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

The effect of Mg infusions on cardiovascular function were investigated in 6 adult male chacma baboons over a wide range of serum Mg concentrations. There was a dose-dependent reduction in systemic vascular resistance which correlated well with serum Mg levels (r = -0.67; p less than 0.001), but arterial blood pressure was only moderately affected at serum Mg levels below 5 mmol/l. Heart rate was reduced at serum Mg concentrations above 5 mmol/l. Cardiac output and stroke work were increased at all Mg levels up to 5 mmol/l, and stroke volume increased significantly until the serum Mg level exceeded 7 mmol/l. Central venous pressure and pulmonary capillary wedge pressure were not affected by increasing magnesium levels, and there was no evidence of myocardial depression at any level of serum Mg.
Magnesium 1987
PMID:Cardiovascular effects of magnesium sulphate in the baboon. 344 7

To assess the consequences of hypercalcemia on systemic and renal hemodynamics, vasoactive hormones, and water and electrolyte excretion in intact, conscious mongrel dogs, measurements in 10 dogs receiving 100 mg/kg calcium gluconate and 10,000 U/kg vitamin D daily for 2 weeks were compared with measurements made in 10 time-control dogs not receiving calcium or vitamin D. Hypercalcemia induced by dietary supplementation with calcium and vitamin D resulted in profoundly reduced glomerular filtration rate (40 vs 78 ml/min in controls; p less than 0.005), estimated renal plasma flow (145 vs 267 ml/min in controls; p less than 0.005), and renal blood flow (254 vs 441 ml/min in controls; p less than 0.005). Renal resistance was significantly increased in the hypercalcemic dogs (0.57 +/- 0.07 vs 0.28 +/- 0.01 mm Hg/ml/min; p less than 0.005). Hypercalcemia also resulted in increased fractional excretion of water (4.8 vs 1.4% in controls; p less than 0.005), sodium (1.4 vs 0.6% in controls; p less than 0.005), calcium (1.7 vs 0.7% in controls; p less than 0.01), and magnesium (10.2 vs 4.1% in controls; p less than 0.005). Systolic blood pressure (160 vs 172 mm Hg in controls; p less than 0.05) and stroke volume were lower (0.024 vs 0.036 L/beat in controls; p less than 0.005) in hypercalcemic dogs, presumably because of the diuresis, while total peripheral resistance was higher (36 vs 31 mm Hg/L/min; p less than 0.05) in controls. Magnesium levels were significantly lower in the experimental group (1.3 vs 1.7 mg/dl in controls; p less than 0.0005). Aldosterone levels, plasma renin activity, and urinary prostaglandin excretion were not significantly affected.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Systemic and renal vascular responses to dietary calcium and vitamin D. 377 Aug 72

Obesity, a well-known phenomenon in Western society, is frequently associated with cardiovascular and endocrine disease. Strokes, myocardial infarction, diabetes and hyperlipidemia are classical reasons for the high mortality and morbidity of overweight people. For this reason, intensive weight-reduction programs have been proposed: low-calorie diets, total starvation, drugs and even surgery. Total starvation and some low-calorie diets are, however, also associated with sudden death, most probably of cardiac origin. Experimental data from our laboratory show that total starvation is accompanied by a severe depletion of magnesium in myocardial tissue. Protein-sparing modified low-calorie diets, however, can protect against this mineral loss even if magnesium supplementation alone cannot obtain this goal. Applying these principles in overweight man show weight reduction without mineral loss or cardiac disturbance. Surgery with 'ileal bypass' procedures gives rise to severe hypomagnesemia and hypocalcemia with tetany and spasmophilia. New procedures, derived from experimental surgery, are 'gastric bypass' and 'gastroplasty'. These methods, only applied in very obese patients (body mass index greater than 40, normal 23-27) show no change in mineral concentrations of calcium and magnesium and no clinical symptoms suggestive for mineral loss. A good, controlled weight-reduction program under strict medical surveillance can, in this way, offer new perspectives in the treatment of one of our most frequent 'culture-induced' diseases.
Magnesium 1987
PMID:Magnesium and obesity: effects of treatment on magnesium and other parameters. 382 Nov 74

The metabolism of inositol phospholipids of the erythrocyte membrane was compared in normotensive Wistar-Kyoto (WKY), spontaneously hypertensive (SHR), and stroke-prone SHR (SHR-SP) rats. This was performed on isolated ghost membranes by measuring the incorporation of 32P from [ gamma-32P ] adenosine triphosphate (ATP) into the diphosphoinositides (DPI) and the triphosphoinositides (TPI) which were the only 32P-labeled phospholipids. 32P-labeling of TPI was altered in adult and 3-week-old SHR as well as in SHR-SP compared to WKY controls; the radioactivity associated with TPI in hypertensive rats was about 30% lower than that associated with TPI in age-matched normotensive controls. By contrast, the radioactivity associated with DPI was similar in both hypertensive and normotensive rats. Measurement of the phosphoinositide distribution in both SHR and WKY indicates that the change observed in 32P-TPI could not be accounted for by a reduced phosphatidylinositol content in SHR membrane. Measurement of the Mg2+-activated TPI-phosphomonoesterase and of the Ca2+-activated polyphosphoinositide phosphodiesterase activities did not show any significant difference between SHR and WKY. It thus appears that the altered phosphoinositide metabolism observed in hypertensive rats was a consequence of some alteration in the activity of kinases which are responsible for the conversion of phosphatidylinositol into DPI and TPI. These results also suggest that the defect in phosphoinositide metabolism observed in genetically hypertensive rats was not a consequence of the blood pressure elevation and could be related to the pathogenesis of hypertension.
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PMID:Altered turnover of polyphosphoinositides in the erythrocyte membrane of the spontaneously hypertensive rat. 630 31

Considerable experimental evidence has accumulated to indicate that brain ischemia or stroke-like events will lead to rapid losses of brain potassium, magnesium, ATP, creatine phosphate and glucose. These events are usually followed by an uptake of sodium and calcium ions. Increased uptake or excess Ca2+ uptake in neuronal cells is thought to be the prime cause of neuronal death in the brain. Mg2+ deficiency is known to produce a host of neurological disturbances in man; experimentally, Mg2+ deficiency leads to excess uptake of Ca2+ in the brain. Strokes and transient ischemic attacks also are known to be associated with neurological disturbances and ionic changes in the brain. Stroke patients have been reported to exhibit deficits in serum and CSF [Mg]. Acute Mg or K deficiency can produce cerebrovasospasm, at least experimentally. The lower the extracellular concentration of either Mg2+ or K+, the greater the magnitude of cerebral arterial contraction. These cerebrovascular contractions induced by lowering either the [Mg2+]0 or [K+]0 cannot be antagonized or attenuated by known pharmacologic antagonists. The cerebrovasospasms produced upon lowering [Mg2+]0 can be modulated by [K+]0 and vice versa; e.g. the lower the [K+]0, the greater the degree of vasospasm upon withdrawal of [Mg2+]0 and vice versa. Lowering [Mg2+]0 in situ and in vitro results in increased uptake of Ca2+ in the brain and the cerebral arteries. Cerebrovasospasms induced by substances that are known to be released in the brain on injury, such as prostanoids and serotonin, are relaxed dramatically by addition of [Mg2+]0. Infusions of MgSO4 into the brain via the internal carotid artery produces dose-dependent lowering of systolic and diastolic blood pressure as well as dose-dependent vasodilatation of arterioles (17-30 micron) and venules (18-40 micron) in the cerebral microcirculation, as observed by direct in situ high-resolution TV image-intensification microscopy. In clinical studies, infusion of MgSO4 has been reported to alleviate cerebrovasospasms. Epidemiological evidence is accumulating to suggest that consumption of fruit and vegetables (foodstuffs relatively high in K and Mg, and low in Na) is associated in certain geographic regions with a lower than normal incidence of strokes, particularly that of cerebral hemorrhage. On the basis of such data, and the findings reported herein, we believe one must consider that certain types of cerebrovascular accidents, transient ischemic attacks and 'classical' migraine attacks may be associated with a 'true' Mg deficiency and altered fluxes of K+ ions in the brain and CSF.(ABSTRACT TRUNCATED AT 400 WORDS)
Magnesium 1984
PMID:Interactions of Mg and K on cerebral vessels--aspects in view of stroke. Review of present status and new findings. 639 42

In an open controlled trial with 6 male human volunteers Mg and K intake was reduced to 32-35% of normal during a 5- and 4-day period, respectively and 80 mg Furosemide/day was coadministered during the second period in order to induce Mg and K wasting. After each testing period an intravenous infusion of 27.87 mEq Mg and K was administered as K, Mg-D,L-aspartate during 2 h. Electrolyte and fluid balance were analysed before, during and after the testing period. Moreover, impedance cardiographic measurements were carried out in order to determine changes of cardiovascular function, and 24-hour ECGs were recorded simultaneously. It could be shown that reduced Mg and K intake induces depletion of the intracellular stores which was furthermore enhanced by coadministration of the loop diuretic Furosemide. Whereas Mg renal elimination amounted only to 60-54% of intake, K elimination exceeded intake to a considerable extent, a fact that could be explained by the lack of Mg. Changes of cardiovascular function, such as stroke volume, cardiac output and end-diastolic volume, expressed by alterations of total resistivity ZO, were less pronounced, but could be inverted at least partly by a single intravenous infusion of K,Mg-D,L-aspartate. Heart rate and 24-h ECG did not reveal any detectable change. The testing procedure described here can be considered a reliable model for tests in clinical pharmacology.
Magnesium 1984
PMID:Influence of magnesium and potassium deficiency on renal elimination and cardiovascular function demonstrated by impedance cardiography. 653 36

The protection afforded by cardioplegia during elective ischemic arrest can be partly compromised by a reperfusion injury, which may impede the recovery of cardiac function. We previously showed experimentally that this postischemic damage could be largely avoided by an appropriate crystalloid reperfusate. The present study was thus undertaken to assess the effects of this "reperfusion solution" clinically. One hundred twelve patients undergoing valve replacement with the aid of hypothermic cardioplegia (K+ 12 mEq, Mg2+ 26 mEq) were prospectively divided in two groups: Group I (n = 49) received an unmodified blood reperfusate. In Group II (n = 63), 1 L of the reperfusion solution was delivered just prior to removal of the aortic clamp. The formulation of the reperfusion solution adhered to the following principles: (1) maintenance of cardioplegia (K+ = 15 mEq), (2) replenishment of Ca2+ stores (Ca2+ = 2.5 mEq), (3) substrate provision (glutamate = 2,942 gm), (4) buffering (pH = 7.70 at 28 degrees C), and (5) hyperosmolarity (370 mOsm). The two groups were matched for preoperative data except for a higher incidence of isolated aortic valve replacement (p = 0.01) in Group II. Also, the cross-clamp time (mean +/- standard error of the mean) was longer in Group II (94 +/- 4 minutes versus 63 +/- 4 minutes, p less than 10(-6]. The reperfusion solution was found to increase both the rate and extent of postischemic functional recovery, as evidenced by (1) a lower proportion of catecholamine-supported patients 48 hours after operation (9/63 [14.28%] versus 16/49 [32.6%] in the control group [p less than 0.03]) and (2) a lower amount (gamma/kg/min) of dobutamine required to achieve stable hemodynamics (11 +/- 1 versus 26 +/- 6 in the control group [p less than 0.03]). A similar recovery pattern was noted in the high-risk subgroup of patients with mitral valve disease. Further, serial postoperative hemodynamic measurements were performed in 31 randomly selected patients (10 control and 21 reperfused). Although the reperfused patients were found to be at higher risk because of lower preoperative cardiac indices and longer cross-clamp times, they consistently achieved better postoperative hemodynamics with a lower incidence of catecholamine support. This hemodynamic improvement was particularly reflected by a higher left ventricular stroke work index throughout the postoperative course, the difference being significant 6 hours and 12 hours postoperatively.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:An asanguineous reperfusion solution. An effective adjunct to cardioplegic protection in high-risk valve operations. 674 22

A history of alcohol abuse associated with hypertension and chronic alcohol consumption is the leading cause of secondary cardiomyopathy. Both acute and chronic alcohol consumption precipitate arrhythmias. However moderate alcohol intake exerts a protective effect against coronary heart disease and stroke. Morbidity is lowest among light drinkers, slightly higher among lifelong abstainers and much higher among heavy drinkers. Magnesium deficiency is common among chronic alcoholics and frequent in Brazil. Magnesium therapy may have beneficial effects when there is excessive ethanol consumption.
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PMID:[Cardiovascular impact of alcoholism]. 748 61

The NMDA receptor is coupled to a cation-selective ion channel, which has been implicated in important brain functions such as long-term potentiation and burst firing, and in neuronal death associated with stroke and epilepsy. We have investigated the binding properties of [3H]MK-801, which binds selectively to the open state of the NMDA channel, at physiological concentrations of Mg2+ in membrane preparations of the rat cerebral cortex. Glutamate and glycine were found to enhance [3H]MK-801 binding at low concentrations and inhibit [3H]MK-801 binding at high concentrations. The inhibition of [3H]MK-801 binding was due to an enhancement of the dissociation rate constant and was reversed by competitive glutamate and glycine antagonists. These findings could be explained by a glutamate- and glycine-induced decrease in the affinity of [3H]MK-801 binding sites within activated NMDA channels, in the presence of Mg2+. This decrease in [3H]MK-801 affinity may correspond to a decreased affinity of the site where Mg2+ causes a voltage-dependent block of the NMDA channel.
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PMID:Glutamate and glycine decrease the affinity of [3H]MK-801 binding in the presence of Mg2+. 768 60

One hundred percent of anesthetized rats administered 6.6 gm/kg of ethanol IP died within 10-35 min of alcohol injection; upon autopsy of the brain all demonstrated profound subarachnoid and intracranial bleeding, clear signs of hemorrhagic stroke. Pretreatment of rats with 4 mumol/min MgCl2, but not saline, via IV administration (for 30-45 min), prevented hemorrhagic stroke in all animals so treated with 6.6 gm/kg ethanol. Administration of the stroke dose of alcohol resulted in rapid (within 3-5 min) and marked deficits in whole brain intracellular free Mg ([Mg2++]i) as observed by in vivo 31P-NMR spectroscopy. Intracellular pH (pHi) and the phosphocreatine [PCr]/[ATP] ratio also fell following a significant fall in brain [Mg2+]i). Brains of rats that exhibited strokelike events, upon death and autopsy, demonstrated continued and marked intracellular acidosis with progressive fall in the [PCr]/[ATP] ratio and elevation of inorganic phosphate (Pi) and [H+]i; these events were not accompanied by any rises in systemic arterial blood pressure. Rats pretreated with MgCl2 exhibited relatively stable brain [Mg2+]i, and essentially unchanged pHi, [PCr], [ATP], or [Pi] following alcohol administration, although such animals exhibited threefold alterations in plasma Mg2+, as measured by ion selective electrodes. These observations suggest that high alcohol ingestion can result in severe vasospasm, ischemia, and rupture of blood vessels probably as a consequence of depletion of brain [Mg2+]i, events that can be prevented by Mg2+ pretreatment.
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PMID:Role of brain [Mg2+]i in alcohol-induced hemorrhagic stroke in a rat model: a 31P-NMR in vivo study. 777 64


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