Differential expression of 2′∶3′-cyclic nucleotide 3′-phosphodiesterase in cultured central,peripheral, and extraneural cells

The relative levels of the central nervous system myelin marker enzyme 2:3-cyclic nucleotide 3-phosphodiesterase (EC 3.1.4.37, CNPase) were determined in neuroblastoma, astrocyte, oligodendrocyte and Schwann cell cultures and in freshly isolated human lymphocytes and platelets. The highest specific activities were associated with the cells that elaborate myelin membrane in the central and peripheral nervous system, oligodendrocytes and Schwann cells, respectively. Antiserum to bovine CNPase recognized both CNP1 and CNP2 in CNS myelin and human oligodendroglioma. In addition, a 53,000 dalton protein was evident on autoradiographs of immunoblotted PNS myelin and human oligodendroglioma proteins. Cultured rat oligodendrocyte, C₆ and mouse NA neuroblastoma CNPase appear to share common determinants with the corresponding normal rat CNS enzyme.     

辣椒四个品种的核型研究

本文对我国栽培辣椒Capsicum annuum L.的四个品种即汉川椒、华椒一号、牛角椒和二金条进行了核型分析,其染色体数目均为2n=2x=24,核型公式均为2n=24=20m+2sm+2st,但汉川椒和华椒一号具一对随体,牛角椒和二金条具两对随体。本文还对它们的进化关系进行了讨论。     

辣椒四个品种的核型研究

本文对我国栽培辣椒Capsicum annuum L.的四个品种即汉川椒、华椒一号、牛角椒和二金条进行了核型分析,其染色体数目均为2n=2x=24,核型公式均为2n=24=20m+2sm+2st,但汉川椒和华椒一号具一对随体,牛角椒和二金条具两对随体。本文还对它们的进化关系进行了讨论。     

ATF4在内质网应激调控成骨分化中的作用

为避免内质网中未折叠蛋白质的过度累积,真核细胞能激活一系列信号通路来维持内质网稳态,这个过程称为内质网应激。在骨生长发育中,适宜的内质网应激有助于成骨细胞、破骨细胞和软骨细胞的生长,可以促进骨髓间充质干细胞向成骨细胞分化。而过度的内质网应激会抑制成骨分化,严重的甚至导致骨质疏松、成骨不全等相关骨病的发生。内质网应激时可激活未折叠蛋白质反应,其主要是通过PERK/eIF2α/ATF4信号通路,上调转录激活因子4(ATF4)的表达。ATF4位于许多成骨分化调节因子的下游,是促进成骨分化的关键因子,在内质网应激对成骨分化的调节中发挥重要作用。在成骨分化过程中,适宜的内质网应激能通过激活PERK信号通路,诱导ATF4表达增加,进而上调骨钙素、骨涎蛋白等成骨所必需基因的表达,促进成骨分化。过度的内质网应激会激活ATF4/CHOP促凋亡途径,并导致Bax、胱天蛋白酶等凋亡信号分子的大量产生,进而导致细胞凋亡,抑制成骨分化。由于ATF4在ERS和成骨分化中的重要作用,ATF4在骨质疏松、成骨不全等骨相关疾病的治疗中具有重要意义。本文通过综述ATF4在内质网应激调控成骨分化中的作用机制,为相关骨性疾病治疗提供理论依据。     

Kinetics of formation of maltose and isomaltose through condensation of glucose by glucoamylase

A kinetic model was devised for the hydrolysis and synthesis of maltose and isomaltose by two glucoamylases from Rhizopus niveus and Aspergillus niger, and the validity of the model was verified experimentally at 313 K and pH 5.0. For both enzymes, the formations of maltose and isomaltose from glucose were parallel reversible reactions, and glucosyl transfer between maltose and isomaltose was not observed. The enzymes catalyzed rapid hydrolysis and synthesis of maltose. Isomaltose was hydrolyzed and synthesized more slowly, but the level produced from glucose was much higher than that of maltose. These hydrolysis and condensation reactions were expressed well by the model.     

Influence of predation on species coexistence in Volterra models

The possibility of predator-mediated coexistence of all species in model ecosystems of the Volterra type is discussed, that is, asymptotic behaviors of systems of two competing species are analyzed when one or two predators are added. All species in the communities can coexist in two distinct ways mathematically, that is, the species may coexist at equilibrium or may coexist in persistent oscillations. The stability of all species at equilibrium increases when one or two predators are added. The conditions for oscillatory coexistence in limit cycles or in chaotic behaviors of two-predator systems are more complicated than in those of one-predator systems. It is concluded that predator-mediated coexistence can be promoted by an intimate relationship between the competitive ability of the prey and the diet preference of the predators.     

Characterization of the env gene and long terminal repeat of molecularly cloned Friend mink cell focus-inducing virus DNA

The highly oncogenic erythroleukemia-inducing Friend mink cell focus-inducing (MCF) virus was molecularly cloned in phage lambda gtWES.lambda B, and the DNA sequences of the env gene and the long terminal repeat were determined. The nucleotide sequences of Friend MCF virus and Friend spleen focus-forming virus were quite homologous, supporting the hypothesis that Friend spleen focus-forming virus might be generated via Friend MCF virus from an ecotropic Friend virus mainly by some deletions. Despite their different pathogenicity, the nucleotide sequences of the env gene of Friend MCF virus and Moloney MCF virus were quite homologous, suggesting that the putative parent sequence for the generation of both MCF viruses and the recombinational mechanism for their generation might be the same. We compare the amino acid sequences in lymphoid leukemia-inducing ecotropic Moloney virus and Moloney MCF virus, and erythroblastic leukemia-inducing ecotropic Friend virus, Friend-MCF virus, and Friend spleen focus-forming virus. The Friend MCF virus long terminal repeat was found to be 550 base pairs long. This contained two copies of the 39-base-pair tandem repeat, whereas the spleen focus-forming virus genome contained a single copy of the same sequence.     

Demonstration of bovine brain calmodulin-dependent cyclic nucleotide phosphodiesterase isozymes by monoclonal antibodies

Calmodulin-dependent cyclic nucleotide phosphodiesterase from bovine brain is found to be composed of two distinct subunits, 60,000- and 63,000-dalton polypeptides. Peptide mapping of the subunits by partial proteolysis demonstrated that the 60-kDa polypeptide is not derived from the 63-kDa species. The interaction of the enzyme with three monoclonal antibodies, A6, C1, and A2, and the analysis of immunocomplexes by sucrose density gradient centrifugation revealed that calmodulin-dependent cyclic nucleotide phosphodiesterase exists in three different forms, i.e. (a) homodiamer of 60-kDa, (b) heterodimer of 60- and 63-kDa, and (c) homodimer of 63-kDa. A6 antibody reacts with both 60- and 63-kDa polypeptides indicating that they are immunologically related. C1 and A2 antibodies react with only 60-kDa polypeptide species. By using C1 Sepharose 4B affinity column chromatography, the 63-kDa homodimer which did not bind to the column (Fraction I) was separated from the 60-kDa polypeptide containing isozymes (the heterodimer and the 60-kDa homodimer) which were retained on the column and later eluted as a mixture (Fraction II). Fraction I, the 63-kDa homodimer enzyme, has higher Vmax toward cGMP as substrate than cAMP whereas the opposite was found with Fraction II. The specific activity of Fraction II enzyme toward cAMP was approximately 500 mumol/min/mg, the highest value ever reported for brain calmodulin-dependent cyclic nucleotide phosphodiesterase preparations.     

三七中达马烷型皂甙的热不稳定性及酸水解产物

前人已证明人参和三七中富含的达马烷型人参皂甙在通常酸性水解下甙元即发生变化,而在弱酸(如50％醋酸,0.1N盐酸)条件下则形成次级皂甙。本文报道人参甙(ginseno-sides)和三七甙(notoginsenosides)的水溶液在水浴上加热亦分别形成相应的C-20位去糖基的次级皂甙。联系到人参和三七均有在蒸煮加工后C-20位去糖基皂甙收率增大的趋势,似可认为人参和三七中的这类皂甙有相当一部分是在生药的加工泡制以及提取过程中形成的次级皂甙,而不一定是植物体的原生成分。将人参甙Rb_1单体以酸水解,不仅得到主产物人参二醇(3),还分离到异去氢原人参二醇(5)、达马烷-20(22)-烯-3β,12β,26-三醇(6)、20(R)-达马烷-3β,12β,20,25-四醇(7)以及20(S)-和20(R)-原人参二醇(1、2)的混合物,从而认为这些微量成分与人参二醇一样均为达马烷型人参皂甙在酸性水解条件下C-20位糖基断裂后由真甙元的侧链转化形成的工作产物。