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Biomedical subjects

James D Lewis

Publications and source records attributed to James D Lewis.

At least 19 recordsLinked to original sources
PubMed2003

Age at flowering differentially affects vegetative and reproductive responses of a determinate annual plant to elevated carbon dioxide.

Plant population and community dynamics may be altered by increasing atmospheric CO(2) concentrations [[CO(2)]] through intraspecific variation in the responses of vegetative and reproductive growth. Although these responses may be regulated by age at flowering, little is known about the direct effects of age at flowering on growth responses to elevated [CO(2)]. In this study, we examined the interactive effects of elevated [CO(2)] and age at flowering on absolute and relative allocation to vegetative and reproductive growth in the determinate, short-day species Xanthium strumarium L. (common cocklebur). Six cohorts were planted at 5-day intervals in chambers maintained at either 365 or 730 micro mol mol(-1) CO(2), with an 18-h photoperiod and a non-limiting nutrient supply. All plants were simultaneously induced to flower by switching the photoperiod to 12 h for 2 days, then switching back to an 18-h photoperiod for the remainder of the experiment. All plants were harvested 15 days after the onset of flowering. Total plant biomass increased 11-41% with increasing [CO(2)] and 45% from the youngest to the oldest cohort. Vegetative growth responses to elevated [CO(2)] significantly increased with increasing age at flowering, associated with increasing sink relative to source capacity. In contrast, total fruit mass decreased 32% from the youngest to the oldest cohort and was not significantly affected by CO(2) supply. Relative biomass allocation to fruit decreased 47% from the youngest to the oldest cohort, reflecting decreased numbers of fruit, and 6-28% with increasing [CO(2)], reflecting decreased mean mass per mature fruit. Our findings suggest that elevated [CO(2)] may increase vegetative growth in Xanthium without increasing reproductive biomass, and that age at flowering may influence these responses through effects on source:sink balance. Further, changes in the allometric relationship between vegetative and reproductive growth associated with growth in elevated [CO(2)] suggest that long-term population and community-level responses to elevated [CO(2)] may differ substantially from predictions based on vegetative responses.

Carbon Dioxide↗
PubMed2003

Detection of proximal adenomatous polyps with screening sigmoidoscopy: a systematic review and meta-analysis of screening colonoscopy.

BACKGROUND: The relative effectiveness of flexible sigmoidoscopy compared with colonoscopy to screen for colorectal cancer depends on the magnitude of the association between findings in the proximal and distal colon and the false-negative rate of screening sigmoidoscopy for proximal neoplasia. To address this, we performed a systematic review and meta-analysis of screening colonoscopy studies. METHODS: Published studies through July 31, 2000, of asymptomatic patients undergoing screening colonoscopy were identified from the MEDLINE database. We generated pooled estimates of the odds ratio for the association between findings in the distal and proximal colon and the prevalence of isolated proximal adenomatous neoplasia. RESULTS: Using the sigmoid-descending colon junction to identify the beginning of the distal colon, the pooled odds ratio for the association between distal adenomatous polyps and any proximal neoplasia was 2.40 (95% confidence interval [CI], 1.42-4.05). Diminutive distal adenomatous polyps were also associated with proximal neoplasia (odds ratio, 2.36; 95% CI, 1.30-4.29). Distal hyperplastic polyps were not associated with proximal neoplasia (odds ratio, 1.44; 95% CI, 0.79-2.62). The prevalence of isolated advanced proximal neoplasia in the 3 studies was 2%, 3%, and 5%. Using the sigmoid-descending colon junction to identify the beginning of the distal colon yields a pooled estimate of isolated proximal neoplasia of 16.3% (95% CI, 13.6%-19.1%). CONCLUSIONS: Distal adenomatous polyps, including diminutive distal adenomatous polyps, are associated with an increased prevalence of synchronous proximal neoplasia. Two percent to 5% of patients undergoing screening colonoscopy may have isolated advanced proximal neoplasia. Even more patients may have isolated nonadvanced proximal neoplasia.

Adenomatous Polyps↗
PubMed2003

Corticosteroids and immunomodulators: postoperative infectious complication risk in inflammatory bowel disease patients.

BACKGROUND & AIMS: Many patients with inflammatory bowel disease receive corticosteroids and 6-mercaptopurine/azathioprine during elective bowel surgery. We investigated the postoperative infection risk for patients undergoing elective bowel surgery who were receiving corticosteroids and/or 6-mercaptopurine/azathioprine before surgery compared with patients not receiving these medications. METHODS: A retrospective cohort study was conducted on 159 patients with inflammatory bowel disease who underwent elective bowel surgery. There were 56 patients receiving corticosteroids alone, 52 patients receiving 6-mercaptopurine/azathioprine alone or with corticosteroids, and 51 patients receiving neither corticosteroids nor 6-mercaptopurine/azathioprine. Postoperative infectious complications to time of discharge were categorized into major and minor complications. RESULTS: Patients receiving corticosteroids had an adjusted odds ratio for any and major infectious complications of 3.69 (95% confidence interval [CI], 1.24-10.97) and 5.54 (95% CI, 1.12-27.26), respectively. The adjusted odds ratio for patients receiving 6-mercaptopurine/azathioprine for any and major infectious complications was 1.68 (95% CI, 0.65-4.27) and 1.20 (95% CI, 0.37-3.94), respectively. CONCLUSIONS: Preoperative use of corticosteroids in patients with inflammatory bowel disease who are undergoing elective bowel surgery is associated with an increased risk of postoperative infectious complications. 6-Mercaptopurine/azathioprine alone and the addition of 6-mercaptopurine/azathioprine for patients receiving corticosteroids was not found to significantly increase the risk of postoperative infectious complications.

Adjuvants, Immunologic↗
PubMed2003

Prevention and treatment of stress ulcers in critically ill patients.

Critically ill patients are at increased risk of developing stress-related mucosal lesions. The pathogenesis of stress-related mucosal disease is not entirely clear, but probably is associated with impairment of mucosal protective mechanisms due to compromised gastric mucosal microcirculation. Acid also plays an integral role. The incidence of gastrointestinal bleeding among intensive care unit patients has been declining over the past 30 years. Only a small proportion of patients with stress-related mucosal lesions develop clinically overt bleeding, and the majority of the overt bleedings do not lead to hemodynamic instability. However, the presence of gastrointestinal bleeding in a critically ill patient predicts markedly increased mortality. Prolonged mechanical ventilation and coagulopathy are the most important predictors of stress ulcer related bleeding. Critically ill patients with stress ulcer related bleeding should be managed in the acute setting just as patients presenting with upper gastrointestinal bleeding. Available evidence supports the use of stress ulcer prophylaxis in patients with risk factors for bleeding. Both histamine 2 receptor antagonists and sucralfate are effective forms of stress ulcer bleeding prophylaxis. More potent acid suppression by proton pump inhibitors may offer additional benefit in the prevention of stress ulcer bleeding.

Aged↗
PubMed2002

Initial evaluation of rectal bleeding in young persons: a cost-effectiveness analysis.

BACKGROUND: Evaluation of rectal bleeding in young patients is a frequent diagnostic challenge. OBJECTIVE: To determine the relative cost-effectiveness of alternative diagnostic strategies for young patients with rectal bleeding. DESIGN: Cost-effectiveness analysis using a Markov model. DATA SOURCES: Probability estimates were based on published medical literature. Cost estimates were based on Medicare reimbursement rates and published medical literature. TARGET POPULATION: Persons 25 to 45 years of age with otherwise asymptomatic rectal bleeding. TIME HORIZON: The patient's lifetime. PERSPECTIVE: Modified societal perspective. INTERVENTIONS: Diagnostic strategies included no evaluation, colonoscopy, flexible sigmoidoscopy, barium enema, anoscopy, or any feasible combination of these procedures. OUTCOME MEASURES: Life expectancy and costs. RESULTS OF BASE-CASE ANALYSIS: For 35-year-old patients, the no-evaluation strategy yielded the least life expectancy. The incremental cost-effectiveness of flexible sigmoidoscopy compared with no evaluation or with any strategy incorporating anoscopy (followed by further evaluation if no anal disease was found on anoscopy) was less than $5300 per year of life gained. A strategy of flexible sigmoidoscopy plus barium enema yielded the greatest life expectancy, with an incremental cost of $23 918 per additional life-year gained compared with flexible sigmoidoscopy alone. RESULTS OF SENSITIVITY ANALYSIS: As patient age at presentation of rectal bleeding increased, evaluation of the entire colon became more cost-effective. The incremental cost-effectiveness of flexible sigmoidoscopy plus barium enema compared with colonoscopy was sensitive to estimates of the sensitivity of the tests. In a probabilistic sensitivity analysis comparing flexible sigmoidoscopy with anoscopy followed by flexible sigmoidoscopy if needed, the middle 95th percentile of the distribution of the incremental cost-effectiveness ratios ranged from flexible sigmoidoscopy yielding an increased life expectancy at reduced cost to $52 158 per year of life gained (mean, $11 461 per year of life saved). CONCLUSIONS: Evaluation of the colon of persons 25 to 45 years of age with otherwise asymptomatic rectal bleeding increases the life expectancy at a cost comparable to that of colon cancer screening.

Adult↗
PubMed2002

Colonic dysplasia and cancer in inflammatory bowel disease.

Extracolonic malignancies are a relatively rare complication of inflammatory bowel disease. In contrast, colorectal cancer remains a major concern for patients with long-standing UC. The best available evidence suggests that patients with long-standing Crohn's colitis are at similar risk for colorectal cancer as those patients with long-standing UC. In patients with UC, the magnitude of this increased risk appears to be greater in patients with more extensive colonic involvement. It appears that the magnitude of this risk increases with increasing duration of disease, at least in UC. Whether this reflects the increased risk of cancer that occurs with the aging process or a separate phenomena distinct to UC is unclear. To date, the methods available to reduce the risk of cancer are less than optimal. Although surgical procedures eliminate the risk, the mental and physical sequelae of these procedures can be substantial. Surveillance with colonoscopic biopsies is likely effective in reducing although not eliminating the risk of colorectal cancer. Efforts to develop chemopreventative agents and improved surveillance methods remain areas of active investigation.

Colitis, Ulcerative↗
PubMed2002

The association between hepatitis C infection and survival after orthotopic liver transplantation.

BACKGROUND & AIMS: The effect of hepatitis C viral (HCV) infection on patient and allograft survival after orthotopic liver transplantation is controversial. Hepatitis C recurrence after transplant is inevitable, but studies to date have not found a survival difference between recipients with and without HCV. METHODS: Using data from the United Network for Organ Sharing, we performed a retrospective cohort study of 11,036 patients who underwent 11,791 liver transplants between 1992 and 1998. The hazard rates of patient and allograft survival for patients who were HCV-positive as compared with patients who were HCV-negative were assessed by proportional-hazards analysis, with adjustment for potential confounding variables, including donor, recipient, and transplant center characteristics. RESULTS: Liver transplantation in HCV-positive recipients was associated with an increased rate of death (hazard ratio, 1.23; 95% confidence interval [CI], 1.12-1.35) and allograft failure (hazard ratio, 1.30; 95% CI, 1.21-1.39), as compared with transplantation in HCV-negative recipients. This reduction in survival persisted after adjusting for potential confounders. There was an interaction between HCV and sex (P < 0.001) with the effect of HCV on survival being most pronounced in female recipients (patient survival hazard ratio, 1.56; 95% CI, 1.35-1.81; allograft survival hazard ratio, 1.51; 95% CI, 1.34-1.70). CONCLUSIONS: HCV infection significantly impairs patient and allograft survival after liver transplantation.

Adult↗
PubMed2002

Leaf respiration at different canopy positions in sweetgum (Liquidambar styraciflua) grown in ambient and elevated concentrations of carbon dioxide in the field.

Trees exposed to elevated CO2 partial pressure ([CO2]) generally show increased rates of photosynthesis and growth, but effects on leaf respiration are more variable. The causes of this variable response are unresolved. We grew 12-year-old sweetgum trees (Liquidambar styraciflua L.) in a Free-Air CO2 Enrichment (FACE) facility in ambient [CO2] (37/44 Pa daytime/nighttime) and elevated [CO2] (57/65 Pa daytime/nighttime) in native soil at Oak Ridge National Environmental Research Park. Nighttime respiration (R(N)) was measured on leaves in the upper and lower canopy in the second (1999) and third (2000) growing seasons of CO2 fumigation. Leaf respiration in the light (R(L)) was estimated by the technique of Brooks and Farquhar (1985) in the upper canopy during the third growing season. There were no significant short-term effects of elevated [CO2] on R(N) or long-term effects on R(N) or R(L), when expressed on an area, mass or nitrogen (N) basis. Upper-canopy leaves had 54% higher R(N) (area basis) than lower-canopy leaves, but this relationship was unaffected by CO2 growth treatment. In August 2000, R(L) was about 40% of R(N) in the upper canopy. Elevated [CO(2)] significantly increased the number of leaf mitochondria (62%), leaf mass per unit area (LMA; 9%), and leaf starch (31%) compared with leaves in ambient [CO(2)]. Upper-canopy leaves had a significantly higher number of mitochondria (73%), N (53%), LMA (38%), sugar (117%) and starch (23%) than lower-canopy leaves. Growth in elevated [CO2] did not affect the relationships (i.e., intercept and slope) between R(N) and the measured leaf characteristics. Although no factor explained more than 45% of the variation in R(N), leaf N and LMA were the best predictors for R(N). Therefore, the response of RN to CO2 treatment and canopy position was largely dependent on the magnitude of the effect of elevated [CO2] or canopy position on these characteristics. Because elevated [CO2] had little or no effect on N or LMA, there was no effect on R(N). Canopy position had large effects on these leaf characteristics, however, such that upper-canopy leaves exhibited higher R(N) than lower-canopy leaves. We conclude that elevated [CO2] does not directly impact leaf respiration in sweetgum and that barring changes in leaf nitrogen or leaf chemical composition, long-term effects of elevated [CO2] on respiration in this species will be minimal.

Carbohydrates↗
PubMed2002

Efficacy of anti-tumor necrosis factor therapy in patients with ulcerative colitis.

OBJECTIVES: Tumor necrosis factor-alpha (TNF-alpha) is an important cytokine involved in the pathogenesis of inflammatory bowel disease. The monoclonal antibody to TNF-alpha, infliximab, is effective in treating Crohn's disease. Preclinical studies suggest the importance of TNF-alpha in treating ulcerative colitis (UC). We report the effectiveness of infliximab for UC and examine factors predictive of response to medication. METHODS: Data from all UC patients receiving infliximab at four institutions were analyzed. Disease activity was determined by the Disease Activity Index. RESULTS: A total of 27 patients with active UC received inpatient (37%) and outpatient (63%) infliximab as single (52%) or multiple (two to 15) infusions (48%). Twelve patients (44%) achieved remission and six patients (22%) had partial response. Nine patients had no response; five subsequently underwent total colectomy. The median time to achieve response and remission was 4 days and the median duration 8 wk. Nine of the 18 patients who responded experienced 19 relapses; 18 of these relapses (95%) were successfully treated with repeat infusions. Steroid-refractory patients were less likely to respond to infliximab therapy than were steroid-responsive patients (33% vs 83%; p = 0.026). No other factors were predictive of response to infliximab. Two patients developed serious adverse events, including death in one case. CONCLUSIONS: Preliminary evidence suggest effectiveness of infliximab in the treatment of UC, including medically refractory severe disease. Individuals who are refractory to corticosteroids, however, may be unlikely to respond to infliximab. A randomized controlled trial is necessary to further investigate the efficacy of infliximab in patients with UC.

Adult↗
PubMed2002

Hospitalization and mortality rates from peptic ulcer disease and GI bleeding in the 1990s: relationship to sales of nonsteroidal anti-inflammatory drugs and acid suppression medications.

OBJECTIVES: Nonsteroidal anti-inflammatory drugs (NSAIDs) can cause peptic ulcer disease and upper GI bleeding. Acid suppression medications effectively treat NSAID-induced ulcers. However, it is unknown what effect the availability of proton pump inhibitors and over-the-counter preparations of NSAIDs and histamine type 2 receptor antagonists have had on population rates of hospitalization and mortality from GI toxicity. This study examines trends in hospitalization and mortality rates from GI toxicity during the 1990s. METHODS: We performed an analysis of secular trends of hospitalization and mortality rates from peptic ulcer disease, upper GI bleeding, and any GI bleeding using data from the National Hospital Discharge Survey, comparing them with sales of NSAIDs, aspirin, and acid suppression medications from 1992 to 1999. RESULTS: From 1992 to 1999, annual rates of hospitalization and mortality per 100,000 population for peptic ulcer disease declined from 205 to 165 and 7.7 to 6.0, respectively; calendar year was negatively correlated with both peptic ulcer disease hospitalization rates (p = -0.88, p = 0.007) and mortality rates (p = -0.71, p = 0.058). In contrast, these correlations did not reach statistical significance for upper or any GI bleeding (p > 0.1 for all comparisons). Sales of acid suppression medications were negatively correlated with peptic ulcer disease hospitalization rates (p = -0.76, p = 0.037) and mortality rates (p = -0.83, p = 0.015). Sales of NSAIDs were not positively correlated with hospitalization or mortality rates from peptic ulcer disease or GI bleeding (p > 0.2 for all comparisons). CONCLUSIONS: Despite changing patterns of use of NSAIDs and acid suppression medications during the 1990s, mortality rates from GI bleeding and peptic ulcer disease have been relatively stable, with an apparent decline in hospitalization rates and mortality from peptic ulcer disease. Changing rates of peptic ulcer disease morbidity and mortality were temporally related to increasing sales of antiulcerants but not to change in sales of NSAIDs.

Antacids↗
PubMedDate not supplied

Validity and completeness of the General Practice Research Database for studies of inflammatory bowel disease.

PURPOSE: The objective of this study was to evaluate the validity and completeness of the General Practice Research Database (GPRD) as a tool for research into inflammatory bowel disease epidemiology. METHODS: Patients diagnosed with inflammatory bowel disease were identified from GPRD. Mailed surveys were sent to the general practitioner caring for a stratified random sample of 170 of these patients and collected information on the diagnosis of inflammatory bowel disease and the most recent surgery and hospitalization. RESULTS: Usable surveys were returned for 157 patients (92%). The inflammatory bowel disease diagnosis was highly probable or probable in 144 (92%, 95% CI 86 to 96%). Among the 53 patients with a potentially incident inflammatory bowel disease diagnosis, 33 (62%) had the first recorded diagnosis in GPRD within 30 days of the date reported in the survey (median difference -8 days; interquartile range 0 to -81 days). Of 12 surgeries and 25 hospitalizations reported in the survey, 11 (92%) and 19 (76%) were identified in GPRD, respectively. CONCLUSIONS: The diagnosis of inflammatory bowel disease in GPRD appears reliable for most patients. Important medical events such as hospitalizations and surgery are recorded at a high rate, although algorithms to identify these events are complex.

Cohort Studies↗