Uni-quantal endplate currents (EPCs) were recorded extracellularly at the frog neuromuscular synapse and their latency dispersions expressed as P90 were estimated in the presence of acetylcholine. Stimulation-evoked EPCs with long release latencies increased in number when acetylcholine was applied. P90, which is designated as the interval between the minimal synaptic delay and the time at which 90 % of all measured uni-quantal EPCs had occurred, was significantly and reversibly increased by 66% from 0.51 ms to 0.85 ms in the presence of 5x10-4 M acetylcholine. This indicates that the evoked release pattern is less synchronous and the increased asynchrony leads to a substantial drop (by 28%) in the amplitude of reconstructed multi-quantal currents., D. Samigullin, E. A. Bukharaeva, E. Nikolsky, S. Adámek, F. Vyskočil., and Obsahuje bibliografii
NG-nitro-D-arginine-methyl ester (D-NAME) is considered to be an inactive enantiomer of L-NAME and is generally used as the negative control for NO synthase inhibition with L-NAME. With the aim to compare the effects of 4-week L-NAME and D-NAME treatments on hemodynamic and cardiovascular structural parameters, four groups of male Wistar rats were investigated: the controls and groups administered 40 and 20 mg/kg/day of L-NAME and 40 mg/kg/day of D-NAME. At the end of the experiment, myocardial NO synthase activity decreased by 42, 24 and 25 %; aortic NO synthase activity decreased by 35, 15 and 13 % vs. controls in the L-NAME 40, L-NAME 20 and D-NAME 40 groups, respectively. The DNA concentrations in the myocardium and the aorta increased significantly after L-NAME and D-NAME treatments. The inhibition of NO synthase was accompanied by a significant elevation in systolic blood pressure in all three groups. The LVW/BW ratio increased by 27, 14 and 13 % vs. controls in the L-NAME 40, L-NAME 20 and D-NAME 40 groups, respectively. The aortic wall mass, measured as the crossectional area, increased by 45, 17 and 25 % vs. controls in the L-NAME 40, L-NAME 20 and D-NAME 40 groups, respectively. Myocardial fibrosis represented 0.94 % in the controls, but 7.96, 4.70 and 5.25 % in L-NAME 40, L-NAME 20 and D-NAME 40 groups, respectively. It is concluded that D-NAME, although less affective than L-NAME, inhibits NO synthase activity resulting in hemodynamic and structural changes in the cardiovascular system similar to the changes induced by half the dose of L-NAME. Thus, the consideration of D-NAME as an inactive enantiomer and its use as the negative control needs to be reevaluated., P. Babál, O. Pecháňová, I. Bernátová., and Obsahuje bibliografii
The need for more long-term studies on helminth communities was addressed by examining changes in composition and diversity of the intestinal helminth component and infracommunities in eels of a small isolated river over 12 years. Examination of samples over one summer season indicated that single samples were representative of community richness in that year. In 1985 the community was species poor (1 species only) and with zero diversity, but by 1996 it comprised six species and all parameters at both levels indicated that it was the richest community yet reported from eels. This overall increase in diversity was not regular or uniform from year to year: rather, the general trend could be reversed in any year(s) and variation between years was considerable. The occurrence of many species was erratic and the identity of the dominant species varied between years. The helminth species that colonised the river contributed to helminth species richness and had an impact on community diversity. It is believed that the overall increase in diversity reflects the changing conditions in the habitat and catchment, but the erratic fluctuations in parameters may reflect the size of the river and the absence of any rescue effects. The findings are compared with the few other long-term studies and it is suggested that the extent of the variation over long periods makes it very difficult to use helminths as indicators of other than general environmental changes or to detect short-term changes due to such specific sources as pollution.
An approach to risk evaluation against the failure of waste deposit sealing layer is given. It is derived from experience gathered with municipal waste deposit closures. Such deposits were monitored in Ce ntral Bohemia in the territory of the Czech Republic. Geodetic observations on such deposits carried out for five to eleven years provided a chance to obtain and interpret continuous deformation data series. Results can increase functional reliability of their superficial sealing and can be used to optimise the time when closure and recultivation should start. The results concern superficial settlement, its development in time and irregularities that are practically very important. Definition of failure criteria that would allow evaluation of limits in irregular deposit se ttlement is relatively difficult and should become a topic for further investigations and discussions., Zdeněk Kudrna., and Obsahuje bibliografické odkazy
Alterations in geometry and structure of coronary arteries have marked consequences on blood flow to the respective area. We evaluated long-term effect of losartan on blood pressure (BP), heart weight/body weight (HW/BW), geometry and structure of septal branch of coronary artery (RS) of young SHR and Wistar rats. Four-week-old Wistar rats and SHR were used. Losartan was administered (20 mg/kg/day) in drinking water by gavage for 5 weeks. BP was measured by plethysmographic method. Cardiovascular system was perfused with a fixative (120 mm Hg). RS was processed for electron microscopy. Wall thickness of intima + media (WT), inner diameter (ID), cross-sectional area of intima + media (CSA), volume dens ities (VD) of endothelial cells (EC), extracellular matrix (ECM) of intima, smooth muscle cells (SMC) and ECM of media were eval uated. BP of 4-week-old SHR did not differ from that of Wistar rats. BP, HW/BW, WT, CSA, WT/ID, CSAs of SMC, ECM of media were increased in 9-week- old SHR, whereas their VD and CSA of EC were decreased. Losartan administration decreased BP and HW/BW in both groups. Geometry of RS was affected only in SHR (reduction of WT, CSA, WT/ID and increased of ID, circumferential tension, VD and CSA of EC). Losartan administration reduced BP and myocardial mass in both groups and beneficially affected geometry and structure of coronary artery in SHR., R. Koprdová, M. Cebová, F. Kristek., and Obsahuje seznam literatury
We studied the effects of long-term administration of molsidomine and pentaerythrityl tetranitrate (PETN) on the cardiovascular system of spontaneously hypertensive rats (SHR). One control and three experimental groups of 10-week-old animals were used: 1) control Wistar rats, 2) SHR, 3) SHR treated with molsidomine in tap water (100 mg/kg/day, by gavage), and 4) SHR treated with PETN in tap water (200 mg/kg/day, by gavage). After six weeks, the content of cGMP in platelets and NO synthase (NOS) activity in aortas were evaluated in the experimental groups. For morphological evaluation the rats were perfused at 120 mm Hg with a glutaraldehyde fixative and the arteries were processed for electron microscopy. Blood pressure and heart weight/body weight ratio (HW/BW) were increased in all experimental groups with respect to the controls. HW/BW was lower in the molsidomine group in comparison to both SHR and PETN-treated group. The platelet content of cGMP was increased and the activity of NOS in the aortas was decreased in the molsidomine and PETN-treated groups. Wall thickness and cross-sectional area of thoracic aorta, carotid artery and coronary artery were increased similarly in all experimental groups compared to the controls, but there were no differences among the experimental groups. We summarize that long-term administration of exogenous NO donors did not improve pathological changes of the cardiovascular system in SHR., F. Kristek, V. Fáberová, I. Varga., and Obsahuje bibliografii
To determine whether the exposure to long term enriched environment (EE) would result in a continuous improvement of neurological recovery and ameliora te the loss of brain tissue after traumatic brain injury (TBI) vs. standard housing (SH). Male Sprague-Dawley rats (300-350 g, n=28) underwent lateral fluid percussion brain injury or SHAM operation. One TBI group was held under complex EE for 90 days, the other under SH. Neuromotor and sensorimotor dysfunction and recovery were assessed after injury and at days 7, 15, and 90 via Composite Neuroscore (NS), RotaRod test, and Barnes Circular Maze (BCM). Cortical tissue loss was assessed using serial brain sections. After day 7 EE animals showed similar latencies and errors as SHAM in the BCM. SH animals performed notably worse with differences still significant on day 90 (p<0.001). RotaRod test and NS revealed superior results for EE animals after day 7. The mean cortical volume was significantly higher in EE vs. SH animals (p=0.003). In summary, EE animals after lateral fluid percussion (LFP) brain injury performed sign ificantly better than SH animals after 90 days of recovery. The window of opportunity may be wide and also lends further credibility to the importance of long term interventions in patients suffering from TBI., M. Maegele, M. Braun, A. Wafaisade, N. Schäfer, M. Lippert-Gruener, C. Kreipke, J. Rafols, U. Schäfer, D. N. Angelov, E. K. Stuermer., and Obsahuje bibliografii
Despite the widespread use of potent immunosuppressive drugs, such as cyclosporin A and mycophenolate mofetil, ongoing and recurrent cellular rejection remain a common problem after heart transplantation. We aimed to describe the long-term effects of conversion from cyclosporine A to tacrolimus in patients with ongoing and recurrent cellular rejection. This was a single-centre retrospective analysis of 17 heart transplant recipients who were switched from cyclosporine A to tacrolimus due to ongoing (5 patients) or recurrent cellular rejection (12 patients). We studied long-term efficacy and safety of this approach. 167 endomyocardial biopsies were performed during a mean followup of 69.1±12.7 months. Thirteen biopsies (7.8 %) in eight patients (47 %) revealed higher grades of acute cellular rejection (Banff 2). However, they were not hemodynamically significant and did not require intravenous antirejection therapy. The mean rejection score was reduced significantly. Conversion to tacrolimus was tolerated in 82 % pts without any significant side effects during a long-term follow-up. In conclusion, the conversion to tacrolimus in heart transplant recipients with ongoing or recurrent acute cellular rejection was safe and effective also during a long-term follow-up., B. Skalická ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Little is known about the effect of chronic angiotensin-converting enzyme inhibition on the catecholamine levels in fowls. In this study, we investigated the effects of chronic lisinopri1 dihydrate (Ld) application on the plasma levels of adrenaline and noradrenaline and on the blood pressure. Lisinopril was given in different concentrations (25, 75 and 250 mg/l drinking water) to the white Leghorn chickens for 9 weeks, while the control group drank tap water only. Twenty-eight hours after the last lisinopril application, arterial blood pressure (BP), plasma adrenaline and noradrenaline levels, plasma renin (PRA) and plasma angiotensin-converting enzyme (ACE) activities were determined. In all concentrations, lisinopril significantly increased PRA and decreased ACE activities. Arterial BP was decreased only in the group receiving high lisinopril concentration (Controls 119±10.27, Ld3 98±5.4 mm Hg). However, the lower lisinopril concentrations did not alter arterial BP compared to the control group. Plasma noradrenaline levels were decreased in a concentration-dependent manner (47-58 %), but plasma adrenaline levels remained unchanged. The heart weight/body weight ratio was not changed in any of the lisinopril-treated groups. The persistent decrease in the blood pressure after lisinopril treatment was not directly related to a decrease of plasma ACE activity or plasma noradrenaline levels. Its mechanism still remains to be elucidated., H. S. Ozdemir, H. E. Aksulu, F. Karataş, B. Ustündag, I. Bingöl., and Obsahuje bibliografii
It has been suggested that thiazolidinediones (TZDs) ameliorate insulin resistance in muscle tissue by suppressing muscle lipid storage and the activity of novel protein kinase C (nPKC) isoforms. To test this hypothesis, we analyzed long-term metabolic effects of pioglitazone and the activation of nPKC-ε and -θ isoforms in an animal model of the metabolic syndrome, the spontaneously hypertensive rat (a congenic SHR strain with wild type Cd36 gene) fed a diet with 60 % sucrose from the age of 4 to 8 months. Compared to untreated controls, pioglitazone treatment was associated with significantly increased basal (809±36 vs 527±47 nmol glucose/g/2h, P<0.005) and insulinstimulated glycogenesis (1321±62 vs 749±60 nmol glucose/g/2h, P<0.0001) in isolated gastrocnemius muscles despite increased concentrations of muscle triglycerides (3.83±0.33 vs 2.25±0.12 μmol/g, P<0.005). Pioglitazone-treated rats exhibited significantly increased membrane/total (cytosolic plus membrane) ratio of both PKC-ε and PKC-θ isoforms compared to untreated controls. These results suggest that amelioration of insulin resistance after long-term pioglitazone treatment is associated with increased activation of PKC-ε and -θ isoforms in spite of increased lipid concentration in skeletal muscles., I. Marková ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy