The p15gag and p12gag regions are both necessary for the pathogenicity of the murine AIDS virus.

The defective murine AIDS (MAIDS) virus has unique sequences in its p15gag and p12gag regions. To clarify whether these sequences are responsible for the development of MAIDS, we constructed recombinant viruses by replacing various regions of the gag gene of the nonpathogenic replication-competent LP-BM5 ecotropic virus with those of the MAIDS virus. Recombinants containing both unique sequences of the MAIDS virus were replication defective and induced MAIDS. However, a recombinant containing either the p15gag or p12gag region of the MAIDS virus was also replication defective but nonpathogenic in mice. A recombinant virus containing only the p30gag region of the MAIDS virus was replication competent and nonpathogenic. These results indicate that the p15gag and p12gag regions of the MAIDS virus do not function like those of replication-competent viruses and that both of the unique sequences in the p15gag and p12gag regions are required to develop MAIDS.     

Abscisic Acid-Induced Membrane Potential Changes in Barley Aleurone Protoplasts: a Possible Relevance for the Regulation of rab Gene Expression

The effect of ABA on the membrane potential of barley (Hordeumvulgare cv. Himalaya) aleurone protoplasts was studied by measuringthe distribution of the lipophilic cation tetraphenylphosphonium(TPP⁺). The resting membrane potential (E_m) according to ourmeasurements with TPP⁺ is about –53 mV and is in agreementwith membrane potential values as measured with intracellularmicroelectrodes (about –55 mV). The TPP⁺-measurementscould demonstrate a clear dependence of the resting E_m on theexternal pH (pH_e). Stimulation of the protoplasts with ABA induced a transienthyperpolarization of the membrane to –62 mV as measuredwith TPP⁺. The hyperpolarization was ABA-concentration dependent. Inhibition of the H⁺-ATPases with the specific proton pump inhibitorsdiethylstilbestrol (DES) or Micanozole effectively preventedhyperpolarization. This indicates that the hyperpolarizationis consistent with the activation of plasma membrane H⁺-ATPases.The K⁺-inward rectifier inhibitor BaCl₂ was able to prolongthe hyperpolarization. This result suggests that the hyperpolarizationcauses the opening of K⁺-channels. The ABA-induced proton-pump activation may be involved in ABA-inducedgene-expression, as DES was able to inhibit this gene expression.BaCl₂ did only show a slight inhibitory effect on ABA-inducedgene-expression. (Received January 4, 1994; Accepted April 12, 1994)     

Extractive fermentation of lactic acid by immobilizedLactobacillus casei using ion—exchange resin

Summary A novel method of lactic acid fermentation byLactobacillus casei immobilized in Ca—alginate gels is described, in which an ion—exchange resin packed column is attached to a fermentor for separation of lactic acid from fermentative broth. The technique successfully alleviated the restriction imposed by lactic acid on bacterial growth and product formation. As compared to the conventional batch fermentation, the new fermentation technique enhanced the lactic acid productivity and sugar conversion rate from 0.328g/L·h and 88. 2% to 0.482g/L·h and 98.6%, respectively.     

Changes and Relationship of PAF and TNF in Rats with Myocardial Ischaemia and Reperfusion Injury

IN THIS STUDY IT IS REPORTED THAT: (1) the levels of blood platelet-activating factor and serum tumour necrosis factor significantly increased after coronary ligation and reperfusion, compared with sham-ligated controls, in an anaesthetized rat model; (2) compared with vehicle controls, pretreatment with the PAF antagonist BN 50739 (10 mg/kg, i.v.) produced significant decreases in infarct size (from 29.6 +/- 4.0% to 22.4 +/- 2.1%, p < 0.05 after 3 h ligation, and from 28.5 +/- 9.5% to 10.5 +/- 4.5%, p < 0.01 after 4 h reperfusion) and the level of serum TNF (from 10.4 +/- 7.7 U/ml to 3.9 +/- 4.8 U/ml, p < 0.05); and (3) a significan positive correlation was found between the level of blood PAF or serum TNF and infarct size. The present results indicate that PAF and TNF may be important mediators involved in myocardial ischaemia and reperfusion injury, and that PAF antagonists may exert a protective effect on ischaemic or reperfused myocardium by inhibiting the interaction of PAF and TNF.     

氚水在模拟水生－陆生生态系中的迁移与分布

利用同位素示踪技术研究了进入水体的ＨＴＯ向陆地的迁移。结果表明：１．进入水体的ＨＴＯ将向系统各组分转移,池水中的ＨＴＯ单调地减少,底泥及水生生物中的ＨＴＯ浓度皆在经历某一最大值后平缓地下降;２．ＨＴＯ中的而以自由水沉和结合态氚存在于水生动植物和底泥中;３．ＨＴＯ还明显地向毗邻的陆地和作物迁移,在一个半月期间,陆地系统中的总而约占水体的２４％。     

植物细胞离析酶的制备和应用

用 Aspergillus sp．A-19菌经固体发酵研制成一种新的植物细胞离析酶(SeparatasezA—P)。其离析单细胞的酶活力平均为70 767u／g,有效作用的pH在3．0—7．0,温度为20—45℃。发酵培养基配方是麸皮：桔皮粉：(NH₄)₂SO₄(w／w)为100:100:O．63,料水比为1 :2．0,培养适宜条件为25℃、60小时。     

麦迪霉素产生菌酮基还原酶基因的研究

将麦迪霉素产生菌基因文库中与放线紫红索酮基还原酶基因actⅢ有同源性的4·0kb DNA片段克隆到质粒载体pWHM3中,构成重组质粒pCB4。将质粒pCB4转入酮基还原酶基因缺陷菌株——加利利链霉菌ATCC3167l中,得到转化子。转化子发酵产物经TLC和HPLC分析证明是阿克拉菌酮,与加利利链霉菌原株ATCC31133的产物相同,说明麦迪霉素产生菌酮基还原酶基因互补了加利利链霉菌ATCC31671中缺陷的酮基还原酶基因,使其恢复了产生阿克拉菌酮的能力。4．Okb DNA片段插入方向相反的重组质粒pCBR4在加利利链霉菌ATCC31671中发酵产物经TLC分析证明也是阿克拉菌酮,这说明4．0kbDNA片段中麦迪霉素产生菌酮基还原酶基因具有自身的启动子。对4．0kb DNA片段进行了限制酶酶切分析,建立了其酶切图谱。以actⅢ基因为探针,经分子杂交以及亚克隆和DNA转化实验,将麦迪霉索产生菌酮基还原酶基因定位于BssH Ⅱ—BamH Ⅰ 1．3kb DNA片段上。对1．3kb DNA片段核苷酸序列分析结果表明：此1．3kbDNA片段中含有一个独立的ORF,起始密码ATG,终止密码TAG,含783bp;在起始密码上游有GGAGG5个核苷酸SD序列;此ORF编码260个氨基酸,与actⅢ基因编码的261个氨基酸相似性为77．4%,相同性为66．7％,对麦迪霉素产生苗酮基还原酶基因的可能作用进行了讨论。     

DISCOVERY OF TWO MID-TERTIARY MAMMALIAN FAUNAS FROM HAIYUAN, NINGXIA, CHINA

Inl988-199otheRegionalGeologicalSurveyTeamoftheGeologicalBureauofNingxia(RGSN)foundsomefossilmammalsinthelowerpartoftheHo11g1iugouFormationandtheupperpartoftheOligocene.Inl992ajointteamoflnstituteofVertebratePaleontologyandPaleoanthropo1ogy,AcademiaSinica(IVPP),andtheRGSNwenttoHaiyuailCountyandcollectedmorefossilmamma1sfromtheYuanjia-wowoareausi11gascreen-washingmethodThemammalfaunafromthelowerpartoftheHongliugouFormationiscomposedofAprotodonsp.,Indricotheriidaeindet.,Rhinoceroti…