Stimulation of dopamine oxidation in liver mitochondria by palmitic acid in the presence of ATP and <Emphasis Type="Italic">tert</Emphasis>-butylhydroperoxide

The effect of palmitic acid on the oxidation of dopamine, i.e., on the monoamine oxidase (MA-oxidase) activity, was investigated on deenergized liver mitochondria, upon energization by ATP and also in the presence of an oxidizing agent tert-butylhydroperoxide (TBH). It was found that palmitic acid reduces the value of the apparent K _m for dopamine without alteration of the apparent V _max. This points to stimulation of the mitochondrial MA-oxidase activity by palmitic acid at low concentrations of dopamine. Stimulatory effect of palmitic acid may be related to the ability of amphiphilic compounds to increase the negative charge density on the outer mitochondrial membrane. This leads to an increase in the local concentration of positively charged ions of dopamine in the layer adjacent to the membrane near the active site of monoamine oxidase. ATP eliminates the ability of palmitic acid to stimulate the MA-oxidase activity of mitochondria. This effect of ATP is not observed in the presence of the F _O F ₁-ATP-synthase inhibitor oligomycin. Apparently, in the case of vector transport of H⁺ from the matrix induced by ATP-hydrolysis, protonation of palmitic acid anions occurs on the outer mitochondrial membrane, followed by the movement of the neutral molecules to the outer and then to the inner monolayer of the inner membrane. It was found that TBH at a concentration of 300 μM has no significant effect on the ATPase activity of mitochondria and in the presence of ATP and palmitic acid reduces the value of the apparent K _m for dopamine without alteration of the apparent V _max. Antioxidant thiourea eliminates this effect of TBH. We propose that the TBH-induced oxidative stress in the case of ATP-energized mitochondria results in the movement of palmitic acid molecules from the inner to the outer membrane. This leads to an increase in the density of negative charges on the surface of this membrane and, therefore, to the stimulation of the dopamine oxidation.     

Effect of bedaquiline on the functions of rat liver mitochondria

The paper considers the effects of bedaquiline (BDQ), an antituberculous preparation of the new generation, on rat liver mitochondria. It was shown that 50?μM BDQ inhibited mitochondrial respiration measured with substrates of complexes I and II (glutamate/malate and succinate/rotenone systems respectively) in the states V₃ and V_DNP. At the same time, at concentrations below 50?μM, BDQ slightly stimulated respiration with substrates of complex I in the state V₂. BDQ was also found to suppress, in a dose-dependent manner, the activity of complex II and the total activity of complexes II?+?III of the mitochondrial transport chain. It was discovered that at concentrations up to 10?μM, BDQ inhibited H₂O₂ production in mitochondria. BDQ (10–50?μM) suppressed the opening of Ca²⁺-dependent CsA-sensitive mitochondrial permeability transition pore. The latter was revealed experimentally as the inhibition of Ca²⁺/P_i-dependent swelling of mitochondria, suppression of cytochrome c release, and an increase in the Ca²⁺ capacity of the organelles. BDQ also decreased the rate of mitochondrial energy-dependent K⁺ transport, which was evaluated by the energy-dependent swelling of mitochondria in a K⁺ buffer and DNP-induced K⁺ efflux from the organelles. The possible mechanisms of BDQ effect of rat liver mitochondria are discussed.     

Variability in host plant resistance of Sorghum to Striga Hermonthica infestation in West Africa

Fourteen elite sorghum lines were evaluated for their resistance to Striga hermonthica at three locations in Nigeria and Mali. Results showed that many of the lines especially MALISOR 84-1, SAMSORG 41, 97-SB-F5DT-64 (Keninkédié) and the check SRN 39 remained resistant to Striga in all locations with low emerged Striga counts, while SAMSORG 14 had the highest Striga infestation in all locations. Considerable variation in reaction to Striga infestation was observed on Séguètana, 97-SB-F5DT-63 (Wasa), 97-SB-F5DT-65, CMDT 38, CMDT 39 and CMDT 45 which were susceptible to Striga at Samaru, Nigeria but were resistant to Striga at both locations in Mali. Based on low Striga resistance and high grain yield, lines MALISOR 84-1, SAMSORG 41, 97-SB-F5DT-64, 97-SB-F5DT-65, CMDT 39 and SAMSORT 14 have been nominated for wider evaluation across more West African countries.     

Long-term effects of graduated compression stockings on cardiorespiratory performance

The use of graduated compression stockings (GCS) in sport has been increasing in the last years due to their potential positive effects for athletes. However, there is little evidence to support whether these types of garments actually improve cardiorespiratory performance. The aim of this study was to examine the cardiorespiratory responses of GCS during running after three weeks of regular use. Twenty recreational runners performed three tests on different days: test 1) – a 5-min maximal effort run in order to determine the participants’ maximal aerobic speed; and tests 2) and 3) – a fatigue running test of 30 minutes at 80% of their maximal aerobic speed with either GCS or PLACEBO stockings at random. Cardiorespiratory parameters (minute ventilation, heart rate, relative oxygen consumption, relative carbon dioxide production, ventilatory equivalents for oxygen and carbon dioxide, and oxygen pulse) were measured. Before each test in the laboratory, the participants trained with the randomly assigned stockings (GCS or PLACEBO) for three weeks. No significant differences between GCS and PLACEBO were found in any of the cardiorespiratory parameters. In conclusion, the present study provides evidence that running with GCS for three weeks does not influence cardiorespiratory parameters in recreational runners.     

Two common nonsynonymous paraoxonase 1 (<Emphasis Type="Italic">PON1</Emphasis>) gene polymorphisms and brain astrocytoma and meningioma

Background  

Human serum paraoxonase 1 (PON1) plays a major role in the metabolism of several organophosphorus compounds. The enzyme is encoded by the polymorphic gene PON1, located on chromosome 7q21.3. Aiming to identify genetic variations related to the risk of developing brain tumors, we investigated the putative association between common nonsynonymous PON1 polymorphisms and the risk of developing astrocytoma and meningioma.     

Local changes in the rabbit brain cortex redox potential accompanying the formation of a conditioned defensive reflex

The brain E is determined by ratio in rate of processes occuring in two energy compartments--in glycolysis (the more ancient one in evolution) in which glucose is splitted whithout oxygen utilization, and in oxidative metabolism which is younger in evolution than glycolysis and more effective than glycolysis. In the present investigation, the brain cortex E changes were recorded with implanted platinum electrodes. CDR was established by combination of light and electric shock applied to the left ear. It has been found that the combinations started to be accompanied by the E shift after the first 5-20 combinations. The E shifts were widely generalized over the cortex, and both increasing and decreasing E were well expressed within 50-200 combinations. As the number of combination increased, the increases in E were gradually replaced by the decreases in E. This dynamic in the balance of the major sources of the brain energy supply during the formation of CDR demonstrates, in our opinion, that subcellular structures or complexes of cells which appeared at the same stages of evolution as the compartment of oxidative metabolism make a significant contribution to the CDR acquisition when memory traces are created, while brain function during realization of well consolidated CDR are supported mainly by glycolysis.