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Biomedical subjects

W Stevens

Publications and source records attributed to W Stevens.

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

Hematological effects and metal residue concentrations following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards.

The U.S. Fish and Wildlife Service required a chronic dosing study that assessed the health and reproductive effects of tungsten-iron and tungsten-polymer shot in adult game-farm mallards (Anas platyrhynchos) prior to granting permanent approval of the shot for waterfowl hunting. Herein, we present the effects of tungsten-iron and tungsten-polymer shot on various hematologic parameters and metal residue concentrations in the femur, liver, kidneys, and gonads. Thirty-two-bird groups (sexes equal) of adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150 day trial (26 January 1998 to 25 June 1998). An additional 12 mallards (sexes equal) received eight #4 lead shot (positive control) on day 0 of the study. Lead-dosed mallards had significantly decreased hematocrit, hemoglobin concentration, and whole-blood delta aminolevulinic acid dehydratase activity on day 7, as well as significant changes in a number of plasma chemistry parameters compared to ducks in the control, tungsten-iron, or tungsten-polymer groups. Mallards dosed with tungsten-iron or tungsten-polymer shot had occasional significant differences in hematocrit and plasma chemistry values when compared to control mallards over the 150 day period, but these changes were not considered to be indicative of deleterious effects. Low concentrations of tungsten were detected in gonad and kidney samples from males and females and in liver samples from females dosed with tungsten-polymer shot. Tungsten was also detected in femur samples from tungsten-polymer-dosed mallards. Higher concentrations of tungsten were detected in femur, liver, kidney, and gonad samples from tungsten-iron-dosed ducks. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards did not cause adverse hematological effects during the 150 day trial. Concentrations of tungsten in the femur, liver, kidneys, and gonads were generally higher in tungsten-iron-dosed ducks when compared to tungsten-polymer-dosed ducks.

Animals↗
PubMed2001

Reproductive effects and duckling survivability following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards.

Tungsten-iron and tungsten-polymer shot were given conditional approval for waterfowl hunting by the U.S. Fish and Wildlife Service based partly on the results of a 30-day acute toxicity trial utilizing mallards (Anas platyrhynchos). Final approval of the two tungsten-containing shot was contingent on the results of a 150-day study that assessed the health and reproductive effects of tungsten-iron and tungsten-polymer shot in adult mallards. Reproductive data are presented in this paper. Sixteen male and 16 female adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150-day trial (26 January 1998 to 25 June 1998). Reproductive performance was assessed during the last 90 days (day 61 to day 150) of the trial. There were no significant differences in egg production and fertility and hatchability of eggs from tungsten-iron- and tungsten-polymer-dosed ducks compared to control ducks. There was no evidence of differences in percent survivability and body weight of ducklings from tungsten-iron and tungsten-polymer mallards compared to ducklings from control ducks. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards during the 150 day trial did not adversely affect reproduction or their offspring.

Animals↗
PubMed2000

Modelling the short term consequences of smoking cessation in England on the hospitalisation rates for acute myocardial infarction and stroke.

OBJECTIVES: To estimate the short term event and cost consequences of achieving two smoking cessation targets for England among a cohort of 35-64 year olds, in terms of the number of hospitalised acute myocardial infarctions (AMIs) and strokes avoided. DESIGN: A spreadsheet model based on previous work and using data for England was constructed to simulate the effects of achieving the target set out in the government's tobacco white paper (target 1). We also examined the consequence of achieving the intensive smoking reduction witnessed in California (target 2). RESULTS: Target 1 would result in 347 AMI and 214 stroke hospitalisations avoided in the year 2000, and by 2010 this would be 6386 AMI and 4964 strokes avoided. Achieving target 2 would result in 739 AMI and 455 stroke hospitalisations avoided in 2000, and 14 554 AMI and 11 304 strokes avoided by 2010. Achieving target 1 would save pound524 million ( pound423 million discounted at a rate of 2.67% for stroke and 2.31% for AMI) and target 2 would save pound1.14 billion ( pound921 million discounted) in terms of National Health Service costs. CONCLUSION: In the short term (11 years), reductions in the prevalence of smoking will produce sizeable reductions in both events and hospital costs.

Adult↗
PubMed2000

Dual regulation of leptin secretion: intracellular energy and calcium dependence of regulated pathway.

Rodent leptin is secreted by adipocytes and acutely regulates appetite and chronically regulates body weight. Mechanisms for leptin secretion in cultured adipocytes were investigated. Acutely, energy-producing substrates stimulated leptin secretion about twofold. Biologically inert carbohydrates failed to stimulate leptin secretion, and depletion of intracellular energy inhibited leptin release. There appears to be a correlation between intracellular ATP concentration and the rate of leptin secretion. Insulin increased leptin secretion by an additional 25%. Acute leptin secretion is calcium dependent. When incubated in the absence of calcium or in the presence of intracellular calcium chelators, glucose plus insulin failed to stimulate leptin secretion. In contrast, basal leptin secretion is secreted spontaneously and is calcium independent. Adipocytes from fatter animals secrete more leptin, even in the absence of calcium, compared with cells from thinner animals. Acute stimulus-secretion coupling mechanisms were then investigated. The potassium channel activator diazoxide and the nonspecific calcium channel blockers nickel and cadmium inhibited acute leptin secretion. These studies demonstrate that intracellular energy production is important for acute leptin secretion and that potassium and calcium flux may play roles in coupling intracellular energy production to leptin secretion.

Adenosine Triphosphate↗
PubMed2000

Leptin responses to glucose infusions in obesity-prone rats.

The secretion of leptin is dually regulated. In fasting animals, plasma leptin concentrations reflect body fat stores, whereas the incremental leptin response to fasting or refeeding most likely reflects insulin-mediated energy flux and metabolism within adipocytes. Impaired secretion of leptin in either pathway could result in obesity. We therefore measured plasma leptin concentrations in fasted animals and plasma leptin concentrations after an intravenous glucose infusion in a rat model of obesity. Young Sprague-Dawley (S-D) and Fischer 344 (F344) rats had similar percent body fat and fasting glucose and fasting leptin concentrations. However, F344 animals had higher insulin concentrations and leptin responses to intravenous glucose than did the S-D animals. The animals were then fed a control or high-fat diet for 6 wk. High-fat fed animals gained more weight and body fat than did the control fed animals. Control and high-fat fed F344 animals gained approximately 40% (P < 0.0001) more weight and >100% (P < 0.01) more body fat than did the S-D animals. Fasting leptin concentrations and leptin concentrations after intravenous glucose infusions and feeding were more than double (P < 0.05) in F344 animals compared with S-D animals. Whether an animal is fed a control or high-fat diet had little effect on the leptin response to intravenous glucose. In conclusion, young, lean F344 animals, before the onset of obesity, demonstrated a greater acute leptin response to intravenous glucose than similarly lean S-D animals. After a 6-wk diet, F344 animals had a greater percent increase in body weight and insulin resistance and exhibited higher fasting leptin concentrations and a greater absolute leptin response to intravenous glucose compared with the S-D animals. The chronic diet (control or high fat) had little impact on the acute leptin response to intravenous glucose. F344 animals exhibit leptin resistance in young, lean animals and after aging and fat accumulation.

Absorptiometry, Photon↗
PubMed2000

[Latex allergy and cross-reactions: a new threat?].

Allergy to latex proteins has become an important problem, especially in the medical profession, but also in people who have regularly contact with latex products. The responsible antigens are proteins, which are present in the natural rubber latex (NRL), extracted from Hevea brasiliensis. These proteins are important in the synthesis of rubber and in the defence of the plant against external noxes (pathogenesis related proteins). Life threathening reactions occur more frequently in the operating theatre. Sensitisation can occur via different routes (aerogen, skin, parenteral, ...) but aerogenic sensitisation seems to be very important. Starch particles are important vectors of the antigens. Diagnosis is made via history, confirmed by demonstration of specific IgE via skin test (in vivo) or via an in vitro method (e.g. CAP, ELISA). Immunological cross reactions are very frequent with other plant or fruit allergens but cross allergy is less frequent (sensitivity and specificity of the in vitro test varies considerably depending on the nature of the fruit or vegetable investigated). There is also a cross reactivity with Ficus. Prevention with latex allergens becomes primordial in hospital settings. The industry is aware of the problem and produces more and more synthetic latex products.

Cross Reactions↗
PubMed1999

Alterations in immune functions during normal aging and Alzheimer's disease.

It is thought that aging induces immune changes, which are related to the pathophysiology of Alzheimer's disease (DAT). In this study, the total number of leukocytes, white blood cell differentiation, mitogen-induced lymphocytic proliferation, neutrophil phagocytosis and superoxide release, and prostaglandin E2 (PGE2) production by mitogen-stimulated whole blood cultures were comparatively investigated between healthy adults (range 22-45 years) and healthy elderly volunteers (range 70-91 years), and between DAT patients (range 56-94 years) and age-matched control subjects. Healthy elderly volunteers showed significantly lower phytohemagglutinin (PHA)-induced lymphocyte proliferation and percentage and absolute number of basophils than young volunteers. In normal volunteers, there were significant and negative correlations between age and the number of basophils. Patients with DAT showed a trend toward significantly higher PHA-induced lymphocyte proliferation and significantly decreased percentage and absolute number of large unstained cells than healthy volunteers. In DAT patients, the total number of leukocytes and the percentage and number of neutrophils were positively correlated with age. All other immune-inflammatory variables were not significantly altered either by the aging process or DAT. The present study suggests that aging and DAT may differently affect some immune variables.

Adult↗
PubMed1999

The relationship between rumination and eating disorders.

OBJECTIVE: Rumination has been described as a symptom in association with eating disorders, but also as a separate disorder. METHOD: A series of 8 female volunteers who reported rumination were systematically screened for the presence of eating disorders and other psychopathology. RESULTS: Seven met current or prior criteria for an Axis I disorder and five had a current or prior eating disorder. DISCUSSION: The importance of screening for eating disorders among women who ruminate, and for screening for rumination among eating disorder patients, is stressed.

Adult↗
PubMed1999

The immune-inflammatory pathophysiology of fibromyalgia: increased serum soluble gp130, the common signal transducer protein of various neurotrophic cytokines.

Fibromyalgia is a chronic, painful musculoskeletal disorder characterized by widespread pain, pressure hyperalgesia, morning stiffness and by an increased incidence of depressive symptoms. The etiology, however, has remained elusive. The aim of the present study was to examine the inflammatory response system (IRS) in fibromyalgia. Serum interleukin-6 (IL-6), soluble IL-6 receptor (sIL-6R), sgp130, sIL-1R antagonist (IL-1RA) and sCD8 were determined in 33 healthy volunteers and in 21 fibromyalgia patients, classified according to the American College of Rheumatology criteria. Severity of illness was measured with several pain scales, dolorimetry and the Hamilton Depression Rating Scale (HDRS). Serum sgp130 was significantly higher and serum sCD8 significantly lower in fibromyalgia patients than in healthy volunteers. Serum sIL-6R and sIL-1RA were significantly higher in fibromyalgia patients with an increased HDRS score (> or = 16) than in normal volunteers and fibromyalgia patients with a HDRS score < 16. In fibromyalgia patients, an important part of the variance in sCD8 (50.3%) and IL-1RA (19.3%) could be explained by the HDRS score; 74.3% of the variance in sIL-6R was explained by the combined effects of pain symptoms and the HDRS score; and 25.9% of the variance in serum sgp130 was explained by stiffness. The results support the contention that pain and stiffness in fibromyalgia may be accompanied by a suppression of some aspects of the IRS and that the presence of clinically significant depressive symptoms in fibromyalgia is associated with some signs of IRS activation.

Antigens, CD↗
PubMed1998

Effect of bile acid composition and manipulation of enterohepatic circulation on leptin gene regulation.

In the rat, the ob gene product, leptin, putatively regulates energy balance via appetite control and energy expenditure. Bile acids in the intestinal lumen are necessary for efficient absorption of dietary lipids and may trigger the release of regulatory peptides. To investigate whether bile acids play a role in leptin gene expression, we altered the bile acid pool and then measured leptin mRNA levels in adipose tissue. Rats fed cholic acid (1% of chow wt/wt) for 2 weeks did not gain weight as rapidly as pair-fed control animals. Despite the lower weight, normalized leptin mRNA levels were 24% greater in cholic acid-fed rats compared with controls. Conversely, cholestyramine, a bile acid sequestrant, in chow (5% wt/wt) resulted in a 26% decline in leptin mRNA. Ligation of the common bile duct or chronic biliary diversion, experimental manipulations that decreased the intestinal concentration of bile salts, decreased leptin gene expression by 30% and 50%, respectively. A fluid and electrolyte (F/E) solution with and without taurocholate (36 micromol/h x 100 g rat[-1]) was then infused for 12 hours into the duodenum in animals with chronic biliary diversion. Taurocholate infusion resulted in a fourfold increase in steady-state adipocyte leptin mRNA levels compared with F/E infusion. Intravenous infusion of taurocholate or incubation of cultured adipocytes with taurocholate had no effect on leptin mRNA levels. We conclude that bile acids upregulate leptin gene expression indirectly, probably via effects on the absorption of dietary lipids or the release of neurohumoral mediators.

Adipocytes↗
PubMed1998

Nursing development units: their structure and orientation.

This paper provides background material about the Department of Health funded Nursing Development Units (NDUs), specifically their biographical and contextual characteristics, their aims and values, and their organization of work and resources acquired. The data were drawn from questionnaires to clinical leaders and from documentation. The findings are summarized under five questions which address the NDUs' values and aims, their organization of work, multiprofessional working, activeness in acquiring resources and support and the effect of the host organization. Taken as a whole, the aims match the vision of the ideal NDU specified by the pioneers of the NDU movement, and most clinical leaders subscribed to primary nursing as their preferred mode of organizing nursing work. Multiprofessional working was a common feature and there was considerable evidence of equality in team membership status. A small number of NDUs had been awarded grants for research and most were successful in generating income from conferences. Nearly all had links with an academic institution. NDUs that had the support of their Trust's management were able to market their services successfully. Our findings indicate that many NDUs have made good progress but their clinical leaders are the first to admit that there is much more to be done.

Clinical Nursing Research↗
PubMed1998

Cost-effectiveness of a primary care based physical activity intervention in 45-74 year old men and women: a randomised controlled trial.

OBJECTIVE: To assess the cost-effectiveness of a primary care based intervention aimed at increasing levels of physical activity in inactive people aged 45-74. METHODS: A total of 714 inactive people aged 45-74, taken from two west London general practices, were randomised into two groups. Intervention subjects were invited to a consultation with an exercise development officer, and offered a personalised 10 week programme to increase their level of regular physical activity, combining leisure centre and home based activities. Control subjects were sent information on local leisure centres. All subjects were followed up at eight months. RESULTS: There was a net 10.6% (95% confidence interval 4.5 to 16.9%) reduction in the proportion of people classified as sedentary in the intervention group compared with the control group, eight months after the intervention. The intervention group also reported an increase in the mean number of episodes of physical activity per week, as compared with the control group (an additional 1.52 episodes (95% confidence interval 1.14 to 1.95)). The cost of moving a person out of the sedentary group was shown to be less than 650 Pounds. The cost of moving someone to the now commonly recommended level was estimated at almost 2500 Pounds. CONCLUSIONS: Moderate physical activity can be successfully encouraged in previously sedentary men and women aged 45-74 through a primary care based intervention. The process of recruitment was the most important variable cost. A high uptake rate would maximise cost-effectiveness, and sensitivity analysis suggests that unit costs could be halved with a more effective recruitment strategy.

Age Factors↗
PubMed1998

Acute effects of lead, steel, tungsten-iron, and tungsten-polymer shot administered to game-farm mallards.

Sixteen-bird groups (sexes equal) of adult mallards (Anas platyrhynchos) were orally dosed with eight #4 steel short, eight #4 lead shot, eight BB-size tungsten-iron shot, eight BB-size tungsten-polymer shot, or were sham-dosed and maintained for 30 days (16 January 1996 to 15 February 1996). Half of the lead-dosed ducks (five males, three females) died during the study, whereas no ducks died in the other dosage groups. For lead-dosed ducks, hematocrit and hemoglobin concentration were decreased on day 15 of the trial, but not on day 30. Delta aminolevulinic acid dehydratase activity in lead-dosed ducks was lower when compared to steel-dosed ducks only. Plasma activities of selected enzymes were elevated in lead-dosed ducks when compared to enzyme activities of ducks in the other groups. For lead-dosed ducks, relative heart, liver, and kidney weights increased in comparison to relative weights of those organs of ducks in other groups. Histology of tissues indicated that renal nephrosis accompanied by biliary stasis was present in the eight lead-dosed ducks that died. For the eight lead-dosed ducks that survived, six had mild to severe biliary stasis. Mild biliary stasis was noted in five tungsten-iron dosed ducks and three tungsten-polymer dosed ducks. Amounts of lead in the femur, liver, and kidneys were higher in lead-dosed ducks than in ducks of the other four groups. Small amounts of tungsten were detected in the femur and kidneys of two tungsten-polymer dosed ducks. Higher concentrations of tungsten were detected in the femur, liver, and kidneys of all tungsten-iron dosed ducks. The rate of shot erosion was highest (80%) for the tungsten-polymer shot, followed by tungsten-iron (55%), lead (50%), and steel shot (33%). Results indicated that tungsten-iron or tungsten-polymer shot (8 shot/duck) orally administered to mallards did not adversely affect them during a 30-day trial.

Alanine Transaminase↗
PubMed1997

Effect of enteral versus parenteral nutrition on leptin gene expression and release into the circulation.

Leptin, a putative satiety hormone in rodents, is acutely regulated by fasting and refeeding. To determine the role of satiety hormones that are secreted by the gastrointestinal tract on leptin regulation, leptin mRNA and serum concentrations were measured after feeding rats similar calories with standard chow or infusion of total parenteral nutrition into the duodenum or intravenously. We have demonstrated that leptin gene expression and hormone secretion into the circulation are stimulated equally in the three experimental paradigms; it is unlikely that satiety factors secreted by the intestinal tract play a significant role in leptin regulation. Furthermore, intravenous infusion of individual components of TPN demonstrated that intravenous glucose infusion was mostly responsible for stimulation of the leptin gene and hormone secretion.

Adipocytes↗
PubMed1997

Stress in community care teams: will it affect the sustainability of community care?

The study investigated whether community care is sustainable by examining the levels of stress and burnout that affect community mental health staff. Six teams from around Great Britain were chosen to take part, representing a number of different facets of care: the type of community model, whether it was in an inner city or suburban area and whether the team had been part of a scientific evaluation of care, in which case it may have contained more experienced and more highly trained staff. The results indicated that community care staff experienced high levels of burnout as a result of the work stressors. These levels were higher than those found in any published study of health professionals within hospitals, but are similar to those found in community teams recently. There was no evidence that any particular model of community care produced less burnout, but working in an inner city did seem to produce the highest levels. There did seem to be some benefit from a moderate staff turnover within teams. These results mirror those of other recent studies. Models of community care can only be sustained by reducing their toxicity on the staff who have to make them work. Therefore, levels of stress and burnout should be included in any evaluation of the cost-effectiveness of service models. The alleviation of these high levels through individual and organisational interventions should now be a high priority.

Adult↗
PubMed1996

In-frame exon 2 deletion in insulin receptor RNA in a family with extreme insulin resistance in association with defective insulin binding: a case report.

The phenotype and allelic expression of the insulin receptor gene is presented in a family with a patient with type A insulin resistance. Compared to controls, insulin receptor binding in transformed lymphocytes was 100%. 33% and 13% in the father, mother and proband, respectively. Reduced insulin receptor binding co-segregated with altered insulin receptor mRNA expression; the mother and daughter expressed eight insulin receptor mRNA species, including a set of four normal sized and a set of four shorter mRNA transcripts. In the proband the levels of the normal sized mRNA transcripts were suppressed relative to the shorter transcripts. Reverse polymerase chain reaction (PCR) revealed that the shorter transcripts contained an in-frame deletion of exon 2. Sequencing of the entire insulin receptor coding region revealed a paternally inherited A to T substitution in nucleotide 3205, converting isoleucine 996 to phenylalanine, which does not co-segregate with reduced binding. Therefore, we hypothesize that two findings are necessary for the presentation of type A insulin resistance in this patient: an in-frame deletion of the insulin receptor exon 2 that codes for amino acids crucial for insulin binding: and an inhibition of expression of the paternal insulin receptor allele.

Adolescent↗