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Articles by J. Ma
Total Records ( 8 ) for J. Ma
  K. L Penney , F. R Schumacher , H Li , P Kraft , J. S Morris , T Kurth , L. A Mucci , D. J Hunter , P. W Kantoff , M. J Stampfer and J. Ma
 

The role of selenium in prostate cancer (PCa) risk remains controversial, but many epidemiologic studies suggest an inverse association with more aggressive disease. A recently discovered selenoprotein, SEP15, which is highly expressed in the prostate, may play a role either independently or by modifying the effects of selenium. We genotyped four common single-nucleotide polymorphisms capturing common variation (frequency >5%; R2 > 0.8) within SEP15, as well as rs5859 in the 3' untranslated region, previously reported to reduce the efficiency of selenium incorporation into SEP15. We examined the association of these single-nucleotide polymorphisms with PCa risk and PCa-specific mortality, as well as their interactions with plasma selenium levels, in the Physicians' Health Study. In this nested case-control study (1,286 cases and 1,267 controls), SEP15 polymorphisms were not significantly associated with PCa risk. However, among the cases, three variants were significantly associated with PCa-specific mortality [rs479341 hazard ratio (HR), 1.94; 95% confidence interval (95% CI), 1.15-3.25; rs1407131 HR, 2.85; 95% CI, 1.45-5.59; rs561104 HR, 1.54; 95% CI, 1.12-2.11] with a recessive model. Additionally, rs561104 significantly modified the association of plasma selenium with PCa survival (Pinteraction = 0.02); an inverse relationship of high levels of selenium with PCa mortality was apparent only among those without the increased risk genotype. This study provides evidence that SEP15 genetic variation may influence PCa mortality. Additionally, the association of selenium with PCa mortality was modified by a variant, suggesting the possibility that some men with PCa may benefit more from selenium than others, depending on their genotype. Cancer Prev Res; 3(5); 604–10. ©2010 AACR.

  H Li , M. J Stampfer , L Mucci , N Rifai , W Qiu , T Kurth and J. Ma
 

Background: Adipocytokines may mediate the association between adiposity and lethal prostate cancer outcomes.

Methods: In the Physicians’ Health Study, we prospectively examined the association of prediagnostic plasma concentrations of adiponectin and leptin with risk of developing incident prostate cancer (654 cases diagnosed 1982–2000 and 644 age-matched controls) and, among cases, risk of dying from prostate cancer by 2007.

Results: Adiponectin concentrations were not associated with risk of overall prostate cancer. However, men with higher adiponectin concentrations had lower risk of developing high-grade or lethal cancer (metastatic or fatal disease). The relative risk (95% CI) comparing the highest quintile to the lowest (Q5 vs Q1) was 0.25 (95% CI 0.07–0.87; Ptrend = 0.02) for lethal cancer. Among all the cases, higher adiponectin concentrations predicted lower prostate cancer–specific mortality [hazard ratio (HR)Q5 vs Q1= 0.39; 95% CI 0.17–0.85; Ptrend = 0.02], independent of body mass index (BMI), plasma C-peptide (a marker of insulin secretion), leptin, clinical stage, and tumor grade. This inverse association was apparent mainly among men with a BMI ≥25 kg/m2 (HRQ5 vs Q1= 0.10; 95% CI 0.01–0.78; Ptrend = 0.02), but not among men of normal weight (Ptrend = 0.51). Although the correlation of leptin concentrations with BMI (r = 0.58, P < 0.001) was stronger than that of adiponectin (r = –0.17, P < 0.001), leptin was unrelated to prostate cancer risk or mortality.

Conclusions: Higher prediagnostic adiponectin (but not leptin) concentrations predispose men to a lower risk of developing high-grade prostate cancer and a lower risk of subsequently dying from the cancer, suggesting a mechanistic link between obesity and poor prostate cancer outcome.

  J. Ma , A. N. Pilichiewicz , C. Feinle-Bisset , J. M. Wishart , K. L. Jones , M. Horowitz and C. K. Rayner
  Aims  Postprandial glucagon-like peptide-1 (GLP-1) secretion and the ‘incretin effect’ have been reported to be deficient in Type 2 diabetes, but most studies have not controlled for variations in the rate of gastric emptying. We evaluated blood glucose, and plasma insulin, GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) responses to intraduodenal glucose in Type 2 diabetes, and compared these with data from healthy controls.

Methods  Eight males with well-controlled Type 2 diabetes, managed by diet alone, were studied on four occasions in single-blind, randomized order. Blood glucose, and plasma insulin, GLP-1, and GIP were measured during 120-min intraduodenal glucose infusions at 1 kcal/min (G1), 2 kcal/min (G2) and 4 kcal/min (G4) or saline control.

Results  Type 2 patients had higher basal (P < 0.0005) and incremental (P < 0.0005) blood glucose responses to G2 and G4, when compared with healthy controls. In both groups, the stimulation of insulin and GLP-1 by increasing glucose loads was not linear; responses to G1 and G2 were minimal, whereas responses to G4 were much greater (P < 0.005 for each) (incremental area under the GLP-1 curve 224 ± 65, 756 ± 331 and 2807 ± 473 pmol/l.min, respectively, in Type 2 patients and 373 ± 231, 505 ± 161 and 1742 ± 456 pmol/l.min, respectively, in healthy controls). The GLP-1 responses appeared comparable in the two groups. In both groups there was a load-dependent increase in plasma GIP with no difference between them.

Conclusions  In patients with well-controlled Type 2 diabetes, blood glucose, insulin and GLP-1 responses are critically dependent on the small intestinal glucose load, and GLP-1 responses are not deficient.

  Z Tian , C Rizzon , J Du , L Zhu , J. L Bennetzen , S. A Jackson , B. S Gaut and J. Ma
 

In flowering plants, the accumulation of small deletions through unequal homologous recombination (UR) and illegitimate recombination (IR) is proposed to be the major process counteracting genome expansion, which is caused primarily by the periodic amplification of long terminal repeat retrotransposons (LTR-RTs). However, the full suite of evolutionary forces that govern the gain or loss of transposable elements (TEs) and their distribution within a genome remains unclear. Here, we investigated the distribution and structural variation of LTR-RTs in relation to the rates of local genetic recombination (GR) and gene densities in the rice (Oryza sativa) genome. Our data revealed a positive correlation between GR rates and gene densities and negative correlations between LTR-RT densities and both GR and gene densities. The data also indicate a tendency for LTR-RT elements and fragments to be shorter in regions with higher GR rates; the size reduction of LTR-RTs appears to be achieved primarily through solo LTR formation by UR. Comparison of indica and japonica rice revealed patterns and frequencies of LTR-RT gain and loss within different evolutionary timeframes. Different LTR-RT families exhibited variable distribution patterns and structural changes, but overall LTR-RT compositions and genes were organized according to the GR gradients of the genome. Further investigation of non-LTR-RTs and DNA transposons revealed a negative correlation between gene densities and the abundance of DNA transposons and a weak correlation between GR rates and the abundance of long interspersed nuclear elements (LINEs)/short interspersed nuclear elements (SINEs). Together, these observations suggest that GR and gene density play important roles in shaping the dynamic structure of the rice genome.

  N. P Tang , B Zhou , B Wang , R. B Yu and J. Ma
  Objective

A number of studies have evaluated the association between flavonoids intake and lung cancer risk. However, results were inconsistent. To clarify the role of flavonoids in lung cancer, we conducted a meta-analysis on this topic.

Methods

Two authors independently searched PubMed and EMBASE for studies regarding the association of flavonoids intake with lung cancer risk. Summary relative risks (RRs) with their corresponding 95% confidence intervals (CIs) were calculated by using random-effects model.

Results

Eight prospective studies and four case–control studies involving 5073 lung cancer cases and 237 981 non-cases were included in this meta-analysis. The combined results indicated a statistically significant association between highest flavonoids intake and reduced risk of developing lung cancer (RR = 0.76, 95% CI = 0.63–0.92). Furthermore, an increase in flavonoids intake of 20 mg/day was associated with a 10% decreased risk of developing lung cancer (RR = 0.90, 95% CI = 0.83–0.97). In stratified analyses, the highest flavonoids intake was significantly associated with decreased lung cancer risk in prospective studies, studies conducted in Finnish population, studies without adjustment for fruits and vegetables or vitamins, males, smokers and studies using dietary history interview for flavonoids intake estimation. Most subclasses of flavonoids were inversely associated with lung cancer except for hesperetin.

Conclusions

Our data indicate that high or an increased intake of flavonoids is associated with reduced risk of lung cancer in some population but not in other population.

  D. Li , J. Ma , S. Mukherjee , G. Bi , F. Zhao , S.L. Elizondo and Z. Shi
  The continual improvement of IV–VI materials grown by molecular beam epitaxy (MBE) is a key step in the development of IV–VI infrared semiconductor devices on silicon substrates. This study presents a novel surface-treatment method which is carried out during MBE growth of monocrystalline PbSe on Si(1 1 1)-oriented substrates. Details of the experimental procedures are described and supported by reflection high-energy electron diffraction (RHEED) patterns. The effect of the in-situ surface-treatment method is exhibited in the forms of improved electrical and morphological properties of PbSe thin films. Specially, the carrier mobility increases almost three-fold at 77 K and nearly two-fold at 300 K. The density of the growth pits undergoes almost three-fold reduction, whereas the density of the threading dislocations decreases around four-fold.
  M. J Xie , Y. G Ma , F Gao , Y. G Bai , J. H Cheng , Y. M Chang , Z. B Yu and J. Ma
 

Cerebral arterial remodeling is one of the critical factors in the occurrence of postspaceflight orthostatic intolerance. We hypothesize that large-conductance calcium-activated K+ (BKCa) channels in vascular smooth muscle cells (VSMCs) may play an important role in regulating cerebrovascular adaptation during microgravity exposure. The aim of this work was to investigate whether activation of BKCa channels is involved in regulation of apoptotic remodeling of cerebral arteries in simulated microgravity rats. In animal studies, Sprague-Dawley rats were subjected to 1-wk hindlimb unweighting to simulate microgravity. Alterations of BKCa channels in cerebral VSMCs were investigated by patch clamp and Western blotting; apoptosis was assessed by electron microscopy and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick-end labeling (TUNEL). To evaluate the correlation of BKCa channel and apoptosis, channel protein and cell nucleus were double-stained. In cell studies, hSlo+β1 channel was coexpressed into human embryonic kidney 293 (HEK293) cells to observe the effects of BKCa channels on apoptosis. In rats, enhanced activities and expression of BKCa channels were found to be correlated with increased apoptosis in cerebral VSMCs after simulated microgravity. In transfected HEK293 cells, activation of cloned BKCa channel induced apoptosis, whereas inhibition of cloned BKCa channel decreased apoptosis. In conclusion, activation of BKCa channels is associated with increased apoptosis in cerebral VSMCs of simulated microgravity rats.

  C Cai , N Weisleder , J. K Ko , S Komazaki , Y Sunada , M Nishi , H Takeshima and J. Ma
 

Defective membrane repair can contribute to the progression of muscular dystrophy. Although mutations in caveolin-3 (Cav3) and dysferlin are linked to muscular dystrophy in human patients, the molecular mechanism underlying the functional interplay between Cav3 and dysferlin in membrane repair of muscle physiology and disease has not been fully resolved. We recently discovered that mitsugumin 53 (MG53), a muscle-specific TRIM (Tri-partite motif) family protein (TRIM72), contributes to intracellular vesicle trafficking and is an essential component of the membrane repair machinery in striated muscle. Here we show that MG53 interacts with dysferlin and Cav3 to regulate membrane repair in skeletal muscle. MG53 mediates active trafficking of intracellular vesicles to the sarcolemma and is required for movement of dysferlin to sites of cell injury during repair patch formation. Mutations in Cav3 (P104L, R26Q) that cause retention of Cav3 in Golgi apparatus result in aberrant localization of MG53 and dysferlin in a dominant-negative fashion, leading to defective membrane repair. Our data reveal that a molecular complex formed by MG53, dysferlin, and Cav3 is essential for repair of muscle membrane damage and also provide a therapeutic target for treatment of muscular and cardiovascular diseases that are linked to compromised membrane repair.

 
 
 
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