大叶杨配囊及胚珠的形成和发育

本文应用细胞化学方法研究了大叶杨胚珠、胚囊的形成和发育过程中核酸、蛋白质及不溶性多糖的分布和消长。大孢子母细胞、大孢子四分体及功能大孢子中含较少不溶性多糖,但却含丰富的RNA和蛋白质。功能大孢子经分裂发育成八核的蓼型胚囊。四核胚囊开始积累细胞质多糖,成熟胚囊中除反足细胞外充满淀粉粒。反足细胞形成后不久即退化。助细胞具多糖性质的丝状器,受精前两个助细胞退化。卵细胞核对Feulgen反应呈负反应。二极核受精前由胚囊中部移向卵器,与卵器接触后融合形成次生核。发育早期的胚珠为厚珠心,双珠被。晚期,内珠被退化,故成熟胚珠为单珠被。四核胚囊时期,珠孔端珠心组织退化,胚囊伸向珠孔形成胚囊喙。合点端珠心组织含丰富的蛋白质和核酸,这一性质与绒毡层性质相似,可能涉及胚囊的营养运输。胚囊的营养来源于子房和胎座细胞内贮存的淀粉粒。     

Optimization of adsorption conditions of papain on dye affinity membrane using response surface methodology

The adsorption of papain on Reactive Blue 4 dye–ligand affinity membrane was investigated in a batch system. The combined effects of operating parameters such as initial pH, temperature, and initial papain concentration on the adsorption were analyzed using response surface methodology. The optimum adsorption conditions were determined as initial pH 7.05, temperature 39 °C, and initial papain concentration 11.0 mg/ml. At optimum conditions, the adsorption capacity of dye–ligand affinity membrane for papain was found to be 27.85 mg/g after 120 min adsorption. The papain was purified 34.6-fold in a single step determined by fast protein liquid chromatography. More than 85% of the adsorbed papain was desorbed using 1.0 M NaCl at pH 9.0 as the elution agent. The purification process showed that the dye–ligand immobilized composite membrane gave good separation of papain from aqueous solution.     

Extremely high prevalence of neural tube defects in a 4-county area in Shanxi Province, China

BACKGROUND: In the past, northern China's Shanxi Province has reported the highest incidence of neural tube defects (NTDs) in the world. However, little is known about the epidemiology of NTDs in this area in recent years. METHODS: Data were collected from a population-based birth defects surveillance system in 4 counties that captures information on all live births, stillbirths of at least 20 weeks' gestation, and pregnancy terminations at any gestational age resulting from prenatal diagnosis of a birth defect. We also surveyed mothers of NTD case patients to determine their use of folic acid before and during early pregnancy. RESULTS: During 2003, 160 NTD cases were identified among 11,534 births (NTD birth prevalence = 138.7/10,000 births). The rates of anencephaly, spina bifida and encephalocele were 65.9, 58.1, and 14.7 per 10,000, respectively, and a female predominance was observed among anencephaly cases (male-to-female relative risk [RR], 0.49; 95% confidence interval [CI], 0.30-0.79), but not among spina bifida (RR, 0.90; 95% CI, 0.55-1.45) and encephalocele (RR, 1.03; 95% CI, 0.40-2.69) cases. The percentages of pregnancy termination following prenatal diagnosis of anencephaly, spina bifida, and encephalocele were 50%, 41.8%, and 35.3%, respectively. NTD birth prevalence tended to be higher among mothers aged <20 or > or =30 years (P = .06) and was markedly associated with lower levels of maternal education (P < .001). Among 143 NTD mothers, only 6 (4.2%) used folic acid supplements during the periconceptional period. CONCLUSIONS: The NTD birth prevalence rate in the study area is among the highest worldwide. Folic acid deficiency may be one important risk factor.     

兼具SOD和GPX活力的双功能酶的制备及性质研究

用苯甲基磺酰氟（ＰＭＳＦ）和Ｈ_２Ｓｅ相继处理铜锌超氧化物岐化酶（Ｃｕ,Ｚｎ－ＳＯＤ）,将酶分子中的丝氨酸（Ｓｅｒ）转化为硒代半胱氨酸（ＳｅＣｙｓ）,从而引入了谷胱甘肽过氧化物酶（ＧＰＸ）的催化基团,使其在ＳＯＤ酶活性大部分保留的情况下,具有ＧＰＸ活性,其ＧＰＸ活力是ＰＺ５１活力的３０倍。研究了双功能酶的最佳制备条件,包括ＰＭＳＦ的剂量、反应最适温度及Ｈ_２Ｓｅ处理时间等,并用电子能谱、ＤＴＮＢ等方法测定了双功能酶的硒含量;测定了双功能酶对不同底物的米氏常数及双功能酶的荧光光谱、紫外吸收光谱及稳定性。     

Systematical detection of significant genes in microarray data by incorporating gene interaction relationship in biological systems

Many methods, including parametric, nonparametric, and Bayesian methods, have been used for detecting differentially expressed genes based on the assumption that biological systems are linear, which ignores the nonlinear characteristics of most biological systems. More importantly, those methods do not simultaneously consider means, variances, and high moments, resulting in relatively high false positive rate. To overcome the limitations, the SWang test is proposed to determine differentially expressed genes according to the equality of distributions between case and control. Our method not only latently incorporates functional relationships among genes to consider nonlinear biological system but also considers the mean, variance, skewness, and kurtosis of expression profiles simultaneously. To illustrate biological significance of high moments, we construct a nonlinear gene interaction model, demonstrating that skewness and kurtosis could contain useful information of function association among genes in microarrays. Simulations and real microarray results show that false positive rate of SWang is lower than currently popular methods (T-test, F-test, SAM, and Fold-change) with much higher statistical power. Additionally, SWang can uniquely detect significant genes in real microarray data with imperceptible differential expression but higher variety in kurtosis and skewness. Those identified genes were confirmed with previous published literature or RT-PCR experiments performed in our lab.     

Gap junctional communication is required to maintain mouse cortical neural progenitor cells in a proliferative state

The mechanisms that determine whether neural stem cells remain in a proliferative state or differentiate into neurons or glia are largely unknown. Here we establish a pivotal role for gap junction-mediated intercellular communication in determining the proliferation and survival of mouse neural progenitor cells (NPCs). When cultured in the presence of basic fibroblast growth factor (bFGF), NPCs express the gap junction protein connexin 43 and are dye-coupled. Upon withdrawal of bFGF, levels of connexin 43 and dye coupling decrease, and the cells cease proliferating and differentiate into neurons; the induction of gap junctions by bFGF is mediated by p42/p44 mitogen-activated protein kinases. Inhibition of gap junctions abolishes the ability of bFGF to maintain NPCs in a proliferative state resulting in cell differentiation or cell death, while overexpression of connexin 43 promotes NPC self-renewal in the absence of bFGF. In addition to promoting their proliferation, gap junctions are required for the survival of NPCs. Gap junctional communication is therefore both necessary and sufficient to maintain NPCs in a self-renewing state.     

Effects of salinity on food intake, growth, and survival of pufferfish (Fugu obscurus)

The food intake, growth, food conversion ratio and survival of yearling pufferfish, Fugu obscurus Abe, were investigated under different water salinity conditions over a 54‐day period. Within the salinity regimes of 0 (freshwater), 8, 18, and 35‰, the food intake levels were 0.97%, 1.43%, 1.19% and 1.01%, respectively; food conversion ratios were 1.31, 1.93, 1.61 and 1.36, respectively; and specific growth rates were 0.41%, 1.15%, 0.84%, and 0.35%, respectively. The three data series were reduced with increasing salinity. However, the survival rates did not show the same tendencies, which were 80%, 100%, 100%, and 67%, respectively. There were significant differences among the treatments. In conclusion, the yearling pufferfish optimum culture salinity condition was about 8‰.     

Complement C1q activates canonical Wnt signaling and promotes aging-related phenotypes

Wnt signaling plays critical roles in development of various organs and pathogenesis of many diseases, and augmented Wnt signaling has recently been implicated in mammalian aging and aging-related phenotypes. We here report that complement C1q activates canonical Wnt signaling and promotes aging-associated decline in tissue regeneration. Serum C1q concentration is increased with aging, and Wnt signaling activity is augmented during aging in the serum and in multiple tissues of wild-type mice, but not in those of C1qa-deficient mice. C1q activates canonical Wnt signaling by binding to Frizzled receptors and subsequently inducing C1s-dependent cleavage of the ectodomain of Wnt coreceptor low-density lipoprotein receptor-related protein 6. Skeletal muscle regeneration in young mice is inhibited by exogenous C1q treatment, whereas aging-associated impairment of muscle regeneration is restored by C1s inhibition or C1qa gene disruption. Our findings therefore suggest the unexpected role of complement C1q in Wnt signal transduction and modulation of mammalian aging.     

MiR-17-92 cluster regulates cell proliferation and collagen synthesis by targeting TGFB pathway in mouse palatal mesenchymal cells

Elongation and elevation of palatal shelves, mainly caused by proliferation and extra-cellular matrix synthesis of palatal mesenchymal cells (PMCs), are essential for normal palatal development. Transforming growth factor beta (TGFB) pathway could induce proliferation inhibition and collagen synthesis in PMCs. Recent studies found that miRNA-17-92 (miR-17-92) cluster, including miR-17, miR-18a, miR-19a, miR-20a, miR-19b, and miR-92a, expressed in the 1st bronchial arch of mouse embryos during the period of palatal shelf elongation and elevation, and directly targeted TGFB pathway in cancer cell lines. Whether miR-17-92 cluster expresses and targets TGFB pathway in PMCs has not yet been studied. Using quantitative real-time RT-PCR, we found that miR-17-92 expressed in PMCs and decreased from embryonic day (E) 12 to E14 in palatal shelves. MTT assay and Western blot showed that miR-17-92 inhibited TGFB1 induced proliferation inhibition and collagen synthesis in PMCs by decreasing TGFBR2, SMAD2, and SMAD4 protein level. Further luciferase assay showed that miR-17 and miR-20a directly targeted 3′UTR of TGFBR2, and that miR-18a directly targeted 3′UTR of SMAD2 and SMAD4. We thus conclude that miR-17-92 cluster could inhibit TGFB pathway induced proliferation inhibition and collagen synthesis in PMCs by directly targeting TGFBR2, SMAD2, and SMAD4.     

Microbial community of aerobic granules for ammonium and sulphide removal in a sequencing batch reactor

Aerobic granules for sulphide and ammonium removal were cultivated in a sequencing batch reactor, and the microbial community of the aerobic granules was investigated by denaturing gradient gel electrophoresis. The loading rate increased from 0.15 to 0.9 kg S2? m?3 d?1, and the removal efficiencies of sulphide, chemical oxygen demand, and NH4 +-N were higher than 99, 80, and 98%, respectively. However, sludge settleability became poorer when the loading rate exceeded 0.3 kg S2? m?3 d?1. The denitrifying bacteria in the aerobic granules were Thauera sp., Pseudomonas alcaligenes, and uncultured planctomycetes, indicating that multiple N-removing processes occurred simultaneously in the aerobic granules. These processes could include nitrification and denitrification, aerobic denitrification, and anaerobic ammonia oxidation. Sludge settleability became poorer because of the overgrowth of uncultured Thiothrix sp.