Quantitation of aberrant interlocus T-cell receptor rearrangements in mouse thymocytes and the effect of the herbicide 2,4-dichlorophenoxyacetic acid

Small studies in human populations have suggested a correlation between the frequency of errors in antigen receptor gene assembly and lymphoid malignancy risk. In particular, agricultural workers exposed to pesticides have both an increased risk for lymphoma and an increased frequency of errors in antigen receptor gene assembly. In order to further investigate the potential of such errors to serve as a mechanistically based biomarker of lymphoid cancer risk, we have developed a sensitive PCR assay for quantifying errors of V(D)J recombination in the thymocytes of mice. This assay measures interlocus rearrangements between two T-cell receptor loci, V-gamma and J-beta, located on chromosomes 13 and 6, respectively. The baseline frequency in four strains of mice was determined at several ages (2-8 weeks of age) and was found to be stable at approximately 1.5 x 10(-5) per thymocyte. Strain AKR, which has a high susceptibility to T-cell lymphomas, did not show an elevated frequency of aberrant V(D)J events. We used this assay to examine the effects of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) on the frequency of these events. Female B6C3F1 mice, 27 days of age, were exposed to 2,4-D by gavage at doses of 0, 3, 10, 30, and 100 mg/kg/day for 4 successive days and sacrificed on day 5. Thymus DNA was isolated and examined for illegitimate V(D)J recombination-mediated gene rearrangements. In addition, pregnant mice were exposed to 2,4-D and thymocytes from the offspring examined at 2 weeks of age. No significant increase in aberrant V(D)J rearrangements was found, indicating that under these conditions 2,4-D does not appear to effect this important mechanism of carcinogenesis.     

Unblocking of meiotic crossing-over between the silent mating-type cassettes of fission yeast,conditioned by the recessive,pleiotropic mutant rik1

Summary The mating-type region of Schizosaccharomyces pombe consists of three subloci: the expressed cassette at mat1, and the silent cassettes at mat2-P and mat3-M. Previous work has shown that the genetically inert spacer region of 15 kb between mat2 and mat3 is completely devoid of meiotic recombination. This crossover blockage is lifted in the recessive mutant rik1. Other properties such as mating-type switching, sporulation efficiency and spore viability are also affected in this pleiotropic mutant. Presumably the wild-type rik1 product is responsible for heterochromatinization throughout the silent domain of the mating-type region.     

Nature of Rec+ revertants isolated from Escherichia coli K-12 cultures with recA- mutations

The nature of Rec⁺ revertants isolated previously from cultures of recombinationally defective strainEscherichia coli K-12 AB 2463 recA13 was studied. With the aid of phage P1 vira the chromosome region of the recA gene in cells of strain JC2915F^- were transduced, after which the recombination capacity of the transductants was determined by crossing with JC158Hfr cells and their resistance to ultraviolet radiation was established. Sensitivity of the transductants to suppressor phages was determined. The Rec⁺ revertants were shown to differ with respect to the recA gene. In some Rec⁺ revertants the Rec⁺ phenotype appeared as the result of a back mutation in this gene from rec^- to rec⁺, whereas in other revertants the Rec⁺ phenotype was due to indirect suppression.Department of Biology and General Genetics, Patrice Lumumba Peoples' Friendship University, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. M. Zhdanov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 12, pp. 1487–1488, December, 1976.     

The detection of chemical impurities by high pressure liquid chromatography and the genetic activity of medical grades of pyrvinium pamoate inSaccharomyces cerevisiae andSalmonella typhimurium

The genetic activity of several medical grades of the anthelmintic drug pyrvinium pamoate, which is a dipyrvinium salt, was studied in a diploid mitotic recombination and gene conversion assay (strain D5 ofSaccharomyces cerevisiae), and in several haploid yeast reversion assays (strains XV185-14C, XY718-1A, and 7854-1A). All of the samples were recombinogenic in strain D5 and mutagenic in the haploid strains, however, the degree of genetic activity varied considerably among the medical grades of pyrvinium pamoate that were tested. Similarly, these samples varied in degree of mutagenicity when they were tested in strains TA97, TA98, TA100, and TA102 ofSalmonella typhimurium, but some of the medical grades of pyrvinium pamoate were mutagenic both in the presence and in the absence of the metabolic transformation system, whereas other medical grades of the drug required such activation to be mutagenic. In addition, the medical grades and dosage forms of several brands of pyrvinium pamoate were examined for purity by fluorescence high pressure liquid chromatography (HPLC) using a methanol:water (9010) solvent system. The HPLC data indicate that monopyrvinium salts are the major contaminants in these pharmaceuticals. In general, there is a correlation between the degree of genetic activity and toxicity, and the number and relative quantity of impurities found in each sample.     

复制缺陷型腺病毒AdE1CMV-NGF的制备

通过DNA重组技术 ,经亚克隆和克隆过程构建分泌表达型重组腺病毒穿梭质粒pAdE1CMV NGF ;制备完整高纯度辅助病毒 pJM1 7。将 pAdE1CMV NGF和 pJM1 7在 2 93细胞中同源重组 ,获得复制缺陷型腺病毒重组体AdE1CMV NGF。梯度系列稀释测得滴度为 4 .6× 1 0 10 PFU/mL。     

广州市2019年H3N2流感病毒分子流行特征分析

目的 对广州市2019年不同来源的H3N2流感病毒进行基因测序,分析H3N2流感病毒的进化变异特点。方法 对广州市2019年门诊监测、暴发疫情、住院重症病例等不同标本来源的H3N2流感病毒进行分离并对其血凝素（HA）和神经氨酸酶（NA）基因进行测序,运用DNA Star 7.1、Mega 6.0软件分析病毒的变异和进化特点。结果 2019年广州市H3N2流感表现为流行期Ⅰ（2019年1-8月）和流行期Ⅱ（2019年11-12月）2个流行高峰。男性和女性的H3N2流感病毒阳性率分别为13.46%（703/5 221）和11.50%（510/4 435）,差异有统计学意义（χ²=8.43,P=0.00）。10~20岁年龄组H3N2流感病毒阳性率最高（25.18%,665/2 641）,各年龄组阳性率差异有统计学意义。测序发现,不同标本来源的毒株高度同源,亲缘关系相近,属于3C.2a.1分支。根据流行时间和进化特点,进一步划分为Group 1~3共3个小进化分支,Group 1分支流行于流行期Ⅰ、Group 3分支流行于流行期Ⅱ,Group 2分支为2个流行期过度的进化分支,流行期Ⅱ的病毒由流行期Ⅰ的病毒进化而来,且不同分支存在基因重组的现象。在疫苗选择压力下,Group 1~3分支逐渐出现HA抗原位点突变,导致新的抗原漂移。HA抗原位点变异主要发生A和B区,Group 1分支和Group 3分支受体结合位点变异发生在前壁和后壁,Group 2~3分支在HA抗原位点A区缺失2个糖基化位点。结论 2019年广州市H3N2流感病毒的遗传变异包括位点突变和基因重组。在疫苗免疫压力下H3N2流感病毒发生快速的进化变异,抗原位点变异逐渐累积,进而出现新的抗原漂移。应对H3N2流感病毒分子流行特点进行持续监测。     

Immunogenicity and reactogenicity of BNT162b2 booster in BBIBP-CorV-vaccinated individuals compared with homologous BNT162b2 vaccination: Results of a pilot prospective cohort study from Lebanon

Facing new COVID-19 waves, the effectiveness of BBIBP-CorV has been noted to be low in countries whose populations were already administered two doses of the vaccine. Heterologous vaccination using ChAdOx1-S/BNT162b2 elicited higher immunogenicity compared with homologous immunization. BBIBP-CorV/BNT162b2 combination is worth testing. In this pilot prospective cohort study conducted at Makassed General Hospital, Beirut, Lebanon, from February 17, 2021, to June 30, 2021, we tested the safety and immunogenicity of a BNT162b2 booster dose in COVID-19-naïve individuals who had received two doses of the BBIBP-CorV vaccine. Heterologous booster vaccination was found to be safe and well tolerated. It was significantly associated with higher anti-spike IgG geometric mean titers compared to that after homologous BNT162b2 immunization in COVID-19-naïve individuals [(8040 BAU/mL, 95% confidence interval (CI), 4612–14 016) vs (1384 BAU/mL, 95% CI, 1063–1801), respectively, (P < 0.0001)]. In countries with limited access to mRNA vaccines and where populations have already received BBIBP-CorV, mixing BBIBP-CorV/BNT162b2 is seen to overcome the low immunogenicity induced by BBIBP-CorV alone, thus potentially providing protection against emerging variants.     

携带双自杀基因且可诱导敲除SV40T的逆转录病毒载体的构建与结构鉴定

目的构建携带双自杀基因且可诱导敲除SV40T的逆转录病毒载体,优化目前的肝细胞永生化。方法去除eGFP终止子taa的pSEB-HUS质粒为逆转录病毒基础质粒。先将SV40T及其启动子hEFH亚克隆至pSEB-HUS,再将LoxP位点插入至pSEB-SV40T质粒的抗性基因Blasticidin上游获得pSEB-LoxP-SV40T质粒。同时将CD自杀基因定向克隆至pSEB-HUS的eGFP下游;然后设计一段HSV-tk自杀基因引物,在上游引物的5′端加入方向一致的LoxP序列。PCR获得TK基因后,定向克隆至CD下游获得pSEB-CD-TK,最后将pSEB-CD-TK上的双自杀基因亚克隆至pSEB-LoxP-SV40T质粒上得到携带双自杀基因及SV40T的质粒。结果PCR及酶切鉴定均证实两个自杀基因及SV40T正确克隆至逆转录病毒质粒中,目的基因序列与GenBank报道一致,两个LoxP位点方向相同。结论成功构建携带双自杀基因且可诱导敲除SV40T的逆转录病毒载体。     

Mitochondrial genetics of Coprinus: Recombination of mitochondrial genomes

Summary The formation of the sexual mycelium or dikaryon in the basidiomycete Coprinus cinereus involves exchange and migration of nuclei without accompanying exchange of mitochondria. The dikaryotic growth which appears around the periphery of mated monokaryons has exclusively the mitochondrial genome of the recipient cells. Recombination of mitochondrial genomes is not, however, precluded during dikaryosis. Using monokaryons with different mitochondrial gene mutations, [acu-10] causing cytochrome aa ₃ deficiency and[cap-1.1] conferring resistance to chloramphenicol, it was shown that recombinant mitochondria arise in the zone of contact of mated monokaryons.     

肝细胞生长因子对多囊肾病囊肿衬里上皮细胞增殖及细胞外基质合成的影响

目的：研究重组人肝细胞生长因子（rhHGF）对常染色体显性遗传型多囊肾病（ADPKD）囊肿衬里上皮细胞增殖及细胞外基质合成的影响。方法：用^3H-TdR掺入法测定不同浓度（0．5、1、2．5、5ng/ml)rhHGF作用48h以及最适浓度的rhHGF分别作用24、48、72h ADPKD囊肿衬里上皮细胞系细胞的增殖情况;并分别用^3H-脯氨酸掺入法和放免法测定最适浓度rhHGF作用最佳时间后ADPKD囊肿衬里上皮细胞系细胞胶原及层粘连蛋白的合成情况。结果：rhHGF促进了ADPKD囊肿衬里上皮细胞增殖及胶原和层粘连蛋白的合成,以1ng/ml持续作用48h最为显。结论：rhHGF对体外培养的ADPKD囊肿衬里上皮细胞增殖及细胞外基质合成有明显的促进作用。