Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Elevated brain lactate during incomplete ischemia is thought to contribute to the irreversibility of cell damage by interference with mitochondrial respiratory function, that should be evident in reduced cytochrome oxidase (CO) activity. In this study changes in the density of CO staining in a stroke model in the rat were assessed. Brains were analyzed subsequent to 30 min of ischemia followed by 30 min of reperfusion. The effects of postischemic treatment with sodium dichloroacetate (DCA)--a compound used to decrease lactate, were also evaluated. Examination of lateral cortex, hippocampus, and corpus striatum showed different intensities of CO in a distribution consistent with known regional variations in metabolic activity of the forebrain. Known laminar staining patterns in lateral cortex and areal patterns in the hippocampus were also confirmed. Comparable regions in ischemic forebrain were stained less densely for CO than controls. Image analysis demonstrated that the density of CO: (a) was greater in lateral cortex than hippocampus in control; (b) in ischemics was reduced by an equal degree in cortex and hippocampus; (c) lacked regional uniformity in ischemic rats; and (d) was not changed by DCA treatment in the majority of cases of ischemia. Our results suggest that lactate may not be the major determinant of 'selective vulnerability'. Despite elevated lactate levels in lateral cortex when compared to hippocampus in a previous study, the proportionate decrease in CO activity in lateral cortex and hippocampus was equal. However, there was a considerable decrease in CO activity subsequent to high brain lactate and some ischemic hemispheres appeared to respond to DCA treatment. Therefore, the role of excessive lactate in the exacerbation of 'selective vulnerability' warrants further evaluation. CO histochemistry can be used successfully to determine the distribution of pathology and the quality of fixation of ischemic forebrain. Densitometric measurements allowed comparative assessment of degrees of injury and the effects of treatment in discrete anatomical regions. This kind of analysis may allow localization of pathology within specific cellular circuits.
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PMID:Densitometric analysis of cytochrome oxidase in ischemic rat brain. 169 9

Mechanistically based short-term in vitro tests to evaluate the relative cytotoxicity of of chemicals will complement in vitro genotoxicity testing during the initial phases of toxicity evaluation as well as provide information on the cellular site of action for chemicals found to be toxic in animals. The objective of this study was to characterize a procedure for evaluating mitochondrial membrane potential, an integral component of cellular energy homeostasis and normal cellular function, as an in vitro indicator of chemically induced cytotoxicity. Rhodamine 123, a cationic fluorescent dye whose mitochondrial fluorescence intensity decreases quantitatively in response to dissipation of mitochondrial transmembrane potential, was used to evaluate disturbances in mitochondrial membrane potential. Cultured rat liver epithelial cells (WB cell line) or human skin fibroblasts (MSU-2 cell line) treated with the oxidative phosphorylation uncoupler 2,4-dinitrophenol (DNP) or the cytochrome oxidase inhibitor sodium azide were used to characterize the system. In addition, acetaldehyde, which has been reported to damage the plasma membrane, but not the mitochondrial membrane, was used to demonstrate the specificity of this assay system. Mitochondrial membrane potential was not significantly affected by the cell culture density, as long as the cells were in the logarithmic phase of growth. The stage of the cell cycle influenced the mitochondrial membrane potential in human skin fibroblasts (highest in late G1-early S) but not in rat liver cells. DNP and sodium azide significantly (p less than 0.01) reduced the mitochondrial membrane potential in both cell lines compared to untreated cells, while acetaldehyde did not reduce the mitochondrial membrane potential in either cell line. This assay provides a tool for evaluating the effect of chemical treatments on mitochondrial membrane potential, as well as an indicator of cytotoxicity which does not require the use of animals.
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PMID:Assessment of mitochondrial membrane potential as an indicator of cytotoxicity. 185 17

The Ca2(+)-induced red shift of the cytochrome a absorption spectrum is counteracted specifically by Na+ ions, whereas neither K+ nor Li+ do show comparable effect. At the same time Na+ does not reverse the H(+)-induced red shift of cytochrome a 2+. It is suggested that Na+ competes with Ca2+ for binding site(s) within the cytochrome oxidase output proton well communicating the heme a propionate substituent responsible for the Ca2(+)- or H(+)-induced red-shift of cytochrome a (Saari et al. 1980, J. Bioenerget. Biomembr. 12, 325-338) with the c-aqueous phase. The unusual ionic specificity of the well (Ca2+, Na+, proton) may point to H3O+ rather than H+ being the ion involved in proton conduction through the output well of cytochrome oxidase.
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PMID:Na(+)-induced reversal of the Ca2(+)-dependent red-shift of cytochrome a. Is there a hydronium output well in cytochrome c oxidase? 215 24

Administration of sodium perchlorate to rats for 45 days leads to decreased activities of citric acid cycle enzymes. The oxidation of succinate both in state 3 and state 4 conditions and endogenous ATP content of mitochondria decreased during perchlorate toxicity. The significant decrease in cytochrome aa3 in perchlorate-treated rats may be one of the prime factors involved in the decreased rate of respiration. The permeability of mitochondria of perchlorate-treated rats is altered as indicated by increased oxidation of NADH and low respiratory control ratio (RCR).
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PMID:Effect of perchlorate on mitochondrial function. 216 Apr 26

Addition of potassium to sodium-loaded asolectin liposomes induces an internal alkalinization even in the absence of ionophores. Most of the K+ entry is electrogenic, as shown by fluorescent changes in the potential-sensitive probe Oxonol V. The major part of the proton efflux observed must therefore be electrophoretic. However, in the presence of high concentrations of membrane permeable n-butyltriphenylphosphonium, potassium addition induces a residual alkalinization under conditions where no membrane potential can be observed with Oxonol V. This suggests that liposomes also catalyze direct electroneutral K+/H+ exchange, as has been theoretically predicted for cytochrome oxidase proteoliposomes (Wrigglesworth, J.M., Cooper, C.E., Sharpe, M.A. and Nicholls, P. (1990) Biochem. J. 270, 109-118). Free fatty acids present in the soybean phospholipid mixture may be responsible for such activity.
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PMID:The mechanism of potassium movement across the liposomal membrane. 226 7

The fast axonal transport of [3H]proline-labeled proteins and [3H]fucose-labeled glycoproteins delivered to the dorsal lateral geniculate nucleus in the developing rat optic nerve was investigated during tetrodotoxin-induced monocular impulse blockade. Repeated intraocular injections of various dosages of tetrodotoxin or citrate buffer vehicle were made every two days in rats aged 5-21 days postnatal, and the accumulation of rapidly transported radioactivity in the lateral geniculate nucleus measured between three and twelve hours post-injection at each age. The effectiveness of prolonged tetrodotoxin treatment was monitored by loss of the pupillary light reflex and the level of cytochrome oxidase activity in the contralateral superior colliculus and dorsal lateral geniculate nucleus. Numbers of optic axons proximal to the chiasm and the frequency of retinal ganglion cells per unit distance from the optic disc were examined for signs of tetrodotoxin-induced degeneration of the retinofugal pathway. Tetrodotoxin-treatment reduced the amount of fucosyl glycoproteins, but not proline-labeled proteins, axonally transported to the lateral geniculate nucleus during the first three weeks of postnatal development. Other studies indicated that tetrodotoxin significantly reduced the incorporation of [3H]fucose into retinal proteins indicating that the reduction in transport was probably due to a decrease in precursor incorporation into retinal ganglion cells. Electron microscopy of ganglion cells at 21 days revealed dilated and vacuolated Golgi cisternae associated with tetrodotoxin treatment, suggesting that tetrodotoxin may alter fucose metabolism by secondarily disrupting Golgi organization. Other protein synthetic machinery in these cells, including ribosomes and rough endoplasmic reticulum, appeared normal throughout tetrodotoxin treatment. These data indicate that Na+-dependent optic impulse activity may be indirectly related to the axonal transport of glycoproteins during early postnatal development by mediating the incorporation of precursor into glycoproteins at the Golgi apparatus and their subsequent entrance into the fast transport system.
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PMID:The effect of intraocular injection of tetrodotoxin on fast axonal transport of [3H]proline- and [3H]fucose-labeled materials in the developing rat optic nerve. 241 84

Energy-dependent Ca2+ uptake was characterized in vesicles derived from rat submandibular salivary glands. Ca2+ transport was stimulated by submicromolar levels of Ca2+, reached a plateau at 1-20 microM Ca2+ then again increased as the Ca2+ concentration rose to millimolar levels. Ruthenium red (2.5 microM) was used to resolve this pattern of uptake into two components: ruthenium red-insensitive Ca2+ transport occurs in the presence of the dye, is stimulated by submicromolar Ca2+ concentrations and reaches a maximum steady state at about 1 microM Ca2+. The distribution of ruthenium red-insensitive Ca2+ uptake in membrane subfractions obtained by differential centrifugation is positively (r = 0.717) and significantly (p = 0.001) correlated with the distribution of membrane-bound RNA in the same subfractions. Ca2+ uptake which is abolished by ruthenium red is greatest at millimolar Ca2+ concentrations. Its distribution is positively (r = 0.828) and significantly (p = 0.0001) correlated with the cytochrome-c oxidase activity of the membrane subfractions but is unrelated to the distribution of particulate RNA and is negatively correlated with Na+-K+ ATPase activity. We conclude that vesicles derived from the endoplasmic reticulum of rat submandibular glands actively transport Ca2+ by a ruthenium red-insensitive mechanism which is stimulated at Ca2+ concentrations typical of the cytosol. Membranes derived from mitochondria also sequester Ca2+ but by a mechanism which is inhibited by ruthenium red and which reaches its maximum steady state capacity at relatively high Ca2+ concentrations.
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PMID:Characterization and localization of two forms of active Ca2+ transport in vesicles derived from rat submandibular glands. 242 Apr 66

2,4,5-Trichlorophenoxyacetic acid (2,4,5-T) reduced the uptake of 5-hydroxy-3-indoleacetic acid (5-HIAA) by the choroid plexus in a dose-related manner, while treatment with quinolinic acid at comparable concentrations did not inhibit 5-HIAA uptake. The role of carrier-mediated transport in the clearance of 5-HIAA from cerebrospinal fluid (CSF) was also evaluated in vivo by ventriculocisternal perfusion. Steady-state clearance of 5-HIAA from CSF exceeded that of inulin and was reduced competitively in the presence of 2,4,5-T. However, the clearance was not affected by quinolinic acid. The effect of 2,4,5-T on transport enzyme systems was also studied by electron microscopic cytochemistry. Na+-K+-ATPase and cytochrome oxidase activities in the choroid plexus were reduced by 2,4,5-T. Since this transport system in the choroid plexus is normally responsible for the excretion of the serotonin metabolite from the brain to the plasma, accumulation of endogenously produced organic acids in the CSF and the brain, secondary to reduced clearance by the choroid plexus, could be a contributing factor in the development of neurotoxicity.
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PMID:Effects of 2,4,5-trichlorophenoxyacetic acid and quinolinic acid on 5-hydroxy-3-indoleacetic acid transport by the rabbit choroid plexus: pharmacology and electron microscopic cytochemistry. 244 18

Sea urchin sperm respond to egg factors with changes in the ionic permeability of their plasma membrane. It has been previously shown that plasma membranes isolated preferentially from sea urchin sperm flagella respond to egg jelly increasing their Ca2+ and Na+ uptake (Darszon et al. (1984) Eur. J. Biochem. 144, 515-522). However, the egg jelly induced acrosome reaction occurs in the sperm head, and there is evidence for an heterogeneous distribution of plasma membrane components within the various regions of this cell. We here report a method for purifying sperm head membranes using positively charged beads according to Jacobson (1977) Biochim. Biophys. Acta 471, 331-335). Under the transmission electron microscope these membranes appeared homogeneous and apparently free of internal membranes. The yield of the preparation was 0.9% of the total protein in the sperm homogenate. The preparation contained less than 5% of the mitochondrial marker cytochrome oxidase, and 10% of the total DNA/mg protein. Surface labeling with 125I indicated a 2.5-3-fold enrichment in specific activity of the head membranes with respect to whole sperm. The SDS band pattern and the lipid composition of this preparation were different from those of isolated flagellar membranes. Phosphatidylcholine was higher in the head membranes, while phosphatidylserine and phosphatidylethanolamine were lower. The head membranes displayed a 1.7-2.3-fold higher Ca2+-ATPase activity and a 2.5-fold lower Na+/K+-ATPase activity, than the flagellar membranes. These results are consistent with a heterogeneous distribution of membrane components along the sea urchin sperm plasma membranes. Isolated head membranes sonicated in the presence of soybean phospholipid liposomes responded to egg jelly with a species-specific increase in Ca2+ and Na+ uptake. As in whole sperm, Ca2+ uptake was inhibited by the Ca2+ channel blocker nisoldipine. A close analog of this compound, [3H]nitrendipine, binds with high affinity to head membranes in a saturable, reversible manner, showing a Kd and Bmax of 31 nM and 5.3 pmol/mg protein, respectively.
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PMID:Sea urchin sperm head plasma membranes: characteristics and egg jelly induced Ca2+ and Na+ uptake. 245 36

Cytochrome c oxidase was isolated from Paracoccus denitrificans as a two-subunit enzyme. Chymotrypsin-catalyzed proteolysis reduced the molecular weight of each subunit by about 8000. The spectral properties of this preparation, as well as its Km for cytochrome c(1.7 muM), remained unchanged with respect to the native enzyme. Vmax was reduced by about 55% when assayed in Triton X-100 or in Triton X-100 supplemented with asolectin. Following further proteolysis by Staphylococcus aureus V8 protease, subunit I remained unchanged as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, whereas subunit II was split into small peptides. These were removed by ion-exchange high-performance liquid chromatography. The one-subunit enzyme had an apparent molecular weight of 43,000. The reduction of molecular weight was also confirmed by the diminution of the ultraviolet/Soret absorption ratio. This value was 1.8-2.1 for the native enzyme and 1.3-1.5 for the one-subunit enzyme. The spectral properties (including the spectrum CO reduced minus reduced) were not modified by the proteolytic treatment, indicating that cytochromes a and a3 were present in equal amounts. The lack of spectral alteration and the known close association of the copper B atom with cytochrome a3 suggest that copper B is also contained within the one-subunit enzyme. The Km of the one-subunit oxidase was similar to that of the two-subunit enzyme; Vmax was decreased by about 50%. The activity of the one-subunit oxidase had a salt-dependent maximum at 30 mM KCl, almost identical with that of the undigested enzyme, and was inhibited by micromolar concentrations of KCN.
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PMID:Preparation of a one-subunit cytochrome oxidase from Paracoccus denitrificans: spectral analysis and enzymatic activity. 246 6


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