Effects of ectopic pacing on left ventricular repolarization were studied in six anesthetized open-c hest chickens. In each animal, unipolar electrograms were acquired from as many as 98 sites with 14 plunge needles (seven transmural locations between epicardium and endocardium in each needle). Activation-recovery intervals (ARIs), corrected to the cycle length, were used for estimating repolarization. At baseline, the nonuniform ARI distribution in the left ventricle resulted in the apicobasal differences being greater than the transmural gradient. Nonuniform ARI prolongation caused by ectopic pacing resulted in decreasing the transmural repolarization gradient and increasing the differences in th e apex-to-base direction. The basal, but not apical transmural differences contributed to the total left ventricular transmural gradient. The total left ventricular apicobasal gradient was contribute d by the apicobasal differences in mid-myocardial and subendoc ardial layers more than in subepicardial ones. Thus, in in situ chicken hearts, the transmural and apicobasal ARI gradients exist within the left ventricle with the shortest ARIs in the basal subepicardium and the longest ARIs in the subendocardium of th e apical and middle parts of the left ventricle. Apicobasal compar ed to transmural heterogeneity of local repolarization properties contributes more to the total left ventricular repolarization gradient., S. N. Kharin, D. N. Shmakov, N. A. Antonova., and Obsahuje bibliografii
The activity of mitochondrial superoxide dismutase (MnSOD) and cytosol superoxide dismutase (CuZnSOD) was measured in corresponding subcellular fractions prepared from the thymi of intact and chronically gonadectomized (GX) rats of both sexes, as well as of GX male and female rats injected subcutaneously with a single dose of 5 mg estradiol benzoate (EB) and/or 2 mg progesterone (P). Animals were sacrificed 2 h or 24 h following hormone treatment. In the females, the activity of MnSOD in the thymus was stable during the estrous cycle and did not change after ovariectomy. Treatment of GX females with estradiol benzoate resulted 2 h later in a significant elevation of MnSOD activity, whereas 24 h later the activity returned back to control values. On the other hand, treatment of GX females with progesterone had no effect on the MnSOD activity. However, combined hormone treatment, in which EB injection preceded progesterone injection by one hour, enhanced the effect on MnSOD activity similar to that of estradiol benzoate alone. The activity of CuZnSOD in cycling rats was increased in proestrus, whereas removal of the ovaries kept the values at low diestrus and estrus levels. Contrary to MnSOD, CuZnSOD activity did not change after EB treatment of GX females, while progesterone increased the enzyme activity at 2 h and 24 h after hormone treatment. However, combined EB+P treatment proved to be ineffective. In the males, neither MnSOD nor CuZnSOD activity was affected by the removal of testes or by progesterone treatment of GX animals. Only EB injection to GX rats significantly increased CuZnSOD activity 24 h later., J. Kasapović, S.B. Pajović, S. Pejić, J.V. Martinović., and Obsahuje bibliografii
The relationships between exercise and metabolites as well as between exercise and sarcoplasmic reticulum function were studied in gastrocnemius muscle of ovariectomized-trained rats. Prolonged moderate-intensity exercise, treadmill up-hill run for 90 min with a 10° incline, decreased the muscle glycogen content. Exercise until exhaustion further lowered the glycogen concentration to 13 % of the control, together with a significant decrease of ATP and glucose-6-phosphate concentrations. Also, Ag+-induced Ca2+release, measured in whole muscle homogenate, showed a 30 % reduction on exhaustion, while Ca2+ uptake was unaffected by this exercise. ATPase activities, of both homogenate and SR vesicles, and Ca2+ transport in the latter preparation were not altered on exhaustion. It could be concluded from these results that muscular fatigue in ovariectomized rats after aerobic exercise is caused by the change in energy supply and Ca2+ release from the SR, this latter possibly due to metabolites generated by the exercise., I. Gigli, L. E. Bussmann., and Obsahuje bibliografii
Hypertension is a major health problem throughout the world because of its high prevalence and its association with increased risk of cardiovascular disease. Two independent studies discovered a locus conferring susceptibility to essential hypertension on chromosome 2, in the 2p25 region, but the causative gene remains unknown. Grainyhead-like 1 (GRHL1) is one of the genes located in this region. Our experiments determined that the Grhl1-null mice, when fed standard diet, have the same blood pressure as their wild type littermate controls. However, we discovered that blood pressure of these mice increases following high sodium diet and decreases when they are fed low sodium diet, and similar effect s were not observed in the control wild type littermates. This suggests that the Grhl1-null mice are sensitive to the development of salt-sensitive hypertension. Thus it is possible that the GRHL1 gene is involved in the regulation of blood pressure, and it may be the causative gene for the locus of susceptibility to essential hypertension in the 2p25 region., A. Walkowska, M. Pawlak, S. M. Jane, E. Kompanowska-Jezierska, T. Wilanowski., and Obsahuje bibliografii
To assess the possible involvement of mast cells and/or their mediators in inflammatory bowel diseases, the effect of the histamine H1 antagonist Dithiaden was studied on a model of acetic acid-induced colitis in rats. Dithiaden pretreatment by intracolonic administration was found to reduce the extent of acute inflammatory colonic injury. This was manifested by a decrease in the score of gross mucosal injury, by lowered colonic wet weight and by diminished myeloperoxidase activity reflecting reduced leukocyte infiltration. Vascular permeability and gamma-glutamyl transpeptidase activity, elevated by acetic acid exposure, were decreased after Dithiaden pretreatment. The results indicate that locally administered Dithiaden may protect the colonic mucosa against an acute inflammatory attack by interfering with the action of the major mast cell mediator histamine., V. Nosáľová, O. Ondrejičková, J. Pečivová., and Obsahuje bibliografii
Toxic influence of high oxygen concentration on pulmonary function and structures has been known for many years. However, the influence of high oxygen concentration breathing on defensive respiratory reflexes is still not clear. In our previous experiments, we found an inhibitory effect of 100 % oxygen breathing on cough reflex intensity in healthy guinea pigs. The present study was designed to detect the effects of hyperoxia on cough reflex in guinea pigs with allergic airway inflammation. In the first phase of our experiment, the animals were sensitized with ovalbumin. Thirty-two sensitized animals were used in two separate experiments according to oxygen concentration breathing: 100 % or 50 % oxygen for 60 h continuously. In each experiment, one group of animals was exposed to hyperoxia, another to ambient air. The cough reflex was induced both by aerosol of citric acid before sensitization, then in sensitized animals at 24 h and 60 h of exposition to oxygen/air in awake animals, and by mechanical stimulation of airway mucosa in anesthetized animals just after the end of the experiment. In contrast to 50 % oxygen, 100 % oxygen breathing leads to significant decrease in chemically induced cough in guinea pigs with allergic inflammation. No significant changes were present in cough induced by mechanical stimulation of airways., M. Brozmanová, J. Hanáček, M. Tatár, A. Strapková, P. Szépe., and Obsahuje bibliografii
The present experiments were performed to evaluate if increased heart tissue concentration of fatty acids, specifically myristic, palmitic and palmitoleic acids that are believed to promote physiological heart growth, can attenuate the progression of unloading-induced cardiac atrophy in rats with healthy and failing hearts. Heterotopic abdominal heart transplantation (HTx) was used as a model for heart unloading. Cardiac atrophy was assessed from the ratio of the native- to-transplanted heart weight (HW). The degree of cardiac atrophy after HTx was determined on days 7, 14, 21 and 28 after HTx in recipients of either healthy or failing hearts. HTx of healthy hearts resulted in 23±3, 46±3, 48±4 and 46±4 % HW loss at the four time-points. HTx of the failing heart resulted in even greater HW losses, of 46±4, 58±3, 66±2 and 68±4 %, respectively (P<0.05). Activation of “fetal gene cardiac program” (e.g. beta myosin heavy chain gene expression) and “genes reflecting cardiac remodeling” (e.g. atrial natriuretic peptide gene expression) after HTx was greater in failing than in healthy hearts (P<0.05 each time). Exposure to isocaloric high sugar diet caused significant increases in fatty acid concentrations in healthy and in failing hearts. However, these increases were not associated with any change in the course of cardiac atrophy, similarly in healthy and post-HTx failing hearts. We conclude that increasing heart tissue concentrations of the fatty acids allegedly involved in heart growth does not attenuate the unloading-induced cardiac atrophy., M. Pokorný, I. Mrázová, J. Malý, J. Pirk, I. Netuka, Z. Vaňourková, Š. Doleželová, L. Červenková, H. Maxová, V. Melenovský, J. Šochman, J. Sadowski, L. Červenka., and Seznam literatury
The effects of various doses of L-arginine, a nitric oxide substrate, on lithium-pilocarpine-induced seizures were studied in rats. Rats were implanted with chronic, stainless steel screw electrodes epidurally for electrocortical recordings. A control group received 3 mEq/kg LiCl (i.p.) and 24 h later 45 mg/kg pilocarpine HCl (i.p.). Two different experimental procedures were followed: (1) L-arginine was applied in doses of 100 mg/kg, 300 mg/kg or 500 mg/kg (i.p.), 30 min before pilocarpine injection; (2) 300 mg/kg, 500 mg/kg or 1000 mg/kg (i.p.) L-arginine was injected either 5 min or 30 min after the onset of status epilepticus (SE). L-arginine (300 mg/kg) injected 30 min before pilocarpine significantly reduced the percentage of SE, but did not change the latency to SE or 24-hour survival. These parameters were not significantly affected by the 100 mg/kg or 500 mg/kg dose of L-arginine. On the other hand, no dose of L-arginine that was applied after SE had begun, had any significant influence on the seizures. We concluded that L-arginine may prevent seizure activity in some but not all doses, and does not have any effect on the ongoing seizure activity., B. Noyan, G. Güleç., and Obsahuje bibliografii
The aim of this study was to assess carotid baroreflex responses during graded lower body negative pressure (LBNP). In 12 healthy subjects (age 29±4 years) we applied sinusoidal neck suction (0 to -30 mmHg) at 0.1 Hz to examine the sympathetic modulation of the heart and blood vessels and at 0.2 Hz to assess the effect of parasympathetic stimulation on the heart. Responses to neck suction were determined as the change in spectral power of RR-interval and blood pressure from baseline values. Measurements were carried out during progressive applications (0 to -50 mmHg) of LBNP. Responses to 0.1 and 0.2 Hz carotid baroreceptor stimulations during low levels of LBNP (-10 mmHg) were not significantly different from those measured during baseline. At higher levels of LBNP, blood pressure responses to 0.1 Hz neck suction were significantly enhanced, but with no significant change in the RR-interval response. LBNP at all levels had no effect on the RR-interval response to 0.2 Hz neck suction. The unchanged responses of RR-interval and blood pressure to neck suction during low level LBNP at -10 mmHg suggest no effect of cardiopulmonary receptor unloading on the carotid arterial baroreflex, since this LBNP level is considered to stimulate cardiopulmonary but not arterial baroreflexes. Enhanced blood pressure responses to neck suction during higher levels of LBNP are not necessarily the result of a reflex interaction but may serve to protect the circulation from fluctuations in blood pressure while standing., C. M. Brown, M. J. Hecht, B. Neundörfer, M. J. Hilz., and Obsahuje bibliografii