Triterpenoid glycosides from the bark of Mimosa tenuiflora.

Two new saponins were isolated from Mimosa tenuiflora and their structures established as 3-O-[alpha-L-rhamnopyranosyl(1----2)-beta-D-glucopyranosyl-(1----3]-(alp ha-L- arabinopyranosyl-(1----4]-beta-D-xylopyranosyl-(1----2)]-[beta-D- xylopyranosyl-(1----4)]-beta-D-glucopyranosyl)-28-O-alpha-L-rhamnopyrano syl oleanolic acid and 3-O-[alpha-L-rhamnopyranosyl-(1----2)-beta-D-glucopyranosyl-(1----3]-(al pha- L-arabinopyranosyl-(1----4]beta-D-xylopyranosyl-(1----2)]-[beta-D- xylopyranosyl-(1----4)]-beta-D-glucopyranosyl) oleanolic acid.     

Functional analysis of the Streptomyces ambofaciens element pSAM2.

pSAM2 is an 11-kb element integrated in the Streptomyces ambofaciens ATCC23877 genome and found additionally as a free replicon present at several copies per chromosome in strain JI3212, the derivative of ATCC23877 isolated after uv irradiation. In spite of its small size, this element specifies numerous functions including maintenance, site-specific integration, self-transmissibility, pock formation, and mobilization of chromosomal markers. After transfer of the free form of pSAM2 to Streptomyces lividans, the free and the integrated forms coexist. A functional map of pSAM2 was deduced from phenotypes exhibited in S. lividans by numerous deletion or insertion derivatives. In addition to the previously characterized regions sufficient for site-specific integration we have shown that separate regions are involved in either plasmid maintenance as a free molecule, plasmid transfer, and pock formation. Transfer of pSAM2 could depend on its ability to be maintained in a free form, since plasmids deficient in this function are transferred at very low frequency. Deletions of some regions of the plasmid are lethal for the plasmid or the host, but if some other regions are deleted simultaneously, transformants can be obtained.     

Oxidation of tyrosine by peroxidase isozymes derived from peanut suspension culture medium and by isolated cell walls

A comparative study on tyrosine oxidation was made with a pure cationic and anionic peroxidase from peanut cell culture medium. The results showed that both isozymes possessed almost identical capacity to oxidize tyrosine to dityrosine, isodityrosine and polytyrosine with the main difference being the pH optimum (pH 4 for the anionic and pH 7 for the cationic isozyme). Variation of reaction time after 1.5 h incubation had little effect on the quantity and quality of the oxidation products. On the other hand, increase of enzyme units correspondingly increased tyrosine-oxidation. The removal of heme and carbohydrate moieties from the holoenzyme arrested the reaction thereby suggesting the role played by these moieties in stabilizing the active site of peroxidase isoenzymes. Isolated cell wall extracts catalyzed the tyrosine-oxidation equally well as the purified peroxidase. Even though polyclonal antibodies against anionic peroxidase inhibited the in vitro tyrosine reaction they did not affect the tyrosine oxidation by the cell walls, while the cationic antibodies did.Abbreviations A.PRX anionic peanut peroxidase - C.PRX cationic peanut peroxidase - PcAb polyclonal antibodies - ELISA enzyme-linked-immuno-sorbent-assay - TFMS trifluoromethane sulfonic acid     

不同利用方式下稻田效益的综合评价

一、引言评价是多目标系统优化和决策的基础。和任何其他农业生态系统一样,稻田生态系统具有多目标、多功能的特点,单项指标难以反映系统的优劣。目前,川东南地区稻田开发利用方式多种多样,但效益评价主要是采用简单的比较分析或粗放的定性描述,尚未形成系统的     

流行性出血热地鼠肾细胞灭活疫苗人体试用细胞免疫反应观察

观察了20位志愿者在接种试验性流行性出血热(EHF)地鼠肾细胞(GHKC)双价灭活疫苗后的细胞免疫反应,并以其体液免疫反应作对照观察。用淋巴细胞转化试验测定细胞免疫水平。结果首针疫苗接种后42天和56天,特异性刺激指数(SSI)和非特异性刺激指数(NSI)均较免疫前显著增高(P_(SSI)<0.001;P_(NSI)<0.02),免疫后SSI累计阳转率为100％,NSI累计阳转率为60％,免疫后6个月二者均降低至正常水平。免疫后56天测定抗体,荧光抗体阳转率为100％;微量感染性中和试验表明,针对家鼠型病毒L99株中和抗体阳转率为95％,而针对野鼠型病毒JR株阳转率为65％。     

Absence of 7-acetyl taxol binding to unassembled brain tubulin

The effect of taxol on microtubule proteins at 0 degrees C is controversial. In order to determine if taxol is unable to bind to unassembled tubulin, as has been hypothesized, the binding of [3H]acetyl taxol has been studied using equilibrium microdialysis. Ac-taxol bound to microtubules at 37 degrees C and the binding remained stable when the temperature was lowered to 0 degrees C. Ac-taxol bound also at 0 degrees C to microtubules stabilized with rhazinilam. In contrast, there was no binding of Ac-taxol to unassembled tubulin, either free tubulin at 0 degrees C or tubulin, complexed with several microtubule poisons, at 0 and 37 degrees C.     

Reversal of insulin-induced negative cooperativity by monoclonal antibodies that stabilize the slowly dissociating ("Ksuper") state of the insulin receptor

Two monoclonal antibodies to the insulin receptor, MA-5 and MA-20, unlike other monoclonal antibodies, do not mimick the accelerating effect of insulin on the dissociation of 125I-insulin from the receptors (negative cooperativity). On the contrary, MA-5 and MA-20 markedly slow down the dissociation rate. We show now that MA-5 and MA-20 are potent antagonists of the negative cooperativity induced by insulin, and reverse the insulin-induced acceleration whether added simultaneously with insulin or after insulin. The reversal of the insulin-induced acceleration is almost immediate. These data strengthen the concept therefore that the insulin-receptor complex has access to alternative conformational states that can be stabilized by ligand-induced site-site interactions.