锌缺乏对海马锌离子及锌转运蛋白ZnT4表达的影响

目的探讨锌缺乏对小鼠大脑海马锌离子和锌转运蛋白4（Zinc Transporter 4,ZnT4）表达的影响.方法建立锌缺乏动物模型,给断乳后的CD-1小鼠分别喂养缺锌饲料和正常饲料,5周后取大脑海马组织,应用锌金属自显影技术、免疫组织化学技术和Western blotting技术分别进行两组海马锌离子含量和ZnT4表...     

Prolonged vibration of cutaneous artery: Absence of persisting aftereffects

Summary 1–3 h after prolonged (3–16 h) vibration (120 Hz, 0.2–0.3 mm amplitude) of rings of canine saphenous arteries there was no significant change in the contractile response to electrical stimulation, exogenous norepinephrine or of neuronal uptake of tritium labeled norepinephrine. These results did not provide evidence for persistent aftereffects of prolonged vibration.Acknowledgments. Supported in part by NIH grant HL 05883 and the Swedish Work Environmental Fund.     

转运葡萄糖苷类化合物的Caco-2细胞模型建立

建立转运葡萄糖苷类化合物的Caco-2细胞模型,为葡萄糖及葡萄糖苷类化合物肠道吸收研究提供基础。通过对Caco-2细胞最适培养基的选择、单层致密性的测定、单层通透性和细胞两侧碱性磷酸酶活性比的测定、单层亚显微结构的观察、细胞葡萄糖转运蛋白SGLT1和GLUT2的mRNA及蛋白表达水平的分析,建立可靠的细胞模型。研究表明:Caco-2细胞的最适培养基为添加体积分数15%血清的DMEM低糖培养基;Caco-2细胞在14～17d的跨膜电阻趋于稳定,苯酚红的表观渗透系数达到0.49×10-6~0.51×10-6cm·s-1,微绒毛分化成熟,细胞两侧碱性磷酸酶比值达到2.0以上。葡萄糖转运载体SGLT1的mRNA表达在14d时显著高于17d和21d,葡萄糖转运载体SGLT1和GLUT2的蛋白表达在14、17、21d无显著差异(P<0.05)。Caco-2细胞培养14～17d即可建立可靠的肠细胞吸收模型,用于葡萄糖及葡萄糖苷类化合物吸收的体外研究。     

Cloning and functional analysis of the sequences flanking mini-Tn5 in the magnetosome-deleted mutant NM21 of Magnetospirillum gryphiswaldense MSR-1

A magnetosome-deleted mutant NM21 of Magnetospirillum gryphiswaldense MSR-1 was generated by mini-Tn5 lacZ2 transposon mutagenesis, and a 3073-bp fragment flanking mini-Tn5 lacZ2 in NM21 was cloned by Anchored PCR. Sequencing analysis showed that this fragment involved three putative ORFs; the mini-Tn5 lacZ2 was inserted into ORF1. Functional complementary test indicated that the 3073-bp fragment was required for biosynthesis of magnetosomes in M. gryphiswaldense MSR-1. The majority of proteins, which had homology with the protein encoded by ORF1, were the cation transporter. Transmembrane domain analysis showed that the protein encoded by ORF1 contained four transmembrane domains. It may be a transmembrane protein. The protein encoded by ORF1 contained two putative conserved domains: COG0053 and PRK09509. The MMT1 and FieF, containing conserved domains COG0053 and PRK09509 too, were Fe²⁺ transporter (cation diffusion facilitator superfamily). It was suggested that the protein encoded by ORF1 might take part in the magnetosomes biosynthesis as Fe²⁺ transporter. Supported by National Natural Science Foundation of China (Grant No. 30570023) and Scientific Research Project of Huaibei City, Anhui Province (Grant No. 070114)     

水稻阶段性返白突变体的鉴定和候选基因分析

从粳稻品种中花11 的后代中发现了一个叶色突变体sgra, 该突变体幼苗期叶色正常, 而6~8 叶期以后新生叶白化, 随后白化叶转绿. 突变体的遗传分析表明, 该突变体表型受1 对隐性核基因控制. 利用籼粳杂交F2群体对突变位点进行了基因定位, 将其定位于水稻第11 染色体的2 个标记ID343-11 和PSM415 之间, 遗传距离分别为0.9 和1.0 cM. 随后, 利用已公布的水稻序列和SSR标记, 在两标记间发展了9 对新的标记, 进一步将SGRA基因定位在IDM-2 和RM26739 之间, 物理距离约为17.6 kb. 对野生型和突变体候选区段基因组DNA 测序分析表明, 候选基因编码一个ABC 转运蛋白.     

甲酸转运蛋白FocA的分子结构揭示其是以五聚体形式存在的一个通道蛋白

FocA是甲酸-亚硝酸转运蛋白家族(FNT)的一个代表性成员,在细菌、古细菌、真菌、藻类和寄生虫中负责短链酸的转运。甲酸-亚硝酸转运蛋白家族中所有成员蛋白的分子结构和转运机制都是未知的。在这项工作中,我们解析了大肠杆菌中FocA蛋白的三维晶体结构,分辨率高达2.25。这个晶体结构显示,FocA构成了一个对称的五聚体,其中每个单体包含6个跨膜螺旋片段。而且,尽管FocA与水通道蛋白Aquaporin在序列上缺乏同源性,但它们的单体整体结构却异常相似。这些结果意味着FocA应该是一个跨膜通道蛋白,而不是此前认为的转运蛋白。进一步的结构分析识别出了通道中的重要氨基酸残基,明确了通道路径,并揭示了两个对通道起收紧作用的位点。但是与水通道蛋白Aqua-porin不同,FocA对水分子并没有通透性,却允许甲酸通过。在结构生物学和生物化学方面的进一步研究为阐明FocA的通道活性机理提供了重要线索。     

脯氨酸与植物抗渗透胁迫基因工程改良研究进展

综述了脯氨酸的生理功能、生物合成途径、脯氨酸在植物体内的分布和脯氨酸运输蛋白基因、脯氨酸的抗渗透胁迫机制以及植物抗渗透胁迫基因工程改良等方面的研究进展．     

α1-Adrenergic stimulation of ketogenesis and fatty acid oxidation is associated with inhibition of lipogenesis in rat hepatocytes

Summary The effect of norepinephrine on fatty acid synthesis (³H₂O incorporation into fatty acids), on fatty acid oxidation to CO₂ and on ketogenesis was studied in isolated hepatocytes of fed rats. After incubation with norepinephrine (50 M), lipogenesis was lower (5.7±1.1 nmoles³H₂O incorporated into fatty acids/mg dry weight/30 min) than in controls (7.5±1.7; n=6, p<0.02). In contrast, (1-¹⁴C) palmitate conversion into total ketone bodies was increased to 10.9±1.8 nmoles/mg/30 min with norepinephrine, vs 8.5±1.6 in controls (p<0.05), and more (1-¹⁴C) palmitate was converted to¹⁴CO₂ with norepinephrine than in controls (1.48±0.10 nmoles/mg/30 min vs 1.06±0.11, p<0.05). The inhibitory effect of norepinephrine on lipogenesis was abolished by addition of the ₁-receptor blocker prazosin, but not by ₂ or -blockers. The results demonstrate that the ketogenic effect of norepinephrine is coupled with an inhibitory effect on lipogenesis which may be explained by diminished activity of acetyl-CoA carboxylase, diminished formation of malonyl-CoA and decreased activity of carnitine palmitoyl transferase I.     

Depletion of hypothalamic norepinephrine reduces the fever induced by polyriboinosinic acid: polyribocytidylic acid (Poly I:Poly C) in rats

Summary Administration of either Poly I:Poly C (0.05–0.50 g) or norepinephrine (2–8 g) into the anterior hypothalamic area produced a dose-related fever in rats. The fever induced by Poly I:Poly C was attenuated after selective depletion of norepinephrine in the hypothalamus. However, selective depletion of hypothalamic norepinephrine did not affect the fever induced by intrahypothalamic norepinephrine. The data indicate that Poly I:Poly C may act to induce fever through the endogenous release of norepinephrine from the rat's hypothalamus.This work was supported by grants from the National Science Council (Taipei, Republic of China).     

锌转运体家族的研究进展

锌是所有生物体必需的微量元素,锌转运体(ZnT)的发现深化了对锌在细胞和分子水平的认识.ZnT家族主要参与锌的外排和锌在细胞内的区室化,以达到降低细胞内锌浓度的目的,进而为细胞内各种生理生化反应的进行提供一种保障机制.本文综述了近年来国内外关于ZnT家族成员的结构特征和基因克隆的研究现状以及在分布和功能方面的研究报道,并结合当前实际就ZnT家族成员在相关疾病方面的研究进行了分析.