Assessment of association of rs2200733 on chromosome 4q25 with atrial fibrillation and ischemic stroke in a Chinese Han population

Atrial fibrillation (AF) is the most common arrhythmia in the clinical setting and an independent risk factor for stroke. Approximately 10 million Chinese people are affected by AF, but the genetic basis is largely unknown. A recent genome-wide association study in Iceland identified association between SNP rs2200733 on 4q25 and AF; however, many independent replication studies are essential to unequivocally validate this association. To assess the association between rs2200733 and AF as well as that between rs2200733 and ischemic stroke in a mainland Chinese Han population, we carried out case–control association studies with 383 AF patients versus 851 non-AF controls and 811 ischemic stroke patients versus 688 non-stroke controls. Highly significant association was detected between rs2200733 and AF in a Chinese Han population (allelic P = 3.7 × 10^?11 with OR = 1.81; genotypic P = 4.1 × 10^?12 with a dominant model). When the AF cases were divided into lone AF (32.6%) and other types of AF (67.4%), significantly stronger association was found with lone AF (OR = 2.40, P = 1.3 × 10^?9 compared to OR = 1.59, P = 6.2 × 10^?7 for other types of AF; P = 0.02 for two ORs). No significant association was found between rs2200733 and ischemic stroke. Our results suggest that SNP rs2200733 confers a highly significant risk of AF, but not ischemic stroke, in a more representative Chinese Han population in the mainland China.     

An innovative consecutive batch fermentation process for very high gravity ethanol fermentation with self-flocculating yeast

An innovative consecutive batch fermentation process was developed for very high gravity (VHG) ethanol fermentation with the self-flocculating yeast under high biomass concentration conditions. On the one hand, the high biomass concentration significantly shortened the time required to complete the VHG fermentation and the duration of yeast cells suffering from strong ethanol inhibition, preventing them from losing viability and making them suitable for being repeatedly used in the process. On the other hand, the separation of yeast cells from the fermentation broth by sedimentation instead of centrifugation, making the process economically more competitive. The VHG medium composed of 255 g L⁻¹ glucose and 6.75 g L⁻¹ each of yeast extract and peptone was fed into the fermentation system for nine consecutive batch fermentations, which were completed within 8–14 h with an average ethanol concentration of 15% (v/v) and ethanol yield of 0.464, 90.8% of its theoretical value of 0.511. The average ethanol productivity that was calculated with the inclusion of the downstream time for the yeast flocs to settle from the fermentation broth and the supernatant to be removed from the fermentation system was 8.2 g L⁻¹ h⁻¹, much higher than those previously reported for VHG ethanol fermentation and regular ethanol fermentation with ethanol concentration around 12% (v/v) as well.     

Enhanced uridine diphosphate <Emphasis Type="Italic">N</Emphasis>-acetylglucosamine production using whole-cell catalysis

Uridine diphosphate N-acetylglucosamine (UDPAG) can be produced by chemical, enzymatic, chemoenzymatic, and fermentative methods. In this study, we used whole-cell catalysis method to produce UDPAG for the first time by Saccharomyces cerevisiae. In order to increase the ATP utilization efficiency and UDPAG conversion yield, the response surface methodology was applied to optimize the whole-cell catalytic conditions for UDPAG production. Firstly, effects of uridine 5′-monophosphate (5′-UMP), glucosamine, vitamin B1, glycerol, magnesium chloride, potassium chloride, temperature, sodium dihydrogen phosphate, sodium acetate, fructose, and pH on UDPAG production were evaluated by a fractional factorial design. Results showed that UDPAG production was mainly affected by sodium dihydrogen phosphate, temperature, and vitamin B1. Then, the concentrations of sodium dihydrogen phosphate and vitamin B1 and temperature were further investigated with a central composite design and response surface analysis. The cultivation conditions to obtain the optimal UDPAG production were determined: sodium dihydrogen phosphate, 31.2 g/L; temperature, 29°C, and vitamin B1, 0.026 g/L. This optimization strategy led to an enhancement of UDPAG production from 2.51 to 4.25 g/L, yield from 44.6% to 75.6% based on the initial 5′-UMP concentration, and ATP utilization efficiency from 7.43% to 12.6%.     

A novel highly acidic β-mannanase from the acidophilic fungus Bispora sp. MEY-1: gene cloning and overexpression in Pichia pastoris

Using degenerate polymerase chain reaction (PCR) and thermal asymmetric interlaced PCR, a 1,347-bp full-length complementary DNA fragment encompassing the gene man5A, which encodes a 429-amino acid β-mannanase with a calculated mass of 46.8 kDa, was cloned from acidophilic Bispora sp. MEY-1. The deduced amino acid sequence (catalytic domain) displayed highest identity (54.1%) with the Emericella nidulans endo-β-1,4-d-mannanase, a member of the glycoside hydrolase family 5. Recombinant MAN5A was overexpressed in Pichia pastoris, and its activity in the culture medium reached 500 U ml⁻¹. The enzyme was acidophilic, with highest activity at pH 1.0–1.5, lower than any known mannanases, and optimal temperature for activity was 65°C. MAN5A had good pH adaptability, excellent thermal and pH stability, and high resistance to both pepsin and trypsin. The specific activity, K _m, and V _max for locust bean gum substrate was 3,373 U mg⁻¹, 1.56 mg ml⁻¹, and 6,587.6 μmol min⁻¹ mg⁻¹, respectively. The enzymatic activity was not significantly affected by ions such as Ca²⁺, Cr³⁺, Co²⁺, Zn²⁺, Na⁺, K⁺, and Mg²⁺ and enhanced by Ni²⁺, Fe³⁺, Mn²⁺ and Ag⁺. These favorable properties make MAN5A a potential candidate for use in various industrial applications.     

Spatial variation of the stable nitrogen isotope ratio of woody plants along a topoedaphic gradient in a subtropical savanna

Variation in the stable N isotope ratio (δ¹⁵N) of plants and soils often reflects the influence of environment on the N cycle. We measured leaf δ¹⁵N and N concentration ([N]) on all individuals of Prosopis glandulosa (deciduous tree legume), Condalia hookeri (evergreen shrub), and Zanthoxylum fagara (evergreen shrub) present within a belt transect 308 m long × 12 m wide in a subtropical savanna ecosystem in southern Texas, USA in April and August 2005. Soil texture, gravimetric water content (GWC), total N and δ¹⁵N were also measured along the transect. At the landscape scale, leaf δ¹⁵N was negatively related to elevation for all the three species along this topoedaphic sequence. Changes in soil δ¹⁵N, total N, and GWC appeared to contribute to this spatial pattern of leaf δ¹⁵N. In lower portions of the landscape, greater soil N availability and GWC are associated with relatively high rates of both N mineralization and nitrification. Both soil δ¹⁵N and leaf [N] were positively correlated with leaf δ¹⁵N of non-N₂ fixing plants. Leaf δ¹⁵N of P. glandulosa, an N₂-fixing legume, did not correlate with leaf [N]; the δ¹⁵N of P. glandulosa’s leaves were closer to atmospheric N₂ and significantly lower than those of C. hookeri and Z. fagara. Additionally, at smaller spatial scales, a proximity index (which reflected the density and distance of surrounding P. glandulosa trees) was negatively correlated with leaf δ¹⁵N of C. hookeri and Z. fagara, indicating the N₂-fixing P. glandulosa may be important to the N nutrition of nearby non-N₂-fixing species. Our results indicate plant ¹⁵N natural abundance can reflect the extent of N retention and help us better understand N dynamics and plant-soil interactions at ecosystem and landscape scales.     

Field evaluation of juvenile in vitro embryo transfer (JIVET) in sheep

The practicality of using juvenile in vitro embryo transfer (JIVET) on a field scale in China was evaluated in each of three seasons (summer, autumn and winter) from 2006 to 2007. A total of 102 donor Merino lambs (18 summer, 69 autumn and 15 winter) aged 4-8 weeks were stimulated with 4 x 40 mg FSH administered at 12h intervals plus 400 IU PMSG given at the time of the first FSH treatment. Overall, 89.2% (91/102) of the lambs exhibited follicle development and 79.1+/-65.5 (mean+/-S.D.) cumulus-oocyte complexes were recovered per donor lamb. Compared with the groups of summer (84.9+/-55.3) and autumn (83.6+/-70.8) lambs, the number of recovered cumulus-oocyte complexes was significantly decreased in winter (51.4+/-43.7; p<0.05). After recovery, the cumulus-oocyte complexes were matured and fertilized in vitro using frozen-thawed semen and culture in synthetic oviduct fluid medium to the 2-4-c stage of development, when they were transferred surgically in groups of 3-8 (5.33+/-1.47) to the ipsilateral uterine horn of a total of 603 synchronized recipients. The overall mean proportion of cumulus-oocyte complexes developing to 2-c embryos was 61.4% (4308/7013) and differed significantly between seasons (summer 38.5%, autumn 66.1%, winter 74.6%; p<0.01). Pregnancy rate assessed by ultrasound examination approximately 60 days after embryo transfer was 54.4% (328/603) overall, and 36.7% (221/603) of the recipients maintained their pregnancy to full-term, producing an average 1.49 (330/221) offspring, of which 1.21 (267/221) were viable and healthy lambs, per pregnant recipient. Pregnancy rate at day 60 was affected by season (summer 40.5%, autumn 56.7%, winter 55.7%; p<0.05), but did not differ significantly between seasons at full-term (summer 34.2%, autumn 38.9%, winter 30.4%; p>0.05). Based on the number of donors stimulated, the total number of offspring and viable progeny produced per donor lamb in autumn (5.81 and 4.87) was significantly (p<0.01) higher than that of summer (2.79 and 1.94) and winter (4.24 and 3.31). This study showed that each donor lamb after stimulation produced an average of 48.6 transferable embryos that resulted in 4.04 viable and healthy progeny. These results indicate that JIVET is a cost-effective method of multiplying desirable sheep genotypes in China.     

A genome-wide screen in Saccharomyces cerevisiae reveals pathways affected by arsenic toxicity

We have used Saccharomyces cerevisiae to identify toxicologically important proteins and pathways involved in arsenic-induced toxicity and carcinogenicity in humans. We performed a systemic screen of the complete set of 4733 haploid S. cerevisiae single-gene-deletion mutants to identify those that have decreased or increased growth, relative to wild type, after exposure to sodium arsenite (NaAsO₂). IC₅₀ values for all mutants were determined to further validate our results. Ultimately we identified 248 mutants sensitive to arsenite and 5 mutants resistant to arsenite exposure. We analyzed the proteins corresponding to arsenite-sensitive mutants and determined that they belonged to functional categories that include protein binding, phosphate metabolism, vacuolar/lysosomal transport, protein targeting, sorting, and translocation, cell growth/morphogenesis, cell polarity and filament formation. Furthermore, these data were mapped onto a protein interactome to identify arsenite-toxicity-modulating networks. These networks are associated with the cytoskeleton, ubiquitination, histone acetylation and the MAPK signaling pathway. Our studies have potential implications for understanding toxicity and carcinogenesis in arsenic-induced human conditions, such as cancer and aging.