共查询到20条相似文献，搜索用时 31 毫秒
1.
Immunoassay of androgen binding protein in blood: a new approach for study of the seminiferous tubule 总被引：3，自引：0，他引：3
Androgen binding protein, a secretory product of seminiferous tubules, was isolated by means of affinity chromatography. A radioimmunoassay was developed and used to identify androgen binding protein in rat plasma. The ability to measure a testicular protein in blood provides a new method for investigation of seminiferous tubular physiology. 相似文献
2.
Plasma membrane compartmentalization in yeast by messenger RNA transport and a septin diffusion barrier 总被引：2，自引：0，他引：2
Asymmetric localization of proteins plays a key role in many cellular processes, including cell polarity and cell fate determination. Using DNA microarray analysis, we identified a plasma membrane protein-encoding mRNA (IST2) that is transported to the bud tip by an actomyosin-based process. mRNA localization created a higher concentration of IST2 protein in the bud compared with that of the mother cell, and this asymmetry was maintained by a septin-mediated membrane diffusion barrier at the mother-bud neck. These results indicate that yeast creates distinct plasma membrane compartments, as has been described in neurons and epithelial cells. 相似文献
3.
笋用雷竹林引种后新立竹生长规律与经营密度研究 总被引：2，自引：0，他引：2
通过对雷竹引种后新立竹生长进行实地调查,结果表明：母竹引种后新立竹数目、胸径、树高、枝下高及与母竹距离有随着母竹年龄增大而增长的趋势。新立竹数目与新立竹年龄(相对母竹而言)之间及新立竹与母竹平均距离之间均存在函数关系。雷竹引种后各年间新立竹数目、胸径、树高、枝下高及新立竹与母竹距离的差异均达到极显著性水平。年龄对雷竹林分平均单株枝重、枝长、叶数／枝、叶重／枝、叶面积的影响均没有达到显著性水平。钩梢处理对平均均叶数／枝、平均叶重／枝及平均单株枝重的影响达到显著性水平或极显著性水平。雷竹株数按径阶分布服从正态分布。雷竹冠幅、胸径、树高及枝下高等生长因子之间存在相关关系。根据雷竹鞭侧芽分化为岔鞭规律以及新立竹年龄与母竹距离的关系可以确定雷竹初植密度,由树冠重叠系数及其平均径阶决定笋用雷竹林经营密度。 相似文献
4.
Structure and function of lipopolysaccharide binding protein 总被引：172，自引：0，他引：172
R R Schumann S R Leong G W Flaggs P W Gray S D Wright J C Mathison P S Tobias R J Ulevitch 《Science (New York, N.Y.)》1990,249(4975):1429-1431
The primary structure of lipopolysaccharide binding protein (LBP), a trace plasma protein that binds to the lipid A moiety of bacterial lipopolysaccharides (LPSs), was deduced by sequencing cloned complementary DNA. LBP shares sequence identity with another LPS binding protein found in granulocytes, bactericidal/permeability-increasing protein, and with cholesterol ester transport protein of the plasma. LBP may control the response to LPS under physiologic conditions by forming high-affinity complexes with LPS that bind to monocytes and macrophages, which then secrete tumor necrosis factor. The identification of this pathway for LPS-induced monocyte stimulation may aid in the development of treatments for diseases in which Gram-negative sepsis or endotoxemia are involved. 相似文献
5.
Yun MK Wu Y Li Z Zhao Y Waddell MB Ferreira AM Lee RE Bashford D White SW 《Science (New York, N.Y.)》2012,335(6072):1110-1114
The sulfonamide antibiotics inhibit dihydropteroate synthase (DHPS), a key enzyme in the folate pathway of bacteria and primitive eukaryotes. However, resistance mutations have severely compromised the usefulness of these drugs. We report structural, computational, and mutagenesis studies on the catalytic and resistance mechanisms of DHPS. By performing the enzyme-catalyzed reaction in crystalline DHPS, we have structurally characterized key intermediates along the reaction pathway. Results support an S(N)1 reaction mechanism via formation of a novel cationic pterin intermediate. We also show that two conserved loops generate a substructure during catalysis that creates a specific binding pocket for p-aminobenzoic acid, one of the two DHPS substrates. This substructure, together with the pterin-binding pocket, explains the roles of the conserved active-site residues and reveals how sulfonamide resistance arises. 相似文献
6.
The binding constants and the number of binding sites for insulin, glucagon, epinephrine, cyclic adenosine monophosphate, and calcium ions for the plasma membrane of rat liver were determined by Scatchard plots. The plots are biphasic or multiphasic, an indication of at least two types of binding sites for each ligand. At least three types of binding sites were found for insulin. In the concentration range of 10(-6) to 10(-8) molar, glucagon, epinephrine, and hydro-cortisone increased calcium ion binding to the plasma membrane, whereas insulin decreased this binding. At hormone concentrations of 10(-6) to 10(-7) molar, glucagon was the most effective in increasing calcium binding, but at a hormone concentration of 10(-8) molar, hydrocortisone was the most effective in stimulating calcium binding. Adenosine triphosphate reversed the effect of insulin and inhibited the effect of the other hormones. These studies suggest a relation between hormones and calcium with respect to membrane structure and function. 相似文献
7.
采用组织化学及生物化学分析方法，研究了重金属污染区水稻籽实中 Pb的分布及其结合形态。结果表明， Pb在籽实各形态结构中的浓度分布不均匀，胚和种皮中的浓度显著高于胚乳和颖壳。就 Pb总量而言，胚乳中的比例最高； Pb在籽实的主要营养成分中，以蛋白质中的分布比例最高，可达 83％，脂肪中甚微；在 4种主要类型蛋白质中，以谷蛋白和球蛋白中的比例较高。凝胶层析的结果表明，蛋白质－ Pb结合体的表观分子量为 54.5KD,蒸煮及体外消化酶的处理下，前者易分解，出现分子量较小的结合物。 相似文献
8.
为研究甘加型藏羊(Ovis arise)发情周期血浆孕激素(P4)的分泌及孕激素受体(Progesterone receptor, PGR)在HPO轴中的表达，分析其在藏羊繁殖活动中的调控作用，本研究应用酶联免疫吸附试验、蛋白免疫印迹法、实时荧光定量和免疫组织化学染色法检测甘加型藏羊发情周期血浆中孕酮含量的动态变化、HPO组织中PGR mRNA及其蛋白的表达和组织分布。结果显示：1)甘加型藏羊发情周期血浆孕酮呈波动式和脉冲式分泌，在间情期达到最高峰值，发情期最低，二者差异显著(P<0.05)。2)PGR mRNA及其蛋白在HPO组织中均有表达；下丘脑中，PGR mRNA及其蛋白相对表达量在间情期最高，各时期之间差异显著(P<0.05);垂体中，PGR mRNA表达量在发情后期达到最高，显著高于发情前期和间情期(P<0.05),发情前期蛋白相对表达量高于其他时期；卵巢中，PGR mRNA在发情期最高，与间情期差异显著(P<0.05),蛋白表达水平在发情前期最高。3)PGR免疫阳性反应产物表达在下丘脑神经胶质细胞和大神经元胞体中，腺垂体嗜酸性细... 相似文献
9.
生长早期泰和鸡与AA鸡血清生长激素水平及生长激素结合蛋白活性的比较 总被引：9，自引：0，他引：9
比较泰和鸡和ＡＡ（Ａｒｂｏｒ Ａｃｒｅｓ）肉鸡血清生长激素（ＧＨ）含量和生长激素结合蛋白（ＧＨＢＰ）的结合活性,发现两品种鸡出雏时血清ＧＨ水平均较低,５日龄时ＧＨ均有显著上升（Ｐ＜０．０１）。此后泰和鸡保持上升趋势,在３５日龄ＧＨ达到最高值;而ＡＡ鸡在５日龄后血清ＧＨ水平上升幅度较小,日龄间差异不显著。１日龄和３５日龄时,泰和鸡血清ＧＨ水平显著高于同日龄的ＡＡ肉鸡,与两者体重的差异刚好相反。血液Ｇ 相似文献
10.
Glucocorticoid receptor-like antigen in lymphoma cell membranes: correlation to cell lysis 总被引：12，自引：0，他引：12
B Gametchu 《Science (New York, N.Y.)》1987,236(4800):456-461
S-49 mouse lymphoma cells undergo lysis when treated with glucocorticoids; the mechanism of this effect is not understood. A protein was detected in the plasma membrane of these cells by means of direct immunofluorescent labeling with a monoclonal antibody to the soluble glucocorticoid receptor. Cellular heterogeneity in the content of this glucocorticoid receptor-like molecule was evident. By immunoadsorption to antibody-coated tissue culture plates, the cells were separated into populations positive (100%) and depleted (38%) for this membrane antigen. Gel electrophoresis, specific immunoblot, and autoradiographic (binding of [3H]dexamethasone mesylate) analysis of the membrane proteins from the membrane antigen-positive group revealed multiple protein bands ranging in size from 85 to 145 kilodaltons. Furthermore, comparison of the glucocorticoid sensitivity of these groups of cells showed complete lysis of the membrane antigen-positive cells and only partial lysis of the antigen-deficient group, which suggests that the lysis response of cells to glucocorticoids is mediated by a glucocorticoid receptor-like molecule located in the plasma membrane. 相似文献
11.
The cross-linking of lysozyme by reaction with phenol-2,4-disulfonyl chloride has been effected. The cross-linked protein retained enzymatic activity, has approximately the same molecular weight as native lysozyme, and has essentially the same conformation as native lysozyme as judged by optical rotatory dispersion analysis. The positions of sulfonylation were assigned by a standard degradation sequence; the presence of sulfonamide bonds was confirmed by infrared spectroscopy. Cross-links may thus be introduced without incurring major structural changes in the protein, and certain intramolecular distances that are allowed in the active enzyme may be deduced. 相似文献
12.
为探索水环境因子对磺胺类抗性基因传播机制的影响,以磺胺类抗性基因Sul1为目的基因,采用绝对定量PCR技术,考察了pH、盐度、腐植酸、总氨氮和活性磷酸盐对Sul1含量的影响。研究结果表明,Sul1含量在pH 6~8时最高,而在酸性(pH 3~5)或碱性(pH 9~10)条件下均显著降低,表现出明显的抑制作用(P0.05)。Sul1含量随着盐度或腐植酸浓度升高而降低,呈显著的抑制作用(P0.05);总氨氮或活性磷酸盐对Sul1含量的影响表现为高浓度抑制、低浓度促进作用。当总氨氮或活性磷酸盐的浓度低于0.05 mg·L~(-1)时,Sul1含量显著增加(P0.05);而当浓度升高到1 mg·L~(-1),Sul1的含量显著降低(P0.05)。上述结果表明,水环境因子会影响磺胺类抗性基因Sul1的存在及分布。 相似文献
13.
14.
The insulin receptor contains a calmodulin-binding domain 总被引：3，自引：0，他引：3
Substantial evidence suggests that calcium has a pivotal role in regulating the initial events through which insulin alters plasma membrane metabolism. Because binding of insulin to its receptor represents the initial site of insulin action in the plasma membrane, studies were undertaken to determine whether the insulin receptor is a calmodulin-binding protein. Preparations enriched in the insulin receptor and calmodulin-binding proteins were isolated from detergent-solubilized rat adipocyte membranes by chromatography with wheat germ agglutinin agarose and calmodulin-conjugated Sepharose, respectively. Substantial purification of a manganese-dependent, insulin-sensitive phosphoprotein of 95K identified as the beta subunit of the insulin receptor was accomplished. Binding and photocovalent cross-linking of iodine-125-labeled calmodulin to these affinity-purified preparations and to isolated plasma membranes, followed by immunoadsorption with insulin receptor antibodies bound to protein A Sepharose, resulted in significant purification of a binding complex of 110K to 140K. These results indicate that the adipocyte insulin receptor or a polypeptide closely associated with the receptor is a calmodulin-binding protein. 相似文献
15.
研究茶叶中磺胺嘧啶(SDZ)、磺胺二甲嘧啶(SM2)、磺胺甲噁唑(SMZ)3种磺胺类抗生素(SAs)的检测方法,优化了提取方法,确定以甲醇为提取剂,超声波提取10 min,浓缩仪浓缩,衍生化后用高效液相色谱-荧光检测器测定的方法。添加回收实验结果表明,茶叶中SDZ、SM2和SMZ的添加回收率为70.5%~131.1%,在茶叶中的检出限为0.002~0.003 mg·kg-1,该方法的灵敏度、精确度、准确度均较高。对安徽省13个茶叶样品检测结果表明,3种SAs均未检出。 相似文献
16.
Egg white proteins are one of the major allergens. The objective of this study was to investigate the effect of Aspergillus oryzae cultivation on IgE binding ability of egg white proteins. Effect of A. oryzae on egg white proteins was determined using ninhydrin method, SDS-PAGE, ELISA, fluorescence FITC labeling, MALDI-TOF-MS and LC-MS/MS analysis. Adding mycelium of A. oryzae ATCC 1011 and 16868 substantially reduced the IgE binding ability of acidified egg white after 24 h incubation. The binding capacity of egg white proteins to IgE in plasma from four egg allergy patients was almost completely lost after incubation with mycelium of ATCC 16868. Results from SDS-PAGE, free amino acid analysis, MALDI-TOF-MS and LC-MS/MS indicated that there was no substantial protein degradation during incubation. Therefore, the reduction of IgE binding ability of egg white proteins during A. oryzae treatment was probably due to a loss of ~1700 Da mass including a fragment of the ovomucoid N terminus. 相似文献
17.
18.
紫鸭跖草细胞中铜的分配和化学形态特征研究 总被引：1，自引：0，他引：1
[目的]为从Cu在组织细胞中的分配特征和结合形态的角度揭示紫鸭跖草超积累Cu的机理。[方法]利用差速离心技术研究Cu在紫鸭跖草中的亚细胞分配特征,并运用化学试剂顺序提取法和酶解法研究Cu在紫鸭跖草根和叶中的赋存形态。[结果]根部Cu的分布位点主要是细胞壁,占根部全Cu的1/3以上;而叶部以叶绿体中的Cu占叶片全Cu的比例较大,约为1/4。在高浓度Cu处理或处理时间延长的情况下,根细胞中Cu向细胞壁的分配增多,向质体中的分配减少;而叶细胞中Cu向叶绿体中的分配增多,向细胞壁的分配减少。叶片中Cu主要与氨基酸、小分子色素、蛋白质、多糖等结合;而根部Cu主要与纤维素、膜结合蛋白等细胞壁物质结合。[结论]Cu在细胞内的分配和存在形态可能是紫鸭跖草超积累Cu的重要机理之一。 相似文献
19.
Maternal and environmental influences on the adrenocortical response to stress in weanling rats 总被引：6，自引：0，他引：6
S Levine 《Science (New York, N.Y.)》1967,156(772):258-260
Handling rat pups either for 10 or 20 days after birth resulted in a reduction of adrenocortical steroids in the plasma at weaning after the pups were exposed to novel stimuli as compared with controls that were not handled. Nonhandled offspring of mothers which had been handled in infancy also show a reduction in plasma steroids in response to novel stimuli when compared to nonhandled weanling rats of nonhandled mothers. Handling of the offspring when they are infants appears to counteract the influence of the experience of the mother during her infancy. 相似文献
20.
In the experiments described the following observations have been made: (1) The toxic and diabetogenic action of alloxan increases in rats fed a low protein diet and even more so in the case of a high lard or ox fat diet. (2) The action of these fat diets was corrected by the addition of methionine, thiouracil, or coconut oil, but there was no modification either by addition of choline or sulfonamide or by increase in the protein proportion. (3) In rats fed other high fat diets (olive oil, butter) the actions of alloxan were not modified, but there was a slight diminution when high oleomargarine or corn oil diets were fed. However, complete protection was observed when a high coconut oil diet was administered. (4) The unfavorable effect of the high lard diet was observed also on the initiation and evolution of diabetes due to subtotal pancreatectomy. Contrarily, feeding a high protein diet and especially treatment with thiouracil had a favorable effect. (5) Diabetes appeared first in subtotal pancreatectomized rats which were overfed, then in those which ate ad libitum, and finally in those which were underfed. Diabetes appeared in rats fed a single meal before it did in those eating the same amount of food divided into three meals. 相似文献