Effect of ethionine on synthesis and methylation of ribosomal ribonucleic acid in regenerating rat liver

Ethionine, a hepatocarcinogen, was administered into rats 24 h before partial hepatectomy and immediately thereafter. Hepatic precursor ribosomal RNA (pre-rRNA) obtained 20 h after the operation of rats injected with ethionine and adenine resulted in methyl deficiency as judged by the incorporation of [3H]methyl group of S-adenosylmethionine into nuclear rRNA by partially purified rRNA methylase. The ethionine and adenine treatment causes methyl deficiency of nuclear rRNA at 2'-hydroxyribose sites of cytidine and uridine, but not at base sites. Although the ethionine and adenine treatment produced no significant change in total hepatic RNA synthesis in vivo assayed by the incorporation of labeled orotate, a one-third increase in nuclear rRNA synthesis as well as a one-third decrease in microsomal rRNA synthesis was found under the treatment. These results suggest that the undermethylation at 2'-hydroxyribose of pre-rRNA in liver nucleus, which is caused by ethionine and adenine administration into rats, causes an inhibition of the processing of nuclear pre-rRNA to cytoplasmic rRNA.     

Raman spectroscopic and X-ray diffraction studies of the effect of temperature and Ca2+ on phosphatidylethanolamine dispersions

Raman spectroscopy and X-ray diffraction are used to study the effect of heat and Ca²⁺ on dimyristoylphosphatidylethanolamine dispersions. Unlike phosphatidylcholine dispersions, dimyristoylphosphatidylethanolamine bilayers (at pH 8) require heating above T_m in order for hydration to occur and apparently bind Ca²⁺ at very low levels. These results are related to models for membrane fusion.     

Survival of Shigella in Sewage: II. Effect of Glycerol on Shigella flexneri and Shigella Bacteriophage1

Glycerol (30%) inhibited or delayed the adsorption of Shigella bacteriophage on its host organism, S. flexneri II; glycerol also inhibited or delayed the burst of phage, whether or not adsorption was carried out in the presence of glycerol. Studies of the mechanisms of these effects showed that viscosity and osmotic shock probably were not responsible for either phenomenon. The inhibition of adsorption, however, was proportional to the concentration of glycerol, and appeared to be a function of the hydroxyl groups on the glycerol molecule. The inhibition of burst seemed to be related to the osmotic pressure outside the bacterial cells.     

油盘孢属和泽田外担菌的研究

寄生于樟、阴香和肉桂等植物上的泽田外担菌和油盘孢属真菌,几十年来分类上存在许多不同看法,或全部归泽田外担菌,或全部归油盘孢属,把此二类不同真菌混淆起来,造成名称混乱。本文通过形态学的研究,表明泽田外担菌与油盘孢属的区别是:泽田外担菌具担子层,担孢子4—8个生担子上,寄主是樟树;而油盘孢属的孢子生菌丝上,形成孢子堆,寄主是阴香和肉桂等植物。     

青霉素G酰化酶α亚基Ser177的突变对酶活性的影响

用盒式突变和定点突变对大肠杆菌青霉素G酰化酶α亚基177位ser进行了突变研究,结果发现所挑选的突变体均无酶的活力,这一结果可能可以用来解释Ser 177附近肽段和一些青霉素结合蛋白青霉素结合区在一级结构上保持同源性的原因。     

用免疫荧光单克隆抗体对脊髓灰质炎病毒抗原表位的分析

用间接免疫荧光与中和试验筛选出来的抗脊髓灰质炎2型与3型不同毒株的12个单克隆抗体,其中3个仅有免疫荧光活性,9个具有中和与免疫荧光活性。用免疫荧光活性的单克隆抗体进行试验,发现它们在识别特异性抗原表位方面与中和性单克隆抗体相似,显示出株特异的、几个毒株共同特异的或型特异的抗原表位。根据表位分布关系及特征,可以用来鉴别型内毒株的特征、毒株的抗原分析、抗原变异的研究以及疫苗相关病例的鉴别。所得结果与中和性单克抗隆抗体及T1-寡核苷酸指纹图谱分析一致。而免疫荧光单克隆抗体识别抗原表位的活性范围比中和性单克隆抗体更广。另外还发现某些兼有荧光与中和两活性的同一个单克隆抗体,用不同方法(IF与NT)进行试验时,与相同毒株出现不同表位反应,这点是值得引起注意需待进一步证实的重要问题。     

Effect of hyperlipidemic serum on lipid peroxidation, synthesis of prostacyclin and thromboxane by cultured endothelial cells: protective effect of antioxidants

An increased lipid peroxides and a decreased production of prostacyclin have been shown in advanced atherosclerotic lesions and plasma. Our purpose was to determine whether the similar findings could be observed in cultured endothelial cells, and whether antioxidants could protect the cell against peroxide injury. In these experiments we have used bovine aortic endothelial cells in culture to address the issue of hyperlipidemia-induced arterial damage. Results of the present study showed that different concentration of hyperlipidemic sera from atherogenic rabbits induced a time- and dose-dependent alteration in the production of prostacyclin and levels of lipid peroxides in endothelial cells. Endothelial cells incubated with hyperlipidemic serum increased prostacyclin generation significantly during the initial stages and then continuously decreased. When endothelial cells were incubated for 36 h, TXA2 generation was also impaired and at the same time the cellular lipid peroxides content increased. There was a positive correlation between the concentration of hyperlipidemic serum and lipid peroxides and an inverse correlation with prostacyclin synthesis. The medium supplemented with antioxidant selenium or vitamin E showed a significant decrease in lipid peroxides and an increase in prostacyclin synthesis. These results suggest that both hyperlipidemic serum and lipid peroxides injury endothelial cells and inactivate prostacyclin synthetase, resulting in a decrease of prostacyclin production, while antioxidants have a protective effect. We conclude that the increase in lipid peroxides in association with hyperlipidemia results in alteration of prostacyclin synthesis that may play an important role in the pathogenesis of atherosclerosis.     

Apolipoprotein E localization in rat hepatocytes by immunogold labeling of cryothin sections

The distribution of apolipoprotein (apo) E in rat hepatocytes was investigated with an affinity-purified polyclonal antibody raised against apoE isolated from hepatogeneous very low density lipoproteins (VLDL). The distribution of this antibody was visualized with colloidal gold complexed to anti-rabbit IgG. By epipolarization microscopy, apoE was found uniformly along the basolateral surfaces of all hepatic parenchymal cells, showing a striking intensity along the sinusoidal front. Punctate deposits of colloidal gold appeared to be randomly distributed within all hepatocytes. Widely scattered Kupffer cells also stained for apoE. Electron microscopic examination of immunogold-labeled cryothin sections showed that hepatocytic microvilli projecting into the space of Disse consistently contained clusters of immunogold. The gold particles were variably associated with evident lipoprotein particles, raising the possibility that apoE alone may bind to receptors or other macromolecules at the surface of hepatocytes. Endosomes near the sinusoidal front and multivesicular bodies in the Golgi/biliary area labeled intensely for apoE, consistent with a high content of apoE associated with triglyceride-rich lipoprotein remnants contained within these organelles. Some but not all nascent VLDL particles within putative forming Golgi secretory vesicles were labeled, but many other Golgi vesicles and cisternae that lacked evident VLDL particles were also labeled. These results suggest that at least some apoE associates with nascent VLDL in forming Golgi secretory vesicles. Unexpectedly, the matrix of all hepatocytic peroxisomes was heavily labeled. Immunoblots with the affinity-purified anti-rat apoE IgG against proteins from highly purified peroxisomes isolated from rat hepatocytes revealed a protein with an apparent molecular mass of 34.5 kDa, similar to that of rat apoE in rat blood plasma. In addition, gold was sometimes found in the area either adjacent to peroxisomes or between multivesicular bodies and the bile canaliculus not evidently associated with a membranous compartment. These observations suggest that apoE may participate in interorganellar cholesterol transport within hepatocytes.     

Purification of the microsomal Ca2+-ATPase from rat liver

Summary The Ca²⁺-ATPase from rat liver microsomes has been solubilized in Triton X-100 and purified to homogeneity by ficollsucrose treatment, column chromatography with agarose-hexane adenosine 5-triphosphate Type 2, and high pressure liquid chromatography (HPLC). The purified enzyme obtained by this sequential procedure exhibited a 183-fold increase in specific activity. After ficoll-sucrose treatment, the activity of the Ca²⁺-ATPase was stable for at least two weeks when stored at –70°C. In SDS-polyacrylamide gels, several fractions from HPLC chromatography showed a single band at a position corresponding to a molecular weight of about 107 kDa. This value is consistent with the molecular weight of the phosphoenzyme intermediate of endoplasmic reticulum (ER) Ca²⁺-ATPase. Further characterization of the ER Ca²⁺-ATPase was performed by western immunoblots. Antiserum raised against the 100-kDa sarcoplasmic reticulum (SR) Ca²⁺-ATPase cross-reacted with the purified Ca²⁺-ATPase from rat liver ER membranes.