Search PubMed⌕ Search

Biomedical subjects

Z Li

Publications and source records attributed to Z Li.

At least 109 records · Page 6Linked to original sources
PubMed2004

Domain-wall dynamics and spin-wave excitations with spin-transfer torques.

A generalization of spin-transfer torques in ferromagnetic structures is proposed. For a spatially nonuniform magnetization, the spin torque has a form nearly identical to that in magnetic multilayers. We show that the domain-wall motion driven by the current has many unique features that do not exist in the conventional domain-wall motion driven by a magnetic field. We also demonstrate that the spin torque can generate bulk and surface spin excitations that have been seen in point-contact experiments.

Journal Article↗
PubMed2004

Enzymatic properties and nucleotide and amino acid sequences of a thermostable beta-agarase from a novel species of deep-sea Microbulbifer.

An agar-degrading bacterium, strain JAMB-A7, was isolated from the sediment in Sagami Bay, Japan, at a depth of 1,174 m and identified as a novel species of the genus Microbulbifer. The gene for a novel beta-agarase from the isolate was cloned and sequenced. It encodes a protein of 441 amino acids with a calculated molecular mass of 48,989 Da. The deduced amino acid sequence showed similarity to those of known beta-agarases in glycoside hydrolase family 16, with only 34-55% identity. A sequence similar to a carbohydrate-binding module was found in the C-terminal region of the enzyme. The recombinant agarase was hyper-produced extracellularly using Bacillus subtilis as the host, and the enzyme purified to homogeneity had a specific activity of 398 U (mg protein)(-1) at pH 7.0 and 50 degrees C. It was thermostable, with a half-life of 502 min at 50 degrees C. The optimal pH and temperature for activity were around 7 and 50 degrees C, respectively. The pattern of agarose hydrolysis showed that the enzyme was an endo-type beta-agarase, and the final main product was neoagarotetraose. The activity was not inhibited by NaCl, EDTA, and various surfactants at high concentrations. In particular, sodium dodecyl sulfate had no inhibitory effect up to 2%.

Alteromonadaceae↗
PubMed2004

Absence of dystrophin in mice reduces NO-dependent vascular function and vascular density: total recovery after a treatment with the aminoglycoside gentamicin.

OBJECTIVE: Mutations in the dystrophin gene causing Duchenne's muscular dystrophy (DMD) lead to premature stop codons. In mice lacking dystrophin (mdx mice), a model for DMD, these mutations can be suppressed by aminoglycosides such as gentamicin. Dystrophin plays a role in flow (shear stress)-mediated endothelium-dependent dilation (FMD) in arteries. We investigated the effect of gentamicin on vascular contractile and dilatory functions, vascular structure, and density in mdx mice. METHODS AND RESULTS: Isolated mice carotid and mesenteric resistance arteries were mounted in arteriographs allowing continuous diameter measurements. Mdx mice showed lower nitric oxide (NO)-dependent FMD and endothelial NO synthase (eNOS) expression as well as decreased vascular density in gracilis and cardiac muscles compared with control mice. Treatment with gentamycin restored these parameters. In contrast, smooth muscle-dependent contractions as well as endothelium-dependent or -independent dilation were not affected by dystrophin deficiency or by gentamicin treatment. CONCLUSIONS: Dystrophin deficiency induces a selective defect in flow-dependent mechanotransduction, thus attenuating FMD and eNOS expression, and may contribute to low arteriolar density. These findings open important perspectives regarding the mechanism involved in the pathophysiology of genetic diseases related to premature stop codons such as DMD.

Animals↗
PubMed2004

Bacterial diversity in Malan ice core from the Tibetan Plateau.

Three ice core samples were collected from the Malan ice core drilled from the Tibetan Plateau, and three 16S rDNA clone libraries by direct amplification from the ice-melted water were established. Ninety-four clones containing bacterial 16S rDNA inserts were selected. According to restriction fragment-length polymorphism analysis, 11 clones were unique in the library from which they were obtained and used for partial sequence and phylogenetic analysis, and compared with 8 reported sequences from the same ice core at depth 70 m. Differences among the samples were apparent in clone libraries. The phylotypes were dominated by the Proteobacteria group, Acinetobacter sp. and Cytophaga-Flavobacterium-Bacteroides (CFB) group. They accounted for 92.5% (Proteobacteria), 100% (Acinetobacter sp.), 34.4% (CFB) and 100% (beta-Proteobacteria) in the clone libraries from the samples at ice depths 35, 64, 70, and 82 m, respectively. The Acinetobacter sp. was only found in the deposition at ice depth 82 m and closely clustered with gamma-Proteobateria. Two members (Malan A-21 and 101) of alpha-Proteobacteria from the sample of 35 m and two (Malan B-26 and 48) of beta-Proteobacteria of 64 m were loosely clustered (< 95% similarity) with known bacteria, represented new genera in ice bacteria.

Bacteria↗
PubMed2004

Molecular characterization of HMW glutenin subunit allele 1Bx14: further insights in to the evolution of Glu-B1-1 alleles in wheat and related species.

1Bx14 is a member of the high molecular weight (HMW) glutenin subunits specified by wheat Glu-B1-1 alleles. In this work, we found that the full-length amino acid sequence of 1Bx14 and 1Bx20, the last two of the three cysteine residues, which are conserved in 1Bx7, 1Bx17 and homologous 1Ax and 1Dx subunits, were replaced by tyrosine residues. In the 5' flanking regions (-900 to -1,200 bp relative to the start codon), a novel miniature inverted-repeat transposable element insertion was present in 1Bx12 and 1Bx20 but not 1Bx7 and 1Bx17. 1Bx14 and 1Bx20 like alleles were readily found in tetraploid wheat subspecies but not several S genome containing Aegilops species. Phylogenetic analysis showed that the four molecularly characterized Glu-B1-1 alleles (1Bx7, 1Bx14, 1Bx17, 1Bx20) could be divided into two allelic lineages. The lineage represented by 1Bx7 and 1Bx17 was more ancient than the one represented by 1Bx14 and 1Bx20. Combined, our data establish that 1Bx14 and 1Bx20 represent a novel subclass of Glu-B1-1 alleles. Based on current knowledge, potential mechanism involved in the differentiation of two Glu-B1-1 lineages is discussed.

Alleles↗
PubMed2004

Ethanol inhibits brain-derived neurotrophic factor-mediated intracellular signaling and activator protein-1 activation in cerebellar granule neurons.

Developmental exposure to ethanol causes profound damage to the cerebellum, ranging from aberration in neuronal differentiation to cell loss. As a major neurotrophic factor, brain-derived neurotrophic factor (BDNF) and its receptor TrkB are expressed in the developing, as well as adult, cerebellum. Many neurotrophic effects of BDNF are mediated by gene transcription. We hypothesized that ethanol interfered with BDNF signaling and disrupted BDNF-regulated transcriptional activity. Using a transgenic mouse model expressing an activator protein-1 (AP-1) luciferase reporter construct, we demonstrated that BDNF stimulated AP-1 transactivation in cultured cerebellar granule neurons. This observation was validated by the study using a human neuronal cell line expressing inducible TrkB (TB8 neuroblastoma cells). BDNF induced AP-1 transactivation, as well as increased the binding activity of AP-1 protein complex to a DNA sequence containing AP-1 sites in TB8 cells. BDNF-mediated AP-1 activation was mediated by PI3K/Akt and JNK pathways; BDNF activated Akt and JNKs, and blocking these pathways significantly inhibited BDNF-stimulated AP-1 transactivation. More importantly, ethanol inhibited BDNF-mediated activation of PI3K/Akt and JNKs, and blocked BDNF-stimulated AP-1 activation. Since ethanol did not affect either the expression or autophosphorylation of TrkB, it could be concluded that the site of ethanol action was downstream of TrkB. The present study establishes that this AP-1 reporter transgenic mouse model is valuable for assessing AP-1 activity in the CNS neurons. Our results provide an insight into molecular mechanism(s) of ethanol action.

Animals↗
PubMed2004

Feasibility of a partial meal replacement plan for weight loss in low-income patients.

BACKGROUND: Low-income patients are disproportionately affected by obesity. Routine care is available to this population at the Venice Family Clinic (VFC) in Los Angeles. The current study examined the effectiveness of nutrition clinic utilizing meal replacements (Slim-Fast, Slim-Fast Foods Co., FL, USA) in low-income patients over a 6-month period compared with the routine care by their primary care physician (PMD) prior to enrolling in the nutrition clinic at similar time intervals. METHODS: In total, 63 patients (51 F; 49+/-0.8 yo) who had been followed at the VFC by their PMD for at least 6 months were enrolled in this study. Patients had a body mass index (BMI) of 40+/-1.1 kg/m2, were 72% Hispanic, 25% Caucasian, and 3% African American. They had the following co-morbidities: hypertension (HTN) 45%, diabetes mellitus II (DM II) 50%, gastroesophageal reflux disease (GERD) 34%, osteoarthritis 51%, and hypercholesterolemia 48%. All patients were provided with meal replacements to be taken twice a day and were instructed to consume one complete low calorie meal per day. Weights at the first visit to the nutrition clinic, 1, 3, and 6 months after enrollment in nutrition clinic were compared to their weights at the same time intervals during routine visits to their PMD prior to enrollment in the nutrition clinic. RESULTS: There was no significant weight change during the 6 months prior to enrollment in the nutrition program despite receiving care by a PMD. At 6 months after participating in the nutrition program, there was a mean decrease of 7% body weight with a reduction in BMI from 40-37 kg/m2 (P< or =0.05). CONCLUSION: Implementation of nutrition clinic utilizing meal replacements in this low-income patient population was effective in achieving a significant reduction in weight over 6 months of treatment..

Adult↗
PubMed2004

On the power of affected relative pair designs for linkage studies.

Using the recurrence risk ratio (lambda), Risch (1990b) indicated that affected pairs of distant relatives are preferable to affected sib-pairs for linkage analysis when lambda is large and the mode of inheritance is additive. By using the optimum test for affected sib-pairs instead of the test used by Risch (1990b), the range of values of lambda for which the affected sib-pair design has larger or smaller power than other pairs is clarified. Risch's conclusion remains true when lambdaO > 2.5, however, sib-pairs have larger power for lower values. As affected sib-pairs occur smore frequently than other relative pairs, when ascertainment costs are non-negligible, they may be the most cost-effective relative pairs to use.

Genetic Linkage↗
PubMed2004

Molecular monitoring and evaluation of the application of the insect-pathogenic fungus Beauveria bassiana in southeast China.

AIMS: To monitor the fate of inundatively applied strains of Beauveria bassiana against Masson's pine caterpillar, Dendrolimus punctatus, in Magushan Forest, southeast China, and evaluate the potential environmental risks of biocontrol introduction. METHODS AND RESULTS: Filed samplings of mycosed cadavers were carried out continuously for more than one year after the inundative applications of two exotic B. bassiana strains. By employing four complementary molecular markers, the purified cultures from collections were characterized and the two released strains Bb17 and Bb13 were recovered with respective frequencies of 9.1 and 5.2%. The released strains were isolated from nontarget hosts. The genetic diversity of the population of B. bassiana in the trial plot changed dynamically over time and no single genotype strain dominated throughout the sampling period or at different seasons. The indigenous strains were observed to be predominant in the local environment. Co-infection and/or genetic recombination might occur between strains under natural conditions. CONCLUSION: Field applications of the biocontrol agent B. bassiana appear to pose no major risk to the environment. There was no evidence of displacement of indigenous strains of B. bassiana. SIGNIFICANCE AND IMPACT OF THE STUDY: The results indicate that the introduction of exotic B. bassiana strains can persist in local environment and infect nontarget insect hosts, highlighting the importance of safety assessment of the large-scale application of fungal biocontrol agents.

Animals↗
PubMed2004

Hepatic fibrogenesis requires sympathetic neurotransmitters.

BACKGROUND AND AIMS: Hepatic stellate cells (HSC) are activated by liver injury to become proliferative fibrogenic myofibroblasts. This process may be regulated by the sympathetic nervous system (SNS) but the mechanisms involved are unclear. METHODS: We studied cultured HSC and intact mice with liver injury to test the hypothesis that HSC respond to and produce SNS neurotransmitters to promote fibrogenesis. RESULTS: HSC expressed adrenoceptors, catecholamine biosynthetic enzymes, released norepinephrine (NE), and were growth inhibited by alpha- and beta-adrenoceptor antagonists. HSC from dopamine beta-hydroxylase deficient (Dbh(-/-)) mice, which cannot make NE, grew poorly in culture and were rescued by NE. Inhibitor studies demonstrated that this effect was mediated via G protein coupled adrenoceptors, mitogen activated kinases, and phosphatidylinositol 3-kinase. Injury related fibrogenic responses were inhibited in Dbh(-/-) mice, as evidenced by reduced hepatic accumulation of alpha-smooth muscle actin(+ve) HSC and decreased induction of transforming growth factor beta1 (TGF-beta1) and collagen. Treatment with isoprenaline rescued HSC activation. HSC were also reduced in leptin deficient ob/ob mice which have reduced NE levels and are resistant to hepatic fibrosis. Treating ob/ob mice with NE induced HSC proliferation, upregulated hepatic TGF-beta1 and collagen, and increased liver fibrosis. CONCLUSIONS: HSC are hepatic neuroglia that produce and respond to SNS neurotransmitters to promote hepatic fibrosis.

Animals↗
PubMed2004

Reduced inspiratory flow attenuates IL-8 release and MAPK activation of lung overstretch.

Lung overstretch involves mechanical factors, including large tidal volumes (VT), which induce inflammatory responses. The current authors hypothesised that inspiratory flow contributes to ventilator-induced inflammation. Buffer-perfused rabbit lungs were ventilated for 2 h with 21%, O2+5%, CO2, positive end-expiratory pressure of 2-3 cmH2O and randomly assigned to either: 1) normal VT (6 mL x kg(-1)) at respiratory rate (RR) 30, inspiration:expiration time ratio (I:E) 1:1, low inspiratory flow 6 mL x kg(-1) x s(-1); 2) large VT (12 mL x kg(-1)) at RR 30, I:E 1:1, high inspiratory flow 12 mL x kg(-1) x s(-1) (HRHF); 3) large VT at RR 15, I:E 1:1, low inspiratory flow 6 mL x kg(-1) x s(-1) (LRLF); or 4) large VT at RR 15, I:E 1:2.3, high inspiratory flow 10 mL x kg(-1) x s(-1) (LRHF). Physiological parameters, tumour necrosis factor (TNF)-alpha, interleukin (IL)-8 and activation of mitogen-activated protein kinases (extracellular signal-regulated kinase (ERK)1/2, p38 and stress-activated protein kinase (SAPK)/ c-Jun N-terminal kinase (JNK)) were measured. HRHF increased weight gain, perfusate IL-8 and phosphorylation of ERK1/2, p38 and SAPK/JNK. These responses were absent during LRLF but present during LRHF. Changes in TNF-alpha were small. Tissue IL-8 and phospho-ERK1/2 staining was localised primarily to smooth muscle, adventitia and bronchial epithelium within larger bronchioles and arterioles. These results indicate that mild overstretch of perfused lungs during high inspiratory flow enhances inflammatory signalling by cells in lung regions most affected by strong turbulent airflow.

Analysis of Variance↗
PubMed2004

Two-year efficacy and tolerability of risedronate once a week for the treatment of women with postmenopausal osteoporosis.

OBJECTIVE: The efficacy and tolerability of risedronate once-a-week dosing (35 and 50mg) were compared with risedronate daily dosing (5mg) in a 2-year study in women with osteoporosis. DESIGN AND METHODS: This was a randomized, double-blind, active-control study with lumbar spine bone mineral density (BMD) as the primary efficacy endpoint at 1 year. Subjects were women aged 50 years or older, postmenopausal for at least 5 years, and had either a BMD T-score of -2.5 or lower (lumbar spine or total proximal femur) or a T-score lower than -2 and at least one prevalent vertebral fracture. In addition to risedronate treatment, the subjects received 1000 mg daily of elemental calcium supplementation and received vitamin D if the baseline serum 25-hydroxyvitamin D(3) level was low. RESULTS: The results after 1 year of treatment were previously published. Of the 1456 women who were randomized and received study medication, 1127 (77%) completed the 2-year study. Over the 2 years of treatment, the incidence of both new vertebral fractures (2.9, 1.5, and 1.7% for the 5, 35, and 50 mg groups, respectively; for women with postmenopausal osteoporosis who p = 0.298) and osteoporosis-related non-vertebral fractures reported as adverse events (5.0, 4.9, and 4.5% for the 5, 35, and 50 mg groups, respectively; p = 0.918) was similar for all 3 treatment groups. The reduction from baseline at Month 24 in bone turnover markers was similar based on an analysis of variance for the 5 mg daily and the 35 mg once-a-week groups. The mean percentage change in lumbar spine BMD after 24 months was 5.17, 4.74, and 5.47% for the 5, 35, and 50 mg groups, respectively. Both the 35 and 50 mg once-a-week treatment groups met the pre-specified criterion of non-inferiority to the 5 mg daily treatment group. No apparent difference in the pattern or distribution of serious and upper gastrointestinal adverse events was observed. CONCLUSIONS: The 2-year data agree with the 1-year results demonstrating that the risedronate once-a-week doses are comparable in efficacy and safety to the 5 mg daily dose. Risedronate 35 mg once a week is considered the optimal dose want a once-a-week dosing regimen.

Aged↗
PubMed2004

Statistical validation of surrogate endpoints: is bone density a valid surrogate for fracture?

In the treatment of osteoporosis using anti-resorptive agents there has been increasing interest in quantifying the relationship between fracture endpoints and surrogates such as bone mineral density (BMD) or bone turnover markers. Statistical methodology constitutes a critical component of assessing surrogate validity. Depending on study designs, data resources, and statistical methods used for analyses, one has to use caution when interpreting results from different analyses, especially when results are disparate. For example, analyses based on individual patient data reported that only a limited proportion of the anti-fracture efficacy was explained by BMD increases for agents such as alendronate, risedronate and raloxifene. Analyses employing meta-regression based on summary statistics, however, indicated that most of the anti-fracture benefits were due to improvements in BMD. In this paper, we review definitions of surrogate endpoints and requirements for their statistical validation. We evaluate whether BMD meets these requirements as a possible surrogate for fracture. Our review indicates that the actual BMD value is correlated with fracture risk and thus BMD is useful in identifying patients that might need treatment. There is limited evidence to support BMD increase with anti-resorptive agents as a reliable substitute for fracture risk reduction. Strengths and limitations for various statistical methods are discussed.

Biomarkers↗
PubMed2003

Energetic protons from a few-micron metallic foil evaporated by an intense laser pulse.

With detailed experimental studies and hydrodynamics and particle-in-cell simulations we investigate the role of the prepulse in laser proton acceleration. The prepulse or pedestal (amplified spontaneous emission) can completely evaporate the irradiated region of a sufficiently thin foil; therefore, the main part of the laser pulse interacts with an underdense plasma. The multiparametric particle-in-cell simulations demonstrate that the main pulse generates the quasistatic magnetic field, which in its turn produces the long-lived charge separation electrostatic field, accelerating the ions.

Journal Article↗
PubMed2003

Deep vein thrombosis and air travel: record linkage study.

OBJECTIVE: To investigate the time relations between long haul air travel and venous thromboembolism. DESIGN: Record linkage study using the case crossover approach. SETTING: Western Australia. PARTICIPANTS: 5408 patients admitted to hospital with venous thromboembolism and matched with data for arrivals of international flights during 1981-99. RESULTS: The risk of venous thromboembolism is increased for only two weeks after a long haul flight; 46 Australian citizens and 200 non-Australian citizens had an episode of venous thromboembolism during this so called hazard period. The relative risk during this period for Australian citizens was 4.17 (95% confidence interval, 2.94 to 5.40), with 76% of cases (n = 35) attributable to the preceding flight. A "healthy traveller" effect was observed, particularly for Australian citizens. CONCLUSIONS: The annual risk of venous thromboembolism is increased by 12% if one long haul flight is taken yearly. The average risk of death from flight related venous thromboembolism is small compared with that from motor vehicle crashes and injuries at work. The individual risk of death from flight related venous thromboembolism for people with certain pre-existing medical conditions is, however, likely to be greater than the average risk of 1 per 2 million for passengers arriving from a flight. Airlines and health authorities should continue to advise passengers on how to minimise risk.

Adolescent↗
PubMed2003

Strong energy dependence of the electron-phonon coupling strength on Bi(100).

We have studied the energy dependence of the electron-phonon coupling strength on Bi(100). A fit of the temperature-dependent surface state linewidth results in a change of the coupling parameter lambda from 0.20+/-0.02 to 0.72+/-0.05 as the binding energy of the surface state increases from 70 to 330 meV. This result cannot be reconciled with the usual interpretation of lambda as the electron-phonon mass enhancement parameter at the Fermi energy. We suggest that this behavior is mainly caused by the strong energy dependence of the bulk density of states in this region.

Journal Article↗
PubMed2003

Mapping osmotic adjustment in an advanced back-cross inbred population of rice.

Osmotic adjustment is one of several characters putatively associated with drought tolerance in rice. Indica cultivars are known to have a greater capacity for osmotic adjustment than japonica cultivars. We developed an advanced back-cross population using an indica donor, IR62266-42-6-2, to introgress osmotic adjustment into an elite japonica cultivar, IR60080-46A. One hundred and fifty BC(3)F(3) families were genotyped using microsatellites and RFLP markers, and a few candidate genes. We evaluated osmotic adjustment in these lines under greenhouse conditions using the re-hydration technique. Using the composite interval mapping technique, we detected 14 QTLs located on chromosomes 1, 2, 3, 4, 5, 7, 8 and 10 that together explained 58% of the phenotypic variability. Most, but not all, of the alleles with positive effects came from the donor parent. On chromosome 8, two QTLs were associated in repulsion. The QTL locations were in good agreement with previous studies on this trait on rice and in other cereals. Some BC(3)F(3) lines carried the favorable alleles at the two markers flanking up to four QTLs. Intercrossing these lines followed by marker-aided selection in their progenies will be necessary to recover lines with levels of osmotic adjustment equal to the donor parent. The advanced back-cross strategy appeared to be an appropriate method to accelerate the process of introgressing interesting traits into elite material.

Adaptation, Psychological↗