四川自贡大山铺蜀龙动物群——简报Ⅴ 两栖类

本文对扁头中国短头鲵(新属新种) (Sinobrachyops placenticephalus gen. et sp. nov.) 的形态特征和分类位置进行简述.标本得自著名的恐龙化石产地——自贡大山铺,产出时代为中侏罗世.中国短头鲵是目前迷齿类中在地史上最年轻的一个属.它的发现使迷齿类在地球上生存时代的上限推移到中侏罗世.     

氚水在模拟水生－陆生生态系中的迁移与分布

利用同位素示踪技术研究了进入水体的ＨＴＯ向陆地的迁移。结果表明：１．进入水体的ＨＴＯ将向系统各组分转移,池水中的ＨＴＯ单调地减少,底泥及水生生物中的ＨＴＯ浓度皆在经历某一最大值后平缓地下降;２．ＨＴＯ中的而以自由水沉和结合态氚存在于水生动植物和底泥中;３．ＨＴＯ还明显地向毗邻的陆地和作物迁移,在一个半月期间,陆地系统中的总而约占水体的２４％。     

微小根毛霉感染机理研究

本文在首次报告二例肺结核、糖尿病患者合并感染肺微小根毛霉的基础上,进一步探讨免疫功能受损与微小根毛霉感染关系。本文采用不同剂量~(60)Co-γ全身辐照小鼠,然后以不同途径注射同剂量的微小根毛霉的孢囊孢子,观察动物的感染情况和感染后的真菌检出率,结果发现各种辐射剂量均在辐射后7-14日感染菌的检出率最高;各种脏器感染菌的检出率以脾脏最高(66.7—81.8％);淋巴结最低(0.0—25.0％);其他脏器的感染菌检出率也有不同程度的差异。     

植物乳杆菌谷氨酸脱羧酶催化pH范围的理性改造及高效转化生产g-氨基丁酸

γ-氨基丁酸可由谷氨酸脱羧酶(glutamate decarboxylase, GAD)催化谷氨酸一步合成,反应体系成分简单、环境友好。然而,绝大多数GAD酶催化pH偏酸性且反应范围狭小,需要加入无机盐维持最适催化环境,增加了生产附加成分。此外,随着产物γ-氨基丁酸的生成,溶液pH会逐渐上升,不利于GAD酶的持续转化。本研究首先从实验室保藏的一株高产γ-氨基丁酸的植物乳杆菌(Lactobacillus plantarum)中克隆得到谷氨酸脱羧酶LpGAD,基于酶蛋白表面电荷修饰,选择9个位点进行定点突变及组合突变,酶学性质表征结果显示三突变体LpGAD^{S24R/D88R/Y309K}在催化pH区间内酶活力整体提高,尤其拓宽了在偏中性pH 6.0下的酶活,为野生酶的1.68倍。接下来,通过分子动力学模拟解析了酶活提高的机理。此外,将Lpgad与Lpgad^{S24R/D88R/Y309K}突变基因分别在谷氨酸棒杆菌(Corynebacterium glutamicum) E01中过表达,通过优化确定了摇瓶最适转化条件为反应温度40 ℃,菌体量OD₆₀₀=20,底物L-谷氨酸100.0 g/L,5-磷酸吡哆醛添加量为100 μmol/L。5 L发酵罐中,不调节pH,通过分批投料底物L-谷氨酸,γ-氨基丁酸产量高达402.8 g/L,较对照菌株提高了1.63倍。本研究成功拓宽了LpGAD的pH催化范围及酶活,提高了γ氨基丁酸的转化效率,为实现其规模化工业生产奠定了基础。     

Active expression of Gγ globin gene on chromosome 11 with Yunnanese (Ayγδβ)~0-thalasseinia deletion in MEL cells

A permanent lymphocyte cell line of a heterozygote with Yunnanese (Aγδβ)0-thalassemia deletion, associated with an increased production of Cry globin in adult, was founded using Epstein-Barr virus transformation. The hybrids of the lymphocyte cell and mouse erythroleukemia cell (MEL) were achieved and the hybrids containing human chromosome 11 were selected with the monoclonal antibody 53/6. The subclones containing only either the normal or the abnormal human chromosome 11 were separated and the expression of the human globin genes was studied. Expression of the β-globin gene, but not the Cγ and Aγ, was observed in the hybrids containing only the normal human chromosome 11, while active expression of the Cγ globin gene was observed in the hybrids containing only the abnormal human chromosome 11. These results have confirmed that the DNA deletion in the β-globin gene cluster is the cause of persistent active expression of the Cγ globin gene in the Yunnanese mutant.     

四川自贡大山铺蜀龙动物群——简报Ⅲ.蜥脚类

本文记述了中侏罗世蜥脚类一新属种——巴山酋龙(Datousaurus bashanensts gen. et sp. nov.)对李氏蜀龙(Shunosaurus lii)的特征进行了补充,讨论了它们在蜥脚类进化过程中的位置。     

Metabolic engineering of Clostridium tyrobutyricum for enhanced butyric acid production with high butyrate/acetate ratio

Applied Microbiology and Biotechnology - Butyric acid fermentation by Clostridium couples with the synthesis of acetic acid. But the presence of acetic acid reduces butyric acid yield and increases...     

Activation of the bitter taste sensor TRPM5 prevents high salt-induced cardiovascular dysfunction

Science China Life Sciences - High salt intake is a known risk factor of cardiovascular diseases. Our recent study demonstrated that long-term high salt intake impairs transient receptor potential...