Tetramethyl-p-phenylenediamine Dihydrochloride Research Articles

Analysis of sulfonamides, trimethoprim, fluoroquinolones, quinolones, triphenylmethane dyes and methyltestosterone in fish and shrimp using liquid chromatography-mass spectrometry.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) screening method is described for the detection and identification of 26 veterinary drugs in fish and other aquaculture products. The analytes include: 13 sulfonamides, trimethoprim, 3 fluoroquinolones, 3 quinolones, 3 triphenylmethane dyes, 2 leuco dye metabolites, and 1 hormone. In this method, tissue is mixed with EDTA-McIlvaine buffer, double-extracted with acetonitrile, p-toluenesulfonic (p-TSA) acid and N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride (TMPD), and analyzed using LC-MS/MS. Inclusion of p-TSA and TMPD in the extraction procedure was critical for simultaneous analysis of dyes with the other groups of veterinary drugs. The proposed procedure was validated as both a quantitative analysis method and as a semi-quantitative screening method for multiple fish and shrimp matrices. The method was applied to eight types of fish (catfish, eel, pangasius, sablefish, tilapia, swai, salmon, and trout) and shrimp at the appropriate level of concern: 10ng/g for sulfonamides, trimethoprim, and quinolones, 5ng/g for fluoroquinolones, 1ng/g for dyes and their metabolites, and 0.4ng/g for methyltestosterone.

Biochemical and Biophysical Characterization of the Two Isoforms of cbb3-Type Cytochrome c Oxidase from Pseudomonas stutzeri

The cbb3-type cytochrome c oxidases (cbb3-CcOs) are members of the heme-copper oxidase superfamily that couple the reduction of oxygen to translocation of protons across the membrane. The cbb3-CcOs are present only in bacteria and play a primary role in microaerobic respiration, being essential for nitrogen-fixing endosymbionts and for some human pathogens. As frequently observed in Pseudomonads, Pseudomonas stutzeri contains two independent ccoNO(Q)P operons encoding the two cbb3 isoforms, Cbb3-1 and Cbb3-2. While the crystal structure of Cbb3-1 from P. stutzeri was determined recently and cbb3-CcOs from other organisms were characterized functionally, less emphasis has been placed on the isoform-specific differences between the cbb3-CcOs. In this work, both isoforms were homologously expressed in P. stutzeri strains from which the genomic version of the respective operon was deleted. We purified both cbb3 isoforms separately by affinity chromatography and increased the yield of Cbb3-2 to a similar level as Cbb3-1 by replacing its native promoter. Mass spectrometry, UV-visible (UV-Vis) spectroscopy, differential scanning calorimetry, as well as oxygen reductase and catalase activity measurements were employed to characterize both cbb3 isoforms. Differences were found concerning the thermal stability and the presence of subunit CcoQ. However, no significant differences between the two isoforms were observed otherwise. Interestingly, a surprisingly high turnover of at least 2,000 electrons s(-1) and a high Michaelis-Menten constant (Km ~ 3.6 mM) using ascorbate-N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride (TMPD) as the electron donor were characteristic for both P. stutzeri cbb3-CcOs. Our work provides the basis for further mutagenesis studies of each of the two cbb3 isoforms specifically.

Skeletal muscle mitochondrial dysfunction during chronic obstructive pulmonary disease: central actor and therapeutic target

Muscle dysfunction is a common complication and an important prognostic factor in chronic obstructive pulmonary disease (COPD). As therapeutic strategies are still needed to treat this complication, gaining more insight into the process that leads to skeletal muscle decline in COPD appears to be an important issue. This review focuses on mitochondrial involvement in limb skeletal muscle alterations (decreased muscle mass, strength, endurance and power and increased fatigue) in COPD. Mitochondria are the main source of energy for the cells; they are involved in production of reactive oxygen species and activate an important pathway that leads to apoptosis. In COPD patients, skeletal muscles are characterized by decreased mitochondrial density and biogenesis, impaired activity and coupling of mitochondrial respiratory chain complexes, increased mitochondrial production of reactive oxygen species and, possibly, increased apoptosis. Of particular interest, a sedentary lifestyle, hypoxia, hypercapnia, tobacco smoking, corticosteroid therapy and, possibly, inflammation participate in this mitochondrial dysfunction, which is accessible to conventional therapies, such as exercise and tobacco cessation, as well as, potentially, to more innovative approaches, such as antioxidant treatment and supplementation with polyunsaturated fatty acids.

Remote and local ischemic preconditioning equivalently protects rat skeletal muscle mitochondrial function during experimental aortic cross-clamping

This study investigated whether remote (rIPC) and local ischemic preconditioning (IPC) similarly limit skeletal muscle dysfunction induced by aortic cross-clamping. Rats were divided in three groups: the sham-operated control group (C) underwent surgery without clamping. The ischemia-reperfusion group (IR) had 3 hours of ischemia induced by aortic clamping and collateral vessels ligation, followed by 2 hours of reperfusion. The IPC group had, before prolonged ischemia, three bouts of 10 minutes of ischemia and 10 minutes of reperfusion on the right hind limb. Thus, right hind limbs had local IPC and left hind limbs had rIPC. Complexes I, II, III, and IV activities of the mitochondrial respiratory chain of the gastrocnemius muscle were measured using glutamate-malate (V(max)), succinate (V(succ)), and N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride (TMPD)-ascorbate (V(TMPD)). Expressions of genes involved in apoptosis (Bax, Bcl-2) and antioxidant defense (superoxide dismutase 1 [SOD 1], SOD2, glutathione peroxidase [GPx]) were determined by quantitative real-time polymerase chain reaction. Glutathione was also measured. Right and left hind limb mitochondrial functions were similar in controls and after IR. IR reduced V(max) (-21.2%, 6.6 ± 1 vs 5.2 ± 1 μmol O(2)/min/g dry weight, P = .001), V(succ) (-22.2%, P = .032), and V(TMPD) (-22.4%, P = .033), and increased Bax (63.4%, P = .020) and Bax/Bcl-2 ratio (+84.6%, P = .029). SODs and GPx messenger RNA were not modified, but glutathione tended to be decreased after IR. Local IPC and rIPC counteracted similarly these deleterious effects, restoring mitochondrial maximal oxidative capacities and normalizing Bax, the Bax/Bcl-2 ratio, and glutathione. Remote ischemic preconditioning protection against IR injury is equivalent to that achieved by local IPC. It might deserve a broader use in clinical practice. Acute and chronic ischemia induce mitochondrial dysfunction in human skeletal muscles, and improving muscle mitochondrial function improves subjects’ status. Compared with local ischemic preconditioning (IPC), remote IPC (rIPC) appears easier to perform and is safer for the vessel and territory involved in ischemic injury. This study demonstrates that the muscle protection afforded by rIPC is equivalent to that achieved by IPC. Acknowledging that IPC procedures should be specifically adapted to patient characteristics to be successful, our results support a broader use of rIPC in the setting of vascular surgery.

Mononuclear and Binuclear Fe(III), Co(II), Ni(II), and Cu(II) Complexes of 3,4′-Dihydroxyazobenzene-3′,4-dicarboxylic Acid and 3-Carboxy-4-hydroxyphenylazo-3-carboxy-4-hydroxynaphthalene

Fe(III), Co(II), Ni(II), and Cu(II) complexes of the title azodyes have been synthesized and characterized by elemental analysis, molar conductance, TGA, DTA, magnetic susceptibility measurements, IR, electronic and ESR spectral studies. The spectral studies suggest an octahedral geometry for Fe(III) and Co(II) complexes but a square planar geometry for Ni(II) and Cu(II) complexes. The kinetics of the catalysed oxidation of N,N,N′,N′-tetramethyl-p-phenylenediamine dihydrochloride (TMPPD) with mononuclear and binuclear copper complexes were studied to check the activity of these copper complexes in oxidizing organic amines. The electrochemical behaviour of the metal complexes was studied using DC polarography and cyclic voltammetry. Antimicrobial activity of the azo compounds and its complexes have been tested against different microorganisms.

Mitochondrial respiration at low levels of oxygen and cytochrome c

In the intracellular microenvironment of active muscle tissue, high rates of respiration are maintained at near-limiting oxygen concentrations. The respiration of isolated heart mitochondria is a hyperbolic function of oxygen concentration and half-maximal rates were obtained at 0.4 and 0.7 μM O2 with substrates for the respiratory chain (succinate) and cytochrome c oxidase [N, N, N, N', N'-tetramethyl-p-phenylenediamine dihydrochloride (TMPD) + ascorbate] respectively at 30 °C and with maximum ADP stimulation (State 3). The respiratory response of cytochrome c-depleted mitoplasts to external cytochrome c was biphasic with TMPD, but showed a monophasic hyperbolic function with succinate. Half-maximal stimulation of respiration was obtained at 0.4 μM cytochrome c, which was nearly identical to the high-affinity K'm for cytochrome c of cytochrome c oxidase supplied with TMPD. The capacity of cytochrome c oxidase in the presence of TMPD was 2-fold higher than the capacity of the respiratory chain with succinate, measured at environmental normoxic levels. This apparent excess capacity, however, is significantly decreased under physiological intracellular oxygen conditions and declines steeply under hypoxic conditions. Similarly, the excess capacity of cytochrome c oxidase declines with progressive cytochrome c depletion. The flux control coefficient of cytochrome c oxidase, therefore, increases as a function of substrate limitation of oxygen and cytochrome c, which suggests a direct functional role for the apparent excess capacity of cytochrome c oxidase in hypoxia and under conditions of intracellular accumulation of cytochrome c after its release from mitochondria.

Pyrrolnitrin from Burkholderia cepacia: antibiotic activity against fungi and novel activities against streptomycetes.

A bacterial strain identified as Burkholderia cepacia NB-1 was isolated from water ponds in the botanical garden in Tübingen, Germany, and was found to produce a broad spectrum phenylpyrrole antimicrobial substance active against filamentous fungi, yeasts and Gram-positive bacteria. In batch culture containing glycerol and L-glutamic acid, the isolate NB-1 produced the antibiotic optimally late in the growth phase and accumulated a main portion in their cells. Isolation and purification of the antibiotic from Burkholderia (Pseudomonas) cepacia NB-1 by acetone extraction, gel filtration on Sephadex LH-20 and preparative HPLC yielded 0.54 mg l-1 of a pure substance. Spectroscopic data (HPLC, MS and NMR) confirmed that the compound was pyrrolnitrin [3-chloro-4-(2'-nitro-3'-chloro-phenyl) pyrrole]. Pyrrolnitrin has an inhibitory effect on the electron transport system, as demonstrated by isolated mitochondria from Neurospora crassa 74 A. This inhibition was relieved by N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride (TMPD), indicating that pyrrolnitrin blocked the electron transfer between the dehydrogenases and the cytochrome components of the respiratory chain. Among Gram-positive bacteria, pyrrolnitrin was most active against certain Streptomyces species, especially S. antibioticus, which has not previously been described in the literature. In the presence of pyrrolnitrin, aerial mycelium and spore formation of Strep. antibioticus was suppressed, although growth continued via substrate mycelium. The new findings of inhibition of streptomycetes and their secondary metabolism by pyrrolnitrin may contribute to the fact that Pseudomonas species predominate in soil and compete even with antibiotic-producing Streptomyces.

Inhibition of cytochrome oxidase by dibucaine

Dibucaine-HCl inhibited mitochondrial cytochrome c oxidase activity in intact mitochondria with 50% inhibition occurring at 1.1 mM dibucaine-HCl. Dibucaine-HCl did not prevent the reduction of cytochrome oxidase by ascorbate plus N, N, N′, N′-tetramethyl- p-phenylenediamine dihydrochloride (TMPD) when measured at 604 nm but prevented 50% of the absorbance change at 445 nm; dithionite reduced the oxidase completely. Dibucaine prevented binding of CO to oxidase reduced with ascorbate plus TMPD by preventing the reduction of cytochrome a 3. The midpotentials of cytochrome c and cytochrome oxidase, the visible absorbance wavelength maxima, and the position and intensity of the signals of the EPR spectrum of the oxidase were not affected. Dibucaine-HCl prevented ascorbate plus TMPD-driven reduction of the near infra-red detectable copper center associated with cytochrome a; dithionite subsequently reduced this center. Dibucaine-HCl inhibited cytochrome oxidase activity by interacting between cytochrome a and its associated copper. Since respiration was 8-fold less sensitive in submitochondrial particles, this site of inhibition is on the cytoplasmic side of the membrane.

Inhibitory effects of pentagalloylglucose on the respiratory chain of Photobacterium phosphoreum.

The activity of glucose-dependent oxygen consumption of whole cells of Photobacterium phosphoreum was inhibi6ted by purified pentagalloylglucose (1, 2, 3, 4, 6-penta-O-galloyl-β-D-glucose). Sonicated membrane vesicles were used to study the effect of the inhibitor on the electron transport activity. The activity of reduced nicotinamide adenine dinucleotide (NADH) oxidase in sonicated membrane vesicles of P. phosphoreum decreased when pentagalloylglucose was added to the assay system. The results suggested that the targets of inhibitory action were NADH dehydrogenase and terminal oxidase.The effect of the inhibitor on the terminal oxidase was compared in the case of purified terminal oxidase (cytochrome bd complex) and sonicated membrane vesicles. The oxidase activities toward ubiquinol-1 and N, N, N', N'-tetramethyl-p-phenylenediamine dihydrochloride (TMPD) in the presence of ascorbate were both inhibited by pentagalloylglucose in sonicated membrane vesicles and purified cytochrome bd complex. The inhibition of ubiquinol-1 oxidase activity in sonicated membrane vesicles and purified enzyme was of noncompetitive type. On the other hand, the inhibitions of TMPD plus ascorbate oxidase in both membrane vesicles and purified enzyme were uncompetitive. Thus, the mechanisms of inhibition of the two kinds of oxidase activities by the inhibitor were different.The inhibitory effect of tetragalloylglucose (1, 2, 3, 6-tetra-O-galloyl-β-D-glucose) on the respiratory chain was similar to that of pentagalloylglucose in the case of membrane vesicles and purified enzyme.

Inhibitory Effects of Tannic Acid on the Respiratory Chain of <I>Photobacterium phosphoreum</I>

Tannic acid inhibited the growth of Photobacterium phosphoreum in liquid culture and also decreased the viability, expressed in terms of the colony forming activity.The activity of glucose dependent oxygen consumption of whole cells was inhibited by tannic acid. It was found that the activity of reduced nicotinamide adenine dinucleotide (NADH) oxidase of the sonicated membrane of Photobacterium phosphoreum decreased when tannic acid was added to the assay system. The results suggested that the targets of tannic acid action were NADH dehydrogenase and the terminal oxidase.The inhibitory effect of tannic acid on the terminal oxidase was compared in the cases of purified terminal oxidase (cytochrome b560-d complex) and sonicated membrane vesicles. The oxidase activities toward ubiquinol-1 and N, N, N', N'-tetramethyl-p-phenylenediamine dihydrochloride (TMPD) in the presence of ascorbate were both inhibited by tannic acid in both sonicated membrane and purified cytochrome b560-d complex. The inhibition of ubiquinol-1 oxidase activity in sonicated membrane was biphasic and noncompetitive in both phases. The inhibition of the ubiquinol-1 oxidase activity of purified terminal oxidase was monophasic and noncompetitive. On the other hand, the inhibition of TMPD oxidase activity in the presence of ascorbate in both membrane vesicles and purified enzyme was uncompetitive. Thus, the mechanisms of inhibition of the two kinds of oxidase activity by tannic acid were different.

Repair of tryptophan radicals by antioxidants

Oxidizing free radicals with redox potential greater than 1 V generate indole radicals, R-Ind ⨥ and R-Ind·, as in tryptophan. These resonance-stabilized free radicals can be repaired efficiently with electron donors ( k = 5 × 10 6 − 1.3 × 10 9 dm 3 mol − s −) such as ascorbate, N, N, N′, N′-tetramethyl- p-phenylenediamine dihydrochloride (TMPD), and phenolic antioxidants. Sulfhydryl compounds, which are good H-atom donors, were found to be relatively unreactive ( k < 10 6 dm 3 mol −1s −1). These indole radicals were also found to be unreactive with oxygen ( k < 10 6 dm 3 mol −1 s −1).

Imbibitional Chilling Injury in Pollen

Chilling injury is sustained by dry pollen of Typha latifolia L. upon hydration in germination medium at 0 degrees C. This injury is evidenced as poor germination, low vigor, and depressed respiration. Isolated mitochondria showed multiple sites of impaired electron transport. Besides losses of cytochrome (Cyt) c and NAD(+), the activities of membrane-bound enzyme complexes such as Cyt oxidase, NADH-duroquinone oxidoreductase, succinate-duroquinone oxidoreductase, and malate-duroquinone oxidoreductase were severely affected.Similarly, as in isolated mitochondria, in situ tests of mitochondrial activity showed that Cyt c was partially lost from its site of action. Re-addition of the lost Cyt c to the grains restored the N,N,N',N'-tetramethyl p-phenylenediamine dihydrochloride plus ascorbate-mediated electron transport from Cyt c to O(2), but did not significantly accelerate the overall O(2) uptake. Electron flow to duroquinone in the injured grains was low, indicating that lesions at the substrate side of ubiquinone determine the rate of O(2) consumption. Leakage of NAD(+), and also of adenylate phosphates and Krebs cycle substrates out of the injured grains, was considerable.Increasing the initial moisture content of the grains strongly enhanced their resistance to cold hydration. Below 17% moisture content (fresh weight basis), the decrease in vigor closely matched the loss of NAD(+) and adenosine phosphates. Vitality was irreversibly lost by cold hydration below 10 to 12% initial moisture content.Injury to dry pollen was prevented by imbibition at 27 degrees C. Decrease of vigor and increased leakage, however, started below 20 degrees C, and complete loss of vitality occurred below 10 degrees C.These results are interpreted as evidence that loss of membrane integrity is the primary cause of imbibitional chilling injury.

Early Effects of Inorganic Lead on Immature Rat Brain Mitochondrial Respiration

Inorganic lead, added to the diet of suckling rat in high doses, produces an encephalopathy similar to that seen in the immature human. Pathologic changes of edema and hemorrhage are seen earliest and are most prominent in the cerebellum. In this study, we measured respiration in cerebral hemisphere and cerebellar mitochondria isolated from led-fed and age-matched normal rat pups. Lactating mothers were begun on ad libitum feedins containing 4% lead carbonate when their pups were 2 weeks old. Mitochondria were isolated by differential centrifugation. Oxygen consumption was measured polarographically, NAD-linked respiration was measured with oxidation of the substrate pair, glutamate and malate. Cytochrome oxidase (cytochrome c oxidase, EC. 1.9.3.1) activity was measured in the presence of tetramethyl-p-phenylenediamine dihydrochloride (TMPD) and ascorbate. Within 2 days of starting lead feedings, rat pups showed a significant loss in body weight (P less than 0.02) and, after 1 week, a significant loss in cerebral hemisphere wet weight (P less than 0.01) compared with controls. Overt encephalopathy appeared in pups from two of nine litters receiving lead feedings for 1 week and in half of the litters after 2 weeks of feedings. None of the lead-fed mothers developed encephalopathic signs. With oxidation of the NAD-linked substrate pair, there was a progressive decrease, relative to controls, in ADP/O ratios in both cerebellar and cerebral mitochondria from lead-fed animals. After 2 weeks these differences were significant in mitochondria from both regions (cerebellum, P less than 0.02; cerebrum, P less than 0.005). Respiratory control ratios were significantly lower in cerebellar mitochondria from lead-fed rats within 2 days of beginning feedings (P less than 0.02) and in mitochondria from both regions after 2 weeks of lead feedings (cerebellum, P less than 0.01; cerebrum, P less than 0.05). The decrease in control ratios in cerebellar mitochondria from animals receivint lead feedings for 1 week or less was due to a small decrease in state 3 respiration and a large, but inconsistent, increase in state 4 respiration. The decrease in control ratios in both cerebellar and cerebral hemisphere mitochondria after 2 weeks of lead feedings was due to a marked inhibition of state 3 respiration, relative to controls (cerebellum, P less than 0.01; cerebral hemisphers, P less than 0.05). In cerebellar mitochondria from lead-fed animals, cytochrome oxidase activity showed similar changes compared with controls: a highly significant (P less than 0.001) increase within 2 days of beginning feedings and a significant (P less than 0.01) decrease after 2 weeks of feedings.