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

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

Ciliary motility was examined optically in tissue cultures from frog palate epithelium and frog's esophagus as a function of extracellular concentration of adenosine 5'-triphosphate (ATP) and related compounds. The addition of micromolar concentration of ATP caused a strong enhancement of frequency and wave velocity in the direction of the effective stroke. Since adenosine 5'-[beta,gamma imido]-triphosphate (AMP-PNP), a nonhydrolyzable analog of ATP, produces the same effects, ATP hydrolysis is not required. The overall potency is ATP approximately equal to AMP-PNP greater than ADP much greater than adenosine greater than AMP. It is suggested that both the phosphate and the base moieties are involved in ATP binding. The enhancement of ciliary activity by extracellular ATP is dependent on the presence of extracellular Ca2+, which can be replaced by extracellular Mg2+. The effect of a number of potent inhibitors of the voltage-gated calcium channels on the stimulation of ciliary activity by ATP were examined. No effect was detected in the concentration range within which these agents are specific. On the other hand, quinidine, a potent inhibitor of K+ (calcium-dependent) channels, inhibits the effect of ATP. The following model is suggested: exogenous ATP interacts with a membrane receptor in the presence of Ca2+, a cascade of events occurs which mobilizes intracellular calcium, thereby increasing the cytosolic free Ca2+ concentration which consequently opens the calcium-activated K+ channels, which then leads to a change in membrane potential. The ciliary response to these changes is the enhancement of ciliary activity.
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PMID:Possible mechanism of ciliary stimulation by extracellular ATP: involvement of calcium-dependent potassium channels and exogenous Ca2+. 149 86

The plasma vWF levels in patients with CVD were determined using ELISA technique with two monoclonal anti-human vWF antibodies. The results showed that the vWF values in the acute stage of CVD increased significantly. They gradually decreased third weeks after the onset of the CVD. The vWF in the chronic stage of CVD remained higher than normal, but lower than that in the acute stage. The plasma vWF values showed practically no difference in either cerebral infarction or hemorrhage. The average plasma vWF level in the patients with TIA was higher than that in the controls but lower than that in the patients with complete stroke. It was found that the plasma vWF correlated with platelet aggregation induced by ADP constantly, but not with other risk factors. It was considered that elevated vWF would rather be regarded in CVD as a relatively independent risk factor.
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PMID:[A study of plasma von Willebrand factor concentration in patients with cerebrovascular disease]. 149 7

In muscle fibres labelled with iodoacetamidotetramethylrhodamine at Cys707 of the myosin heavy chain, the probes have been reported to change orientation when the fibre is activated, relaxed or put into rigor. In order to test whether these motions are indications of the cross-bridge power stroke, we monitored tension and linear dichroism of the probes in single glycerol-extracted fibres of rabbit psoas muscle during mechanical transients initiated by laser pulse photolysis of caged ATP and caged ADP. In rigor dichroism is negative, indicating average probe absorption dipole moments oriented more than 54.7 degrees away from the fibre axis. During activation from rigor induced by photoliberation of ATP from caged ATP in the presence of calcium, the dichroism reversed sign promptly (half-time 12.5 ms for 500 microM-ATP) upon release of ATP, but then changed only slightly during tension development 20 to 100 milliseconds later. During the onset of rigor following transfer of the fibre from an ATP-containing relaxing solution to a rigor medium lacking ATP, force generation preceded the change in dichroism. The dichroism change occurred slowly (half-time 47 s), because binding of ADP to sites within the muscle fibre limited its rate of diffusion out of the fibre. When ADP was introduced or removed, the dichroism transient was similar in time course and magnitude to that obtained after the introduction or removal of ATP. Neither adding nor removing ADP produced substantial changes in force. These results demonstrate that orientation of the rhodamine probes on the myosin head reflects mainly structural changes linked to nucleotide binding and release, rather than rotation of the cross-bridge during force generation.
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PMID:Transients in orientation of a fluorescent cross-bridge probe following photolysis of caged nucleotides in skeletal muscle fibres. 153 Sep 78

The abuse of anabolic-androgenic steroids by athletes has recently been associated with the development of myocardial infarction and stroke. Because platelets play a pathogenic role in these disorders, the authors hypothesized that androgenic steroid abuse among weight lifters was associated with increased platelet aggregation as measured in vitro. Twenty-eight study participants were recruited. Twelve denied current androgen use. However, 8 of these 12 tested positive for urinary androgens. Nonsignificant trends toward increased platelet counts and increased platelet aggregation to adenosine diphosphate were noted when androgen users were compared to nonusers. However, when stratified by age, older (greater than 22 years) androgen users required lower concentrations of collagen to produce 50% aggregation of test platelets than did younger (less than or equal to 22 years) androgen users (1.47 versus 3.35 micrograms/ml; p = .01). Further subgroup analysis revealed nonsignificant trends toward increased adenosine diphosphate-induced aggregability and nonsignificant trends in the platelet count in older weight lifters. Subsequent studies using collagen threshold aggregometry revealed no age-dependent effect in 17 other men (aged 18 to 46 years) not specifically selected for activity (r = .17). This study suggests an association between androgen use, age, and increased platelet sensitivity to collagen in weight lifters and may be helpful in explaining recent thrombotic disease in androgen users. It additionally calls into question the validity of subjective reporting when assessing androgen use among weight lifters.
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PMID:Androgenic-anabolic steroid abuse and platelet aggregation: a pilot study in weight lifters. 153 13

The purpose of this study was to examine the effects of ethanol exposure on responses of cerebral arterioles in vivo. Rats were fed liquid diets with or without ethanol for 2-3 mo. Using intravital microscopy, we measured diameter of cerebral arterioles in non-ethanol- and ethanol-fed rats in response to acetylcholine, histamine, ADP, the thromboxane analogue (U-46619), and nitroglycerin. In non-ethanol-fed rats, acetylcholine, histamine, and ADP produced dose-related dilatation of cerebral arterioles. In ethanol-fed rats, however, acetylcholine produced vasoconstriction, and vasodilatation in response to histamine and ADP was impaired. Dilatation of cerebral arterioles in response to nitroglycerin and vasoconstriction in response to the thromboxane analogue (U-46619) were similar in non-ethanol-fed and ethanol-fed rats. Thus these findings suggest that chronic ethanol exposure impairs responses of cerebral arterioles to agonists, which produce dilatation via the release of an endothelium-derived relaxing factor. We speculate that impaired vasodilatation coupled with preservation of vasoconstriction in ethanol-fed rats may have important implications for the pathogenesis of stroke during chronic alcohol ingestion.
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PMID:Responses of cerebral arterioles during chronic ethanol exposure. 155 88

The chemistry, pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage of ticlopidine are reviewed. Ticlopidine appears to inhibit platelet aggregation induced by adenosine diphosphate. Ticlopidine hydrochloride is rapidly absorbed after oral administration, and maximum antiplatelet effects occur one to three hours after the dose. In multicenter, randomized, double-blind trials, ticlopidine was more effective than aspirin or placebo in preventing stroke, myocardial infarction, or death caused by vascular events. Ticlopidine was more effective than aspirin in preventing recurrent transient ischemic attacks after six months of therapy. Ticlopidine has also been used to prevent occlusion and improve patency of aortocoronary bypass grafts, to prevent ischemic ulcers in patients with chronic arterial occlusive disease, and to slow the progression of diabetic microangiopathy. The most serious adverse effect, neutropenia, occurred in about 1% of patients. The most frequently reported adverse effects are diarrhea, nausea, vomiting, and abdominal cramps. Ticlopidine is indicated for reducing the risk of thrombotic stroke in patients who have experienced a minor stroke, transient ischemic attack, or completed thrombotic stroke. The recommended dosage is 500 mg/day in two divided doses taken with food. Ticlopidine is an alternative agent for the primary and secondary prevention of stroke. Because of the risk of neutropenia and agranulocytosis and the high cost of therapy, ticlopidine should be reserved for patients who are intolerant of or lack benefit from aspirin.
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PMID:Ticlopidine: a new platelet aggregation inhibitor. 161 11

The structure and function of the chemicals contributing to the three main peaks seen with 1H NMR spectroscopy, N-acetyl-L-aspartate (NAA), creatine/phosphocreatine (Cr), and choline-containing compounds (Cho) is reviewed and the changes seen with these compounds in various disease states are briefly outlined. NAA is present within neurons although its biological function is largely unknown. NAA is elevated in several degenerative neurological conditions including amyotrophic lateral sclerosis and canavan disease, and in high concentrations it may behave like a neurotoxin. The creatine peak seen with 1H NMR spectroscopy consists of creatine and phosphocreatine which serve as a reserve for high-energy phosphates in the cytosol of muscle and neurons. They also buffer cellular ATP/ADP. The Cho peak seen with 1H NMR consists of a complex mixture of Cho-containing compounds. Cho is a precursor for the neurotransmitter acetylcholine and for the membrane constituent phosphatidylcholine. Future studies of changes seen in the Cho peak with stroke, degenerative dementia, drug intake, and infectious and neoplastic brain masses will be of great interest.
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PMID:A review of chemical issues in 1H NMR spectroscopy: N-acetyl-L-aspartate, creatine and choline. 165 Feb 41

In 80 patients with moderate hypertension the effects of nisoldipine 10 mg b.i.d., nifedipine 10 mg and 20 mg t.i.d., diltiazem 60 mg and 120 mg t.i.d., and verapamil 40 mg q.i.d. (all after single dose and 14 days' treatment) on blood pressure; hemodynamic parameters (cardiac output, stroke volume, left ventricular ejection fraction, and total peripheral resistance); and red blood cell and platelet functional state parameters (platelet aggregation, erythrocytal mechanical resistance, and free hemoglobin and ADP levels in plasma) were studied. All of the drugs studied in doses mentioned produced statistically significant hypotensive effects. Nifedipine 20 mg and nisoldipine 10 mg produced the most peripheral vasodilatator activity after a single dose and chronic treatment. Diltiazem had the same effect only in doses of 120 mg and after chronic treatment. However, all the drugs significantly normalized the red blood cell and platelet functional state disturbances in 70-80% of patients with moderate hypertension, even 2 h after a single dose. Disaggregation effect was parallel to clinical improvement. These data make it possible to predict the individual response of most patients to antihypertensive drugs on the basis of acute pharmacological tests, with determination of disaggregation effect.
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PMID:The effects of nisoldipine, diltiazem, nifedipine, and verapamil on hemodynamic parameters and red blood cells-platelet interactions in patients with arterial hypertension. 172 40

The objective of the present study was to assess changes in cellular energy metabolism in focal and perifocal areas of a stroke lesion and to explore how these changes are modulated by preischemic hyperglycemia. A model for reversible occlusion of the middle cerebral artery (MCA) in rats was used to study changes in energy metabolism. Following MCA occlusion for 5, 15, or 30 min in normoglycemic rats, the tissue was frozen in situ, and samples from the lateral caudoputamen and from two neocortical areas were collected for metabolite analyses, together with a control sample from the contralateral, nonischemic hemisphere. Two other groups, subjected to 30 min of MCA occlusion, were made hyperglycemic by acute glucose infusion or by prior injection of streptozotocin. Enzymatic techniques were used for measurements of phosphocreatine, creatine, ATP, ADP, AMP, glycogen, glucose, pyruvate, and lactate. The neocortex of the contralateral, nonischemic hemisphere had labile metabolites that were similar to those measured in control animals. Ipsilateral neocortex bordering the focus, and thus constituting the "penumbra," showed mild to moderate ischemic changes. In the "focus" (lateral caudoputamen plus the overlying neocortex), deterioration of energy state was rapid and relatively extensive (ATP content 20-40% of control). After 5 min of occlusion, no further deterioration of metabolic parameters was observed. Substrate levels were markedly reduced, and lactate content rose to approximately 10 mM kg-1.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Focal and perifocal changes in tissue energy state during middle cerebral artery occlusion in normo- and hyperglycemic rats. 172 40


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