Cross-sectional DXA and MR measures of tibial periarticular bone associate with radiographic knee osteoarthritis severity

SummaryObjectiveWe evaluated the relationship of medial proximal tibial periarticular areal bone mineral density (paBMD) and trabecular morphometry and determined whether these bone measures differed across radiographic medial joint space narrowing (JSN) scores.Methods482 participants of the Osteoarthritis Initiative (OAI) Bone Ancillary Study had knee dual X-ray absorptiometry (DXA) and trabecular bone 3T magnetic resonance imaging (MRI) exams assessed at the same visit. Medial proximal tibial paBMD was measured on DXA and apparent trabecular bone volume fraction (aBV/TV), thickness (aTb.Th), number (aTb.N), and spacing (aTb.Sp) were determined from MR images. Radiographs were assessed for medial JSN scores (0–3). We evaluated associations between medial paBMD and trabecular morphometry. Whisker plots with notches of these measures versus medial JSN scores were generated and presented.ResultsMean age was 63.9 (9.2) years, BMI 29.6 (4.8) kg/m2, and 53% were male. The Spearman correlation coefficients between DXA-measured medial paBMD and aBV/TV was 0.61 [95% confidence interval (CI) 0.55–0.66]; between paBMD and aTb.Th was 0.38 (95%CI 0.30–0.46); paBMD and aTb.N was 0.65 (95%CI 0.60–0.70); paBMD and aTb.Sp was −0.65 (95%CI −0.70 to −0.59). paBMD and the trabecular metrics were associated with medial JSN scores.ConclusionThe moderate associations between periarticular trabecular bone density and morphometry and their relationship with greater severity of knee OA support hypotheses of remodeling and/or microscopic compression fractures in the natural history of OA. Longitudinal studies are needed to assess whether knee DXA will be a predictor of OA progression. Further characterization of the periarticular bone in OA utilizing complementary imaging modalities will help clarify OA pathophysiology

Mutational analysis of feedback inhibition and catalytic sites of prephenate dehydratase from Corynebacterium glutamicum

Prephenate dehydratase is a key regulatory enzyme in the phenylalanine-specific pathway of Corynebacterium glutamicum. PCR-based random mutagenesis and functional complementation were used to screen for m-fluorophenylalanine (mFP)-resistant mutants. Comparison of the amino acid sequence of the mutant prephenate dehydratases indicated that Ser-99 plays a role in the feedback regulation of the enzyme. When Ser-99 of the wild-type enzyme was replaced by Met, the specific activity of the mutant enzyme was 30% lower than that of the wild-type. The Ser99Met mutant was active in the presence of 50 muM phenylalanine, whereas the wild-type enzyme was not. The functional roles of the eight conserved residues of prephenate dehydratase were investigated by site-directed mutagenesis. Glu64Asp substitution reduced enzyme activity by 15%, with a 4.5- and 1.7-fold increase in K-m and k(cat) values, respectively. Replacement of Thr-183 by either Ala or Tyr resulted in a complete loss of enzyme activity. Substitution of Arg-184 with Leu resulted in a 50% decrease of enzyme activity. The specific activity for Phe185Tyr was more than 96% lower than that of the wild-type, and the K-m value was 26-fold higher. Alterations in the conserved Asp-76, Glu-89, His-115, and Arg-236 residues did not cause a significant change in the K-m and k(cat) values. These results indicated that Glu-64, Thr-183, Arg-184, and Phe-185 residues might be involved in substrate binding and/or catalytic activity

Fusion of Bacillus stearothermophilus leucine aminopeptidase II with the raw-starch-binding domain of Bacillus sp strain TS-23 alpha-amylase generates a chimeric enzyme with enhanced thermostability and catalytic activity

Bacillus stearothermophilus leucine aminopeptidase 11 (LAPII) was fused at its C-terminal end with the raw-starch-binding domain of Bacillus sp. strain TS-23 alpha-amylase. The chimeric enzyme (LAPsbd), with an apparent molecular mass of approximately 61 kDa, was overexpressed in IPTG-induced Escherichia coli cells and purified to homogeneity by nickel-chelate chromatography. The purified enzyme retained LAP activity and adsorbed raw starch. LAPsbd was stable at 70degreesC for 10 min, while the activity of wild-type enzyme was completely abolished under the same environmental condition. Compared with the wild-type enzyme, the twofold increase in the catalytic efficiency for LAPsbd was due to a 218% increase in the k(cat) value

Statistical Theory of Spin Relaxation and Diffusion in Solids

A comprehensive theoretical description is given for the spin relaxation and diffusion in solids. The formulation is made in a general statistical-mechanical way. The method of the nonequilibrium statistical operator (NSO) developed by D. N. Zubarev is employed to analyze a relaxation dynamics of a spin subsystem. Perturbation of this subsystem in solids may produce a nonequilibrium state which is then relaxed to an equilibrium state due to the interaction between the particles or with a thermal bath (lattice). The generalized kinetic equations were derived previously for a system weakly coupled to a thermal bath to elucidate the nature of transport and relaxation processes. In this paper, these results are used to describe the relaxation and diffusion of nuclear spins in solids. The aim is to formulate a successive and coherent microscopic description of the nuclear magnetic relaxation and diffusion in solids. The nuclear spin-lattice relaxation is considered and the Gorter relation is derived. As an example, a theory of spin diffusion of the nuclear magnetic moment in dilute alloys (like Cu-Mn) is developed. It is shown that due to the dipolar interaction between host nuclear spins and impurity spins, a nonuniform distribution in the host nuclear spin system will occur and consequently the macroscopic relaxation time will be strongly determined by the spin diffusion. The explicit expressions for the relaxation time in certain physically relevant cases are given.Comment: 41 pages, 119 Refs. Corrected typos, added reference

The N-terminal signal sequence and the last 98 amino acids are not essential for the secretion of Bacillus sp TS-23 alpha-amylase in Escherichia coli

A truncated Bacillus sp. TS-23 alpha -amylase gene lacking 96 and 294 bp at its 5' and 3' end respectively was prepared by polymerase chain reaction and cloned into Escherichia coli expression vector, pQE-30, under the control of T5 promoter. SDS-PAGE and activity staining analyses showed that the His(6)-tagged amylase had a molecular mass of approximately 54 kDa. Isopropyl-beta -D-thiogalactopyranoside (IPTG) induction of E. coli M15 cells bearing the recombinant plasmid resulted in the extracellular production of active amylase. Western blot analysis also revealed that the truncated amylase was present in the periplasmic space and culture medium

Fusion of Bacillus stearothermophilus leucine aminopeptidase II with the raw-starch-binding domain of Bacillus sp strain TS-23 alpha-amylase generates a chimeric enzyme with enhanced thermostability and catalytic activity

Bacillus stearothermophilus leucine aminopeptidase 11 (LAPII) was fused at its C-terminal end with the raw-starch-binding domain of Bacillus sp. strain TS-23 alpha-amylase. The chimeric enzyme (LAPsbd), with an apparent molecular mass of approximately 61 kDa, was overexpressed in IPTG-induced Escherichia coli cells and purified to homogeneity by nickel-chelate chromatography. The purified enzyme retained LAP activity and adsorbed raw starch. LAPsbd was stable at 70degreesC for 10 min, while the activity of wild-type enzyme was completely abolished under the same environmental condition. Compared with the wild-type enzyme, the twofold increase in the catalytic efficiency for LAPsbd was due to a 218% increase in the k(cat) value

Identification of essential histidine residues in a recombinant alpha-amylase of thermophilic and alkaliphilic Bacillus sp strain TS-23

To understand the structure-function relationships of a truncated Bacillus sp. strain TS-23 alpha-amylase, each of His-137, His-191, His-239, His-269, His-305, His-323, His-361, His-436, and His-475 was replaced with leucine. The molecular masses of the purified wild-type and mutant enzymes were approximately 54 kDa. The specific activity of His323Leu and His436Leu was decreased by more than 52%, while His239Leu, His305Leu, and His475Leu showed activity similar to that of the wild-type enzyme. As compared with the wild-type enzyme, His323Leu and His436Leu exhibited a 62% decrease in the value of k(cat)/K-m. Alterations in His-191, His-239, His-305, and His-475 did not cause a significant change in the K-m or k(cat) values. At 70degreesC, a decreased half-life was observed in His436Leu. These results indicate that His-137, His-269, and His-361 of Bacillus sp. strain TS-23 alpha-amylase are important for proper catalytic activity and that His-436 may contribute to the thermostability of the enzyme

Cut Diagrams for High Energy Scatterings

A new approach is introduced to study QCD amplitudes at high energy and comparatively small momentum transfer. Novel cut diagrams, representing resummation of Feynman diagrams, are used to simplify calculation and to avoid delicate cancellations encountered in the usual approach. Explicit calculation to the 6th order is carried out to demonstrate the advantage of cut diagrams over Feynman diagrams.Comment: uu-encoded file containing a latex manuscript with 14 postscript figure

A systematic review of the effects of exercise interventions on body composition in HIV+ adults

Over the years, physical activity and exercise have been used to positively impact the health and quality of life of persons infected with HIV and, more recently, has been associated with a spectrum of body composition changes. The aim of this review was to examine the effects of various exercise interventions on body composition in HIV positive adults, using a search strategy of randomized, controlled trials (RCTs). A systematic review was performed by five independent reviewers using a predetermined protocol adapted from previous research for assessing the articles for inclusion, the extracted data, and methodological quality. Eight RCTs involving 430 (26% female) HIV positive adults performing exercise a minimum of thrice weekly for at least six weeks were finally selected: Four were progressive resistance training (PRT) studies, three were aerobic training (AT) studies, and one involved yoga. In the PRT studies, there were significant increases in three anthropometric measures, namely, body mass, sum of skinfolds and sum of limb girths. In the AT studies, significant decreases were found in seven anthropometric measures, namely, body mass index, waist-hip ratio, body mass, triceps skinfold, waist circumference and sum of skinfolds. With yoga, the changes were nonsignificant. Exercise contributes to improved body composition and, when applied safely, appears to be beneficial for adults living with HIV/AIDS. However, these findings should be interpreted cautiously due to the relatively few RCTs published to date. Future studies would benefit from increased attention to sample size, female participants, participant follow-up, complete statistical analysis and intention-to-treat analysis.Scopu