Anti-Obese Effect of Glucosamine and Chitosan Oligosaccharide in High-Fat Diet-Induced Obese Rats

Objective: This study is to evaluate the anti-obese effects of glucosamine (GLC) and chitosan oligosaccharide (COS) on high-fat diet-induced obese rats. Methods: The rats were randomly divided into twelve groups: a normal diet group (NF), a high-fat diet group (HF), Orlistat group, GLC high-, middle-, and low-dose groups (GLC-H, GLC-M, GLC-L), COS1 (COS, number-average molecular weight ≤1000) high-, middle-, and low-dose groups (COS1-H, COS1-M, COS1-L), and COS2 (COS, number-average molecular weight ≤3000) high-, middle-, and low-dose groups (COS2-H, COS2-M, COS2-L). All groups received oral treatment by gavage once daily for a period of six weeks. Results: Rats fed with COS1 gained the least weight among all the groups (P < 0.01), and these rats lost more weight than those treated with Orlistat. In addition to the COS2-H and Orlistat groups, the serum total cholesterol (CHO) and low-density lipoprotein cholesterol (LDL-C) levels were significantly reduced in all treatment groups compared to the HF group (P < 0.01). The various doses of GLC, COS1 and COS2 reduced the expression levels of PPARγ and LXRα mRNA in the white adipose tissue. Conclusions: The results above demonstrated that GLC, COS1, and COS2 improved dyslipidemia and prevented body weight gains by inhibiting the adipocyte differentiation in obese rats induced by a high-fat diet. Thus, these agents may potentially be used to treat obesity.     

热稳定性对甲基对硫磷水解酶在毕赤酵母中分泌的影响

甲基对硫磷水解酶可生物降解有机磷农药,由于其特殊的应用价值,越来越受到人们的关注。来源于苍白杆菌的甲基对硫磷水解酶MPH-Och在毕赤酵母系统中不能有效地分泌表达。将热稳定性提高的突变体MPH-S274Q在毕赤酵母中表达,发现其毕赤酵母重组菌株经摇瓶诱导培养120 h后,培养上清的酶活力达到0.7 U/mL,蛋白分泌量是野生型的14倍,SDS-PAGE电泳图中培养上清有明显的蛋白质条带,进一步证明了分泌效率提高,该结果表明提高蛋白质的热稳定性可以作为提高外源蛋白在毕赤酵母中的分泌效率的一条有效途径。     

北京市主要行道树白蜡生长因子的模型研究

为了构建胸径生长估测模型,以便快速掌握行道树的生长状况,提高行道树调查效率。笔者采用随机抽样的方法,收集了北京城区主要行道树白蜡的胸径、树高、枝下高、冠幅、叶面积等生长指标,根据胸径等级进行分类,利用5种单因素变量模型构建胸径与多项生长指标的估测模型。结果表明,北京市中径级的行道树白蜡分布最为广泛,占总数的63%以上;白蜡胸径与树高的相关性最高,其余依次为冠幅、叶面积、枝下高,其指数估测模型H=98.2399-28.0859D+2.8115D²-0.0743D³,相关系数达0.9967,系统误差为0.3299%,相对其他模型效果更优;而白蜡胸径与多生长因素的估测首选模型为：D=0.5595H²-9.6656H+2.0172h²-9.2454h-1.0413W²+12.4859W-0.0188S²+1.4996S+6.2011,其均方根误差只有1.0242,而精度高达95.61%。本研究建立的白蜡胸径生长估测模型具有良好的效果,适用于各年龄段的行道树白蜡调查,为北京市行道树白蜡的生长状况、景观质量和生态效益的监测提供快速调查与数据更新理论模型。     

酸化剂对碱性土壤和水体的改良机制及其效果

本文主要概述了碱性土壤和水体的形成原因、危害以及酸化剂的种类和特点,总结了酸化剂对碱性土壤和水体的改良机制与应用,为碱性土壤和水体的改良提供参考。     

虾类肌肉白浊病病原和病理的研究进展

本文针对虾类肌肉白浊病易感染的罗氏沼虾、凡纳滨对虾、中国对虾进行了分析。从病毒、细菌、寄生虫和环境因素方面,总结了近十几年来虾类肌肉白浊病的病原和病理特征。归纳了虾类肌肉白浊病的流行病学、检测方法及综合防治。     

Dietary methionine requirement of juvenile blunt snout bream (Megalobrama amblycephala) at a constant dietary cystine level

A 9‐week feeding trial was conducted to investigate the dietary methionine requirement of juvenile Megalobrama amblycephala at a constant dietary cystine level. Six semipurified diets were formulated to contain graded dietary methionine levels from 3.9 to 15.4 g kg^?1 in about 2.5 g kg^?1 increments in the presence of 2.2 g kg^?1 cystine. Results showed that specific growth rate (SGR) and protein efficiency ratio (PER) significantly increased with increasing dietary methionine levels from 3.9 to 12.4 g kg^?1 and thereafter kept stable. Maximum protein productive value (PPV), nitrogen retention efficiency (NRE) and liver weight were observed in 8.5 g methionine kg^?1 diet. Protein contents in whole fish body were positively correlated with dietary methionine level, while lipid contents were negatively correlated with it. Morphological index and hepatic glutamate‐pyruvate transaminase (GPT) activities were independent of dietary methionine levels. However, dietary methionine supplementation significantly improved haematological parameters, plasma methionine and total essential amino acid contents and hepatic glutamate‐oxaloacetate transaminase (GOT) activities. Analysis of dose response using broken‐line regression on the basis of SGR and PPV versus dietary methionine level estimated the optimum dietary methionine requirements of juvenile M. amblycephala to be between 8.5 and 8.4 g kg^?1 of diet (25.0 and 24.7 g kg^?1 of protein) in the presence of 2.2 g kg^?1 cystine, respectively. Hence, the corresponding total sulphur amino acids requirements of this species were calculated to be 10.7 and 10.6 g kg^?1 of diet (31.5 and 31.2 g kg^?1 of dietary protein).     

稻蝗肠道真菌的除草活性筛选及菌株DH03的鉴定

利用涂布平板法从中华稻蝗肠道中分离得到6株真菌,活性筛选试验表明菌株DH03具有较好的除草活性。当供试质量浓度为100 μg/mL时,该菌株发酵液的乙酸乙酯提取物对稗草和反枝苋根生长的抑制率均大于80%,比阳性对照2,4-二氯苯氧乙酸的活性好;进一步研究表明发酵液活性物质主要集中在中等极性部分;该菌株的发酵液对盆栽稗草幼苗生长表现出较强的抑制作用,当喷施发酵液原液时,稗草的受害率和均株高分别为36.1%和9.78 cm。经形态学观察和ITS序列分析确定该菌株为Cladosporium oxysporum。DH03作为微生物源除草剂值得进一步研究。     

小尾寒羊白介素1β全长cDNA序列克隆及生物信息学分析

本研究旨在克隆白介素1β(IL-1β)全长cDNA,为深入研究其生物学功能提供全长cDNA信息和试验材料.本试验利用前人构建的布鲁氏菌强、弱毒株感染小尾寒羊白细胞层抑制性差减杂交(SSH)cDNA文库,获得小尾寒羊IL-1β部分cDNA序列信息,利用cDNA末端快速扩增技术(RACE),克隆小尾寒羊IL-1β全长cDNA,并申请GenBank登录号KC425612.2.该cDNA全长1494 bp,含有801 bp开放阅读框(ORF),可编码266个氨基酸残基,预测其编码蛋白分子质量为30.622 ku,与林麝、牛、海豚、虎鲸的IL-1β一致性较高,亲缘关系较近.     

超高效液相色谱-串联质谱法测定黄瓜及番茄中异菌脲残留

采用分散固相萃取(QuEChERS)为样品前处理方法,建立了超高效液相色谱-串联四极杆质谱(UPLC-MS/MS)快速同时检测黄瓜及番茄中异菌脲的残留分析方法。样品经乙腈提取,C18分散固相(dSPE)净化后,应用超高效液相色谱-电喷雾串联四级杆质谱仪,多反应监测模式(MRM)检测,外标法定量,结果显示,异菌脲在黄瓜和番茄基质中的线性关系良好,在0.02~1mg/L添加水平范围内,异菌脲在黄瓜和番茄中的平均回收率分别为82.7%~91.9%和89.8%~90.5%,相对标准偏差分别为4.7%~7.7%和4.8%~7.2%,最低检出浓度(LOQ)均为0.02mg/kg。     

齿墩状内消能工的消能及压力特性

输水管道或泄洪洞常见的内消能方式为孔板和洞塞,结合明渠水流中的消能工形式提出了齿墩状内消能工,并通过物理模型试验对不同面积收缩比的齿墩状内消能工进行了研究,分析了它们的过流能力、消能率、压强沿程变化及脉动压强特性.结果表明:齿墩状内消能工的过流能力主要是由消能工的体型及尺寸决定的,其面积收缩比越大,消能率越低,过流能力就越强;齿墩状内消能工的时均压强在收缩段骤降,在其后部逐渐上升,而后恢复至稳定,其恢复长度基本相同;齿墩状内消能工的脉动压强最大点均出现在收缩段后1倍圆管直径范围内,随后迅速减小,逐渐趋于平稳;面积收缩比为0.471 2的齿墩状消能工的脉动强度最小,因而其抗空化性能优于其他情况,且脉动压强最大点的压强概率密度分布接近正态分布.