HIV-1膜抗原部分位点的改造对假病毒形成及感染能力的影响

研究HIV-1膜抗原部分位点的改造对假病毒形成及病毒感染能力的影响。本实验采用环形诱变和DpnΙ筛选的方法对env进行定点突变。用获得的克隆和骨架质粒pSG3△env共转染293FT细胞,收获假病毒后用TZM-bl细胞进行单周期感染试验,检测特定位点改造对功能性假病毒形成能力的影响。改造之前样品S12-42-1的免疫印记的实验结果显示弥散的条带,蛋白大小约160kD,但单周期感染试验中其S/CO(样品信号值与临界值的比值)小于1,即不能形成假病毒。将该样品第457位氨基酸由丙氨酸变成天冬氨酸后,用突变体S12-42M进行单周感染试验,其S/CO值为6.65,表示突变体能够形成假病毒。结果表明HIV-1膜抗原部分位点的改变影响假病毒的形成或假病毒感染细胞的能力。     

Iron acquisition by Pseudomonas aeruginosa in the lungs of patients with cystic fibrosis

The bacterium Pseudomonas aeruginosa is commonly isolated from the general environment and also infects the lungs of patients with cystic fibrosis (CF). Iron in mammals is not freely available to infecting pathogens although significant amounts of extracellular iron are available in the sputum that occurs in the lungs of CF patients. P. aeruginosa has a large number of systems to acquire this essential nutrient and many of these systems have been characterised in the laboratory. However, which iron acquisition systems are active in CF is not well understood. Here we review recent research that sheds light on how P. aeruginosa obtains iron in the lungs of CF patients.     

具免疫时滞的HIV感染模型动力学性质分析

讨论了一类具免疫时滞的HIV感染模型.分析了未感染平衡点的全局渐近稳定性,给出了感染无免疫平衡点及感染免疫平衡点局部渐近稳定的充分条件.数值模拟结果表明,当易感细胞生成率的取值使得基本再生数满足平衡存在的条件且低于某一临界值时,时滞对平衡点的稳定性没有影响;若大于该临界值,随着时滞增大,稳定性开关发生,平衡点不稳定,出现一系列Hopf分支,最终表现为周期波动模式.     

Helicobacter spp. Other Than Helicobacter pylori

Non- H. pylori Helicobacter species (NHPHS) are associated with several important human and animal diseases. In the past year research into this group of bacteria has continued to gain attention, and novel species have been described in new niches owing to improvements in detection methods. Polymerase chain reaction and/or sequencing remain the gold standard for the detection of this genus. New insights into the pathogenesis of the NHPHS in hepatobiliary, gastric, and intestinal diseases were gained. In particular, data revealed interaction between hepatic steatosis and infectious hepatitis in the development of hepatocellular carcinoma. Evidence of an association between hepatitis C virus and Helicobacter spp. in hepatocarcinoma development was also provided; and male sex hormone signaling appeared to influence infectious hepatitis induced by Helicobacter hepaticus . More findings support an association between Helicobacter heilmannii and gastric adenocarcinoma; and in mice, mucins MUC4 and MUC5 but not MUC1 influence the colonization and pathogenesis of Helicobacter felis . Data indicated that the roles of the adaptive immune system in H. hepaticus -induced intestinal tumorigenesis are different in the small and large intestines, and environmental factors, such as bile acids may modulate H. hepaticus carcinogenic potential. New reports in the prevention and eradication of NHPHS showed a protective response against Helicobacter suis induced by vaccine administration, and a successful cross-foster rederivation method successfully eradicated Helicobacter spp. from contaminated mice litters. Overall, the studies provided insights into the pathophysiology of Helicobacter species other than Helicobacter pylori.     

Response of <Emphasis Type="Italic">Sphagnum</Emphasis> species mixtures to increased temperature and nitrogen availability

To predict the role of ombrotrophic bogs as carbon sinks in the future, it is crucial to understand how Sphagnum vegetation in bogs will respond to global change. We performed a greenhouse experiment to study the effects of two temperature treatments (17.5 and 21.7°C) and two N addition treatments (0 and 4 g N m⁻² year⁻¹) on the growth of four Sphagnum species from three geographically interspersed regions: S. fuscum, S. balticum (northern and central Sweden), S. magellanicum and S. cuspidatum (southern Sweden). We studied the growth and cover change in four combinations of these Sphagnum species during two growing seasons. Sphagnum height increment and production were affected negatively by high temperature and high N addition. However, the northern species were more affected by temperature, while the southern species were more affected by N addition. High temperature depressed the cover of the ‘wet’ species, S. balticum and S. cuspidatum. Nitrogen concentrations increased with high N addition. N:P and N:K ratios indicated P-limited growth in all treatments and co-limitation of P and K in the high N treatments. In the second year of the experiment, several containers suffered from a severe fungal infection, particularly affecting the ‘wet’ species and the high N treatment. Our findings suggest that global change can have negative consequences for the production of Sphagnum species in bogs, with important implications for the carbon sequestration in these ecosystems.     

Characterization of the smallest dimeric bile salt hydrolase from a thermophile Brevibacillus sp.

A thermophilic microorganism producing bile salt hydrolase was isolated from hot water springs, Pali, Maharashtra, India. This microorganism was identified as Brevibacillus sp. by 16S rDNA sequencing. Bile salt hydrolase (BSH) was purified to homogeneity from this thermophilic source using Q-sepharose chromatography and its enzymatic properties were characterized. The subunit molecular mass of the purified enzyme was estimated to be 28 kDa by SDS-PAGE and, 28.2 kDa by MALDI-TOF analysis. The native molecular mass was estimated to be 56 kDa by gel filtration chromatography, indicating the protein to be a homodimer. The pH and temperature optimum for the enzyme catalysis were 9.0 and 60°C, respectively. Even though BSH from Brevibacillus sp. hydrolyzed all of the six major human bile salts, the enzyme preferred glycine conjugated substrates with apparent K _M and k _cat values of 3.08 μM and 6.32 × 10² s⁻¹, respectively, for glycodeoxycholic acid. The NH₂-terminal sequence of the purified enzyme was determined and it did not show any homology with other bacterial bile salt hydrolases. To our knowledge, this is the first report describing the purification of BSH to homogeneity from a thermophilic source. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Crystal structure of human mitochondrial acyl-CoA thioesterase (ACOT2)

Acyl-CoA thioesterases (ACOTs) catalyze the hydrolysis of CoA esters to free CoA and carboxylic acids and have important functions in lipid metabolism and other cellular processes. Type I ACOTs are found only in animals and contain an α/β hydrolase domain, through currently no structural information is available on any of these enzymes. We report here the crystal structure at 2.1 Å resolution of human mitochondrial ACOT2, a type I enzyme. The structure contains two domains, N and C domains. The C domain has the α/β hydrolase fold, with the catalytic triad Ser294-His422-Asp388. The N domain contains a seven-stranded β-sandwich, which has some distant structural homologs in other proteins. The active site is located in a large pocket at the interface between the two domains. The structural information has significant relevance for other type I ACOTs and related enzymes.     

Characterization of the Mechanisms Involved in the Increased Renal Elimination of Bromosulfophthalein During Cholestasis: Involvement of Oatp1

The kidneys and liver are the major routes for organic anion elimination. We have recently shown that acute obstructive jaundice is associated with increased systemic and renal elimination of two organic anions, p-aminohippurate and furosemide, principally excreted through urine. This study examined probable adaptive mechanisms involved in renal elimination of bromosulfophthalein (BSP), a prototypical organic anion principally excreted in bile, in rats with acute obstructive jaundice. Male Wistar rats underwent bile duct ligation (BDL rats). Pair-fed sham-operated rats served as controls. BSP renal clearance was performed by conventional techniques. Renal organic anion-transporting polypeptide 1 (Oatp1) expression was evaluated by immunoblotting and IHC. Excreted, filtered, and secreted loads of BSP were all higher in BDL rats compared with Sham rats. The higher BSP filtered load resulted from the increase in plasma BSP concentration in BDL rats, because glomerular filtration rate showed no difference with the Sham group. The increase in the secreted load might be explained by the higher expression of Oatp1 observed in apical membranes from kidneys of BDL animals. This likely adaptation to hepatic injury, specifically in biliary components elimination, might explain, at least in part, the huge increase in BSP renal excretion observed in this experimental model. (J Histochem Cytochem 57:449–456, 2009)     

A quantitative assay measuring the function of lipase maturation factor 1

Newly synthesized lipoprotein lipase (LPL) and related members of the lipase gene family require an endoplasmic reticulum maturation factor for attainment of enzyme activity. This factor has been identified as lipase maturation factor 1 (Lmf1), and mutations affecting its function and/or expression result in combined lipase deficiency (cld) and hypertriglyceridemia. To assess the functional impact of Lmf1 sequence variations, both naturally occurring and induced, we report the development of a cell-based assay using LPL activity as a quantitative reporter of Lmf1 function. The assay uses a cell line homozygous for the cld mutation, which renders endogenous Lmf1 nonfunctional. LPL transfected into the mutant cld cell line fails to attain activity; however, cotransfection of LPL with wild-type Lmf1 restores its ability to support normal lipase maturation. In this report, we describe optimized conditions that ensure the detection of a complete range of Lmf1 function (full, partial, or complete loss of function) using LPL activity as the quantitative reporter. To illustrate the dynamic range of the assay, we tested several novel mutations in mouse Lmf1. Our results demonstrate the ability of the assay to detect and analyze Lmf1 mutations having a wide range of effects on Lmf1 function and protein expression.     

Regulatory volume decrease in cardiomyocytes is modulated by calcium influx and reactive oxygen species

We investigated the role of Ca²⁺ in generating reactive oxygen species (ROS) induced by hyposmotic stress (Hypo) and its relationship to regulatory volume decrease (RVD) in cardiomyocytes. Hypo-induced increases in cytoplasmic and mitochondrial Ca²⁺. Nifedipine (Nife) inhibited both Hypo-induced Ca²⁺ and ROS increases. Overexpression of catalase (CAT) induced RVD and a decrease in Hypo-induced blebs. Nife prevented CAT-dependent RVD activation. These results show a dual role of Hypo-induced Ca²⁺ influx in the control of cardiomyocyte viability. Hypo-induced an intracellular Ca²⁺ increase which activated RVD and inhibited necrotic blebbing thus favoring cell survival, while simultaneously increasing ROS generation, which in turn inhibited RVD and induced necrosis.