Non-peptidyl small molecule, adenosine, 5'-Se-methyl-5'-seleno-, 2',3'-diacetate, activates insulin receptor and attenuates hyperglycemia in type 2 diabetic Leprdb/db mice.

The pathophysiology of type 2 diabetes mellitus (T2D) is characterized by reduced or absent insulin receptor (INSR) responsiveness to its ligand, elevated hepatic glucose output and impaired glucose uptake in peripheral tissues, particularly skeletal muscle. Treatments to reduce hyperglycemia and reestablish normal insulin signaling are much sought after. Any agent which could be orally administered to restore INSR function, in an insulin-independent manner, would have major implications for the management of this global disease. We have discovered a non-peptidyl small molecule, adenosine, 5'-Se-methyl-5'-seleno-, 2',3'-diacetate [referred to as non-peptidyl compound #43 (NPC43)], which restores INSR signaling in the complete absence of insulin. Initial screening of numerous compounds in human HepG2 liver cells revealed that NPC43 significantly inhibited glucose production. The compound was potently anti-hyperglycemic and anti-hyperinsulinemic in vivo, in insulin-resistant T2D Leprdb/db mice, following either acute or chronic treatment by oral gavage and intraperitoneal injection, respectively. The compound acted at the level of INSR and activated it in both liver and skeletal muscle of Leprdb/db mice. In cell culture, the compound activated INSR in both liver and skeletal muscle cells; furthermore, it cooperated with insulin to depress glucose-6-phosphatase catalytic subunit (G6pc) expression and stimulate glucose uptake, respectively. Our results indicated that the compound directly interacted with INSRα, triggering appropriate phosphorylation and activation of the receptor and its downstream targets. Unlike insulin, NPC43 did not activate insulin-like growth factor 1 receptor in either liver or skeletal muscle. We believe this compound represents a potential oral and/or injectable insulin replacement therapy for diabetes and diseases associated with insulin resistance.

Biological activity of selenium: Revisited.

Selenium (Se) is an essential micronutrient that exerts multiple and complex effects on human health. Se is essential for human well-being largely due to its potent antioxidant, anti-inflammatory, and antiviral properties. The physiological functions of Se are carried out by selenoproteins, in which Se is specifically incorporated as the amino acid, selenocysteine. Importantly, both beneficial and toxic effects of Se have been reported suggesting that the mode of action of Se is strictly chemical form and concentration dependent. Additionally, there is a relatively narrow window between Se deficiency and toxicity and growing evidence suggests that Se health effects depend greatly on the baseline level of this micronutrient. Thus, Se supplementation is not an easy task and requires an individualized approach. It is essential that we continue to explore and better characterize Se containing compounds and mechanisms of action, which could be crucial for disease prevention and treatment.

Supplementation with selenium-enriched yeast attenuates brain metastatic growth.

Metastases are the leading cause of cancer mortality and their development may be affected by diet. The aim of this study was to compare the effects of dietary supplementation with different selenium (Se) compounds on the dynamics of brain metastasis development in a novel mouse model. Mice were fed experimental diets enriched (1 mg/kg) with sodium selenite (Se-S), seleno-1-methionine (Se-Meth), a yeast-derived organic form of selenium (Se-Yeast), or a control diet (Se < 0.05 mg/kg) for 20 wk. At the end of the feeding period, animals were injected with luciferase-tagged K1735 (K1735-Luc) melanoma cells into the brain vasculature. The development of brain metastatic tumors was monitored for 2 wk following injection. Mice bearing brain metastatic tumors and fed Se-Yeast- or Se-S-enriched diets displayed a higher survival rate compared with other experimental and control groups. Importantly, Se-Yeast supplementation decreased the growth of brain metastatic tumors as determined by the measurement of the intensity of the bioluminescent signal emitted by K1735-Luc cells upon reaction with luciferin. Different chemical forms of Se have distinct effects on the development of brain metastases. Organic Se in the form of Se-Yeast may be a valuable agent in suppression of brain metastatic disease.

Oral administration of NPC43 counters hyperglycemia and activates insulin receptor in streptozotocin-induced type 1 diabetic mice.

INTRODUCTION: Adenosine, 5'-Se-methyl-5'-seleno-,2',3'-diacetate (NPC43) is a recently identified small, non-peptidyl molecule which restores normal insulin signaling in a mouse model of type 2 diabetes (Lan et al). The present study investigated the ability of NPC43 as an oral and injectable insulin-replacing agent to activate insulin receptor (INSR) and counter hyperglycemia in streptozotocin (STZ)-induced type 1 diabetic (T1D) mice. RESEARCH DESIGN AND METHODS: In this study, STZ was intraperitoneally injected into wild-type mice to induce hyperglycemia and hypoinsulinemia, the main features of T1D. These STZ-induced T1D mice were given NPC43 orally or intraperitoneally and blood glucose levels were measured using a glucometer. Protein levels of phosphorylated and total Insrß, protein kinase B (Akt) and AS160 (critical for glucose uptake) in the skeletal muscle and liver of STZ-induced T1D mice following oral NPC43 treatment were determined by western blot analysis. In addition, hepatic expression of activated Insr in STZ-induced T1D mice after intraperitoneal NPC43 treatment was measured by ELISA. Student's t-test was used for statistical analysis. RESULTS: Oral administration of NPC43 at a dose of 5.4 or 10.8 mg/kg body weight (mpk) effectively lowered blood glucose levels in STZ-induced T1D mice at ≥1 hour post-treatment and the glucose-lowering activity of oral NPC43 persisted for 5 hours. Blood glucose levels were also reduced in STZ-induced T1D mice following intraperitoneal NPC43 (5.4 mpk) treatment. Protein levels of phosphorylated Insrß, Akt and AS160 were significantly increased in the skeletal muscle and liver of STZ-induced T1D mice after oral NPC43 (5.4 mpk) treatment. In addition, activation of hepatic Insr was observed in STZ-induced T1D mice following intraperitoneal NPC43 (5.4 mpk) treatment. CONCLUSIONS: We conclude that NPC43 is a de facto fast-acting oral and injectable insulin mimetic which activates Insr and mitigates hyperglycemia in a mouse model of T1D.

Characterisation of prototype Nurmi cultures using culture-based microbiological techniques and PCR-DGGE.

Undefined Nurmi-type cultures (NTCs) have been used successfully to prevent salmonella colonisation in poultry for decades. Such cultures are derived from the caecal contents of specific-pathogen-free birds and are administered via drinking water or spray application onto eggs in the hatchery. These cultures consist of many non-culturable and obligately anaerobic bacteria. Due to their undefined nature it is difficult to obtain approval from regulatory agencies to use these preparations as direct fed microbials for poultry. In this study, 10 batches of prototype NTCs were produced using an identical protocol over a period of 2 years. Traditional microbiological techniques and a molecular culture-independent methodology, polymerase chain reaction combined with denaturing gradient gel electrophoresis (PCR-DGGE), were applied to characterise these cultures and also to examine if the constituents of the NTCs were identical. Culture-dependent analysis of these cultures included plating on a variety of selective and semi-selective agars, examination of colony morphology, Gram-staining and a series of biochemical tests (API, BioMerieux, France). Two sets of PCR-DGGE studies were performed. These involved the amplification of universal and subsequently lactic acid bacteria (LAB)-specific hypervariable regions of a 16S rRNA gene by PCR. Resultant amplicons were subjected to DGGE. Sequence analysis was performed on subsequent bands present in resultant DGGE profiles using the Basic Local Alignment Search Tool (BLAST). Microbiological culturing techniques tended to isolate common probiotic bacterial species from the genera Lactobacillus, Lactococcus, Bifidobacterium, Enterococcus, Clostridium, Escherichia, Pediococcus and Enterobacterium as well as members of the genera, Actinomyces, Bacteroides, Propionibacterium, Capnocytophaga, Proteus, and Klebsiella. Bacteroides, Enterococcus, Escherichia, Brevibacterium, Klebsiella, Lactobacillus, Clostridium, Bacillus, Eubacterium, Serratia, Citrobacter, Enterobacter, Pectobacterium and Pantoea spp. in addition to unculturable bacteria were identified as constituents of the NTCs using universal PCR-DGGE analysis. A number of the sequences detected by LAB-specific PCR-DGGE were homologous to those of a number of Lactobacillus spp., including L. fermentum, L. pontis, L. crispatus, L. salivarius, L. casei, L. suntoryeus, L. vaginalis, L. gasseri, L. aviaries, L. johnsonii, L. acidophilus, and L. mucosae in addition to a range of unculturable lactobacilli. While NTCs are successful due to their complexity, the presence of members of Lactobacillus spp. amongst other probiotic genera, in these samples possibly lends to the success of the NTC cultures as probiotics or competitive exclusion products in poultry over the decades. PCR-DGGE proved to be an effective tool in detecting non-culturable organisms present in these complex undefined cultures. In conclusion, while the culture-dependent identification methods or PCR-DGGE alone cannot comprehensively elucidate the bacterial species present in such complex cultures, their complementarity provides useful information on the identity of the constituents of NTCs and will aid in future development of defined probiotics. Moreover, for the purpose of analysing prototype NTCs during their development, PCR-DGGE overcomes the limitations associated with conventional culturing methods including their low sensitivities, inability to detect unculturable bacteria and unknown species, very slow turnabout time and poor reproducibility. This study demonstrated that PCR-DGGE is indeed more valuable in detecting predominant microbial populations between various NTCs than as an identification methodology, being more applicable as a quality control method used to analyse for batch-to-batch variation during NTC production.

Purification and physico-chemical characterisation of genetically modified phytases expressed in Aspergillus awamori.

Two heterologous phytases from Aspergillus awamori and Aspergillus fumigatus obtained from submerged cultures of genetically modified fungal strains in addition to two commercially available phytase preparations (Allzyme and Natuphos phytases) were purified to homogeneity using a combination of ultrafiltration, gel filtration and ion exchange. The purified preparations were used in subsequent characterisation studies, in which Western Immunoblot analysis, pH and temperature optima, thermal stability and substrate specificity were assessed. A. fumigatus phyA phytase expressed in A. awamori exhibited activity over a broad pH range together with an increased temperature optimum, and slightly enhanced thermal stability compared to the other phytases tested, and is thus a promising candidate for animal feed applications. This particular phytase retains activity over a wide range of pH values characteristic of the digestive tract and could conceivably be more suited to the increasingly higher feed processing temperatures being utilised today, than the corresponding phytases from Aspergillus niger.

Dietary Selenium Supplementation Modulates Growth of Brain Metastatic Tumors and Changes the Expression of Adhesion Molecules in Brain Microvessels.

Various dietary agents can modulate tumor invasiveness. The current study explored whether selenoglycoproteins (SeGPs) extracted from selenium-enriched yeast affect tumor cell homing and growth in the brain. Mice were fed diets enriched with specific SeGPs (SeGP40 or SeGP65, 1 mg/kg Se each), glycoproteins (GP40 or GP65, 0.2-0.3 mg/kg Se each) or a control diet (0.2-0.3 mg/kg Se) for 12 weeks. Then, murine Lewis lung carcinoma cells were infused into the brain circulation. Analyses were performed at early (48 h) and late stages (3 weeks) post tumor cell infusion. Imaging of tumor progression in the brain revealed that mice fed SeGP65-enriched diet displayed diminished metastatic tumor growth, fewer extravasating tumor cells and smaller metastatic lesions. While administration of tumor cells resulted in a significant upregulation of adhesion molecules in the early stage of tumor progression, overexpression of VCAM-1 (vascular call adhesion molecule-1) and ALCAM (activated leukocyte cell adhesion molecule) messenger RNA (mRNA) was diminished in SeGP65 supplemented mice. Additionally, mice fed SeGP65 showed decreased expression of acetylated NF-κB p65, 48 h post tumor cell infusion. The results indicate that tumor progression in the brain can be modulated by specific SeGPs. Selenium-containing compounds were more effective than their glycoprotein controls, implicating selenium as a potential negative regulator of metastatic process.

Dietary Supplementation with Organoselenium Accelerates Recovery of Bladder Expression, but Does Not Improve Locomotor Function, following Spinal Cord Injury.

Selenium is an essential element required for activity of several antioxidant enzymes, including glutathione peroxidase. Because of the critical role of the antioxidant system in responding to traumatic events, we hypothesized that dietary selenium supplementation would enhance neuroprotection in a rodent model of spinal cord injury. Rats were maintained on either a control or selenium-enriched diet prior to, and following, injury. Dietary selenium supplementation, provided as selenized yeast added to normal rat chow, resulted in a doubling of selenium levels in the spinal cord. Dietary selenium reduced the time required for recovery of bladder function following thoracic spinal cord injury. However, this was not accompanied by improvement in locomotor function or tissue sparing.

Development of solution phase hybridisation PCR-ELISA for the detection and quantification of Enterococcus faecalis and Pediococcus pentosaceus in Nurmi-type cultures.

Nurmi-type cultures (NTCs), derived from the fermentation of caecal contents of specifically pathogen-free (SPF) birds, have been used successfully to control salmonella colonisation in chicks. These cultures are undefined in nature and, consequently, it is difficult to obtain approval from regulatory agencies for their use as direct fed microbials (DFMs) for poultry. Progress towards the generation of effective defined probiotics requires further knowledge of the composition of these cultures. As such, species-specific, culture-independent quantification methodologies need to be developed to elucidate the concentration of specific bacterial constituents of NTCs. Quantification of specific bacterial species in such ill-defined complex cultures using conventional culturing methods is inaccurate due to low levels of sensitivity and reproducibility, in addition to slow turnaround times. Furthermore, these methods lack selectivity due to the nature of the accompanying microflora. This study describes the development of a rapid, sensitive, reliable, reproducible, and species-specific culture-independent, solution phase hybridisation PCR-ELISA procedure for the detection and quantification of Enterococcus faecalis and Pediococcus pentosaceus in NTCs. In this technique, biotin-labelled primers were designed to amplify a species-specific fragment of a marker gene of known copy number, in both species. Resulting amplicons were hybridised with a dinitrophenol (DNP)-labelled oligonucleotide probe in solution and were subsequently captured on a streptavidin-coated microtitre plate. The degree of binding was determined by the addition of IgG (anti-DNP)-horseradish peroxidase conjugate, which was subsequently visualised using a chromogenic substrate, tetramethylbenzidine. This novel quantitative method was capable of detecting E. faecalis and P. pentosaceus at levels as low as 5 CFU per PCR reaction.

Assessment of the effects of Nurmi-type cultures and a defined probiotic preparation on a Salmonella typhimurium 29E challenge in vivo.

The effects of treatment with an undefined commercial Nurmi-type culture (NTC), cultured cecal contents, and a dual-strain probiotic, containing Enterococcus faecalis and Pediococcus pentosaceus, on Salmonella Typhimurium colonization were evaluated in a specific-pathogen-free bird model. Two sets of trials were performed, and each study was arranged as a randomized complete block design with three treatments. Treatments consisted of (i) control, (ii) commercial NTC, and (iii) cultured cecal contents in the first set of trials and (i) control, (ii) defined probiotic, and (iii) cultured cecal contents in the second set. On day 1, birds were administered 1.2 x 10(7) CFU of the appropriate treatment by oral gavage. On day 3, all birds were challenged with 1 x 10(6) CFU of Salmonella Typhimurium 29E (nalidixic acid resistant). Chicks were asphyxiated with argon gas on day 10, and ceca were aseptically removed. Salmonella Typhimurium counts (CFU per milliliter of cecal contents) were determined on brilliant green agar containing 30 mg of nalidixic acid per liter, and CFU counts were log transformed prior to analysis. Cecal pH and volatile fatty acid concentrations were also determined. Data were analyzed by one-way analysis of variance, and means were compared by Tukey's pairwise analysis. Commercial NTC and cultured cecal contents treatments resulted in a significant decrease (P < or = 0.05) in Salmonella Typhimurium 29E colonization, with the NTC offering a higher level of protection. In the second set of trials, the defined probiotic tended to reduce colonization by Salmonella Typhimurium (P = 0.07), while chicks treated with cultured cecal contents displayed a significant decrease (P = 0.03) when compared to the negative control. No significant change was observed in cecal pH or in acetate and propionate concentrations; however, a significant increase in butyrate concentrations in both the cultured cecal contents and defined probiotic treatment groups was observed when compared to the control birds. These observations suggest that defined cultures are less effective Salmonella control agents than are preparations generated from the complete cecal microflora.

Selenoglycoproteins attenuate adhesion of tumor cells to the brain microvascular endothelium via a process involving NF-κB activation.

Selenium-containing compounds and selenized yeast have anticancer properties. In order to address possible mechanisms involved in these effects, selenoglycoproteins (SGPs) were extracted from selenium-enriched yeast at pH 4.0 and 6.5 (the fractions are called SGP40 and SGP65, respectively), followed by evaluation of their impact on the interactions of lung and breast tumor cells with human brain microvascular endothelial cells (HBMECs). Extracted SGPs, especially SGP40, significantly inhibited adhesion of tumor cells to HBMECs and their transendothelial migration. Because the active components of SGPs are unknown, small selenium-containing compounds [leucyl-valyl-selenomethionyl-arginine (LVSe-MR) and methylselenoadenosine (M-Se-A)], which are normally present in selenized yeast, were introduced as additional treatment groups. Treatment of HBMECs with SGP40, LVSe-MR and M-Se-A induced changes in gene signatures, which suggested a central involvement of nuclear factor (NF)-κB-dependent pathway. These observations were confirmed in the subsequent analysis of NF-κB DNA binding activity, quantitative measurements of the expression of selected genes and proteins, and tumor cell adhesion assay with a specific NF-κB inhibitor as the additional treatment factor. These findings indicate that specific organic selenium-containing compounds have the ability to inhibit tumor cell adhesion to brain endothelial cells via down-regulation of NF-κB. SGPs appear to be more effective than small selenium-containing compounds, suggesting the role of not only selenium but also the glycoprotein component in the observed protective impact.

Validation of method for total selenium determination in yeast by flame atomic absorption spectrometry.

A procedure using open digestion followed by flame atomic absorption spectrometry is described for measuring the total selenium content of Se-enriched yeast. The limits of detection and quantitation were 2.5 mg/L and 5 mg/L Se, respectively. The signal response was linear over the range of 5-50 mg/L Se, and the average recovery from spiked samples was 98.9%. The validated method was used to measure the Se content of Se-enriched yeast reference material and produced a result of 2145 +/- 38 mg/kg (n = 3), which is in good agreement with the certified level of 2125 +/- 65 mg/kg.

Source of selenium supplementation influences testis selenium content and gene expression profiles in Single Comb White Leghorn roosters.

Spermatogenesis is a tightly regulated, selenium-dependent process. Nutritional deficiencies, including Se, have been associated with decreased fertility. During Se depletion, testes preferentially retain Se while other tissues are depleted. This study was aimed at evaluating the effect of Se source (inorganic or organic yeast derived) on testes weight, Se content, and gene expression. At 17 weeks of age, roosters were randomly assigned to one of three treatments: basal diet (control), basal diet + 0.3 mg organic Se/kg organic yeast-derived Se (YS; Sel-Plex®, Alltech Inc.), or basal diet + 0.3 mg inorganic Se /kg inorganic Se as sodium selenite (SS). At 40 weeks of age, seven roosters from each treatment were euthanized and testes removed. Testes weight did not differ between treatments, but Se content was greater (P ≤ 0.01) in YS than SS and control. Testicular differential gene expression profiling was accomplished using the Affymetrix Genechip® chicken genome array. Ingenuity® pathway analysis revealed that Se supplementation, regardless of source, results in the up-regulation of genes governing cell structure/morphology. The enrichment of such pathways was greater with YS than SS. These expression patterns suggest that aside from playing a role in antioxidant defense, Se, especially in the organic YS form, is useful for maintaining testicular cell structure.

Gene expression profiling reveals differential effects of sodium selenite, selenomethionine, and yeast-derived selenium in the mouse.

The essential trace mineral selenium is an important determinant of oxidative stress susceptibility, with several studies showing an inverse relationship between selenium intake and cancer. Because different chemical forms of selenium have been reported to have varying bioactivity, there is a need for nutrigenomic studies that can comprehensively assess whether there are divergent effects at the molecular level. We examined the gene expression profiles associated with selenomethionine (SM), sodium selenite (SS), and yeast-derived selenium (YS) in the intestine, gastrocnemius, cerebral cortex, and liver of mice. Weanling mice were fed either a selenium-deficient (SD) diet (<0.01 mg/kg diet) or a diet supplemented with one of three selenium sources (1 mg/kg diet, as either SM, SS or YS) for 100 days. All forms of selenium were equally effective in activating standard measures of selenium status, including tissue selenium levels, expression of genes encoding selenoproteins (Gpx1 and Txnrd2), and increasing GPX1 enzyme activity. However, gene expression profiling revealed that SS and YS were similar (and distinct from SM) in both the expression pattern of individual genes and gene functional categories. Furthermore, only YS significantly reduced the expression of Gadd45b in all four tissues and also reduced GADD45B protein levels in liver. Taken together, these results show that gene expression profiling is a powerful technique capable of elucidating differences in the bioactivity of different forms of selenium.

Use of stringent selection parameters for the identification of possible selenium-responsive marker genes in mouse liver and gastrocnemius.

Selenium is a trace element that, although toxic in higher concentrations, is essential for human and animal health. In this study, we looked at microarray-based gene expression patterns from liver and gastrocnemius tissues in mice fed either a selenium-deficient diet or diets containing sodium selenite, selenomethionine, or a yeast-derived selenium supplement. A p value cutoff of 0.01 was used to identify a select set of selenium-responsive genes that were consistently differentially expressed across three age groups of mice with both ANOVA and t test analyses. A total of 19 gene transcripts were found to be differentially expressed across the three age groups with at least one selenium-deficient/selenium-supplemented diet comparison. Of those 19 genes, 12 had been previously identified as selenoprotein-encoding genes, and four of the genes, Gpx1, Selh, Sep15, and Sepw1, were differentially expressed in both tissues, all three mouse age groups, and all three diet comparisons. Activities associated with non-selenoproteins encoded by selenium-responsive genes included transport and stress response. The selenophosphate synthetase 2 gene Sephs2 in gastrocnemius tissue and the solute carrier gene Slc48a1 in liver tissue, both up-regulated with selenium-deficient diets compared to all three selenium-supplemented diets, are previously overlooked candidates for dietary selenium marker genes.

Insight in the transport behavior of copper glycinate complexes through the porcine gastrointestinal membrane using an Ussing chamber assisted by mass spectrometry analysis.

An Ussing chamber study was conducted in order to investigate the transport behavior of copper glycinate complexes through a porcine gastrointestinal membrane. Organic copper complexes such as copper tri- and tetraglycinates (GGG-Cu(II) and GGGG-Cu(II)) were used as model system. In a novel analytical approach the Ussing chamber was combined with mass spectrometry. Therefore, relevant analytical methods based on MALDI-MS and a coupling of capillary electrophoresis to ICP-MS and ESI-MS were developed for the determination of copper complexes in the mucosal and serosal half-chambers. It was found that 86.1+/-8.5% of copper triglycinate but only 20.8+/-9.9% of copper tetraglycinate penetrated the digestive membrane without modification. Furthermore, inorganic copper species were not detected but a new copper complex (m/z 442) was found to be formed in both compartments of the Ussing chamber.

Characterization of metal-peptide complexes in feed supplements of essential trace elements.

Metal chelates with biomolecules are increasingly used in animal supplementation to increase the bioavailability of essential trace elements. However, the transfer of the chelates is not well understood and speciation studies may bring a comprehensive insight to further investigate the biological uptake mechanism(s) implicated. An analytical method was developed for the characterization of the water-soluble metal complexes in animal feed supplements obtained by reaction of a metal salt with a non-GMO soybean enzymatic digest. The method was based on fractionation of the extract by size-exclusion chromatography followed by the analysis of the metal-containing fraction by reversed-phase nanoHPLC with parallel ICP MS and electrospray MS/MS detection. The metal complexes were identified in the mass spectra owing to the Cu characteristic isotopic pattern; the complexation was corroborated by the presence of a peak corresponding to the non-metallated peptide. The study demonstrated the feasibility of SEC-ICP MS to produce characteristic metal (Cu, Zn, Mn, Fe) distribution patterns, which can be of interest to test batch-to-batch reproducibility and to determine the origin of the supplement. The use of the method could be extended to animal feeds prepared using the metal-chelated complexes. Electrospray MS/MS allowed the identification of a number of Cu complexes with peptides. Four different structure conformations were modeled by means of molecular mechanics investigations to assess the chelation stability.

Interaction effects of lactic acid and acetic acid at different temperatures on ethanol production by Saccharomyces cerevisiae in corn mash.

The combined effects of lactic acid and acetic acid on ethanol production by S. cerevisiae in corn mash, as influenced by temperature, were examined. Duplicate full factorial experiments (three lactic acid concentrations x three acetic acid concentrations) were performed to evaluate the interaction between lactic and acetic acids on the ethanol production of yeast at each of the three temperatures, 30, 34, and 37 degrees C. Corn mash at 30% dry solids adjusted to pH 4 after lactic and acetic acid addition was used as the substrate. Ethanol production rates and final ethanol concentrations decreased (P<0.001) progressively as the concentration of combined lactic and acetic acids in the corn mash increased and the temperature was raised from 30 to 37 degrees C. At 30 degrees C, essentially no ethanol was produced after 96 h when 0.5% w/v acetic acid was present in the mash (with 0.5, 2, and 4% w/v lactic acid). At 34 and 37 degrees C, the final concentrations of ethanol produced by the yeast were noticeably reduced by the presence of 0.3% w/v acetic acid and >or=2% w/v lactic acid. It can be concluded that, as in previous studies with defined media, lactic acid and acetic acid act synergistically to reduce ethanol production by yeast in corn mash. In addition, the inhibitory effects of combined lactic and acetic acid in corn mash were more apparent at elevated temperatures.

Acute and subchronic toxicity studies on Sel-Plex, a standardized, registered high-selenium yeast.

Selenium has been recognized as an essential nutrient for human health; however, its bioavailability is primarily dependent upon the type of selenium, elemental versus organic. In geographic areas low in selenium, there is the potential for animals (including humans) to become selenium deficient and this potential deficiency can be remedied by consumption of exogenous selenium, including selenium-enriched yeast (Saccharomyces cerevisiae) that contains high levels of organic selenium (e.g., selenized yeast). The present studies were conducted to investigate potential oral toxicity of a unique selenized yeast preparation (Sel-Plex) when administered to (1) adult female CHS Swiss mice ICo:OFI (IOPS Caw); (2) adult female CHS Sprague-Dawley rats; and (3) adult male and female Sprague-Dawley CD rats. For the 28- and 90-day toxicity studies, (1) adult male and female Sprague-Dawley CRL:CD(R)(SD) IGS BR strain rats and (2) adult male and female 6- to 7-month-old Beagle dogs were used. The LD50 for mice was >or=2000 mg Sel-Plex/kg (>or=4.06 mg Se/kg) and for rats, was greater than >or=2000 mg Sel-Plex/kg (>or=4.06 mg Se/kg). In the two 28-day studies, for rats, the no observed adverse effects level (NOAEL) was 50 mg Sel-Plex/kg/day (0.1 mg Se/kg/day), and for the dogs, the NOAEL was 22.5 mg Sel-Plex/kg/day (0.045 mg Se/kg/day). For the two 90-day studies, for rats the NOAEL for Sel-Plex was 114 mg/kg/day (0.23 mg Se/kg/day), and for dogs, the NOAEL was 30 mg Sel-Plex/kg/day (0.06 mg Se/kg/day): the latter being the NOAEL in the most sensitive species.

Genotoxicity studies on Sel-Plex, a standardized, registered high-selenium yeast.

Selenium, recognized as an essential nutrient for human health, is a component of proteins and enzymes required for various biological functions and is currently being used as a feed supplement for livestock in geographical areas that are naturally low in selenium. Selenium is structurally similar to sulfur, replacing the sulfur atom in stoichiometric amounts and thus functions through an association with proteins, termed selenoproteins. In geographic areas low in selenium, there is the potential for animals (including humans) to become selenium deficient and this potential deficiency can be remedied by consumption of exogenous selenium, including selenium-enriched yeast (Saccharomyces cerevisiae) that contains high levels of organic selenium (e.g., selenized yeast). A unique, standardized, registered high selenium food-grade baker's yeast (S. cerevisiae; Sel-Plex), was tested in the following battery of Genotoxicity assays; (1) a bacterial reverse mutation test (Ames test); (2) an in vitro mammalian chromosome aberration test; and (3) a mouse micronucleus test. Under the conditions of this assay, Sel-Plex showed no evidence of mutagenic activity in Salmonella typhimurium, in the bacterial reverse mutation test. Sel-Plex did not induce significant chromosomal aberrations in cultured human lymphocytes in the in vitro mammalian chromosome aberration test. Sel-Plex did not statistically increase the frequency or proportion of micronucleated immature erythrocytes in the mouse micronucleus test. Thus, from the studies presented here, the authors conclude that Sel-Plex is nongenotoxic.