The Role of Glycolysis and Hexose Monophosphate Pathway in the Hypoxic Toxicity of Misonidazole

The metabolic activation of misonidazole (MISO) and its effects on the hexose monophosphate pathway (HMP) and clonogenicity were studied in hypoxic EMT6/R0, wildtype Chinese hamster ovary (CHO) and mutant CHO cells deficient in glucose-6-phosphate dehydrogenase. In all three cell lines metabolic activation of MISO, as indicated by the binding of ^l4C-MISO to the acid-insoluble fraction of these cells, was increased by the presence of glucose. In EMT6/R0 cells and wildtype CHO cells, MISO caused a significant stimulation of the activity of the HMP while in the mutant CHO cells no HMP activity was measurable, even in the presence of MISO. Loss of clonogenicity induced by MISO occurred markedly earlier in EMT6/R0 cells than in the CHO cells. In the latter cells, however, only a small difference was observed between the wildtype and mutant cell line. From these results it is concluded that not only the HMP but also glycolysis and other, glucose-independent, metabolic pathways are able to provide electrons for the reductive activation of MISO and hence contribute to the hypoxic toxicity of this compound.     

Oligosaccharides in feces of breast- and formula-fed babies

So far, little is known on the fate of oligosaccharides in the colon of breast- and formula-fed babies. Using capillary electrophoresis with laser induced fluorescence detector coupled to a mass spectrometer (CE–LIF–MSⁿ), we studied the fecal oligosaccharide profiles of 27 two-month-old breast-, formula- and mixed-fed preterm babies. The interpretation of the complex oligosaccharide profiles was facilitated by beforehand clustering the CE–LIF data points by agglomerative hierarchical clustering (AHC). In the feces of breast-fed babies, characteristic human milk oligosaccharide (HMO) profiles, showing genetic fingerprints known for human milk of secretors and non-secretors, were recognized. Alternatively, advanced degradation and bioconversion of HMOs, resulting in an accumulation of acidic HMOs or HMO bioconversion products was observed. Independent of the prebiotic supplementation of the formula with galactooligosaccharides (GOS) at the level used, similar oligosaccharide profiles of low peak abundance were obtained for formula-fed babies. Feeding influences the presence of diet-related oligosaccharides in baby feces and gastrointestinal adaptation plays an important role herein. Four fecal oligosaccharides, characterized as HexNAc-Hex-Hex, Hex-[Fuc]-HexNAc-Hex, HexNAc-[Fuc]-Hex-Hex and HexNAc-[Fuc]-Hex-HexNAc-Hex-Hex, highlighted an active gastrointestinal metabolization of the feeding-related oligosaccharides. Their presence was linked to the gastrointestinal mucus layer and the blood-group determinant oligosaccharides therein, which are characteristic for the host’s genotype.     

Heat-Melt of β-1, 3-d-Glucan Gel

Six new products of oxidation of indolyl-3-acetic add catalyzed by horseradish peroxidase were isolated, along with four known ones, 3-hydroxymethyloxindole (1), 3-methyleneoxindole (2), indolyl-3-aldehyde (4), and 3,3-diindolylmethane (10). Based on spectroscopic and chemical evidence, the new products were identified as 3-acetoxyindole (3), 3-(indol-3-ylmethyl)oxindole (6), 3-[(2-mdol-3-ylmethyl)indol-3-ylmethyl]oxindole (9), the 3-hydroxymethyl compounds of 6 and 9 (5 and 7), and 2-(indol-3-ylmethyl)indolyl-3-acetic acid (8), respectively.     

Correlated responses of root growth and sugar concentrations to various defoliation treatments and rhythmic shoot growth in oak tree seedlings (Quercus pubescens)

Background and Aims

To understand whether root responses to aerial rhythmic growth and contrasted defoliation treatments can be interpreted under the common frame of carbohydrate availability; root growth was studied in parallel with carbohydrate concentrations in different parts of the root system on oak tree seedlings.

Methods

Quercus pubescens seedlings were submitted to selective defoliation (removal of mature leaves, cotyledons or young developing leaves) at appearance of the second flush and collected 1, 5 or 10 d later for morphological and biochemical measurements. Soluble sugar and starch concentrations were measured in cotyledons and apical and basal root parts.

Key Results

Soluble sugar concentration in the root apices diminished during the expansion of the second aerial flush and increased after the end of aerial growth in control seedlings. Starch concentration in cotyledons regularly decreased. Continuous removal of young leaves did not alter either root growth or apical sugar concentration. Starch storage in basal root segments was increased. After removal of mature leaves (and cotyledons), root growth strongly decreased. Soluble sugar concentration in the root apices drastically decreased and starch reserves in the root basal segments were emptied 5 d after defoliation, illustrating a considerable shortage in carbohydrates. Soluble sugar concentrations recovered 10 d after defoliation, after the end of aerial growth, suggesting a recirculation of sugar. No supplementary recourse to starch in cotyledons was observed.

Conclusions

The parallel between apical sugar concentration and root growth patterns, and the correlations between hexose concentration in root apices and their growth rate, support the hypothesis that the response of root growth to aerial periodic growth and defoliation treatments is largely controlled by carbohydrate availability.     

The Candida albicans gene HGT12 (orf19.7094) encodes a hexose transporter

Yeast cells of the human pathogen Candida albicans that enter the bloodstream can be engulfed by macrophage cells but survive in, and can escape from, the phagolysosome. The C. albicans gene HGT12, which is specifically expressed during macrophage infection, encodes a protein that transports fructose, glucose and mannose. Expression of this hexose transporter along with the shift from glycolysis to gluconeogenesis that occurs in these phagocytosed cells suggests a requirement for glucose that can be supplied in part by uptake from the lumen of the phagolysosome.     

Water soluble feruloyl arabinoxylans from rice and ragi: changes upon malting and their consequence on antioxidant activity

The objective of this study is to determine the changes brought about by germination on water soluble feruloyl arabinoxylans (feraxans), one of the major components of soluble fibre from rice and ragi and their consequence on antioxidant activity. Soluble feraxans, isolated from native and malted rice and ragi were fractionated on DEAE-cellulose. Ferulic acid content of the major [0.1 molar ammonium carbonate (AC) eluted] fraction was higher in malts (rice: 1045 microg/g; ragi: 1404 microg/g) than in native (rice: 119 microg/g; ragi: 147 microg/g) and this fraction was separated by Sephacryl S-300 chromatography into two peaks each in rice (native: 232 and 24.4 kDa; malt: 75.4 and 39.6 kDa) and ragi (native: 140 and 15.4 kDa; malt: 38.9 and 15.4 kDa). 0.1 molar AC eluted fractions showed very strong antioxidant activity in vitro as determined by beta-carotene-linoleate emulsion (IC50: 0.16-0.24 mg), DPPH* (IC50: 4.1-11.4 mg) and Ferric reducing/antioxidant power, FRAP (EC1: 0.76-3.1mg) assays. Antioxidant activity of feraxans was several (4.9-1400) folds higher than the expected activity due to their bound ferulic acid content. Apart from ferulic acid, presence of sugars with >C=O (uronyl/acetyl) groups and degree/nature of glycan-polymerization were observed to influence antioxidant activity of the polysaccharides. Malting resulted in many dynamic changes in the ferulic acid content in different feraxan types and affected their antioxidant activity.     

Measuring microbial fitness in a field reciprocal transplant experiment

Microbial fitness is easy to measure in the laboratory, but difficult to measure in the field. Laboratory fitness assays make use of controlled conditions and genetically modified organisms, neither of which are available in the field. Among other applications, fitness assays can help researchers detect adaptation to different habitats or locations. We designed a competitive fitness assay to detect adaptation of Saccharomyces paradoxus isolates to the habitat they were isolated from (oak or larch leaf litter). The assay accurately measures relative fitness by tracking genotype frequency changes in the field using digital droplet PCR (DDPCR). We expected locally adapted S. paradoxus strains to increase in frequency over time when growing on the leaf litter type from which they were isolated. The DDPCR assay successfully detected fitness differences among S. paradoxus strains, but did not find a tendency for strains to be adapted to the habitat they were isolated from. Instead, we found that the natural alleles of the hexose transport gene we used to distinguish S. paradoxus strains had significant effects on fitness. The origin of a strain also affected its fitness: strains isolated from oak litter were generally fitter than strains from larch litter. Our results suggest that dispersal limitation and genetic drift shape S. paradoxus populations in the forest more than local selection does, although further research is needed to confirm this. Tracking genotype frequency changes using DDPCR is a practical and accurate microbial fitness assay for natural environments.     

木薯己糖激酶MeHXK5的催化功能鉴定

该研究利用ISSR分子标记,对分布于福建省内5个样地( 邵武、建阳、建瓯、周宁和屏南)的61个野钩锥(Castanopsis tibetana)单株的遗传多样性进行了分析,并采用聚类分析方法探讨了它们的遗传关系。结果表明： 用10条ISSR引物从61个单株的基因组DNA共扩增出158条带,包含145条多态性条带,多态性条带百分率达91.77%,其中引物 UBC817、UBC819与UBC842的多态性条带百分率（PPB）为100.0%。各居群的多态性条带百分率(PPB)、有效等位基因数(Ne)、Nei’s基因多样度(H)和Shannon’s多样性指数（I）等各遗传指数差异较大,其中各项遗传指标中最高的为邵武居群,而周宁居群则最低。5个居群的基因分化系数和基因流分别为0.144 0和2.973 0,说明5个居群总遗传变异的14.40%存在于居群间,85.60%存在于居群内。种间总基因多样度分别为0.395 8,种内基因多样度分别为0.338 8,表明钩锥种间遗传多样性较高,且种间变异大于种内变异。各居群间的遗传距离差异较大; 其中,邵武与建瓯居群的遗传距离最近,仅为0.081 5; 建阳和周宁居群的遗传距离最远,为0.162 9。通过聚类分析可将5个钩锥居群聚为3支,屏南与周宁的居群各自独立聚为2支;来自邵武、建瓯及建阳的居群聚为一支,且可进一步分为两个亚支,建阳居群为1个亚支,邵武和建瓯居群聚为1个亚支。供试的钩锥具有较高的遗传多样性,存在着较为频繁的基因交流。该研究结果较准确地揭示了钩锥种间的遗传多样性。     

亚硫酸盐废液中戊糖己糖同步酒精发酵中间试验

木材在亚硫酸盐法制浆过程中,占木材干重２０％～３０％的半纤维素降解成单糖而溶于废液中,废液中单糖的利用,不仅能够充分利用生物质资源,而且对于后续产品木质素的深加工十分必要。废液中糖主要由己糖和戊糖组成,近年来,随着阔叶材在制浆原料中的比例不断增加,废...     

Hydroperoxy fatty acid formation in selenium deficient rat platelets: coupling of glutathione peroxidase to the lipoxygenase pathway

After incubation with [1-14C]-arachidonic acid, washed platelets from selenium deficient rats produced a sevenfold greater amount of 12-hydroperoxytetraenoic acid than platelets from control animals. When stimulated with either arachidonic acid or t-butyl-hydroperoxide, antimycin-A1 treated platelets from the deficient rats also converted markedly lower amounts of [1-14C]-glucose to [14C]-CO2 than platelets from control rats. These results indicate a significant role for platelet selenium-dependent glutathione peroxidase in the enzymatic reduction of platelet-produced hydroperoxides.