三尖杉叶精油化学成分的研究

三尖杉叶精油化学成分的研究苏应娟,王艇,张宏达（中国科学院武汉植物研究所武汉４３００７４）（中山大学生命科学学院广州５１０２７５）关键词三尖杉,精油,化学分类ＡＳＴＵＤＹＯＮＣＨＥＭＩＣＡＬＣＯＮＳＴＩＴＵＥＮＴＳＯＦＥＳＳＥＮＴＩＡＬＯＩＬＦＲＯＭ...     

镁离子对阿霉素线粒体毒性的防护作用

利用ＥＳＲ技术研究了阿霉素与心肌线粒体的相互作用及Ｍｇ＾２＋的防护作用。结果表明：在线粒体及亚线粒体体系,Ｍｇ＾２＋可有效地抑制阿霉素半醌自由基产生,在一定浓度范围内抑制效果依赖于Ｍｇ＾２＋的浓度。另外,Ｍｇ＾２＋显著抑制阿霉素诱导产生的线粒体脂质过氧化。在亚线粒体体系,我们观察到阿霉素半醌自由基的固定化信号,并发现Ｍｇ＾２＋能明显延缓固定化信号出现。     

Functional groups at the catalytic site of F1 adenosine triphosphatase

The protection of F1 ATPase by inorganic phosphate, ADP, ATP, and magnesium ion against inactivation by 1-fluoro-2,4-dinitrobenzene, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, and 1-(ethoxycarbonyl)-2-ethoxy-1,2-dihydroquinoline, respectively, has been investigated. Dissociation equilibrium constants and rate constants for the labeling reactions have been deduced from a quantitative treatment of the kinetic data. Comparison of these dissociation constants with each other and with the corresponding literature values indicates that the essential Tyr, Arg, Lys, and Glu or Asp residues are indeed located at the catalytic site of the enzyme. Examination of the rate constants for the labeling reactions in the presence of excess inorganic phosphate, ADP, ATP, or magnesium ion, respectively, suggests that the essential phenol and amino groups are located nearer to the bound inorganic phosphate or the gamma-phosphate group than to the alpha- or beta-phosphate group of the bound ATP, that the essential guanidinium group is located nearer to the alpha- or beta-phosphate group than to the gamma-phosphate group of the bound ATP or the bound inorganic phosphate, and that the essential carboxylate group is located slightly farther away but complexed with magnesium ion which it shares with the bound inorganic phosphate. A mechanism consistent with these topographical relationships is proposed for the catalytic hydrolysis and synthesis of ATP.     

Selective suppression of the murine autologous mixed lymphocyte reaction by physiological concentrations of hydrocortisone: effects on cell-surface Ia antigens

Strong, adult (Type II) autologous mixed lymphocyte reactions (AMLR) were observed in cultures of lymphoid cells from both A.TH and A.TL mice. These were suppressed by more than 90% in the continuous presence of 7.5 × 10^?8M hydrocortisone-21-sodium succinate. This concentration of hormone had minimal effects on the allogeneic mixed lymphocyte response (MLR) and the mitogenic response to concanavalin A (Con A). Higher concentrations suppressed all three responses. Treatment of autologous cell mixtures for the first 30 hr with 7.5 × 10^?8M hydrocortisone resulted in a 78% suppression of the AMLR. This was not associated with a detectable decrease in the quantity of Ia antigens on the stimulator-cell surface, as evaluated by the susceptibility of treated cells to antibody dependent, complement-mediated lysis, using [A.TH × B.10M]F₁ anti-A.TL antiserum. Hence, this suppression did not appear to result from an alteration of the antigens putatively associated with stimulation of the AMLR. Separate pretreatment of stimulator and responder cells with 7.5 × 10^?8M hydrocortisone followed by culturing with appropriate companion cells had no major effect on the AMLR. Therefore, low-dose hydrocortisone did not appear to selectively eliminate or permanently inactivate subpopulations of responder or stimulator cells. Rather, it appeared to regulate active cellular processes that are initiated by the coculturing of these cells and are required for the early stages of autologous lymphocyte activation.     

Effects of abscisic acid on CAM in Portulacaria afra

Water stress induces Crassulacean acid metabolism (CAM) in Portulacaria afra as manifested by day stomatal closure, organic acid fluctuation, and night CO₂ uptake. We now have evidence that abscisic acid treatment of leaves causes partial stomatal closure that is accompanied by the induction of CAM in a manner similar to water stress. There appears to be an inverse relationship between exogenous CO₂ uptake and decarboxylation of organic acids in that organic acids remain high during the day providing stomata are open. When stomata close, there is consumption of organic acids by decarboxylation. The hypothesis is that stomatal opening controls CAM in this species.This material is based upon work supported by the Science and Education Administration of the USDA under Competitive Grant No. 5901-0410-8-0018-0.     

Nitrogen fixation, denitrification, and pleomorphic growth in a highly pigmented Spirillum lipoferum.

A strain of Spirillum lipoferum with intense red pigmentation was isolated from the roots of Cynodon dactylon "Coastal." This isolate vigorously reduced acetylene when grown in N-free, Na-malate, semisolid agar, and it was identical to S. lipoferum strain SP7 by standard taxonomic tests. Both S. lipoferum SP7 and the C. dactylon root isolate displayed the unique features of being denitrifiers as well as N2 fixers. The N2-dependent growth curve was biphasic: cells in younger cultures showed the characteristic spiral shape and motility, but those in older cultures developed larger, nonmotile, cystlike forms. Nitrogenase activity seemed associated only with younger spiral forms. The red pigment may be a b- or c-type cytochrome. The strong red color, which this strain develops, could be used as a marker in evaluating soil inoculation experiments.     

Nitrogen fixation, denitrification, and pleomorphic growth in a highly pigmented Spirillum lipoferum.

A strain of Spirillum lipoferum with intense red pigmentation was isolated from the roots of Cynodon dactylon "Coastal." This isolate vigorously reduced acetylene when grown in N-free, Na-malate, semisolid agar, and it was identical to S. lipoferum strain SP7 by standard taxonomic tests. Both S. lipoferum SP7 and the C. dactylon root isolate displayed the unique features of being denitrifiers as well as N2 fixers. The N2-dependent growth curve was biphasic: cells in younger cultures showed the characteristic spiral shape and motility, but those in older cultures developed larger, nonmotile, cystlike forms. Nitrogenase activity seemed associated only with younger spiral forms. The red pigment may be a b- or c-type cytochrome. The strong red color, which this strain develops, could be used as a marker in evaluating soil inoculation experiments.     

Studies of the mechanisms for the induction of in vivo tumor immunity. VI. Induction of specific and nonspecific cell-mediated immunity in tumor-bearing hosts and its correlation with transplantation tumor immunity

Studies were performed to determine the development of cell-mediated cytotoxic response at tumor site in C57BL/6 mice bearing progressively growing FBL-3 ascites leukemia. The effectors isolated from tumor ascites are found to be highly cytotoxic for leukemic target cells. The levels of cytotoxicity obtained with effectors isolated from tumor site are generally higher than those obtained with immune mice. This cytotoxicity is both specific and nonspecific. The specific cytotoxicity against tumor-associated antigen is mainly mediated by T cells and the nonspecific cytotoxicity against unrelated tumor cells is mediated largely by macrophages. The T-cell-enriched preparation did not give significant natural killer activity. When testing the ability of these effectors to produce in vivo immunity against the challenge of FBL-3, it was found that only T cells could confer the transplantation-type immunity, but the immunity was transient. The macrophage-enriched preparation isolated from tumor ascites failed to give in vivo protection. These findings indicate that in FBL-3 system, mice with progressively growing tumors are able to develop immune response against tumor cells. However, this immunity is probably interfered with by a suppressor factor(s) or suppressor cells which restrict their activity to eliminate the tumor cells effectively.