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

Isolated systolic hypertension (ISH) is generally defined as a systolic pressure of 160 mmHg or more, with a diastolic pressure cut-off point below 95 mmHg in some studies and 90 mmHg in others. Its prevalence and incidence vary from 3 to 30% depending on the definition applied, methodology of measurement, as well as the population and the age and sex of the patients. Mechanisms that could lead to the development of isolated systolic hypertension are discussed, especially the role of atherosclerosis and sodium intake. Comparing results from different countries, the Intersalt study showed that the age related rise in systolic pressure was positively related to the mean sodium excretion in that country. A post-hoc analysis of data from 4 Belgian groups could not show such a correlation within our country. The risks of systolic hypertension on mortality and morbidity in the elderly are considered. The need for further studies to quantify the risk and to establish the effect of treatment is emphasized. Three such studies in patients above the age of 60 years with ISH were started. The studies are double-blind, placebo-controlled trials and the main purpose is to examine the influence of treatment on morbidity, mortality, and general well-being. In the American SHEP study the patients of the actively treated group received a diuretic and possibly a beta-blocker or reserpine. The results indicate a significant reduction in non fatal stroke, heart failure and myocardial infarction without a significant reduction in fatal stroke, fatal myocardial infarction, cardiovascular or all cause mortality. Studies in other continents are still in progress, such as the Syst-Chin in China and the Syst-Eur trial in Europe. They may indicate whether the results obtained in the U.S.A. can be extrapolated to other continents and whether the use of other drugs without metabolic disturbances, such as calcium entry blockers and angiotensin converting enzyme inhibitors, produce a similar reduction in events. Additional studies are needed to establish the effect of reducing salt intake in younger age groups on the prevalence of ISH and of the related morbidity and mortality.
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PMID:[Isolated systolic hypertension in persons older than 60]. 141 81

The effectiveness of the calcium antagonist nicardipine in protecting the ischemic myocardium was evaluated using the hemodynamic recovery of isolated working rat hearts subjected to hyperkalemic cardiac arrest followed by ischemia at 37.5 degrees C and 10 degrees C. Rat hearts (n = 51) received 20 mL of cardioplegia and were subjected to 27 minutes of ischemia at 37.5 degrees C. Group A (control) did not receive nicardipine. Groups B through F received nicardipine in the cardioplegia with total doses ranging from 2 micrograms to 6 micrograms. Group A had 46% survival of ischemia, whereas groups C (3 micrograms) and D (4 micrograms) had survival rates of 88% and 100%, respectively (p less than 0.05). The recovery of aortic flow after ischemia was 35% in group A, compared with 76% in group B (2 micrograms) and 81% in group D (p less than 0.05). Group A had 49% postischemic recovery of cardiac output, whereas groups B and D had 82% and 85% recovery (p less than 0.05). The postischemic recovery of stroke volume was 48% in group A compared with 84% in group B, 87% in group D, and 73% in group E (5 micrograms) (p less than 0.05). Additional rats were exposed to 210 minutes of ischemia (n = 41) or 240 minutes of ischemia (n = 56) at 10 degrees C. Control groups did not receive nicardipine, whereas treatment groups received nicardipine in the cardioplegia with total doses ranging from 1.4 micrograms to 6.4 micrograms. There were no significant differences in the survival of ischemia or the recovery of function after ischemia at 10 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nicardipine: myocardial protection in isolated working hearts. 141 29

To determine whether ephedrine or CaCl2 improves hemodynamics in cardiac surgery patients emerging from cardiopulmonary bypass, three sequential doses of either CaCl2 (200 mg/dose; n = 12), ephedrine (5 mg/dose; n = 12), or placebo (n = 12) were administered in a prospective, randomized, double-blind fashion. Thermodilution volumetric catheters were used to calculate right ventricular (RV) volumes and ejection fraction. The first dose of ephedrine improved RV stroke volume from 57 +/- 3 to 63 +/- 4 mL/beat (P < 0.05) and ejection fraction from 44 +/- 2% to 49 +/- 2% (P < 0.05). Subsequent doses maintained this improvement but without further change. In contrast, placebo and CaCl2 had minimal effects on RV end-systolic volume, stroke volume, and ejection fraction. After the third injection of ephedrine, mean arterial pressure had significantly increased from 78 +/- 2 to 93 +/- 4 mmHg (P < 0.05) in contrast to insignificant increments with placebo and CaCl2. Serum ionized calcium increased by 6% to 8% after each CaCl2 bolus but remained stable in the ephedrine and placebo groups. CaCl2 failed to improve RV performance in mildly hypocalcemic patients during separation from cardiopulmonary bypass. In patients with normal preoperative ventricular function, ephedrine more effectively improved RV performance and arterial blood pressure than placebo or CaCl2, and is a suitable short-acting drug to assist separation from cardiopulmonary bypass.
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PMID:Is calcium or ephedrine superior to placebo for emergence from cardiopulmonary bypass? 142 Oct 63

Excessive activation of NMDA receptors is thought to mediate the calcium-dependent neurotoxicity associated with hypoxic-ischemic brain injury, trauma, epilepsy, and several neurodegenerative diseases. For this reason, various NMDA antagonists have been investigated for their therapeutic potential in these diseases, but heretofore none have proven to be both effective and safe. In the present study, memantine, an adamantane derivative similar to the antiviral drug amantadine, is shown to block the channels activated by NMDA receptor stimulation. From whole-cell and single-channel recording experiments, the mechanism of action of memantine is deduced to be open-channel block, similar to MK-801; however, unlike MK-801, memantine is well tolerated clinically. Compared to MK-801, memantine's safety may be related to its faster kinetics of action with rapid blocking and unblocking rates at low micromolar concentrations. Furthermore, at these levels memantine is an uncompetitive antagonist and should theoretically allow near-normal physiological NMDA activity throughout the brain even in the face of pathologically high focal concentrations of glutamate. These pharmacological properties confer upon memantine a therapeutic advantage against NMDA receptor-mediated neurotoxicity with few side effects compared with other organic NMDA open-channel blockers. Moreover, memantine is increasingly effective against escalating levels of glutamate, such as those observed during a stroke. Low micromolar concentrations of memantine, levels known to be tolerated by patients receiving the drug for the treatment of Parkinson's disease, prevent NMDA receptor-mediated neurotoxicity in cultures of rat cortical and retinal ganglion cell neurons; memantine also appears to be both safe and effective in a rat stroke model. These results suggest that memantine has considerable therapeutic potential for the myriad of clinical entities associated with NMDA receptor-mediated neurotoxicity.
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PMID:Open-channel block of N-methyl-D-aspartate (NMDA) responses by memantine: therapeutic advantage against NMDA receptor-mediated neurotoxicity. 143 3

The ability of digitalis compounds to counteract calcium antagonist overdose was studied in anesthetized dogs (n = 6, 13.5 +/- 0.7 kg) and isolated trabeculae from human hearts (n = 7). Digitalis caused by increasing intracellular cytosolic Ca2+ concentration through Na+/Ca(2+)-exchange across the cell membrane, was postulated to overcome the detrimental effects of excessive slow calcium-channel blockade. In anesthetized dogs, an infusion of verapamil (40 mg/30 min, i.v.) decreased mean arterial pressure from 88 +/- 6 to 66 +/- 6 mm Hg (P < 0.05), reduced systemic vascular resistance (SVR) from 3838 +/- 916 to 2200 +/- 669 dyne.s/cm5 (P < 0.05), and induced total atrio-ventricular (A-V) block in three animals. Stroke volume (SV) remained unchanged. Administration (i.v.) of NaCl (0.9%, 200 ml) and calcium gluconate (100 mg)--to increase the availability of Na+ and Ca(2+)--together with atropine (0.2 mg)--to block the parasympathetic effects of digoxin on A-V conduction--increased left ventricular contractility (15%) but had no significant effects on blood pressure, SV, or A-V block. Digoxin (0.125 mg) returned sinus rhythm in all dogs and, by increasing SVR (P < 0.05) and left ventricular contractility (P < 0.05), returned arterial pressures to baseline. Because of increased afterload, SV decreased slightly (15%) despite increased cardiac contractility. In experiments with isolated trabeculae from diseased human hearts, TA 3090 (Clentiazem) depressed contractile force and ouabain, another glycoside, restored contractile force within 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cardiac glycosides in the treatment of experimental overdose with calcium-blocking agents. 143 98

Aggregation, secretion and 47kDa protein (P47) phosphorylation by various agonists such as thrombin, ADP and ionophore A23187 were markedly reduced in platelets from stroke-prone spontaneously hypertensive rats (SHRSP) compared with those of age-matched Wistar Kyoto rat (WKY) platelets, suggesting defective functions of intracellular Ca2+ in SHRSP platelets (Tomita et al. Hypertension 1989; 14: 304-315). To clarify the mechanism of the platelet hypofunctions, saponin permeabilized platelets were prepared to compare the responses of platelets from both rats in varying concentrations of extracellular Ca2+. The leakage of lactate dehydrogenase from saponin (15 micrograms/ml)-treated platelets was approx. 5% of total activity; the degree of the leakage in both platelets did not differ. In saponin-treated platelets, extracellular Ca2+ alone did not induce either aggregation or secretion in both strains. However, in the presence of 1-oleoyl-2-acetylglycerol (10 micrograms/ml), Ca2+ dose dependently stimulated both aggregation and secretion. Under this condition, Ca2+ sensitivity of aggregation, secretion and P47 phosphorylation in SHRSP platelets were significantly reduced compared with those in WKY platelets. These results strongly suggest that intracellular Ca2+ functions are impaired in SHRSP platelets.
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PMID:Reduced functions of intracellular Ca2+ in aggregation, secretion and protein phosphorylation of permeabilized platelets from stroke-prone spontaneously hypertensive rats. 144 May 31

1. Genetic rat models of hypertension, such as spontaneously hypertensive rats (SHR) and in particular, stroke-prone SHR (SHRSP) are useful models for research on the genetic pathogenesis, gene-environment interaction and control of environmental factors for the prevention of hypertension and related cardiovascular diseases (CVD). 2. Since recent genetic analysis of hypertension in SHRSP indicated that one of the hypertensive genes related to salt-induced blood pressure (BP) rise was linked with the gene of the angiotensin-converting enzyme, gene-environment interaction is important in the humoral, neural, vascular and nutritional mechanisms of hypertension and CVD. 3. Extensive experimental studies in SHRSP by the authors have demonstrated nutritional factors counteracting directly or indirectly against the adverse effect of excess salt intake, such as K, Mg, Ca, dietary fibres, protein, some amino acids and fatty acids, etc.; they are therefore effective in preventing stroke, the typical complication of hypertension. 4. Experimental atherosclerotic models were established in SHRSP, which indicated also a gene-environment interaction in the pathogenesis of atherosclerosis at the cellular level of vascular smooth muscle cells. Excess salt intake accelerated cholesterol absorption from the intestine to induce arterial fat deposition as well as to active platelet aggregation by the mechanism of increased intracellular Ca2+ mobilization. 5. Based on such experimental findings on the hypertension and related CVD prevention, a cross-sectional multicentre epidemiological 'CVD and Alimentary Comparison' Study (WHO-CARDIAC Study) was designed to assess the relationship of biological markers of dietary factors with BP ('core' study) and major CVD mortalities ('complete' study) and has been successfully undertaken for the past 8 years in co-operation with 54 centres in 23 countries. 6. The results of 'core' study so far obtained by cross-centre simple linear regression analysis demonstrated adverse effects of body mass index and salt intake on BP in men and possible beneficial effects of Mg by within-centre multiple linear regression analysis. 7. Preliminary cross-centre simple linear regression analysis of the 'complete' study indicated a positive correlation of serum cholesterol levels and negative correlation of serum phospholipid poly-unsaturated to unsaturated fatty acid ratios and 24 h urinary taurine excretion with coronary heart diseases mortality; a positive correlation of 24 h urinary Na and Na/K ratios and a negative correlation of serum cholesterol levels with stroke mortalities was indicated. 8. These epidemiological data confirmed mostly the applicability of experimental findings to the nutritional prevention of hypertension and CVD prevention.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Gene-environment interaction in hypertension, stroke and atherosclerosis in experimental models and supportive findings from a world-wide cross-sectional epidemiological survey: a WHO-cardiac study. 144 9

Epidemiological data have revealed that the progestogen in oral contraceptives (OCs) is involved in hypertension, ischemic heart diseases, and stroke. Atherosclerotic lesions were implicated owing to the androgenic properties of progestogens. However, atherosclerosis did not develop despite reduced high density lipoprotein (HDL) and elevated low density lipoprotein (LDL), presumably because of the strong effect of ethinyl estradiol (EE) upon induction of hepatic LDL- and remnant-receptors. A series of findings indicate that vasospasms caused by the effect of progestogens are involved in arterial thromboses. In postmenopausal women, the addition of progestogens to the estrogen treatment may trigger ischemic diseases. Estrogens exert a vasodilatory effect and stabilize the vascular tonus through the responsiveness of the endothelium, neurotransmitter release, and direct blocking of calcium channels. Progestogens increase the sensitivity of arteries to vasoconstrictory compounds and reduce blood flow. In women treated with ovulation inhibitors, and EE-induced activation of the renin-angiotensin-aldosterone system was observed. Aldosterone acts vasodilatorily, while progestogens with high affinity to the aldosterone receptor may exert a strong vasoconstrictory effect. If vascular lesions are present, the vasoconstrictory action of progestogens may cause acute ischemic attacks. Therefore, the lowest effective dose of the progestogen has to be used for replacement therapy. In hysterectomized women, the extra administration of progestogens should be avoided and in women with arterial diseases they should be prescribed with discretion. Additional progestogens given for 14 days 3 months apart may suffice for the prevention of endometrial hyperplasia. Both the EE and progestogen doses in OCs should be reduced. Progestogen-dominant ovulation inhibitors should be restricted to cases with an additional indication.
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PMID:[Hormonal contraception and substitution therapy: the importance of progestogen for cardiovascular diseases]. 145

To assess the hemodynamic interactions when combining verapamil, acute changes in extracellular ionized calcium concentration [Ca2+] and enflurane (2.5%), halothane (1.2%) or isoflurane (1.6%), seven dogs were chronically instrumented to measure heart rate (HR), aortic, left atrial and left ventricular (LV) pressures, and cardiac output (CO). [Ca2+] was lowered 0.35 mmol.l-1 by citrate infusion and then increased 0.35 mmol.l-1 above control level by CaCl2 infusions. Verapamil was infused at 3 micrograms.kg-1 x min-1 (loading dose 200 (awake), 150 (isoflurane) or 100 (enflurane and halothane) micrograms.kg-1), giving mean verapamil concentrations around 75 (range of means: 66-84 ng.ml-1). Verapamil produced mostly minor changes in the cardiovascular effects of changing [Ca2+] in both awake and anesthetized dogs, indicating mostly additive effects. Verapamil induced a decrease in HR at high [Ca2+] and abolished an increase in mean aortic pressure at both low and high [Ca2+] awake. Verapamil exaggerated the decrease in CO and stroke volume (SV) induced by low [Ca2+] during enflurane anesthesia and abolished the increase in CO induced by low [Ca2+] and exaggerated the increase in SV and LV dP/dtmax induced by high [Ca2+] during halothane anesthesia.
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PMID:Hemodynamic interactions when combining verapamil, acute changes in extracellular ionized calcium concentration and enflurane, halothane or isoflurane in chronically instrumented dogs. 146 19

The study investigated the evolution of 72-nifedipine treated cases with ischemic stroke. Dipyridamole was administered to 72 controls. Subjects showed clinical improvement, thus calcium blockers can constitute a therapy alternative. A good influence of nifedipine was remarked in blood pressure.
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PMID:Calcium blockers in ischemic stroke. 147 11


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