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Biomedical subjects

S Williamson

Publications and source records attributed to S Williamson.

At least 37 records · Page 2Linked to original sources
PubMed2001

Identification of a target population for immunisation against East Coast fever in coastal Kenya.

Two experiments were carried out to identify the target population of cattle for immunisation against East Coast fever (ECF) using the infection-and-treatment method. Firstly, a sentinel-calf study was used to determine the age window for ECF immunisation by determining ages at clinical detection of infection with Theileria parva. Six groups of five naive cross-bred (Bos taurus/Bos indicus) male calves, introduced at intervals of 2 months at a mean age of 26 days, were exposed to natural tick challenge on a high ECF-risk, small-holder farm in the coastal lowland, coconut-cassava agro-ecological zone of coastal Kenya. Secondly, a challenge study evaluated the relationship between the presence of T. parva antibodies and immunity. Ten indigenous adult Zebu cattle and nine Zebu young stock purchased from farmers in the same zone, and eight cross-bred calves (survivors of the sentinel-calf study) were challenged with 10 times the immunising dose of T. parva Marikebuni stock. Twenty-four of these 27 cattle had high antibody titres before challenge. Two cross-bred calves, obtained from an ECF-free area and seronegative to T. parva schizont antigen, also were challenged and used as susceptible controls. Twenty-five (83%) of the 30 sentinel calves contracted ECF over an age range of 36-116 days (mean 72 days). The remaining five calves died of other causes within 2 months of arrival on the farm. Fourteen of the 25 calves survived the infection and developed antibodies to T. parva. Despite tick control, seven of these 14 calves had a second episode of ECF and two died. In total, 13 of the 25 calves that contracted ECF died. Only one of 19 indigenous Zebu animals developed clinical ECF when challenged with T. parva Marikebuni (mild clinical signs with spontaneous recovery). Of the eight cross-bred survivors from the first experiment, only one succumbed to ECF when challenged and it died. Both susceptible cross-bred calves developed severe clinical signs of ECF and one died. The experimental studies show that in the high ECF-risk areas of the coconut-cassava zone of coastal Kenya, immunisation against ECF in cross-bred (B. taurus/B. indicus) cattle should be targeted at an early age (preferably within 1-2 months of birth).

Agriculture↗
PubMed2001

Relativistic effects and two-body currents in (H)((-->)e(')p)n using out-of-plane detection.

Measurements of the (2)H((-->)e,e(')p)n reaction were performed with the out-of-plane magnetic spectrometers (OOPS) at the MIT-Bates Linear Accelerator. The longitudinal-transverse, f(LT) and f(')(LT), and the transverse-transverse, f(TT), interference responses at a missing momentum of 210 MeV/c were simultaneously extracted in the dip region at Q2 = 0.15 (GeV/c)(2). In comparison to models of deuteron electrodisintegration, the data clearly reveal strong effects of relativity and final-state interactions and the importance of two-body meson-exchange currents and isobar configurations. We demonstrate that such effects can be disentangled by extracting these responses using the novel out-of-plane technique.

Journal Article↗
PubMed2001

Theory of the growth and evolution of feather shape.

We present the first explicit theory of the growth of feather shape, defined as the outline of a pennaceous feather vane. Based on a reanalysis of data from the literature, we propose that the absolute growth rate of the barbs and rachis ridges, not the vertical growth rate, is uniform throughout the follicle. The growth of feathers is simulated with a mathematical model based on six growth parameters: (1) absolute barb and rachis ridge growth rate, (2) angle of helical growth of barb ridges, (3) initial barb ridge number, (4) new barb ridge addition rate, (5) barb ridge diameter, and (6) the angle of barb ramus expansion following emergence from the sheath. The model simulates growth by cell division in the follicle collar and, except for the sixth parameter, does not account for growth by differentiation in cell size and shape during later keratinization. The model can simulate a diversity of feather shapes that correspond closely in shape to real feathers, including various contour feathers, asymmetrical feathers, and even emarginate primaries. Simulations of feather growth under different parameter values demonstrate that each parameter can have substantial, independent effects on feather shape. Many parameters also have complex and redundant effects on feather shape through their influence on the diameter of the follicle, the barb ridge fusion rate, and the internodal distance. Simulated isochrones-the loci, or sets, of feather cells of the same age-have the same oblique chevron-shaped position in the mature feather as fault bars, which are isochronic defects in the barbules created by a disruptions during development. Accurate simulation of fault bar shape and position confirms the uniform absolute growth rate hypothesis and the general realism of the model. The theory defines a six-parameter feather morphospace, and provides many predictions about the developmental determination of feather shape that can be tested with detailed observations and experiments on developing feathers. This theory also provides testable predictions about the changes in developmental mechanisms required to evolve different feather shapes to accomplish various functions.

Animals↗
PubMed2001

Search for quadrupole strength in the electroexcitation of the delta+(1232).

High-precision 1H(e,e'p)pi(0) measurements at Q2 = 0.126 (GeV/c)2 are reported, which allow the determination of quadrupole amplitudes in the gamma*N-->Delta transition; they simultaneously test the reliability of electroproduction models. The derived quadrupole-to-dipole ( I = 3/2) amplitude ratios, R(SM) = (-6.5+/-0.2(stat+sys)+/-2.5(mod))% and R(EM) = (-2.1+/-0.2(stat+sys)+/-2.0(mod))%, are dominated by model error. Previous R(SM) and R(EM) results should be reconsidered after the model uncertainties associated with the method of their extraction are taken into account.

Journal Article↗
PubMed2001

Young children's figural selections: accuracy of reporting and body size dissatisfaction.

OBJECTIVE: The present study aimed to investigate children's accuracy of reporting body size and gender differences in body size dissatisfaction among preadolescent Australian children. METHOD: In an Australian partial replication of Dowdney, Woodward, Pickles, and Skuse (International Journal of Eating Disorders, 5, 29-40, 1995), children between 5 and 10 years of age (N = 195) made current and ideal figure choices using the Body Image Perception and Attitude Scale for Children (BIPAS-C), a nonsequentially ordered linear figural scale. RESULTS: The results are consistent with accurate identification of their body size by Australian children at all the age levels. The girls, irrespective of age, preferred smaller ideal than current shapes and expressed greater body size dissatisfaction than did the boys. DISCUSSION: The results are consistent with the body dissatisfaction found in adolescent and adult women and with those found in preadolescent children in the United States, Britain, and Israel.

Body Constitution↗
PubMed2001

Phase 1 clinical trial of irradiated autologous melanoma cells adenovirally transduced with human GM-CSF gene.

The objective of this study was to determine the safety and antitumor activity of an autologous GM-CSF-secreting melanoma cell vaccine that was engineered ex vivo with recombinant replication-incompetent adenovirus harboring a human GM-CSF gene (Adv/hGM-CSF). Melanoma samples were surgically obtained from 30 patients (15 female and 15 male, ages ranging from 23 to 87) and were processed for vaccine preparation. Due to stringent eligibility criteria, 9 out of 30 patients were enrolled in the phase 1 clinical trial (FDA IND7677). Melanoma cell lines established from surgical specimens of 9 patients were transduced with Adv/hGM-CSF (MOI of 100) and subsequently irradiated at 35 Gy. These cell lines secreted human GM-CSF in vitro at an average rate of 80-424 ng/10(6) cells/24 h. All patients were intradermally and subcutaneously injected at several sites with irradiated autologous melanoma cells (2x10(6)-1x10(7) in 300 microl saline), 2-10 times, at intervals of 4-8 weeks. None of the patients vaccinated showed any serious adverse systemic response. Three patients (nos.1, 6 and 7) demonstrated local reaction (erythema) to the vaccination. Tumor-specific CTL assays performed in the absence of K562 cells showed that the levels of CTLs in peripheral blood of 5 patients increased following vaccination, whereas those in one patient declined. Levels of CTLs assayed in the presence of K562 cells were considerably lower than those assayed in the absence of K562 cells, but were also found to increase following vaccination in the peripheral blood of 6 patients. A patient who had been vaccinated 10 times (patient 1) responded to the vaccination by apparent reduction in size of metastatic tumor in the lung. Immunohistochemical examination of the vaccination sites of patient 1, biopsied after the 3rd and 4th vaccination. showed that the vaccination sites responded with infiltration of inflammatory cells, such as T cells (CD3+, CD8+), macrophages and dendritic cells (CD83+), for a period up to about 8 days. These data suggest that repeated vaccinations with irradiated autologous GM-CSF-producing tumor cells were well tolerated by patients and led to the activation of an antitumor immune response in some patients.

Adenoviridae↗
PubMed2001

Declining the offer of flexible sigmoidoscopy screening for bowel cancer: a qualitative investigation of the decision-making process.

Qualitative methods were used to investigate decision-making among a group of older adults who declined the offer of flexible sigmoidoscopy screening for bowel cancer. Interviews were conducted with 60 people (30 men and 30 women) who either had not responded to the screening letter or who responded saying that they were not interested in participating. The findings suggest that low perceived susceptibility to bowel cancer, in terms of current health status, family history or absence of bowel symptoms. was an important factor in the decision to decline screening. Procedural barriers such as embarrassment, pain/discomfort and perceived unpleasantness of the test were reported as relatively minor, although the test was considered more physically intrusive than other screening tests. Avoidant attitudes emerged as an important theme and were reported by a third of respondents. Distinct patterns of decision-making were also observed and three groups emerged from accounts: (i) forgetting or avoiding making a decision about the test (ii) a confident rejection of the test based on a few salient factors, and (iii) a more careful consideration of the test focusing on issues of susceptibility. The findings are discussed in the context of models of health behaviour and bowel cancer screening participation research.

Colorectal Neoplasms↗
PubMed2001

Thin-section CT evidence of bronchial thickening in children with stable asthma: bronchoconstriction or airway remodeling?

RATIONALE AND OBJECTIVES: The authors performed this study to determine if bronchial wall thickening is present in children with moderate to severe asthma during periods free from clinical bronchoconstriction. MATERIALS AND METHODS: The authors obtained low (radiation) dose thin-section computed tomographic (CT) scans in each of 18 control subjects and 21 children with moderately severe but stable asthma. Spirometry was performed on all subjects at the time of CT scanning. Bronchial wall thickness and bronchial wall area were measured, and the percentage wall area (bronchial wall area divided by bronchial cross-sectional area) was calculated. The authors performed best-fit regression analysis of wall thickness and percentage wall area versus bronchial diameter and qualitative analysis of images for bronchial wall thickening. RESULTS: In asthmatic patients, the mean percentage of the predicted forced expiratory volume in 1 second was 0.88 +/- 0.09. The best fit regression line that demonstrated the relationship between wall thickness and bronchial diameter for patients with asthma differed significantly from that for control subjects (P < .005). The regression line that demonstrated the relationship between the percentage wall area and bronchial diameter for patients with asthma differed from that of the control subjects when bronchial wall thickness measurements were used to calculate the percentage wall area (P < .05). Results of qualitative analysis also showed significantly more bronchial wall thickening in asthmatic patients than in control subjects (P < .001). CONCLUSION: Bronchial wall thickening detected at thin-section CT in children with moderately severe asthma cannot be attributed solely to bronchoconstriction and may represent airway inflammation or remodeling.

Adolescent↗
PubMed2000

Predicting response to selection on a quantitative trait: a comparison between models for mixed-mating populations.

Two different theoretical frameworks have been developed to predict response to selection in a mixed mating population (in which reproduction occurs by a mixture of outcrossing and self-fertilization). The genotypic covariance model (GCM) and the structured linear model (SLM) rely on the same assumptions regarding quantitative trait inheritance, but use different genetic summary statistics. Here, we demonstrate the algebraic relationships between the various genetic metrics used in each theory. This is accomplished by reformulating the GCM in terms of the Wright-Kempthorne equation. We use stochastic simulations to investigate the relative accuracy of each theory for a range of selfing rates. The SLM is generally more accurate than the GCM, the most pronounced differences emerging in simulations with inbreeding depression for fitness. In fact, with strong inbreeding depression and high selfing rates, evolution can occur opposite the direction predicted by the GCM. The simulations also indicate that direct application of random mating models to partially selfing populations can produce very inaccurate predictions if quantitative trait loci exhibit dominance.

Animals↗
PubMed2000

Phylogeography of mitochondrial DNA variation in brown bears and polar bears.

We analyzed 286 nucleotides of the middle portion of the mitochondrial cytochrome b gene of 61 brown bears from three locations in Alaska and 55 polar bears from Arctic Canada and Arctic Siberia to test our earlier observations of paraphyly between polar bears and brown bears as well as to test the extreme uniqueness of mitochondrial DNA types of brown bears on Admiralty, Baranof, and Chichagof (ABC) islands of southeastern Alaska. We also investigated the phylogeography of brown bears of Alaska's Kenai Peninsula in relation to other Alaskan brown bears because the former are being threatened by increased human development. We predicted that: (1) mtDNA paraphyly between brown bears and polar bears would be upheld, (2) the mtDNA uniqueness of brown bears of the ABC islands would be upheld, and (3) brown bears of the Kenai Peninsula would belong to either clade II or clade III of brown bears of our earlier studies of mtDNA. All of our predictions were upheld through the analysis of these additional samples.

Animals↗
PubMed2000

Psychosocial influences on older adults' interest in participating in bowel cancer screening.

BACKGROUND: As part of a multicenter, randomized controlled trial of the efficacy of flexible sigmoidoscopy for the prevention of bowel cancer, an investigation of the predictors of screening interest was carried out in a subsample of older adults. METHOD: The aim of the study was to establish the predictive power of the Health Belief Model (HBM) and to evaluate the contribution of HBM elements in mediating the effect of other demographic and health variables which have been found to be associated with screening interest and participation. A total of 5,099 participants were sent a postal questionnaire which examined screening interest, attitudes toward screen ing (benefits and barriers), perceived bowel cancer risk, bowel cancer worry, bowel symptoms, health status, state anxiety, and optimism. A total of 3,648 questionnaires were returned completed, giving a response rate of 71.5%. RESULTS: The results showed that threat, barriers, and benefits explained 47% of the variance in interest. Demographic and health variables were also associated with screening interest, although most of their effect was mediated by the HBM constructs. DISCUSSION: This community study in older adults showed a high level of interest in participating in screening. The large sample size provided the opportunity to test the value of the HBM model and to examine mediation of demographic and health variables. The HBM proved to be a good model of screening interest. These results further our understanding of the decision processes in participating in cancer screening and point to directions to increase the level of participation in community samples.

Attitude to Health↗
PubMed2000

Treatment of vitamin D deficiency in patients with metastatic prostate cancer may improve bone pain and muscle strength.

PURPOSE: We performed a phase II study to determine whether pain associated with prostate cancer bone metastasis would respond to vitamin D replacement and parameters of muscle strength would be improved by vitamin D replacement therapy. MATERIALS AND METHODS: After a 4-week placebo period, eligible patients received orally 2,000 units vitamin D daily for 12 weeks. Pain questionnaires and measurements of muscle strength were competed at study enrollment and every 4 weeks thereafter. Serum calcium and vitamin D were measured at each clinic visit. RESULTS: A total of 16 patients with advanced hormone refractory prostate cancer were enrolled in this phase II study, of whom 7 (44%) had decreased baseline vitamin D. With vitamin D treatment, 4 patients (25%) had improvement in pain scores and 6 (37%) had improvement in muscle strength measurements. Improvement in pain scores correlated with improvement in subjective symptoms but did not result in a significant decrease in regular scheduled analgesic requirements. CONCLUSIONS: Vitamin D deficiency develops in a significant percent of patients with advanced hormone refractory prostate cancer. Supplementation with vitamin D may be a useful adjunct for improving pain, muscle strength and quality of life in this patient population.

Aged↗
PubMed2000

Acceptability of flexible sigmoidoscopy screening in older adults in the United Kingdom.

OBJECTIVES: To assess the acceptability of bowel cancer screening using flexible sigmoidoscopy (FS). SETTING: Adults aged 55 to 64 recruited from general practices in Welwyn Garden City and Leicester, which were the pilot and start up centres of a multicentred randomised controlled trial of FS screening (the ICRF/MRC Flexible Sigmoidoscopy Screening Trial). METHODS: Screenees (n=4422) were sent a three month follow up questionnaire that included measures of satisfaction with information given before the test, facilities at the test unit, attitudes of the staff, and explanation of the results. Measures of pain, embarrassment, feelings of being "in control" during the test, willingness to encourage others to have the test, and gladness to have participated were also included. In addition, semistructured telephone interviews were conducted with 60 screenees, stratified by screening outcome and gender. RESULTS: The follow up questionnaire was completed by 94% of screenees. Responses indicated a high level of satisfaction with the procedure: 99% were satisfied with the information given before the test, the facilities, the attitudes of the staff, and the explanation of their results; 91% reported only mild or no pain; 97% reported little or no embarrassment; and 99% were glad they had the test. Satisfaction ratings varied little by gender or outcome group. The quantitative results were reinforced by the qualitative data, which also revealed high acceptability. CONCLUSION: In the context of a clinical trial with dedicated trial staff, FS is a well tolerated procedure. There are high levels of satisfaction with service provision and positive attitudes towards the programme.

Colorectal Neoplasms↗
PubMed2000

Predictors of attendance in the United Kingdom flexible sigmoidoscopy screening trial.

OBJECTIVE: To investigate predictors of attendance in the United Kingdom flexible sigmoidoscopy screening trial. DESIGN: Prospective design in which participants completed a postal questionnaire before being sent their invitation for screening. SETTING: Welwyn Garden City and Leicester, United Kingdom. PARTICIPANTS: A total of 2758 patients aged 55 to 64, registered with general practices in the two centres, who (a) expressed interest in having the screening test, (b) completed a postal questionnaire, and (c) were subsequently invited for screening. MAIN RESULTS: The attendance rate among questionnaire responders was 76.1%. Multiple logistic regression analysis yielded a final model that included nine independent predictors of attendance. Patients with the following characteristics were more likely to attend: men; home owners; non-smokers; those who had regular check ups at the dentist; those with better subjective health; those who minded less about having medical tests; those who said they would definitely rather than probably take up the offer of sigmoidoscopy screening; and those who perceived less barriers and more benefits to having the test. CONCLUSIONS: The findings are broadly consistent with previous studies of screening participation, although subjective health emerged as an important predictor in this study. There was no evidence for "reverse targeting": attenders were not at lower (or higher) risk for colorectal cancer compared with non-attenders. The findings relating to attitudes and beliefs could be used in efforts to improve attendance, for example by developing information leaflets that address barriers to screening. Other findings could be used to target interventions to subgroups that have relatively low rates of screening participation.

Age Factors↗
PubMed2000

Family study of girls with attention deficit hyperactivity disorder.

OBJECTIVE: Because attention deficit hyperactivity disorder (ADHD) is relatively infrequent among girls, little is known about the causes of ADHD in girls. To help fill this gap in the literature, the authors assessed the familial transmission of ADHD in families ascertained through girls. METHOD: Interviewers who were blind to diagnosis administered structured psychiatric interviews to 140 girls with ADHD and their 417 first-degree relatives and to 122 girls without ADHD and their 369 first-degree relatives. RESULTS: The relatives of the ADHD girls had a significantly higher prevalence of ADHD, according to either the DSM-III-R or DSM-IV definition, than the relatives of the comparison girls. However, this did not differ from the prevalence the authors reported previously for families of boys with ADHD. Like the boys' families, the relatives of the girl probands also had significantly higher prevalences of antisocial, mood, anxiety, and substance use disorders, although the prevalence of familial antisocial disorders was lower than had been observed in the boys' families. There was no association between the DSM-IV subtypes of the probands and relatives. CONCLUSIONS: The familial transmission of ADHD and comorbid disorders generalizes to families of girls with ADHD. Neither proband gender nor subtype influences the familial transmission of ADHD.

Adolescent↗