安徽省颖上县小张庄种植业子系统生态功能分析

小张庄村位于淮北平原南部,常年平均气温15.1℃,光合作用时间221天,降水量905mm,但降水分配不均,加上地势低平,常有旱涝灾害发生。全村有耕地约324ha,以砂姜黑土为主,土壤基本性状良好,但生产力水平不高。为了从根本上改变农业低产面貌,     

蝙蝠寄生长吸盘属一新种（吸虫纲：枝腺科）

本文论述长吸盘属Longitrema一新种——杭州长吸盘吸虫,新种Longilremahangz-houensissp.Nov.,模式标本采自浙江省桐庐县大足鼠耳蝠的小肠中。对新种与近似种梨形长吸盘吸虫Longitremapiriforme(Yamaguti,1939)Chen,1954作了详细的描述。     

阿胶,新阿胶,黄明胶,马皮胶,杂皮胶的质量对比研究：Ⅰ.氨基酸分析

本文用835-50型氨基酸自动分析仪测定了阿胶、新阿胶、黄明胶、马皮胶和杂皮胶中游离氨基酸和总氨基酸的含量,并计算出游离氨基酸、总氨基酸按侧链基团分类和按医药用途分类的相对含量。结果表明,各种氨基酸含量一般以驴皮胶为较高,但与其他几种胶比较并无显著差异,似可以猪皮马皮、牛皮代替驴皮。这也说明,单从氨基酸的含量来鉴别胶的种类和质量似乎不可行。     

组织型纤溶酶原激活剂的发光分析法及其应用

 本文建立了组织型纤溶酶原激活剂(t-PA)活力的发光固相测定方法。用氨基乙基丁基异鲁米诺(ABEI)标记纤维蛋白原(Fg),在一定条件下,t-PA作用于固相(包被ABEI-Fg),产生纤维蛋白的降解产物。测定可溶性降解产物的发光强度,即能计算t-PA活性。该方法的标准曲线范围对t-PA为0.156IU/mL～40IU/mL。灵敏度可达0.156IU/mL。回收率为98.6％(n=27)。批内批间变异系数分别为6.6％及10.3％。该方法曾用于检测细胞培养液中提取t-PA样品及t-PA基因表达时培养液中t-PA的活性。也曾用于检测从组织中纯化t-PA样品及血浆中t-PA活性的测定。文中讨论了该方法与其它方法优缺点的比较。     

大鼠肾脏组织cDNA文库的制备和葡萄糖转运蛋白cDNA克隆的筛选

 大鼠的肾脏组织经匀浆后,提取纯化总RNA和mRNA合成cDNA,进行甲基化,加人工接头,最后连入载体(λgt11)和外壳蛋白包装步骤制成肾脏组织的cDNA文库。插入载体的cDNA长度为0.5kb到8kb之间。经反复稀释,测定出该文库的效价为1.5×10~7pfu/mL。     

A novel difucosylated neutral glycosphingolipid from the eggs of the sea urchin, Hemicentrotus pulcherrimus: I. Purification and structural determination of the glycolipid.

A novel fucose-containing neutral glycosphingolipid (GL-5) was purified from the eggs of the sea urchin, Hemicentrotus pulcherrimus. The chemical structure was determined to be Fuc alpha 1-3GalNAc beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-4Glc beta 1-1Cer by methylation analysis, partial acid hydrolysis, fast atom bombardment mass spectrometry, and proton nuclear magnetic resonance spectroscopy. The unique characteristics of GL-5 are that: the reducing terminal disaccharide portion is not Gal beta 1-4Glc but GlcNAc beta 1-4Glc; it includes a GalNAc beta 1-4GlcNAc sequence and a Fuc-GalNAc linkage; the defucosylated core is a novel trisaccharide chain; and the sugar structure is one of the smallest ever characterized for a difucosylated glycolipid. The major fatty acids were 22:1 and 22h:1, and about 30% of the total acids was 2-hydroxylated. All the long-chain bases were phytosphingosines, of which about 90% was n-t18:0. The similarity of the ceramide moiety to that of glucosylceramide from the same eggs [Kubo, H. et al. (1992) J. Biochem. 111, 726-731] suggests a close biosynthetic relationship between GL-5 and the glucosylceramide.     

Families of metalloendopeptidases and their relationships.

Crystal structures available for four metalloendopeptidases have revealed zinc ligands for these enzymes. New sequence information has made it possible to compare the primary structures of the zinc-binding site in metalloendopeptidases. A scheme based on the zinc-binding site is proposed to classify metalloendopeptidases into five distinct families: thermolysin, astacin, serratia, matrixin, and snake venom metalloproteinases. Two histidines and one glutamate are zinc-ligands in the thermolysin family. Three histidines and one tyrosine are zinc ligands in the other four families, which are further distinguished by the identity of the residue following the third histidine and by the environment surrounding the tyrosine.     

Nuclear totipotency of cultured rabbit morulae to support full-term development following nuclear transfer.

The rabbit was used as a model for nuclear transfer. A critical step in nuclear transfer is oocyte activation, which was evaluated in this research. Optimal field strength of an electric stimulus for activation was examined. A significantly higher activation rate in all criteria tested was achieved when oocytes were activated electrically with a field strength of 2.4 kV/cm versus 1.2 or 1.8 kV/cm. Also, electrical stimulation with combined alternating current (AC) and direct current (DC) was superior to DC stimulation alone for activation. In another study involving 586 oocytes, exposure of oocytes to cytochalasin B for 1 h followed by activation with electrical stimulation significantly improved development of the oocytes to blastocyst stage compared to oocytes without cytochalasin B pre-exposure (38% vs 26%, p less than 0.05). Cytochalasin B exposure alone (control), however, had no effect on activation. Exposing oocytes to activation medium without electrical stimulation also activated some oocytes. In the nuclear transfer experiment, blastomeres from 8-cell embryos cultured for 20-24 h to the 32-64-cell stage were used as nuclear donor cells. Of 491 oocytes used, 459 (93%) survived the enucleation and fusion procedure, 370 (81%) fused, and 284 (77%) developed into 2-4-cell embryos. A total of 243 of these 2-4-cell embryos were transferred to 15 pseudopregnant recipients and produced 8 young (3%). Although the efficiency is low, this study demonstrated that rabbit morulae cultured for 20-24 h to the 32-64-cell stage as nuclear donors for transfer remain totipotent.     

The biophysics and biochemistry of smooth muscle contraction.

In this review the biophysics and biochemistry of smooth muscle contraction are dealt with. We describe a new model for the study of bronchial smooth muscle, which facilitates study of cellular contractile mechanisms. A new concept emerging is that study of steady-state mechanical parameters such as maximal isometric force (Po) velocity is inadequate because two types of crossbridges (normally cycling (NBR) and latch) seem to be sequentially active during smooth muscle contraction. Thus quick-release techniques are required to characterize the force-velocity properties of the two types of bridges. Pathophysiological processes that affect the muscle's shortening ability seem to affect the early NBRs only. With respect to maximal shortening capacity of the smooth muscle, the role of loading is very important. The differences between isotonic, elastic, and viscous loading are considerable. Ultimately, the time course and magnitude of loading should exactly resemble that operative in vivo. Once again, it is the characteristic of loading in the early phase of contraction that is crucial, as most of the shortening in smooth muscle occurs early in the contraction. While the maximum force developed by smooth muscle per unit cross-sectional area is the same as for striated muscle, the velocity is 50 times less. The properties of the series and parallel elastic elements of smooth muscle are described. The latter, when in compression mode, acts as an internal resistance to shortening and probably limits it. Isotonic relaxation has therefore not been studied in smooth muscle. We have developed a shortening parameter that is independent of the load on the muscle and of the initial length of the muscle's contractile element. We report the novel observation that isotonically relaxing smooth muscle reactivates itself, resulting in terminal slowing of the relaxation process. With respect to the biochemistry of smooth muscle contraction, contractile (actin isoforms, myosin heavy and light chains and their isoforms), regulatory (calmodulin-4 Ca2+, myosin light chain kinase, myosin light chain and its phosphorylation, tropomyosin, caldesmon, and calponin), and cytoskeletal (chiefly desmin and vimentin) proteins are discussed. While the kinase activates the contractile system, caldesmon and calponin modulate the activity downward. The cytoskeletal proteins desmin, vimentin, and alpha-actinin could constitute the muscle cell's internal resistor.