Hypoxia is a potent coronary-vasodilating signal; its mechanisms are still controversial. We have assessed the possible role of nitric oxide (NO) in hypoxic coronary vasodilatation (HCVD) in isolated guinea pig hearts perfused at constant pressure. HCVD was elicited by a 1-minute 100% N2 exposure; coronary flow doubled within 1 minute of hypoxia (early phase) and returned to baseline within 40 seconds after reoxygenation (late phase). The early phase of HCVD was associated with a rapid approximately eightfold increase in cGMP overflow, an indication of NO release. The specific NO synthase inhibitor N omega-methyl-L-arginine (NMA, 0.1-1 mM) antagonized HCVD and the associated increase in cGMP spillover (maximum inhibition, approximately 65%); excess arginine (1.2 mM) prevented both effects. The late phase of HCVD was associated with an increase in adenosine overflow and was attenuated by the adenosine receptor antagonist BW A1433 (1 microM; maximum inhibition, approximately 45%). Indomethacin (10 microM) inhibited HCVD in spontaneously beating hearts by approximately 35% but had no effect in hearts paced at faster rates. NMA and BW A1433 were more effective in combination than alone (maximum inhibition, approximately 72%). However, irrespective of the concentrations used, there was no synergism among the anti-HCVD effects of NMA, BW A1433, and indomethacin, nor was HCVD completely inhibited by the antagonists, whether alone or in combination. Our findings indicate that NO is an important mediator of the early phase of HCVD, whereas additional mechanisms and/or factors, including adenosine and vasodilatatory prostaglandins, contribute to the late phase.
This study was designed to measure the magnitude and duration of inhibition of platelet aggregation following doses of aspirin or ibuprofen alone or taken in combination in a group of healthy volunteers. Ten normal volunteer subjects underwent 3 randomized treatment sessions: aspirin 325 mg alone, ibuprofen 400 mg alone, and ibuprofen 400 mg, followed by dosing with aspirin 325 mg 2 hours thereafter. In addition, a confirmatory study was performed in patients. Over 27 months, a cohort of patients treated with aspirin for secondary stroke prophylaxis while concomitantly taking a nonsteroidal anti-inflammatory drug (NSAID) was identified. A significant reduction was found in both the magnitude and duration of aspirin's inhibitory effect on platelet aggregation when ibuprofen was given prior to aspirin administration in normal volunteer subjects. During a 27-month period, a cohort of 28 patients took regular daily doses of ibuprofen or naproxen. Of these 28 patients, 18 returned for follow-up testing in the absence of this pharmacodynamic interaction. None of these 18 patients demonstrated inhibition of platelet aggregation while on both NSAID and aspirin; however, all showed inhibition of aggregation following discontinuation of the NSAID. Notably, 13 of these 18 patients (72%) had experienced a recurrent ischemic episode while taking aspirin and NSAIDs concomitantly. These data suggest that ibuprofen prevents the irreversible inhibition of platelet aggregation produced by aspirin needed for secondary stroke prophylaxis, and this interaction can have clinical consequences for patients taking aspirin.
The counseling center's top three issues pursued for counseling are consistent with the research of mental health issues on college campuses. Counseling services at a university are an integral part of the institution, as evidenced by statistics from undergraduate and graduate college settings.
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