Reversal of Fv-1 host range by in vitro restriction endonuclease fragment exchange between molecular clones of N-tropic and B-tropic murine leukemia virus genomes.

We molecularly cloned unintegrated viral DNA of the BALB/c endogenous N-tropic and B-tropic murine leukemia retroviruses and in vitro passaged N-tropic Gross (passage A) murine leukemia retroviruses. Recombinant genomes were constructed in vitro by exchanging homologous restriction enzyme fragments from N- or B-tropic parents and subsequent recloning. Infectious virus was recovered after transfection of these recombinant genomes into NIH-3T3 cells and cocultivation with the Fv-1 nonrestrictive SC-1 cells. XC plaque assays of recombinant virus progeny on Fv-ln and Fv-lb cells indicated that the Fv-l host range was determined by sequences located between the BamHI site in the p30 region of the gag gene (1.6 kilobase pairs from the left end of the map) and the HindIII site located in the pol gene (2.9 kilobase pairs from the left end of the map).     

九种罕见的人类染色体异常核型报告

ReportonNineRareSpeciesofHumanChromosomalAbnormalKaryotypesHanWeitian;QuOu;YuPing;JiangMiao(LiaoningResearchInstituteofFamilyPlanning,Shenyang110031)自1983年以来,我们对数千例不育及胚胎丢失等生殖异常患者进行细胞遗传学研究,发现大量异常染色体核型,而且异常种类繁多,已报道世界首报人类异常核型25种[1]。最近,在不良妊娠患者中又发现9种异常核型,经湖南医科大学医学细胞遗传学国家培训中心鉴定,为世界首次报道．现报告如下。1病例摘要及核型例1男,30岁,表型及智力正常,其妻子妊娠两次,均在无任何诱因情…     

Compartmentalization of SHC, GRB2 and mSOS, and hyperphosphorylation of Raf-1 by EGF but not insulin in liver parenchyma.

Rat liver parenchyma harbors equal numbers of epidermal growth factor (EGF) and insulin receptors. Following administration of a saturating dose of EGF (10 micrograms/100 g body weight), there was a rapid (t1/2 approximately 1.1 min) internalization of receptor coincident with its tyrosine phosphorylation at residue 1173 and receptor recruitment of the adaptor protein SHC, its tyrosine phosphorylation and its association with GRB2 and the Ras guanine nucleotide exchange factor, mSOS, largely in endosomes. This led to a cytosolic pool of a complex of tyrosine-phosphorylated SHC, GRB2 and mSOS. It was demonstrated that these constituents were linked to Ras activation by the characteristic decrease in Raf-1 mobility on SDS-PAGE, which was maintained for 60 min after a single bolus of administered EGF. While insulin administration (15 micrograms/100 g body weight) led to insulin receptor beta-subunit tyrosine phosphorylation and internalization, there was little detectable tyrosine phosphorylation of SHC, recruitment of GRB2, association of a complex with mSOS or any detectable change in the mobility of Raf-1. Therefore, in normal physiological target cells in vivo, distinct signaling pathways are realized after EGF or insulin receptor activation, with regulation of this specificity most probably occurring at the locus of the endosome.     

Lac host-trees and the balance of agroecosystems in south Yunnan,China

The importance of spontaneous lac host-trees for preserving the fragile agroecosystem of the main lac producing areas of China, located in the tropical part of Yunnan province, is analyzed. In upland fields, the fire-resistant vegetation consists mainly of these trees. Farmers deliberately preserve young sprouts during the cultivation cycle. This benefits both soil fertility and lac production. Host-trees, mainly Dalbergia and Ficus, form a range of multipurpose trees which although limited to some ten species allows maximum use of the heterogeneities of the village territory. Finally, lac host-trees are associated with some environmental values important to farmers. This circumstance contributes to the sustainability of lac host-tree agroforestry in spite of current problems in the lac market.     

Expression and characterization of virus-like particles containing rubella virus structural proteins.

Rubella virus (RV) virions contain two envelope glycoproteins (E1 and E2) and a capsid protein (C). Noninfectious RV-like particles (VLPs) containing three structural proteins were expressed in a BHK cell line (BHK-24S) by using an inducible promoter. These VLPs were found to resemble RV virons in terms of their size, their morphology, and some biological activities. In immunoblotting studies, VLPs were found to bind similarly to native RV virions with 10 of a panel of 12 RV-specific murine monoclonal antibodies. Immunization of mice with VLPs induced specific antibody responses against RV structural proteins as well as virus-neutralizing and hemagglutination-inhibiting antibodies. After immunization of mice with VLPs, in vitro challenge of isolated lymphocytes with inactivated RV and individual RV structural proteins stimulated proliferation. Our data suggest the possibility of using VLPs as immunogens for serodiagnostic assays and RV vaccines.     

Effects of Temperature,Shoot Age,and Medium on Gall Induction by Subanguina picridis in Vitro

The influence of temperature, shoot age, and medium on gall induction by Subanguina picridis on Russian knapweed (Acroptilon repens) was examined in vitro. The optimal temperature for gall formation was 20 C. Gall induction was delayed as the temperature decreased, and decreased as shoot age increased. Bud primordia (0-day-old shoots and 5-day-old shoots) with an average length of 4.2 mm and 7.9 mm were the most suitable tissues for nematode development and gall formation. Gall formation was more effective on B5G medium than on MSG. Young shoots under slow growth were most suitable for mass rearing of S. picridis.     

Depression of Neuronal Protein Synthesis Initiation by Protein Tyrosine Kinase Inhibitors

Abstract— Growth factors stimulate cellular protein synthesis, but the intracellular signaling mechanisms that regulate initiation of mRNA translation in neurons have not been clarified. A rate-limiting step in the initiation of protein synthesis is the formation of the ternary complex among GTP, eukaryotic initiation factor 2 (elF-2), and the initiator tRNA. Here we report that genistein, a specific tyrosine kinase inhibitor, decreases tyrosine kinase activity and the content of phosphotyrosine proteins in cultured primary cortical neurons. Genistein inhibits protein synthesis by >80% in a dose-dependent manner (10–80 μg/ml) and concurrently decreases ternary complex formation by 60%. At the doses investigated, genistein depresses tyrosine kinase activity and concomitantly stimulates PKC activity. We propose that a protein tyrosine kinase participates in the initiation of protein synthesis in neurons, by affecting the activity of elF-2 directly or through a protein kinase cascade.     

Phytopathogenic bacteria utilize host glucose as a signal to stimulate virulence through LuxR homologues

Chemical signal-mediated biological communication is common within bacteria and between bacteria and their hosts. Many plant-associated bacteria respond to unknown plant compounds to regulate bacterial gene expression. However, the nature of the plant compounds that mediate such interkingdom communication and the underlying mechanisms remain poorly characterized. Xanthomonas campestris pv. campestris (Xcc) causes black rot disease on brassica vegetables. Xcc contains an orphan LuxR regulator (XccR) which senses a plant signal that was validated to be glucose by HPLC-MS. The glucose concentration increases in apoplast fluid after Xcc infection, which is caused by the enhanced activity of plant sugar transporters translocating sugar and cell-wall invertases releasing glucose from sucrose. XccR recruits glucose, but not fructose, sucrose, glucose 6-phosphate, and UDP-glucose, to activate pip expression. Deletion of the bacterial glucose transporter gene sglT impaired pathogen virulence and pip expression. Structural prediction showed that the N-terminal domain of XccR forms an alternative pocket neighbouring the AHL-binding pocket for glucose docking. Substitution of three residues affecting structural stability abolished the ability of XccR to bind to the luxXc box in the pip promoter. Several other XccR homologues from plant-associated bacteria can also form stable complexes with glucose, indicating that glucose may function as a common signal molecule for pathogen–plant interactions. The conservation of a glucose/XccR/pip-like system in plant-associated bacteria suggests that some phytopathogens have evolved the ability to utilize host compounds as virulence signals, indicating that LuxRs mediate an interkingdom signalling circuit.