Effect of melatonin on the behaviour of rats with continuous light-induced hypertension.

This study investigated whether continuous light exposure (CLE) results in behavioural disturbances in rats and whether melatonin can modify these potential changes. Four groups of 3-month-old Wistar rats were treated as follows for six weeks: control, melatonin, CLE, and CLE with melatonin. CLE increased systolic blood pressure and melatonin reduced it. No changes in behavioural patterns by CLE were observed. In the controls, melatonin reduced both exploration and locomotion but these parameters remained uninfluenced in the CLE. We conclude that melatonin exerted a different impact on behaviour in controls and in the CLE group.

Melatonin improves the restoration of endothelium-derived constricting factor signalling and inner diameter in the rat femoral artery after cessation of L-NAME treatment.

OBJECTIVE: Melatonin is suggested to be beneficial in several pathological conditions including arterial hypertension. One of the mechanisms proposed for its antihypertensive action is the protection against endothelial dysfunction. We investigated whether melatonin can accelerate the recovery from N(G)-nitro-L-arginine-methyl ester (L-NAME)-induced hypertension after the cessation of L-NAME administration. METHODS: Male adult Wistar rats (n=40) were randomized into 3 treated groups: 5-week L-NAME, 5-week L-NAME + 3-week vehicle, 5-week L-NAME + 3-week melatonin and into 2 age-matched control groups. The blood pressure was measured in the carotid artery. The NO-signalling was represented by NO-synthase activity and expression in the aorta and NO-mediated relaxations of femoral and mesenteric arteries. The endothelium-derived-constricting factor (EDCF)-signalling was represented by aortic cyclooxygenase-2 expression and femoral EDCF-mediated contractions. Oxidative load was determined in the aorta based on conjugated dienes concentration and inner diameter was measured in femoral arteries. RESULTS: L-NAME caused hypertension, reduced NO-signalling and arterial diameter and increased oxidative load and EDCF-signalling. While the NO-signalling was restored spontaneously 3 weeks after L-NAME cessation, the EDCF-signalling, oxidative load and arterial remodeling were completely restored only when melatonin treatment was administered during the recovery period. The blood pressure regression was comparable between spontaneous and melatonin recovery. CONCLUSION: Although melatonin did not accelerate blood pressure reduction, it attenuated EDCF-contractions and oxidative load and enlarged arterial diameter. These effects may be beneficial for cardiovascular protection.

Effect of melatonin, captopril, spironolactone and simvastatin on blood pressure and left ventricular remodelling in spontaneously hypertensive rats.

OBJECTIVE: Melatonin was shown to reduce blood pressure, oxidative load and to increase nitric oxide bioavailability predisposing melatonin to have antiremodelling potential. DESIGN: The aim of this study was to show whether melatonin can reverse left ventricular remodelling in spontaneously hypertensive rats (SHR) and to compare this potential protective effect with captopril, spironolactone, or simvastatin. METHODS: Six groups of 3-month old rats (eight per group) were treated for 5 weeks: control untreated Wistar rats, control SHR, SHR plus melatonin (10 mg/kg per 24 h), SHR plus captopril (100 mg/kg per 24 h), SHR plus spironolactone (200 mg/kg per 24 h) and SHR plus simvastatin (10 mg/kg per 24 h). Their systolic blood pressure (SBP) was measured by the tail-cuff method. The relative weights of the left ventricle, nitric oxide synthase (NOS) activity, endothelial NOS and nuclear factor kappa B (NF-kappaB) protein expression, conjugated dienes concentration, level of collagenous proteins and hydroxyproline were measured. RESULTS: SBP was reduced by all drugs investigated but most prominently by captopril in SHR. The activity of NOS and endothelial NOS expression increased in the left ventricles of SHR compared with controls. Melatonin and spironolactone further increased NOS expression. Left ventricular oxidative load, estimated by NF-kappaB expression and conjugated dienes concentration, increased in SHR. Only melatonin reduced NF-kappaB expression and decreased conjugated diens concentration. Only captopril reduced left ventricular hypertrophy in SHR, whereas melatonin reduced collagenous protein concentration and hydroxyproline content in the left ventricle. CONCLUSION: It is concluded that although melatonin, in comparison with captopril, did not reverse left ventricle hypertrophy, it reversed left ventricular fibrosis. This protection by melatonin may be caused by its prominent antioxidative effect.

Soil flushing by surfactant solution: pilot-scale demonstration of complete technology.

This paper mainly relates to the real polychlorinated biphenyl (PCB)-contaminated soil flushing process, in which an aqueous solution of anionic surfactant was passed through sandy soil having an average concentration 34.3 mg/kg of dry matter. The goal of the treatment was to decrease the PCB concentration in the soil to less than 10 mg/kg, which is a limiting value if the soil is to be used in the field of civil engineering. The laboratory part was focused on the demonstration of the suggested method for estimating the CMC value of the surfactant used for leaching the PCBs from the soil to the solution. The estimate was based on a set of batch experiments carried out with the same soil as the soil used for the pilot-scale experiments. Theoretically, all effects affecting the CMC should be considered in an estimated value. The experimental facility used for the pilot-scale demonstration consisted of a steel column (3 m in length, 1.5 m in diameter) containing 1.7 m(3) of polluted soil and a liquid circulation system, by which an aqueous solution of a surfactant was supplied to the soil. Spolapon AOS 146 (anionic surfactant) solution (40 g/L) was passing through the soil column for 2.5 months. The concentration of the surfactant and PCBs in the aqueous soil extract was monitored during this time period. The final PCB concentration profile in the soil was determined after stopping the liquid flow. After passing through the soil, the PCBs containing the aqueous extract was pumped out from the steel column bottom to a treatment unit, where it was processed by coagulation. The final PCB concentration profile in the soil was compared with the results of the theoretical model, which is also described in the paper. The time necessary to reach the limit demanded was estimated to move within the range from 6 to 12 months.

Adsorptive micellar flocculation as an efficient method for processing soil extracts containing both surfactant and polychlorinated biphenyls: practical demonstration.

The main purpose of the paper is to share the results and experience from processing soil extracts containing a high concentration of both anionic surfactant and polychlorinated biphenyls (PCBs) by use of method the called adsorptive micellar flocculation. The method is similar to coagulation, but the mechanism is more complicated. The flocculants examined in the laboratory section involved ferric chloride, aluminium chloride, ferric sulfate, and aluminum sulfate. It was observed that ferric chloride provides the best PCB removal efficiency from the extract. Subsequently, two extracts obtained from the pilot-scale demonstration of the PCBs leaching from the soils by the surfactant solution were processed by this method. The volume of the extracts processed was several hundred liters. The method proved it can remove PCBs from all extracts with a very high efficiency (greater than 99.99%). The residual PCB concentrations in solution were less than 1 microg/L.

Semi-empirical approach to modeling of soil flushing: model development, application to soil polluted by zinc and copper.

This paper describes a semi-empirical approach to modeling the soil flushing technology. A new mathematical model aimed at predicting the course of the continuous soil flushing process by use of the input data obtained from simple batch laboratory experiments is described in the theoretical part. An objective of the study is to apply this new model to soil polluted by zinc and copper (11949 mg kg(-1) and 1895 mg kg(-1), respectively) by flushing the soil with an ammonia nitrogen solution. A set of batch experiments provided both equilibrium and kinetic data characterizing the leaching ability of both metals. By use of the model, the optimal ammonia concentration in the flushing solution was estimated (0.6 mol L(-1)). For this concentration, validity of the model results was verified by a column experiment. The removal efficiency obtained was 44% (zinc) and 54% (copper). The model correctly predicted the period of time needed for the removal of weakly bound metal fractions as well as the estimate of the overall removal efficiency of metals from the soil during the flushing process. It has also proven that it is possible to use the column experiment for model calibration through the modification of the input data. Agreement of the model and experimental results can be further improved this way.