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Biomedical subjects

J Baxter

Publications and source records attributed to J Baxter.

At least 19 recordsLinked to original sources
PubMed2006

Pneumococcal vaccination during pregnancy for preventing infant infection.

BACKGROUND: Each year at least one million children worldwide die of pneumococcal infections. The development of bacterial resistance to antimicrobials adds to the difficulty of treatment of diseases and emphasizes the need for a preventive approach. Newborn vaccination schedules could substantially reduce the impact of pneumococcal disease in immunized children, but does not have an effect on the morbidity and mortality of infants less than three months of age. Pneumococcal vaccination during pregnancy may be a way of preventing pneumococcal disease during the first months of life before the pneumococcal vaccine administered to the infant starts to produce protection. OBJECTIVES: To assess the effect of pneumococcal vaccination during pregnancy for preventing infant infection. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group Trials Register (June 2004), CENTRAL (The Cochrane Library, Issue 2, 2004), MEDLINE (January 1966 to June 2004), EMBASE (January 1985 to June 2004), and reference lists of articles. SELECTION CRITERIA: Randomized controlled trials in pregnant women comparing pneumococcal vaccine with placebo or doing nothing or with another vaccine to prevent infant infections. DATA COLLECTION AND ANALYSIS: Two authors independently assessed methodological quality and extracted data using a data collection form. Study authors were contacted for additional information. MAIN RESULTS: Three trials (280 participants) were included. There was no evidence that pneumococcal vaccination during pregnancy reduces the risk of neonatal infection (one trial, 149 pregnancies, relative risk (RR) 0.51; 95% confidence interval (CI) 0.18 to 1.41). Although the data suggest an effect in reducing pneumococcal colonisation in infants by 16 months of age (one trial, 56 pregnancies, RR 0.33; 95% CI 0.11 to 0.98), there was no evidence of this effect in infants at two months of age (RR 0.28; 95% CI 0.02 to 5.11) or by seven months of age (RR 0.32; 95% CI 0.08 to 1.29). AUTHORS' CONCLUSIONS: There is insufficient evidence to support whether pneumococcal vaccination during pregnancy could reduce infant infections.

Female↗
PubMed2006

The impact of bioaugmentation on metal cyanide degradation and soil bacteria community structure.

Metal cyanides are significant contaminants of many soils found at the site of former industrial activity. In this study we isolated bacteria capable of degrading ferric ferrocyanide and K2Ni(CN)4. One of these bacteria a Rhodococcus spp. was subsequently used to bioaugment a minimal medium broth, spiked with K2Ni(CN)4, containing 1 g of either an uncontaminated topsoil or a former coke works site soil. Degradation of the K2Ni(CN)4 was observed in both soils, however, bioaugmentation did not significantly impact the rate or degree of K2Ni(CN)4 removal. Statistical analysis of denaturing gradient gel electrophoresis profiles showed that the topsoil bacterial community had a higher biodiversity, and its structure was not significantly affected by either K2Ni(CN)4 or bioaugmentation. In contrast, profiles from the coke works site indicated significant changes in the bacterial community in response to these additions. Moreover, in both soils although bioaugmentation did not affect rates of biodegradation the Rhodococcus spp. did become established in the communities in broths containing both top and coke works soil. We conclude that bacterial communities from contaminated soils with low biodiversity are much more readily perturbed through interventions such as contamination events or bioaugmentation treatments and discuss the implications of these findings for bioremediation studies.

Cyanides↗
PubMed2006

The application of the herbicide bromoxynil to a model soil-derived bacterial community: impact on degradation and community structure.

AIMS: Bromoxynil degradation by soil micro-organisms has been shown to be co-oxidative in character. In this study, we investigate both the impact of the application of increasing bromoxynil concentrations on soil-derived bacterial communities and how these changes are reflected in the degradation of the compound. Our aim was to test the hypothesis that the addition of bromoxynil to a soil-derived bacterial community, and the availability of a readily utilizable carbon source would have an impact on bromoxynil degradation, and that would be reflected in the bacteria present in the soil community. METHODS AND RESULTS: Degradation of bromoxynil was observed in soil-derived communities containing 15 mg l(-1), but not 50 mg l(-1) of the compound, unless glucose was added. This suggests that the addition of carbon stimulates co-oxidative bromoxynil degradation by the members of the bacterial community. Measurable changes in the bacterial community indicated that the addition of bromoxynil led to deterministic selection on the bacterial population, i.e. the communities observed arise through the selection of specific micro-organisms that are best adapted to the conditions in the soil. The addition of bromoxynil was also shown to have a negative impact on the presence of alpha and gamma-proteobacteria in the soil community. CONCLUSION: Bromoxynil degradation is significantly inhibited in bacterial soil communities in the absence of readily accessible carbon. The application of bromoxynil appears to exert deterministic selection on the bacterial community. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights the effects of increasing bromoxynil concentrations on a model bacterial population derived from soil. Soil communities show qualitative and quantitative differences to bromoxynil application depending on the availability of organic carbon. These findings might have implications for the persistence of bromoxynil in agricultural soils.

Bacteria↗
PubMed2004

Discrete-element method simulations: from micro to macro scales.

Many liquid systems encountered in environmental science are often complex mixtures of many components which place severe demands on traditional computational modelling techniques. A meso scale description is required to account adequately for their flow behaviour on the meso and macro scales. Traditional techniques of computational fluid dynamics and molecular simulation are not well suited to tackling these systems, and researchers are increasingly turning to a range of relatively new computational techniques that offer the prospect of addressing the factors relevant to multicomponent multiphase liquids on length- and time-scales between the molecular level and the macro scale. In this category, we discuss the off-lattice techniques of 'smooth particle hydrodynamics' (SPH) and 'dissipative particle dynamics' (DPD), and the grid-based techniques of 'lattice gas' and 'lattice Boltzmann' (LB). We highlight the main conceptual and technical features underpinning these methods, their strengths and weaknesses, and provide a few examples of the applications of these techniques that illustrate their utility.

Algorithms↗
PubMed2004

Analysis of the evolution of granular stress-strain and voidage states based on DEM simulations.

We review and discuss the results of our granular-dynamics simulations of the time evolution of the microstructure of compact granular beds as found in pouring, in hopper filling and discharge, and in a shear cell. These systems are mainly quasi-static. However, it is also common to encounter localized 'shear zones' with significant velocity/voidage fluctuations and high bulk-strain gradients. These narrow-banded zones are separated from near-static regions by sharp, discontinuous changes of bulk stress and voidage. Within these bands the granular assembly undergoes a transition from the quasi-static to the inertial state, where enduring particle contacts are increasingly replaced by collisional ones. We focus on the discrete particle origins of this inhomogeneous yield/flow behaviour. We show the usefulness of analysing the local evolution in terms of relative rotation of the grains which is observed to cause rapid local bulk dilation responsible for setting off avalanches near free-surface boundaries and protracted bulk-failure planes in confined static assemblies. We also present some evidence to suggest that allowing for effective continuous particle-particle interactions could approximate observed effects attributable to particle shape and surface roughness. Wavelet analyses have been applied successfully to generate the variations in periodicity and the relative sequence of evolution of the stress, strain-rate and voidage states in avalanching granular heaps and in the wall region of axially symmetric hopper flows.

Journal Article↗
PubMed2004

Insulin resistance as a modifier of the relationship between dietary fat intake and weight gain.

OBJECTIVE: To investigate whether insulin resistance modifies the rate of weight gain associated with a high percent of energy intake from dietary fat. DESIGN: Longitudinal, observational population study. SUBJECTS: A total of 782 nondiabetic Hispanic and non-Hispanic white free-living adult residents of the San Luis Valley in Colorado. MEASUREMENTS: Subjects were seen up to three times over a 14-y period. Weight, height, fasting insulin and glucose, diet by 24 h recall, and self-reported physical activity were collected at each visit. RESULTS: Percentage of energy intake from dietary fat was positively associated with weight gain over time (P=0.0103). High intake of dietary fat was more strongly related to weight gain in women than in men, and in those with lower total energy intake levels. The relationship between weight change and relative macronutrient intake also varied by baseline insulin sensitivity (P=0.0025). Weight gain over time in individuals with relative insulin resistance at baseline, as measured by QUICKI, was the greatest among those who consumed a higher percent of energy from fat. CONCLUSION: Percentage of total intake from dietary fat predicts weight change independent of total energy intake. Nondiabetic, insulin-resistant individuals are particularly susceptible to the weight gain associated with high levels of dietary fat intake. Further investigation into the relationship between insulin resistance, diet, and weight gain is warranted.

Adult↗
PubMed2004

Competition for attachment of aquaculture candidate probiotic and pathogenic bacteria on fish intestinal mucus.

Probiotics for aquaculture are generally only selected by their ability to produce antimicrobial metabolites; however, attachment to intestinal mucus is important in order to remain within the gut of its host. Five candidate probiotics (AP1-AP5), isolated from the clownfish, Amphiprion percula (Lacepéde), were examined for their ability to attach to fish intestinal mucus and compete with two pathogens, Aeromonas hydrophila and Vibrio alginolyticus. Two different radioactive isotopes were used to quantify competition between pathogens and probionts. Attachment of the pathogens was enhanced by the presence of the candidate probiotics. However, the addition of the candidate probiotics after the pathogens resulted in reduced pathogen attachment. Only AP5 caused lower attachment success of V. alginolyticus when added before the pathogen. When AP5 was added first, the average attachment change was 41% compared with 72% when added after V. alginolyticus, suggesting that the probiotic is displaced but that enhanced attachment of the pathogen does not occur. Conversely, when V. alginolyticus was added first, followed by AP5, attachment change was 37% while AP5 had 92% attachment change when added second. This implies that the pathogen was displaced by the candidate probiotic and therefore it appeared that, based on the ability of probiont AP5 to attach to mucus, the growth of the pathogen in the digestive tract might be suppressed by the candidate probiont's presence.

Aeromonas hydrophila↗
PubMed2002

Eight years' experience of gastrostomy tube management.

BACKGROUND AND STUDY AIMS: Increasingly, patients fed by gastrostomy tube are surviving the lifespan of the device. Data are scarce concerning the factors affecting the longevity and failure of gastrostomy tubes or the criteria for selection of replacement devices which leads to cost-effective patient management. The aims of the study were: to set criteria for selection of replacement gastrostomy tubes; to determine the causes of gastrostomy tube failure, and the factors affecting device longevity; and to examine the effect of initiating an educational programme for caregivers on resource utilization in long-term enteral nutrition patients. MATERIALS AND METHODS: We analyzed the clinical gastrostomy tube database compiled prospectively over 8 years by the nutrition team at Ninewells Hospital, Dundee. RESULTS: For 363 gastrostomy tubes inserted in 304 patients (160 women; median age 71), the median duration of gastrostomy tube use was 138 days. The total follow-up was 294 patient-years. Death occurred before the first gastrostomy tube replacement in 48 % of patients, but 20 % resumed oral nutrition. Tube failure mechanisms were: dislodgment, 28 %; perishing of tube material, 25 %; tube-related Candida albicans infection, 16 %; leakage, 7 %; and unspecified, 7 %. Of the balloon tubes and gastrostomy buttons, 8 % needed early replacement due to dislodgment and/or leakage. The cost per day for replacement percutaneous endoscopic gastrostomy (PEG) was Euro 2.12, for balloon tubes it was Euro 0.62, and for gastrostomy buttons Euro 1.80. Despite an increasing PEG insertion rate throughout the study period, yearly referrals for PEG-related problems dropped by 30 % between 1997 to 1999, coinciding with the initiation of an educational programme for caregivers. CONCLUSION: Tube longevity is mainly limited by the patient's diagnosis and prognosis. The choice of replacement device should be based on clinical factors. The use of more durable materials in the manufacture of gastrostomy tubes may prolong tube life and reduce cost. Education of patients and caregivers by a multidisciplinary nutrition support team promotes independence and limits demand on the service.

Adolescent↗
PubMed2001

Are Maori under-served for cardiac interventions?

AIMS: To examine hospitalisation rates for selected heart-disease-related diagnoses by age, gender, ethnicity and deprivation. METHODS: Four years' data on publicly-funded hospital discharges for: (i) heart failure and (ii) cardiac interventions were cross-classified by age group, gender, ethnicity (Maori/non-Maori) and deprivation (NZDep96). Population hospitalisation rates were calculated and displayed in multi-dimensional trellis graphs. RESULTS: The graphs show patterns of hospitalisation for chosen variables simultaneously. The expected increase in heart failure with age is found, as is an increase for the cardiac group up to ages 65-74 years. Clear gender differences were found. A further increase of heart failure with higher deprivation is evident throughout. For cardiac interventions, the relationship with deprivation is complex. Differences by ethnicity are disturbing. Hospitalisation rates for heart failure for Maori are typically more than double the non-Maori rates. In contrast, for the cardiac group Maori intervention rates are much lower. CONCLUSIONS: Graphical analysis that displays age, gender, ethnicity and deprivation simultaneously provides great insight into hospitalisation rates. Ethnic differences are particularly concerning and raise important questions about how well Maori needs are being met and how equitable is access to cardiac interventions for Maori.

Adult↗
PubMed2001

A case-control study of physical activity and non-insulin dependent diabetes mellitus (NIDDM). the San Luis Valley Diabetes Study.

PURPOSE: The purpose of this study was to examine the association between physical activity and non-insulin dependent diabetes mellitus (NIDDM). METHODS: We conducted a population-based case-control study in Hispanic and non-Hispanic white men and women, ages 20-74. A total of 167 cases with NIDDM and 1100 controls with normal glucose tolerance were included. All subjects completed an oral glucose tolerance test. RESULTS: Persons with recently diagnosed NIDDM reported significantly lower levels of physical activity than control subjects. For total metabolic units, the odds ratio for subjects in the highest tertile compared to those in the lowest tertile was 0.60 (95% confidence interval (CI) = 0.37-0.98) after adjusting for age, sex, ethnicity, and family history of diabetes. The adjusted odds ratio for persons reporting high levels of vigorous activity (at least three times per week for 20 minutes) was also less than 1, but was not statistically significant (odds ratio (OR) = 0.73, 95% CI = 0.47-1.14). Similar adjusted odds ratios were observed for high versus low levels of self-assessed work activity (OR = 0.50, 95% CI = 0.34-0.74) and leisure time physical activity (OR = 0.62, 95% CI = 0.44-0.90). Further adjustments for body mass index attenuated the strength of the association between physical activity and NIDDM. This is consistent with the hypothesis that obesity is one consequence of physical inactivity that puts individuals at increased risk for NIDDM. The association of physical activity and NIDDM was stronger in Hispanic than in non-Hispanic white subjects, although this difference was not statistically significant. CONCLUSIONS: High levels of physical activity are associated with lower odds of NIDDM and this relationship may be stronger in Hispanic subjects.

Adult↗
PubMed2001

Nonequivalent nuclear location of immunoglobulin alleles in B lymphocytes.

Individual B lymphocytes normally express immunoglobulin (Ig) proteins derived from single Ig heavy chain (H) and light chain (L) alleles. Allelic exclusion ensures monoallelic expression of Ig genes by each B cell to maintain single receptor specificity. Here we provide evidence that at later stages of B cell development, additional mechanisms may contribute to prioritizing expression of single IgH and IgL alleles. Fluorescent in situ hybridization analysis of primary splenic B cells isolated from normal and genetically manipulated mice showed that endogenous IgH, kappa and lambda alleles localized to different subnuclear environments after activation and had differential expression patterns. However, this differential recruitment and expression of Ig alleles was not typically seen among transformed B cell lines. These data raise the possibility that epigenetic factors help maintain the monoallelic expression of Ig.

Alleles↗
PubMed2000

Depressive symptoms in Hispanic and non-Hispanic White rural elderly: the San Luis Valley Health and Aging Study.

Literature on depression in rural and Hispanic elderly adults is sparse. This report describes the prevalence of depressive symptoms in 1,151 community-dwelling, Hispanic and non-Hispanic White participants in the San Luis Valley Health and Aging Study, conducted in rural Colorado during 1993-1995. The prevalence and odds ratios of high depressive symptoms, defined as a Center for Epidemiologic Studies Depression Scale score of > or = 16, were calculated. The crude prevalence of high depressive symptoms was 11.4% (95% confidence interval: 9.6, 13.6). Female gender, chronic diseases, dissatisfaction with social support, living alone, and lower income and education were associated with depressive symptoms. There were no ethnic differences in the men. The age-adjusted odds ratio of depressive symptoms in Hispanic women compared with that of non-Hispanic White women was 2.11 (95% confidence interval: 1.32, 3.38). After adjustment for multiple sociodemographic and health risk factors, the odds ratio in Hispanic women was 2.12 (95% confidence interval: 1.19, 3.80). Higher depressive symptoms in Hispanic women varied by acculturation level. The odds ratio in the high acculturation stratum was 1.56 (95% confidence interval: 0.75, 3.27) and in the low acculturation stratum was 2.51 (95% confidence interval: 1.11, 5.70). A lower acculturation level may increase the risk for depression in older Hispanic women.

Aged↗
PubMed2000

The relation between baseline HIV drug resistance and response to antiretroviral therapy: re-analysis of retrospective and prospective studies using a standardized data analysis plan.

To assess the relation between resistance to antiretroviral drugs for treatment of HIV-1 infection and virological response to therapy, results from 12 different studies were re-analysed according to a standard data analysis plan. These studies included nine clinical trials and three observational cohorts. The primary end-point in our analyses was virological failure by week 24. Baseline factors that were investigated as predictors of virological failure were plasma HIV-1 RNA, the number and type of new antiretroviral drugs in the regimen, and viral susceptibility to the drugs in the regimen, determined by genotyping or phenotyping methods. These analyses confirmed the importance of both genotypic and phenotypic drug resistance as predictors of virological failure, whether these factors were analysed separately or adjusted for other baseline confounding factors. In most of the re-analysed studies, the odds of virological failure were reduced by about twofold for each additional drug in the regimen to which the patient's virus was sensitive by genotyping methods, and by about two- to threefold for each additional drug that was sensitive by phenotyping.

Anti-HIV Agents↗
PubMed2000

Effect of iron(III) chitosan intake on the reduction of serum phosphorus in rats.

Because of the widespread use of aluminium- and calcium-containing phosphate binders for the control of hyperphosphataemia in patients with end-stage renal failure, an iron(III) chitosan complex was synthesised and fed to rats to measure its effect on serum phosphorus and calcium, intestinal phosphate binding and phosphate absorption. Thirty-six Wistar rats were randomly selected and distributed into a baseline group (n = 6), a control group (n = 8 (days 0-15), n = 8 (days 16-30)) and a treatment group (n = 8 (days 0-15), n = 8 (days 16-30)). The control groups ingested AIN-76 diet mix with a 1% w/w fibre content; however, the treatment groups had the fibre content completely substituted with iron(III) chitosan. The mean weights of the treated rats were slightly lower from 15 days (not significant); but overall, rat growth was not stunted in the treatment groups. The serum phosphorus levels of the treated group (n = 8) were significantly reduced after 15 days (P = 0.004; control: 5.7+/-0.9 mg dL(-1); treatment: 4.4+/-0.5 mg dL(-1); 95% CI of difference: 0.5-2.2) and 30 days (P = 0.002; control: 5.5+/-0.9 mg dL(-1); treatment = 4.1+/-06 mg dL(-1); 95% CI of difference: 0.6-2.3) as compared with the respective control group. The serum calcium-phosphorus product was 62.0+/-12.1 mg2 dL(-2) for the control and 45.1+/-6.6 mg2 dL(-2) for the treatment group after 30 days (P = 0.004). The serum iron concentration of the treatment group did not differ from the baseline value after 15 and 30 days, but the treatment group was significantly higher than the control group (P<0.05) after 30 days. The faeces phosphorus levels (mg day(-1)) were higher (P<0.01) and its iron content was much higher (P<0.01) for the treated group. The urine phosphorus (mg kg(-1)) was not significantly reduced for the treated group, but the mean was consistently less. The kidney and liver weights of both groups were similar, but the phosphorus content of the kidney (mg (g kidney)(-1)) was higher for the treated group after 30 days (P = 0.041; control, 4.2+/-1.2 mg g(-1) vs treatment, 5.6+/-1.4 mg g(-1). Because iron(III) chitosan had a high phosphorus-binding capacity of 308 (mg P) per gram of Fe3+ for both the in-vitro (pH 7.5) and in-vivo studies, which is greater than nearly all commonly used phosphate binders, and a small net phosphorus absorption difference of 3.7 mg day(-1), it is an efficient phosphate binder for lowering serum phosphate levels without increasing serum calcium levels.

Animals↗
PubMed1999

Indicators of nutritional risk in a rural elderly Hispanic and non-Hispanic white population: San Luis Valley Health and Aging Study.

OBJECTIVE: To describe the prevalence of nutritional risk factors among elderly residents in a rural Hispanic and non-Hispanic white population. DESIGN: A geographically based survey of community-dwelling elderly adults. SUBJECTS/SETTING: From July 1993 to July 1995, all Hispanic persons older than 65 years and an age-stratified, random sample of 69% of non-Hispanic white persons, from 2 Colorado counties, were invited to participate in a study of functional impairment and disability (81% responded). After exclusion of 184 respondents who required a surrogate respondent and 8 with missing diet data, the study consisted of 1,006 subjects. Interviews included questions similar to the Nutrition screening Initiative checklist, a 21-item food frequency questionnaire, and anthropometric measures. STATISTICAL ANALYSES PERFORMED: Gender- and ethnicity-specific, age-adjusted prevalence for each risk factor was estimated by use of logistic regression. RESULTS: Hispanic participants were more likely than non-Hispanic whites to report inadequate intake of vegetables, problems with teeth or dentures that limited the kinds and amounts of food eaten, difficulty preparing meals, and lack of money needed to buy food. Hispanic women reported nutritional risk factors more often than Hispanic men, although anthropometric markers indicated that Hispanic men may be at higher risk of nutritional deficiency. APPLICATIONS/CONCLUSIONS: Hispanic men and women had a higher prevalence of nutritional risk factors than non-Hispanic whites. Intervention programs targeting rural, elderly Hispanics should aim to ensure that basic nutrition needs (access to food, help preparing meals, and adequate dental care) are being met. Community programs to increase activity levels and consumption of nutrient-dense foods are recommended.

Aged↗