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91.
92.
Mutations at the flügellos (fl) locus in Bombyx mori give rise to wingless pupae and moths. To understand the developmental steps responsible for the fl wing defect, we compared the morphological changes and protein synthesis profiles between fl and wild-type (WT) wing discs during larval development. Morphologically, the four wing discs in the fl homozygote larva developed normally at least until the fourth instar, but they were slightly smaller than those of the WT.
After the last larval ecdysis, wing epithelial invagination and tracheal migration into the lacunar spaces evidently occurred
in the WT wing discs. However, there was no apparent morphological change in fl discs through the fifth instar. The fl wing discs cultured in medium containing 20-hydroxyecdysone (20E) did not grow and develop, although the WT wing discs extended
and differentiated under the same conditions. A comparison of protein synthesis in the wing discs revealed that several bands
were differentially expressed between the fl and WT. A 41-kDa band expressed abundantly from larval to pharate pupal stages in the WT wing discs was rarely observed in
fl discs. Furthermore, in vitro culture studies showed that the 41-kDa protein was induced by 20E and specifically synthesized
in WT wing discs after the wandering stage, but not in fl discs. The wing-specific protein synthesis and morphogenesis in fl wing discs may be blocked due to aberrant expression of the fl gene.
Received: 6 November 1996 / Accepted: 5 February 1997 相似文献
93.
Avram Hershko 《Current opinion in cell biology》1997,9(6):788-799
Selective degradation of cyclins, inhibitors of cyclin-dependent kinases and anaphase inhibitors is responsible for several major cell cycle transitions. The degradation of these cell cycle regulators is controlled by the action of ubiquitin—protein-ligase complexes, which target the regulators for degradation by the 26S proteasome. Recent results indicate that two types of multisubunit ubiquitin ligase complexes, which are connected to the protein kinase regulatory network of the cell cycle in different ways, are responsible for the specific and programmed degradation of many cell cycle regulators. 相似文献
94.
载脂蛋白E(ApoE)与迟发的家族性及孤发性阿尔茨海默(Alzheimer)病密切相关. 氯喹慢性中毒可诱发某些肌病理改变, 出现β淀粉样蛋白(βAP)与tau蛋白等的沉积, 与Alzheimer脑中见到的病理改变类似. 为分析这一改变的机制, 用逆转录结合多聚酶链反应技术(RT-PCR)对氯喹处理的大鼠肌肉中ApoE表达的改变进行了研究. 在PCR定量中采用了一种稳定表达的内源性甘油醛-3-磷酸脱氢酶mRNA作为内部参照. PCR扩增在很宽的循环数范围内成线性, 且靶mRNA与参照mRNA的扩增效率相当. 氯喹处理后大鼠肌肉中ApoE mRNA的表达从第6周开始增加, 第8周后超过对照组的20多倍. 结果提示, ApoE在氯喹慢性中毒所致的大鼠肌病理改变中发挥某些作用. 相似文献
95.
枯草杆菌蛋白酶E的156和165位突变 总被引:1,自引:0,他引:1
应用定点突变方法,在M222A突变的枯草杆菌蛋白酶E基因上进行E156S和V165I定点突变. 将突变基因插入大肠杆菌-枯草杆菌穿梭质粒pBE-2中,在碱性和中性蛋白酶缺陷型的枯草杆菌DB104中进行表达,得到突变种(M222A,E156S)和(M222A,E156S,V165I)蛋白酶E. 性质测定表明,E156S突变使蛋白酶比活力增加90%,并不影响酶的热稳定性和抗氧化性. 而V165I突变使蛋白酶比活力降低. 相似文献
96.
97.
The synthetic antibody model “M41” was rationally designed with a binding site complementary to chicken egg white cystatin as the prescribed antigen. In order to permit comparison between the computer model and an experimental three-dimensional structure of the artificial protein, its X-ray crystallographic analysis was pursued. For this purpose, M41 was expressed as a recombinant Fab fragment in E. coli by medium cell density fermentation employing the tightly regulated tetracycline promoter. The Fab fragment was efficiently purified via a His-6 tail fused to its heavy chain and immobilized metal affinity chromatography. To raise the chances for the productive formation of crystal packing contacts, three versions of the Fab fragment were generated with differing constant domains. One of these, the variant with murine CK and CH 1γ1 domains, was successfully crystallized by microseeding in a sitting drop. The orthorhombic crystals exhibited symmetry of the space group P212121 with unit cell dimensions a = 104.7 Å, b = 113.9 Å, c = 98.8 Å and diffracted X-rays to a nominal resolution of 2.5 Å. © 1995 Wiley-Liss, Inc. 相似文献
98.
Astrid Zimmermann Anke Haina Ute Gröschel-Stewart 《Development genes and evolution》1995,204(4):271-275
The development of the autonomic ganglia of Auerbach's plexus and gizzard smooth muscle was studied in chicken embryos. Nervous system and smooth-muscle-specific antibodies were employed in immunofluorescence stainings on tissue sections to investigate the temporal and spatial frame of neural and muscular differentiation in relation to each other. Subserosal clusters of neural cells were clearly demonstrable at embryonic day 5 (ED5), the earliest stage analysed, with the monoclonal antibody El (SGIII-1). Fine nerve fibres (ED6) and, later, large axon bundles projecting from subserosal neuron clusters towards the lumen were followed and found to reach the luminal border by ED11. Already in early development the area of the future laminar tendons on the ventral and dorsal surface of the gizzard was devoid of neuroblasts, and nerve fibres were not extending to the muscle-tendon borderline until ED16. Double stainings with antibodies to smooth muscle myosin (SMM) and El revealed that SMM expression, taken as an indicator for muscle differentiation, followed neural growth. It was first detectable in close apposition to the differentiating neuroblasts in the caudal and cranial portion of the gizzard at ED6. With further development, myosin expression proceeded inward towards the lumen in a wave which followed the ingrowth of E1-positive nerve fibres from the prospective Auerbach plexus. Neuromuscular differentiation deviated from this pattern in the lateral tendon area where nerve growth was delayed and myosin expression preceeded the arrival of E1-positive nerve fibres. The findings suggest that the gizzard could serve as a model system for the analysis of potential early nervous system imprints on smooth premuscle mesenchyme differentiation. 相似文献
99.
C.A. Rebeiz A. Montazer-Zouhoor H.J. Hopen S.M. Wu 《Enzyme and microbial technology》1984,6(9):390-396
A new approach to the design of conceptually and phenomenologically new herbicides is described. It involves the joint utilization of tetrapyrrole precursors, such as δ-aminolaevulinic acid (a biodegradable amino acid) and activators of the chlorophyll biosynthetic pathway, such as 2,2′-dipyridyl, in order to induce treated plants to biosynthesize and accumulate massive amounts of tetrapyrrole intermediates of the chlorophyll biosynthetic pathway in the dark (i.e. at night). During the subsequent light period (daylight) the accumulated tetrapyrroles act as potent photodynamic sensitiziers, which in turn result in the death of susceptible plants in a matter of hours. We have therefore proposed to name herbicides that act via this mechanism as photodynamic herbicides, or more pictorially as laser herbicides. From a limited survey of agricultural plant and weed species it appears that photodynamic herbicides exhibit a very pronounced organ, age and species-dependent selectivity. For example, dicotyledonous weeds such as mustard, red-root pigweed, common purslane and lambsquarter are very susceptible while monocotyledonous plants such as corn, wheat, barley and oats are not. The biochemical basis of this selectivity seems to lie, among other things, in the rates of tetrapyrrole turnover and in a differential enhancement by the applied chemicals of the monovinyl and divinyl tetrapyrrole biosynthetic pathways in the various species. A survey of various groups of chemicals (herbicides and other selected biochemicals) that are likely to exhibit photodynamic herbicidal properties is currently under investigation. 相似文献
100.
Matthew J. Friedman Ante M. Krstulović Henri Colin Georges Guiochon Kathleen Pajer 《Analytical biochemistry》1984,142(2):480-486
Described in this paper is a rapid, isocratic assay for serum indole-3-acetic acid (IAA). The sample preparation involves only protein precipitation using sulfosalicylic acid, and the sensitivity of amperometric detection is in the picogram range. The chromatographic analysis time is approximately 4 min. The devised method was used for a longitudinal study of IAA levels in serum samples from control subjects and newly abstinent alcoholics. Dietary variations were eliminated by administering a 2.0-g loading dose of L-Trp to all subjects investigated. The results are presented in the form of cumulative frequency polygons. Preliminary data indicate no differences in IAA levels between newly abstinent alcoholics and control subjects. 相似文献