固定化酶的微环境效应—载体离子基团性质的影响

作者合成了阴离子型和阳离子型葡聚糖,以此为载体,用CNBr活化其剩余羟基,固定化了葡萄糖淀粉酶和葡萄糖异构酶。就离子型载体对固定化酶的蛋白载量、最适pH和热稳定性等的影响做了考察。发现固定化酶的蛋白载量不仅与载体的电性质有关,也与酶分子自身的电性质有关。当载体电性质与酶蛋白电性质相反时,固定化酶的蛋白载量增加,热稳定性提高、载体电性质与酶蛋白电性质相同时,固定化酶的蛋白载量不变或下降,其热稳定性不变。作者还发现当离子型载体孔度和体系缓冲液浓度一定时,酶分子能否进入多孔性载体内部,对其最适pH是否变化影响极大。若酶分子仅被连接在载体的外表层,其最适pH不发生变化,反之亦然。作者还观察到当多糖类载体引入氨基或羧基后,大大增强了其抵抗微生物侵蚀的能力。     

猪肺炎支原体膜上ATP酶生化性质的研究

猪肺炎支原体膜上ATP酶为Mg~(2+)激活,乌巴因不抑制。DCCD和寡霉素对该酶也无抑制作用,只有NBD与Quercetin才有一定的抑制效果。用梯度凝胶电泳可获均一的具有活性的酶蛋白带。     

Interaction of opioid peptides and other drugs with multiple kappa receptors in rat and human brain. Evidence for species differences.

Previous experiments resolved four kappa binding sites in guinea pig brain termed kappa 1a, kappa 1b, and kappa 2b. The present study was undertaken to examine the occurrence of kappa receptor subtypes in rat and human brain. [3H]U69,593 and [3H]bremazocine were used to label kappa 1 and kappa 2 binding sites, respectively, present in brain membranes depleted of mu and delta binding sites by pretreatment with the irreversible ligands, BIT and FIT. Low levels of [3H]U69,593 binding precluded a detailed quantitative study of kappa 1 binding sites in these species. Quantitative examination of [3H]bremazocine binding resolved two kappa 2 binding sites in both rat and human brain whose ligand selectivity patterns differed from that of the guinea pig. These observations suggest that there may be considerable variation in the ligand recognition site of kappa receptor subtypes among mammalian species.     

Interstitial cells associated with the deep muscular plexus of the guinea-pig small intestine,with special reference to the interstitial cells of Cajal

Summary Interstitial cells associated with the deep muscular plexus of the guinea-pig small intestine were studied by electron microscopy, and three-dimensional cell models were reconstructed from serial ultrathin sections with a computer graphic system. Three types of cells were recognized. The first type was similar in shape to smooth muscle cells, but did not contain an organized contractile apparatus. Many large gap junctions comprising about 4% of the cell surface were present; they connected cells of the first type to each other, to the second type of cell and to smooth muscle cells of the outer circular layer. The second type of cell had a welldemarcated cell body with long slender processes and was characterized by a large amount of glycogen comprising about 9% of the cell volume. The third type of cell was similar to fibroblasts, and contained well-developed Golgi apparatus and rough endoplasmic retiulum. Some of these fibroblast-like cells (a possible subtype) formed small gap junctions. All three types of cells showed close relationships with nerve varicosities. This cellular network consisting of gap-junction-rich cells, glycogen-rich cells and smooth muscle cells may be involved in the pacemaking activity of intestinal movement.     

Comparative analysis of glycoprotein and glycolipid composition of virulent and avirulent strain membranes ofMycoplasma hyopneumoniae

The glycoproteins and glycolipids from membranes of virulent strain Z and avirulent strain M ofMycoplasma hyopneumoniae have been compared. The proteins and the glycoproteins were identified by SDS-polyacrylamide gel electrophoresis and concanavalin A-biotin labeling, respectively. The membrane preparation contained approximately 34 protein bands with molecular weights between 20 KD and 100 KD. The concanavalin A-biotin system reacted with a glycoprotein of a molecular weight of approximately 28,000 from avirulent strain M and did not react with the correspondent band from virulent strain Z. The membrane glycolipids of both strains consisted of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), and the percentages of 160, 180, and 181 fatty acids comprised more than 80% of the total fatty acids of membrane glycolipids. The 180 fatty acid of MGDG in avirulent strain M was twofold higher than that of virulent strain Z.     

Alport syndrome: a genetic study of 31 families

Thirty one families with Alport syndrome including 3 families with associated syndromes were studied. The location of the COL4A5 gene, responsible for the Alport syndrome, was determined by linkage analysis with eight probes of the Xq arm and by a radiation hybrid panel. Concordant data indicated the localization of the Alport gene between DXS17 and DXS11. Four deletions and one single base mutation of the COL4A5 gene were detected. Homogeneity tests failed to show any evidence of genetic heterogeneity superimposed on clinical heterogeneity for ophthalmic signs and end-stage renal disease age.     

p140trk mRNA marks NGF-responsive forebrain neurons: evidence that trk gene expression is induced by NGF.

Nerve growth factor (NGF) appears to act as a neurotrophic factor for basal forebrain and caudate-putamen cholinergic neurons. The mechanism by which NGF transduces its signal in these neurons is yet to be defined. Recent data indicate that the product of the trk gene, p140trk, is a critical component of the NGF receptor. Herein, we show that p140trk mRNA is highly restricted in its distribution in the adult rat forebrain, that it is present in cholinergic neurons, and that most if not all cholinergic neurons contain p140trk mRNA. Furthermore, induction of trk expression by NGF suggests that neurotrophin-mediated up-regulation of their receptor tyrosine kinases is an important feature of their actions and that neurotrophins may regulate the activity of responsive neurons through increasing the level of their receptors.     

Expression of an enhancer-binding protein in insect cells transfected with the Autographa californica nuclear polyhedrosis virus IE1 gene.

The baculovirus Autographa californica nuclear polyhedrosis virus contains an element known as homologous region 5 (hr5) which is an enhancer of delayed-early viral gene expression. To begin to identify proteins that interact with hr5, DNA-protein interactions were analyzed by using extracts from Spodoptera frugiperda cells and a fragment of DNA containing the left half of the hr5 enhancer. This 252-bp DNA fragment contains two copies of a 30-bp direct repeat (DR30) and two copies of a 24-bp imperfect palindrome contained within a 60-bp direct repeat (DR60). Extracts prepared from normal S. frugiperda cells and cells transfected with pUC8 lacked enhancer-binding proteins. However, when gel shift assays were performed with extracts from cells transfected with a plasmid containing the viral trans-activator IE1 gene, two DNA-protein complexes were formed. Both DNA-protein complexes were specifically inhibited by competition with a 60-bp oligonucleotide corresponding to DR60 but not by competition with a different oligonucleotide corresponding to DR30. Formation of the two complexes did not appear to involve cooperative interactions between binding proteins. When DR60 was used as a probe, a single complex was formed. To measure the enhancer activity of DR60, a reporter plasmid was constructed that contained DR60 cloned upstream of the reporter chloramphenicol acetyltransferase gene under the control of the delayed-early 39K promoter. Transient expression analysis indicated that the oligonucleotide increased expression of this gene 300-fold over the level obtained in the absence of any enhancer sequences.