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141.
草鱼免疫应答的初步研究 总被引:11,自引:0,他引:11
研究了草鱼在不同水温条件下受抗原刺激后其中和抗体的变化。15℃培养条件下中和抗体上升缓慢,9周内滴度低于1:8;20℃时,3周后抗体可上升到1:256,最高达1:5270,而在25℃时,1周中和抗体即达到1:570,最高可达1:20000以上。并探索了从草鱼血清中提纯抗体的条件,研究其抗体的特性。草鱼血清中的抗体为大分子蛋白,容易解离为抗原性相同,分子量近似于人IgG的较小分子,含有较多的二硫键,具有类似IgM的某些特性。 相似文献
142.
143.
蝙蝠寄生长吸盘属一新种(吸虫纲:枝腺科) 总被引:2,自引:0,他引:2
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。 相似文献
144.
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。 相似文献
145.
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. 相似文献
146.
Families of metalloendopeptidases and their relationships. 总被引:10,自引:0,他引:10
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. 相似文献
147.
Nuclear totipotency of cultured rabbit morulae to support full-term development following nuclear transfer. 总被引:6,自引:0,他引:6
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. 相似文献
148.
N L Stephens C Y Seow A J Halayko H Jiang 《Canadian journal of physiology and pharmacology》1992,70(4):515-531
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. 相似文献
149.
Asthma research has recently highlighted the importance of correctly normalizing force development for purposes of comparing stiffness properties of smooth muscle between different airways, between airways at different stages of maturity, and between airways from different animal species. This problem does not exist in striated muscle where the entire tissue consists almost entirely of muscle and where cross bridges cycle at the same rate throughout a contraction when load correlation is made. In the bronchus, cross-sectional area of true muscle may constitute only 20-30% of the total tissue cross section, and load-independent cycling rate varies fourfold during the course of a contraction because of the occurrence of normally cycling and latch bridges. These features are responsible for the difficulty in force normalization in smooth muscle. Our studies indicate that normalization with respect to true muscle cell cross-sectional area (derived by quantitative morphometry of appropriate tissue transverse sections) is the most valid. This is only so, however, when it has been proved that the actomyosin content per unit weight of the different muscle tissues is the same. 相似文献
150.
Huiling Hao Yunquan Jiang S. J. Zhang Peng Zhang Rong X. Zeng Marietta Y. W. T. Lee 《Chromosoma》1992,102(Z1):S121-S127
A continuing theme of our laboraory, has been the understanding of human DNA polymerases at the structural level. We have
purified DNA polymerases delta, epsilon and alpha from human placenta. Monoclonal antibodies to these polymerases were isolated
and used as tools to study their immunochemical relationships. These studies have shown that while DNA polymerases delta,
epsilon and alpha are discrete protiens, they must share common structural features by virtue of the ability of several of
our monoclonal antibodies to exhibit cross-reactivity. A second approach we have taken is the molecular cloning of human DNA
polymerase delta and epsilon. We have cloned the DNA polymerase delta cDNA, and this has allowed us to compare its primary
structure to those of human polymerase alpha and other members of this polymerase family. Multiple sequence alignments have
revealed that human DNA polymerase delta is also closely related to the herpes virus family of DNA polymerases. In situ hybridization
has shown that the human DNA polymerase delta gene is localized to chromosome 19 q13.3–q13.4. In order to further determine
the functional regions of the DNA polymerase δ structure we are currently expressing human pol δ inE. coli and baculovirus systems. Other work in our laboratory is directed toward examining the expression of DNA polymerase δ during
the cell cycle. 相似文献