Cytochrome System Research Articles

Determination of beta-endorphins in alcoholic patients in the acute stage of intoxications: Relation with naloxone therapy: (Barret, L., F. Bourhis, H. Buffet, V. Danel and J. L. Debru. Drug Alcohol Depend19: 71–78, 1987.)

The number of trials looking at the gender effecton anesthetic agents is very limited. What evidence exists is not clear, but the general pattern suggests a difference in pharmacokinetics and pharmacodynamics between men and women for certain drugs. These differences may not be predictable within the same group of drugs, such as benzodiazepines; the gender effect may vary and sometimes may be completely opposite. Important gender factors, such as menopause, pregnancy, and use of oral contraceptives, may affect the pharmacokinetics and dynamics of drugs significantly. Difference in body weight and composition alone result in significant pharmacokinetic differences in volume of distribution, initial plasma concentration, organ blood flow, rate of redistribution, and rate of filtration by the kidney. The intrinsic activity of the cytochrome system appears to be affected by gender: The activity of CYP3A4 is 1.4 times greater in women than men, with the resultant increased metabolism of certain drugs in women. One possible explanation for this increased intrinsic activity in women may be the interaction of the sex steroids with the cytochrome systems. Increased sensitivity to drugs may result from interaction of the sex steroids with receptors such as the μ-opioid receptors. The sex hormones may affect other intrinsic substances such as beta-endorphins. For example, beta-endorphin levels are increase in pregnancy and along with progesterone are thought to result in the decreased MAC associated with pregnancy. Clearly, further studies are needed to identify which drugs are affected by gender as well as the causes for these differences. Last, how big these differences are and to what degree they are clinically significant must be determined.

Mycelial- to yeast-phase transitions of the dimorphic fungi Blastomyces dermatitidis and Paracoccidioides brasiliensis.

The physiological changes that occur during the mycelial- to yeast-phase transitions induced by a temperature shift from 25 to 37 degrees C of cultures of Blastomyces dermatitidis and Paracoccidioides brasiliensis can be divided into three stages. The triggering event is a heat-related insult induced by the temperature shift which results in partial uncoupling of oxidative phosphorylation and declines in cellular ATP levels, respiration rates, and concentrations of electron transport components (stage 1). The cells then enter a stage in which spontaneous respiration ceases (stage 2), and finally, there is a shift into a recovery phase during which transformation to yeast morphology occurs (stage 3). Cysteine is required during stage 2 for the operation of shunt pathways which permit electron transport to bypass blocked portions of the cytochrome system. The mycelial- to yeast-phase transitions of these two fungi are very similar to that of Histoplasma capsulatum. Therefore, these three dimorphic fungal pathogens have evolved parallel mechanisms to adjust to the temperature shifts which induce these mycelial- to yeast-phase transitions.

Polarographic determination of mitochondrial respiration in Gastrothylax crumenifer

ABSTRACTThe oxidative metabolism of Gastrothylax crumenifer mitochondrial fractions was assayed polarographically at 30°C in the presence of various substrates. Succinate was most readily oxidized, malate and pyruvate were oxidized at subsantially lower retes. The spcific inhibitors such as malonate, KCN, NaN3, oxaloacetate, salicylhydroxamic acid and oligomycin effectively affected the mitochondrial oxygen consumption. The results indicate the presence of oxidative phosphorylation and cytochrome systems. Mitochondrial ATPase was found to be active.

ChemInform Abstract: Membrane‐Bound Cytochrome P‐450 Mimic. Polymerized Vesicles as Microreactors.

AbstractA synthetic model system of cytochrome P‐450 which incorporates all features of the natural enzyme system is described.

Characterization of the cytochrome system of a nitrogen-fixing strain of a sulfate-reducing bacterium: Desulfovibrio desulfuricans strain Berre-Eau.

Two c-type cytochromes were purified and characterized by electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopic techniques, from the sulfate-reducer nitrogen-fixing organism, Desulfovibrio desulfuricans strain Berre-Eau (NCIB 8387). The purification procedures included several chromatographic steps on alumina, carboxymethylcellulose and gel filtration. A tetrahaem and a monohaem cytochrome were identified. The multihaem cytochrome has visible, EPR and NMR spectra with general properties similar to other low-potential bis-histidinyl axially bound haem proteins, belonging to the class of tetrahaem cytochrome c3 isolated from other Desulfovibrio species. The monohaem cytochrome c553 is ascorbate-reducible and its EPR and NMR data are characteristic of a cytochrome with methionine-histidine ligation. Their properties are compared with other homologous proteins isolated from sulfate-reducing bacteria.

Differential mitochondrial gene expression between slender and stumpy bloodforms of Trypanosoma brucei

Bloodforms of Trypanosoma brucei lack complete cytochrome and Krebs cycle systems but a fully functional mitochondrial respiratory system is elaborated upon differentiation to procyclics. We previously found differential expression of some mitochondrial genes, at the level of transcript abundance, between these two life cycle stages. We report here that mitochondrial genes are also differentially expressed between the two morphological types of bloodforms. Some transcripts that are more abundant in procyclics than slender bloodforms are intermediate in abundance in stumpy bloodforms. Most major mitochondrial transcripts are more abundant in stumpy than slender bloodform RNA; some are also more abundant than in procyclic RNA. Transcripts from protein coding genes are increased in abundance to varying degrees. Treatment with difluoromethylornithine, which induces a stumpy morphology, produces transcript abundance patterns similar to those in naturally occurring stumpy bloodforms. Stumpy bloodforms also have a decrease in tubulin transcript abundance, consistent with their nondividing character and smaller flagellum. These studies suggest that molecular events associated with mitochondrial development during the differentiation from bloodforms to procyclics can be initiated in the bloodstream, and that maxicircle transcript abundances are individually modulated during the life cycle.

Phenotypic characteristics of a slow-growing, nongerminating variant of Candida albicans.

Some of the phenotypic characteristics of a slow-growing, nongerminating variant of a commonly studied strain of Candida albicans are described. The variant arose as a chance isolate. The rate of occurrence was about 0 X 1% and the reversion rate was about 1 per 10(6) cells. The colony size was typically smaller than that of the parent and the yeast cells tended not to separate from one another so that catenulate strands of cells (pseudohyphae) were formed. Under standard conditions the generation time of the small-colony variant in liquid shake cultures was about twice that of the parental strain. Growth of the variant was suppressed by antimycin A, indicating that the small colony form was not the consequence of a defect in the cytochrome system. The colony size of the variant was not influenced by chlorobenzotriazole, which suggested that adenine metabolism was not involved in the small-colony phenotype. The pseudohyphal growth pattern was not relieved by high concentrations of utilizable carbohydrates, which means the catenulate microscopic appearance of the yeast cells was not simply an exaggeration of the normal growth pattern of isolates of C. albicans but more probably represented the growth of a cell-cycle mutant defective at the cell separation step. The cytoplasmic proteins of the variant and the parent were very similar though some unique peptides were displayed by each.

31] Cooperative proton-transfer reactions in the respiratory chain: Redox Bohr effects

Publisher Summary This chapter describes direct measurement of redox Bohr effects in electron carriers of the respiratory chain. Redox Bohr effects can be directly analyzed by measuring pH changes associated with oxidation or reduction of redox carriers. Artificial electron carriers such as ferricyanide-ferrocyanide can be used as oxidant or reductant. The redox Bohr effects can be measured by monitoring pH changes associated with oxidation of components of the respiratory chain by oxygen. The aerobic oxidation method for measurement of redox Bohr effects in the cytochrome system of mitochondria can be used to measure Bohr effects in purified cytochrome- c reductase and cytochrome- c oxidase. The redox centers of the reductase are reduced by succinate, since there are traces of succinate dehydrogenase always present in the purified enzyme. Aerobic oxidation of the reduced centers is affected through traces of purified cytochrome- c oxidase and cytochrome c added to the system.

Alternative cyanide- and antimycin A-insensitive respiratory system in Sporobolomyces red yeasts.

Sporobolomyces ruberrimus is insensitive to antimycin A which is a respiratory inhibitor of the cytochrome system, as cyanide is. When this red yeast was cultured in the presence of antimycin A, the growth curve showed the same pattern as that of the normal culture in the absence of it, but the growth mass was only about 70% of that of the normal culture. The antimycin A-insensitive and cyanide-insensitive respiration of Sp. ruberrimus was inhibited by pyrocatechol and salicylhydroxamic acid. Sporobolomyces red yeasts have two characteristic terminal oxidase systems; one is a cytochrome oxidase system and the other is a cyanide- and antimycin A-insensitive oxidase system. The proportions of the two respiratory systems differed among the species and strains of Sporobolomyces red yeasts examined.

Treatment of acute carbon monoxide poisoning with hyperbaric oxygen: A review of 115 cases

From January 1978 through March 1984, 115 cases of acute carbon monoxide poisoning were treated with hyperbaric oxygen. Exposure resulted from accidental sources (n = 39), attempted suicide (n = 47), and smoke inhalation (n = 29). Forty-one victims were never unconscious, 30 victims were unconscious at the scene but awoke before arriving at the hospital, and 44 victims were unconscious in the ED. Eleven patients (9.6%) died, and two victims (1.9% of the survivors) experienced major sequelae. All these patients were comatose on arrival. The remaining 102 patients recovered fully. Carboxyhemoglobin levels did not correlate with clinical findings, thereby demonstrating the variability between carbon monoxide exposure and impairment of the cellular cytochrome system. Hyperbaric oxygen therapy facilitates the rapid removal of carbon monoxide from the hemoglobin and cytochrome systems while reoxygenating compromised tissues, and it can be an effective treatment in reducing mortality and morbidity.

Characterization of cytochrome c3 from the thermophilic sulfate reducer Thermodesulfobacterium commune.

A c3 type cytochrome has been purified from the thermophilic, non-spore-forming, sulfate-reducing bacterium Thermodesulfobacterium commune. The purified protein was homogeneous as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, gel filtration, and isoelectric focusing. A pI of 6.83 was observed. The molecular weight of the cytochrome was estimated to be ca. 13,000 from both gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The hemoprotein exhibited absorption maxima at 530, 408.5, and 351 nm in the oxidized form and 551.5 (alpha band), 522.5 (beta band), and 418.5 nm (gamma band) in the reduced form. The extinction coefficients of T. commune cytochrome c3 were 130,000, 74,120, and 975,000 M-1 cm-1 at 551.5, 522.5, and 418.5 nm, respectively. It contains four hemes per molecule, on the basis of both the iron estimation and the extinction coefficient value of its pyridine hemochrome. The amino acid composition showed the presence of eight cysteine residues involved in heme binding. T. commune cytochrome c3 had low threonine, serine, and glycine contents and high glutamic acid and hydrophobic residue contents. The electrochemical study of T. commune cytochrome c3 by cyclic voltammetry and differential pulse polarography has shown that the cytochrome system behaves like a reversible system. Four redox potential values at Eh1 = -0.140 +/- 0.010 V, Eh2 = Eh3 = Eh4 = -0.280 +/- 0.010 V have been determined. T. commune cytochrome c3, which acts as the physiological electron carrier of hydrogenase, is similar in most respects to the multiheme low-potential cytochrome c3 which is characteristic of the genus Desulfovibrio.

The mechanism of proton translocation by the cytochrome system of mitochondria. Characterization of proton-transfer reactions associated with oxidoreductions of terminal respiratory carriers.

A direct kinetic analysis is presented of rapid proton-releasing reactions at the outer or C-side of the membrane, in ox heart and rat liver mitochondria, associated with aerobic oxidation of reduced terminal respiratory carriers in the presence of antimycin. Valinomycin plus K+ enhances the rate of cytochrome c oxidation and the rate and extent of H+ release. In the presence of valinomycin the leads to H+/e- ratio, computed on the basis of total electron flow from respiratory carriers to oxygen, varies with pH, remaining always lower than 1, and is unaffected by N-ethylmaleimide. 2-Heptyl-4-hydroxyquinoline N-oxide and 5-(n-undecyl)-6-hydroxy-4,7-dioxobenzothiazole, at concentrations which inhibit in the presence of antimycin the oxygen-induced reduction of b cytochromes, cause also a marked depression of the H+ release associated with aerobic oxidation of terminal respiratory carriers. Aerobic oxidation of the cytochrome system in mitochondria and of isolated b-c1 complex and cytochrome c oxidase results in scalar proton release from ionizable groups (redox Bohr effects). In mitochondria and submitochondrial particles, about 70% of the oxidoreductions of the components of the cytochrome system are linked to scalar proton transfer by ionizable groups. In isolated b-c1 complex scalar proton transfer, resulting from redox Bohr effect, amounts to 0.9H+ per Fe-S protein (190 muT). In isolated cytochrome c oxidase, Bohr protons amount to 0.8 per haem a + a3. The results presented indicate that the H+ release from mitochondria during oxidation of terminal respiratory carriers derives from residual antimycin-insensitive electron flow in the quinone-cytochrome c span and from redox Bohr effects in the b-c1 complex and cytochrome c oxidase. There is no sign of proton pumping by cytochrome oxidase during its transition from the reduced to the active 'pulsed' state and the first one or two turnovers.

The cytochrome system of sea urchin eggs and embryos

The cytochrome system in eggs and embryos of the sea urchin, Hemicentrotus pulcherrimus, was investigated. Difference spectra of the mitochondrial fraction demonstrated the presence of a complete cytochrome system in unfertilized eggs. Cytochrome levels and the activities of respiratory enzymes were measured in crude extracts of eggs both before and after fertilization. Unfertilized eggs contained cytochromes aa 3, b, and c + c 1 in a ratio of 1.0:1.8:0.7. Gastrulae contained almost the same amount of cytochromes aa 3and b as unfertilized eggs. However, the amount of cytochrome c + c 1 in gastrulae was 1.5 times greater than that in unfertilized eggs. The activity of cytochrome oxidase remained unchanged during development. No cytochrome oxidase inhibitor was found in unfertilized eggs. Both antimycin A-sensitive and insensitive NADH-cytochrome c reductase activities increased during development. The activity of succinate-cytochrome c reductase increased during early development, reached a temporary plateau, and then declined at the pluteus stage. These results are discussed in relation to the increase of respiration during early development.

Ubiquinone pool behaviour in plant mitochondria

A kinetic analysis of oxygen uptake was carried out in order to investigate the role of ubiquinone pool behaviour in plant mitochondria. The interaction of the external NADH dehydrogenase with either the cytochrome system or the cyanide-insensitive oxidase was examined under various conditions. The involvement of a ubiquinone pool can be deduced from the shape of the titration curve as the appropriate oxidase system is inhibited, by antimycin A for the cytochrome system and salicylhydroxamic acid for the cyanide-insensitive oxidase, at different activities of the NADH dehydrogenase. In the absence of a specific inhibitor, the turnover of the external NADH dehydrogenase was adjusted using a novel NADH-generating system involving the recycling of a low concentration of NAD + by added glucose 6-phosphate dehydrogenase in the presence of substrate. The results show that ubiquinone pool behaviour is observed between the external NADH dehydrogenase and either the cytochrome b- c 1 complex or the cyanide-insensitive oxidase. However, there is a substantial departure from pool behaviour during the simultaneous operation of both oxidases.

Sulfhydryl induced respiratory "shunt" pathways and their role in morphogenesis in the fungus, Histoplasma capsulatum.

When the mycelial to yeast transition of the dimorphic fungus Histoplasma capsulatum is induced by a temperature shift from 25 to 37 degrees C, the activities of the cytochrome system and the alternate oxidase decrease in parallel over the first 24 to 40 h (stage 1 of the transition). The decrease in activity of the cytochrome system is correlated with extensive decreases in the amounts of cytochromes b, c, and aa3, assayed spectrophotometrically. After 40 h, the cells enter a dormant phase (stage 2 of the transition) and cysteine or other sulfhydryl-containing compounds are required to reactivate mitochondrial respiration. This reactivation is due to the establishment of shunt pathways which bypass blocked segments of the electron transport system. The "shunt" pathways operate normally in mycelia grown at 25 degrees C, but are shut down during the transition, possibly because of depletion of intracellular cysteine. The longstanding observation that cysteine is required to progress beyond the initial stages of the morphological transition may be due, at least in part, to the reactivation of these "shunt" pathways.

Biosynthesis of Ubiquinone

Publisher Summary This chapter discusses the biosynthesis of ubiquinone. Ubiquinone serves as a lipid-soluble electron carrier in the membrane-bound electron transport chains of both prokaryotes and eukaryotes. Eighty-five percent of cell ubiquinon is located in the mitochondria or equivalent membrane system. The structure of ubiquinone and the dimensions of various ubiquinone homologs with respect to a typical membrane bilayer are diagrammatically represented in the chapter. During respiration, reducing equivalents entering the electron transport chain are transferred through a series of redox components from pyridine nucleotides and flavoproteins to ubiquinone, and then by the cytochromes to oxygen. Ubiquinone provides a linkage between the two-electron transport enzymes and the one-electron cytochrome system through semiquinone formation. Acetone extraction of the endogenous ubiquinone disrupts electron transport. The readdition of ubiquinone-9 to ubiquinone-depleted mitochondria restores both cyanide and antimycin sensitivity to levels approaching the unextracted systems. The first step in ubiquinone biosynthesis is the alkylation of 4-hydroxybenzoate by polyprenyl pyrophosphate. The initial stages of the biosynthesis of polyprenyl pyrophosphate are accomplished in the cytosol and the product is transported through the external mitochondrial membrane to the internal membrane where the alkylation reaction occurs.

To the Editor.-Reply

—We appreciate the comments by Dr Feagin and Mr Dorr who both suggest alternative mechanisms for the severe neutropenia seen in patients treated with carmustine and cimetidine. Inhibition of the cytochrome system or alteration of hepatic blood flow by cimetidine may potentially delay the clearance of chemotherapeutic agents. This could increase their toxic or therapeutic effects. 1 In our practice, we have seen one patient with a reversible neutropenia and another with severe aplastic anemia that followed ingestion of cimetidine. Since these patients were not receiving cytotoxic drugs, it seems likely that cimetidine can act to suppress marrow function. Further investigation should help to resolve the question of direct v indirect effect on the hematopoietic stem cell.

Occult Carbon Monoxide Poisoning

Carbon monoxide (CO) is a colorless, tasteless, and odorless product of incomplete fuel combustion. It exerts its pathophysiologic effect by its avid binding to hemoglobin, with consequent displacement of oxygen. Tissue hypoxia is worsened by the deleterious effect on oxyhemoglobin dissociation and the direct effects of CO on the cytochrome system. Symptoms of CO poisoning are related to the blood carboxyhemoglobin level, time course of exposure, respiratory rate, age of the patient, and presence of underlying illness. Blood carboxyhemoglobin levels are dependent on the ambient CO level, which, in turn, is determined by the source of CO production and meteorologic and climatic factors. 1 The symptoms and signs of CO poisoning are extremely varied. Nonspecific symptoms, eg, headache, nausea, vomiting, fatigue, and malaise, are common. Because of the fixed oxygen needs of the circulatory and nervous systems, cardiovascular and neurologic symptoms are frequent. However, virtually every organ system may be

Occult carbon monoxide poisoning

Carbon monoxide (CO) is a colorless, tasteless, and odorless product of incomplete fuel combustion. It exerts its pathophysiologic effect by its avid binding to hemoglobin, with consequent displacement of oxygen. Tissue hypoxia is worsened by the deleterious effect on oxyhemoglobin dissociation and the direct effects of CO on the cytochrome system. Symptoms of CO poisoning are related to the blood carboxyhemoglobin level, time course of exposure, respiratory rate, age of the patient, and presence of underlying illness. Blood carboxyhemoglobin levels are dependent on the ambient CO level, which, in turn, is determined by the source of CO production and meteorologic and climatic factors.¹ The symptoms and signs of CO poisoning are extremely varied. Nonspecific symptoms, eg, headache, nausea, vomiting, fatigue, and malaise, are common. Because of the fixed oxygen needs of the circulatory and nervous systems, cardiovascular and neurologic symptoms are frequent. However, virtually every organ system may be

Cytokinin Modification of Mitochondrial Function

6-Benzylaminopurine, 6-(Delta(2)-isopentenylamino)purine, 6-furfurylaminopurine, rotenone, and antimycin A inhibited oxidation of NADH by mitochondrial sonicates or submitochondrial particles (but not by intact mitochondria) from pea (Pisum sativum L., cult. Alaska) stems and mung bean (Vigna radiata L. Wilczak) hypocotyls. The above purine cytokinins can interfere with electron transport from NADH to the cytochrome system in the inner mitochondrial membrane. Adenine did not inhibit oxidation by sonicated mitochondria, and zeatin was almost ineffective. Zeatin scarcely inhibited state 3 malate respiration by intact mitochondria, but the O-formyl and O-n-propionyl esters of zeatin and the O-acetyl ester of 2-chlorozeatin were more active. Perhaps zeatin is ineffective because it does not get into the inner membranes of the isolated mitochondria, whereas the esters and other cytokinins mentioned above do. N-4-(2-chloropyridyl)-N'-Phenylurea, which has cytokinin-like effects on plant growth and development, inhibited NADH oxidation by sonicated mitochondria. It also inhibited malate, succinate, and NADH oxidation by intact mitochondria; in contrast, the latter two oxidations were not decreased by purine cytokinins.The benzyl, isopentenyl, and furfuryl aminopurines inhibited malate (but not succinate) oxidation by rat liver mitochondria, if ADP was present. In the absence of ADP, these cytokinins promoted succinate (but not malate) oxidation. Zeatin and adenine had slight, if any, effect in either situation.