高同型半胱氨酸血症致动脉粥样硬化的细胞分子机制

同型半胱氨酸（homocysteine,Hcy)是蛋氨酸代谢途径产生的含硫氨基酸,其代谢紊乱可以诱导高同型半胱氨酸血症的发生,已被临床及流行病学资料证实为动脉粥样硬化发病的独立危险因子。Hcy通过激活二酰甘油－蛋白激酶C－（DAG－PKC）及丝裂素活化蛋白激酶（MAPK）途径,诱导相关基因的表达,促进细胞钙化,启动脂质过氧化应激,从而损伤心血管系统。金属硫蛋白,牛磺酸,L－精氨酸作为内源性小分子物质,成为继维生素B6,B12之后控制和治疗高同型半胱氨酸血症的新途径。     

SNPCEQer: detecting SNPs in sequences generated by the Beckman CEQ2000 DNA Analysis System

SNPCEQer identifies and reports SNPs in sequences obtained from the Beckman CEQ2000 DNA Analysis System. SNPCEQer aligns sequences obtained using CEQ2000 heterozygote detection analysis and reports discrepancies between individual sequences and the consensus sequence it generates from this set as SNPs when the individual base calls have high-quality values. SNPCEQer reported comparable numbers of SNPs to the UNIX-based PolyPhred (148 vs. 165, respectively) in regions amplified from eight genes. A total of 21 different SNPs was discovered. Each gene region was analyzed in 96-306 samples. SNPCEQer was designed to operate from Windows NT, making SNP detection more accessible to users without UNIX systems. SNPCEQer is available free of charge at http://innovation.swmed.edu.     

Two genetic circuits repress the Caenorhabditis elegans heterochronic gene lin-28 after translation initiation

The heterochronic gene lin-28 of the nematode Caenorhabditis elegans controls the relative timing of diverse developmental events during the animal's larval stages. lin-28 is stage-specifically regulated by two genetic circuits: negatively by the 22-nt RNA lin-4 and positively by the heterochronic gene lin-14. Here, we show that lin-28 is repressed during normal development by a mechanism that acts on its mRNA after translation initiation. We provide evidence that lin-14 inhibits a negative regulation that is independent of the lin-4 RNA and involves the gene daf-12, which encodes a nuclear hormone receptor. The lin-4-independent repression does not affect the initiation of translation on the lin-28 mRNA, and like the lin-4-mediated repression, acts through the gene's 3'-untranslated region. In addition, we find that lin-4 is not sufficient to cause repression of lin-28 if the lin-4-independent circuit is inhibited. Therefore, the lin-4-independent circuit likely contributes substantially to the down-regulation of lin-28 that occurs during normal development. The role of lin-4 may be to initiate or potentiate the lin-4-independent circuit. We speculate that a parallel lin-4-independent regulatory mechanism regulates the expression of lin-14.     

Hydrolysis of biological peptides by human angiotensin-converting enzyme-related carboxypeptidase

Human angiotensin-converting enzyme-related carboxypeptidase (ACE2) is a zinc metalloprotease whose closest homolog is angiotensin I-converting enzyme. To begin to elucidate the physiological role of ACE2, ACE2 was purified, and its catalytic activity was characterized. ACE2 proteolytic activity has a pH optimum of 6.5 and is enhanced by monovalent anions, which is consistent with the activity of ACE. ACE2 activity is increased approximately 10-fold by Cl(-) and F(-) but is unaffected by Br(-). ACE2 was screened for hydrolytic activity against a panel of 126 biological peptides, using liquid chromatography-mass spectrometry detection. Eleven of the peptides were hydrolyzed by ACE2, and in each case, the proteolytic activity resulted in removal of the C-terminal residue only. ACE2 hydrolyzes three of the peptides with high catalytic efficiency: angiotensin II () (k(cat)/K(m) = 1.9 x 10(6) m(-1) s(-1)), apelin-13 (k(cat)/K(m) = 2.1 x 10(6) m(-1) s(-1)), and dynorphin A 1-13 (k(cat)/K(m) = 3.1 x 10(6) m(-1) s(-1)). The ACE2 catalytic efficiency is 400-fold higher with angiotensin II () as a substrate than with angiotensin I (). ACE2 also efficiently hydrolyzes des-Arg(9)-bradykinin (k(cat)/K(m) = 1.3 x 10(5) m(-1) s(-1)), but it does not hydrolyze bradykinin. An alignment of the ACE2 peptide substrates reveals a consensus sequence of: Pro-X((1-3 residues))-Pro-Hydrophobic, where hydrolysis occurs between proline and the hydrophobic amino acid.     

Mechanisms and rates of bacterial colonization of sinking aggregates

Quantifying the rate at which bacteria colonize aggregates is a key to understanding microbial turnover of aggregates. We used encounter models based on random walk and advection-diffusion considerations to predict colonization rates from the bacteria's motility patterns (swimming speed, tumbling frequency, and turn angles) and the hydrodynamic environment (stationary versus sinking aggregates). We then experimentally tested the models with 10 strains of bacteria isolated from marine particles: two strains were nonmotile; the rest were swimming at 20 to 60 microm s(-1) with different tumbling frequency (0 to 2 s(-1)). The rates at which these bacteria colonized artificial aggregates (stationary and sinking) largely agreed with model predictions. We report several findings. (i) Motile bacteria rapidly colonize aggregates, whereas nonmotile bacteria do not. (ii) Flow enhances colonization rates. (iii) Tumbling strains colonize aggregates enriched with organic substrates faster than unenriched aggregates, while a nontumbling strain did not. (iv) Once on the aggregates, the bacteria may detach and typical residence time is about 3 h. Thus, there is a rapid exchange between attached and free bacteria. (v) With the motility patterns observed, freely swimming bacteria will encounter an aggregate in <1 day at typical upper-ocean aggregate concentrations. This is faster than even starving bacteria burn up their reserves, and bacteria may therefore rely solely on aggregates for food. (vi) The net result of colonization and detachment leads to a predicted equilibrium abundance of attached bacteria as a function of aggregate size, which is markedly different from field observations. This discrepancy suggests that inter- and intraspecific interactions among bacteria and between bacteria and their predators may be more important than colonization in governing the population dynamics of bacteria on natural aggregates.     

Exopolysaccharide biosynthesis and related enzyme activities of the medicinal fungus, Ganoderma lucidum, grown on lactose in a bioreactor

Exopolysaccharide (EPS) production and biosynthesis were studied in Ganoderma lucidum, a fungus used in traditional Chinese medicine, grown with lactose in a bioreactor. -Galactosidase activity, which implies the existence of a lactose permease system, was induced by lactose. Lactose feeding also increased -phosphoglucomutase activity and EPS accumulation but decreased phosphoglucose isomerase activity and lactate concentration in the culture broth. A maximum cell density of 22 g l^–1 and EPS at 1.25 g l^–1 were obtained in fed-batch bioreactor culture.     

Selective cytotoxicity of scFv-TNF fusion protein on the tumor cells

A fusion protein of single-chain, Fv-tumor necrosis factor , scFv-TNF, was constructed and expressed in the Pichia pastoris expression system. There was 67-fold less toxicity of the fusion protein when compared with TNF- alone in cells expressing CA125. Furthermore, scFv-TNF was 10-fold more selective in cell killing directed by anti-CA125 scFv in a CA125-positive cell line than the CA125-negative line.