Characterization of the Erwinia carotovora pelB gene and its product pectate lyase.

The pelB gene encodes pectate lyase B, one of three pectate lyases identified in Erwinia carotovora EC. Pectate lyase B was purified from Escherichia coli containing the pelB gene on a recombinant plasmid. The activity of the protein was optimal at a pH of 8.3. The amino acid composition, N-terminal amino acid sequence, and C-terminal peptide sequence were determined and compared with the polypeptide sequence deduced from the DNA sequence of pelB. Purified pectate lyase B started at amino acid 23 of the predicted sequence, suggesting that a 22-amino-acid leader peptide had been removed. Pectate lyase B of E. carotovora EC and pectate lyase B of E. chrysanthemi EC16 contain 352 and 353 amino acids, respectively (N. T. Keen, S. Tanaki, W. Belser, D. Dahlbeck, and B. Staskawicz, J. Bacteriol. 168:595-606, 1986). The two proteins are 72% homologous on the basis of DNA sequence data, and 75% of the amino acids are identical.     

Structural analysis of the locus containing the human C-reactive protein gene and its related pseudogene

The gene for human C-reactive protein (CRP) is mapped within a 34-kilobase pair genomic DNA segment identified by chromosome walking through overlapping DNA fragments cloned into a lambda phage library. Within 16 kilobase pairs upstream and downstream of the locus for the authentic CRP gene, only one other sequence homologous to that for CRP could be found. Sequencing analysis indicates this sequence to be a pseudogene with 50-80% region-specific homology. Comparison of the authentic CRP gene cloned from genomic DNA libraries independently prepared from three patients indicates no difference in the 5' and 3' flanking region, promoter region, or coding sequence. Only a polymorphism in the length of the poly(GT) stretch located in the intron is observed. There appears to be only one gene locus and copy per haploid chromosome for the authentic CRP gene and its pseudogene.     

大鼠脑室注射P物质引起的血压升高与脑啡肽和β-内啡肽有关

给乌拉坦麻醉大鼠侧脑室注射P物质(SP)10μg 引起的升压效应,可被脑室注射纳洺酮15μg 部分阻断。将抗β-内啡肽抗血清、抗甲啡肽抗血清及抗亮啡肽抗血清各10μl 分别注入侧脑室预处理60min 后,再注入 SP,其升压效应明显减弱;而抗强啡肽抗血清则对其无影响。上述结果提示:大鼠脑室注射 SP 引起的升压效应,可能是通过释放β-内啡肽和脑啡肽实现的。     

肌苷对缺氧心肌跨膜电位和收缩强度的影响

本工作在正常和缺氧情况下,观察肌苷对豚鼠心室乳头肌跨膜电位和收缩强度的影响。结果表明肌苷使正常心肌细胞动作电位时间(APD_(10)、APD_(50)延长。在缺氧心肌,肌苷使细胞静息电位增大,动作电位去极化幅度增高,零期最大去极化速度加快和动作电位时间延长。肌苷增加正常心肌收缩力,使缺氧心肌收缩的衰减显著缓和,亦即使收缩功能改善,且表现剂量-依从性。肌苷对心肌细胞跨膜电位的影响提示它很可能有抗心律失常作用,特别是在缺氧心脏。肌苷对离休乳头肌收缩的影响,证明其对心肌有直接的强心作用。     

In vivo apoprotein catabolism of high density lipoproteins in copper-deficient, hypercholesterolemic rats

High density lipoprotein (HDL) apoprotein catabolism was examined in male Sprague-Dawley rats deficient in dietary copper. Twenty-four rats were randomly divided into two groups: copper-adequate (control, 5 mg of copper/kg diet) and copper-deficient (0.6 mg of copper/kg diet). After 5 weeks, animals were administered a tracer dose of iodinated HDL protein previously isolated from donor rats that were subjected to the same dietary treatments as the test animals. Copper-deficient rats exhibited a 54% increase in plasma volume and a 26% increase in HDL protein concentration above controls. Consequently, the intravascular pool of total HDL protein was increased 2-fold. The fractional catabolic rate of total HDL protein was similar between groups. However, because of the increased intravascular HDL pool in copper-deficient animals, the absolute catabolic rate was greater (640 +/- 49 micrograms/hr vs 316 +/- 12 micrograms/hr in controls). Tissue uptake of total HDL protein in copper-deficient rats tended to be greater in the kidneys, spleen, and testes compared with controls; the heart exhibited a significant 2.3-fold increase. In contrast, the catabolic rate of HDL protein in the liver and adrenal gland were not different between treatment groups. That an obligatory increase in HDL protein uptake was not observed in the liver and adrenal gland (organs which are sensitive to and can further metabolize cholesterol) suggests that these organs may be regulated, possibly contributing to the observed hypercholesterolemia in this model. These data imply that total HDL apoprotein catabolism is increased in response to the increased intravascular pool of HDL in copper-deficient rats.     

脊髓苯环立啶受体的心血管效应与去甲肾上腺素能系统

本文应用受体阻断、高效液相,6-OHDA 化学损毁神经末梢和放射自显影等多学科技术方法,探讨脊髓苯环立啶受体的心血管效应与去甲肾上腺素能神经系统的关系。结果表明,哌唑嗪、育亨宾均可对抗 ith PCP 的降压和减慢心率作用,ith PCP 产生降压和减慢心率作用时,脊髓脑脊液内 MHPG 的含量升高;用6-OHDA 损毁脊髓 NA 能神经末梢后,ith PCP的降压和减慢心率作用大为减弱,脊髓 PCP 受体密度亦同时大为降低。可以认为,脊髓内有 PCP 受体分布于 NA 能神经末梢上,促进 NA 释放或抑制 NA 重摄取,可能是脊髓 PCP 受体产生心血管抑制效应的重要机理。     

Specific binding and uptake of apolipoprotein E-free high density lipoproteins by cultured liver parenchymal cells of copper-deficient rats

The influence of copper deficiency on the binding and uptake of apolipoprotein E-free high density lipoprotein (apo E-free HDL) in cultured rat hepatic parenchymal cells was examined in this study. Male weanling Sprague-Dawley rats were randomly divided into two treatments, a Cu-adequate (7.33 mg Cu/kg diet) or a Cu-deficient (1.04 mg Cu/kg diet) group. After 7 weeks, plasma apo E-free HDL were isolated by a combination of ultracentrifugation, gel filtration, and heparin-Sepharose affinity chromatography. Parenchymal cells were isolated from collagenase perfused liver of Cu-deficient and adequate rats and cultured for 16 hours at 37 degrees C prior to incubation with iodinated apo E-free HDL from the same treatment group. Cells were incubated with 5 microg/ml(125) I-apo E-free HDL for 2, 6, or 12 hours in the presence or absence of 200 microg/ml (40-fold) excess unlabeled apo E-free HDL. Increases in specific binding at 4 degrees C and specific cell-associated uptake at 37 degrees C as a function of time were observed with cells and HDL from Cu-deficient rats. Cells were also incubated for 6 hours with 8 concentrations of (125)I-apo E-free HDL in the presence or absence of excess unlabeled HDL. Although no significant increase in specific binding was detected at 4 degrees C as a function of ligand concentration, the response tended to be higher at 5 to 15 microg HDL/ml for the Cu-deficient treatment. However, at 37 degrees C the specific cell-associated uptake was increased markedly with cells and HDL from Cu-deficient rats. The observed increases in HDL binding and uptake indicate that these processes may be enhanced in Cu-deficient rats. These data are also consistent with recent in vivo results which indicate that plasma clearance and tissue uptake of HDL are increased in Cu-deficient rats.     

蛋白和酯酶电泳在根霉鉴定上的应用

对根霉(Rhizopus)属的十个种或变种共二十四株菌的菌体可溶性蛋白和酯酶同工酶进行了电泳的研究得到对这个属分类上更多的依据.在严格控制培养,提取和电泳条件的情况下,同一株菌不同批次所得菌体蛋白电泳图谱有较好的重复性.在相同的条件下,每个种的根霉有各自特征性蛋白图谱,种内不同菌株的蛋白图谱和酯酶酶谱基本相同.特别是形态特征明显、分类地位明确的种,种内各株的图谱也较一致,如R. stolonifer;与R.circinans.在确定新变种R. delemar var. latoapicalis时,电泳图谱与R.delemar var.delema:有明显不同,起到了佐证作用.因此认为,蛋白图谱与酯酶酶谱相辅相成,在根霉种的分类中是一有效的辅助手段.     

白魔芋和花魔芋葡甘露聚糖研究

从白魔芋和花魔芋的块茎中分离纯化出两种魔芋葡甘露聚糖(Konjac Glucomannan,简称KGM),分别名为白魔芋葡甘露聚糖(aKGM)和花魔芋葡甘露聚糖(rKGM)。通过超离心、玻璃纤维纸电泳和凝胶过沪证明aKGM和rKGM都是均一的多糖。这两种多糖都由甘露糖(M)和葡萄糖(G)组成,其克分子比G/M:aKGM为1:1.69,rKGM为1:1.60,分子量前者为8.09×10~5,后者为7.37×10~5。酶水解实验和红外光谱分析说明aKGM和rKGM都是由甘露糖和葡萄糖以β-1,4-糖苷键连接的杂多糖;有O-乙酰基的特征吸收峰,说明在某些糖残基上可能有乙酰基团。