Lipid peroxide metabolism in chemical carcinogenesis]

Lecithin and kephalin content in the microsomes and mitochondria of the rat liver, and also the activity of enzymatic and nonenzymatic systems of the phospholipid peroxidation showed a sharp change following 3,4-benzpyrene injection. Carcinogenesis is accompanied by significant changes in the lipid peroxides content and in the activity of the enzyme utilizing lipoperoxides (glutathion peroxidase, glutathion reductase). Accumulation of lipid peroxides in the rat liver in carcinogenesis was connected with disturbed balance of the generating systems and detoxication of lipid peroxides in the tumour is attributed to the high activity of the protective enzymatic systems and serves as a reflection of the adaptation mechanisms directed to the maintenance of a high pool of proliferating cells in the tumour.     

Effects of general,specific and combined warm-up on explosive muscular performance

The purpose of this study was to compare the acute effects of general, specific and combined warm-up (WU) on explosive performance. Healthy male (n = 10) subjects participated in six WU protocols in a crossover randomized study design. Protocols were: passive rest (PR; 15 min of passive rest), running (Run; 5 min of running at 70% of maximum heart rate), stretching (STR; 5 min of static stretching exercise), jumping [Jump; 5 min of jumping exercises – 3x8 countermovement jumps (CMJ) and 3x8 drop jumps from 60 cm (DJ60)], and combined (COM; protocols Run+STR+Jump combined). Immediately before and after each WU, subjects were assessed for explosive concentric-only (i.e. squat jump – SJ), slow stretch-shortening cycle (i.e. CMJ), fast stretch-shortening cycle (i.e. DJ60) and contact time (CT) muscle performance. PR significantly reduced SJ performance (p =0.007). Run increased SJ (p =0.0001) and CMJ (p =0.002). STR increased CMJ (p =0.048). Specific WU (i.e. Jump) increased SJ (p =0.001), CMJ (p =0.028) and DJ60 (p =0.006) performance. COM increased CMJ performance (p =0.006). Jump was superior in SJ performance vs. PR (p =0.001). Jump reduced (p =0.03) CT in DJ60. In conclusion, general, specific and combined WU increase slow stretch-shortening cycle (SSC) muscle performance, but only specific WU increases fast SSC muscle performance. Therefore, to increase fast SSC performance, specific fast SSC muscle actions must be included during the WU.     

Similar hypotensive responses to resistance exercise with and without blood flow restriction

Low intensity resistance exercise (RE) with blood flow restriction (BFR) has gained attention in the literature due to the beneficial effects on functional and morphological variables, similar to those observed during traditional RE without BFR, while the effects of BFR on post-exercise hypotension remain unclear. The aim of the present study was to compare the blood pressure (BP) response of trained normotensive individuals to RE with and without BFR. In this cross-over randomized trial, eight male subjects (23.8 ± 4 years, 74 ± 3 kg, 174 ± 4 cm) completed two exercise protocols: traditional RE (3 x 10 repetitions at 70% one-repetition maximum [1-RM]) and low intensity RE (3 x 15 repetitions at 20% 1-RM) with BFR. Blood pressure measurements were performed after 15 min of seated rest (0), immediately after and 10 min, 20 min, 30 min, 40 min, 50 min and 60 min after the experimental sessions. Similar hypotensive effects for systolic BP (SBP) were observed for both protocols (P < 0.05) after exercise, with no differences between groups (P > 0.05) and no statistically significant difference for diastolic BP (P > 0.05). These results suggest that in normotensive trained individuals, both traditional RE and RE with BFR induce hypotension for SBP, which is important to prevent cardiovascular disturbances.     

Influence of dicarbonyls on kinetic characteristics of glutathione peroxidase

Se-containing glutathione peroxidase (GSH-Px) is one of the key enzymes of the body’s antioxidant system. The kinetic characteristics of GSH-Px (substrate is tert-butyl hydroperoxide) after modification of the enzyme by various concentrations of natural dicarbonyls (glyoxal, methylglyoxal, malonic dialdehyde) were studied. It was shown that dicarbonyls affected both K _m and V _max for GSH-Px. It is suggested that the effect of various dicarbonyls on GSH-Px depends on the molecular mechanisms of their interaction with the amino acid residues of the enzyme.     

Fluctuation approach to description of nonideal plasma. I: Equilibrium plasma

A model capable of describing the kinetics of collisional recombination in nonideal plasmas by the methods of molecular dynamics is developed. The dependence of the collisional recombination rate on the coupling parameter is found to differ substantially from the extrapolation of the three-body recombination rate in nonideal plasmas. A sharp decrease in the recombination rate in strongly nonideal plasmas is revealed. As the coupling parameter decreases, collisional recombination transforms into three-body recombination.     

Changes in peroxidation under conditions of 3,4-benzypyrene-induced carcinogenesis

The activities of enzymatic systems generating and destroying peroxides and the lipid peroxide content in neoplastic rat liver and 3,4-benzpyrene-induced sarcoma were studied. The tumour was characterized by high activity of glutathione peroxidase and low activity of catalase. No urate- and glycolate oxidases or ascorbat dependent peroxidation of lipids and lipid peroxides were found in the tumour. In the liver of neoplastic animals the activities of glutathione peroxidase and NADPH-dependent system of microsomal phospholipid peroxidation and the lipd peroxides content were increased, whereas the activities of catalase and urate oxidase were decreased.     

Hydroperoxide-Reducing Enzymes in the Regulation of Free-Radical Processes

Biochemistry (Moscow) - The review presents current concepts of the molecular mechanisms of oxidative stress development and describes main stages of the free-radical reactions in oxidative stress....     

Lipoxin B, an enhancing factor of spontaneous platelet aggregation in whole blood

The arachidonic acid metabolites, lipoxin B (5,14,15-trihydroxy-6,8,10,12-eicosatetraenoate) and 5,15-dihydroxy-eicosatetraenoate were shown to possess a marked effect on platelet aggregation and procoagulant activity. Lipoxin B increases and 5,15-dihydroxy-eicosatetraenoate decreases spontaneous platelet aggregation and procoagulant activity when added at various concentrations. The drugs tested were found to have no direct action on blood coagulation.