Molecular and functional characterization of the first nucleobase transporter gene from African trypanosomes

African trypanosomes are unable to synthesize purines and depend upon purine nucleoside and nucleobase transporters to salvage these compounds from their hosts. To understand the crucial role of purine salvage in the survival of these parasites, a central objective is to identify and characterize all of the purine permeases that mediate uptake of these essential nutrients. We have cloned and functionally expressed in a purine nucleobase transport deficient strain of Saccharomyces cerevisiae a novel nucleobase transporter gene, TbNT8.1, from Trypanosoma brucei. The permease encoded by this gene mediates the uptake of hypoxanthine, adenine, guanine, and xanthine with Kms in the low micromolar range. The TbNT8.1 protein is a member of the equilibrative nucleoside transporter (ENT) family of permeases that occur in organisms as diverse as protozoa and mammals. TbNT8.1 is distinct from other ENT permeases that have been identified in trypanosomes in utilizing multiple purine nucleobases, rather than purine nucleosides, as substrates and is hence the first bona fide nucleobase permease identified in these parasites. Furthermore, unlike the mRNAs for other purine transporters, TbNT8.1 mRNA is significantly more abundant in insect stage procyclic forms than in mammalian stage bloodstream forms, and the TbNT8.1 permease thus may represent a major route for purine nucleobase uptake in procyclic trypanosomes.     

Effect of chromosome loss on the leavening ability of Saccharomyces cerevisiae in dough

Summary To investigate the leavening ability of yeast in dough, chromosome loss was induced by benomyl treatment in YOY1037, a diploid between a baking strain and a laboratory strain, and its effect on the leavening ability was studied. When benomyl-treated cells were spread on plates with a dye indicator for ploidy, about 20% of the visible colonies were stained dark blue or dark purple; the rest stained pale blue, similar to the diploid YOY1037. Strains showing the MAT phenotype, and non-galactose fermenting strains, apparently having lost particular chromosomes, were observed only in those with darkcoloured colonies. Strains with dark-coloured colonies showed a wider range of leavening ability than did those with pale-coloured colonies.     

Epidemiological study of pathogenic fungi in China: 1986 and 1996

目的　研究 1986年 - 1996年 ,我国致病真菌菌群的变化情况。方法　 1986年 1月 1日 - 12月 31日和 1996年 1月 1日 - 12月 31日在全国 2 5个省、市、自治区 4 0多个有代表性的单位对临床或现场确定的致病菌进行了动态研究 ,就病原菌变迁、各区动态情况和具体疾病等作了详细分析。结果　发现 10年间较易治疗的皮肤癣菌比例下降 ,而较难治疗的酵母菌和霉菌比例升高。结论　 10年间致病真菌菌群的变化较大 ,我们应根据变化情况进行相应的研究及制定出相应治疗措施     

手术前后补硒对结直肠癌患者免疫功能的影响

目的　研究手术前后服用酵母硒对结直肠癌患者免疫功能的作用。方法　1998 年3 月～1999 年3月,将我院的40 例大肠癌患者,随机分成对照组和治疗组,分别给予一般酵母和酵母硒(600μg/d) 持续2 周,观察治疗前后血硒水平、T 细胞亚群和免疫球蛋白,以及细胞因子αTNF 的变化。结果　补硒后,血硒由0 .79 ±0 .17μmol/L上升到0 .99 ±0 .23μmol/L,P< 0 .05 ;CD4 由24 .09 ±4 .10 % 上升到27 .95 ±4 .91 % ,CD8 由20 .18 ±2 .48 % 上升到23 .09 ±4 .47 % ,P< 0 .05 ;血清中Ig M 从83 .7 ±22 .37mg % 上升到103 .69 ±35 .49mg % ,P< 0 .05 。结论　手术前后给大肠癌患者服用酵母硒可明显地提高其血硒水平,改善机体的免疫功能并增强抗肿瘤的能力。     

山区农村散居80岁及以上老年人营养调查

对象与方法：在沂蒙山区对４个乡镇的散居高龄老人１２１人进行营养调查（男５５,女６６）,年龄最高男９６岁,女９２岁;最低男女均为８０岁。以称重法与五日询问回忆法相结合,进行四季动态的膳食调查。结果：其膳食构成以谷类（占总重量６１％～７１％）及蔬菜（１２％～１６％）为主,配有少量豆类（１．８％～４．６％）与动物性食品（６．２％～１２．０％）。按中国营养学会８０岁以上老人ＲＤＡ计算,四季能量摄入男性达到ＲＤＡ的８１％～９１％,女性达到７５％～８４％,蛋白质男性仅达到６７％～７５％,女性５５％～６７％,动物和豆类蛋白质来源不足,低于蛋白质总量的３０％～５０％。钙摄入量只有ＲＤＡ的２０％左右,锌、硒、维生素Ａ、Ｂ１、Ｂ２、Ｃ均明显不足。三大营养素所占能量比例合理,脂肪来源以植物油为主,符合老年人营养要求。营养缺乏病检查发现有维生素不足症状,如皮肤干燥鳞皮占４．１％,口角湿白厚２８．９％,舌腥红２２．３％,味蕾肥大８１．０％,膝反射消失１２．４％等。临界高血压患病率为１６．１％,高血压患病率１４．３％。生化检查：血红蛋白检测１１４人,低于１２０ｇ／Ｌ者１６．７％;血糖检测１１６人,高于正常的占６．９％,低于正常的占４７?     

铬酵母中铬的含量测定

目的 研究铬酵母中铬的含量测定方法。方法 采用氧化－光度法。结果 铬的平均回收率及相对标准偏差分别为１００．３％、２．７％（ｎ＝５）。结论 本方法可用于测定铬酵母中铬的含量,方法简便,易行。     

Bacterial β-lactamase is efficiently secreted in Saccharomyces cerevisiae under control of the invertase signal sequence

Summary The enzyme -lactamase, a secretory protein that is located in the Escherichia coli periplasmic space, can be highly expressed in Saccharomyces cerevisiae. Although the protein can cross eukaryotic membranes, it is only inefficiently secreted by yeast. To determine whether the lack of secretion in yeast is due to the nature of the bacterial signal sequence, it was replaced with the signal peptide of yeast invertase. The presence of the invertase signal peptide led to -lactamase secretion of up to 75%. The results indicate that the bacterial signal peptide is not functional in yeast, although cleavage can take place at the authentic processing site. The mature enzyme does not interfere with the yeast secretion pathway.     

不同剂量重组(酵母)乙肝疫苗对小鼠细胞免疫应答的研究

目的：探索不同剂量重组(酵母)乙肝疫苗对小鼠细胞免疫调节作用。方法：将HBsAg免疫Balb／C小鼠一周后取淋巴结制备淋巴细胞悬液，经HBsAg刺激培养48h后检测其诱导产生的IL-2、IFN-γ的水平，另一份细胞同样经HBsAg刺激培养56h后，用氚-胸腺嘧啶核苷(^3H-TdR)标记16h后检测T细胞增殖的水平。用不同剂量HBsAg免疫小鼠后，检测血清中抗HBsIgG2a的水平。结果：中、高剂量组小鼠产生的IL-2、IFN-γ、抗HBsIgG2a以及T细胞增殖的水平显著高于低剂量组和对照组。结论：一定剂量的重组(酵母)乙肝疫苗可上调小鼠的细胞免疫功能。     

基因转殖酵母菌培养液中生物素的高灵敏ELISA竞争测定法

目的　发展一种测定基因转殖酵母菌培养液中生物素的灵敏ELISA竞争测定法。方法　酶标板先用猪肺炎支原体包被 ,再依次用兔抗猪肺炎支原体抗血浆、羊抗兔IgG -生物素温育形成固态生物素 ,同溶液中的生物素 (标准液或试样 )竞争有限量的链霉亲和素 HRP。建立了在 5 0 - 2 0 0 0ng·L- 1 范围内生物素的标准曲线。结果　检测限为 83ng·L- 1 ,比文献报告的ELISA测生物素的最低测定浓度小 10 0 0倍。测定生物素浓度为 2 0 0、5 0 0、10 0 0ng·L- 1 的用空白培养液稀释的标准生物素试样的相对标准偏差分别是 2 4 87%、6 15 %、7 86 % ,平均回收率为 10 1 13%。在用本法测定野生酵母菌及其 6 3个基因转殖酵母菌培养液中的生物素时 ,发现 85 %以上的培养液试样中生物素浓度均得到不同程度扩增。结论　用猪肺炎支原体作包被蛋白 ,提高了ELISA结果的精确度和准确度 ,可供测定其它介质中生物素的参考     

Interaction of the C-terminal tail region of the metabotropic glutamate receptor 7 with the protein kinase C substrate PICK1

Group III metabotropic glutamate receptors (mGluRs) are highly enriched in the presynaptic terminals of glutamatergic synapses where they mediate feedback inhibition of neurotransmitter release. Here, we used the yeast two-hybrid system to identify a direct interaction of the C-terminal tail region of mGluR7 with the rat homologue of the protein kinase C substrate PICK1. This interaction is specifically mediated by the very C-terminal amino acids of the receptor and can be reconstituted in human embryonic kidney 293 cells by transfection of full-length mGluR7 and PICK1 cDNAs. Quantitative beta-galactosidase assays revealed that among the different group III mGluRs, mGluR7 is the major PICK1 binding partner although other subfamily members can also interact with PICK1. These data indicate that PDZ domain-containing proteins might contribute to the presynaptic localization of group III mGluRs.