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Zinc phosphodiesterase (ZiPD) participates in the maturation of tRNA precursors. The roles of metal ions in promoting phosphoryl transfer reaction on zinc phosphodiesterase (ZiPD) activity have not been fully characterized. Therefore, this study investigated the effects of some metal ions on phosphodiesterase activity of Escherichia coli ZiPD as well as the binding site and binding affinity of the metal ions. ZiPD activity was measured by monitoring the rate of hydrolysis of bis-para-nitrophenyl phosphate (bis-pNPP) in the presence of some selected divalent metal ions (Mn2+, Co2+, Mg2+ and Zn2+). The results obtained revealed that Mn2+ at 1 mM activated ZiPD activity by 4-fold with binding affinity score of 1.795. Co2+ at 0.5 mM activated ZiPD activity by 2-fold with binding affinity score of 1.773. Mg2+ at 0.5 mM enhanced the binding affinity of ZiPD for bis-pNPP but did not increase the turnover rate of ZiPD. Zn2+ at 1.5 mM activated ZiPD activity by 2-fold via increased affinity of ZiPD for bis-pNPP. In conclusion, the findings from this study showed that Mn2+ and Zn2+ are the most effective stimulatory ions of ZiPD for bis-pNPP while Zn2+ exerted the highest binding affinity of ZiPD for bis-pNPP.

Hypertension is the most common non-communicable disease, with about 1.28 billion hypertensive people worldwide. It is more prevalent in men than women and more common in the elderly. Hereditary, age, obesity, lifestyle, diet, alcohol, and chronic metabolic diseases are the major risk factors of hypertension. Treating hypertension is a complex process as there are several mechanisms responsible for its pathogenesis; hence, a combination of several drugs is used for managing hypertension. Drugs used in managing hypertension are expensive and often come with associated side effects; thus, there is need for alternative means of managing this life-threatening disease. These drugs do not achieve the recommended blood pressure target in most people; more so majority of people with hypertension do not follow the treatment regimen religiously. Some Africans have been reported to become normotensive as a result of dietary consumption of spices. Several spices have been used over the years in Africa to manage hypertension. The aim of this review is to evaluate the ethnomedicinal use, bioactive phytochemical composition, bioactive compounds present, and pharmacological applications of spices commonly used in Africa for managing hypertension. Most of the plants used contained polyphenols, flavonoids, tannins, anthraquinone, flavonoids, cardiac glycosides, and saponins. Dietary supplementation of Xylopia aethiopica and other spices in diet have been proven to significantly reduced plasma angiotensin-I-converting enzyme (ACE) than simvastatin (the reference drug). Toxicological, histological, and hematological evaluation revealed that acute and chronic consumption of most of these spices are safe. Studies have also revealed that some of the spices can be used as alternative therapy alongside usual antihypertensive medications. PRACTICAL IMPLICATION: The prevalent rate of hypertension is on the increase in both the developed and developing countries. People often skip medication due to their busy schedule and anti-hypertensive potential side effects; however, this is not the case with food/spices as most people consumed them daily. Deliberate, right combinations and consistent incorporation of spices with proven anti-hypertensive potential into our diet may be of great benefit in normalizing blood pressure and mitigate other complications on the heart and vital organs.

Summary Monosodium glutamate (MSG), an established excitotoxic food additive, has been found to induce oxidative stress in all tissues. To examine the protective effects of ivermectin on MSG-induced excitotoxicity, 28 male albino rats were randomized into four groups. Group 1, the control, received 1 ml of oral distilled water, group 2 was administered an aqueous solution of MSG (4 mg/kg body weight/day). Group 3 was co-administered with the same dose of MSG and 0.4 mg/kg body weight of ivermectin, while group 4 rats received orally the same dose of MSG for 2 weeks, after which ivermectin was administered orally for 1 week. Administration of MSG orally for 21 days and for 14 days, followed by oral administration of ivermectin for 7 days, significantly increased (p < 0.05) glutathione-S-transferase, nitric oxide synthase, superoxide dismutase and catalase activities as well as malondialdehyde and intracellular Ca2+ concentrations while Na+ - K+ - ATPase, Ca2+ - Mg2+ - ATPase, acid phosphatase (ACP) and alkaline phosphatase (ALP) activities were significantly reduced (p < 0.05) compared to the control. However, co-administration of MSG and ivermectin for 21 days did not show any significant difference (p > 0.05) in all the parameters studied compared to the control. This result suggests that ivermectin may protect against MSG-induced excitotoxicity in rats.

Cellulases are enzymes that hydrolyse cellulose and related cellu-oligosaccharides derivatives. Its applications are enormous but high cost of production is the bottle-neck against the utilization of cellulase in industries. Therefore, this study investigated the isolation, purification and characterization of cellulase produced by Aspergillus niger cultured on Arachis hypogaea shells. The crude cellulase enzyme was produced by A. niger through submerged fermentation process using A. hypogaea shells as a carbon source. The optima fermentation conditions were determined by varying different parameters. The crude cellulase was purified through ammonium sulphate precipitation, dialysis and gel-filtration chromatography. The molecular weight was estimated using sodium dodecyl sulphate polyacrylamide gel electrophoresis. The effects of pH and temperature on the activity of the purified cellulase were investigated. The study revealed that the: optimal production of crude cellulase was achieved at incubation period of 120 h, pH 4, temperature 40 °C, and inoculum size of 13 × 105 CFU/ml. Cellulase was purified to 68.12-fold with a yield and specific activity of 3.87% and 484.3 U/mg respectively. The Vmax for the cellulase was 9.26 U/ml while the Km was 0.23 mg/ml. The molecular weight of the cellulase was approximately 13.5 kDa and the enzyme has higher specificity for CMC compared to other substrates. The optimum pH and temperature for the cellulase activity were 4 and 40 °C respectively. The present study has shown that A. hypogaea shells can be used as a carbon source by A. niger for the production of cellulase., Biotechnology; Biochemistry, Molecular biology; Proteins; Cellulase; Aspergillus niger; Arachis hypogaea; Purification; Characterization

The global challenge to the treatment of malaria is mainly the occurrence of resistance of malaria parasites to conventionally used antimalarials. Artesunate, a semisynthetic artemisinin compound, and other artemisinin derivatives are currently used in combination with selected active antimalarial drugs in order to prevent or delay the emergence of resistance to artemisinin derivatives. Several methods, such as preparation of hybrid compounds, combination therapy, chemical modification and the use of synthetic materials to enhance solubility and delivery of artesunate, have been employed over the years to improve the antimalarial activity of artesunate. Each of these methods has advantages it bestows on the efficacy of artesunate. This review discussed the various methods employed in enhancing the antimalarial activity of artesunate and delaying the emergence of resistance of parasite to it.

G-quadruplex DNAzymes are short DNA aptamers with repeating G4 quartets bound in a non-covalent complex with hemin. These G4/Hemin structures exhibit versatile peroxidase-like catalytic activity with a wide range of potential applications in biosensing and biotechnology. Current efforts are aimed at gaining a better understanding of the molecular mechanism of DNAzyme catalysis as well as devising strategies for improving their catalytic efficiency. Multimerisation of discrete units of G-quadruplexes to form multivalent DNAzyes is an emerging design strategy aimed at enhancing the peroxidase activities of DNAzymes. While this approach holds promise of generating more active multivalent G-quadruplex DNAzymes, few examples have been studied and it is not clear what factors determine the enhancement of catalytic activities of multimeric DNAzymes. In this study, we report the design and characterisation of multimers of five G-quadruplex sequences (AS1411, Bcl-2, c-MYC, PS5.M and PS2.M). Our results show that multimerisation of G-quadruplexes that form parallel structure (AS1411, Bcl-2, c-MYC) leads to significant rate enhancements characteristic of cooperative and/or synergistic interactions between the monomeric units. In contrast, multimerisation of DNA sequences that form non-parallel structures (PS5.M and PS2.M) did not exhibit similar levels of synergistic increase in activities. These results show that design of multivalent G4/Hemin structures could lead to a new set of versatile and efficient DNAzymes with enhanced capacity to catalyse peroxidase-mimic reactions.

Peroxidases are well known for their ability to biodegrade some recalcitrant organic pollutants like phenol and their derivatives resulting in a reduction in their toxicity. The present study was designed to extract, characterize, and evaluate the potential of partially purified peroxidase from discarded and decaying waste cabbage leaves in the biodegradation of phenol and some common synthetic azo dyes. This was done by first partially purifying the crude extract of waste cabbage peroxidase (WCP) using ammonium sulfate precipitation, dialysis, and gel filtration chromatography. Thereafter, the experimental determination of protein concentration, peroxidase activity, and biodegradation of phenol and azo dyes was done spectrophotometrically. The results showed a purification fold of 87.65 with a 34.92% yield. The partially purified peroxidase had its optimum activity at temperature 30 °C, pH 5.5 while showing broad substrate preference with ABTS been the substrate. The stability studies also showed that WCP was stable over a wide range of pH (4.0–7.0) and 41% of its original activity was retained at 80 °C indicating that it is a thermostable enzyme. The kinetic data of WCP showed Km values of 1.24, 17.89, and 19.24 mM and Vmax values of 1111.11, 909.09, and 588.24 mM /minutes for ABTS, guaiacol, and o-dianisidine respectively. Three metal ions, Hg2+, Cu2+, Ni2+, organic solvent (acetone), EDTA, and urea inhibited peroxidase activity; whereas Mn2+ and Zn2+ showed slight activation. The partially purified WCP exhibited high efficiency for the biodegradation of synthetic azo dyes and phenol at the lab-scale. After 48 h incubation, the waste cabbage peroxidase efficiently catalyzed the decolorization of tested azo dyes at varying degrees; azo blue 5, azo purple, azo yellow 6, and citrus red 2, with a percentage decolorization of 85.1, 69.1, 46.2 and 42.9%, respectively. The waste cabbage peroxidase also shows up to 91.1% efficiency for degradation of phenol in aqueous solution after 60 min. Findings from this study provide promising evidence on the possibility of utilizing/recycling a readily abundant waste cabbage to useful bioproducts like peroxidase enzyme with the ability to biodegrade azo dyes and phenol at a small scale in the laboratory. Moreover, the findings from this study increase the prospect of waste cabbage peroxidase for the treatment of industrial effluents containing dyes and phenolic pollutants. The approach of transforming waste from one source into a useful biocatalyst that can potentially be exploited to treat waste pollutants from a different source offers a chain of green technology.

Background: Most of the Nigerian studies on the determinants of diabetes self-management have focused on patient-related factors. There is no previous local study that examined the quality of diabetes self- management education provided by primary care physicians to people with diabetes mellitus.Methods: A descriptive cross-sectional study was conducted among 105 primary care physicians during a workshop. The quality of diabetes self-management education provided by the physicians was assessed using a self-designed scale of 39 Likert questions derived from American Association of Diabetes Educators seven domains of diabetes self-management. Cronbach’s reliability coefficient of each domain/subscale was ≥ 0.7. The data was analysed using the independent sample t-test and one-way ANOVA.Results: Over half of the physicians provided ‘inadequate quality’ diabetes self-management education in all the domains. Physicians had the highest mean score in the ‘taking medication’ domain (4.35 ± 0.59). The mean scores in the ‘problemsolving domain’ (3.63 ± 0.74) and the ‘being active domain’ (3.57 ± 0.71) were low. The quality of diabetes self-managementeducation provided by the physicians was not associated with any of the physician characteristics.Conclusion: The quality of physicians’ communication of diabetes self-management was suboptimal in this study. The majority of the adequately communicated diabetes self-management behaviours were risk factors reduction related and disease-centred. Thus, training of primary care physicians on diabetes self-management education is recommended because of the key role these physicians play in diabetes management in resource-poor countries.Keywords: diabetes self-management, patient–physician communication, primary care physicians, resource-poor countries, Nigeria

Anacardium occidentale L. leaf is useful in the treatment of inflammation and asthma, but the bioactive constituents responsible for these activities have not been characterized. Therefore, this study was aimed at identifying the bioactive constituent(s) of A. occidentale ethanolic leaf extract (AOEL) and its solvent-soluble portions, and evaluating their effects on histamine-induced paw edema and bronchoconstriction.The bronchodilatory effect was determined by measuring the percentage protection provided by plant extracts in the histamine-induced bronchoconstriction model in guinea pigs. The anti-inflammatory effect of the extracts on histamine-induced paw edema in rats was determined by measuring the increase in paw diameter, after which the percent edema inhibition was calculated. The extracts were analyzed using gas chromatography-mass spectrometry to identify the bioactive constituents. Column chromatography and Fourier transform infrared spectroscopy were used respectively to isolate and characterize the constituents. The bronchodilatory and anti-inflammatory activities of the isolated bioactive constituent were evaluated.Histamine induced bronchoconstriction in the guinea pigs and edema in the rat paw. AOEL, hexane-soluble portion of AOEL, ethyl acetate-soluble portion of AOEL, and chloroform-soluble portion of AOEL significantly increased bronchodilatory and anti-inflammatory activities (P 0.05). Oleamide (9-octadecenamide) was identified as the most abundant compound in the extracts and was isolated. Oleamide significantly increased bronchodilatory and anti-inflammatory activities by 32.97% and 98.41%, respectively (P 0.05).These results indicate that oleamide is one of the bioactive constituents responsible for the bronchodilatory and anti-inflammatory activity of A. occidentale leaf, and can therefore be employed in the management of bronchoconstriction and inflammation.

The roles of Mg(2+) and Zn(2+) ions in promoting phosphoryl transfer catalysed by alkaline phosphatase are yet to be fully characterised. We investigated the divalent metal ion requirements for the monoesterase and diesterase activities of calf intestinal alkaline phosphatase. The synergistic effect of Mg(2+) and Zn(2+) in promoting the hydrolysis of para-nitrophenyl phosphate (monoesterase reaction) by alkaline phosphatase is not observed in the hydrolysis of the diesterase substrate, bis-para-nitrophenyl phosphate. Indeed, the diesterase reaction is inhibited by concentrations of Mg(2+) that were optimal for the monoesterase reaction. This study reveals that the substrate specificities of alkaline phosphatases and related bimetalloenzymes are subject to regulation by changes in the nature and availability of cofactors, and the different cofactor requirements of the monoesterase and diesterase reactions of mammalian alkaline phosphatases could have significance for the biological functions of the enzymes.

Objective: The aqueous extract of Celosia argentea var. cristata L. leaves at 100, 200, and 400 mg/kg body weight (b.w.) was investigated against cadmium (Cd)-induced oxidative stress in Wistar rats. The in vitro antioxidant of the extract was evaluated using ammonium thiocyanate, reducing power, and membrane stabilizing models. Materials and Methods: For the in vivo study, 30 male rats (Rattus norvegicus) weighing 138.02 ± 7.02 g were completely randomized into 6 groups (A–F) of 5 animals each. Animals in groups A and B received 0.5 ml of distilled water and the same volume containing 8 mg/kg b.w. of Cd, respectively, for 7 days orally. Animals in groups C, D, E, and F were treated like those in group B except that they received 100 mg/kg b.w. of ascorbic acid, and 100, 200, and 400 mg/kg b.w. of the extract, respectively, in addition to Cd. Results: Phytochemical screening revealed the presence of alkaloids (0.61%), saponins (2.93%), cardiac glycosides (0.21%), cardenolides (0.20%), phenolics (3.26%), and flavonoids (2.38%). A total of 10 mg/ml of the extract inhibited linoleic acid oxidation by 67.57%. The highest reducing power was 100 mg/ml as against 10 mg/ml for ascorbic acid. In addition, 2 mg/ml of the extract produced a membrane stabilizing activity of 63.49% as against 77.46% for indomethacin. Compared with the distilled water control group, the administration of Cd alone significantly (P < 0.05) decreased the alkaline phosphatase activity of the rat liver and brain. This decrease was accompanied by a corresponding increase in the serum enzyme. The simultaneous administration of the extract and Cd produced an enzyme activity that compared favorably (P > 0.05) with the animals that received Cd and ascorbic acid. In addition, the reduction in the superoxide dismutase and catalase activity of the liver and brain of the animals, serum uric acid, albumin and bilirubin, and also the increase in the serum malondialdehyde content in animals treated with Cd alone was attenuated by the extract; the values compared well (P > 0.05) with those simultaneously administered with Cd and ascorbic acid. Conclusion: Overall, the results indicated that the aqueous extract of C. argentea leaves attenuated Cd-induced oxidative stress in the animals, with the best result at 400 mg/kg b.w. The antioxidant activity of the extract may be attributed to the phenolic and flavonoid components of the extract. The induction of antioxidant enzymes and scavenging of free radicals may account for the mechanism of action of the extract as an antioxidant.

The effects of co-administration of artesunate and amodiaquine on some cardiovascular disease indices were investigated in albino rats (Rattus novergicus). The experimental animals were randomly divided into four groups: those administered distilled water (control), those administered artesunate (2 mg/kg body weight), those administered amodiaquine (6.12 mg/kg body weight) and those co-administered artesunate (2 mg/kg body weight) and amodiaquine (6.12 mg/kg body weight). The drugs were orally administered twice daily for three days after which the serum lipid profile, heart MDA content and heart ALP and ACP activities were determined. Artesunate significantly reduced (P0.05) total cholesterol and HDL-cholesterol concentrations in the serum with no significant effects (P0.05) on other parameters compared to controls. Amodiaquine, on the other hand, significantly reduced (P0.05) serum total cholesterol concentration while it significantly increased (P0.05) serum LDL-cholesterol and heart ACP activity compared to controls. Co-administration of artesunate and amodiaquine significantly reduced (P0.05) total cholesterol and HDL-cholesterol concentrations in the serum while significantly increasing (P0.05) serum LDL-cholesterol concentration, atherogenic index (LDL-C/HDL-C) and ACP activity in the heart compared to controls. The results obtained suggest that co-administration of artesunate and amodiaquine to patients with coronary heart disease should be with caution.

The effects of two hydrazine derivatives (isoniazid and hydralazine) on the inactivation of myeloperoxidase by H2O2 were investigated. Incubation of 20 nM myeloperoxidase with 0.25 mM H2O2 alone caused a time-dependent irreversible loss of tetramethylbenzidine oxidation activity with a pseudo-first order inactivation rate constant of 0.057 min -1 . The hydrazine derivatives increased the inactivation rate in a concentration-dependent manner. Inactivation of the enzyme by H2O2 with or without the hydrazides showed a saturation kinetics pattern. Steady state kinetics analysis suggests that the hydrazides likely inactivate myeloperoxidase using a similar inactivating species as does H2O2. A bimolecular rate constant, specific inactivation rate enhancement factor (k*enh) is proposed as a formal description of the inactivation rate stimulation by the hydrazides. This parameter potentially avoids confounding the finite inactivation due to H2O2 with that caused by the presence of the hydrazides. The relevance of these findings and the constants derived to the analysis of suicide inactivation of peroxidases by reductant substrates are discussed.

The effect of promethazine on peroxidase-catalyzed oxidation of 3,3', 5,5'-tetramethylbenzidine was investigated at pH 5.4. Promethazine dose dependently introduced a lag in the appearance of tetramethylbenzidine charge-transfer complex monitored at 652 nm. Increasing concentrations of tetramethylbenzidine however decreased the lag period proportional to the tetramethylbenzidine concentration. Addition of promethazine to preformed charge transfer complex caused rapid bleaching of the blue-colored complex. Titration of promethazine with the yellow-colored diimine gave rise to the blue charge-transfer complex and the complete reduction of the species to the colorless parent amine compound. The available evidence suggests that promethazine is oxidized via redox mediation by tetramethylbenzidine peroxidase-oxidized products.

The study was carried out to investigate whether an interaction between albendazole and ivermectin could lead to enhanced central nervous system (CNS) toxicity. Ivermectin (0.4mg/kg body weight (b.w)) and/or albendazole (15mg/kg b.w) were daily and orally administered to albino rats for 14 days. Activities of acid phosphatase (ACP), alkaline phosphatase (ALP), catalase (CAT), Na+-K+ ATPase, Ca2+-Mg2+ ATPase and malondialdehyde (MDA) level which are considered essential to correct functioning of the brain were determined. The co-administration of the two drugs significantly caused reduction (p0.05) in the activity of these enzymes. These suggest that in the presence of albendazole, ivermectin is able to reach the CNS and impair its function through neurochemical changes. Also, co-administration of ivermectin and albendazole led to a significant increase (p

The aim of this study was to investigate the effect of crankcase oil on the cellular and functional integrity of rat skin. Thirty (30) rats were randomly grouped into six viz groups A-F. Group A (base-line control) received 2 ml of distilled water. 2.5 %, 5.0 %, 7.5 %, and 10.0 % v/v of the crankcase oil were prepared using unused oil as solvent and 2 ml of the concentrations were topically administered to groups C-F respectively for seven consecutive days. Group B served as positive control and received 2 ml of the unused oil. The rats were sacrificed 24 hours after the last administration, and blood and part of the skin were collected. Alkaline phosphatase (ALP), acid phosphatase (ACP), superoxide dismutase (SOD) and malondialdehyde level in the blood and skin samples collected were evaluated. Elemental analysis of the crankcase oil was also carried out. The result revealed high lead, iron and chromium levels. Blood lead concentration of rats was significantly (P

The effect of hydroxyurea, sodium thiocyanate and potassium tellurite on cations content and membrane properties of sickle erythrocyte was investigated in this study. Human sickle blood was incubated with the drugs in vitro at their optimum sickling inhibitory concentration. Mean corpuscular volume (MCV), mean corpuscular haemoglobin concentration (MCHC), cations (Na+, K+ and Ca2+) contents and viscosity were measured. Tellurite and thiocyanate significantly increased (P0.05) MCV, reduced MCHC and blood viscosity and also significantly inhibited (P0.05) calcium accumulation by sickle red blood cell. In addition, the two drugs increased red blood cell sodium gain and inhibited potassium loss significantly. Incubation of the drugs with sickle erythrocyte ghost membrane indicated that tellurite and thiocyanate significantly inhibited (P0.05) Na+-K+-ATPase (EC 3.6.3.9) and Ca2+-Mg2+-ATPase (EC 3.6.3.8) activities. Blood incubated with hydroxyurea also significantly inhibited (P0.05) calcium ion accumulation but had no effect on all other measured parameters. This result suggests that thiocyanate and tellurite have positive modification effect on sickle erythrocyte membrane and cation transport thereby causing rehydration and improvement in red blood cell deformability. Keywords: Cations content, Erythrocyte Membrane, Hydroxyurea, Sodium thiocyanate, Potassium tellurite Egyptian Journal of Biochemistry and Molecular Biology Vol. 26 (1) 2008 pp. 117-125

Investigations were carried out to find the biochemical and bioenergetic implications of a defective in vivo synthesis of mitochondrial proteins during dietary-protein depletion. 3.4% dietary protein was fed to 21-day-old weanling rats for 30 days (experimental), while 21.0% dietary protein was fed to controls. A close simulation of marasmic-kwashiorkor syndrome was obtained in the experimental group. Rat liver mitochondria were isolated, and the functional and structural integrity was determined using biochemical standard parameters. Results show that the respiratory control ratio (RCR) is reduced by 50% in the experimental group, using any of the pyruvate/malate, beta-hydroxybutyrate or succinate as substrate. The effects of storage at 0 degree C were more pronounced in mitochondria from protein-depleted rats as these mitochondria are more leaky to protons (H+); hence they are defective in carrying out chemiosmotic oxidative phosphorylation. There is a drastic reduction in the basal ATPase and cytochrome oxidase activities with low ATP production and a decline in energy expenditure. This led to serious bioenergetic consequences culminating in heavy dependence on glycolysis and other biochemical aberrations.

Oxygraphic measurements of the rates of mitochondrial respiration in the presence of varying amounts of chalepin, imperatorin and marmesin, three naturally occurring furanocoumarins, revealed that the oxidation of NAD(+)-linked substrates was inhibited by chalepin and imperatorin and less significantly by marmesin. The order of potency being rotenone much greater than chalepin imperatorin greater than marmesin. There was no effect whatsoever on succinate oxidation by the furanocoumarins tested (up to 60 microM). State 3 respiration was also inhibited by these furanocoumarins; by at least 80% by 10 microM chalepin and by 48 and 29% with 60 microM imperatorin and 60 microM marmesin, respectively. Consequently, ADP control of respiration was diminished by those concentrations of furanocoumarins that inhibited respiration. At 60 microM, respiratory control ratio was reduced by about 88, 49 and 28% with chalepin, imperatorin and marmesin, respectively. A measurement of the rate of proton and Ca2(+)-movements across the mitochondrial coupling membrane demonstrated that succinate-supported transport was not affected by these furanocoumarins. On the other hand, pyruvate/malate-supported proton ejection was significantly inhibited by chalepin, imperatorin and marmesin. The order of the degree of inhibition of proton flux is rotenone much greater than chalepin greater than imperatorin greater than marmesin. The pattern of the inhibition of pyruvate/malate-supported Ca2(+)-transport was identical to that seen during proton transport. A comparison of the effects of chalepin to that of rotenone suggests that chalepin might be about 10 times less potent than rotenone.

The acidity and lipophilicity of the fluorinated arylalkylsulphonamides are determined by the nature of the substituents on their aromatic rings. Herbicidal and anti-inflammatory effects of these compounds appear to increase with their lipophilicity. According to Mitchell's chemiosmotic theory, lipophilic weak-acid uncoupling agents act by transporting protons across the inner mitochondrial membrane and thus destroying the proton-electrochemical potential gradient required for ATP synthesis and ion transport. 1:1:1-Trifluoro-N-[2-methyl-4-(phenylsulphonyl) phenyl]methanesulphonamide (Perfluidone), a pre- and post-emergence herbicide (at 20 microM concentration), in isolated rat-liver mitochondria caused (1) a 2-fold stimulation of metabolic state-4 respiration, (2) a reduction of respiratory control ratio (RCR) by at least 50%, (3) an enhancement of latent ATPase activity by 40%, (4) a significant passive swelling of mitochondria in 0.15 N NH4Cl(delta A520 = -0.46 +/- 0.003), (5) proton intrusion during state-4 respiration (356 ng H+/min/mg protein; ng H+/min/mg protein with 5 microM perfluidone), and (6) at least 100% stimulation of oligomycin-inhibited respiration. These profiles are qualitatively comparable with those of the classical lipophilic weak-acid uncoupler, carbonylcyanide-trifluoro-methoxyphenylene hydrazone (FCCP), which acts by promoting the electrogenic transport of H+ ions across mitochondrial membrane.

Oxygen electrode polarographic measurements of the rate of oxygen consumption by isolated rat liver mitochondria revealed that oligomycin inhibition of respiration was offset to different degrees by varying concentrations of perfluidone (1,1,1-trifluoro-N-(2 methyl-4-(phenylsulfonyl) methanesulfonamide). Using any of pyruvate-malate, succinate or ascorbate-TMPD (N,N,N',N'-tetramethyl-p-phenylenediamine) as substrate, this herbicidal and anti-inflammatory agent at 100 microM concentration caused a 5-fold stimulation of oligomycin-inhibited respiration. Higher concentrations of the herbicide (greater than or equal to 120 microM) gave lower stimulatory effects. Similar stimulatory effects were obtained with 1 microM FCCP (carbonylcyanide p-trifluoromethyoxyphenyl-hydrazone), a classical protonophore. Our results also show an enhanced oligomycin-sensitive ATPase action in intact mitochondria incubated with ATP and varying concentrations of perfluidone. Maximum enhancement effect (111.3%) was obtained at 120 microM perfluidone. FCCP (1 microM) stimulated this ATPase action by 130%. An initial inhibition of respiration by oligomycin is due to an interaction with the proton well of FOF1-ATP synthetase (Lardy, H.A. et al., Arch. Biochem. Biophys., 78 (1953) 587). Perfluidone probably increases the proton conductance of mitochondrial inner membrane in the same manner as FCCP and thus causes an increase in mitochondrial respiratory rate. As protons move into the matrix, delta mu H+, the proton electrochemical potential gradient becomes very small and the F0F1-ATP synthetase functions in the direction of hydrolysis of ATP rather than its shnthesis (Mitchell, P., Eur. J. Biochem., 95 (1979) 1). These findings therefore indicate that perfluidone acts in a way similar to FCCP, a classical uncoupler and protonophore.

Apart from the symptoms of poisoning which the fluorinated arylalkylsulphonamides share with the classical protonphore and uncoupler of oxidative phosphorylation, carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), the direct correlation between the lipophilic weak acid properties of these chemicals and their biological activity suggests that permeation of the inner mitochondrial membrane could be the initial step in the molecular mechanism of their biological activity. Mitochondria isolated from the livers of rats intraperitoneally exposed to varying doses (0-80 mg/kg body wt.) of perfluidone (1,1,1-trifluoro-N-(2 methyl-4-(phenylsulphonyl)phenyl methanesulphonamide), a fluorinated arylalkylsulphonamide pesticide, exhibit the following dose-dependent features: (i) increased state-4 respiration: stimulation being maximal (greater than or equal to 400%) at 80 mg perfluidone per kg body wt.), (ii) release of respiratory control by ADP: least respiratory control ratios (RCRs) (less than or equal to 1.2) were obtained at 80 mg perfluidone per kg body wt., (iii) reduced ADP/O ratios, (iv) increased mitochondrial passive swelling, (vi) reduced rates of mitochondrial proton ejection during succinate oxidation, (vi) reduced rates of respiration-dependent Ca2+ accumulation and (vii) an enhanced oligomycin-sensitive ATPase action. These features which are qualitatively identical to those of the classical protonophore FCCP, suggest that permeation of the inner mitochondrial membrane by perfluidone is accompanied by a movement of protons into the matrix such that the proton motive force required for ATP synthesis and ion transport becomes small or not formed at all.

The acidity and lipophilicity of the fluorinated arylalkylsulphonamides are determined by the nature of the substituents on their aromatic rings. Herbicidal and anti-inflammatory effects of these compounds appear to increase with their lipophilicity. According to Mitchell's chemiosmotic theory, lipophilic weak-acid uncoupling agents act by transporting protons across the inner mitochondrial membrane and thus destroying the proton-electrochemical potential gradient required for ATP synthesis and ion transport. 1:1:1-Trifluoro-N-[2-methyl-4-(phenylsulphonyl) phenyl]methanesulphonamide (Perfluidone), a pre- and post-emergence herbicide (at 20 microM concentration), in isolated rat-liver mitochondria caused (1) a 2-fold stimulation of metabolic state-4 respiration, (2) a reduction of respiratory control ratio (RCR) by at least 50%, (3) an enhancement of latent ATPase activity by 40%, (4) a significant passive swelling of mitochondria in 0.15 N NH4Cl(delta A520 = -0.46 +/- 0.003), (5) proton intrusion during state-4 respiration (356 ng H+/min/mg protein; ng H+/min/mg protein with 5 microM perfluidone), and (6) at least 100% stimulation of oligomycin-inhibited respiration. These profiles are qualitatively comparable with those of the classical lipophilic weak-acid uncoupler, carbonylcyanide-trifluoro-methoxyphenylene hydrazone (FCCP), which acts by promoting the electrogenic transport of H+ ions across mitochondrial membrane.