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Biomedical subjects

Gareth Williams

Publications and source records attributed to Gareth Williams.

At least 55 records · Page 3Linked to original sources
PubMed2003

Chronic treatment with the thiazolidinedione, MCC-555, is associated with reductions in nitric oxide synthase activity and beta-cell apoptosis in the pancreas of the Zucker Diabetic Fatty rat.

The Zucker Diabetic Fatty (ZDF) rat is a model of impaired insulin sensitivity arising from hyperphagia owing to a mutation in the leptin receptor. In time, young ZDF rats, which are not initially diabetic, develop impaired pancreatic beta-cell function leading to apoptotic cell death. This results in an inability to fully compensate for the reduction in insulin sensitivity with hypersecretion of insulin. Young, pre-diabetic ZDF rats were treated, over a 4-week period, with the thiazolidinedione compound MCC-555, and the islet morphology studied in comparison to ZDF rats not given MCC-555. In particular, changes in the apoptotic incidence, as measured using TUNEL staining to localize apoptotic cells, were studied over the 4-week period. Changes in the induction of nitric oxide synthase and in the accumulation of nitrate/nitrite within the pancreas were also studied during the time course of administration of MCC-555. The study has demonstrated that the administration of MCC-555 significantly decreases the apoptotic incidence in the islets of Langerhans of pre-diabetic ZDF rats given the compound, as compared to those not given MCC-555, as well as decreasing the accumulation of nitrate/nitrite within the pancreas.

Animals↗
PubMed2003

The cannabinoid system: a role in both the homeostatic and hedonic control of eating?

Knowledge of the cannabinoid system and its components has expanded greatly over the past decade. There is increasing evidence for its role in the regulation of food intake and appetite. Cannabinoid system activity in the hypothalamus is thought to contribute to the homeostatic regulation of energy balance, under the control of the hormone leptin. A second component of cannabinoid-mediated food intake appears to involve reward pathways and the hedonic aspect of eating. With the cannabinoid system contributing to both regulatory pathways, it presents an attractive therapeutic target for the treatment of both obesity and eating disorders.

Animals↗
PubMed2003

Beyond 'beer, fags, egg and chips'? Exploring lay understandings of social inequalities in health.

This paper seeks to contribute to the limited body of work that has directly explored lay understandings of the causes of health inequalities. Using both quantitative and qualitative methodology, the views of people living in contrasting socio-economic neighbourhoods are compared. The findings support previous research in suggesting that lay theories about causality in relation to health inequalities, like lay concepts of health and illness in general, are multi-factorial. The findings, however, also illustrate how the ways in which questions about health and illness are asked shape people's responses. In the survey reported on here people had no problem offering explanations for health inequalities and, in response to a question asking specifically about area differences in health experience, people living in disadvantaged areas 'constructed' explanations which included, but went beyond, individualistic factors to encompass structural explanations that gave prominence to aspects of 'place'. In contrast, within the context of in-depth interviews, people living in disadvantaged areas were reluctant to accept the existence of health inequalities highlighting the moral dilemmas such questions pose for people living in poor material circumstances. While resisting the notion of health inequalities, however, in in-depth interviews the same people provided vivid accounts of the way in which inequalities in material circumstances have an adverse impact upon health. The paper highlights ways in which different methodologies provide different and not necessarily complementary understandings of lay perspectives on the causes of inequalities in health.

England↗
PubMed2003

HLA class II polymorphisms and susceptibility to recurrent respiratory papillomatosis.

Recurrent respiratory papillomatosis (RRP) is characterised by multiple laryngeal papillomas. Left untreated, the lesions enlarge, spread, and endanger the airway. Medical treatments are unsatisfactory, and repeated surgery remains the mainstay of therapy. RRP is caused by human papillomavirus (HPV) infection. However, since oral HPV infection is common and RRP is rare, other host and/or viral factors may contribute to pathogenesis. In an attempt to identify such factors, we have investigated 60 patients. The patients were HLA class I, II, and tumor necrosis factor TNF typed by sequence-specific primer PCR, and the results compared to those for 554 healthy controls by using Fisher's exact test. Peripheral blood mononuclear cell proliferative responses of 25 controls and 10 patients to HPV-11 L1 virus-like particles (VLP) were compared. Short-term VLP-specific T-cell lines were established, and recognition of L1 was analyzed. Finally, the L1 open reading frames of HPV isolates from four patients were sequenced. Susceptibility to RRP was associated with HLA DRB1*0301 (33 of 60 patients versus 136 of 554 controls, P < 0.0001). The three most severely affected patients were homozygous for this allele. A range of T-cell proliferative responses to HPV-11 VLP were observed in DRB1*0301-positive healthy donors which were comparable to those in DRB1*0301-negative controls. Individuals with juvenile-onset RRP also mounted a range of VLP responses, and their magnitude was negatively correlated with the clinical staging score (P = 0.012 by the Spearman rank correlation). DRB1*0301-positive patients who responded to L1 recognized the same epitope as did matched controls and produced similar cytokines. Sequencing of clinical isolates excluded the possibility that nonresponsiveness was the result of mutation(s) in L1.

Adolescent↗
PubMed2003

A randomized trial of sibutramine in the management of obese type 2 diabetic patients treated with metformin.

OBJECTIVE: To evaluate the effects of sibutramine (15 and 20 mg/day) on weight, metabolic control, and blood pressure in metformin-treated obese subjects with type 2 diabetes. RESEARCH DESIGN AND METHODS: A 12-month randomized prospective placebo-controlled double-blind study was performed. It included 21 primary and secondary care centers in England, Canada, France, and Belgium. A total of 195 subjects (44% male) with type 2 diabetes and a BMI >27 kg/m(2) were studied. Changes were assessed in weight, blood pressure and resting heart rate, HbA(1c), fasting glucose, and lipids. RESULTS: Sibutramine induced significant weight loss (P < 0.001) with both 15 mg/day (5.5 +/- 0.6 kg at 12 months) and 20 mg/day (8.0 +/- 0.9 kg), whereas placebo did not (0.2 +/- 0.5 kg). Weight loss > or = 10% was achieved by 14 and 27% of subjects receiving 15 and 20 mg, respectively, but by none given placebo. Glycemic control improved in parallel with weight loss, and subjects who lost > or = 10% weight showed significant decreases in both HbA(1c) (1.2 +/- 0.4%, P < 0.0001) and fasting plasma glucose (1.8 mmol/l, P < 0.001). HDL cholesterol increased slightly with the higher dose, whereas plasma triglycerides fell with both doses, especially in subjects with weight loss of > or = 10% (a 29% decrease, P < 0.01). Treatment was generally well tolerated. Sibutramine treatment raised sitting diastolic blood pressure by > or = 5 mmHg in a higher proportion of patients than did placebo (43% with 15 mg/day vs. 25% with placebo, P < 0.05), but this effect was less evident in subjects who had a weight loss of > or = 10% weight. Pulse rate increased significantly more with sibutramine, being > or = 10 bpm higher in 42% of treated patients versus 17% with placebo (P < 0.01). CONCLUSIONS: Sibutramine can be an effective adjunct to metformin treatment in selected obese type 2 diabetic subjects and improves metabolic control in individuals who lose weight.

Appetite Depressants↗
PubMed2002

Diet-induced obesity increases mu opioid receptor binding in specific regions of the rat brain.

Mu (mu) opioid agonists preferentially increase the intake of highly palatable food. Here we investigated changes in mu opioid binding in feeding- and reward-related brain regions in rats given a palatable diet for 17 weeks. Diet feeding induced variable obesity, and rats were stratified into 'high-weight gain' (HWG: weight increase, 513-695 g; n=12) and 'low-weight gain' (LWG: range: 396-502 g; n=11) groups. Chow-fed controls (n=9) gained 324-487 g during this time. Body fat mass and plasma leptin and insulin were significantly higher in LWG than in controls and even higher in HWG. mu-Receptor binding (measured in brain slices using [3H]-DAMGO (D-Ala(2), N-Me-Phe(4),Gly-ol(5)) and quantitative autoradiography) was significantly increased in specific forebrain regions of diet-fed rats. In the fundus striati, dorsal endopiriform nucleus and medial preoptic area (MPA), binding was similarly increased (30-40%; P<0.05 vs. controls) in the HWG and LWG groups. Increases in mu binding paralleled weight gain in the basolateral amygdala and basomedial amygdala, being approximately 20% above controls (P<0.001) in LWG and approximately 30% higher in HWG (P<0.05 vs. LWG). The medial habenula showed significantly higher binding (by approximately 40%) in HWG, with no significant changes in LWG. In all these areas (except the MPA), binding was significantly correlated with plasma leptin and insulin. We suggest that increased mu binding reflects decreased release of endogenous mu opioid peptides. This orexigenic system therefore seems unlikely to drive appetite for palatable food. Indeed, the mu opioid system in reward-related areas may be inhibited in dietary obesity, probably by increased plasma leptin and insulin, and this may represent a failed homeostatic attempt to limit overeating and eventually obesity.

Analgesics, Opioid↗
PubMed2002

Down-regulation of cannabinoid-1 (CB-1) receptors in specific extrahypothalamic regions of rats with dietary obesity: a role for endogenous cannabinoids in driving appetite for palatable food?

Agonists at cannabinoid-1 (CB-1) receptors stimulate feeding and particularly enhance the reward aspects of eating. To investigate whether endogenous cannabinoids might influence appetite for palatable food, we compared CB-1 receptor density in the forebrain and hypothalamus, between rats fed standard chow (n=8) and others given palatable food (n=8) for 10 weeks to induce dietary obesity. CB-1 receptor density was significantly decreased by 30-50% (P<0.05) in the hippocampus, cortex, nucleus accumbens and entopeduncular nucleus of diet-fed rats. Furthermore, CB-1 receptor density in the hippocampus, nucleus accumbens and entopeduncular nucleus was significantly inversely correlated with intake of palatable food (r(2)=0.25-0.35; all P<0.05). By contrast, CB-1 receptor binding in the hypothalamus was low and not altered in diet-fed rats. CB-1 receptor down-regulation is consistent with increased activation of these receptors by endogenous cannabinoids. Acting in areas such as the nucleus accumbens and hippocampus, which are involved in the hedonic aspects of eating, cannabinoids may therefore drive appetite for palatable food and thus determine total energy intake and the severity of diet-induced obesity. However, cannabinoids in the hypothalamus do not appear to influence this aspect of eating behaviour.

Animals↗
PubMed2002

Resistin and RELM-alpha gene expression in white adipose tissue of lactating mice.

The adipose tissue-derived factor resistin has been suggested to induce insulin resistance in obesity and inhibit adipocyte differentiation. Lactation is associated with major metabolic adaptations, which cause a profound loss of adipose tissue to support milk production by the mammary gland. This study has examined the expression of the resistin and resistin-like molecule-alpha (RELM-alpha) genes in white adipose tissue of lactating mice. Lactation induced significant increases in food intake and body weight, whereas body fat was substantially decreased at peak lactation. Resistin and RELM-alpha mRNAs were both detectable in gonadal, subcutaneous, and mammary gland fat; mRNA level was highest in gonadal fat and lowest in mammary tissue. There was no difference in resistin mRNA level in gonadal fat of lactating mice compared with controls. However, RELM-alpha mRNA fell by approximately 40% in early lactation and there was a parallel fall in the leptin mRNA level proportional to the loss of fat mass. These results indicate that the substantial reduction of adiposity in lactation does not lead to any changes in resistin gene expression; however, the fall in RELM-alpha mRNA might indicate a role for RELM-alpha in the metabolic adaptations of lactation.

Adipose Tissue↗
PubMed2002

Orexins and the treatment of obesity.

Orexin-A and -B are two peptides derived by proteolytic cleavage from a 130-amino acid precursor, prepro-orexin, which were recently isolated from the rat hypothalamus. Orexin-A is fully conserved across mammalian species, whilst rat and human orexin-B differ by two amino acids. These peptides bind to two Gq-coupled receptors, termed orexin-1 and orexin-2. The receptors are 64% homologous and highly conserved across species. Orexin-A is equipotent at orexin-1 and orexin-2 receptors, whilst orexin-B displays moderate (approximately 10 fold) selectivity for orexin-2 receptors. The distribution and pharmacology of the orexin peptides and their receptors indicate that they play a role in various regulatory systems including energy homeostasis and the regulation of feeding, the evidence for which is reviewed here.

Animals↗
PubMed2002

Orexins and feeding: special occasions or everyday occurrence?

Neurons expressing prepro-orexin, the precursor of orexin-A and -B, are found in the lateral hypothalamic area, a region classically implicated in driving feeding. Orexin-A induces feeding transiently when injected centrally, and food intake can be decreased when orexin action is disrupted by immunoneutralization of orexin-A, or by pharmacological blockade of orexin receptors, or by transgenic knockout of orexin. Here, we argue that orexin neurons may act to stimulate feeding in the short term, and that important regulatory signals may be a fall in plasma glucose (stimulatory), countered by satiety signals generated by eating, such as gastric distention (inhibitory).

Animals↗
PubMed2002

Pulmonary artery catheter.

Controversy concerning the pulmonary artery catheter (PAC) and its use as a bedside clinical tool continues to be a significant bone of contention. In the pursuit of evidence-based medicine, a substantial effort has been made over the last 25 years to demonstrate the benefit or lack thereof of PAC-led therapy, and this endeavor still persists with large, randomized, clinical trials currently in progress both in the United States and in the United Kingdom. This article reviews the core evidence for and against PAC efficacy and safety and considers the most appropriate method for validation of such a device.

Catheterization, Swan-Ganz↗
PubMed2001

Dimeric versions of two short N-cadherin binding motifs (HAVDI and INPISG) function as N-cadherin agonists.

N-cadherin is a member of the classical cadherin family of homophilic binding molecules. Peptide competition studies have identified the HAVDI and INPISGQ sequences as functional binding motifs in extracellular domain 1 (ECD1) of N-cadherin. Whereas monomeric versions of these motifs function as specific N-cadherin antagonists, we now show that cyclic peptides containing a tandem repeat of the individual motifs function as N-cadherin agonists. In this context, when presented to neurons as soluble molecules, the dimeric versions of the motifs stimulate neurite outgrowth in a similar manner to native N-cadherin. The response to the dimeric agonist peptides was inhibited by monomeric versions of the same motif and also by recombinant N-cadherin ECD1 protein. The responses were also inhibited by antibodies to a fibroblast growth factor receptor (FGFR) binding motif in ECD4 of N-cadherin and by a specific FGFR antagonist (PD17304). These data suggest that the peptides function by binding to and clustering N-cadherin in neurons and thereby activating an N-cadherin/FGFR signaling cascade. The novel agonists will be invaluable for dissecting out those cadherin functions that rely on signaling as opposed to adhesion and clearly have the potential to be developed as therapeutic agents for the promotion of cell survival and axonal regeneration.

3T3 Cells↗