Post-translational modification of proteins by arginine and lysine following crush injury and during regeneration of rat sciatic nerves

Following crush injury to rat sciatic nerves, a crude fraction of the 150,000 g supernatant can post-translationally incorporate [3H]Arg and [3H]Lys into endogenous proteins in amounts approximately 10 times uninjured control nerves. These increases occur in the proximal nerve stump within 2 h of injury and 2 weeks later in a distal segment of nerve containing the tips of the regenerating axons. In the present experiments, the endogenous nerve proteins modified by Arg or Lys in these nerve segments have been identified using two-dimensional polyacrylamide gel electrophoresis. The fraction used to assay for protein modification, the void volume of a Sephacryl S-300 column, was found to contain only a few proteins visible by Coomassie blue staining, one of which is likely to be albumin (68 kDa, pI 6.4). While this protein was modified by both Arg and Lys, the majority of label was found in areas not showing Coomassie blue staining. This indicates that of the many potential targets of post-translational arginylation and lysylation, most are proteins of relatively low abundance. A variety of proteins were modified by Arg or Lys alone while others were modified by both Arg and Lys. A high molecular weight protein (175 kDa, pI 9.0) was modified only by Lys and only at 2 h post crush. Of a variety of modified proteins of approximately 17 kDa one (pI 6.3) was modified by both Arg and Lys and at both time points, while another (pI 9.0) was modified at both time points, but only by Lys. The results show that Arg and Lys can be added post-translationally to a large number of low abundance, soluble sciatic nerve proteins, and that some of those proteins are modified only by Arg or Lys while others are modified by both Arg and Lys. Also, the modification of certain proteins appears to be associated specifically with the immediate response of a nerve to injury (e.g. 88 kDa, pI 7.1) while others are associated with the regenerative period (e.g. 56 kDa, pI 7.4).     

Posttranslational modification of nerve proteins by amino acids

Both axonal and glial components of nerve are capable of carrying out reactions in which Arg, Lys, Leu, Pro, Val, AJa and Ser can be covalently linked to endogenous proteins in reactions which require tRNA but occur in the absence of ribosomes and ribosomal RNA. These posttranslational protein modifications appear to play important roles in nerve regeneration since they are increased more than 10-fold within 2 h of a crush injury in nerves which are capable of regeneration, but are not activated in nerves not capable of regrowth following injury. The regulation of the modification of proteins by Arg and Lys in vivo appears to be the function of separate peptides. The exogenous application of serine protease inhibitors (but not other protease inhibitors) mimics the effect of the endogenous peptides, suggesting that the endogenous regulators have serine protease inhibitory activity. The targets for modification are proteins of low abundance and thus far have been identified only in terms of their molecular weights and isoelectric points. The site of addition of Arg, but not the other amino acids, to target proteins is to the amino terminus. The addition of Arg to an amino terminus is likely to be involved in the ubiquitin mediated proteolysis of the modified protein. One of the most unusual findings in these series of experiments is that in regenerating sciatic nerves, amino acid modified proteins aggregate to form complexes of greater than 2 × 106 Da. The significance of this finding is not known. But we speculate that the aggregate may result from the assembly of an insoluble functional unit of the cell from soluble precursor proteins, and that the trigger for their assembly is amino acid modification.     

重组人肝细胞生长因子基因的克隆

用ＲＴ－ＰＣＲ技术从人胎盘组织内成功地扩增全长肝细胞生长因子（ＨＧＦ）ｃＤＮＡ基因（２ １８４ｂｐ）,并将其克隆至ｐＧＥＭ－Ｔ载体,经限制性核酸内切酶ＮｄｅⅠ,ＢｇｌⅡ,ＨｉｎｄⅢ,ＢａｍＨⅠ和ＸｈｏⅠ的酶谱分析和ＤＮＡ测序分析证实。再将其亚克隆至逆病毒载体ｐＬＮＬ－ＸＨＣ,可进一步用于基因表达和基因治疗的研究。     

医古文求疵四则

古人用字行文,决非凭空虚构;遣词造句,十分精确.反复阅读,才能体味其中之妙.本义、引申,需谋全篇,方能准确理解.笔者不揣愚陋,就医古文规划教材的注释提出求疵四则,以便投石问路.     

Studies of β-lactamase production in ampicillin resistant Haemophilus influenzae

In 1972, HaelnOPhilus influenzae (HI) was firstlydiscovend being resistant against alnpicillin by producing5-lac~e, since then, studies on the rests~ mechamsms and the moleCular basis of 5-lactalnaSe Pwhctionhave been increasing year by yeax abroadll]. In 1978,Bryan et .l[2] first reported sabins of HI Producing 0-lactamaSe, which was mediated by plaaed, from then on,many stUdies foeused on 3-lactamase encoded by PlaSnddin HI and its relation with ampicillin resisboce. In ourco~, few st…     

Role of Th1/Th2 cells activation in chronic hepatitis B virus infection

Clonal analysis of mndne T cells has led to the idenuncation of Z typeS of Th cells, Thl and on. Thl cells,chacterized by secreting interferon-y (Iap-Y), interleukin-2 (IL2) and tumor necrosis factor-5 (TNF-3), involved Principally in cell-mediated ~ity and play acrucial role in defending the host against intracellularPathogens such as a Vallety of yi~es. ThZ cells,secreting IL4, ms, IL-6 and ilo, mostly regulateh~ immune responSe, and may oafs Paxtial PIDtection against extracellula…     

奥曲肽治疗肝硬变食管静脉曲张破裂出血

0　引言　我院 1996 - 0 6 / 1998- 0 7用奥曲肽治疗肝硬变食管静脉曲张破裂出血 19例 ,并与垂体后叶素作了对照 .1　对象和方法1.1　对象　经内镜证实食管静脉曲张破裂出血 37例 ;男 32例 ,女 5例 ;年龄 42～ 6 9岁 .肝炎后肝硬变 32例 ,乙醇性肝硬变 3例 ,血吸虫性肝硬变 2例 .按就诊顺序随机分为治疗组19例 ,对照 18例 .估计出血量 :治疗组 (146 3.6± 375 .8) m L;对照组 (144 9.5± 36 8.4) m L .出血至治疗间隔时间 :治疗组(11.6± 3.5 ) h;对照组 (11.2± 3.6 ) h.两组的年龄、性别、肝功 Child分级、食管静脉曲张程度、出血量、出…     

药物诱导狗Ⅰ型糖尿病的研究

To evaluate the efficiency and toxic and side effect of the combined chemical inducer for Type I diabetes mellitus, Type I diabetes in 9 adult dogs were induced with alloxan(50 mg.kg-1) and streptozotocin (30 mg.kg-1) with vein injection. After 7-14 days, the blood glucose of 5 male dogs was kept on high levels [mean value was (22.7 +/- 3.2) mmol.L-1], exogenous insulin was (21.4 +/- 2.4) U.day-1. Three female dogs died in 7 days after they had been injected with the combined inducers. Alloxan-streptozotocin combination administration reduced the dosage of each drug, and decreased the toxic and side effect of each drug. The results suggest that this method has a high rate of success to induce Type I diabetes male dogs.     

Human papillomaviruses and papillomatosis lesions of the female lower genital tract

Objective: The objective of this study was to determine whether human papillomavirus (HPV) infections are involved in the development of papillomatosis lesions of the lower female genital tract.Methods: A total of 616 biopsy specimens of genital papillomatous lesions (307 nodular and 309 papular types) from 598 patients were anaylyzed for the presence of HPV DNA sequences by polymerase chain reaction (PCR). These specimens were also examined by histopathological assessment for characteristic HPV-associated cytological changes, by immunohistochemical staining for HPV-associated antigen, and by electron microscopy for the presence of virions.Results: HPV DNA sequences were found in 97.9% (140 of 143 cases) and 1.1% (1 of 91 cases) of the nodular and papular papillomatosis cases tested, respectively. In 18 patients who had both types of papillomatosis lesions, HPV DNA was invariably found only in nodular tissues. HPV-associated antigen, koilocytosis, and virions were found in 53.6% (98 of 183 cases), 70.5% (129 of 183 cases), and 5.9% (5 of 85 cases) of nodular papillomatosis lesions tested, respectively.Conclusions: These data suggest that nodular papillomatosis was closely associated with HPV infection, but that papular papillomatosis of the lower female genital tract may have an etiology other than HPV infection.