The effects of ionizing radiation on pineal melatonin and on key enzymes of its metabolism have been studied in our laboratory. After adaptation to an artificial light/dark cycle of 12:12 h, male Wistar rats were fractionally whole-body irradiated with a dose of 2.4 Gy of gamma-rays twice a week up to total doses of 4.8, 9.6 or 14.4 Gy. Irradiation and sham-irradiation were performed in the late afternoon. The rats were sacrificed at 24:00 to 01:00 h in darkness, 6 h, 3 or 5 days after the last exposure. Pineal and serum melatonin concentrations, pineal activities of serotonin N-acetyltransferase (NAT) and of monoamine oxidase (MAO) were determined. The NAT activities in the rats irradiated with 4.8 and 9.6 Gy decreased at some intervals without changes of melatonin concentration. Irradiation with a total dose of 14.4 Gy decreased NAT activity and the concentration of pineal and serum melatonin 6 h and 3 days after the last exposure. The activity of MAO, estimated only in the rats irradiated with the dose of 14.4 Gy, increased significantly 3 days after irradiation. The fractionated irradiation up to the dose of 14.4 Gy caused a transient decrease in pineal melatonin synthesis. This could be the consequence of preferential oxidative deamination of serotonin in comparison with its N-acetylation, leading to melatonin biosynthesis.
The aim of the present study was to investigate the effects of Angiotensin II (Ang II) and Arginin-Vasopressin (AVP) on contractility of non-pregnant uterus in diabetic Wistar rats and to explore whether one-week administration of Melatonin (MLT) or Ghrelin (GHR) will change the response of diabetic uterine muscle to AngII and AVP. Uterine horns, prepared by the method of isolated tissues were investigated as w ell as glycemic profile, blood pressure and body weight. The research of smooth muscle contractions was made by a new method of analysis, characterizing in detail the various phases of the myometrial activity. Differences in the development of the peptide-mediated smooth muscle contractions depending on the phase of the estrous cycle were observed. Experimental diabetes had a pronounced negative effect on force and time-parameters of AngII and AVP-stimulated uterine contractions. Administration of GHR or MLT had a beneficial effect on the glycemic status of diabetic rats and partially improved the response of uterine preparations to the peptides. The application of MLT increased both force and time-parameters of Ang II- and AVP-stimulated uterine contractions while treatment with GHR increased power characteristics and shortened contraction and relaxation of the smooth muscle process., T. Georgiev, A. Tolekova, R. Kalfin, P. Hadzhibozheva., and Obsahuje bibliografii
Biological membrane mimetics, such as liposomes, lipid bilayers and model membranes, are used in a broad range of scientific and technological applications due to the unique physical properties of these amphiphilic aggregates. They serve as platforms for studying soft matter physics of membranes and membrane dynamics, interactions of bilayers with drugs, and effects of various additives of environmental changes. State-of-the-art research takes advantage of the combination of the brilliance of X-ray scattering sources with peculiar properties of neutrons and the power of computer simulations. The advances in chemistry, and in particular the possibility of deuteration, enables improved experimental spatial resolution and the ability to pi-point labels within membranes. It is only a matter of time for many biological functions, which occur at the membrane interface, to be matched with the structural properties of these membranes., Článok referuje o zákonitostiach stavby lipidových membrán a ich interakciách s biologicky aktívnymi molekulami. Vplyv iónov nachádzajúcich sa v prirodzenom prostredí bunkovej membrány, anestetický efekt alkánov a účinok cholesterolu a melatonínu pri zabudovaní do membrány je diskutovaný najmä z pohľadu zmeny štruktúry lipidovej matrice membrány. Štruktúrne výsledky sú získané pomocou experimentálnych prístupov, pričom dôraz sa kladie na pokrok dosiahnutý v metódach využívajúcich moderné zdroje röntgenového žiarenia a neutrónov., Norbert Kučerka., and Obsahuje bibliografii
Male Wistar rats adapted to an artificial light-dark regimen (12 h light: 12 h darkness) were whole-body irradiated with a dose of 14.35 Gy of gamma rays. Irradiation, sham-irradiation and decapitation 30, 60 and 120 min after the exposure were performed between 2000 h and 0100 h in the darkness. The serotonin N-acetyltransferase activity (NAT), the concentration of melatonin, dopamine, norepinephrine and epinephrine were measured in the pineal gland. The serum levels of melatonin and corticosterone were also determined. Ionizing radiation did not change the activity of the key enzyme of melatonin synthesis, NAT, but decreased the concentration of pineal melatonin. The concentration of pineal dopamine and norepinephrine decreased 30 and 120 min after exposure, while the concentration of epinephrine was elevated 30 min after irradiation, though later it was markedly decreased. The serum melatonin level was not changed, but an increase in corticosterone level was observed. In the early period after the exposure, a decrease in pineal melatonin occurred, accompanied by a decrease in pineal catecholamines. On the contrary, in the phase of developed radiation injury the signs of increased melatonin synthesis were observed on days 3 and 4 after the exposure (Kassayova et al. 1993a). The underlying mechanisms require further research.
Factors modulating cardiac susceptibility to ischemia-reperfusion (I/R) are permannetly attracting the attention of experimental cardiology research. We investigated, whether continuous 24 h/day light exposure of rats can modify cardiac response to I/R, NO-synthase (NOS) activity and the level of oxidative load represented by conjugated dienes (CD) concentration. Two groups of male adult Wistar rats were studied: controls exposed to normal light/dark cycle (12 h/day light, 12 h/day dark) and rats exposed to continuous light for 4 weeks. Perfused isolated hearts (Langendorff technique) were exposed to 25 min global ischemia and subsequent 30 min reperfusion. The recovery of functional parameters (coronary flow, left ventricular developed pressure, contractility and relaxation index) during reperfusion as well as the incidence, severity and duration of arrhythmias during first 10 min of reperfusion were determined. The hearts from rats exposed to continuous light showed more rapid recovery of functional parameters but higher incidence, duration and severity of reperfusion arrhythmias compared to controls. In the left ventricle, the NOS activity was attenuated, but the CD concentration was not significantly changed. We conclude that the exposure of rats to continuous light modified cardiac response to I/R. This effect could be at least partially mediated by attenuated NO production., R. Važan, P. Janega, S. Hojná, J. Zicha, F. Šimko, O. Pecháňová, J. Styk, L'. Paulis., and Obsahuje bibliografii