扫描电镜分析牙齿釉质结构方法的讨论

通过扫描电镜对大熊猫牙齿釉质结构的三维观察与比较,结果表明:在同一枚牙齿上,不同部位的釉质切面,釉柱截面的形状、大小以及排列等,有不同的现象.因此在用上述特征描述时,应对所有要比较的样品,须精确地统一在相同的部位.本文以多次实验结果,表明了严格定位取样的重要性.     

云南引种的玫瑰天竺葵精油主要化学成份分析

玫瑰天竺葵从摩洛哥引入云南已试种成功,并开始大面积推广。其各生长期精油分析结果表明,随月份的推移,香叶醇含量下降。其香气特征与云南产香叶天竺葵(Pelargonium graveolens)精油不同,更接近印度波尔蓬香叶油的香气。     

大熊猫——剑齿象动物群的聚类分析

<正> 中外学者对我国南方石灰岩溶洞出土的第四纪哺乳动物化石(按照以往的习惯,又可总称为广义的“大熊猫——剑齿象动物群”)已经进行了长期的、广泛的研究。最近有人(计宏祥,1977;黄万波,1979)对这段历史作了详尽的总结。从历史的回顾中可以看到,随着化石材料的不断积累,华南溶洞出土的第四纪哺乳动物化石已由单一     

Antiplatelet effect of butylidenephthalide

Butylidenephthalide inhibited, in a dose-dependent manner, the aggregation and release reaction of washed rabbit platelets induced by collagen and arachidonic acid. Butylidenephthalide also inhibited slightly the platelet aggregation induced by PAF and ADP, but not that by thrombin or ionophore A23187. Thromboxane B2 formation caused by collagen, arachidonic acid, thrombin and ionophore A23187 was in each case markedly inhibited by butylidenephthalide. Butylidenephthalide inhibited the aggregation of ADP-refractory platelets, thrombin-degranulated platelets, chymotrypsin-treated platelets and platelets in the presence of creatine phosphate/creatine phosphokinase. Its inhibition of collagen-induced aggregation was more marked at lower Ca2+ concentrations in the medium. The aggregability of platelets inhibited by butylidenephthalide could be recovered after the washing of platelets. In human platelet-rich plasma, butylidenephthalide and indomethacin prevented the secondary aggregation and blocked ATP release from platelets induced by epinephrine. Prostaglandin E2 formed by the incubation of guinea-pig lung homogenate with arachidonic acid could be inhibited by butylidenephthalide, indomethacin and aspirin. It is concluded that the antiplatelet effect of butylidenephthalide is mainly due to an inhibitory effect on cyclo-oxygenase and may be due partly to interference with calcium mobilization.     

水稻黄化苗PAL内源性抑制物的初步纯化及其基本性质

从去胚乳水稻黄化苗中提取、并部分纯化了苯丙氨酸解氨酶的抑制因子(PAL-I)。它是非透析性的蛋白质;大部分活力可被蛋白酶(胰蛋白酶、链霉蛋白酶)所破坏。动力学实验表明PAL-I对PAL的抑制作用是竞争性的。水稻PAL-I不仅能抑制水稻PAL,而且能抑制从玉米、小麦、马铃薯块茎切片中提取的PAL;但不能抑制从水稻中提取的多酚氧化酶、α-淀粉酶(过氧化物酶除外)。     

Physicochemical properties of alpha- and beta-fibrinogenases of Trimeresurus mucrosquamatus venom.

alpha- and beta-Fibrinogenases (EC 3.4.21.5) were purified from Trimeresurus mucrosquamatus venom by the technique of recycling chromatography. Both enzymes were single polypeptide chains and homogeneous as judged by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis and ultracentrifugation. The sedimentation constants of alpha- and beta-fibrinogenases were 2.52 and 3.04 respectively. The molecular weight of alpha-fibrinogenase was 21 500--23 400, and that of beta-fibrinogenase was 25 000--26 000. The contents of proline, glycine and tryptophan were higher in beta-fibrinogenase than in alpha-fibrinogenase. The isoelectric points of alpha- and beta-fibrinogenases were pH 8.1 and 5.7 respectively. The optimal pH of alpha-fibrinogenase was about 7.4 and that of beta-fibrinogenase was around 8.5. The activity of alpha-fibrinogenase was completely destroyed after 30 min at 60 degrees C, pH 5.6, 7.4 and 9.0, while that of beta-fibrinogenase was not significantly affected by the same treatment. Both enzymes showed proteolytic activities toward fibrinogen and casein, but were devoid of phospholipase A, alkaline phosphomonoesterase and phosphodiesterase activities of the crude venom. The tosyl-L-arginine methylester esterase activity of beta-fibrinogenase was about 17 times that of the crude venom, while alpha-fibrinogenase was completely devoid of this activity. The fibrinogenolytic activity of alpha-fibrinogenase was markedly inhibited by EDTA and cysteine, while that of beta-fibrinogenase was inhibited markedly by phenylmethane sulfonylfluoride and slightly by tosyl-L-lysine chloromethylketone and cysteine.     

Profiles of IgG antibodies to nucleocapsid and spike proteins of the SARS-associated coronavirus in SARS patients

To evaluate humoral immunity against the SARS-associated coronavirus (SARS-CoV), we studied the profiles of IgG antibodies to the nucleocapsid (N) and spike (S) proteins of SARS-CoV. Serum specimens from 10 SARS patients were analyzed by Western blotting and an enzyme-linked immunosorbent assay (ELISA) using purified recombinant N and truncated S (S1, S2, and S3) proteins as antigens. Western blotting results demonstrated that 100% of the SARS patients tested positive for N protein-specific antibodies, 50% for S1 protein-specific antibodies, 30% for S2 protein-specific antibodies, and 70% for S3 protein-specific antibodies. The ELISA results, which showed positive rates of IgG reactivity against recombinant proteins N, S1, S2, and S3, were, respectively, 28.57, 14.29, 14.29, and 14.29% at week 1, 77.78, 55.56, 44.44, and 66.67% at week 2, 100, 75, 75, and 87.5% at week 3, and 100, 77.78, 77.78, and 88.89% after 3 weeks. The average titers of IgG against recombinant proteins N, S1, S2, and S3 were, respectively, 691, 56, 38, and 84 after 3 weeks. These results suggest that the recombinant proteins N and S3 are potentially useful antigens for a serological diagnosis of SARS. In consideration of possible cross-reactivity among N proteins of SARS-CoV and other coronaviruses, immunoassays using recombinant N protein in combination with S3 as antigens might improve the specificity of SARS diagnoses.     

Structure, divergence, and distribution of the CRR centromeric retrotransposon family in rice

The centromeric retrotransposon (CR) family in the grass species is one of few Ty3-gypsy groups of retroelements that preferentially transpose into highly specialized chromosomal domains. It has been demonstrated in both rice and maize that CRR (CR of rice) and CRM (CR of maize) elements are intermingled with centromeric satellite DNA and are highly concentrated within cytologically defined centromeres. We collected all of the CRR elements from rice chromosomes 1, 4, 8, and 10 that have been sequenced to high quality. Phylogenetic analysis revealed that the CRR elements are structurally diverged into four subfamilies, including two autonomous subfamilies (CRR1 and CRR2) and two nonautonomous subfamilies (noaCRR1 and noaCRR2). The CRR1/CRR2 elements contain all characteristic protein domains required for retrotransposition. In contrast, the noaCRR elements have different structures, containing only a gag or gag-pro domain or no open reading frames. The CRR and noaCRR elements share substantial sequence similarity in regions required for DNA replication and for recognition by integrase during retrotransposition. These data, coupled with the presence of young noaCRR elements in the rice genome and similar chromosomal distribution patterns between noaCRR1 and CRR1/CRR2 elements, suggest that the noaCRR elements were likely mobilized through the retrotransposition machinery from the autonomous CRR elements. Mechanisms of the targeting specificity of the CRR elements, as well as their role in centromere function, are discussed.