Inhibitory Effects of Partially Decomposed Alginate on Production of Glucan and Organic Acid by Streptococcus sobrinus 6715

Our previous study has already clarified that partially decomposed alginate (Alg53) by Vibrio alginolyticus SUN53 has a competitive inhibitory effect on sucrase. The objective of this study is to evaluate the influence of Alg53 on the production of glucan from sucrose by glucosyltransferase and acid from glucose by Streptococcus sobrinus 6715. Glucosyltransferase was prepared from cultural medium of S. sobrinus using ultrafiltration and hydroxyapatite chromatography. In order to examine the inhibitory effect of Alg53 for production of glucan by GTase, partially purified GTase, sucrose and Alg53 solution were incubated at 37°C. The influence of Alg53 on the production of acid from glucose was evaluated by a degree of pH decline during the incubation for 60 min. The original Alg53 solution markedly inhibited to 21% of the synthesis of water-insoluble glucan from sucrose and that of 10-fold diluted of Alg53 solution was 23%. However, the production of water-soluble glucan from sucrose by GTase was hardly affected by Alg53. Furthermore, Alg53 suppressed dose-dependently pH decline by organic acid converted from glucose. These results suggest that Alg53 is expected as a functional food material which prevents or reduces dental caries.     

A single nucleotide mutation results in loss of enzymatic activity in the hyaluronate lyase gene of Streptococcus pyogenes

Group A streptococci produce a variety of extracellular proteins, many of which are considered to be virulence factors. One of these is hyaluronate lyase (HylA), an enzyme capable of degrading the extracellular matrix of the host as well as the bacterial capsule. The current study examined three genotypes of hylA (full, truncated and deleted). Only isolates containing a full-length gene produced an enzymatically active hyaluronate lyase; however, truncation of the protein was not the reason for loss of activity. A single nucleotide substitution, resulting in an amino acid change at position 199 of the lyase was present in a highly-conserved region of the protein in isolates not producing active enzyme. In serotypes 4 and 22, those producing active enzymes, this residue was an aspartic acid, in serotypes not showing hyaluronate lyase activity, it was a valine. Site-directed mutagenesis indicated the loss of enzymatic activity of the hyaluronate lyase is in part determined by the mutation resulting in an amino acid residue change. This mutation results in an inactive form of the enzyme and is found in the more virulent serotypes of Streptococcus pyogenes, suggesting that hyaluronate lyase could interfere with the disease process, in essence being an anti-virulence factor.     

Ammonia metabolism,the brain and fatigue; revisiting the link

This review addresses the ammonia fatigue theory in light of new evidence from exercise and disease studies and aims to provide a view of the role of ammonia during exercise. Hyperammonemia is a condition common to pathological liver disorders and intense or exhausting exercise. In pathology, hyperammonemia is linked to impairment of normal brain function and the onset of the neurological condition, hepatic encephalopathy. Elevated blood ammonia concentrations arise due to a diminished capacity for removal via the liver and lead to increased exposure of organs, such as the brain, to the toxic effects of ammonia. High levels of brain ammonia can lead to deleterious alterations in astrocyte morphology, cerebral energy metabolism and neurotransmission, which may in turn impact on the functioning of important signalling pathways within the neuron. Such changes are believed to contribute to the disturbances in neuropsychological function, in particular the learning, memory, and motor control deficits observed in animal models of liver disease and also patients with cirrhosis. Hyperammonemia in exercise occurs as a result of an increased production by contracting muscle, through adenosine monophosphate (AMP) deamination (the purine nucleotide cycle) and branched chain amino acid (BCAA) deamination prior to oxidation. Plasma concentrations of ammonia during exercise often achieve or exceed those measured in liver disease patients, resulting in increased cerebral uptake. In this article we propose that exercise-induced hyperammonemia may lead to concomitant disturbances in brain function, potentially through similar mechanisms underpinning pathology, which may impact on performance as fatigue or reduced function, especially during extreme exercise.     

海藻酸钠在药物制剂中的研究进展

海藻酸钠是从海带或海藻中提取的天然多糖类化合物，作为缓释制剂辅料广泛应用于片剂、微九、微蠢、脂质体、纳米粒等缓释制剂中，现综述近年来海藻酸钠作为辅料的影响因素及在缓释制剂中的应用研究进展。     

藻酸双酯钠铬配合物的制备及其理化性质的初步研究

目的 制备藻酸双酯钠(PSS)的铬配合物.并研究其溶解性、颜色、分子量等理化性质和光谱表征.方法 将PSS与三价铬离子在不同pH条件下进行络合.制备PSS铬配合物(PSS-Cr),采用正交实验优化制备条件.并采用UV、IR、HPGPC、原子吸收和电导滴定等分析方法 对PSS-Cr的结构和基本理化性质进行初步分析.结果 与结论 制备PSS-Cr的最适条件为:温度为50℃.pH值为7,PSS(以单糖计)与铬的摩尔比为2:1,在此条件下制备的PSS-Cr中的铬含量迭6.69%,重均相对分子质量为12188Da.     

口服利福平海藻酸钠微球的制备

［摘要］目的研制口服利福平海藻酸钠微球。方法采用静电液滴法制备利福平海藻酸钠微球，测定粒径大小、包封率、载药量及其影响因素，考察微球的体外释放特点。结果微球球形圆整，分散性好，平均粒径70.2 μm，包封率83.5%，载药量17.1%，在模拟肠液中的释放呈快慢相，时间长而药物释放完全。结论以海藻酸钠、硬脂酸为材料，用静电液滴法制备利福平微球，球径小、包封率高、释药时间长，工艺简便。     

Effect of allogeneic Schwann cell transplantation on peripheral nerve regeneration

Transplantation of allogeneic Schwann cells (SC) would make it feasible to reconstruct immediately peripheral nerve defects, compared to using autologous SC; however, this treatment modality has not been adequately evaluated. The aim of this study was to characterize and compare the effects of allogeneic versus syngeneic SC transplantation following peripheral nerve injury. Polyhydroxybutyrate conduits were used to bridge a 10-mm gap in the rat sciatic nerve. The conduits were filled with alginate hydrogel with or without cultured allogeneic or syngeneic genetically labeled SC, without the use of immunosuppressive therapy, and examined after 2, 3, and 6 weeks with 5-bromo-4-chloro-3-indoyl-beta-D-galactosidase chemical staining and immunohistochemistry to quantify SC migration into the conduit, axonal regeneration, the state of SC differentiation, and the expression of major histocompatibility complexes (MHC) I and II, as well as to quantify macrophage and B- and T-lymphocyte infiltration. Allogeneic SC were rejected by 6 weeks, whereas syngeneic SC could still be identified. Allogeneic and syngeneic SC equally enhanced the axonal regeneration distance but the quantity of axons was greater using syngeneic SC. The ingrowth of SC into the conduits containing allogeneic SC was similar to that observed in the presence of syngeneic SC, indicating the absence of deleterious immune response. SC continued to express phenotypic markers of nonmyelination and these were highest in conduits with allogeneic SC. Expression of MHC I and II was higher in the conduits with allogeneic SC at 3 weeks and without significant difference in the number of macrophages and lymphocytes, except at 6 weeks, when there was a larger number of lymphocytes using syngeneic SC. In conclusion, allogeneic SC enhanced axonal regeneration distance and did not induce a deleterious immune response. In a clinical setting the immediate availability of allogeneic SC for transplantation may compensate for the better outcome achieved by the use of autologous SC that require a longer preparation time in culture.     

Prothrombin activity and concentration in healthy subjects with and without the prothrombin G20210A mutation

A synthetic pentasaccharide, containing an intact antithrombin III (ATIII) binding site that is in clinical studies a specific antifactor Xa agent, serves as a substrate for a heparin lyase (heparinase I, EC 4.2.2.7) from Flavobacterium heparinum. Heparinase I, currently being assessed as a heparin reversal agent, also reverses the antifactor Xa activity of this synthetic pentasaccharide by breaking it down to inactive disaccharide and trisaccharide products.     

海藻酸盐/壳聚糖衍生物复合抗菌纤维

通过溶液纺丝法制备海藻酸盐/羧甲基壳聚糖（CMC）共混纤维,并用红外光谱,X射线衍射和扫描电镜对共混纤维进行了表征.结果表明：共混体系中的两种组分之间存在着较强的相互作用,有良好的相容性.当ωCMC=0.30时,共混纤维的干态抗张强度达到最大值,13.8cN/tex.当ωCMC=0.10时,纤维的干态断裂伸长率可达23.1%.纤维的湿态抗张强度和断裂伸长率随着CMC含量的增加而降低.CMC的引入,可显著提高纤维的吸水率.用壳聚糖季铵盐对纤维进行处理,可赋予纤维抗菌性.     

壳聚糖-海藻酸盐纳米粒子的制备及其对BSA的载药与释放特性

带相反电荷的聚电解质在水溶液中能通过静电相互作用自组装形成壳聚糖-海藻酸盐纳米粒。利用动态光散射纳米粒度分析仪考察了钙离子及壳聚糖对粒子粒径的影响。结果表明：钙离子的存在可使粒子粒径从268．5nm降为203．4nm，但随着钙离子含量的继续升高，粒径迅速增大，当钙离子浓度大于0．45g／L时形成凝胶。壳聚糖含量的增加和蛋白的包裹均会使粒径增大。所制备的纳米粒对BSA具有较高的包栽能力，并有一定的缓释作用。当壳聚糖投料量增加时，可使BSA在pH=7．4的PBS中的释放减慢。