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

The effects of fluorescein, methylene blue, and indocyanine green on hemodynamic variables and on pulse oximetry and co-oximetry measurements of arterial hemoglobin oxygen saturation (SaO2) and oxyhemoglobin percentage (% HbO2) were evaluated in 16 anesthetized dogs in vitro by co-oximetry (% HbO2) and in vivo by pulse oximetry (SaO2). The light absorbance (optical density) in plasma (range 500 to 800 nm) was measured by a spectrophotometer. Fluorescein did not affect oximetry measurements, plasma light absorbance in the range measured, or hemodynamic variables. Methylene blue caused dose-dependent decreases in measurements made with both forms of oximetry for up to 30 minutes, the decrease being greater and longer lasting with pulse oximetry (P less than 0.05). Hemodynamic measurements in 5 dogs showed that methylene blue (1 to 5 mg/kg) increased arterial pressure transiently, after which cardiac output, stroke index, and left ventricular stroke work index decreased and left ventricular end-diastolic pressure and systemic and pulmonary vascular resistances increased (P less than 0.05 with 5 mg/kg). Methemoglobin concentration measured by co-oximetry increased significantly (to 19.9 +/- 1.4%, P less than 0.05) 1 minute after 5 mg/kg of methylene blue was injected. Methylene blue had a dose- and time-dependent effect on plasma light absorbance, and this effect peaked in the 660- to 670-nm range. The data do not distinguish the relative contributions of physiology (hemodynamic change), chemistry (methemoglobin production), and physics (optical properties) to the decrease in pulse oximetry and co-oximetry measurements that follows injection of methylene blue. Indocyanine green affected neither hemodynamic variables nor co-oximetry readings but decreased pulse oximetry readings for up to 10 minutes dose dependently.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Methylene blue and indocyanine green artifactually lower pulse oximetry readings of oxygen saturation. Studies in dogs. 368 58

This study examined the role of denervation supersensitivity in the development of cerebral vasospasm. Adrenergic denervation of cat basilar artery was accomplished by resection of the superior cervical ganglia or by injection of 6-hydroxydopamine into the cisterna magna. In vivo dose-response characteristics were determined for normal and for denervated arteries, and no significant differences were found between topical applications of serotonin, norepinephrine, epinephrine, fresh blood, or incubated blood. In addition, analysis of cat blood incubated in vitro revealed that the levels of serotonin, norepinephrine, and epinephrine diminished over time, whereas levels of hemoglobin and methemoglobin increased up to Day 14. The results of this study indicate that adrenergic denervation is not the cause of cerebral vasospasm and that, whatever the mechanism, hemoglobin is far more likely to play a role than are the other agents.
Stroke
PMID:Does cerebral vasospasm result from denervation supersensitivity? 381 Jul 75

Magnetic resonance image (MRI) findings, intraoperative macroscopic findings and endocrinological functions were reported in 13 cases of hemorrhagic pituitary adenoma (HPA) according to clinical severity. The cases were divided into 3 groups: (1) classical pituitary apoplexy (PA) (n = 2), (2) subacute PA (n = 4), (3) asymptomatic HPA (n = 7). Based on MRI intensity and intraoperative findings, there were 7 cases with hemorrhagic PA and 5 with necrotic cyst formation. MRI intensities predicted the cyst contents, either hemorrhagic or xanthochromic, more accurately than CT findings. In addition, two classical cases of the PA group disclosed niveau formation on MRI, but MRI intensity in the first case differed from that in the second case. Classical PA of the first case occurred during the pregnancy. MRI intensity in the case 7 months after the onset disclosed high intensity of the upper part and normointensity of the lower part. T1 weighted image and proton image showed homogeneous intensity. On the contrast, PA of the second case showed water-like intensity on the upper part and methemoglobin-like intensity on the lower part. These different MRI intensities suggest different etiologies of niveau formation. MRI findings in the first case may indicate the chronic stage of massive intratumoral hemorrhage but the mechanism may be the same in both cases. From MRI intensity and clinical course, the cause of niveau formation in the second case is similar to that found in the literature. That is, hemorrhage was thought to have occurred in the pre-existing cyst cavity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[MRI findings and endocrinological dysfunction in hemorrhagic pituitary adenoma]. 825 74

NADPH-dependent methemoglobin reductase, first detected in erythrocytes sixty years ago, has subsequently been purified and characterized as a methylene blue reductase and a flavin reductase. The reductase plays no role in methemoglobin reduction under normal conditions, but its activity serves as the basis for the treatment of methemoglobinemia with methylene blue or flavin. On-going studies demonstrate that this cytosolic protein is also present in liver and that its primary structure distinguishes it from other known proteins. The bovine erythrocyte reductase tightly binds hemes, porphyrins, and fatty acids with resulting loss of activity. Pyrroloquinoline quinone serves as a high-affinity substrate of the reductase, suggesting that this naturally-occurring compound may be a physiological substrate. The ability of the reductase to catalyze the intracellular reduction of administered riboflavin to dihydroriboflavin suggested that this system might be exploited to protect tissues from oxidative damage. This hypothesis was supported by our finding that dihydroriboflavin reacts rapidly with Fe(IV)O and Fe(V)O oxidation states of hemeproteins, states that have been implicated in tissue damage associated with ischemia and reperfusion. Preliminary studies demonstrate that, as predicted, administration of low concentrations of riboflavin protects isolated rabbit heart from reoxygenation injury, rat lung from injury resulting from systemic activation of complement, and rat brain from damage caused by four hours of ischemia. Data from these animal studies suggest that flavin therapy holds promise in protecting tissue from the oxidative injuries of myocardial infarction, acute lung injury, stroke, and a number of other clinical conditions.
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PMID:Evidence that NADPH-dependent methemoglobin reductase and administered riboflavin protect tissues from oxidative injury. 841 88

Anoxia-reoxygenation leads to severe metabolic alterations, which result in a generalized inflammatory reaction and multiple organ dysfunction. Direct blood transfusion limits these alterations, but is accompanied by risk of transmission of infections or viral diseases. To avoid these risks, "blood substitutes" have been designed. The modified hemoglobins are not true blood substitutes because they do not possess the complex functions of erythrocytes. They are only oxygen carriers, with a short intravascular life, adapted for temporary use. They are stable, devoid of toxicity and antigenicity, and are able to carry and deliver O2 without regulation of this oxygen transport and without chemical reaction with O2. They possess rheologic properties and an oncotic pressure like those of blood. The use of natural hemoglobin solutions, obtained after lysis of erythrocytes, remains "at risk" because these solutions easily form methemoglobin, increase the oncotic pressure, present renal toxicity, and possess a too high affinity for O2. For these reasons, 5 types of modified hemoglobin solutions have been designed, prepared from human or bovine hemoglobin or by genetic engineering. These hemoglobins are highly purified to eliminate trace amounts of stroma, lipids and endotoxins, which are responsible for acute toxicity. They are modified by internal cross-linking between the monomers, or by binding to macromolecules. Afterwards, they can be polymerized or encapsulated in liposomes. The purpose of these modifications is to modulate the affinity for O2 (by decreasing the binding of O2 and increasing its delivery to tissue), to reduce the dissociation into monomers and to guard against oxidation into methemoglobin. Encapsulation in liposomes allows co-encapsulation of effector molecules and protective substances. Genetic engineering allows the production of recombinant hemoglobin with selective modifications. The modified hemoglobin solutions are essentially used in hemorrhagic shock and perioperative hemodilution. Experimental work in animals has afforded good results: restoration of normal O2 pressure and no toxicity. These assays allow frequent observation of an unexpected rapid hypertensive effect, transient, reversible, and that could be controlled by antihypertensive drugs. The mechanisms of this hypertensive effect remain controverted (stimulation of endothelin production, inhibition of nitric oxide effects, etc.). In humans, studies with healthy volunteers have been completed, while phase II clinical studies are under way in hypovolemic shock, in major abdominal, orthopedic and cardiac surgery, in stroke and in intensive care patients after surgery. The detailed results are awaited, but the modified hemoglobin solutions already appear to be without toxicity and present the same hypertensive effect as observed in animals. However, until now only low doses have been used, and the catabolism of these solutions remains largely unknown.
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PMID:[Contributions and prospects of hemoglobin derivatives]. 931 31

During head injuries and hemorrhagic stroke, blood is released into the extravascular space. The pooled erythrocytes get lysed and hemoglobin is released into the intracranial cavities. Therefore, neurons may be exposed to hemoglobin and/or its breakdown products, hemin and iron, for long periods of time. In this study, the electrophysiological actions of these agents on synaptic transmission in rat hippocampal CA1 pyramidal neurons were studied using extracellular field- and whole cell patch-recordings. Previously our laboratory reported that commercially available hemoglobin produced a dose dependent suppression of synaptic transmission in hippocampal CA1 neurons. In the present study, however, we found that this depression was caused by impurities present in the hemoglobin samples. Commercially available hemoglobin and methemoglobin did not have a significant effect on synaptic transmission. Although, reduced-hemoglobin prepared using a method described by Martin et al. [J. Pharm. Exp. Ther. 232 (1985) 708], produced a significant depression of synaptic transients, these effects were due to contamination with bisulfite that was present due to the reducing procedure. Therefore, the technique of Martin et al. was inadequate in removing the reducing agents or their breakdown products. A number of studies in literature used commercial samples of hemoglobin or reduced hemoglobin prepared using the method of Martin et al. Our observations indicate that it would be important to determine if contaminants, rather than hemoglobin, are responsible for the observed effects in these studies. Unlike hemoglobin, its breakdown products, ferrous chloride and hemin, produced an irreversible and significant depression of field excitatory postsynaptic potentials. The relevance of these effects in neurological complications that follow head injuries and hemorrhagic stroke awaits further investigation.
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PMID:Effects of hemoglobin and its breakdown products on synaptic transmission in rat hippocampal CA1 neurons. 1079 81

Bed rest is an integral part of treatment of numerous diseases. Typical examples are bone fractures of lower extremities and pelvis. Temporary immobilization is necessary also, e.g., in heart diseases (stroke), backbone and imminent abortion. The sick organism spares energy during the bed rest wich is beneficial. However, bed rest results in many alterations which are disadavantageous. They concern the function of almost all organs and systems but affect most significantly the locomotor and ciruclatory systems. Bed rest brings also about changes in the composition of peripheral blood and functions of the morphotic elements of blood. Red blood cells are subjected to the action of large amounts of reactive oxygen species (ROS). During oxidation of hemoglobin to methemoglobin superoxide radical anion (O2-) is formed: HbFe2+ + O2 --> MetHbFe3+ + O2- (1) Ferrous and ferric ions present in the cytoplasm of red blood cells may be catalysts of the Fenton reaction leading to the production of the hydroxyl radical: O2- + Fe3+ --> O2- + Fe2+ (2) Fe2+ + H2O2 --> Fe3+ + OH + HO- (3) OH shows a tremendous reactivity. It may react with lipids, proteins, nucleic acids and carbohydrates. The process of lipid peroxidation is best understood. It concerns mainly polyunsaturated fatty acids present in cell membranes. Peroxidation of membrane lipids decreases membrane fluidity and impairs its barrier function. The lowered membrane fluidity compromises erythrocyte deormability which in turn disturbs oxygen delivery to the tissues. End productions of lipid peroxidation are low-molecular wieght compounds, among them carbohydrates (ethane and pentane) and aldehydes, e.g. malondialdehyde (MDA). MDA concentration is an acknowldeged marker of the intensity of lipid peroxidation. Erythrocytes contain a complex system of protection against the action of ROS. It includes various enzymatic and non-enzymatic mechanism. The most important antioxidative enzymes of the red blood cells are superoxide dismutase (Cu,Zn-SOD, EC 1.15.1.1) catalase (CAT, EC 1.11.1.6) and glutathione peroxidase (GSH-Px, EC 1.11.1.9). Cu,Zn-SOD catalyzes the dismuation of O2- to hydrogen peroxide (H2O2). Catalase and peroxidase remove H2O2 and, moreover, GSH-Px can reduce lipid peroxides. Under normal conditions an equilibrium exists between the formation and removal ROS. If ROS are formed in excess or the defensive antioxidative mechanism are inefficient, oxidative stress develops. Derangement of the equilibrium between the formation and removal of ROS is important in the pathosgenesis of many diseases, e.g. atherosclerosis, diabetes, Down syndrome and Alzheimer disease. There are literature data on disturbances of enzymatic antioxidant defense mechanism of blood plateless during bed rest. This study was aimed at an examination of the post-traumatic bed rest on the enzymatic antioxidative defense mechanisms and lipid peroxidation in erythrocytes.
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PMID:Effect of long term bed rest in men on enzymatic antioxidative defence and lipid peroxidation in erythrocytes. 1154 39

Severe hypoxia occurs in patients with acute chest syndrome, and erythrocytapheresis has been shown to improve oxygenation. Patients with sickle cell anemia also have decreased baseline oxygen saturation values, but the effect of erythrocytapheresis on steady-state oxygenation has not been well studied. We investigated the changes in oxygen saturation versus hematocrit, fraction of hemoglobin A, and transfusion volume during 71 prophylactic erythrocytapheresis procedures performed in 5 stable patients with sickle cell anemia. Each patient had a history of either acute chest syndrome or stroke, but no serious events occurred while enrolled in the chronic exchange program. The oxygen saturation improved from 1% to 6% during erythrocytapheresis in each of our patients (p < 0.001) regardless of preprocedure saturation level or total hematocrit. We have shown that decreased baseline oxygen saturation in sickle cell disease is related to abnormal hemoglobin S levels, and oxygen saturation can be improved with erythrocytapheresis, independent of any change in the total hematocrit.
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PMID:Oxygen saturation and hemoglobin A content in patients with sickle cell disease undergoing erythrocytapheresis. 1242 35

Sickle cell disease (SCD) is the most common genetic disorder of the blood. The disease produces significantly abnormal hemoglobin (Hgb) molecules in red blood cells (RBCs). The sickling of RBCs occurs when partially or totally deoxygenated Hgb molecules distort their normal disk shape, producing stiff, sticky, sickle-shaped cells that obstruct small blood vessels and produce vasoocclusion as well as the disruption of oxygen to body tissues. Because tissue damage can occur at multiple foci, patients with SCD are at risk for other medical complications including, but not limited to, delayed growth and sexual maturation; acute and chronic pulmonary dysfunction; stroke; aseptic necrosis of the hip, shoulders, or both; sickle cell retinopathy; dermal ulcers; and severe chronic pain. The chronicity of the illness combined with frequent hospitalizations for pain and other medical management can contribute significantly to impaired psychosocial functioning, altered intra- and interpersonal relationships, and reduced quality of life. Unlike previous qualitative reviews of SCD, this article describes the relevant clinical and research data on the relation between psychosocial functioning and SCD in adult and child populations. The authors discuss the significant role of psychosocial issues in the trajectory and management of the disease and conclude that understanding the pathophysiology of SCD without thoroughly understanding the equally important psychosocial influences is misunderstanding SCD.
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PMID:A brief review of the pathophysiology, associated pain, and psychosocial issues in sickle cell disease. 1608 20

Lipid peroxidation is caused by reactive oxygen species (ROS) and is involved in traumatic brain injury (TBI). Consequently, a therapeutic strategy for TBI may be to control lipid peroxidation. The only drug approved to date for blocking lipid peroxidation is edaravone (MCI-186), a novel free-radical scavenger shown to exert neuroprotective effects in acute ischemic stroke. Although edaravone scavenges hydroxyl and nitric oxide radicals, its effect on alkoxyl radicals (OR-), which also contribute to lipid peroxidation, is unknown. To date, the study of free radicals in blood has been severely hampered by technical difficulties in their detection. We used an in vitro and ex vivo electron spin resonance (ESR) method employing 5,5-dimethyl-1-pyrroline-N-oxide as a spin trap to investigate whether edaravone can scavenge OR-. By mixing either methemoglobin or human blood with tert-butyl hydroperoxide, we found that this technique can detect OR- generated in vitro. We also found that generated OR- can be completely absorbed by administration of edaravone in vitro (400 microM). Analysis of jugular venous blood collected from 17 TBI patients immediately before and 20 minutes after the administration of edaravone (30 mg, i.v.) revealed higher OR- levels in the untreated patients blood than in normal control blood samples. However, treatment with edaravone suppressed these OR- levels by 24.6% (radical intensity = 71.1 +/- 5.2-53.6 +/- 5.2; p < 0.01). Thus, edaravone can scavenge OR- and significantly reduce levels of these radicals in TBI patients. The novel ex vivo ESR method described here provides a valuable clinical measure of oxidative stress.
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PMID:Alkoxyl radical-scavenging activity of edaravone in patients with traumatic brain injury. 1711 6


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