The aim of the present study was to investigate changes in the activity of branched-chain a-keto acid dehydrogenase (BCKAD) in skeletal muscle and the heart during brief and prolonged starvation. Fed control rats and rats starved for 2, 4 and 6 days were anesthetized with pentobarbital sodium before heart and hindlimb muscles were frozen in situ by liquid nitrogen. Basal (an estimate of in vivo activity) and total (an estimate of enzyme amount) BCKAD activities were determined by measuring the release of 14CO2 from a-keto[1-14C]isocaproate. The activity state of BCKAD complex was calculated as basal activity in percentages of total activity. Both basal and total activities and the activity state of the BCKAD were lower in skeletal muscles than in the heart. In both tissues, starvation for 2 or 4 days caused a decrease in the basal activity and activity state of BCKAD. On the contrary, in the heart and muscles of animals starved for 6 days a marked increase in basal activity and activity state of BCKAD was observed. The total BCKAD activity was increasing gradually during starvation both in muscles and the heart. The increase was significant in muscles on the 4th and 6th day of starvation. The demonstrated changes in BCKAD activity indicate significant alterations in branched-chain amino acid (BCAA) and protein metabolism during starvation. The decreased BCKAD activity in skeletal muscle and heart observed on the 2nd and 4th day of starvation prevents the loss of essential BCAA and is an important factor involved in protein sparing. The increased activity of BCKAD on the 6th day of starvation indicates activated oxidation of BCAA and accelerated protein breakdown., M. Holeček., and Obsahuje bibliografii
Abundant evidence indicates that ATP and adenosine act as neurotransmitters or co-transmitters, influencing nerve cell physiology in various ways. Therefore, regulation of ATP-metabolizing enzymes is essential for the normal development and function of neuronal tissue. In the present study we have examined the effect of gonadal (OVX) or adrenal (ADX) steroid hormone deprivation on the activity and expression of synaptic membrane ecto-ATPase in three extrahypothalamic brain areas of female rats, primarily not associated with reproductive function. It was shown that OVX significantly increased ecto-ATPase activity and the relative abundance of this enzyme in the hippocampal (Hip) and caudate nucleus (CN), but not in brain stem (BS) membrane preparations. ADX was followed by an upregulation of the enzyme activity and its relative abundance in all the brain areas investigated. The highest enzyme activity and the most profound effects of OVX and ADX were detected in the CN. The results obtained indicate that ADX and OVX upregulate the expression of ecto-ATPase, potentiating the production of adenosine in synaptic cleft thus modulating the activity of numerous neurotransmitter systems in distinct areas of the CNS., N. Nedeljkovic, V. Djordjevic, A. Horvat, G. Nikezic, D.T. Kanazir., and Obsahuje bibliografii
Activation of sublobule IX-b of the cerebellar vermis evokes hypotension, bradycardia and decrease of the phrenic nerve activity in the anesthetized animal. Cardiac performance during the isovolumic phases of systole and relaxation can be evaluated by dP/dt max, Vpm, dP/dt/DP40 and τ, respectively. In the present study, we evaluated the changes on cardiac function evoked by the stimulation of sublobule IX-b. New Zealand white rabbits were anesthetized, paralyzed and artificially ventilated. A posterior craniotomy was made to reveal and stimulate the cerebellar uvula (4 s train; 50 Hz; 1 ms; 20 μA). The femoral artery and veins were cannulated and a Swan-Ganz catheter was advanced in the upper abdominal aorta to control afterload when inflating the balloon. The left ventricle was catheterized with a Millar catheter. Blood pressure, heart rate, left ventricular pressure were monitored. Results showed a significant decrease on sublobule IX-b stimulation of all the indices of systolic function and an increase of τ indicating a decrease in the speed of the relaxation. These data provide the first evidence of the influence of sublobule IX-b on cardiac function. They may contribute to the understanding of the origin the cardiovascular changes that were observed in two patients with vermian and paravermian hemorrhage., I. Rochas, V. Gonçalves, M. J. Bettencourt, L. Silva-Carvalho., and Obsahuje bibliografii a bibliografické odkazy
The aim of this work was to study the effect of the daily ingestion of a purified anthocyanin extract from red grape skin on rat serum antioxidant capacity (ORAC) and its safety for the intestinal epithelium. The study was carried out in rats orally administered with the extract for 10 days in either normal physiological conditions or exposed to a pro-oxidant chemical (CCl4). The oral administration of the extract significantly (P<0.05) enhanced the ORAC va lue of the deproteinised serum of about 50 % after 10 days of ingestion. Anthocyanin administration was also able to reverse completely the decrease in the serum ORAC activity induced by the CCl4 treatment. Experiments with Ussing chamber mounted intestine allowed to exclude any toxicity of the extract for the intestinal epithelium. In conclusion, our results demonstrate that the purified anthocyanin extract from red grape skin e nhances the total antioxidant capacity of the serum in either normal physiological condition or during oxidative stress induction, revealing a protective role against the decrease in the serum antioxidant capacity induced by a pro-oxidant compound., M. G. Lionetto ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Creatine (Cr) is recommended as a dietary supplement especially for athletes but its therapeutic potential is also discussed. It is assumed that human body uses Cr for the formation of phosphocreatine, which is nece ssary for muscular work as a source of energy. Production of Cr in a body is closely connected to methionine cycle where guanidinoacetate (GAA) is in a final step methylated from S-adenos ylmethionine (SAM). Increased availability of SAM for phosphatidylcholine (PC) and sarcosine synthesis can potentially stimulate endogenous production of betaine a thus methylation of homocysteine (HCy) to form methionine. Our subject who was methylenetetrahydrofolate reductase ( MTHFR ) 677TT homozygote lowered plasma HCy from 33.3 μmol/l to 17.1 μmol/l following one-month Cr supplementation (5 g/day) opposite to 677CC and CT genotypes whose HCy levels tended to increase (but still in normal ranges). We suppose that Cr supplementation stimulates pathways leading to production of sarcosine which can serve to regenerate tetrahydrofolate (THF) to form 5,10-methylene-THF. This could potentially increase MTHFR enzyme activity which may later result in increased HCy methylation. Cr supplementation significantly effects metabolism of one carbon unit and potentially lower body's demands for methyl groups. This could be beneficial as in the case of reduced enzyme activity such as MTHFR 677C/T polymorphism., M. Petr, M. Šteffl, E. Kohlíková., and Obsahuje bibliografii a bibliografické odkazy
Time delay in the mediation of ventilation (VE) by arterial CO2 pressure (PaCO2) was studied during recovery from short impulse-like exercises with different work loads of recovery. Subjects performed two tests including 10-s impulse like exercise with work load of 200 watts and 15-min recovery with 25 watts in test one and 50 watts in test two. V . E, end tidal CO2 pressure (PETCO2) and heart rate (HR) were measured continuously during rest, warming up, exercise and recovery. PaCO2 was estimated from PETCO2 and tidal volume (VT). Results showed that predicted arterial CO2 pressure (PaCO2 pre) increased during recovery in both tests. In both tests, VE increased and peaked at the end of exercise. VE decreased in the first few seconds of recovery but started to increase again. The highest correlation coefficient between PaCO2 pre and V . E was obtained in the time delay of 7 s (r=0.854) in test one and in time delays of 6 s (r=0.451) and 31 s (r=0.567) in test two. HR was significantly higher in test two than in test one. These results indicate that PaCO2 pre drives VE with a time delay and that higher work intensity induces a shorter time delay., R. Afroundeh, T. Arimitsu, R. Yamanaka, C. S. Lian, K. Shirakawa, T. Yunoki, T. Yano., and Obsahuje bibliografii
Spontaneous activity of cortical neurons exhibits alternative fluctuations of membrane potential consisting of phased depolarization called "up-state" and persistent hyperpolarization called "down-state" during slow wave sleep and anesthesia. Here, we examined the effects of sound stimuli (noise bursts) on neuronal activity by intracellular recording in vivo from the rat auditory cortex (AC). Noise bursts increased the average time in the up-state by 0.81±0.65 s (rang e, 0.27-1.74 s) related to a 10 s recording duration. The rise times of the spontaneous up-events averaged 69.41±18.04 ms (range, 40.10-119.21 ms), while those of the sound-evoked up-events were significantly shorter (p<0.001) averaging on ly 22.54±8.81 ms (range, 9.31- 45.74 ms). Sound stimulation did not influence ongoing spontaneous up-events. Our data suggest that a sound stimulus does not interfere with ongoing spontaneous neuronal activity in auditory cortex but can evoke new depolarizations in addition to the spontaneous ones., Y. Zhang ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
We compared the effects of adaptation to intermittent high altitude (IHA) hypoxia of various degree and duration on ischemia-induced ventricular arrhythmias in rats. The animals were exposed to either relatively moderate hypoxia of 5000 m (4 or 8 h/day, 2-3 or 5-6 weeks) or severe hypoxia of 7000 m (8 h/day, 5-6 weeks). Ventricular arrhythmias induced by coronary artery occlusion were assessed in isolated buffer-perfused hearts or open-chest animals. In the isolated hearts, both antiarrhythmic and proarrhythmic effects were demonstrated depending on the degree and duration of hypoxic exposure. Whereas the adaptation to 5000 m for 4 h/day decreased the total number of premature ventricular complexes (PVCs), extending the daily exposure to 8 h and/or increasing the altitude to 7000 m led to opposite effects. On the contrary, the open-chest rats adapted to IHA hypoxia exhibited an increased tolerance to arrhythmias that was even more pronounced at the higher altitude. The distribution of PVCs over the ischemic period was not altered by any protocol of adaptation. It may be concluded that adaptation to IHA hypoxia is associated with enhanced tolerance of the rat heart to ischemic arrhythmias unless its severity exceeds a certain upper limit. The opposite effects of moderate and severe hypoxia on the isolated hearts cannot be explained by differences in the occluded zone size, heart rate or degree of myocardial fibrosis. The proarrhythmic effect of severe hypoxia may be related to a moderate left ventricular hypertrophy (27 %), which was present in rats adapted to 7000 m but not in those adapted to 5000 m. This adverse effect can be overcome by an unknown protective mechanism(s) that is absent in the isolated hearts., G. Asemu, J. Neckář, O. Szárszoi, F. Papoušek, B. Ošťádal, F. Kolář., and Obsahuje bibliografii
Adenosine is known to influence different kinds of cells, including β-cells of the pancreas. However, the role of this nucleoside in the regulation of insulin secretion is not fully elucidated. In the present study, the effects of adenosine A1 receptor antagonism on insulin secretion from isolated rat pancreatic islets were tested using DPCPX, a selective adenosine A1 receptor antagonist. It was demonstrated that pancreatic islets stimulated with 6.7 and 16.7 mM glucose and exposed to DPCPX released significantly more insulin compared with islets incubated with glucose alone. The insulin-secretory response to glucose and low forskolin appeared to be substantially pote ntiated by DPCPX, but DPCPX was ineffective in the presence of glucose and high forskolin. Moreover, DPCPX failed to change insulin secretion stimulated by the combination of glucose and dibutyryl-cAMP, a non-hydrolysable cAMP analogue. Studies on pancreatic islets also revealed that the potentiating effect of DPCPX on glucose-induced insulin secretion was attenuated by H-89, a selective inhibitor of protein kinase A. It was also demonstrated that fo rmazan formation, reflecting metabolic activity of cells, was enhanced in islets exposed to DPCPX. Moreover, DPCPX was found to increase islet cAMP content, whereas ATP was not significantly changed. These results indicate that adenosine A1 receptor blockade in rat pancreatic islets potentiates insulin secretion induced by both physiological and supraphysiological glucose concentrations. This effect is proposed to be due to increased metabolic activity of cells and increased cAMP content., A. Zywert, K. Szkudelska, T. Szkudelski., and Obsahuje bibliografii a bibliografické odkazy
Mitochondrial dysfunction and accumulation of oxidative damage have been implicated to be the major factors of aging. However, data on age-related changes in activities of mitochondrial electron transport chain (ETC) complexes remain controversial and molecular mechanisms responsible for ETC dysfunction are still largely unknown. In this study, we examined the effect of aging on activities of ETC complexes and oxidative damage to proteins and lipids in cardiac mitochondria from adult (6-month-old), old (15-month-old) and senescent (26-month-old) rats. ETC complexes I-IV displayed different extent of inhibition with age. The most significant decline occurred in complex IV activity, whereas complex II activity was unchanged in old rats and was only slightly reduced in senescent rats. Compared to adult, old and senescent rat hearts had significantly higher levels of malondialdehyde, 4-hydroxynonenal (HNE) and dityrosine, while thiol group content was reduced. Despite marked increase in HNE content with age (25 and 76 % for 15-and 26-month-old rats, respectively) Western blot analysis revealed only few HNE-protein adducts. The present study suggests that non-uniform decline in activities of ETC complexes is due, at least in part, to mitochondrial oxidative damage; however, lipid peroxidation products appear to have a limited impact on enzyme functions., Z. Tatarková ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy