Biomedical subjects

W Chen

Publications and source records attributed to W Chen.

At least 325 records · Page 18Linked to original sources

PubMed2000

Effects of pioglitazone on promoting energy storage, not expenditure, in brown adipose tissue of obese fa/fa Zucker rats: comparison to CL 316,243.

Recent advances in the treatment of non-insulin-dependent diabetes mellitus (NIDDM) include the use of thiazolidinediones (TZDs), agents that enhance insulin action, in part, through an activation of adipose tissue peroxisome proliferator-activated receptor gamma. Current evidence also indicates that these agents upregulate uncoupling protein 1 (UCP1) gene expression in brown adipocytes and increase interscapular brown adipose tissue (IBAT) mass in rodents, suggestive of a thermogenic component to their mechanism of action. In the present study, the TZD pioglitazone (PIO) and the beta3-adrenoceptor agonist CL 316,243 (CL), were used to determine whether the antidiabetic effects of PIO, like those of CL, may, in part, be mediated by an increase in either IBAT thermogenesis or whole-body energy expenditure. Treatment of obese, insulin resistant fa/fa Zucker rats with PIO for 10 days resulted in a 2- to 3-fold increase in IBAT mass, due largely to an increase in adipocyte size and number, and increased fatty acid biosynthesis. However, unlike the effects of CL, the PIO-induced IBAT changes were not associated with an increase in UCP1 expression or whole-body energy expenditure. In contrast to CL, PIO substantially increased body weight gains over the 10-day treatment period by increasing feeding efficiency. These data suggest that, unlike CL, the actions of PIO in the obese Zucker rat does not include increased energy expenditure, but rather strengthens its role as an adipogenic and lipogenic agent, which promotes energy storage.

Adipose Tissue, Brown↗

PubMed2000

Effects of parenteral infusion with medium-chain triglycerides and safflower oil emulsions on hepatic lipids, plasma amino acids and inflammatory mediators in septic rats.

This study was designed to investigate the effects of preinfusion with total parenteral nutrition (TPN) using medium-chain triglycerides (MCT) versus safflower oil (SO) emulsion as fat sources on hepatic lipids, plasma amino acid profiles, and inflammatory-related mediators in septic rats. Normal rats, with internal jugular catheters, were divided into two groups and received TPN. TPN provided 300kcal/kg/day with 40% of the non-protein energy provided as fat. All TPN solutions were isonitrogenous and identical in nutrient composition except for the fat emulsion, which was made of SO or a mixture of MCT and soybean oil (9:1) (MO). After receiving TPN for 6 days, each group of rats was further divided into control and sepsis subgroups. Sepsis was induced by cecal ligation and puncture, whereas control rats received sham operation. All rats were classified into four groups as follows: MCT control group (MOC, n= 8), MCT sepsis group (MOS, n= 8), safflower oil control group (SOC, n= 8), and safflower oil sepsis group (SOS, n= 11). The results of the study demonstrated that the MOS group had lower hepatic lipids than did the SOS group. Plasma leucine and isoleucine levels were significantly lower in the SOS than in the SOC group, but no differences in these two amino acids were observed between the MOC and MOS groups. Plasma arginine levels were significantly lower in septic groups than in those without sepsis despite whether MCT or safflower oil was infused. Plasma glutamine and alanine levels, however, did not differ between septic and non-septic groups either in the SO or MO groups. No differences in interleukin-1b, interleukin-6, tumor necrosis factor-alpha, and leukotriene B(4)concentrations in peritoneal lavage fluid were observed between the two septic groups. These results suggest that catabolic reaction is septic rats preinfused MCT is not as obvious as those preinfused safflower oil. Compared with safflower oil, TPN with MCT administration has better effects on reducing sepsis-induced liver fat deposition. Preinfusion with MCT before sepsis, however, had no effect on inflammatory-related cytokines or leukotriene in peritoneal lavage fluid. In addition, plasma arginine appears to be a more sensitive indicator than glutamine for septic insult.

Amino Acids↗

PubMed2000

Bacteriology and antimicrobial choice in hepatolithiasis.

BACKGROUND AND AIMS: Hepatolithiasis is prevalent in southeast Asia and presents a difficult management problem. Acute repeated episodes of cholangitis are frequently manifested in patients with hepatolithiasis. Without proper treatment, such infection can lead to liver abscess, secondary biliary cirrhosis, portal hypertension, and death from sepsis or hepatic failure. In addition to clearance of the stones and relief of bile stasis either by surgery or by interventional radiologic manipulation, effective antimicrobial therapy also plays a crucial role in the treatment of patients with hepatolithiasis. The aim of this study is to clarify the bacteriology in hepatolithiasis and to provide the information for an appropriate antimicrobial choice. METHODS: From July 1993 to June 1996, 150 patients with hepatolithiasis underwent surgical intervention. Bile specimens were routinely obtained by syringe aspiration from common bile duct. The syringe was immediately capped, and the bile was subsequently cultured for both aerobes and anaerobes. RESULTS: Bacteria were present in the bile of all patients. The bacteria most frequently found were gram-negative bacteria such as Klebsiella sp, Escherichia coli, and Pseudomonas sp, and the gram-positive Enterococcus sp. Bacteroides sp were the most frequently found anaerobes. CONCLUSIONS: This study demonstrated the close relationship between acute cholangitis in hepatolithiasis and enteric bacteria and also displayed the detailed antibiotic sensitivity results. Armed with this fruitful information, we believe the antibiotic treatment for acute cholangitis in hepatolithiasis should first aim at enteric bacteria and be adjusted later according to the results of bacteriologic cultures and clinical situation to achieve an effective microbial control.

Adult↗

PubMed2000

Reduced serum amino acid concentrations in infants with necrotizing enterocolitis.

OBJECTIVE: To determine whether premature infants who have necrotizing enterocolitis (NEC) have deficiencies in glutamine (GLN) and arginine (ARG), which are essential to intestinal integrity. STUDY DESIGN: A 4-month prospective cohort study of serum amino acid and urea levels in premature infants was done. Serum amino acid and urea levels were measured by high-pressure liquid chromatography and enzymatic methods, respectively, on samples obtained on days of life 3, 7, 14, and 21. RESULTS: Infants in the control (n = 32) and NEC groups (n = 13) were comparable for birth weight, gestational age, and Apgar scores. NEC began on mean day of life 14.5 (95% CI, day of life 11 to 18). Median values of GLN were 37% to 57% lower in the NEC group on days 7, 14, and 21 compared with those in the control group (P <.05). On days 7 and 14, median values of ARG, GLN, alanine, lysine, ornithine, and threonine were decreased 36% to 67% (P <.05) in the NEC group. Total nonessential amino and total essential amino acids were 35% to 50% lower in the NEC group on days 7 and 14 (P <.05). Infants in the NEC group had significant reductions in GLN and ARG 7 days before the onset of NEC. CONCLUSIONS: Infants who have NEC have selective amino acid deficiencies including reduced levels of GLN and ARG that may predispose to the illness.

Age Factors↗

PubMed2000

Effects of ragweed and Th-2 cytokines on the secretion of IL-8 in human airway epithelial cells.

Ragweed-induced asthma is a very common pulmonary disease. An important part of asthma is a large increase in inflammatory cells, including neutrophils and eosinophils, in ragweed-sensitilized subjects. In this study, we determined if ragweed treatment could induce the release of interleukin-8 (IL-8) by human airway epithelial cells. We found that ragweed induces a substantial increase of the secretion of IL-8 from A549 cells in a dose- and time-dependent manner. Th-2 cytokines, IL-4 and IL-13, partially inhibited the ragweed-induced secretion of IL-8. Our results suggest that airway epithelial cells may be one of the cell sources that provide IL-8 during ragweed-induced asthma. The results also indicate that IL-4 and IL-13 may exert inhibitory effects on IL-8 secretion by airway epithelium.

Allergens↗

PubMed2000

Examination of expert and novice teachers' constructivist-oriented teaching practices using a movement approach to elementary physical education.

The purpose of this study was to describe the characteristics of expert and novice teachers' constructivist-oriented teaching practices while using a movement approach to teach elementary physical education. Three expert and three novice teachers' constructivist-oriented teaching practices (18 lessons, 3 each) were evaluated using the Educational Games Observation Rubric (EGOR), a rubric specifically designed and validated for this study. Data sources included transcripts of two formal interviews with each teacher, transcripts of the 18 videotaped lessons, and coding from the EGOR. The expert teachers were more likely than the novice teachers to facilitate students' self-regulation and critical thinking about movement quality, to link new learning to students' prior knowledge and emerging relevance, and to guide students' social interaction. As with the expert teachers, the novice teachers encouraged students to engage in, elaborate on, and share ideas about movement variety tasks.

Adult↗

PubMed2000

Role of ribosome and translocon complex during folding of influenza hemagglutinin in the endoplasmic reticulum of living cells.

Protein folding in the living cell begins cotranslationally. To analyze how it is influenced by the ribosome and by the translocon complex during translocation into the endoplasmic reticulum, we expressed a mutant influenza hemagglutinin (a type I membrane glycoprotein) with a C-terminal extension. Analysis of the nascent chains by two-dimensional SDS-PAGE showed that ribosome attachment as such had little effect on ectodomain folding or trimer assembly. However, as long as the chains were ribosome bound and inside the translocon complex, formation of disulfides was partially suppressed, trimerization was inhibited, and the protein protected against aggregation.

Animals↗

PubMed2000

Age-related decline in Ras/ERK mitogen-activated protein kinase cascade is linked to a reduced association between Shc and EGF receptor.

Numerous studies have demonstrated that the proliferative capacity of cells declines with age. Using rat primary hepatocytes as a model system, we recently demonstrated that this age-related decline in the proliferative response to mitogenic stimulation is associated with decreased activities of both extracellular signal-regulated kinase (ERK) and p70 S6 kinase (p70(S6k)). To unravel the molecular basis for age-related defects in the ERK pathway, we have now characterized the upstream signaling events that occur after epidermal growth factor (EGF) stimulation in young and aged hepatocytes. As previously noted for ERK, the activities of both MEK (the kinase immediately upstream of ERK) and Ras following EGF stimulation were significantly lower in aged hepatocytes. An examination of the EGF receptor (EGFR) revealed a similar amount of EGFR in the two age groups. Likewise, EGFR and Shc, an adaptor protein that plays a crucial role in linking EGFR to Ras activation, underwent tyrosine phosphorylation to a similar degree in both young and aged hepatocytes. However, in aged cells Shc was unable to form stable complexes with EGFR after EGF stimulation. Our results suggest that a decrease in the association between Shc and EGFR in aged cells underlies the age-related declines in the ERK signaling cascade and in proliferative capacity.

Adaptor Proteins, Signal Transducing↗

PubMed2000

Anesthesiologist direction and patient outcomes.

BACKGROUND: Anesthesia services for surgical procedures may or may not be personally performed or medically directed by anesthesiologists. This study compares the outcomes of surgical patients whose anesthesia care was personally performed or medically directed by an anesthesiologist with the outcomes of patients whose anesthesia care was not personally performed or medically directed by an anesthesiologist. METHODS: Cases were defined as being either "directed" or "undirected," depending on the type of involvement of the anesthesiologist, as determined by Health Care Financing Administration billing records. Outcome rates were adjusted to account for severity of disease and other provider characteristics using logistic regression models that included 64 patient and 42 procedure covariates, plus an additional 11 hospital characteristics often associated with quality of care. Medicare claims records were analyzed for all elderly patients in Pennsylvania who underwent general surgical or orthopedic procedures between 1991-1994. The study involved 194,430 directed and 23,010 undirected patients among 245 hospitals. Outcomes studied included death rate within 30 days of admission, in-hospital complication rate, and the failure-to-rescue rate (defined as the rate of death after complications). RESULTS: Adjusted odds ratios for death and failure-to-rescue were greater when care was not directed by anesthesiologists (odds ratio for death = 1.08, P < 0.04; odds ratio for failure-to-rescue = 1.10, P < 0.01), whereas complications were not increased (odds ratio for complication = 1.00, P < 0.79). This corresponds to 2.5 excess deaths/1,000 patients and 6.9 excess failures-to-rescue (deaths) per 1,000 patients with complications. CONCLUSIONS: Both 30-day mortality rate and mortality rate after complications (failure-to-rescue) were lower when anesthesiologists directed anesthesia care. These results suggest that surgical outcomes in Medicare patients are associated with anesthesiologist direction, and may provide insight regarding potential approaches for improving surgical outcomes. (Key words: Anesthesiologists; anesthesia care team; quality of care; mortality; failure-to-rescue; complication; Medicare; general surgery; orthopedics.)

Aged↗

PubMed2000

Risk factors for presentation with bleeding in patients with Helicobacter pylori-related peptic ulcer diseases.

At present, there is no study that simultaneously addresses the apparent differences between bacterial and host factors in patients with bleeding and nonbleeding Helicobacter pylori-related ulcer diseases. Therefore, we designed this prospective study to evaluate whether there are identifiable differences between the two groups of patients whose H. pylori-related peptic ulcer diseases present with bleeding or dyspepsia. From July 1996 to November 1996, consecutive patients presenting with upper gastrointestinal bleeding or dyspepsia were enrolled if H. pylori-related ulcer diseases were confirmed. Fifteen clinical, endoscopic, histologic, and serologic factors were tested for association with ulcer bleeding by a logistic regression analysis. In the study period, bleeding occurred in 39 out of 119 patients with H. pylori-related peptic ulcer diseases. Multivariate analysis showed that ingestion of nonsteroidal antiinflammatory drugs (NSAIDs; p = 0.0156; odds ratio = 5:4), ulcer size > or = 1 cm (p = 0.0033; odds ratio = 4:2), and low bacterial density (p = 0.0030; odds ratio = 4:1) were independent factors associated with the risk of bleeding. There were no associations between ulcer bleeding and age, sex, smoking, alcohol consumption, the histologic grade of gastritis, location and number of ulcers, and the cytotoxin-associated gene (CagA) status of H. pylori strain. Therefore, we concluded that H. pylori-related ulcer patients who use NSAIDs or have large ulcers are more likely to present with upper gastrointestinal bleeding; that the CagA-bearing strains are not associated with the development of bleeding complication in patients with peptic ulcer diseases; and that the exact reason concerning the association between low bacterial density and ulcer bleeding merits further investigation.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2000

Estimating fetal weight in the management of macrosomia.

The purpose of this review is to examine the evidence that, including estimates of fetal macrosomia in patient care, will decrease adverse perinatal outcomes. A literature search for the years 1980 to 1999 was used. Shoulder dystocia and brachial plexus injuries occur more often in macrosomic than in non-macrosomic neonates. However, 26 to 58 percent of shoulder dystocias and 24 to 44 percent of brachial plexus injuries occur to babies weighing less than 4000 gm. Persistence of impairment is extremely rare. Neither historical nor clinical factors have strong positive predictive values for macrosomia. From 15 to 81 percent of the babies predicted to be macrosomic are confirmed by birth weight. Of babies determined to be macrosomic at birth, only 50 to 100 percent were successfully predicted. Shoulder dystocia and brachial plexus injuries are unpredictable events. Available evidence suggests that planned interventions based on estimates of fetal weight do not reduce the incidence of shoulder dystocia and do not decrease adverse outcomes attributable to fetal macrosomia.

Birth Injuries↗

PubMed2000

Intelligent database generated occupational questionnaire system.

Obtaining an adequate occupational history requires special expertise to "ask the right questions" that are relevant to a particular patient's specific health conditions and potential exposures. This article describes a way to systematically accomplish this by means of a computer system that can overcome limited availability of necessary clinical occupational health expertise. The Intelligent Questionnaire system is a computer-based system for generating case-specific questionnaires about the influence of work on respiratory disease. Intelligent Questionnaire includes three databases: Questions, Responses, and Calls (clues to identify questions). The Questionnaire also arranges questions in a logical manner and provides a customized data entry screen for each subject. This approach provides primary practitioners with expertise on a case-by-case basis. It also facilitates occupational health surveillance because it allows acquiring detailed case-specific information in a systematic fashion. A computer-based system can facilitate obtaining occupational histories with high specificity and consistency without depending on general availability of a human occupational health clinical expertise.

Artificial Intelligence↗

PubMed2000

Genetic erosion in northern marginal population of the common wild rice Oryza rufipogon Griff. and its conservation, revealed by the change of population genetic structure.

In order to monitor genetic erosion within the northern marginal population of common wild rice Oryza rufipogon Griff. from Dongxiang, Jiangxi Province, China, allozyme diversity encoded by 22 loci was analyzed electrophoretically from all the existing subpopulations in 1980, 1985 and 1994. The sample collected from the nine large subpopulations in 1980 showed the highest levels of genetic diversity (A = 1.27, P = 18.20%, Ho = 0.042 and He = 0.049) and a slight deviation from Hardy-Weinberg expectation (F = 0.143), the sample from five moderate ones in 1985 displayed medium levels of genetic diversity (A = 1.14, P = 13.60%, Ho = 0.008 and He = 0.049) and a great deviation from Hardy-Weinberg expectation (F = 0.837), and the sample from two small ones in 1994 demonstrated the lowest levels of genetic diversity (A = 1.09, P = 9.10%, Ho = 0.000 and He = 0.043) and the largest deviation from Hardy-Weinberg expectation (F = 1.000). The results not only documented the genetic erosion stemmed from the extinction of the subpopulations, but also revealed the drastic change of the population genetic structure due to the reduction of the population. Finally, some conservation strategies for the population are proposed.

DNA, Plant↗

PubMed2000

A localization algorithm and error analysis for stereo x-ray image guidance.

Stereo x-ray radiography attracts increasing attention in major clinical applications. The purpose of this paper is to analyze the 3D localization error for breast biopsy procedures and provide guidelines for improving its accuracy. Our prototype is a CCD based digital stereo x-ray imaging system. The mathematical model consists of two x-ray sources and one stationary detector plane. A closed form least-squares solution is derived for 3D localization of feature points, particularly a biopsy needle tip, from a pair of 2D digital radiographs. Based on the least-squares formula and its first order approximation, the 3D localization error is analyzed in terms of object location, measurement error, separation between the two x-ray sources, and distance from the source to the detector. The stereo imaging and error estimation formulas are numerically simulated and experimentally validated. The data are in agreement with theoretical prediction. These results can be used for the purpose of system design and protocol optimization.

Algorithms↗

PubMed2000

Correction of the DNA sequence of the regB gene of Rhodobacter capsulatus with implications for the membrane topology of the sensor kinase regB.

We corrected the previously published sequence for the regB gene, which encodes a histidine sensor kinase in Rhodobacter capsulatus. The deduced RegB amino acid sequence has an additional putative transmembrane domain at the N terminus. Analysis of RegB-PhoA and RegB-LacZ fusion proteins supports a topology model for RegB with six membrane-spanning domains.

Alkaline Phosphatase↗

PubMed2000

Identification of a methylation imprint mark within the mouse Gnas locus.

The imprinted mouse gene Gnas produces the G protein alpha-subunit G(S)alpha and several other gene products by using alternative promoters and first exons. G(S)alpha is maternally expressed in some tissues and biallelically expressed in most other tissues, while the gene products NESP55 and XLalphas are maternally and paternally expressed, respectively. We investigated the mechanisms of Gnas imprinting. The G(S)alpha promoter and first exon are not methylated on either allele. A further upstream region (approximately from positions -3400 to -939 relative to the G(S)alpha translational start site) is methylated only on the maternal allele in all adult somatic tissues and in early postimplantation development. Within this region lies a fourth promoter and first exon (exon 1A) that generates paternal-specific mRNAs of unknown function. Exon 1A and G(S)alpha mRNAs have similar expression patterns, making competition between their promoters unlikely. Differential methylation in this region is established during gametogenesis, being present in oocytes and absent in spermatozoa, and is maintained in preimplantation E3. 5d blastocysts. Therefore, this region is a methylation imprint mark. In contrast, differential methylation of the NESP55 and XLalphas promoter regions (Nesp and Gnasxl) is not established during gametogenesis. The methylation imprint mark that we identified may be important for the tissue-specific imprinting of G(S)alpha.

Animals↗

PubMed2000

Magnetic resonance studies of brain function and neurochemistry.

In the short time since its introduction, magnetic resonance imaging (MRI) has rapidly evolved to become an indispensable tool for clinical diagnosis and biomedical research. Recently, this methodology has been successfully used for the acquisition of functional, physiological, and biochemical information in intact systems, particularly in the human body. The ability to map areas of altered neuronal activity in the brain, often referred to as functional magnetic resonance imaging (fMRI), is probably one of the most significant recent achievements that rely on this methodology. This development has permitted the examination of functional specialization in human and animal brains with unprecedented spatial resolution, as demonstrated by mapping at the level of orientation and ocular dominance columns in the visual cortex. These functional imaging studies are complemented by the ability to study neurochemistry using magnetic resonance spectroscopy, allowing the determination of metabolic processes that support neurotransmission and neurotransmission rates themselves.

Animals↗

PubMed2000

Activin A-induced HepG2 liver cell apoptosis: involvement of activin receptors and smad proteins.

A balance between cell proliferation and apoptosis is important for regulating normal liver function. Proteins of the transforming growth factor-beta superfamily are known to be important mediators of apoptosis in the liver. In this study we demonstrate that activin A potently induces apoptotic cell death in a hepatoma cell line, HepG2 cells. To determine the roles of activin receptors and downstream signaling proteins in activin A-induced apoptosis in these cells, the activin signaling pathway was analyzed using the transcription of an activin-responsive reporter gene, p3TP-Lux, as an assay. Although individual activin receptors had little effect on transcriptional activity, coexpression of an activin type I receptor and a type II receptor significantly increased both basal and activin-induced transcriptional activation, with the combination ofreceptors IB and IIB being the most potent. Similarly, expression of individual Smad proteins had only a modest effect on reporter gene activity, but the combination of Smad2 and Smad4 strongly stimulated transcription. Activin signaling induced a rapid relocation of Smad2 to the nucleus, as determined using a green fluorescence protein-Smad2 fusion protein. In contrast, green fluorescence protein-Smad4 remained localized to the cytoplasm unless it was coexpressed with Smad2. In agreement with the transcriptional response assays, overexpression or suppression of activin signaling components in HepG2 cells altered apoptosis. Overexpression of receptors IB and IIB or Smad proteins 2 and 4 stimulated apoptosis, whereas dominant negative mutant forms of the activin type IIB receptor or Smad2 blocked activin-stimulated apoptosis. These studies suggest that signaling from the cell surface to the nucleus through Smad proteins is a required component of the activin A-induced cell death process in liver cells.

Activin Receptors↗