Biomedical subjects

Graham Jackson

Publications and source records attributed to Graham Jackson.

At least 91 records · Page 5Linked to original sources

PubMed2004

Treatment of erectile dysfunction in patients with cardiovascular disease : guide to drug selection.

Erectile dysfunction (ED) is common in cardiac patients and shares the same risk factors--smoking, hypertension, hyperlipidaemia and diabetes mellitus. Sexual activity is not unduly stressful to the heart and, providing patients are properly assessed using established guidelines, sexual intercourse can be enjoyed without increased risk. The treatment of ED in patients with cardiovascular disease has been transformed by the introduction of the oral phosphodiesterase type 5 inhibitors, the first of which was sildenafil. Success in restoring erectile function is possible in up to 80% of patients (depending on the aetiology) with minimal adverse effects. A synergistic hypotensive effect with nitrates, and almost certainly nicorandil, is the only major contraindication. ED in asymptomatic patients may be a marker of silent vascular disease or increased vascular risk factors and should alert the physician to the need for cardiac risk screening. ED is common in patients with cardiovascular disease and should be routinely enquired about. ED is a distressing condition for the man and his partner, and severely impairs quality of life. Patients with cardiovascular disease and patients with diabetes represent the largest group of patients with ED, the majority of whom benefit from the drug therapies currently available. Addressing ED in patients with cardiovascular disease can lead to a substantial improvement in quality of life and success is not difficult to achieve.

3',5'-Cyclic-GMP Phosphodiesterases↗

PubMed2003

Time course of the interaction between tadalafil and nitrates.

OBJECTIVES: This study was designed to determine the time course of nitrate interaction with tadalafil, a phosphodiesterase 5 (PDE5) inhibitor with a half-life (t(1/2)) of 17.5 h. BACKGROUND: The PDE5 inhibitors augment the blood pressure (BP)-lowering effects of nitrates, yet the time course of this interaction is unclear. Recent guidelines from the American College of Cardiology/American Heart Association recommend that nitrates be withheld for 24 h after taking sildenafil (t(1/2) = 4 h). METHODS: Male subjects (n = 150) received seven consecutive daily doses of placebo or tadalafil (20 mg). On day 7 and beyond, subjects received repeated doses of sublingual nitroglycerin (0.4 mg) after the last dose of placebo or tadalafil. After a 10- to 21-day washout period, subjects crossed over to either placebo or tadalafil, and nitrate dosing was repeated. RESULTS: In response to nitroglycerin at 4, 8, and 24 h, standing systolic BP fell below 85 mm Hg in more subjects on tadalafil compared with placebo (p < 0.05), with no difference in the response to nitroglycerin at 48, 72, and 96 h (p > 0.2). Similar observations were made for standing diastolic BP <45 mm Hg, decrease in systolic BP >30 mm Hg, and decrease in diastolic BP >20 mm Hg. Nitroglycerin also evoked greater mean maximal decreases in standing systolic BP at 8 and 24 h after taking tadalafil versus placebo (p < 0.02), with no significant difference at 48, 72, or 96 h (p > 0.49). CONCLUSIONS: The hemodynamic interaction between tadalafil and sublingual nitroglycerin lasted 24 h, but was not seen at 48 h and beyond. Similar to other PDE5 inhibitors, tadalafil should not be administered in combination with organic nitrates.

Adult↗

PubMed2003

Aspirin modifies nitric oxide synthase activity in platelets: effects of acute versus chronic aspirin treatment.

OBJECTIVE: We examined the effects of aspirin on basal and beta-adrenoceptor (beta-AR)-mediated nitric oxide synthase (NOS) activity in normal platelets. METHODS: NOS activity was determined from the conversion of L-[3H]arginine to L-[3H]citrulline, both basally and following beta-AR stimulation, in platelets from healthy human subjects following both short- and long-term aspirin administration. RESULTS: Basal L-[3H]citrulline increased following aspirin 800 mg administered intravenously in vivo, from 0.31+/-0.12 to 0.76+/-0.14 pmol/10(8) platelets (P<0.01). Isoproterenol at 1 micromol/l increased platelet NOS activity before but not following intravenous aspirin. After short-term in vitro treatment with aspirin 10 micromol/l, 400 micromol/l or 4 mmol/l, basal platelet L-[3H]citrulline increased similarly, an effect not seen with indomethacin 100 micromol/l or ibuprofen 10 micromol/l. Platelet NOS activity was not increased by albuterol 1 micromol/l, in the presence of indomethacin, ibuprofen or aspirin in vitro. By contrast, oral aspirin 75 mg daily for 14 days did not affect basal platelet NOS activity, but abolished beta-adrenergic NOS activation. CONCLUSIONS: Aspirin activates basal platelet NOS acutely, but not chronically, through a mechanism independent of cyclooxygenase (COX) inhibition. By contrast, both short- and long-term aspirin treatment inhibit platelet beta-adrenergic NOS activation by a COX-dependent mechanism. This indicates that aspirin exerts divergent effects on basal and beta-AR-stimulated platelet NOS activity, which are likely to be of clinical relevance.

Adrenergic beta-Agonists↗

PubMed2003

Regional heterogeneity of cellular prion protein isoforms in the mouse brain.

Prion diseases are a group of invariably fatal neurodegenerative disorders that include Creutzfeldt-Jakob disease in humans, scrapie in sheep and goats, and bovine spongiform encephalopathy in cattle. The infectious agent or prion is largely composed of an abnormal isoform (PrPSc) of a host encoded normal cellular protein (PrPc). The conversion of PrPc to PrPSc is a dynamic process and, for reasons that are not clear, the distribution of spongiform change and PrPSc deposition varies among prion strains. An obvious explanation for this would be that the transformation efficiency in any given brain region depends on favourable interactions between conformations of PrPc and the prion strain being propagated within it. However, identification of specific PrPc conformations has until now been hampered by a lack of suitable panels of antibodies that discriminate PrPc subspecies under native conditions. In this study, we show that monoclonal antibodies raised against recombinant human prion protein folded into alpha or beta conformations exhibit striking heterogeneity in their specificity for truncations and glycoforms of mouse brain PrPc. We then show that some of these PrPc isoforms are expressed differentially in certain mouse brain regions. This suggests that variation in the expression of PrPc conformations in different brain regions may dictate the pattern of PrPSc deposition and vacuolation, characteristic for different prion strains.

Animals↗

PubMed2003

Changes in the human mitochondrial genome after treatment of malignant disease.

Mitochondrial DNA (mtDNA) is the only extrachromosomal DNA in human cells. The mitochondrial genome encodes essential information for the synthesis of the mitochondrial respiratory chain. Inherited defects of this genome are an important cause of human disease. In addition, the mitochondrial genome seems to be particularly prone to DNA damage and acquired mutations may have a role in ageing, cancer and neurodegeneration. We wished to determine if radiotherapy and chemotherapy used in the treatment of cancer could induce changes in the mitochondrial genome. Such changes would be an important genetic marker of DNA damage and may explain some of the adverse effects of treatment. We studied samples from patients who had received radiotherapy and chemotherapy for point mutations within the mtDNA control region, and for large-scale deletions. In blood samples from patients, we found a significantly increased number of point mutations compared to the control subjects. In muscle biopsies from 7 of 8 patients whom had received whole body irradiation as well as chemotherapy, the level of a specific mtDNA deletion was significantly greater than in control subjects. Our studies have shown that in patients who have been treated for cancer there is an increased level of mtDNA damage.

Adolescent↗

PubMed2003