喜温嗜酸硫杆菌SM-1的ROS防护机制

【目的】从基因组水平探讨生物冶金微生物——喜温嗜酸硫杆菌(Acidithiobacillus caldus)的活性氧类物质(Reactive oxygen species,ROS)防护机制。【方法】采用罗氏454 GS FLX测序平台对喜温嗜酸硫杆菌SM-1进行全基因组测序,利用NCBI非冗余蛋白数据库、Uniport蛋白数据库对全基因组序列进行功能注释,并采用基因组百科全书数据库(KEGG)进行基因组代谢途径重构,通过比较基因组学方法分析SM-1基因组中参与ROS防护相关的基因及可能的分子机制。【结果】SM-1细胞内的酶促抗氧化系统可用于清除细胞内产生的ROS物质,而非酶促抗氧化系统可用于维持细胞内的还原性内环境;细胞内的DNA损伤修复系统可用于修复DNA的氧化损伤从而保持个体遗传物质的稳定性。此外,SM-1基因组中大量的转座元件可能会增加基因组的可塑性以适应极端冶金环境。【结论】SM-1基因组序列的获得为从整体水平揭示喜温嗜酸硫杆菌适应生物冶金环境ROS氧化损伤的防护机制提供了帮助,对于SM-1的ROS防护机制的认知也为进一步通过遗传改造、提升其在高浓度重金属离子冶金环境中的抗性、提高冶金效率提供了理论指导。     

Lactoferrin Dampens High-Fructose Corn Syrup-Induced Hepatic Manifestations of the Metabolic Syndrome in a Murine Model

Hepatic manifestations of the metabolic syndrome are related obesity, type 2 diabetes/insulin resistance and non-alcoholic fatty liver disease. Here we investigated how the anti-inflammatory properties of lactoferrin can protect against the onset of hepatic manifestations of the metabolic syndrome by using a murine model administered with high-fructose corn syrup. Our results show that a high-fructose diet stimulates intestinal bacterial overgrowth and increases intestinal permeability, leading to the introduction of endotoxin into blood circulation and liver. Immunohistochemical staining of Toll-like receptor-4 and thymic stromal lymphopoietin indicated that lactoferrin can modulate lipopolysaccharide-mediated inflammatory cascade. The important regulatory roles are played by adipokines including interleukin-1β, interleukin-6, tumor necrosis factor-α, monocyte chemotactic protein-1, and adiponectin, ultimately reducing hepatitis and decreasing serum alanine aminotransferase release. These beneficial effects of lactoferrin related to the downregulation of the lipopolysaccharide-induced inflammatory cascade in the liver. Furthermore, lactoferrin reduced serum and hepatic triglycerides to prevent lipid accumulation in the liver, and reduced lipid peroxidation, resulting in 4-hydroxynonenal accumulation. Lactoferrin reduced oral glucose tolerance test and homeostasis model assessment-insulin resistance. Lactoferrin administration thus significantly lowered liver weight, resulting from a decrease in the triglyceride and cholesterol synthesis that activates hepatic steatosis. Taken together, these results suggest that lactoferrin protected against high-fructose corn syrup induced hepatic manifestations of the metabolic syndrome.     

Increasing quadriceps loads affect the lengths of the ligaments and the kinematics of the knee.

The relationships between the lengths of the ligaments and kinematics of the knee and quadriceps load, for low to physiologic levels of quadriceps loads, have not previously been studied. We investigated the effects of increasing levels of quadriceps force, necessary to balance increasing levels of externally applied flexion moments, on the kinematics of the tibiofemoral joint and on the separation distances between insertions of selected fibers of the major ligaments of the knee in twelve cadavera. Static measurements were made using a six-degree-of-freedom digitizer for flexion angles ranging from 0 to 120 deg in 15 deg increments. Quadriceps generated extension of the knee was performed by applying loads to the quadriceps tendon to equilibrate each of four magnitudes of external flexion moments equivalent to 8.33, 16.67, 25.00, and 33.33 percent of values previously reported for maximum isometric extension moments. The magnitude of quadriceps force increased linearly (p < 0.0001) as external flexion moment increased throughout the entire range of flexion. Anterior translation, internal rotation, and abduction of the tibia increased linearly (p < 0.0001, p < 0.001, p < 0.001) as external flexion moment and, hence, quadriceps load increased. For the fibers studied, the anterior cruciate ligament (p < 0.0076), posterior cruciate ligament (p < 0.0001), and medial collateral ligament (p < 0.0383) lengthened linearly while the lateral collateral ligament (p < 0.0124) shortened linearly as quadriceps load increased. Based on these results for low to physiologic levels of quadriceps loads, it is reasonable to assume that the ligament lengths or knee kinematics expected with higher quadriceps loads can be extrapolated.     

A pivotal role for the structure of the Holliday junction in DNA branch migration.

Branch migration of a DNA Holliday junction is a key step in genetic recombination that affects the extent of transfer of genetic information between homologous DNA sequences. We previously observed that the rate of spontaneous branch migration is exceedingly sensitive to metal ions and postulated that the structure of the cross-over point might be one critical determinant of the rate of branch migration. Other investigators have shown that in the presence of divalent metal ions like magnesium, the Holliday junction assumes a folded conformation in which base stacking is retained through the cross-over point. This base stacking is disrupted in the absence of magnesium. Here we measure the rate of branch migration as a function of Mg2+ concentration. The rate of branch migration increases dramatically at MgCl2 concentrations below 500 microM, with the steepest acceleration occurring between 300 and 100 microM MgCl2. This increase in the rate of branch migration coincides with the loss of base stacking in the four-way junction over this same interval of magnesium concentration, as measured by the susceptibility of junction residues to modification by osmium tetroxide and diethyl pyrocarbonate. We conclude that at physiological concentrations of intracellular Mg2+, base stacking in the Holliday junction constitutes one kinetic barrier to branch migration and that disruption of base stacking at the cross-over relieves this constraint.     

Determination of pilocarpic acid in human plasma by capillary gas chromatography with mass-selective detection

A novel, highly sensitive method for the determination of pilocarpic acid (PA) in human plasma is described. In addition, the method provides for the conversion of the lactone, pilocarpine (P), to PA so that a total drug presence can be determined. Using novel high-performance liquid chromatographic conditions capable of separating P, isopilocarpine (I-P), PA and isopilocarpic acid (I-PA) from each other and from endogenous plasma impurities, it was confirmed that P exclusively and quantitatively converts to PA in heparinized human plasma during storage. For the determination of PA, the selective extraction of PA from protein-free plasma was accomplished using two different solid-phase extraction (SPE) cartridges in two consecutive SPE steps. After extraction, PA was lactonized with trifluoroacetic acid back to P, and both P and an internal standard were acylated using heptafluorobutyric anhydride (HFBA). The trifluoroacetylated derivatives were monitored using gas chromatography (GC) with mass spectrometric (MS) detection. This procedure allowed the sensitive and reliable determination of PA with a limit of quantification (LOQ) of 1 ng/ml, which could not be achieved using previously described methods. The assay was validated in the concentration range of 1 to 10 ng/ml with an intra-day precision (expressed as the coefficient of variation, C.V.) ranging from 9.9 to 0.5%. Inter-day precision for the quality control standard at 2.5 ng/ml showed a C.V. of 10.2%. Accuracy ranged from 94 to 102%. The assay was used to monitor the maximum systemic exposure to P, administered by the ocular route, in terms of total plasma PA (P and PA).     

The human kininogen gene (KNG) mapped to chromosome 3q26-qter by analysis of somatic cell hybrids using the polymerase chain reaction

Summary Kinins, peptide products of kininogens, may be involved in hypertensive and diabetic diseases, and inflammatory disorders. The human kininogen gene (KNG) has been mapped to chromosome 3, using a panel of human-hamster somatic cell hybrids by polymerase chain reaction of hybrid DNA with gene-specific primers. KNG was further assigned to 3q26-3qter, using DNA from a second panel of chromosome 3 deletion mapping cell hybrids.     

Construction of expanded continuous life tables--a generalization of abridged and complete life tables.

This article extends the recent abridged life-table method of Hsieh. It generalizes the conventional discrete (abridged and complete) life tables into a continuous life table that can produce life-table functions at any age and develops a unified method of life-table construction that simplifies the disparate laborious procedures used in the traditional approach of constructing abridged and complete life tables. A set of precise procedures based on the complete cubic spline for the main body of the table and a mortality law for advanced ages is developed for estimating the basic and nonbasic life-table functions from a given mortality schedule. The proposed method can also produce more life-table functions than other existing methods. The method is illustrated with Canadian data.