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Biomedical subjects

A S Holmes

Publications and source records attributed to A S Holmes.

7 recordsLinked to original sources
PubMed2001

Stable angina and acute coronary syndromes are associated with nitric oxide resistance in platelets.

OBJECTIVES: The study examined possible clinical determinants of platelet resistance to nitric oxide (NO) donors in patients with stable angina pectoris (SAP) and acute coronary syndromes (ACS), relative to nonischemic patients and normal subjects. BACKGROUND: We have shown previously that platelets from patients with SAP are resistant to the antiaggregating effects of nitroglycerin (NTG) and sodium nitroprusside (SNP). METHODS: Extent of adenosine diphosphate (1 micromol/liter)-induced platelet aggregation (impedance aggregometry in whole blood) and inhibition of aggregation by NTG (100 micromol/liter) and SNP (10 micromol/liter) were compared in normal subjects (n = 43), nonischemic patients (those with chest pain but no fixed coronary disease, (n = 35) and patients with SAP (n = 82) or ACS (n = 153). Association of NO resistance with coronary risk factors, coronary artery disease (CAD), intensity of angina and current medication was examined by univariate and multivariate analyses. RESULTS: In patients with SAP and ACS as distinct from nonischemic patients and normal subjects, platelet aggregability was increased (both p < 0.01), and inhibition of aggregation by NTG and SNP was decreased (both p < 0.01). Multivariate analysis revealed that NO resistance occurred significantly more frequently with ACS than with SAP (odds ratio [OR] 2.3:1), and was less common among patients treated with perhexiline (OR 0.3:1) or statins (OR 0.45:1). Therapy with other antianginal drugs, extent of CAD, intensity of angina and coronary risk factors were not associated with variability in platelet responsiveness to NO donor. CONCLUSIONS: Patients with symptomatic ischemic heart disease, especially ACS, exhibit increased platelet aggregability and decreased platelet responsiveness to the antiaggregatory effects of NO donors. The extent of NO resistance in platelets is not correlated with coronary risk factors. Pharmacotherapy with perhexiline and/or statins may improve platelet responsiveness to NO.

Acute Disease↗
PubMed1999

Nitrate resistance in platelets from patients with stable angina pectoris.

BACKGROUND: Hemodynamic resistance to nitrates has been previously documented in congestive heart failure. In patients with stable angina pectoris (SAP), we have observed a similar phenomenon: decreased platelet response to disaggregating effects of nitroglycerin (NTG) and sodium nitroprusside (SNP). METHODS AND RESULTS: In blood samples from normal subjects (n=32) and patients with SAP (n=56), we studied effects of NO donors (NTG and SNP) on ADP-induced platelet aggregation and on intraplatelet cGMP. NTG and SNP inhibited platelet aggregation in patients to lesser extents than in normal subjects (P<0.01). The cGMP-elevating efficacy of NTG and SNP was diminished in platelets from patients in comparison with those from normals (P<0.001). Inhibition of the anti-aggregatory effects of NTG and SNP by ODQ, a selective inhibitor of NO-stimulated guanylate cyclase, was significantly less pronounced in patients than in normal subjects. Content of O2- was higher in blood samples from patients than in those from normal subjects (P<0. 01). In blood samples from patients with SAP, but not in normal subjects, the O2- scavenger superoxide dismutase (combined with catalase) suppressed platelet aggregation (P<0.01) and increased the extent of anti-aggregatory effect of SNP (P<0.01). CONCLUSIONS: In patients with SAP, platelets are less responsive to the anti-aggregating and cGMP-stimulating effects of NO donors; this may reflect both reduction in guanylate cyclase sensitivity to NO and inactivation of the released NO by O2-. The implied impairment of anti-platelet efficacy of endogenous NO (in the form of EDRF) may contribute to platelet hyperaggregability associated with angina pectoris.

Adenosine Diphosphate↗
PubMed1993

Fluorescence quenching by metal ions in lipid bilayers.

Fluorescence quenching of perylene by Co2+ and Ni2+ ions has been investigated both below and above the phase transition temperature in small unilamellar DPPC vesicles. Classic Förster type energy transfer was observed for perylene quenched by Co2+ ions below the phase transition when the effects of donor-donor energy transfer are taken into account. In the liquid crystalline phase a simple diffusion theory incorporating energy transfer was found to model the system well. For quenching by Ni2+ ions both above and below the phase transition temperature in lipid bilayers and in glycerol the data did not follow classic Förster type energy transfer but indicated that an additional quenching mechanism was present. A mechanism other than Förster behaviour was also observed for the quenching by Cr3+ ions in glycerol.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1986

Spontaneous regression of testicular seminoma: case report.

A 33-year-old man had a 1-year history of a painless testicular mass and a 2-month history of an enlarging left supraclavicular mass. Biopsy of the supraclavicular mass showed classical seminoma. Massive abdominal lymphadenopathy was demonstrated by computerized tomography. Radical orchiectomy was performed and examination of the specimen showed only fibrous scar tissue consistent with regression of a primary tumor in the testis. While complete regression of a primary testicular tumor with progressive growth of metastases is well recognized in cases of nonseminomatous germ cell tumors, this phenomenon is reported rarely with seminoma.

Adult↗