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Biomedical subjects

B Tomlinson

Publications and source records attributed to B Tomlinson.

At least 55 records · Page 3Linked to original sources
PubMed2000

Obesity, independent of insulin resistance, is a major determinant of blood pressure in normoglycemic Hong Kong Chinese.

Obesity and insulin resistance are considered important links underlying the development of hypertension. In Caucasians, there have been many reports of an association between insulin resistance and hypertension. However, this relationship is not consistently found in other ethnic groups. In this study, we examined the involvement of insulin resistance (assessed as fasting insulin-glucose product, FIGP) and general and central obesity as potential links in the development of hypertension in 413 normoglycemic Hong Kong Chinese (56.9% hypertensive) subjects. Anthropometric parameters (waist circumference [WC], waist-to-hip ratio [WHR], body mass index [BMI]), surrogate measures of insulin resistance (fasting plasma glucose, insulin, FIGP), fasting lipids and systolic (SBP) and diastolic (DBP) blood pressure were measured. Both male and female hypertensives were more obese and dyslipidemic, and the females had higher indices of insulin resistance than the normotensive subjects of the same gender. Before adjustment for age, gender, and adiposity, FIGP correlated with SBP in the total (r = .19, P = .009) and low BMI (r = .23, P < .05) and low WHR (r = .25, P < .01) groups. However, after adjustment, there was no significant relationship between FIGP and blood pressure. In contrast, BMI and WC were strongly associated with blood pressure (r > or = .41, P < .001 for both DBP and SBP in the total population), although in the group with general obesity, the strength of the relationship was weaker (r > or = .13). These relationships persisted after adjustment for age, gender, and FIGP. Obesity, therefore, appears to have a predominant role compared with insulin resistance in determining blood pressure in these normoglycemic Chinese.

Adult↗
PubMed2000

Tumor necrosis factor alpha gene G-308A polymorphism in the metabolic syndrome.

Tumor necrosis factor alpha (TNF-alpha) is a multifunctional cytokine constitutively produced by adipose tissue that may mediate insulin resistance. Studies in Caucasian subjects have suggested that the G-308A transition in the 5' region of the TNF-alpha gene may be associated with insulin resistance and obesity. These factors have been proposed to underlie the clustering of type 2 diabetes, hypertension, and dyslipidemia found in the metabolic syndrome, the prevalence of which is reaching epidemic proportions in Hong Kong Chinese. We investigated the association of this gene polymorphism with the components of the metabolic syndrome including the lipid profile, as well as with the indices of obesity and insulin resistance as measured by the insulin-glucose product, in 440 Chinese subjects (healthy [27.5%] and overlapping groups with type 2 diabetes [54.1%], hypertension [38.8%], dyslipidemia [39.3%], or obesity [39.5%]). The frequency of the mutant A allele was 7.4% in 121 healthy controls and 9.0% in the total population. The mutation was not associated with any component of the metabolic syndrome or with the prevalence of albuminuria and retinopathy in these subjects. Furthermore, there was no difference in anthropometric measures, insulin resistance, or lipid levels between subjects with the GG genotype and those with the mutant allele. In summary, the TNF-alpha gene G-308A polymorphism is unlikely to play an important role in the development of these disorders in this population.

Diabetes Mellitus, Type 2↗
PubMed2000

Renin-angiotensin-aldosterone system gene polymorphisms and hypertension in Hong Kong Chinese.

In Chinese populations, hypertension is common and is a major risk factor for cerebrovascular and coronary heart disease. The renin-angiotensin-aldosterone system (RAAS) helps maintain blood pressure and salt homeostasis and appears important in the pathogenesis of hypertension and some forms of vascular disease. We investigated three RAAS gene polymorphisms, the angiotensin-converting enzyme (ACE) insertion/deletion, angiotensinogen (AGT) M235T and angiotensin II type 1 receptor A1166C polymorphisms in 232 hypertensive and 178 normotensive Chinese subjects. The hypertensives were generally more obese and dyslipidaemic. No significant differences in genotype or allele frequencies for any of the polymorphisms were identified between the groups, nor was there any interactive contribution to blood pressure by the ACE and AGT polymorphisms. However, there were large differences in genotype and allele frequencies between the healthy Chinese and published data for equivalent Caucasian populations. These findings suggest these polymorphisms are unlikely to be involved in the pathogenesis of hypertension in Chinese.

Adult↗
PubMed2000

Modulation of blood pressure and obesity with the dopamine D2 receptor gene TaqI polymorphism.

Pharmacological data suggest that obesity and blood pressure (BP) may be modulated through the dopamine D2 receptor (DD2R), which may represent an underlying mechanism that links these conditions. A TAQ:I polymorphism near the DD2R gene has been associated with indices of obesity in white populations. We compared anthropometric and fasting plasma biochemical parameters between 209 nondiabetic hypertensive and 174 gender-matched normotensive Chinese subjects. The hypertensives had increased dyslipidemia, increased fasting plasma glucose concentrations, and a greater degree of obesity. The A1 and A2 alleles of the DD2R gene TAQ:I polymorphism were identified with a polymerase chain reaction-based restriction fragment length polymorphism protocol. The A1 allele frequency was decreased in the hypertensives (42.0%) compared with the control subjects (52.0%, P=0.006), and genotype frequencies were different (P=0.05) between the 2 groups. In the combined population (n=383), systolic, diastolic, and mean arterial BPs were 6, 5, and 6 mm Hg lower, respectively, in subjects with the A1A1 genotype relative to the A2A2 genotype (all P<0.05), whereas skinfold thickness was increased at the iliac (P<0.001) and triceps (P<0.03) sites but not at the biceps or subscapular sites. Furthermore, this DD2R gene polymorphism was shown to be a significant independent predictor of diastolic BP and iliac and triceps skinfold thicknesses (all P<0.03). These contrasting associations of the DD2R TAQ:I polymorphism A1 allele with lower BP but increased markers of "gynoidal" or peripheral subcutaneous obesity (iliac and triceps skinfold thicknesses) in our Chinese population may provide some insight into the underlying relationship between BP and body fat distribution, but the exact nature of this link remains to be determined.

Adult↗
PubMed2000

Toxicity of complementary therapies: an eastern perspective.

Chinese traditional medicine is used extensively in Chinese populations, and other Asian countries employ similar therapies. Herbal treatments have a major role in these systems, and although most have a well-established safety record, occasional adverse effects are seen. Problems arise when toxic herbs are used in excessive doses, with improper preparation, or when they are substituted erroneously. There may also be adulteration with Western drugs or heavy metals, and interactions between herbs and Western drugs may also occur. It is always prudent to obtain a complete history of the use of herbal medications during any clinical assessment, particularly in Asian patients.

Complementary Therapies↗
PubMed2000

Antioxidant effects of Chinese traditional medicine: focus on trilinolein isolated from the Chinese herb sanchi (Panax pseudoginseng).

It is thought that oxygen-derived free radicals (OFR) cause lipid peroxidation, which contributes to the process of atherosclerosis, and they are also involved in the myocardial damage seen with ischemia and reperfusion. Antioxidants could potentially ameliorate such harmful effects. Many natural plant products have been shown to have antioxidant effects. Trilinolein, a triacylglycerol purified from Panax pseudoginseng, which is commonly used in Chinese traditional medicine, has been found to have pharmacological effects, including antioxidant activity that may explain the benefits in treating circulatory disorders perceived from the use of the herb over the centuries.

Animals↗
PubMed2000

Alternative therapies and medical science: designing clinical trials of alternative/complementary medicines--is evidence-based traditional Chinese medicine attainable?

Evidence-based traditional Chinese medicine is attainable. With good planning and a positive attitude, the remedies used in traditional Chinese medicine (TCM) and Chinese proprietary medicines can be studied at a standard acceptable to modern science. The identification of an active principal should not delay the search for effective remedies from the TCM pharmacopoeia. Herbal mixtures can be validly tested to establish their efficacy. Problems with potential batch-to-batch variation can be circumvented by appropriate randomization. Subsequent independent screening and randomization to treatment and placebo arms can allow for the individualization of treatments by TCM practitioners. However, clearly defined treatments are required and should be recorded in a manner that enables other suitably trained researchers to reproduce them reliably (e.g., using prescriptions in Chinese). Quality control of TCM is a prerequisite of credible clinical trials. Correct natural ingredients must be used without adulteration or erroneous substitution. Evidence of safety in man is essential, and in lieu of data from formal toxicity studies, clear, convincing, and impartial evidence of safety is needed based on their long-term use in mainstream TCM practice backed up by publications in the Chinese medical/scientific literature.

Clinical Medicine↗
PubMed2000

Hydroxychloroquine has no significant effect on lipids and apolipoproteins in Chinese systemic lupus erythematosus patients with mild or inactive disease.

OBJECTIVE: To investigate the effects of hydroxychloroquine (HCQ) in Chinese patients with systemic lupus erythematosus who were either on a low dose of prednisone or not on prednisone. METHODS: 65 consecutive Chinese lupus patients without features of nephritis underwent assessment of the fasting serum lipid profile, including total cholesterol (TC), triglycerides (TG), HDL-cholesteorl (HDL-C), LDL-cholesterol (LDL-C), apolipoprotein A-1 (apo A-1), apolipoprotein B (apo B) and lipoprotein (a) (Lp(a)). RESULTS: 44/65 (67.7%) patients were on HCQ with a dose of 244 +/- 86 mg daily and 34/65 (52.3%) patients were on 4.3 +/- 2.6 mg daily of prednisone. The percentages of patients taking prednisone and the mean dose in those patients receiving this treatment were not different between the groups with or without HCQ treatment. TG tended to be lower in those patients on HCQ (median and interquartile range) (1.0 (0.7-1.4) mmol/L vs 1.2 (0.8 1.6) mmol/L), but there were no significant differences in TC or other lipid parameters including Lp(a) between the 2 groups of patients with or without HCQ treatment. CONCLUSION: HCQ had no significant effect on the serum lipid profile in these lupus patients with mild or inactive disease. This finding probably reflects the low doses of corticosteroid used and a lower background lipid level in this population.

Adult↗
PubMed2000

Obesity is the key determinant of cardiovascular risk factors in the Hong Kong Chinese population: cross-sectional clinic-based study.

OBJECTIVES: To examine the interrelationships between obesity and various cardiovascular risk factors, and to investigate the relative importance of insulin and obesity in their associations with various pathophysiologies. DESIGN: Cross-sectional clinic-based study. SETTING: Medical clinics at a university teaching hospital, Shatin, Hong Kong. PARTICIPANTS: A heterogeneous cohort of 767 Hong Kong Chinese subjects with a mean age of 43 (standard deviation, 14) years. MAIN OUTCOME MEASURES: Body mass index, waist circumference, plasma insulin, insulin resistance index, fasting plasma glucose and lipid levels, blood pressure, and 24-hour urinary albumin excretion. RESULTS: Pathophysiological abnormalities and risk factors are frequently clustered to varying degrees. Compared with the control subjects, patients with at least one component of the metabolic syndrome were more obese, hyperinsulinaemic, insulin resistant, hyperglycaemic, hypertensive, dyslipidaemic, and albuminuric (all variables, P<0.001). Increasing degrees of body mass index, waist circumference, plasma insulin level, and insulin resistance index were associated with an increasing number of risk factors after adjusting for age and sex (all variables, P<0.02). Multiple regression analysis showed that obesity, as reflected by either the body mass index or waist circumference, had a closer association than plasma insulin with the fasting plasma glucose concentration, blood pressure, and high-density lipoprotein-cholesterol and triglyceride concentrations. Using 19.0-20.9 kg/m(2) as the reference body mass index interval, the lowest cardiovascular risk was associated with a body mass index of <23.0 kg/m(2). There was an increased risk of 3.1 and 5 times when the body mass index was 23. 0-24.9 kg/m(2) and > or =25 kg/m(2), respectively. CONCLUSIONS: Obesity, hyperinsulinaemia, and insulin resistance are characteristic features of Hong Kong Chinese patients who have various components of the metabolic syndrome. Obesity has a greater effect than plasma insulin on various pathophysiologies.

Adult↗
PubMed2000

IUPHAR Southeast Asian-Western Pacific Region--eighth Meeting. Pharmacology in the Next Millennium. 1-5 November 1999, Taipei, Taiwan.

This conference focused on some areas of particular interest to pharmacologists in the Asia-Pacific region, including prostanoids, drug metabolism and drugs from traditional Chinese herbs. Areas covered in the prostanoid sessions included reviews of the development of selective COX-2 inhibitors, the use of knockout mice to study the role of prostanoid receptors in various disease states, the interactions of G-protein-coupled receptor pathways, and the effects of prostanoid mimetics on autonomic neurons. Sessions on drug metabolism reviewed the use of transgenic mouse models for toxicological screening of new drugs, the use of a combination of probe drugs given together to identify the activity of a range of drug metabolizing enzymes in vivo, and the interaction of drug metabolizing enzymes and nitric oxide. In the presentations on herbal medicines, there were discussions about the regulatory status and the problems involved in conducting clinical trials with these preparations. There were a number of seminars on details of the basic or clinical pharmacology of some active principles derived from herbs, thus recognizing the intense effort by local pharmacologists to improve the scientific study of this important resource.

Journal Article↗
PubMed1999

Effects of losartan on the sexual behavior of male rats.

Many commonly used antihypertensive drugs such as diuretics and beta-blockers can interfere with sexual function in both sexes, causing loss of libido, impairment of erectile function and ejaculation in men, and delay or prevent orgasm in women. Newly developed antihypertensive drugs should ideally not interfere with the patients' quality of life including sexual function. This study examined the effects of losartan, a nonpeptide, specific antagonist for type I angiotensin II receptors, on the male sexual behavior of rats. Spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats were treated with losartan 30 mg/ kg/day or saline control for 7, 30 and 90 days. Dark-cycle video recording was used to analyze the male sexual activities of the rats. No significant alteration in male sexual performance was observed after 7 and 30 days of treatment with losartan. In contrast, SHRs treated with propranolol 5 mg/kg/day showed increases in intromission latency, ejaculation latency and postejaculatory period indicating decreased libido and erectile and ejaculatory function. Upon completion of 90 days of losartan administration, the mount latency of the SHR was significantly increased, suggesting a decrease in libido although other parameters were unchanged and there was no effect in WKY rats. It is therefore concluded that losartan may have an advantage in preservation of sexual function when used clinically for the treatment of hypertensive disorders.

Animals↗
PubMed1999

The antihypertensive effect of the berberine derivative 6-protoberberine in spontaneously hypertensive rats.

Berberine is a natural isoquinoline alkaloid found in plants of the Ranunculaceae and Berberidaceae families. Extracts from berberine-containing plants have been used as traditional Chinese folk remedies for centuries. The antihypertensive effects of the berberine derivative 6-protoberberine (PTB-6) were studied in spontaneously hypertensive rats (SHRs). In conscious SHRs, PTB-6 lowered the systolic blood pressure in a dose-dependent manner (6-PTB: 5 mg/kg, -31.1 +/- 1.6 mm Hg; 10 mg/kg, -42.4 +/- 3.1 mm Hg). Cardiac output using the thermodilution method was reduced in PTB-6-treated anesthetized SHRs with a tendency to decrease in heart rate. Injection of PTB-6 into the intracerebral ventricles of SHRs lowered the systolic arterial blood pressure and heart rate. The berberine derivative PTB-6 is an effective antihypertensive agent. The mechanism of the antihypertensive effect of PTB-6 is probably through a central sympatholytic effect.

Animals↗
PubMed1999

Consumption of green tea causes rapid increase in plasma antioxidant power in humans.

Green tea contains polyphenolic antioxidants that have shown anticarcinogenic properties in animal and in vitro experimental studies. Current data regarding absorption and bioavailability of tea antioxidants in humans, however, are conflicting. In this study, plasma and urine antioxidant power after ingestion of green tea was measured using the ferric reducing/antioxidant power (FRAP) assay (US patent pending) to assess absorption, systemic distribution, and renal excretion of green tea antioxidants in healthy adults. Results showed that absorption of green tea antioxidants was rapid, with peak increase in plasma FRAP of around 4% at 40 minutes after ingestion: mean increase was 44 +/- 9 (SE) mumol/l. Excretion of polyphenolic antioxidants was also fast, peaking at 60-90 minutes, with significant correlation between urinary FRAP values and urinary total phenolic concentrations (r = 0.845, p < 0.001). In control studies, no increase in plasma or urine FRAP values was seen after intake of water. Although the amount of antioxidants absorbed was relatively small and the increase in plasma antioxidant power was of short duration, results demonstrate that some potentially anticarcinogenic polyphenolic antioxidants in green tea enter the systemic circulation soon after ingestion and cause a significant increase in plasma antioxidant status. This increase may, in turn, lower oxidative damage to DNA and so decrease risk of cancer.

Adult↗
PubMed1999

Intensification and the discourse of decline: a rhetoric of medical anthropology.

Our use of academic rhetorics does not just deliver old arguments more eloquently, but rather serves an epistemological purpose that enables us to ask new questions. The rhetorical strategy of intensification contests and dislodges unnoticed and untheorized presuppositions in academic arguments by redefining taken-for-granted uses of language, by reemphasizing the often overlooked social imbrication of metaphors presented as neutral scientific descriptions, and by reopening the textual and conceptual "black boxes" that allow authors to evade responsibility for their rhetorical choices. As deployed by Emily Martin (1987) in The Woman in the Body, intensification reveals how rhetorical gestures rooted in negative sociocultural attitudes toward women's bodies sometimes masquerade as "scientific" or "medical" knowledge. Martin reveals a pattern of medical metaphors that incorrectly associate menstruation and menopause with processes of decline and decay. Intensification enables Martin to contest the discourse of decline in accounts of menstruation by underscoring how it is shaped by cultural metaphors of production and information processing, by fore-grounding its anachronistic voices and their outmoded language and attitudes about women's reproductive systems, by calling attention to the persistently negative terminology that permeates discussions of women's reproductive processes, by emphasizing the different languages used for women's reproductive physiology and for similar but ungendered physiological processes, and by accentuating the celebratory language used for men's reproductive physiology. Intensification serves to demonstrate that these metaphors misrepresent or suppress fundamental aspects of physiology, inappropriately impose gendered attitudes on processes more accurately represented by nongendered terms, and negatively influence representations of women, their physiological processes, and their medical needs.

Adult↗
PubMed1999

A sibling-pair analysis of fasting lipids and anthropometric measurements and their relationship to hypertension.

Fifty non-diabetic, young Chinese hypertensives were compared to their normotensive siblings with respect to body fat distribution and fasting lipid and glucose (FPG) profiles. Sitting BP in hypertensives met conventional hypertension criteria after a 4-week washout period on placebo. Hypertensives had greater body mass index (BMI), subscapular skin-fold thickness (SFT), waist circumference (W), waist-to-height (WHtR) and waist-to-hip ratio (WHR), p<0.0001 for all. Higher triglycerides (p=0.004) and lower HDL-cholesterol (p=0.015) concentrations were also observed. Weight, W, WHtR and BMI were higher in hypertensives in both male (n=9) and female gender-concordant sibling pairs (n=21). Higher WHR, hip circumference and subscapular SFT were only seen in the male hypertensives. Hypertension is associated with central adiposity and adverse lipid profiles in this group of young hypertensives, supporting the hypothesis that obesity, particularly central, is closely associated with hypertension in Chinese as in other ethnic groups.

Adult↗