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Biomedical subjects

Jack Chen

Publications and source records attributed to Jack Chen.

At least 19 recordsLinked to original sources
PubMed2007

The continuum model of obligatory exercise: a preliminary investigation.

OBJECTIVE: The aim of this study was to carry out a preliminary study of the proposed Continuum Model of Obligatory Exercise, which states that obligatory exercise lies on a continuum--a continuum that is characterized not only by differences in severity, but by qualitative differences in the way the syndrome manifests, as the behaviour changes from mildly obsessive attitudes to exercise, to extremely disordered attitudes to exercise, which are accompanied by an eating disorder. METHOD: Structural equation modelling (SEM) was used to investigate the Continuum Model of Obligatory Exercise utilizing data from a longitudinal study of female triathletes. RESULTS: The structural model specifying the hypothesized causal pathways confirmed many of the postulates of the Continuum Model of Obligatory Exercise, including the role of weight and shape preoccupation in predicting food restriction, eating disorder behaviour, and increased obligatory exercise behaviour, as well as the role of obsessive-compulsiveness and increased physical activity in predicting eating disorder behaviour in exercisers. CONCLUSION: The structural model investigated is reasonable and can serve as a starting point for a theory-based empirical exploration of the notion that obligatory exercise behaviour lies on a continuum.

Adult↗
PubMed2006

Distant touch hydrodynamic imaging with an artificial lateral line.

Nearly all underwater vehicles and surface ships today use sonar and vision for imaging and navigation. However, sonar and vision systems face various limitations, e.g., sonar blind zones, dark or murky environments, etc. Evolved over millions of years, fish use the lateral line, a distributed linear array of flow sensing organs, for underwater hydrodynamic imaging and information extraction. We demonstrate here a proof-of-concept artificial lateral line system. It enables a distant touch hydrodynamic imaging capability to critically augment sonar and vision systems. We show that the artificial lateral line can successfully perform dipole source localization and hydrodynamic wake detection. The development of the artificial lateral line is aimed at fundamentally enhancing human ability to detect, navigate, and survive in the underwater environment.

Animals↗
PubMed2006

An exploration of 3'-end processing signals and their tissue distribution in Oryza sativa.

The 3' untranslated regions deeply affect many properties of eukaryotic mRNA. In plants, the polyadenine control signals contained in these regions seem to be more variable than of mammals. Three cDNA libraries derived from the leaf, endosperm and stem tissues of rice were sequenced from the 3'-end. Of the 9911 transcripts analyzed, 5723 unique transcripts were identified from the leaf sequences, 2934 from the endosperm and 1254 from the stem. The information entropy and two statistical methods were used to compile a list of rice poly(A) control signals. Based on their distribution, these signals can be roughly grouped into far-upstream element (FUE), near-upstream element (NUE), T-rich region (TRE) and downstream element (DE). The distribution of rice conserved regions is similar to the previous model from Arabidopsis and yeast, with a few differences in word constructions. Interestingly, we also found the word distributions were diverse in the cleavage site of downstream sequences of different rice tissues. The signal bias in downstream sequences may lead mRNA to be differently cleaved in different rice tissues.

3' Untranslated Regions↗
PubMed2006

Hepatitis C in Australia: impact of a mass media campaign.

BACKGROUND: Hepatitis C affects over 200,000 Australians. This study evaluated the impact of a public education campaign about this disease in New South Wales (NSW), Australia. DESIGN: Cohort and independent cross-sectional telephone surveys before and after the campaign. SETTING/PARTICIPANTS: Random population samples of adults in NSW. INTERVENTION: Television, radio and newsprint advertisements, posters and public display boards, public awareness events and media releases, and dissemination of information to healthcare professionals in April 2000. Data were analyzed in 2000 and 2005. MAIN OUTCOME MEASURES: Campaign recall, and knowledge and attitudes concerning hepatitis C. RESULTS: Recall of information about hepatitis C increased between baseline and follow-up, from 11.1% to 45.5% in the independent samples and 11.8% to 65.3% in the cohort. The proportion of people who knew that there was a low risk of disease transmission by kissing, sharing food utensils, or breastfeeding also increased significantly. In the cohort sample, a higher number of correct knowledge responses was associated with reporting exposure to information about hepatitis C after the campaign, postsecondary education, and a greater level of knowledge at baseline. Most people reported supportive attitudes toward people with hepatitis C and to prevention programs addressing this disease, and there was little apparent improvement in these. CONCLUSIONS: This campaign successfully increased public exposure to information about hepatitis C and improved knowledge about the means of transmission of this disease. There is room for further improvements in community understanding about hepatitis C. Mass media campaigns have a valuable role to play in this endeavor.

Adolescent↗
PubMed2006

Efficacy of linezolid versus vancomycin in the treatment of methicillin-resistant Staphylococcus aureus discitis: a controlled animal model.

STUDY DESIGN: A rabbit model was used to assess the efficacy of linezolid and vancomycin for the treatment of discitis due to methicillin-resistant Staphylococcus aureus (MRSA). Nontreated controls were used for comparison. OBJECTIVE: The purpose of this study was to determine if there was a therapeutic difference between using linezolid and vancomycin in the treatment of MRSA discitis. SUMMARY OF BACKGROUND DATA: Vancomycin is currently the gold standard treatment for medical management of MRSA discitis. Linezolid is a relatively new drug that has been approved for treatment of MRSA infections, but currently there is no research demonstrating its efficacy at treating infections of the disc space. METHODS: Twenty-four rabbits were inoculated with MRSA at two adjacent lumbar disc spaces via an anterior retroperitoneal approach. Six rabbits were to receive only pain medication and to serve as controls. Ten rabbits were assigned to a 5-day course of intravenous vancomycin, and 8 were assigned to a 5-day course of intravenous linezolid. Disc spaces were sent for quantitative culture after the 5-day treatment course. RESULTS: The mean culture growth for the disc spaces was not statistically different between the linezolid treated group and the nontreated controls. While vancomycin treatment did lead to lower bacterial loads when compared with controls, the reduction was not statistically significant. When bacterial counts for the vancomycin group and linezolid group were compared, vancomycin treatment resulted in less bacterial growth. This difference was statistically significant. CONCLUSIONS: Linezolid is a clinically attractive alternative to vancomycin due to its mild side effect profile and oral bioavailability. However, in this MRSA discitis model with a short treatment course, vancomycin was superior to linezolid.

Acetamides↗
PubMed2006

Modeling ozone and aerosol formation and transport in the pacific northwest with the community Multi-Scale Air Quality (CMAQ) modeling system.

The Community Multi-Scale Air Quality (CMAQ) modeling system was used to investigate ozone and aerosol concentrations in the Pacific Northwest (PNW) during hot summertime conditions during July 1-15, 1996. Two emission inventories (El) were developed: emissions for the first El were based upon the National Emission Trend 1996 (NET96) database and the BEIS2 biogenic emission model, and emissions for the second El were developed through a "bottom up" approach that included biogenic emissions obtained from the GLOBEIS model. The two simulations showed that elevated PM2.5 concentrations occurred near and downwind of the Interstate-5 corridor along the foothills of the Cascade Mountains and in forested areas of central Idaho. The relative contributions of organic and inorganic aerosols varied by region, but generally organic aerosols constituted the largest fraction of PM2.5. In wilderness areas near the 1-5 corridor, organic carbon from anthropogenic sources contributed approximately 50% of the total organic carbon with the remainder from biogenic precursors, while in wilderness areas in Idaho, biogenic organic carbon accounted for 80% of the total organic aerosol. Regional analysis of the secondary organic aerosol formation in the Columbia River Gorge, Central Idaho, and the Olympics/Puget Sound showed that the production rate of secondary organic carbon depends on local terpene concentrations and the local oxidizing capacity of the atmosphere, which was strongly influenced by anthropogenic emissions. Comparison with observations from 12 IMPROVE sites and 21 ozone monitoring sites showed that results from the two El simulations generally bracketed the average observed PM parameters and that errors calculated for the model results were within acceptable bounds. Analysis across all statistical parameters indicated that the NW-AIRQUEST El solution performed better at predicting PM2.5, PM1, and beta(ext) even though organic carbon PM was over-predicted, and the NET96 El solution performed better with regard to the inorganic aerosols. For the NW-AIRQUEST El solution, the normalized bias was 30% and the normalized absolute error was 49% for PM2.5 mass. The NW-AIRQUEST solution slightly overestimated peak hourly ozone downwind of urban areas, while the NET96 solution slightly underestimated peak values, and both solutions over-predicted average 03 concentrations across the domain by approximately 6 ppb.

Aerosols↗
PubMed2006

Prevalence of inadequate glycemic control among patients with type 2 diabetes in the United Kingdom general practice research database: A series of retrospective analyses of data from 1998 through 2002.

BACKGROUND: Since the mid-1990s, the development of new oral antidiabetic agents (OAs) and treatment guidelines have created an opportunity to improve glycemic control in patients with type 2 diabetes. OBJECTIVES: This study aimed to assess the prevalence of good and inadequate glycemic control across a 5-year period among patients with diabetes in the United Kingdom. It also investigated the factors associated with achieving glycemic targets. METHODS: This was a retrospective, cross-sectional analysis of data from the General Practice Research Database. Three limits were used to assess glycosylated hemoglobin (HbA1c): 6.5%, 7.0%, or 7.5%. Values above the cutoffs indicated inadequate control of HbA1c; those at or below the cutoffs indicated good control. The study evaluated clinical and pharmacy data from the years 1998 to 2002 for patients with type 2 diabetes, > or =2 years of follow-up, and > or =2 HbA1c measurements during the first year. Five independent cross-sectional analyses were conducted, grouping data by year. Statistical significance was determined by Student t and chi2 tests. RESULTS: Data were analyzed for 10,663 patients aged 17 to 98 years. The number of total eligible type 2 diabetes patients increased over the course of the study period: 5674 patients in 1998, 6553 in 1999, 7314 in 2000, 7323 in 2001, and 6192 in 2002. Overall, the study population had a mean (SD) age of 66 (11.0) years, was 53% male (3033/5674), and had a body mass index of 29 kg/m(2). Seventy-six percent of patients had HbA1c >7.0% and 37% were taking > or =2 oral agents. In 1998 and 2002, 79% (4482/5674) and 76% (4732/6192) of patients, respectively, had inadequate glycemic control, defined as HbA1c >7.0%. When defined as HbA1c >7.5%, 69% (3923/5674) and 62% (3814/6192) of patients, respectively, had inadequate control. Finally, when defined as HbA1c >6.5%, 88% (5011/5674) of patients in both 1998 and 2002 had inadequate control. Compared with patients with good disease control (HbA1c < or =7.0%), patients with inadequate control were approximately 2 years younger (P < 0.001) and had been prescribed more OAs: 41% received > or =2 OAs in 1998 and 52% in 2002, compared with 23% and 34% (both, P = 0.001), respectively, of patients with good glycemic control (P < 0.02). Sex, number of diabetes complications, and number of comorbidities did not differ between groups (P = NS). CONCLUSIONS: Despite the introduction of new OAs and treatment guidelines, the prevalence of inadequate glycemic control remains high (>60%) in patients with type 2 diabetes in the United Kingdom. Regardless of the HbA1c cutoff, patients with inadequate control were younger and received prescriptions for more OAs than patients with good control.

Administration, Oral↗
PubMed2006

Findings of the first consensus conference on medical emergency teams.

BACKGROUND: Studies have established that physiologic instability and services mismatching precede adverse events in hospitalized patients. In response to these considerations, the concept of a Rapid Response System (RRS) has emerged. The responding team is commonly known as a medical emergency team (MET), rapid response team (RRT), or critical care outreach (CCO). Studies show that an RRS may improve outcome, but questions remain regarding the benefit, design elements, and advisability of implementing a MET system. METHODS: In June 2005 an International Conference on Medical Emergency Teams (ICMET) included experts in patient safety, hospital medicine, critical care medicine, and METs. Seven of 25 had no experience with an RRS, and the remainder had experience with one of the three major forms of RRS. After preconference telephone and e-mail conversations by the panelists in which questions to be discussed were characterized, literature reviewed, and preliminary answers created, the panelists convened for 2 days to create a consensus document. Four major content areas were addressed: What is a MET response? Is there a MET syndrome? What are barriers to METS? How should outcome be measured? Panelists considered whether all hospitals should implement an RRS. RESULTS: Patients needing an RRS intervention are suddenly critically ill and have a mismatch of resources to needs. Hospitals should implement an RRS, which consists of four elements: an afferent, "crisis detection" and "response triggering" mechanism; an efferent, predetermined rapid response team; a governance/administrative structure to supply and organize resources; and a mechanism to evaluate crisis antecedents and promote hospital process improvement to prevent future events.

Benchmarking↗
PubMed2005

Voluntary electronic reporting of medical errors and adverse events. An analysis of 92,547 reports from 26 acute care hospitals.

OBJECTIVE: To describe the rate and types of events reported in acute care hospitals using an electronic error reporting system (e-ERS). DESIGN: Descriptive study of reported events using the same e-ERS between January 1, 2001 and September 30, 2003. SETTING: Twenty-six acute care nonfederal hospitals throughout the U.S. that voluntarily implemented a web-based e-ERS for at least 3 months. PARTICIPANTS: Hospital employees and staff. INTERVENTION: A secure, standardized, commercially available web-based reporting system. RESULTS: Median duration of e-ERS use was 21 months (range 3 to 33 months). A total of 92,547 reports were obtained during 2,547,154 patient-days. Reporting rates varied widely across hospitals (9 to 95 reports per 1,000 inpatient-days; median=35). Registered nurses provided nearly half of the reports; physicians contributed less than 2%. Thirty-four percent of reports were classified as nonmedication-related clinical events, 33% as medication/infusion related, 13% were falls, 13% as administrative, and 6% other. Among 80% of reports that identified level of impact, 53% were events that reached a patient ("patient events"), 13% were near misses that did not reach the patient, and 14% were hospital environment problems. Among 49,341 patient events, 67% caused no harm, 32% temporary harm, 0.8% life threatening or permanent harm, and 0.4% contributed to patient deaths. CONCLUSIONS: An e-ERS provides an accessible venue for reporting medical errors, adverse events, and near misses. The wide variation in reporting rates among hospitals, and very low reporting rates by physicians, requires investigation.

Adverse Drug Reaction Reporting Systems↗
PubMed2005

Health behaviour and lifestyle of Pacific youth surveys: a resource for capacity building.

The changing global socio-economic environment over the last two decades has had significant ramifications for the health and development of youth in lower- and middle-income countries. In the Pacific region, young people are exposed to similar causes of ill-health as their peers in developed countries. This paper describes the development, implementation and major findings of the Health Behaviour and Lifestyle of Pacific Youth (HBLPY) surveys, a regional initiative to obtain representative data about health-related behaviour and needs of adolescents in Vanuatu, Tonga and the Federated States of Micronesia. The Pacific HBLPY is modelled on the WHO Europe Health Behaviour in School-aged Children (HBSC) surveys. The surveys, undertaken in 2000-2001, were built upon strong local partnerships and were undertaken with youth participation to ensure survey ownership. A regional technical group was formed to provide training and support to strengthen health survey capacity of youth and their agencies. The findings showed that tobacco was most commonly used substance, with 29.7% of 15-year-old boys and 15.7% of girls smoking weekly. Over half of the students did not engage in physical activity for at least 2 h per week; these rates are substantially lower than those usually found in Europe. Dietary habits among this group are also of concern, reflecting international trends away from highly nutritious traditional diets. The HBLPY surveys have shown that it is possible to collect population-based data in lower- and middle-income countries so that appropriate youth health programmes and policies can be developed. Implementation of an ongoing surveillance system similar to the HBLPY model in these countries warrants further investigation. Such initiatives should be supported at the regional and global level.

Adolescent↗
PubMed2005

Impact of a mass media campaign upon calls to the New South Wales Hep C helpline.

ISSUE ADDRESSED: This study evaluated the impact of a mass media campaign upon calls to the New South Wales Hep C Helpline. METHODS: A time-series design was used to record the number and characteristics of calls to the helpline before, during and after the campaign. RESULTS: The incidence rate ratio of calls during the month of the campaign was 3.12 (95% CI 2.45-3.97) compared with the months before the campaign, and in this month more callers were < or =30 years or > or =60 years of age or non-English speaking while fewer were professionals or people directly affected by hepatitis C. Callers during the campaign were more likely to have heard about the helpline through the media and to want information about disease transmission, and less likely to want to discuss topics such as support and legal issues. CONCLUSIONS: The calls received by the Hep C Helpline indicate that the campaign was a useful way to generate public interest about hepatitis C. The findings indicate that telephone helplines are an information dissemination strategy that can be coupled effectively with mass media campaigns about this issue.

Adult↗
PubMed2005

Cost-effectiveness analysis of ondansetron and prochlorperazine for the prevention of postoperative nausea and vomiting.

OBJECTIVE: To compare the cost-effectiveness of 2 antiemetic agents, ondansetron and prochlorperazine, for the prevention of postoperative nausea and vomiting (PONV) in patients undergoing total hip replacement or total knee replacement procedures. METHODS: The cost-effectiveness analysis model was applied to data derived from a previous clinical study conducted in 1995 and 1996. This study involved 78 adult patients (62.8% female and 37.2% male) undergoing total hip replacement or total knee replacement procedures. Patients were enrolled in a randomized, double-blind manner to receive either ondansetron 4 mg intrvenously (n=37) or prochlorperazine 10 mg intramuscularly (n=41) immediately upon completion of surgery and were monitored for occurrences of PONV during the subsequent 48 hours. In our analysis, we measured the cost-effectiveness ratio (C/E ratio), defined as the cost per successfully treated patient, for each antiemetic agent using the clinical data obtained from the previous study. RESULTS: The incidence of PONV and use of rescue antiemetics was significantly greater in the ondansetron group compared with the prochlorperazine group. The mean total costs of PONV management per patient in the prochlorperazine and ondansetron groups were dollar 13.99 and dollar 51.98, respectively (based on 2004 average wholesale prices [AWP]). The cost of successfully treating one patient with prochlorperazine and ondansetron was dollar 31.87 and dollar 275.01, respectively. One-way sensitivity analysis was performed adjusting the percent efficacy rate of each antiemetic and the drug cost of ondansetron (up to a 50% reduction in AWP). Prochlorperazine remained the dominant strategy across each scenario. CONCLUSION: The results indicate that prochlorperazine is a more cost-effective antiemetic compared with ondansetron for the prevention of PONV in a mixed gender, adult inpatient population undergoing total joint arthroplasty.

Antiemetics↗
PubMed2003

A clinical model for Health Services Research-the Medical Emergency Team.

Health Services Research (HSR) is a relatively recent discipline which describes how health care delivery occurs and the evaluation of that care. The implementation of a Medical Emergency Team (MET) is an example of a health service intervention. The aim of the MET is to extend the expertise of Intensive Care across the hospital to all at-risk patients. The MET criteria for calling are based on simple abnormalities in vital signs with an extra "worried" category to empower junior medical and nursing staff to call for help. The concept is based on early intervention and resuscitation of the seriously ill, hopefully leading to improved outcomes from intensive care and perhaps even avoiding admission to an intensive care unit. The problems of implementing major health service change and evaluating the effectiveness of that change presents a different challenge to evaluating a new drug or procedure and is approached within different research frameworks.

Emergency Treatment↗
PubMed2002

Conjoint analysis of a new Chemotherapy: willingness to pay and preference for the features of raltitrexed versus standard therapy in advanced Colorectal Cancer.

OBJECTIVE: To estimate the willingness to pay for a new chemotherapy, raltitrexed (Tomudex trade mark ) over conventional therapy with fluorouracil plus leucovorin (FU-LV) from the perspective of patients with advanced colorectal cancer. The study was part of the product's reimbursement application in Australia. DESIGN AND METHODS: The key differences relevant to patients between the two therapies, frequency of administration and severity of mouth ulceration, were used to develop a self-administered questionnaire. A relatively new technique to healthcare, that of conjoint analysis (CA), was used to estimate willingness to pay and strength of preference. A discrete choice CA was used. Analysis was via a logit model with adjustment for the cluster effect (or intra-patient correlation). STUDY PARTICIPANTS: Oncology nurses served as proxies for patients with advanced colorectal cancer. RESULTS: The participation rate was 87% (62/71) with questionnaires from 56 respondents eligible for analysis. The CA method generated a mean incremental willingness to pay of 745 Australian dollars (dollar A; dollars US 507) per cycle of chemotherapy, comprising dollars A 550 (dollars US 374) and dollars A 195 (dollars US 133) for the toxicity and administration improvements, respectively (1998 values). Both features were related to preference with independent odds of 6.87 and 1.98, respectively, however only the toxicity attribute was a significantly related to preference. Subscription to private health insurance was the only significant demographic predictor identified, however, the homogeneous income structure of the respondents seems likely to have masked any significant income effect. CONCLUSIONS: This study highlights the advantages of using CA in healthcare, where new therapies or treatments are often composed of a number of attributes. The CA allows both strength of preference and willingness to pay for individual treatment attributes to be estimated and can be used to assign statistical significance to these parameters.

Adult↗
PubMed2002

Human breast cancer MCF-7 cell line contains inherently drug-resistant subclones with distinct genotypic and phenotypic features.

The resistance of cancer cells to multiple chemotherapeutic agents poses a major problem in the successful treatment of breast cancer. Whether drug resistance is due to changes induced in the drug-exposed tumor cells or represents the selective growth of one or more drug-resistant clones present in the initial tumor remains controversial. Here we provide evidence that the development of multidrug resistance in a human breast cancer cell line (MCF-7) is a result of propagation of an inherently resistant subclone. The drug-resistant MCF-7 (MCF-7/DOX) cells exhibited several phenotypic and genotypic features that were notably distinct from those observed in the parental drug-sensitive (MCF-7/WT) cells. The most striking change was the presence of a full-length functional caspase-3 in MCF-7/DOX cells that was missing in the parental MCF-7/WT cells due to a deletion mutation in the caspase-3 gene. A drug-resistant MCF-7 cell subline (MCF-7/WT/DOX) was established by exposing the MCF-7/WT cells directly to a high dose of doxorubicin and used for determining the phenotypic and genotypic alterations associated with drug resistance. The MCF-7/WT/DOX cells exhibited alterations identical to those of the MCF-7/DOX cells but which were strikingly distinct from the parental MCF-7/WT cell line. These results suggest that drug resistance is an inherent property of some cancer cells that are present in the initial tumor burden and exhibit distinct phenotypic/genotypic alterations.

Breast Neoplasms↗
PubMed2002

A comparison of techniques for eliciting patient preferences in patients with benign prostatic hyperplasia.

PURPOSE: We compared the Health Utility Index (HUI), EuroQol (EQ-5D) and time trade-off methods to identify the most suitable technique for collecting preference data in a clinical trial of patients with benign prostatic hyperplasia (BPH). MATERIALS AND METHODS: A total of 29 men with symptomatic BPH were interviewed by a single trained interviewer who collected demographic data and administered EQ-5D and time trade-off questionnaires. Participants self-administered the HUI and a symptom severity index, the International Prostate Symptom Score (I-PSS) questionnaire. Utility values for current patient health states obtained from the HUI, EQ-5D and time trade-off questionnaires were compared and their relationship with I-PSS data was examined using Spearman's correlation coefficients. Administration time and patient assessments of the relevance of the questions were also compared for the 3 methods. RESULTS: Although mean utility values for HUI, EQ-5D and 1-year time trade-off were similar, only utility values elicited using time trade-off with a 1-year time frame significantly correlated with symptom scores. The 1 and 10-year time trade-off derived values were reasonable predictors of the I-PSS with multiple correlation coefficient values of 0.379 and 0.265, respectively. All participants indicated that the HUI and EQ-5D were appropriate for assessing BPH, while approximately 10% considered time trade-off questions irrelevant. Average completion time for the HUI, time trade-off and EQ-5D questionnaires was 31, 25 and 10 minutes, respectively. CONCLUSIONS: Because only time trade-off resulted in utility values that significantly correlated with symptom scores, we recommend its use for estimating utility in clinical trials of BPH.

Adult↗