Cellular systems for the study of the biosynthesis of polyamines and ethylene,as well as of virus multiplication

Leaves of Chinese cabbage from healthy plants or from those infected with turnip yellow mosaic virus yield protoplasts which convert methionine to protein, S-adenosylmethionine, decarboxylated S-adenosylmethionine, spermidine, spermine and 1-aminocyclopropane-1-carboxylate. The enzyme spermidine synthase is entirely cytosolic and has been purified extensively. An inhibitor of this enzyme, dicyclohexylamine, blocks spermidine synthesis in intact protoplasts, and in so doing stimulates spermine synthesis. Aminoethoxyvinylglycine blocks the conversion of S-adenosylmethionine to 1-aminocyclopropane-1-carboxylate, the precursor to ethylene, in protoplasts. This inhibitor markedly stimulates the synthesis of both spermidine and spermine. Essentially all the protoplasts obtained from new leaves of plants infected 7 days earlier are infected. On incubation, such protoplasts convert exogenous methionine to viral protein and viral spermidine whose specific radioactivity is twice that of total cell spermidine. Exogeneous spermidine is also converted to cell putrescine and viral spermidine and spermine. Normal and virus-infected cells are being studied for their content of phenolic acid amides of the polyamines.     

A method for efficient gene isolation from phage lambda gt11 libraries: use of antisera to denatured, acetone-precipitated proteins

Experience with cloning pseudorabies virus (PRV) DNA in the lambda gt11 phage vector has shown that there are special requirements for the antisera used in screening the libraries, in addition to the requirement that the antisera recognize proteins on a Western blot. Initial screening of a lambda gt11 library of sheared PRV DNA fragments in Escherichia coli for expression of PRV antigens using PRV hyperimmune antisera was unsuccessful. It was only after screening the library with antisera raised against PRV proteins eluted from sodium dodecyl sulfate (SDS)-polyacrylamide (PA) gels that positive results were obtained. These "gel-slice" antisera (GSA) were equivalent in potency to hyperimmune antisera in standard immunoassays (including ELISA, immunoprecipitation, Western blots, and neutralization of virus), but only the GSA could recognize PRV fusion proteins expressed by recombinant lambda gt11 phage. This difference was seen despite the fact that hyperimmune antisera performed satisfactorily on Western blots of denatured PRV-infected cell extracts. These results show that the efficiency of screening expression libraries in E. coli can be improved if antibodies are raised against denatured proteins.     

甲型流感病毒自然温度敏感株的宿主依赖性

用鸡胚细胞(CEC)和Madin-Darby Canine Kidney(MDCK)两个宿主细胞系统,检查甲型流感病毒各亚型不同时期流行株的温度敏感性状(ts),发现自然界存在许多宿主依赖的温度敏感性突变株(hd-ts)。它们在CEC上是ts,在MDCK上却是ts~ 。检出的hd-ts株中有些曾经过人体接种观察证明为减毒株。这表明在CEC中鉴定的ts表型与对人减毒性状密切相关。     

土壤中含EB病毒诱导物的检测

从广西壮族自治区梧州市、苍梧县、罗城县和北京市收集的土壤标本中发现有EB病毒诱导物。梧州市和苍梧县沿公路和江河两旁桐油树下的土壤标本,对EB病毒早期抗原诱导的阳性率为40～58％。在其他大戟科植物下的土壤标本中,也发现有EB病毒诱导物。对桐油树下土壤中EB病毒诱导物与鼻咽癌发生的可能关系进行了讨论。     

马立克氏病毒单克隆抗体的研究

获得了4株分泌马立克氏病毒(MDV)特异性单克隆抗体(McAb)的杂交瘤细胞:4BS10对MDV所有毒株呈阳性反应;4CN8 对MDV血清1,3型毒株发生反应;2BN90和4CN24只对MDV血清1型毒株有阳性反应。3个McAb属IgG1,1个为IgG2b,均不中和MDV,免疫扩散试验也无沉淀线。对禽白血病毒(ALV)无交叉反应。 以2BN90和辣根过氧化物酶、异硫氰酸荧光素的结合物进行直接酶联免疫吸附试验和直接荧光抗体试验,均获得成功。抗体滴度前者为1/51,200,后者为1/640。对ALV无交叉反应。     

从广州市散发性脑炎病人血清中查出雪鞋野兔病毒抗体升高

近几年来夏季,在我国南方一些省市发现一些散发性病毒性脑炎病例,主要是儿童。他们的流行性乙型脑炎抗体阴性。病因不明。 为了研究本病的病因,于1983年4月至10月,我们在广州市儿童医院收集了34例散发性脑炎病人的双份血清,15例其它病种(如百日咳、心肌炎、钩端螺旋体脑炎、多发性神经根     

流行性乙型脑炎病毒减毒株和野毒株在聚丙烯酰胺凝胶电泳上的表现

乙型脑炎病毒减毒株(2-8株)和野毒株(SA14株)在生物学性质上有明显的不同,特别是嗜神经毒力方面,2-8株已丧失了对小白鼠、马,猴等敏感动物的脑内致病力。为了探讨这些生物学性质变化的物质基础,我们开展了乙脑强、弱毒株聚丙烯酰胺凝胶     

Calcium compartments and fluxes are affected by the src gene product of Rat-1 cells transformed by temperature-sensitive Rous sarcoma virus

Total cellular calcium content (determined by atomic absorption spectrometry) of Rat-1 cells transformed by temperature-sensitive Rous sarcoma virus decreases with cell density, but is found not significantly different at permissive and at non-permissive temperature. Kinetic analysis of 45Ca efflux from preloaded cells exhibits three separable pools of exchangeable calcium. The ratio of pool size of the fast-exchanging Ca-compartment (bound to cell surface) to pool size of the intermediate Ca-compartment (cytoplasmic) was found to decrease from 2.5 to 1.3 upon shift from non-permissive to permissive temperature. The slowly exchanging Ca-pool (presumably mitochondrial) did not change significantly upon temperature shift. These and further data demonstrate a close correlation between distribution of cellular Ca among different cellular compartments and characteristics of cellular proliferation, both attributable to the function(s) of a single oncogene.