of differentiation 14 (sCD14) concentrations were significantly higher in the breast milk from Māori and Pacific Island women compared with women from Asian and NZ European ethnicities. This study explores the relationship between ethnicity, body mass index, mode of baby delivery and the microbiota of infants and their mothers and their potential impact on infant health.

New Zealand Bitter Hops Extract Reduces Hunger During a 24 h Water Only Fast

Intermittent fasting improves metabolic and cardiac health. However, increased hunger towards the end of the fasting period may affect compliance and limit its application. Our aim was to determine the effect of anorexigenic agent co-therapy on subjective ratings of appetite during the 16–24 h period of a day-long water-only intermittent fast. Thirty adult men were recruited and required to fast for 24 h from 18:00 h to 18:00 h on the same day of the week for three subsequent weeks. Treatments of either a placebo or one of two doses (high dose; HD: 250 mg or low dose; LD: 100 mg) of a bitter hops-based appetite suppressant (Amarasate®) were given twice per day at 16 and 20 h into the fast. From 18–24 h of the 24 h fast, both the HD and LD treatment groups exhibited a statistically significant (p < 0.05) > 10% reduction in hunger. Additionally, the expected lunchtime increase in hunger that was present in the placebo group (12:00 h) was absent in both the HD and LD groups. These data suggest that appetite suppressant co-therapy may be useful in reducing hunger during intermittent fasting, and show that bitter compounds may regulate appetite independently of meal timing.

Human Milk Composition and Dietary Intakes of Breastfeeding Women of Different Ethnicity from the Manawatu-Wanganui Region of New Zealand

Human milk is nutrient rich, complex in its composition, and is key to a baby’s health through its role in nutrition, gastrointestinal tract and immune development. Seventy-eight mothers (19–42 years of age) of Asian, Māori, Pacific Island, or of European ethnicity living in Manawatu-Wanganui, New Zealand (NZ) completed the study. The women provided three breast milk samples over a one-week period (6–8 weeks postpartum), completed a three-day food diary and provided information regarding their pregnancy and lactation experiences. The breast milk samples were analyzed for protein, fat, fatty acid profile, ash, selected minerals (calcium, magnesium, selenium, zinc), and carbohydrates. Breast milk nutrient profiles showed no significant differences between the mothers of different ethnicities in their macronutrient (protein, fat, carbohydrate, and moisture) content. The breast milk of Asian mothers contained significantly higher levels of polyunsaturated fatty acids (PUFAs), omega-3 (n-3) and omega-6 (n-6) fatty acids, docosahexaenoic acid (DHA), and linoleic acids. Arachidonic acid was significantly lower in the breast milk of Māori and Pacific Island women. Dietary intakes of protein, total energy, saturated and polyunsaturated fat, calcium, phosphorus, zinc, iodine, vitamin A equivalents, and folate differed between the ethnic groups, as well as the number of serves of dairy foods, chicken, and legumes. No strong correlations between dietary nutrients and breast milk components were found.

Effect of chronic hypoxia on RAGE and its soluble forms in lungs and plasma of mice

The receptor for advanced glycation end products (RAGE) is a multi-ligand receptor. Alternative splicing and enzymatic shedding produce soluble forms that protect against damage by ligands including Advanced Glycation End products (AGEs). A link between RAGE and oxygen levels is evident from studies showing RAGE-mediated injury following hyperoxia. The effect of hypoxia on pulmonary RAGE expression and circulating sRAGE levels is however unknown. Therefore mice were exposed to chronic hypoxia for 21 d and expression of RAGE, sheddases in lungs and circulating sRAGE were determined. In addition, accumulation of AGEs in lungs and expression of the AGE detoxifying enzyme GLO1 and receptors were evaluated. In lung tissue gene expression of total RAGE, variants 1 and 3 were elevated in mice exposed to hypoxia, whereas mRAGE and sRAGE protein levels were decreased. In the hypoxic group plasma sRAGE levels were enhanced. Although the levels of pro-ADAM10 were elevated in lungs of hypoxia exposed mice, the relative amount of the active form was decreased and gelatinase activity unaffected. In the lungs, the RAGE ligand HMGB1 was decreased and of the AGEs, only LW-1 was increased by chronic hypoxia. Gene expression of AGE receptors 2 and 3 was significantly upregulated. Chronic hypoxia is associated with downregulation of pulmonary RAGE protein levels, but a relative increase in sRAGE. These alterations might be part of the adaptive and protective response mechanism to chronic hypoxia and are not associated with AGE formation except for the fluorophore LW-1 which emerges as a novel marker of tissue hypoxia.

Altered transcription of murine genes induced in the small bowel by administration of probiotic strain Lactobacillus rhamnosus HN001

Lactobacillus rhamnosus HN001 is a probiotic strain reported to increase resistance to epithelium-adherent and -invasive intestinal pathogens in experimental animals. To increase understanding of the relationship between strain HN001 and the bowel, transcription of selected genes in the mucosa of the murine small bowel was measured. Mice previously naive to lactobacilli (Lactobacillus-free mice) were examined after daily exposure to HN001 in drinking water. Comparisons were made to results from matched Lactobacillus-free mice. Infant and adult mice were investigated to provide a temporal view of gene expression in response to exposure to HN001. Genes sgk1, angptl4, and hspa1b, associated with the apoptosis pathway, were selected for investigation by reverse transcription-quantitative PCR on the basis of a preliminary duodenal DNA microarray screen. Normalized to gapdh gene transcription, these three genes were upregulated after 6 to 10 days exposure of adult mice to HN001. Angptl4 was shown by immunofluorescence to be upregulated in duodenal epithelial cells of mucosal samples. Epithelial cell migration was faster in HN001-exposed mice than in the Lactobacillus-free controls. Transcriptional responses in infant mice differed according to bowel region and age. For example, sgk1 was upregulated in duodenal, jejunal, and ileal mucosa of mice less than 25 days old, whereas angptl4 and hspa1b were upregulated at 10 days in the duodenum but downregulated in the jejunal mucosa until mice were 25 days old. Overall, the results provide links between a probiotic strain, mucosal gene expression, and host phenotype, which may be useful in delineating mechanisms of probiotic action.

Preparation, characterization and analytical application of an electrochemical laccase biosensor towards low level determination of isoprenaline in human serum samples

A novel electrochemical biosensor has been developed based on the immobilization of multiwalled carbon nanotubes (MWCNT) followed by sol–gel entrapment of laccase (Lac) enzyme on to the GCE.

Meta-analysis: underutilisation and disparities of treatment among patients with hepatocellular carcinoma in the United States

BACKGROUND

Despite wide availability of treatment options for hepatocellular carcinoma (HCC), several studies have suggested underutilisation in clinical practice.

AIMS

To quantify utilisation rates for HCC treatment among patients with HCC in the United States, and to summarise patterns of association between utilisation rates and patient socio-demographic characteristics.

METHODS

We performed a systematic literature review using the Medline database from January 1989 to March 2013. Two investigators independently extracted data on patient populations, study methods and results using standardised forms. Pooled treatment rates for any treatment and curative treatment, with 95% confidence intervals, were calculated. Prespecified subgroup analysis was performed to identify patient-level correlates of treatment utilisation.

RESULTS

We identified 24 studies that met inclusion criteria. The pooled rates of any treatment and curative treatment were 52.8% (95% CI 52.2-53.4%) and 21.8% (95% CI 21.4-22.1%) respectively. Among patients diagnosed at an early stage, the pooled curative treatment rate was 59.0% (95% CI 58.1-59.9%). Elderly, non-Caucasians and patients of low socioeconomic status had lower treatment rates than their counterparts.

CONCLUSIONS

Rates of HCC treatment in the United States, including curative treatment rates among patients detected at an early stage, are disappointingly low. Future efforts should focus on identifying appropriate intervention targets to increase treatment rates and reduce socio-demographic disparities.

Functionality of Probiotics – Potential for Product Development

It is becoming increasingly accepted by consumers that live lactic acid bacteria do exert health benefits when eaten. In addition, it is also becoming recognised that not all probiotic bacteria are equal. It is now no longer just a question of providing sufficient numbers of viable bacteria in a product; industry must also provide proof of efficacy for each strain. In the early 1990s, Fonterra embarked on a programme to develop proprietary probiotic strains, and as a result, commercialised two strains, Bifidobacterium lactis HN019 and Lactobacillus rhamnosus HN001. Over the past decade, Fonterra has developed a significant body of peerreviewed published reports around these strains, including studies showing safety in animal and human trials, protection against pathogens such as Salmonella typhimurium and Escherichia coli O157:H7, modulation of human and animal immune markers at realistic dose rates, and efficacy in human clinical trials. Based on this work, HN019 and HN001 have been applied to several functional foods both by Fonterra (under the DR10 and DR20 brands, respectively) and by third parties (e.g. under the HOWARU brand by Danisco). While the 'gold standard' of proof of efficacy is a phase III clinical trial, ethical considerations as well as expense preclude the use of clinical trials as screening tools for probiotics. Therefore, biomarkers have to be employed to identify strains with probiotic utility, and to define the different positive health benefits of existing probiotic strains. However, as the mechanisms by which most probiotic bacteria exert their health benefits remain unclear, the question of which biomarkers accurately reflect efficacy in vivo remains unresolved. With recent technological advances, and the shift toward probiotics targeted to specific conditions, researchers are beginning to tease out how probiotic bacteria work, and it is this knowledge that will inform biomarker development and improve the ability to offer the market safe and effective probiotic functional foods.

Differential roles of C4 and betaC1 in mediating suppression of post-transcriptional gene silencing: evidence for transactivation by the C2 of Bhendi yellow vein mosaic virus, a monopartite begomovirus

Bhendi yellow vein mosaic disease (BYVMD) is caused by the association of a DNA beta satellite with a begomovirus component. The begomovirus component has two promoters, one in the virion sense (V-sense) and the other in the complementary sense (C-sense) in the intergenic region (IR). To study the promoter activities of V-sense and C-sense promoters, mGFP gene fusion was made downstream to the promoters. Transient and stable expressions in N. benthamiana leaves showed significant GFP expression under C-sense promoter whereas the expression under the V-sense promoter was very weak in the absence of the transactivator C2. Untransformed N. benthamiana plants were agroinfiltrated with binary vector constructs containing V-sense-GFP alone or along with C1, C2, C4, V1, V2 or betaC1 (in both sense and antisense orientations) to understand the roles of these gene products in transactivation and/or suppression of post-transcriptional gene silencing (PTGS). The results showed strong suppression of gene silencing activities for C4 and betaC1 but a weak activity for C2. The suppression activities were also confirmed using gfp-silenced GFP16c/GFPi plants by agroinfiltration and agroinoculation. The expression of C4 and betaC1 as transgenes produced abnormal phenotypic growth compared to the other viral genes mentioned above, further supporting their suppressor function.

Impact of consumption of different levels of Bifidobacterium lactis HN019 on the intestinal microflora of elderly human subjects

BACKGROUND

Age-related changes in the physiology and intestinal function of the elderly render them more susceptible to gut-related illnesses. Probiotic dietary supplementation has been shown to enhance the health indices in the elderly.

OBJECTIVE

To determine the effect of three different doses [5 x 109 CFU/day (high), 1.0 x 109 CFU/day (medium) and 6.5 x 107 CFU/day (low)] of Bifidobacterium lactis HN019 (DR10TM) on the intestinal flora of elderly human subjects and the dose response effect.

DESIGN

Randomised, double-blind and placebo-controlled human dietary intervention study consisting of four groups of 20 elderly (over 60 years old) volunteers. Each volunteer consumed 250 mL per day of reconstituted skim milk (RSM) which either did not contain any probiotic supplement (placebo group) or contained B. lactis HN019 at different levels (low, medium and high dose groups). The study comprised three stages: a 2-week pre-intervention (without any supplement), followed by 4 weeks of test feeding (dietary intervention) and then a 2-week washout period.

RESULTS

After dietary intervention, statistically significant increases in bifidobacteria, lactobacilli and enterococci were observed. At the end of the 4-week feeding period the mean number of bifidobacteria recorded in the placebo group were 9.31 +/- 0.01 log CFU/g of faeces. In the high, medium and low dose groups the bifidobacteria levels were significantly (p < 0.006) higher (9.88 +/- 0.1, 9.75 +/- 0.14 and 9.74 +/- 0.11 log CFU/g of faeces, respectively), when compared to the respective pre-intervention levels. There were no significant differences (p superior 0.05) between the responses of the different dose groups, indicating that even the lowest dose tested augmented the changes in bifidobacteria. Similar trends were observed for lactobacilli and enterococci. In contrast, the counts of enterobacteria were reduced in all the probiotic dose groups.

CONCLUSION

The present study showed that dietary supplementation with B. lactis HN019 significantly increased the number of resident bifidobacteria and reduced the enterobacteria counts. In addition, enterococci and lactobacilli were also increased. Based on this study and already published clinical evidence (4, 5, 8, 9) we conclude that, B. lactis HN019 is a suitable probiotic for elderly human subjects and even the lowest dose (6.5 x 107 CFU/day) tested is able to confer desired changes in the intestinal microflora.

Probiotic research in Australia, New Zealand and the Asia-Pacific region

Although the epicentres of probiotic research in the past decade have been Japan and Europe, researchers in the Asia-Pacific region have actively contributed to the growing understanding of the intestinal microbial ecosystem, and interactions between gut bacteria, diet and health of the human host. A number of new probiotic strains have been developed in the region that have been demonstrated to have beneficial impacts on health in animal and human trials, including improved protection against intestinal pathogens and modulation of the immune system. Probiotics targeted to animals, including aquaculture, feature heavily in many Asian countries. Developments in probiotic technologies have included microencapsulation techniques, antimicrobial production in fermented meats, and synbiotic combinations. In particular, the impact of resistant starch on the intestinal environment and fermentation by intestinal bacteria has been intensively studied and new probiotic strains selected specifically for synbiotic combinations with resistant starch. This paper provides an overview of probiotic research within Australia, New Zealand and a number of Asian countries, and lists scientists in the Asia-Pacific region involved in various aspects of probiotic research and development.

Impact of consumption of oligosaccharide-containing biscuits on the fecal microbiota of humans

Human subjects consumed biscuits containing either galacto-oligosaccharides or fructo-oligosaccharides in a double-blinded, crossover study. The impact of supplementing the diet with three biscuits per day on the fecal microbiota was evaluated by selective culture of particular bacterial groups, measurement of beta-galactosidase activity, and nucleic acid-based analytical methods (PCR-denaturing gradient gel electrophoresis [PCR-DGGE] and fluorescent in situ hybridization). The composition of the bifidobacterial populations was monitored at the level of species (PCR-DGGE) and strains (pulsed-field gel electrophoresis of DNA digests), and representative cultures were tested quantitatively for their ability to use galacto-oligosaccharides. Technical improvements to DGGE analysis of the microbiota were made by the use of an internal standard that allowed valid comparisons of fragment staining intensities to be made between profiles, the use of S1 nuclease digestion to remove single-stranded DNA to facilitate cloning of DNA sequences cut from gels, and the extraction of RNA to be used as the template in reverse transcription-PCR-DGGE. RNA-DGGE profiles were markedly different (Dice's similarity coefficient, 58.5%) from those generated by DNA-DGGE. Neither the sizes of the bacterial populations nor the DNA-DGGE profiles of the microbiota were altered by the consumption of the biscuits, but the RNA-DGGE profiles were altered by the detection or increased staining intensity of 16S rRNA gene sequences originating from Bifidobacterium adolescentis and/or Colinsella aerofaciens in the feces of 11 of 15 subjects. beta-Galactosidase activity was elevated in the feces of some subjects as a result of biscuit consumption. Subjects differed in the ability of the bifidobacterial strains harbored in their feces to use galacto-oligosaccharides. Our observations suggest that a phylogenetic approach to analysis of the gut ecosystem may not always be optimal and that a more physiological (biochemical) method might be more informative.

Heat and osmotic stress responses of probiotic Lactobacillus rhamnosus HN001 (DR20) in relation to viability after drying

The viability of lactic acid bacteria in frozen, freeze-dried, and air-dried forms is of significant commercial interest to both the dairy and food industries. In this study we observed that when prestressed with either heat (50 degrees C) or salt (0.6 M NaCl), Lactobacillus rhamnosus HN001 (also known as DR20) showed significant (P < 0.05) improvement in viability compared with the nonstressed control culture after storage at 30 degrees C in the dried form. To investigate the mechanisms underlying this stress-related viability improvement in L. rhamnosus HN001, we analyzed protein synthesis in cultures subjected to different growth stages and stress conditions, using two-dimensional gel electrophoresis and N-terminal sequencing. Several proteins were up- or down-regulated after either heat or osmotic shock treatments. Eleven proteins were positively identified, including the classical heat shock proteins GroEL and DnaK and the glycolytic enzymes glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, enolase, phosphoglycerate kinase, and triose phosphate isomerase, as well as tagatose 1,6-diphosphate aldolase of the tagatose pathway. The phosphocarrier protein HPr (histidine-containing proteins) was up-regulated in cultures after the log phase irrespective of the stress treatments used. The relative synthesis of an ABC transport-related protein was also up-regulated after shock treatments. Carbohydrate analysis of cytoplasmic contents showed higher levels (20 +/- 3 microg/mg of protein) in cell extracts (CFEs) derived from osmotically stressed cells than in the unstressed control (15 +/- 3 microg/mg of protein). Liquid chromatography of these crude carbohydrate extracts showed significantly different profiles. Electrospray mass spectrometry analysis of CFEs revealed, in addition to normal mono-, di-, tri-, and tetrasaccharides, the presence of saccharides modified with glycerol.

A mutation that prevents glucosylation of the lipid-linked oligosaccharide precursor leads to underglycosylation of secreted yeast invertase

A mutant of Saccharomyces cerevisiae with the genotype mnn1 mnn2 mnn9 gls1 synthesizes mannoproteins with oligosaccharides having the composition Glc3Man10Glc-NAc2- owing to the mnn9 defect, which prevents synthesis of the outer chain, the mnn1 defect, which prevents branching of the core, and the gls1 mutation, which prevents deglucosylation of the resultant glycoprotein as a consequence of a defective glucosidase-I [Tsai, P.-K., Ballou, L., Esmon, B., Schekman, R. & Ballou, C. E. (1984) Proc. Natl. Acad. Sci. USA 81, 6340-6343]. (The mnn2 defect is not expressed in presence of the mnn9 mutation.) This strain spontaneously forms new colonies in which gls1 is suppressed owing to a defect in synthesis of dolichol phosphoglucose, the glucosylation substrate. The new mutant, designated mnn1 mnn2 mnn9 gls1 dpg1, synthesizes and secretes invertase (EC 3.2.1.26) that has a higher mobility on native gel electrophoresis than that made by the parent strain, the consequence of a reduction in both the size and the number of carbohydrate chains. The mannoprotein chains have the mnn1 mnn9 structure (Man10Glc-NAc2-), and the invertase is resolved by gel electrophoresis in sodium dodecyl sulfate into two major and two minor bands that represent homologs with about 4-7 carbohydrate units, in contrast to about 8-11 chains in the parent strain. Thus, the inability to glucosylate the lipid-linked precursor reduces the efficiency of glycosylation of the protein chains. The genetic defect is in synthesis of the glucose donor dolichol phosphoglucose, but the mutation is nonallelic with the reported alg5-1 mutation, which has a similar phenotype [Runge, K. W., Huffaker, T. C. & Robbins, P. W. (1984) J. Biol. Chem. 259, 412-417].

Isolation and structure of glucan from regenerating spheroplasts of Candida albicans

Regenerating spheroplasts of Candida albicans formed organized glucan nets in liquid culture. The nets consisted of interwoven microfibrils about 50 nm wide, but of an undetermined length. Partial acid hydrolysis of the polysaccharide showed the presence of chains of beta(1----3)- and beta(1----6)-linked glucose residues, but no intrachain beta(1----3) and beta(1----6) linkages. Periodate oxidation and GLC of the methylated glucan indicated a highly branched polymer (9.5% branch points). Sequential enzymic degradation of the isolated nets confirmed the presence of chains of beta(1----3)- and beta(1----6)-linked glucose residues. Degradation by (1----3)-beta- and (1----6)-beta-glucanase released 23% (w/w) and 30% (w/w) respectively of the carbohydrate as glucose equivalents. The residual material was degraded by chitinase. Equal amounts of N-acetylglucosamine and glucose equivalents were detected in the chitinase hydrolysate, suggesting a possible linkage between glucan and chitin. Our data indicate that the cell wall of C. albicans contains at least two highly branched glucans with predominantly beta(1----3) or beta(1----6) linkages.

Metabolism of [14C]glucose by regenerating spheroplasts of Candida albicans

Spheroplasts of Candida albicans were regenerated in [14C]glucose and buffered magnesium sulphate (0.1 M-Tris/HCl; 0.5 M-MgSO4, pH 7.2) at 35 degrees C. Uptake of glucose by spheroplasts was faster than that by intact yeast cells. After 6 h, 65% of the glucose taken up by the yeast appeared as CO2 and 30% was incorporated into the cellular material. With spheroplasts, 55% of the glucose taken up was expired as CO2, 25% was excreted into the medium as other metabolites and 20% was incorporated into the cells. The regenerating spheroplasts excreted 14C-labelled carbohydrates into the medium which were fractionated on a Sephadex G-15 column. Acid hydrolysis of the low molecular-weight fraction yielded the following sugars: mannose (75.7%), fucose (3.8%), arabinose (3%), galactose (2.1%) and an unidentified monosaccharide (14%). Spheroplasts did not incorporate mannoprotein into the regenerated wall. The wall carbohydrate from regenerated spheroplasts was fractionated on the basis of solubility in sodium hydroxide. The alkali-insoluble fraction was analysed by sequential enzyme hydrolysis; 40% of the incorporated counts were associated with beta (1----3)-linked glucan and 50% with a mixed glucan comprising beta (1----3)- and beta (1----6)-linkages and chitin.

Enzymes of N-acetylglucosamine metabolism during germ-tube formation in Candida albicans

The enzymes of N-acetyl-D-glucosamine (GlcNAc) metabolism, GlcNAc-6-phosphate deacetylase and GlcN-6-phosphate deaminase were found to be inducible in Candida albicans. The pattern of induction for these enzymes was the same under conditions of germ-tube formation (37 degrees C) and where yeast cells metabolized GlcNAc with no change in morphology (28 degrees C); this indicates that these enzymes are not control points in the dimorphic development of C. albicans. During induction there was a 40-and 25-fold increase in specific activity for the deacetylase and the deaminase, respectively, and the maximum specific activity correspond to the time when all the GlcNAc had been metabolized. The presence of lomofungin (an inhibitor of transcription) or trichodermin (an inhibitor of translation) in cell suspensions of C. albicans containing GlcNAc prevented the increase in specific activity of these enzymes. 2-Deoxyglucose inhibited germ-tube formation, partially inhibited the induction of the deacetylase (43%) and the deaminase (60%), but did not affect the growth of C. albicans on either Glc or GlcNAc. GlcN-6-phosphate was a competitive inhibitor of the deacetylase with a Ki of 1.4 mM while the other product of the reaction, acetate, did not inhibit the enzyme. The Km value for GlcN-6-phosphate on GlcN-6-phosphate deaminase was 0.24 mM. Incubation of starved yeast cells with GlcNAc produced a four-fold increase in the specific activity of UDP-GlcNAc-pyrophosphorylase at either 28 degrees C or 37 degrees C.