Reduced orthostatic tolerance following 4 h head-down tilt

The cardiovascular responses to a 10-min 1.22 rad (70 degrees) head-up tilt orthostatic tolerance test (OST) was observed in eight healthy men following each of a 5-min supine baseline (control), 4 h of 0.1 rad (6 degrees) head-down tilt (HDT), or 4 h 0.52 rad (30 degrees) head-up tilt (HUT). An important clinical observation was presyncopal symptoms in six of eight subjects following 4 h HDT, but in no subjects following 4 h HUT. Immediately prior to the OST, there were no differences in heart rate, stroke volume, cardiac output, mean arterial pressure and total peripheral resistance for HDT and HUT. However, stroke volume and cardiac output were greater for the control group. Mean arterial pressure for the control group was less than HDT but not HUT. Over the full 10-min period of OST, the mean arterial pressure was not different between groups. Heart rate increased to the same level for all three treatments. Stroke volume decreased across the full time period for control and HDT, but only at 3 and 9 min for HUT. There was a higher total peripheral resistance in the HDT group than control or HUT. The pre-ejection period to left ventricular ejection time ratio was less in HDT than for control or HUT groups. These data indicate a rapid adaptation of the cardiovascular system to 4 h HDT that appears to be inappropriate on reapplication of a head to foot gravity vector. We speculate that the cause of the impaired orthostatic tolerance is decreased tone in venous capacitance vessels so that venous return is inadequate.     

Genomic DNA sequence for human C-reactive protein

The gene for the prototype acute phase reactant, C-reactive protein, has been isolated from two lambda phage libraries containing inserted human DNA fragments using synthetic oligonucleotide probes. Nucleotide sequence analysis indicates that after coding for a signal peptide of 18 amino acids and the first two amino acids of the mature protein, there is an intron of 278 base pairs followed by the nucleotide sequence for the remaining 204 amino acids. The intron is unusual in that it contains on the positive strand a poly(A) stretch 16 nucleotides long and a poly(GT) region 30 nucleotides long which could adopt the Z-form of DNA. The nucleotide sequence reported here confirms the amino acid sequence of mature C-reactive protein as originally reported except that it codes for an additional 19 amino acids beginning at position 62. Thus DNA sequence analysis predicts that the mature protein consists of 206 amino acids rather than 187 as originally reported. The mRNA cap site is located 104 nucleotides from the start of the signal peptide and there is a 3' noncoding region 1.2 kilobase pairs in length. The gene has a typical promoter containing the sequences TATAAAT and CAAT 29 and 81 base pairs upstream, respectively, of the cap site.     

An improved DNA sequencing strategy

A modification of Hong's systematic DNA sequencing strategy is described. The original procedure has been simplified and transfectant yield increased. After DNase I limited cleavage in the presence of Mn2+, the single-cut linear DNA does not have to be separated from supercoiled or open circular DNA on an agarose gel. After ligation, the DNA is digested with a second restriction endonuclease for which a unique cleavage site resides between the insert and the first restriction endonuclease cutting site. The original intact DNA is linearized whereas the deleted subclone is not. The background is decreased to an undetectable level. This DNA sequencing strategy was tested on a 1.4-kb DNA fragment containing the araC regulatory gene from Erwinia carotovora. A set of subclones sufficient to sequence the fragment on both strands was produced in 2 days and the yield was at least 60-fold higher than in the original protocol.     

Regeneration of the arterial wall in microporous,compliant, biodegradable vascular grafts after implantation into the rat abdominal aorta

Summary The ultrastructure of a new type of vascular graft, prepared from a mixture of polyurethane (95 weight %) and poly-L-lactic acid (5 weight %), was examined six weeks after implantation into the abdominal aorta of rats. These microporous, compliant, biodegradable, vascular grafts function as temporary scaffolds for the regeneration of the arterial wall.Smooth muscle cells, covering the grafts, regenerated a neo-media underneath an almost completely regenerated endothelial layer (neo-intima). These smooth muscle cells varied in morphology from normal smooth muscle cells to myofibroblasts. They were surrounded by elastic laminae and collagen fibers.Macrophages, epithelioid cells, multinucleated giant cells, fibroblasts and capillaries were present in the disintegrating graft lattices. The epithelioid cells and multinucleated giant cells engulfed polymer particles of the disintegrating grafts.The regeneration of the endothelial and smooth muscle cells is similar to the natural response of arterial tissue upon injury. The presence of macrophages, epithelioid cells, multinucleated giant cells, fibroblasts and capillaries in the graft lattices resembles the natural response of tissue against foreign body implants. Both of these responses result in the formation of a neo-artery that possesses sufficient strength, compliance and thromboresistance to function as a small caliber arterial substitute.Supported by Grant nr. 82.042 from the Dutch Heart Foundation     

Cloning of the pectate lyase genes from Erwinia carotovora and their expression in Escherichia coli

A hybrid cosmid coding for pectate lyase (PL) activity was identified from an Erwinia carotovora genomic library by an immunological screening method. A 7-kb DNA fragment was identified which codes for three proteins identical in size to proteins with PL activity purified from E. carotovora culture supernatants. The three proteins had apparent Mrs of 41, 44 and 44 X 10(3) as estimated by SDS-PAGE. None of the PLs were exported from Escherichia coli strain HB101 but all were found in the periplasmic space. Plant tissue was macerated by the PLs made in E. coli.     

The araBAD operon of Salmonella typhimurium LT2. I. Nucleotide sequence of araB and primary structure of its product, ribulokinase

Hybrid plasmids containing the araBAD operon of Salmonella typhimurium LT2 were characterized by Southern blot and genetic analyses. The nucleotide sequence of araB was determined. The araB gene product, ribulokinase (EC 2.7.1.16), was purified and the results of amino acid composition analysis and partial amino acid sequence are in agreement with predictions from the DNA sequence. Ribulokinase is 569 amino acid residues long and has a calculated Mr of 61 793. Ribulokinase shares significant homology with xylulose kinase from Escherichia coli. Codon usage in the araB gene does not favor those codons which have intermediate codon-anticodon binding energy.     

柱孢鱼腥藻的铁蛋白与棕色固氮菌的钼铁蛋白的交叉互补作用

纯化的柱孢鱼腥藻铁蛋白能够与棕色固氮菌的钼铁蛋白有效地交叉反应,展现较高的活性。此异源交叉反应的乙炔还原比活及放氢比活,分别是蓝藻同源互补比活的83.8及66.7％。比较藻铁蛋白与菌钼铁蛋白异源交叉反应及藻固氮酶组分之间的同源反应的动力学特点时发现,铁蛋白对钼铁蛋白的最佳克分子比数前者(异源交叉反应)较后者(藻同源反应)为高,前者为5,后者为1;但反应的时间进程两者差别不大。     

新疆20种药用植物的染色体观察

本文对在新疆生长和引种栽培的10科20种药用植物染色体进行了计数和研究,其中5种进行了核型分析,6种为首次报道。     

碱性蛋白酶生产菌——地衣芽孢杆菌(B. licheniformis)的温和噬菌体

碱性蛋白酶生产菌——地衣芽孢杆菌经丝裂霉素C或紫外线处理,均可诱导释放噬菌体,电镜观察表明噬菌体头部外廓呈六边形,有不收缩的尾部(头部40nm×40nm,尾部107×5,7nm),噬菌体BLL1 DNA对限制酶Eco R Ⅰ,HindⅢ和Bam H Ⅰ敏感,分别切割成8,15,和9个片段,经电泳法测定。噬菌体DNA分子量约相当于23.4kb,根据解链温度计算出噬菌体的G+C含量约为31.2摩尔％,噬菌体提纯的外壳蛋白经SDS-聚丙烯酰胺凝胶电泳呈现5条主带,其分子量分别约为78000,72000,55000,39000,35000。     

细菌(Pseudomonas maltophilia)之绒毛膜促性腺激素(hCG)结合物质之研究

 细菌(Pseudomonas moltophilia)与hCG及LH有特异的亲和力,实验发现,细菌之生长曲线与hCG结合活性成平行关系,96小时达高峰,细菌之培养液中含有可溶性结合蛋白,该蛋白经硫酸铵沉淀(80％饱和度)、Sephadex G-100柱层析、DEAE-纤维素柱0.5mol/L NaCl梯度洗脱,再过Sepharose CL-AB柱,收集之活性部分经SDS电泳测得其分子量为70,000,凝胶层析测Stokes radius为41A,Schiff氏染色未见着色带。