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Biomedical subjects

Wei Shen

Publications and source records attributed to Wei Shen.

At least 55 records · Page 3Linked to original sources
PubMed2006

[The effectiveness of endoscopic variceal ligation in patients with different grades of liver function].

OBJECTIVE: To evaluate the effectiveness of endoscopic variceal ligation (EVL) in patients with different grades of liver function. METHODS: MELD scores were determined for 156 patients before their EVL operations. After the EVL these patients were followed-up and their survival rates were analyzed. RESULTS: Fifty percent of the patients whose MELDs were less than or equal to 7 survived longer than 45 months after the EVL; in those with MELDs between 7 and 9, 50% of the patients survived 47.34 months; however, the figure for those whose MELD were more than 9 survived only 24.89 months. In the first two groups, 50% of the patient' survival duration was significantly longer than that of the third group. The difference was statistically significant. CONCLUSION: EVL becomes an effective clinical way to treat hemorrhage of esophagus varicose veins. The survival rate for this procedure is directly correlated with the liver function of the patient before the EVL.

Adult↗
PubMed2005

A novel organoclay with antibacterial activity prepared from montmorillonite and Chlorhexidini Acetas.

A series of novel organoclays with antibacterial activity were synthesized using Ca-montmorillonite and Chlorhexidini Acetas (CA) by ion-exchange. The resultant organoclays were characterized using X-ray diffraction (XRD), high-resolution thermogravimetric analysis (HRTG) and Fourier transform infrared spectroscopy (FTIR). Their antibacterial activity was assayed by so-called halo method. In the organoclays prepared at low CA concentration, CA ions within the clay interlayer adopt a lateral monolayer while a 'kink' state or a special state with partial overlapping of the intercalated CA in the organoclays prepared at 1.0-4.0 CEC. HRTG analysis demonstrates that CA located outside the clay interlayer exists in all synthesized organoclays, resulting from the complex molecular configuration of CA. The dramatic decrease of the surface adsorbed water and interlayer water is caused by the surface property transformation and the replacement of hydrated cations by cationic surfactant. These observations are supported by the results of FTIR. Antibacterial activity test against E. coli demonstrates that the antibacterial activity of the resultant organoclays strongly depends on the content of CA. Meanwhile, the resultant organoclay shows a long-term antibacterial activity that can last for at least one year. These novel organoclays are of potential use in synthesis of organoclay-based materials with antibacterial activity.

Adsorption↗
PubMed2005

The combined use of ibutilide as an active control with intensive electrocardiographic sampling and signal averaging as a sensitive method to assess the effects of tadalafil on the human QT interval.

OBJECTIVES: This study was designed to evaluate effects of tadalafil, a phosphodiesterase-5 inhibitor used for the treatment of erectile dysfunction (ED), on the QT interval. BACKGROUND: Cardiovascular disease is common in men with ED. Men with cardiovascular disease and ED may have decreased cardiac repolarization reserve. METHODS: Effects of tadalafil (100 mg by mouth), ibutilide (0.002 mg/kg intravenously), and placebo on the QT interval in healthy men were compared (placebo and tadalafil [n = 90], with a subset [n = 61] receiving all treatments; mean age 30 years, range 18 to 53 years). Electrocardiographic sampling was done for two days before treatment and on treatment days. The QT was corrected for RR interval with five correction methods, including an individual correction (QTcI). Plasma concentrations of tadalafil were measured to evaluate concentration-QT effect relationships. RESULTS: At the time corresponding to maximum plasma concentration of tadalafil, the mean difference in the change in QTcI between tadalafil and placebo was 2.8 ms; tadalafil was equivalent to placebo (a priori, upper limit of 90% confidence interval < 10 ms [actual = 4.4 ms]; post hoc, upper limit of 95% confidence interval < 5 ms [actual = 4.8]). The active control, ibutilide, significantly increased QTcI by 6.9 and 8.9 ms compared with tadalafil and placebo, respectively. Similar statistical results were obtained with four additional QT correction methods. No subject had a QTcI > or = 450 ms or an increase in QTcI > or = 30 ms with any treatment. CONCLUSIONS: Based on the a priori statistical test of equivalence, placebo and high-dose tadalafil produced equivalent effects on the QT interval. This study reliably discerned 5- to 10-ms changes in corrected QT in the ibutilide active control group.

Adolescent↗
PubMed2005

Selective synthesis of single-crystalline selenium nanobelts and nanowires in micellar solutions of nonionic surfactants.

Single-crystalline nanobelts and nanowires of trigonal selenium (t-Se) have been selectively synthesized in micellar solutions of nonionic surfactants. In particular, t-Se nanobelts about 30 nm in thickness were obtained in micellar solutions of poly(oxyethylene(20)) octadecyl ether (C18EO20), whereas t-Se nanowires were obtained in micellar solutions of poly(oxyethylene(10)) dodecyl ether (C12EO10). The obtained t-Se nanobelts exhibit a low-energy absorption peak that is considerably red shifted from that for t-Se nanowires, which has been presumably attributed to the lower degree of crystal perfection for the t-Se nanobelts with rectangular cross sections.

Journal Article↗
PubMed2005

Analysis of KIT mutations in sporadic and familial gastrointestinal stromal tumors: therapeutic implications through protein modeling.

PURPOSE: Gastrointestinal stromal tumors (GIST) are characterized by expressing a gain-of-function mutation in KIT, and to a lesser extent, PDGFR. Imatinib mesylate, a tyrosine kinase inhibitor, has activity against GISTs that contain oncogenic mutations of KIT. In this study, KIT and PDGFRalpha mutation status was analyzed and protein modeling approaches were used to assess the potential effect of KIT mutations in response to imatinib therapy. EXPERIMENTAL DESIGN: Genomic DNA was isolated from GIST tumors. Exons 9, 11, 13, and 17 of c-KIT and exons 12, 14, and 18 of PDGFRalpha were evaluated for oncogenic mutations. Protein modeling was used to assess mutations within the juxtamembrane region and the kinase domain of KIT. RESULTS: Mutations in KIT exons 9, 11, and 13 were identified in GISTs with the majority of changes involving the juxtamembrane region of KIT. Molecular modeling indicates that mutations in this region result in disruption of the KIT autoinhibited conformation, and lead to gain-of-function activation of the kinase. Furthermore, a novel germ-line mutation in KIT was identified that is associated with an autosomal dominant predisposition to the development of GIST. CONCLUSIONS: We have used protein modeling and structural analyses to elucidate why patients with GIST tumors containing exon 11 mutations are the most responsive to imatinib mesylate treatment. Importantly, mutations detected in this exon and others displayed constitutive activation of KIT. Furthermore, we have found tumors that are both KIT and PDGFRalpha mutation negative, suggesting that additional, yet unidentified, abnormalities may contribute to GIST tumorigenesis.

Adult↗
PubMed2005

Isolation and sequence analysis of the gene URA3 encoding the orotidine-5'-phosphate decarboxylase from Candida glycerinogenes WL2002-5, an industrial glycerol producer.

The URA3 gene of Candida glycerinogenes WL2002-5, an industrial glycerol producer encoding orotidine-5'-phosphate decarboxylase enzyme, was isolated by complementation cloning in Saccharomyces cerevisiae. DNA sequence analysis revealed the presence of an open reading frame (ORF) of 786 bp, encoding a 262 amino acid protein, which shares 71.65% amino acid sequence similarity to the S. cerevisiae URA3 protein. Furthermore, the cloned ORF fully complemented the ura3 mutation of S. cerevisiae, confirming that it encodes for the C. glycerinogenes Ura3 (CgUra3) protein.

Amino Acid Sequence↗
PubMed2005

Defective p38 mitogen-activated protein kinase signaling impairs chemotaxic but not proliferative responses to stromal-derived factor-1alpha in acute lymphoblastic leukemia.

The chemokine stromal-derived factor-1alpha (SDF-1alpha) regulates leukemic cell motility and proliferation; however, the importance of these functions in the growth and dissemination of leukemia is unclear. We examined SDF-1alpha-mediated responses of cells from 27 cases of acute lymphoblastic leukemia (ALL). Although cells from the majority of cases showed chemotactic and proliferative responses to SDF-1alpha, a subset of cases did not undergo chemotaxis in response to SDF-1alpha, while still demonstrating dependence on SDF-1alpha for proliferation in stroma-supported cultures. This chemotactic defect was associated with an absence of phosphorylation of p38 mitogen-activated protein kinase (MAPK) induced by SDF-1alpha, and of SDF-1alpha-induced augmentation of beta(1) integrin-mediated adhesion. Signaling through phosphoinositide 3-kinase and MEK was not affected. No correlation was observed between CXCR4 expression and chemotactic function, in vitro migration into bone marrow stromal layers, and engraftment of leukemic cells in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice. This study suggests that signaling through p38 MAPK is required for ALL cell chemotaxis but not for proliferation, and that the loss of a chemotactic response to SDF-1alpha does not impede engraftment in NOD/SCID mice.

Adolescent↗
PubMed2005

Musculoskeletal gene therapy and its potential use in the treatment of complicated musculoskeletal infection.

Tissue repair is a major issue in orthopedics. Many musculoskeletal tissues, including cartilage, meniscus, and the anterior cruciate ligament, heal poorly after injury. Recent studies have led to the identification of numerous growth factors and other gene products that can promote the regeneration of damaged musculoskeletal tissues. In the last century, the discovery and evolving use of antibiotics has significantly decreased the prevalence and severity of infectious diseases. In many orthopedic scenarios, however, treatment of infections can be difficult, and often involves a prolonged course of antibiotics with concomitant surgical interventions and loss of tissue. Although studies have demonstrated the successful transfer of target genes and the associated manipulation of the musculoskeletal tissue environment, researchers have made few attempts designed to use gene therapy to treat infectious musculoskeletal diseases in animal models. Before it is possible to use gene-based approaches to treat such diseases effectively, researchers must perform more studies to investigate the potential problems that may arise when using gene therapy in an infectious environment.

Bone Diseases↗
PubMed2005

NS-398, a cyclooxygenase-2-specific inhibitor, delays skeletal muscle healing by decreasing regeneration and promoting fibrosis.

Nonsteroidal anti-inflammatory drugs are often prescribed after muscle injury. However, the effect of nonsteroidal anti-inflammatory drugs on muscle healing remains primarily controversial. To further examine the validity of using these drugs after muscle injury, we investigated the working mechanism of NS-398, a cyclooxygenase-2-specific inhibitor. In vitro experiments showed that NS-398 inhibited the proliferation and maturation of differentiated myogenic precursor cells, suggesting a detrimental effect on skeletal muscle healing. Using a mouse laceration model, we analyzed the in vivo effect of NS-398 on skeletal muscle healing at time points up to 4 weeks after injury. The in vivo results revealed delayed muscle regeneration at early time points after injury in the NS-398-treated mice. Compared to controls, lacerated muscles treated with NS-398 expressed higher levels of transforming growth factor-beta1, which corresponded with increased fibrosis. In addition, transforming growth factor-beta1 co-localized with myostatin, a negative regulator of skeletal muscle growth. We also found reduced neutrophil and macrophage infiltration in treated muscles, indicating that the delayed skeletal muscle healing observed after NS-398 treatment could be influenced by the anti-inflammatory effect of NS-398. Our findings suggest that the use of cyclooxygenase-2-specific inhibitors to treat skeletal muscle injuries warrants caution because they may interfere with muscle healing.

Animals↗
PubMed2005

Four-compartment cellular level body composition model: comparison of two approaches.

OBJECTIVE: The aim of this study was to develop and compare two DXA-based four-compartment [body weight=body cell mass (BCM)+extracellular fluid (ECF)+extracellular solids (ECS)+fat] cellular level models. RESEARCH METHODS AND PROCEDURES: Total body potassium (TBK) model: BCM from TBK by whole-body counting-ECF(TBK)=LST-[BCM(TBK)+0.73 x osseous mineral (Mo)]. Bromide model: ECF from sodium bromide dilution-BCM(BROMIDE)=LST-(ECF(BROMIDE)+0.73xMo); Mo and LST measurements came from DXA. The two approaches were evaluated in 99 healthy men and 118 women. RESULTS: BCM estimates were highly correlated (r=0.97, p<0.001), as were ECF estimates (r=0.87, p<0.001); a small statistically significant mean difference was present (mean+/-SD; BCM(TBK) model, 30.4+/-8.9 kg; BCM(BROMIDE), 31.4+/-9.3 kg; Delta=1.0+/-2.8 kg; p<0.001; ECF(TBK), 18.5+/-4.2 kg; ECF(BROMIDE), 17.5+/-3.6 kg; Delta=1.0+/-2.8 kg; p<0.001). A high correlation (r=0.97, p<0.001) and good agreement (38.9+/-9.5 vs. 38.9+/-9.5 kg; Delta=0.0+/-2.4 kg; p=0.39) were present between TBW, derived as the sum of intracellular water from TBK and ECW from bromide, and measured TBW by 2H2O dilution. DISCUSSION: Two developed four-compartment cellular level DXA models, one of which is appropriate for use in most clinical and research settings, provide comparable results and are applicable for BCM and ECF estimation of subject groups with hydration disturbances.

Absorptiometry, Photon↗
PubMed2005

A cellular-level approach to predicting resting energy expenditure across the adult years.

BACKGROUND: We previously derived a whole-body resting energy expenditure (REE) prediction model by using organ and tissue mass measured by magnetic resonance imaging combined with assumed stable, specific resting metabolic rates of individual organs and tissues. Although the model predicted REE well in young persons, it overpredicted REE by approximately 11% in elderly adults. This overprediction may occur because of a decline in the fraction of organs and tissues as cell mass with aging. OBJECTIVE: The aim of the present study was to develop a cellular-level REE prediction model that would be applicable across the adult age span. Specifically, we tested the hypothesis that REE can be predicted from a combination of organ and tissue mass, the specific resting metabolic rates of individual organs and tissues, and the cellular fraction of fat-free mass. DESIGN: Fifty-four healthy subjects aged 23-88 y had REE, organ and tissue mass, body cell mass, and fat-free mass measured by indirect calorimetry, magnetic resonance imaging, whole-body (40)K counting, and dual-energy X-ray absoptiometry, respectively. RESULTS: REE predicted by the cellular-level model was highly correlated with measured REE (r = 0.92, P < 0.001). The mean difference between measured REE (x+/- SD: 1487 +/- 294 kcal/d) and predicted REE (1501 +/- 300 kcal/d) for the whole group was not significant, and the difference between predicted and measured REE was not associated with age (r = 0.009, NS). CONCLUSION: The present approach establishes an REE-body composition link with the use of a model at the cellular level. The combination of 2 aging-related factors (ie, decline in both the mass and the cellular fraction of organs and tissues) may account for the lower REE observed in elderly adults.

Absorptiometry, Photon↗
PubMed2005

The efficacy of tadalafil in clinical populations.

OBJECTIVES: To evaluate the efficacy of tadalafil in men with erectile dysfunction (ED) by demographic and ED characteristics, in patients having various comorbid medical conditions, and in patients receiving drug treatment for other medical conditions. METHODS: This is an analysis of 11 double-blind, placebo-controlled trials with 2,102 men with a broad spectrum of ED etiology and various comorbid medical conditions as participants. The variables analyzed in this report included race, age, body mass index (BMI), ED etiology, ED severity, ED duration, smoking, prior sildenafil use, presence of comorbid conditions (diabetes mellitus, hypertension, cardiovascular disease, hyperlipidemia, depression, benign prostatic hyperplasia), and treatment with antihypertensives or antidepressants. Patients were randomly assigned to receive tadalafil 10 mg (N=321), tadalafil 20 mg (N=1,143), or placebo (N=638). The primary efficacy variables included mean changes from baseline in the erectile function (EF) domain score of the International Index of Erectile Function (IIEF) questionnaire, and the mean per-patient percentage of "yes" responses to the Sexual Encounter Profile (SEP) diary question 3 (SEP3--successful intercourse). The Global Assessment Question 1 (GAQ) was evaluated, as was the percentage of men attaining a normal IIEF EF domain score at end point. RESULTS: Patients taking tadalafil 10 mg or 20 mg demonstrated significant improvement (P<0.005) from baseline to end point on the IIEF EF domain score in all subpopulations analyzed compared with patients receiving placebo. The mean-per-patient percentage of "yes" responses to SEP3 increased significantly in all subpopulations taking tadalafil compared with placebo (P<0.05). Tadalafil-treated patients had a significantly greater positive response rate on the GAQ in all subpopulations analyzed compared with placebo-treated patients (P<0.03) except for the tadalafil 10 mg cardiovascular subpopulation (placebo, 46.8%; tadalafil 10 mg, 71.0%; P=0.127). The percentage of positive responses ranged from 72% to 91% for patients on tadalafil 20 mg and from 52% to 94% for tadalafil 10 mg compared with a range of 20% to 47% for placebo-treated patients. CONCLUSIONS: Tadalafil was effective in improving erectile function across a wide spectrum of ED patients including patients with various comorbid conditions.

Adult↗
PubMed2005

Differential behavior of simple and complex cells in visual cortex during a brief IOP elevation.

PURPOSE: To study and compare responses of different types of cortical neurons in the primary visual cortex in cats to grating stimuli before and during brief elevation of intraocular pressure (IOP). METHODS: Single-unit electrophysiological recordings were performed in anesthetized and paralyzed cats. The IOP was elevated by injecting saline into the anterior chamber of the cat's eyes through a syringe needle. The IOP was elevated to a level at which the retinal perfusion pressure (arterial pressure minus IOP) was maintained at approximately 30 mmHg for a period of 4 minutes. The responses of simple and complex cells in the primary visual cortex to visually drifting sinusoidal gratings were measured before and during the elevation of IOP. RESULTS: The response amplitude of all the cortical cells in the primary visual cortex declined during a brief elevation of IOP. The decrease in the response of simple cells was always more significant than that of complex cells. The differential decrease between the two major types of cells was independent of the cell's receptive field location and cortical depth. There was a mild tendency for cells with higher preferred spatial frequencies to be more sensitive than those with lower frequencies. The preferred orientation and direction of most cortical cells remained roughly unchanged though their orientation and direction biases decreased. An increase in the animal's blood pressure, which returned the retinal perfusion pressure to a normal level, compensated for the decreased response induced by the elevation of IOP. CONCLUSIONS: The differential effects of a brief elevation of IOP on the response of simple and complex cells in the visual cortex are general and may originate from the retina through the lateral geniculate nucleus (LGN), where different effects of elevation of IOP are exerted on X- and Y-type retinal ganglion cells. The results may suggest differential behavior of neurons tin the parvo and magno pathways of the primate.

Animals↗
PubMed2005

Inducing form-deprivation myopia in fish.

PURPOSE: To induce form deprivation myopia in fish and investigate the role of the lens in the development of refractive error. METHODS: Tilapia (Oreochromis niloticus), approximately 4 months old and from 26 to 63 g, were divided into three groups. Translucent goggles were directly sutured over the right eye for 4 weeks to induce form-deprivation myopia; the left eye served as an untreated contralateral control. The refractive state was measured by retinoscopy. Ocular dimensions were determined from frozen sections and with ultrasound biomicroscopy, and a scanning laser system was used to determine the optical quality of excised lenses. RESULTS: After 4 weeks of form-deprivation treatment, all the deprived fish eyes showed development of significant amounts of myopia ranging from -3.75 to -26.25 D, with the average amounting to -10.27 +/- 1.14 D. Eye dimension measurements show that the vitreous and anterior chambers of the treated eye are significantly longer axially than those of the contralateral eyes. No significant change in optical quality was found between lenses of the myopic and nonmyopic eyes. The fish recovered completely from the myopia 5 days after the goggle was removed. CONCLUSIONS: Although lower vertebrates are capable of lifelong growth, their eyes are susceptible to form-deprivation myopia. Thus, the visual environment is an important factor controlling ocular development in lower vertebrates, as well as in higher ones, and eye development is not strictly genetically determined. This study also indicates that lens growth and optical development are largely independent from the refractive development of the whole eye.

Animals↗
PubMed2005

A general method to modify BACs to generate large recombinant DNA fragments.

Bacterial artificial chromosome (BAC) has the capacity to clone DNA fragments in excess of 300 kb. It also has the considerable advantages of stable propagation and ease of purification. These features make BAC suitable in genetic research, such as library construction, transgenic mice production, and gene targeting constructs. Homologous recombination in Escherichia coli, a process named recombineering, has made the modification of BACs easy and reliable. We report here a modified recombineering method that can efficiently mediate the fusion of large DNA fragments from two or more different BACs. With the introduction of kanamycin-resistant gene and proposed rare-cutting restriction endonuclease (RCRE) sites into two BACs, a 82.6-kb DNA fragment containing the inverted human alpha-globin genes (theta, alpha1, alpha2, and zeta) from BAC191K2 and the locus control region (LCR) of human beta-globin gene locus (from the BAC186D7) was reconstructed. This approach for combining different BAC DNA fragments should facilitate many kinds of genomic experiments.

Chromosomes, Artificial, Bacterial↗
PubMed2005

[Genetic structure and phylogeny status of Chaidamu goat population].

Genetic structure and character of Chaidamu goats were studied through simple random sampling. Genetic structure was analysed from five aspects, and phylogeny status was also investigated. The results indicated that: (1) the average phenotypic heterogeneity degree of coat color and morphological character were 0.3419 and 0.5207, respectively; (2) polymorphous blood albumen existed in 6 loci and the average loci heterozygosity was 0.2584; and (3) polymorphism existed in marked genes by DND-RAPD with diversity of 0.4085 approximately 0.5318. Phylogeny status was investigated through clustering by Ward's method on Chaidamu Goats and other domestic goats. All these indicated that Chaidamu Goats was a domestic goat with less intensively selected breed.

Albumins↗