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

White matter of the mammalian brain is susceptible to anoxic injury, but little is known about the pathophysiology of this process. We studied the mechanisms of anoxic injury in white matter using the isolated rat optic nerve, a typical central nervous system white-matter tract. Optic nerve function, measured as the area under the compound action potential, rapidly failed when exposed to anoxia. Postanoxic recovery was variable, depending on duration of the anoxic insult; after a standard 60-minute period of anoxia, the compound action potential recovered to 28.5% of control. Irreversible anoxic injury was critically dependent on extracellular Ca2+; maintaining the tissue in zero [Ca2+] solution throughout the anoxic period resulted in 100% compound action potential recovery. Increasing perfusate [Ca2+] during anoxia from zero to 4 mM resulted in progressively less recovery. Anoxic damage to the optic nerve appears to depend on the gradual accumulation (over tens of minutes) of Ca2+ in a cytoplasmic compartment. The inorganic Ca2+ channel blockers Mn2+ (1 mM), Co2+ (1 mM), or La3+ (0.1 mM) had no effect on recovery of the compound action potential after anoxia; only Mg2+ (10 mM) significantly improved recovery. Treatment with the dihydropyridine Ca2+ channel blockers nifedipine (1-10 microM) or nimodipine (1-40 microM) also had no effect on recovery from anoxia. Thus, Ca2+ influx during anoxia does not occur via conventional Ca2+ channels. Preliminary evidence suggests that this Ca2+ influx may occur via other cation channels that are imperfectly selective for Ca2+ or via the Na(+)-Ca2+ exchanger.(ABSTRACT TRUNCATED AT 250 WORDS)
Stroke 1990 Nov
PMID:The pathophysiology of anoxic injury in central nervous system white matter. 223 86

Poly(ADP-ribose) synthetase has been purified 2,000-fold to apparent homogeneity from human placenta. The purification procedure involves affinity chromatography with 3-aminobenzamide as the ligand. The purified enzyme absolutely requires DNA for the catalytic activity and catalyzes poly(ADP-ribosyl)ation of the synthetase itself (automodification) and histone H1. Mg2+ enhances both the automodification and poly(ADP-ribosyl)ation of histone H1. The enzyme is a monomeric protein with a pI of 10.0 and an apparent molecular weight of 116,000. The sedimentation coefficient and Strokes radius are 4.6 S and 5.9 nm, respectively. The frictional ratio is 1.82. Amino acid analysis and limited proteolysis with papain and alpha-chymotrypsin indicate that the human placental enzyme is very similar to the enzyme from calf thymus, although some differences are noted. Mouse antibody raised against the placental enzyme completely inhibits the activity of enzymes from human placenta and HeLa cells and cross-reacts with the enzymes from calf thymus and mouse testis. Immunoperoxidase staining with this antibody demonstrates the intranuclear localization of the enzyme in human leukemia cells. All these results indicate that molecular properties as well as antigenic determinants of poly(ADP-ribose) synthetase are highly conserved in various animal cells.
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PMID:Purification and characterization of poly (ADP-ribose) synthetase from human placenta. 243 82

The capability of cyclohexylphenol exaprolol of protecting the ischaemic myocardium during ischaemic cardiac arrest was assessed in the isolated working rat heart. Exaprolol added to the perfusion medium in a dose of 10(-7) mol.l-1 only minimally influenced the left ventricular function (reduced the stroke volume by 18.84% and cardiac output by 14.63%). The hearts were subjected to global ischaemia for 75 min at 26 degrees C and subsequently reperfused for 60 min at 37 degrees C. The recovery of left ventricular function following reperfusion, expressed as a percentage of preischaemic functional performance was used as an indicator of the ischaemic tolerance of the heart. The effect of exaprolol on sarcolemmal (Na+ + K+)-, Mg2+- and Ca2+-ATPase activities was also examined. Exaprolol-pretreated hearts revealed better postischaemic recovery of the left ventricular dP/dt max and stroke volume as well as improved efficiency in the transformation of chemical energy to mechanical work. Exaprolol in 10(-4) mol.l-1 concentration significantly stimulated the specific activity of sarcolemmal (Na+ + K+)-ATPase. Possible mechanisms of the salutary effect of exaprolol on the ischaemic heart are discussed.
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PMID:The influence of exaprolol upon the ischaemic rat heart and its interaction with sarcolemmal (Na+ + K+)-ATPase. 256 82

Both Mg2+ and Ca2+ have been implicated as having roles in the pathomechanisms of cerebral ischemia. To further study the effects of these ions on postischemic histologic outcome, fasted rats were given one of three intravenous infusions: 5.0 mmol/kg MgCl2, 5.0 mmol/kg MgCl2 + 0.035 units/kg regular insulin, or 1.0 mmol/kg CaCl2. This resulted in elevated plasma Mg2+ or Ca2+ concentrations in the corresponding groups. A fourth group received 0.9% NaCl (saline). Preinfusion plasma glucose concentration was similar for all groups and was unchanged after infusion in rats receiving either saline or MgCl2 + insulin. In contrast, postinfusion glucose concentration was increased in the MgCl2 group (p less than 0.001) and decreased in the CaCl2 group (p less than 0.001) relative to saline-treated rats. Following respective infusions, all rats underwent 10 minutes of reversible forebrain ischemia (bilateral carotid artery occlusion and systemic hypotension) followed by 7 days' recovery. Six of 12 CaCl2-treated rats died 2-3 days after ischemia; all other rats remained neurologically indistinguishable, without gross neurologic deficits. Histologic injury in the neocortex and caudate was moderate in all groups. In the hippocampus, MgCl2 + insulin resulted in 66 +/- 6% (mean +/- SD) dead CA1 pyramidal cells, which was similar to the amount in saline-treated rats (68 +/- 10%). Injury was increased in the MgCl2 group (79 +/- 4% dead cells), while in surviving CaCl2-treated rats, injury was decreased (54 +/- 13%). We conclude that the increased injury in MgCl2-treated rats and the decreased injury noted in surviving rats receiving CaCl2 are due to the plasma glucose concentrations present prior to ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)
Stroke 1989 Apr
PMID:Effects of elevated plasma magnesium versus calcium on cerebral ischemic injury in rats. 264 53

Recent evidence supports the concept that cerebral vasospasm is involved in the pathogenesis of eclampsia. Magnesium, which has a beneficial effect in eclampsia, may act by opposing calcium-dependent arterial constriction, thereby relieving vasospasm. Magnesium may also antagonize the increase in intracellular calcium concentration caused by ischemia and thus prevent cell damage and death. Magnesium might have a role in the treatment of cerebral vasospasm and ischemia, such as occurs in subarachnoid hemorrhage, ischemic stroke, and brain trauma.
Stroke 1989 Sep
PMID:Action of magnesium sulfate in the treatment of preeclampsia-eclampsia. 267 28

Excitatory dicarboxylic amino acid neurotransmitters, particularly glutamate, have been implicated in mediating neuronal cell injury in brain ischemia-anoxia, epilepsy, and stroke. Glutamate neurotoxicity has been demonstrated in several in vitro models, as well as its prevention by a variety of agents, including several sialic acid-containing glycosphingolipid species, gangliosides. We have now examined ganglioside effects in anoxic exposed cultures of granule cells from Postnatal Day 8 rat cerebellum. Cells between 10 and 12 days in vitro were placed into an anoxic atmosphere or subjected to a chemical model of anoxia by a pulse exposure to rotenone. Widespread neuronal degeneration of neuronal cell bodies and their associated neurite network was seen the following day. These effects on cell vitality at the morphological level were quantitatively confirmed by measuring the photometric reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide to a blue formazan product. This neuronal injury was abolished by the specific N-methyl-D-aspartate receptor noncompetitive antagonists Mg2+, phencyclidine and MK-801, suggesting that this subtype of glutamate receptor is involved in the pathogenesis of anoxic granule cell injury. Pretreatment for 30 to 60 min or more or concurrent treatment with ganglioside GM1 largely prevented the ensuing neuronal death (ED50 = 25 microM), even 4 days later. Degeneration induced by exogenous glutamate was equally reduced. Asialo GM1 (lacking sialic acid) was ineffective. These results are consistent with the observed beneficial effects of the gangliosides in ischemic brain injury models in vivo.
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PMID:Monosialoganglioside GM1 protects against anoxia-induced neuronal death in vitro. 268 18

It is widely held that a glutamate-like toxin that resembles N-methyl-D-aspartate may be responsible for the death of nerve cells seen after severe neurological insults including stroke, seizures, and degenerative disorders, such as Huntington disease, Alzheimer disease, and the amyotrophic lateral sclerosis-parkinsonism-dementia complex found on Guam. One puzzling fact about these maladies is the differential vulnerability of specific groups of neurons peculiar to each condition. We report here that an identified population of central neurons, rat retinal ganglion cells, are resistant to the neurotoxic effects of millimolar concentrations of glutamate under otherwise normal culture conditions. Patch-clamp experiments show that this resistance is associated with a very small ionic current response to N-methyl-D-aspartate. Varying the ionic milieu by increasing the extracellular Ca2+ concentration, however, results in a striking increase in glutamate-induced cell death in this population. Under these conditions, Mg2+ or the amino acid antagonist MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo-(alpha,gamma)-cyclohepten-5 ,10-imine maleate], blockers of N-methyl-D-aspartate receptor-coupled ion channels, completely abrogate the lethal effects of glutamate. These findings strongly suggest that Ca2+ entry through N-methyl-D-aspartate-activated channels is responsible for this type of neuronal death and suggest strategies that may be clinically useful in the treatment of various neurological disorders.
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PMID:Central mammalian neurons normally resistant to glutamate toxicity are made sensitive by elevated extracellular Ca2+: toxicity is blocked by the N-methyl-D-aspartate antagonist MK-801. 290 Nov 1

The activity of three forms of ATPase were examined in fractions of the brain of the gerbil treated with ethylene glycol-N-N-tetra-acetic acid (EGTA) under a variety of conditions of primary and secondary (reflow) ischemia. In animals which were unilateral ischemic (ligation of the right common carotid), damage to Na+, K+-ATPase alone was observed only after at least 6 hr of ischemia had elapsed. The phenomenon occurred in only symptomatic gerbils and was absent in animals which were either asymptomatic or only displayed partial neurological symptoms. Under conditions of bilateral cerebral ischemia, in which both carotid arteries were clamped, only irreversible ischemia (60 min) followed by reflow, was associated with highly significant damage to cerebral Na+, K+-ATPase. In regional studies of the forebrain involving ischemia for 60 min plus 30 min reflow, damage to Na+, K+-ATPase was evident in the cerebrum, hippocampus, striatum and thalamus, while the hypothalamus and olfactory bulb were spared. Pretreatment of gerbils with allopurinol, clonazepam or combinations of thiopental plus either indomethacin or methylprednisolone offered protection to cerebral Na+, K+-ATPase subsequent to secondary ischemia. With only minor exceptions (striatum) neither Ca2+, Mg2+- nor Mn2+-ATPase were altered by stroke or treatment with drugs.
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PMID:Classification of ischemic-induced damage to Na+, K+-ATPase in gerbil forebrain. Modification by therapeutic agents. 299 3

Structural and behavioral features of intact and permeabilized Paramecium tetraurelia have been defined as a basis for study of Ca2+ control of ciliary reversal. Motion analysis of living paramecia shows that all the cells in a population swim forward with gently curving spirals at speeds averaging 369 +/- 19 microns/second. Ciliary reversal occurs in 10% of the cell population per second. Living paramecia, quick-fixed for scanning electron microscopy (SEM), show metachronal waves and an effective stroke obliquely toward the posterior end of the cell. Upon treatment with Triton X-100, swimming ceases and both scanning and transmission electron microscopy reveal cilia that uniformly project perpendicularly from the cell surface. Thin sections of these cells indicate that the ciliary, cell, and outer alveolar membranes are greatly disrupted or entirely missing and that the cytoplasm is also disrupted. These permeabilized paramecia can be reactivated and are capable of motility and regulation of motility. Motion analysis of cells reactivated with Mg2+ and ATP in low Ca2+ buffer (pCa greater than 7) shows that 71% swim forward in straight or curved paths at speeds averaging 221 +/- 20 microns/second. When these cells are quick-fixed for SEM the metachronal wave patterns of living, forward swimming cells reappear. Motion analysis of permeabilized cells reactivated in high Ca2+ buffers (pCa 5.5) shows that 94% swim backward in tight spirals at a velocity averaging 156 +/- 7 microns/second. SEM reveals a metachronal wave pattern with an effective stroke toward the anterior region. Although the permeabilized cells do not reverse spontaneously, the pCa response is preserved and the Ca2+ switch remains intact. The ciliary axonemes are largely exposed to the external environment. Therefore, the behavioral responses of these permeabilized cells depend on interaction of Ca2+ with molecules that remain bound to the axonemes throughout the extraction and reactivation procedures.
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PMID:Ultrastructure and motion analysis of permeabilized Paramecium capable of motility and regulation of motility. 335 46

Cardiovascular variables were measured in baboons before and during an adrenaline infusion at 1 microgram/kg/min, and following two bolus injections of either MgSO4 60 mg/kg or saline. Arterial blood pressure (ABP), systemic vascular resistance (SVR), central venous pressure (CVP), pulmonary arterial pressure and pulmonary capillary wedge pressure were all elevated by the adrenaline infusion. Cardiac output (CO), stroke volume (SV) and heart rate were unchanged but multifocal arrhythmias occurred. Mg infusion abolished arrhythmias and markedly increased CO and SV. SVR was reduced below baseline values by Mg, and ABP and CVP returned toward baseline. Saline did not alter adrenaline-induced changes in any way. It is concluded that Mg has powerful antiarrhythmic effects in the presence of catecholamines and, in addition, may have useful alpha-adrenergic antagonist effects.
Magnesium 1988
PMID:Interactions of adrenaline and magnesium on the cardiovascular system of the baboon. 337 80


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