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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

As shown by large-scale clinical trials, the antihypertensive effectiveness of diuretics has been associated with a dramatic decrease in the incidence of stroke. This decrease, however, has not been accompanied by a similar reduction in atherosclerotic complications of hypertension, perhaps because other risk factors are important contributors to cardiovascular disease. In particular, a pathophysiologic relationship appears to exist between high blood pressure, left ventricular hypertrophy, diabetes and dyslipidemia. Thus, metabolically neutral antihypertensive agents such as calcium antagonists, which have no adverse effects on serum lipids and insulin sensitivity and can reduce left ventricular mass, are particularly suitable for the treatment of hypertension and attendant cardiovascular complications.
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PMID:Calcium antagonists for the treatment of systemic hypertension. 157 72

Hypertension is a major risk factor for cardiovascular diseases, including coronary artery disease (CAD), stroke, left ventricular hypertrophy (LVH), congestive heart failure, peripheral vascular disease, renal failure, and aortic aneurysms. It is also a potent promoter of atherosclerosis. Observational studies have shown a linear relationship between a wide range of blood pressures and the risk for CAD and stroke. Clinical trials have indicated that hypertension reduction leads to the predicted reduction in stroke incidence, but that CAD incidence is affected to a lesser extent than predicted. The modest effect of traditional antihypertensive drugs on CAD may be due to several factors, including failure to reverse well-established coronary atherosclerosis, particularly if multiple risk factors are not reduced as well. Metabolic side effects of antihypertensive drugs or excessive lowering of blood pressure leading to inadequate myocardial perfusion, especially in patients with increased left ventricular (LV) mass, also may play important roles. Hypertension is a major cause of renal failure, particularly in black males, but control of the hypertension does not necessarily prevent deterioration of renal function. Increased glomerular pressure is thought to play a causative role in the development of renal failure in hypertensive and diabetic patients. Antihypertensive drugs may have a direct effect on the arterial wall, which may be independent of their antihypertensive action. Beta-adrenergic blockers, calcium antagonists, and angiotensin-converting enzyme (ACE) inhibitors inhibit the development of vascular lesions in response to hypercholesterolemia or to iatrogenic balloon injury, but the clinical importance of these observations remains to be determined.
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PMID:Vascular effects of systemic hypertension. 157 75

Age-related changes (e.g., decrease in plasma renin activity and total body potassium, increase in plasma catecholamines, volume depletion) need to be taken into account when selecting an antihypertensive agent for the elderly patient. A number of large scale clinical trials (e.g., Systolic Hypertension in the Elderly Program, Veterans Administration Cooperative Study, European Working Party on High Blood Pressure in the Elderly) have demonstrated that antihypertensive therapy with diuretics substantially reduced cardiovascular mortality and stroke incidence. However, since diuretics, even potassium-sparing agents, may induce hypokalemia, newer antihypertensive agents (angiotensin-converting enzyme [ACE] inhibitors and calcium antagonists) may also be appropriate as first-line monotherapy for this patient population. ACE inhibitors are effective antihypertensive agents and are associated with a lower rate of adverse effects than diuretics, beta blockers, and centrally acting agents. Nevertheless, periodic monitoring of serum potassium, creatinine levels, and renal function is advisable. An important feature of calcium antagonists is that they lower blood pressure with no negative effect on serum lipids or glucose metabolism. Typically, they have few side effects, peripheral edema being the most commonly reported. A recent double-blind randomized study comparing a new sustained release nifedipine formulation and the ACE inhibitor lisinopril found the 2 drugs equivalent in efficacy with no differences in the rate of adverse events.
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PMID:Hypertension in the elderly with a special focus on treatment with angiotensin-converting enzyme inhibitors and calcium antagonists. 157 76

Three indexes developed originally to assess left ventricular contractile performance were applied instead to the right ventricle (RV) in 11 conscious dogs: the relation between stroke work and end-diastolic volume (EDV), termed the preload recruitable stroke work (PRSW) relation; the end-systolic pressure-volume (ESPV) relation; and the maximum dP/dt (dP/dtmax)-EDV relation. The reproducibility, inotropic sensitivity, chronotropic sensitivity, and afterload sensitivity of these RV relations were compared. RV volume was determined with an ellipsoidal shell subtraction model from orthogonal dimensions measured by sonomicrometry. RV transmural pressure was measured with micromanometers. After autonomic blockade, preload was varied by repeated, transient vena caval occlusions before and during partial occlusion of the main pulmonary artery, after release of the pulmonary arterial occlusion, after calcium infusion, and over a range of heart rates induced by atrial pacing. The slope and volume-axis intercept of the PRSW relation were more reproducible (SD/mean, 7.8 +/- 3.3% and 6.2 +/- 4.1%, respectively) than the slope and volume-axis intercept of the ESPV relation (10.1 +/- 6.7% and 23.0 +/- 31.3%, both p less than 0.05) or the slope and volume-axis intercept of the dP/dtmax-EDV relation (43.4 +/- 70.4% and 153.8 +/- 184.6%, both p less than 0.05). The slope of the PRSW relation increased 32 +/- 17% (p less than 0.05) after calcium infusion, but the volume-axis intercept did not change significantly. In contrast, the slopes of the ESPV and dP/dtmax-EDV relations did not change significantly after calcium infusion, but the volume-axis intercepts decreased significantly (both p less than 0.05). Despite a 71 +/- 26% increase in mean RV ejection pressure during partial occlusion of the main pulmonary artery, the slopes and volume-axis intercepts of both the PRSW and dP/dtmax-EDV relations did not change significantly, but the slope of the ESPV relation increased 45 +/- 22% (p less than 0.05) without significant change in the volume-axis intercept. None of the relations demonstrated significant chronotropic sensitivity. The PRSW relation is the preferred index of RV contractile performance because 1) it is the most reproducible, 2) its slope alone sensitively detects changes in contractile state, and 3) unlike the ESPV relation, it is relatively insensitive to afterload.
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PMID:Right ventricular preload recruitable stroke work, end-systolic pressure-volume, and dP/dtmax-end-diastolic volume relations compared as indexes of right ventricular contractile performance in conscious dogs. 157 38

The possibility of a super-coiling of the thin filament is studied. The bimetallic super-coiling might contribute to the power-stroke. The calculation of the axial shortening of the proposed super-coiling leads to a very surprising geometric fitting: the maximal axial shortening of the super-coiling, without any loop, of the thin filament segment (38.5 nm) is equal to the axial repeat of cross-bridges (14 nm). According to the present model, the sarcomere shortening is caused by the axial shortening of the super-coiled actin filament. The top-view of the super-coiled segment shows a dual half-circle form. There are experimental evidences for such a type of formation in electron micrographs. According to this model, the widely accepted sterically hidrance model on association of actin and myosin can be neglected. One of the main roles of calcium is to make the thin filament segment flexible enough for the association.
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PMID:Contraction due to bimetallic, short-lived super-coiling in the helical, double stranded filaments of striated muscle. 159 59

It has become increasingly clear that a stroke lesion usually consists of a densely ischemic focus and of perifocal areas with better upheld flow rates. At least in rats and cats, some of these perifocal ("penumbral") areas subsequently become recruited in the infarction process. The mechanisms may involve an aberrant cellular calcium metabolism and enhanced production of free radicals. In general, though, the metabolic perturbation in the penumbra requires better characterization. The objective of this article was to define flow distribution in a rat model of reversible middle cerebral artery (MCA) occlusion, so as to allow delineation of the metabolic aberrations responsible for the subsequent infarction. We modified the intraluminal filament occlusion model recently developed by Koizumi et al. (1986), and described in more detail by Nagasawa and Kogure (1989), adopting it for use in both spontaneously breathing and artificially ventilated rats. Successful occlusion of the MCA (achieved in about 9/10 rats) was judged by unilateral EEG depression in ventilated rats, and neurological deficits, such as circling, in spontaneously breathing ones. CBF in the ipsilateral hemisphere was reduced to nearly constant values after 20, 60, and 120 min of occlusion, flow rates in the focus being about 10% and in the perifocal ipsilateral areas about 15-20% of control (contralateral side). When the filament was left in place (permanent occlusion) 2,3,5-triphenyl tetrazolium chloride (TTC) staining and histopathology after 24 h showed a massive infarct on the occluded side, extending from caudoputamen and overlaying cortex to the occipital striate cortex. Animals recirculated after 60 min of MCA occlusion, and allowed to survive 7 days for histopathology, showed infarction of the caudoputamen (lateral part or whole nucleus) in 5/6 animals and selective neuronal necrosis in one animal. The neocortex showed either infarcts, selective neuronal necrosis, or no damage. There was some overlap between neocortical areas which were infarcted and those which were salvaged by reperfusion. In general, though, both the CBF data and the recovery studies with a histopathological endpoint define large parts of the neocortex as perifocal (penumbral) areas which lend themselves to studies of metabolic events leading to infarction.
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PMID:Ischemic penumbra in a model of reversible middle cerebral artery occlusion in the rat. 160 Nov 3

The Cardiovascular Health Study (CHS), a cohort study of risk factors for coronary heart disease and stroke, recruited 5201 community-dwelling adults aged 65 years or older. To assess the prevalence of medication use at baseline, we used the method of medication inventory and transcribed information about drug names and doses from prescription bottles. Using a specially-written computer program, persons without a knowledge of drug nomenclature coded 10,511 (89%) of the 11,846 medicines entered. We compared the results of the medication inventory and answers to questions on specific medications for reliability and validity. The use of beta-blockers and beta-agonists assessed by the method of medication inventory, but not by the method of directed recall, was associated with a significant effect on mean heart rate. Among 5197 participants with medication data, 76.1% were taking at least one medicine, and the mean number of drugs per person was 2.28. Among those with a reported history of high blood pressure, participants with cardiovascular disease (CVD) were more likely to be treated, and they were more likely to be taking beta-blockers and calcium-channel blockers than those without CVD. Daily aspirin use was also more common among those with CVD (30.5% of women and 43.2% of men) than among those without CVD (14.0% of women and 14.0% of men). The prevalence of post-menopausal estrogen use differed significantly among the four clinical centers (range = 5.5%-22.5% of women). We conclude that this method of assessing medications was easy to use and provided estimates of exposure to drugs that may affect risk of cardiovascular disease.
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PMID:Assessing the use of medications in the elderly: methods and initial experience in the Cardiovascular Health Study. The Cardiovascular Health Study Collaborative Research Group. 160 9

The search for effective therapy of acute stroke, centres on the two strategies of restoring blood flow before ischaemia causes irreversible infarction, and moderation of the biochemical changes in ischaemic tissue that cause neuronal death. This review concentrates on the role of lactacidosis, calcium ions, free radicals, and excitatory neurotransmitters in the pathogenesis of neuronal death, and on the therapeutic possibilities in acute stroke emerging from studies in animal models.
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PMID:Protection against ischaemia: the basis of acute stroke therapy. 162 35

Although platelets constitute the major component of a thrombus, its role in determining the clinical severity of thrombotic stroke is unknown. Therefore, we investigated the relationship between platelet ionized calcium ([Ca2+i]), a measure of platelet activity and presumably proneness to thrombosis, and clinical stroke severity in 45 consecutively studied acute ischemic stroke patients. Even though there was no correlation between the clinical neurological scores and the levels of baseline and activated platelet [Ca2+i], stroke was less severe in patients who had been taking aspirin at the time of stroke onset. These results raise several important questions: (a) is the extent of platelet activation a reflection of thrombus volume, (b) does the clinical severity of neurological deficit reflect the causative thrombus volume, and (c) whether the beneficial effect of aspirin in stroke prophylaxis is through its inhibition of platelets alone.
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PMID:Platelet activity and stroke severity. 162 46

The effect of fish oil on potassium efflux and basal tension in aortas from stroke prone spontaneously hypertensive rats (SHRSP) was evaluated. Four-week-old male Wistar-Kyoto rats (WKY) and SHRSP were divided into two groups: one received a 5% corn oil diet; the other a 5% menhaden oil diet. After 15 weeks, mean systolic blood pressure (mm Hg) was reduced in SHRSP-fish (202 +/- 5) compared to SHRSP-corn (227 +/- 4). Systolic pressure of WKY-fish (146 +/- 3) was not different from WKY-corn (151 +/- 4). Potassium efflux was evaluated with the isotope 86Rb. Basal 86Rb efflux from aorta of SHRSP-corn was evaluated compared to WKY-corn. Diltiazem or sodium nitroprusside decreased 86Rb efflux and basal tension in SHRSP. Basal 86Rb efflux, tension, and the magnitude of this diltiazem- or nitroprusside-induced inhibition were decreased in SHRSP-fish. At maximal diltiazem or nitroprusside concentration, 86Rb efflux from both SHRSP dietary groups was similar but still greater than control aorta. The IC50 values for diltiazem or nitroprusside effects on 86Rb efflux and tension were not altered by diet in SHRSP. Qualitatively similar changes in basal 86Rb efflux and tension were noted in WKY-fish compared to WKY-corn. These experiments demonstrate that dietary fish oil supplementation decreased calcium-sensitive 86Rb efflux and basal tension in vascular smooth muscle and suggest that these changes may contribute to the concomitant antihypertensive effect of dietary fish oil in SHRSP.
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PMID:Effects of dietary fish oil on Rb+ efflux from aorta of stroke prone spontaneously hypertensive rats. 163 20


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