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Biomedical subjects

K S Channer

Publications and source records attributed to K S Channer.

At least 19 recordsLinked to original sources
PubMed2004

Testosterone replacement in hypogonadal men with angina improves ischaemic threshold and quality of life.

BACKGROUND: Low serum testosterone is associated with several cardiovascular risk factors including dyslipidaemia, adverse clotting profiles, obesity, and insulin resistance. Testosterone has been reported to improve symptoms of angina and delay time to ischaemic threshold in unselected men with coronary disease. OBJECTIVE: This randomised single blind placebo controlled crossover study compared testosterone replacement therapy (Sustanon 100) with placebo in 10 men with ischaemic heart disease and hypogonadism. RESULTS: Baseline total testosterone and bioavailable testosterone were respectively 4.2 (0.5) nmol/l and 1.7 (0.4) nmol/l. After a month of testosterone, delta value analysis between testosterone and placebo phase showed that mean (SD) trough testosterone concentrations increased significantly by 4.8 (6.6) nmol/l (total testosterone) (p = 0.05) and 3.8 (4.5) nmol/l (bioavailable testosterone) (p = 0.025), time to 1 mm ST segment depression assessed by Bruce protocol exercise treadmill testing increased by 74 (54) seconds (p = 0.002), and mood scores assessed with validated questionnaires all improved. Compared with placebo, testosterone therapy was also associated with a significant reduction of total cholesterol and serum tumour necrosis factor alpha with delta values of -0.41 (0.54) mmol/l (p = 0.04) and -1.8 (2.4) pg/ml (p = 0.05) respectively. CONCLUSION: Testosterone replacement therapy in hypogonadal men delays time to ischaemia, improves mood, and is associated with potentially beneficial reductions of total cholesterol and serum tumour necrosis factor alpha.

Androgens↗
PubMed2003

Effect of treatment of carotid artery stenosis on blood pressure: a comparison of hemodynamic disturbances after carotid endarterectomy and endovascular treatment.

BACKGROUND AND PURPOSE: Carotid intervention by carotid endarterectomy (CEA) or endovascular treatment may cause hemodynamic change. The immediate and long-term effects on blood pressure after these procedures were assessed. METHODS: Patients were randomized to CEA (n=49) or endovascular treatment (n=55) that comprised percutaneous transluminal angioplasty alone (n=31), balloon-expandable stent (n=13), or self-expandable stent (n=11). A baseline 24-hour ambulatory blood pressure recording was made before carotid intervention and repeated at 24 hours, 1 month, and 6 months after the procedure. RESULTS: In the first 24 hours after the procedure, episodes of hypotension occurred in 75% of the CEA group and 76% of the endovascular group; hypertension occurred in 11% and 13%, respectively. There was a significant fall in blood pressure at 1 hour after the procedure in both groups (24 and 16 mm Hg fall in CEA and endovascular groups, respectively), but this was only sustained in the endovascular group. The pattern of blood pressure response in the first 24 hours was significantly different (P<0.0001, ANCOVA). Systolic blood pressure was significantly lower at 1 and 6 months only in the surgical group (6 and 5 mm Hg fall, respectively). CONCLUSIONS: Both CEA and endovascular treatment have an effect on blood pressure stability, particularly within the first 24 hours after the procedure.

Aged↗
PubMed2003

Ethical problems in clinical practice.

Ethics is about judgment, which is rarely black and white. This paper highlights some of the ethical dilemmas that face practising clinicians in their everyday life and restates how useful the General Medical Council guidance is to make appropriate decisions. The authors have faced all eight of the clinical scenarios in this paper in their routine clinical practice.

Decision Making↗
PubMed2003

Testosterone as a protective factor against atherosclerosis--immunomodulation and influence upon plaque development and stability.

Inflammation plays a central pathogenic role in the initiation and progression of coronary atheroma and its clinical consequences. Cytokines are the mediators of cellular inflammation and promote local inflammation in the arterial wall, which may lead to vascular smooth muscle apoptosis, degradation of the fibrin cap and plaque rupture. Platelet adhesion and thrombus formation then occur, resulting clinically in unstable angina or myocardial infarction. Recent studies have suggested that cytokines are pathogenic, contributing directly to the disease process. 'Anti-cytokine' therapy may, therefore, be of benefit in preventing or slowing the progression of cardiovascular disease. Both oestrogens and testosterone have been shown to have immune-modulating effects; testosterone in particular appears to suppress activation of pro-inflammatory cytokines. Men with low testosterone levels are at increased risk of coronary artery disease. An anti-inflammatory effect of normal physiological levels of sex hormones may, therefore, be important in atheroprotection. In this Article, we discuss some of the mechanisms involved in atherosclerotic coronary artery disease and the putative link between testosterone deficiency and atheroma formation. We present the hypothesis that the immune-modulating properties of testosterone may be important in inhibiting atheroma formation and progression to acute coronary syndrome.

Apoptosis↗
PubMed2003

Testosterone inhibits the prostaglandin F2alpha-mediated increase in intracellular calcium in A7r5 aortic smooth muscle cells: evidence of an antagonistic action upon store-operated calcium channels.

Testosterone-induced vasodilatation is proposed to contribute to the beneficial effects associated with testosterone replacement therapy in men with cardiovascular disease, and is postulated to occur via either direct calcium channel blockade, or through potassium channel activation via increased production of cyclic nucleotides. We utilised flow cytometry to investigate whether testosterone inhibits the increase in cellular fluorescence induced by prostaglandin F(2alpha) in A7r5 smooth muscle cells loaded with the calcium fluorescent probe indo-1-AM, and to study the cellular mechanisms involved. Two-minute incubation with testosterone (1 microM) significantly inhibited the change in cellular fluorescence in response to prostaglandin F(2alpha) (10 microM) (3.6+/-0.6 vs 7.6+/-1.0 arbitrary units, P=0.001). The change in cellular fluorescence in response to prostaglandin F(2alpha) (10 microM) was also significantly attenuated in the absence of extracellular calcium (3.6+/-0.3 vs 15.6+/-0.7 arbitrary units, P=0.0000002), and by a 2-min incubation with the store-operated calcium channel blocker SK&F 96365 (50 microM) (4.7+/-0.8 vs 8.1+/-0.4 arbitrary units, P=0.003). The response was insensitive to similar incubation with the voltage-operated calcium channel blockers verapamil (10 microM) (12.6+/-1.2 vs 11.9+/-0.2 arbitrary units, P=0.7) or nifedipine (10 microM) (13.9+/-1.3 vs 13.3+/-0.5 arbitrary units, P=0.7). Forskolin (1 microM) and sodium nitroprusside (100 microM) significantly increased the cellular concentration of cyclic adenosine monophosphate and cyclic guanosine monophosphate respectively, but testosterone (100 nM-100 microM) had no effect. These data indicate that the increase in intracellular calcium in response to prostaglandin F(2alpha) occurs primarily via extracellular calcium entry through store-operated calcium channels. Testosterone inhibits the response, suggesting an antagonistic action upon these channels.

Animals↗
PubMed2002

Testosterone acts as a coronary vasodilator by a calcium antagonistic action.

T acts as a vasodilator in vitro and in vivo. Supplemental T therapy in humans with angina improves symptoms and reduces objective measures of ischemia. In left anterior descending coronary arteries taken from adult male Wistar rats, T abolishes 100+/-4.2% of calcium-dependent contraction induced by potassium chloride, 82.3+/-6.1% of the mostly calcium-dependent contraction induced by prostaglandin-F-2-alpha, but only 45.3+/-3.4% of the contraction induced by phorbol-12,13-dibutyrate (PDBu) in the presence of extracellular calcium, and 54.5+/-4.5% of the contraction induced by PDBu in the absence of extracellular calcium. These findings suggest that T is primarily inhibiting the calcium-dependent elements of vascular contraction.

Animals↗
PubMed2001

Novel platelet membrane glycoprotein VI dimorphism is a risk factor for myocardial infarction.

BACKGROUND: Glycoprotein (GP) VI plays a crucial role in platelet activation and aggregation. We investigated whether polymorphic variation at the GP VI locus confers an increased risk of myocardial infarction (MI). METHODS AND RESULTS: Coding and 5' and 3' non-coding regions of the GP VI gene were analyzed by polymerase chain reaction and conformation sensitive gel electrophoresis in 21 healthy subjects. Ten dimorphisms, 5 of which predicted amino acid substitutions (T13254C, A19871G, A21908G, A22630T, C22644A), were identified. Two core haplotypes involving 7 dimorphisms (C10781A and G10873A and all those predicting amino acid substitutions) were apparent. The contribution of the T13254C dimorphism, which predicted the substitution of serine 219 by proline, to risk of MI was assessed in 525 patients with acute MI and 474 controls, all aged <75 years. The allelic odds ratio (OR) for MI associated with the 13254C allele was 1.16 (95% CI, 0.91 to 1.46; P=0.23). Compared with corresponding control subgroups, the 13254CC genotype was more common among cases who were female (OR, 4.52; 95% CI, 1.23 to 16.64; P=0.029), nonsmokers (OR, 2.50; 95% CI, 0.98 to 6.38; P=0.048), aged >/=60 years (OR, 6.48; 95% CI, 1.47 to 28.45; P=0.009) or carried the beta-fibrinogen -148T allele associated with increased fibrinogen levels (OR, 10.49; 95% CI, 1.32 to 83.42; P=0.02). In logistic regression analysis that took other cardiovascular risk factors into account, the interactions of GP VI genotype with age (P=0.005) and beta-fibrinogen genotype (P=0.035) remained significant. CONCLUSIONS: The GP VI 13254CC genotype increases the risk of MI, particularly in older individuals, and the interaction of the GP VI 13254C allele with other candidate risk alleles may accentuate this risk.

Aged↗
PubMed2001

Analysis of the postulated interaction between the angiotensin II sub-type 1 receptor gene A1166C polymorphism and the insertion/deletion polymorphism of the angiotensin converting enzyme gene on risk of myocardial infarction.

A synergistic interaction between the insertion/deletion (I/D) polymorphism within the angiotensin-converting enzyme (ACE) gene and an A/C transversion at nucleotide position 1166 within the angiotensin II sub-type 1 receptor (AT1R) gene on risk of myocardial infarction has been reported. The risk associated with the ACE DD genotype increased with the number of AT1R C alleles present. To investigate this further, ACE I/D and AT1R A1166C genotypes were determined in 541 cases recruited at the time of infarction and 507 population-based controls. There was no difference in either the genotype distribution or allele frequencies between cases and controls for either the ACE polymorphism (P=0.48 and 0.35 respectively) or the AT1R polymorphism (P=0.35 and 0.21 respectively). Odds ratios for risk of MI associated with the ACE DD and AT1R CC genotypes were 1.09 (95% CI, 0.82-1.45) and 1.06 (0.67-1.68) respectively. 3.1% of cases versus 3.6% of controls were homozygous for both the D and C alleles (P=0.71). There was no increase in risk associated with the DD genotype in the presence of either one or two AT1R C alleles in the whole cohorts (OR 0.99, 95% CI 0.65-1.51 and 0.76, 95% CI 0.30-1.88, respectively) nor in sub-groups defined by specific risk factors. In conclusion, no evidence was found to support any interaction between the ACE gene I/D polymorphism and the ATIR gene A1166C transversion in determining the risk of myocardial infarction in the population studied.

Aged↗
PubMed2001

The -1185 A/G and -1051 G/A dimorphisms in the von Willebrand factor gene promoter and risk of myocardial infarction.

Elevated plasma von Willebrand factor (VWF) levels are associated with coronary artery disease, although the precise mechanism for this is unclear. Recently, four linked dimorphisms in the VWF gene promoter were demonstrated to influence plasma VWF level. We conducted a case-control study of 525 acute myocardial infarction (MI) cases and 451 control subjects, all aged < or = 75 years, to assess the potential contribution of two of these dimorphisms (-1185 G/A and -1051 A/G) to the risk of MI. The frequency of the -1185A/-1051G haplotype, associated with elevated VWF levels, was similar in the case and control groups, yielding a haplotypic odds ratio for MI of 0.93 (95% CI 0.77, 1.12, P = 0.43), and there was no significant association between the -1185A/-1051G haplotype and the risk of MI in any subgroup analysed. We therefore conclude that possession of the -1185A/-1051G haplotype does not confer an increased risk for MI.

Aged↗