稳定性核素测定大鼠小肠蛋白质合成

目的：建立稳定性核素（[L-^15N]亮氨酸）测定大鼠小肠蛋白质合成率的方法。方法：分别测定静脉注射相同剂量[L-^15N]亮氨酸不同时相的大鼠小肠^15N丰度及不同剂量[L-^15N]亮氨酸同一时相的大鼠小肠^15N丰度。结果：大鼠小肠游离氨基酸池中^15N核素丰度在注射后0．5h内呈线性上升并达高峰，维持4h后缓慢下降，小肠蛋白质中的^15N丰度0．5h至12h基本维持不变；随着注射剂量的增加，大鼠小肠蛋白质分数合成率（FSR）亦增加，当[L-^15N]亮氨酸剂量在1．0mmol／kg以上，FSR并不随施加[L15N]亮氨酸剂量的加大而增加。结论：在进行大鼠小肠蛋白质合成率测定时，一次性静脉注射的测量最佳时限为0．5h，剂量为1．0mmol／kg。     

增强子结合蛋白家族的新基因HP8的部分cDNA克隆

探讨人的增强子结合蛋白（Ｃ／ＥＢＰ）相关基因。方法以大鼠Ｃ／ＥＢＰｃＤＮＡ为探针，筛选人胎盘ｃＤＮＡ文库。结果得到一个含有１９７５碱基命名为ＨＰ８的ｃＤＮＡ克隆，其中１～６０４位碱基属编码区。经基因数据库查对未发现同源基因。该基因编码的蛋白Ｃ－末端含有亮氨酸拉链结构（ｌｅｕｃｉｎｅ ｚｉｐｐｅｒ ｓｔｒｕｃｅｕｒｅ）和Ｃ／ＥＢＰ功能区（Ｃ－末端６０个氨基酸）同源性高达９７％，而上游编码区则与Ｃ／ＥＢＰ及其已知家族同源性很低，表明该基因属Ｃ／ＥＢＰ基因家族新成员。基因组Ｓｏｕｔｈｅｒｎ杂交证实该基因为单拷贝基因。在１４种胎儿组织中显示小肠、皮肤高表达，肾上腺中度表达，肝、肺、肾、甲状腺、胆囊低表达。在３例正常成人肝组织中仅１例低表达，而在５对肝癌及癌旁肝组织中显示２例癌组织及１例癌旁组织高表达。结论以上结果提示该基因可能与细胞增殖有关。     

The genetic fine structure of nonsense suppressors in Schizosaccharomyces pombe

Summary Meiotic fine-structure maps of two efficient UGA suppressors of Schizosaccharomyces pombe which are known (sup8-e) or inferred (sup10-e) to code for two leucine tRNAs carrying the mutant anticodon U^*CA (Kohli et al. 1979, 1980a, b; Wetzel et al. 1979; Mao et al. 1981) are presented. In both cases, the recombination frequencies given by the primary site of the anticodon mutation fitwell into the map defined by the sites of a number of inactivating secondary mutations. This contrasts the corresponding situation found in the serine tRNA genes sup3 and sup9 where the anticodon site exhibits a specific marker effect which strongly increases recombination frequencies in crosses with all revertant sites, due to a decrease in the efficiency of excision repair of base-pair mismatches whenever the anticodon site is included in hybrid-DNA (Hofer et al. 1979; Munz and Leupold 1979; Thuriaux et al. 1980). A pronounced specific marker effect which leads to a several fold increase of the recombination frequencies over those expected is observed, however, at one of the secondary inactivating sites mapping in the leucine tRNA gene sup8.     

8精氨酸加压素_(4-9)肽对衰老脑突触体氨基酸掺入的影响

本文采用分离实触体体外摄取的方法研究8精氨酸加压素_(4-9)(AVP_(4-9))肽片段对青年(3月龄)和衰老(27月龄)大鼠脑的突触体氨基酸掺入和蛋白质合成的影响。结果显示,衰老时海马、额叶和颞叶皮质突触体的~3H—亮氨酸摄取明显减少(P<0.01),AVP_(4-9)肽能够促进上述脑区的突触体的亮氨酸摄取能力,以海马的突触体对AVP_(4-9)肽的反应最强,AVP_(4-9)肽对老年鼠各脑区的促进作用较青年鼠减弱,提示AVP_(4-9)肽对老年性神经精神疾病记忆损害的潜在治疗作用可能与其提高突触体的活性及增加蛋白质合成能力有关。     

Oxidative stress in plasma from maple syrup urine disease patients during treatment

Maple Syrup Urine Disease (MSUD) is an autossomal recessive metabolic disorder caused by a deficiency of branched-chain α-keto acid dehydrogenase complex activity leading to accumulation of the branched-chain amino acids leucine, isoleucine and valine and their corresponding branched-chain α-keto acids. Affected patients usually present hypoglycemia, ketoacidosis, convulsions, poor feeding, coma, psychomotor delay and mental retardation. Considering that the pathophysiology of MSUD is still poorly understood, in this study we evaluated some parameters of oxidative stress, namely thiobarbituric acid-reactive substances (TBARS), total antioxidant reactivity (TAR) and total antioxidant status (TAS) in plasma from treated MSUD patients presenting high and low plasma leucine levels. We verified a significant increase of TBARS (lipid peroxidation) and a decrease of TAR (capacity to rapidly react with free radicals) in plasma from treated MSUD patients with low and with high plasma levels of leucine compared to the control group. It was also verified that TAS (quantity of tissue antioxidants) was not altered in plasma from treated MSUD patients with low and high blood leucine levels. Finally, we found no correlation between leucine, valine and isoleucine levels with the various parameters of oxidative stress. These results are indicative that increased lipid oxidative damage and decreased antioxidant defenses occur in plasma of MSUD patients and that the accumulating branched-chain amino acids are probably not directly associated to oxidative stress in this disorder.     

Independent occurrence of I2020T mutation in the kinase domain of the leucine rich repeat kinase 2 gene in Japanese and German Parkinson's disease families

To understand the genetic origin of I2020T mutation in the kinase domain of leucine rich repeat kinase 2 (LRRK2), we investigated the original PARK8 Japanese family (Sagamihara family) and a German family (family 32), both of which were found to harbor I2020T as the causal mutation for autosomal dominant familial Parkinson's disease (PD). Microsatellite-haplotype analysis around the LRRK2 gene indicated that the mutation-carrying haplotypes of the two families were distinct from each other. This indicated that the I2020T mutation, an essential pathogenic mutation of PARK8-related PD, had occurred independently in the two PD families.     

Multimerization of the p12 domain is necessary for Mason-Pfizer monkey virus Gag assembly in vitro

Mason-Pfizer monkey virus (M-PMV) Gag protein contains a domain p12 that is unique to this virus (simian retrovirus-3) and its close relatives. The alpha-helical N-terminal half of p12, which contains a leucine zipper-like region, forms ordered structures in E. coli and the C-terminal half can form SDS-resistant oligomers in vitro. Together these properties suggest that p12 is a strong protein-protein interaction domain that facilitates Gag-Gag oligomerization. We have analyzed the oligomerization potential of a panel of p12 mutants, including versions containing substituted dimer, trimer, and tetramer leucine zippers, expressed in bacteria and in the context of the Gag precursor expressed in vitro and in cells. Purified recombinant p12 and its mutants could form various oligomers as shown by chemical cross-linking experiments. Within Gag these same mutants could assemble when overexpressed in cells. In contrast, all the mutants, including the leucine zipper mutants, were assembly defective in a cell-free system. These data highlight the importance of a region containing alternating leucines and isoleucines within p12, but also indicate that this domain's scaffold-like function is more complex than small number oligomerization.     

脾虚证大鼠各脑区和血清亮氨酸-脑啡肽的变化

目的：研究各脑区和血清亮氨酸－脑啡肽（L－EK）含量的变化,方法：成年SD大鼠32只随机分为4组,每组8只,即正常组,脾虚组,治疗组,自复组,采用放射免疫分析法,测定各组大鼠额叶皮质,下丘脑,垂体及血清L－EK的含量。结果：（1）脾虚组,自复组大鼠额叶皮质,下丘脑,垂体L－EK含量均较正常组,治疗组高,有显性差异（P＜0．01）;而血清L－EK含量均较正常组,治疗组低,有显性差异（P＜0．01）。（2）大鼠额叶皮质L－EK含量均较下丘脑,垂体L－EK含量低,有显性差异（P＜0．05）,结论：L－EK参与脾虚证的病理过程,四君子汤通过调节内源性阿片肽,发挥健脾益气作用。     

The intracellular mobility of NPY and a putative mitochondrial form of NPY in neuronal cells

Preproneuropeptide Y is a precursor peptide to mature neuropeptide Y (NPY), which is a universally expressed peptide in the central and peripheral nervous system. NPY is normally routed to endoplasmic reticulum and secretory vesicles in cells, which secrete NPY. In our previous studies, we found a functional Leucine7 to Proline7 (L7P) polymorphism in the signal peptide sequence of preproNPY. This polymorphism affects the secretion of NPY and causes multiple physiological effects in humans. The sequence of NPY mRNA contains two in frame kozak sequences that allow translation initiation to shift, and translation of two proteins. In addition to mature NPY_1–36 also a putative truncated NPY_17–36 with mitochondrial targeting signal is produced. The purpose of this study was to investigate the protein mobility of the putative mitochondrial fragment and the effect of the L7P polymorphism on the cellular level using GFP tagged constructs. The mobility was studied with fluorescence recovery after photobleaching technique in a neuronal cell line. We found that the mobility of the secretory vesicles with NPY_1–36 in cells with L7P genotype was increased in comparison to vesicle mobility in cells with the more abundant L7L genotype. The mobility in the cells with the putative mitochondrial construct was found to be very low. According to the results of the present study, the mitochondrial truncated peptide stays in the mitochondrion. It can be hypothesized that this could be one of the factors affecting energy balance of the membranes of the mitochondrion.     

Both homo and heterodimers of Marek's disease virus encoded Meq protein contribute to transformation of lymphocytes in chickens

Marek' disease virus serotype-1, also know as Gallid herpesvirus 2 (GaHV-2), elicits T-cell lymphomas in chickens. The GaHV-2 genome encodes an oncoprotein, Meq, with similarity to the Jun/Fos family of proteins. We have previously shown that Meq homodimers are not sufficient to induce lymphomas in chickens. In this study, we investigated the role of Meq heterodimers in the pathogenicity of GaHV-2 by generating a chimeric meq gene, which contains the leucine zipper region of Fos (meqFos). A recombinant virus containing the meqFos gene in place of parental meq, rMd5-MeqFos, was not capable of transforming chicken lymphocytes, indicating that heterodimerization of Meq alone is not sufficient for transformation. In addition, the recovery of the oncogenic phenotype by a recombinant virus encoding one copy each of MeqGCN (homodimer) and MeqFos (heterodimer) conclusively demonstrates that both homo and heterodimerization of Meq are required for oncogenesis.