We have tested the hypothesis that neurons of both the ventral reticular nucleus and the adjacent parts of the lateral tegmental field (LTF) may be important for the production of motor programs associated with cough, expiration and aspiration reflexes. Our studies were conducted on non-decerebrate, spontaneously breathing cats under pentobarbitone anesthesia. Dysfunction of the medullary LTF region above the obex, produced by uni- or bilateral injections of kainic acid (a neurotoxin), regularly abolished the cough reflex evoked by mechanical stimulation of both the tracheobronchial and laryngeal regions and in most cases also the expiration reflex induced from the glottal area. However, some electrical activity still occurred in the neurogram of the recurrent laryngeal nerve during probing the laryngeal and glottal regions. Interestingly, the aspiration reflex elicited from the nasopharynx regularly persisted, although with lower intensity after the LTF lesion. Nevertheless, successive midcollicular decerebration performed in four cats also abolished the aspiration reflex. These experiments demonstrate the importance of medullary LTF neurons for the normal occurrence of cough and expiration reflexes. One possible explanation for the elimination of these expulsive processes is that the blockade of the LTF neurons may remove an important source of a facilitatory input to the brainstem circuitries that mediate cough and expiration reflexes. In addition, the potential importance of the mesencephalic reticular formation for the occurrence of the aspiration reflex and the role of the LTF in modulating both the eupnoeic breathing and the blood pressure are also discussed., J. Jakuš, A. Stránsky, I. Poliaček, H. Baráni, Ľ. Bošeľová., and Obsahuje bibliografii
Measurements of ryanodine receptor (RyR) activity during dynamic changes of calcium concentration have suggested that RyR has at least four calcium binding sites, and that activation transpires as an increase in the activity within the high open probability H-mode. Binding of several Ca2+ ions within the H-mode should manifest itself in the steady-state RyR activity by the presence of multiple closed times. However, previously only two closed times were detected in the H-mode of RyR activity. Here we recorded steady-state activity of single cardiac RyRs with high temporal resolution and compared it to data simulated under the same conditions using our previously published model of RyR gating. At a 10 kHz resolution, the closed time histograms of both experimental and simulated data had three exponential components. The closed times of simulated data were not significantly different from those obtained experimentally. After filtering at 2 kHz, only two exponential closed time components with time constants not significantly different from those previously published could be detected in both experimental and simulated records. The conformity of the steady-state experimental data to the model derived from the dynamic data provides further support for the idea that RyRs need binding of multiple Ca2+ ions to open., M. Dura, I. Zahradník, A. Zahradníková., and Obsahuje bibliografii
MK-801 impaired social recognition potency of adult male rats when given immediately after the initial interaction with a juvenile rat. Administration of kynurenic acid prior to the initial interaction protected the adults against recognition deficits induced by MK-801. When re-exposed at a delay of 30 min to the familiar juvenile, social investigation in the adults was significantly reduced. Thus, the adults are able to remember olfactory stimuli emitted by juvenile con-specifics., Z. Hliňák, I. Krejčí., and Obsahuje bibliografii
Previous studies in our laboratory reported L-malate as a free radical scavenger in aged rats. To investigate the antioxidant mechanism of L-malate in the mitochondria, we analyzed the change in gene expression of two malate-aspartate shuttle (MAS)-related carried proteins (A GC, aspartate/glutamate carrier and OMC, oxoglutarate/malate carrier) in the inner mitochondrial membrane, and three antioxidant enzymes (CAT, SOD, and GSH-Px) in the mitochondria. The changes in gene expression of these proteins and enzymes were examined by real-time RT-PCR in the heart and liver of aged rats treated with L-malate. L-malate was orally administered in rats continuously for 30 days using a feeding atraumatic needle. We found that the gene expression of OMC and GSH-Px mRNA in the liver increased by 39 % and 38 %, respectively, in the 0.630 g/kg L-malate treatment group than that in the control group. The expression levels of SOD mRNA in the liver increased by 39 %, 56 %, and 78 % in the 0.105, 0.210, and 0.630 g/kg L-malate treatment groups, respectively. No diffe rence were observed in the expression levels of AGC, OMC, CAT, SOD, and GSH-Px mRNAs in the heart of rats between the L-malate treatment and control groups. These results predicted that L-malate may increase the antioxidant capacity of mitochondr ia by enhancing the expression of mRNAs involved in the MAS and the antioxidant enzymes., X: Zeng, J. Wu, Q. Wu, J. Zhang., and Obsahuje bibliografii
The intracellular levels of antioxidant and free radical scavenging enzymes are gradually altered during the aging process. An age-dependent increase of oxidative stress occurring throughout the lifetime is hypothesized to be the major cause of aging. The current study examined the effects of L-malate on oxidative stress and antioxidative defenses in the liver and heart of aged rats. Sprague-Dawley male rats were randomly divided into four groups, each group consisting of 6 animals. Group Ia and Group IIa were young and aged control rats. Group Ib and Group IIb were young and aged rats treated with L-malate (210 mg/kg body weight per day). L-malate was orally administrated via intragastric canula for 30 days, then the rats were sacrificed and the liver and heart were removed to determine the oxidant production, lipid peroxidation and antioxidative defenses of young and aged rats. Dietary L-malate reduced the accumulation of reactive oxygen species (ROS) and significantly decreased the level of lipid peroxidation in the liver and heart of the aged rats. Accordingly, L-malate was found to enhance the antioxidative defense system with an increased activity of antioxidant enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GPx) and increased glutathione (GSH) levels in the liver of aged rats, a phenomenon not observed in the heart of aged rats. Our data indicate that oxidative stress was reversed and the antioxidative defense system was strengthened by dietary supplementation with L-malate., J.-L. Wu, Q.-P. Wu, X.-F. Yang, M.-K. Wei, J.-M. Zhang, Q. Huang, X.-Y. Zhou., and Obsahuje bibliografii a bibliografické odkazy
Reactive oxygen species (ROS) have been implicated in the mechanism of postischemic contractile dysfunction, known as myocardial stunning. In this study, we examined protective effects of antioxidant enzymes, superoxide dismutase (SOD) and catalase, against ischemia/reperfusion-induced cardiac dysfunction and inhibition of Na+,K+-ATPase activity. Isolated Langendorff-perfused rabbit hearts were subjected to 15 min of global normothermic ischemia followed by 10 min reperfusion. The hearts treated with SOD plus catalase did not show significant recovery of left ventricular (LV) end-diastolic pressure compared with untreated ischemic reperfused hearts. Treatment with antioxidants had no protective effects on developed LV pressure or its maximal positive and negative first derivatives (±LVdP/dt). Myocardial stunning was accompanied by significant loss in sarcolemmal Na+,K+-ATPase activity and thiol group content. Inhibition of enzyme activity and oxidation of SH groups were not prevented by antioxidant enzymes. These results suggest that administration of SOD and catalase in perfusate do not protect significantly against cardiac dysfunction in stunned rabbit myocardium., P. Kaplán, M. Matejovičová, P. Herijgers, W. Flameng., and Obsahuje bibliografii a bibliografické odkazy
The impact of environmental pollution at the place of residence of pregnant women and of their smoking habits on the cellular energy metabolism of placental tissue was investigated. Samples of full-term placentas were randomly collected from two environmentally different regions of Slovakia (Bratislava, Stará Ľubovňa) and the activity of lactate dehydrogenase (LDH) was measured. Our results showed enhanced LDH activity in the placenta that was dependent on both the type of environmental pollutants at the place of residence and the smoking habits during pregnancy. The enhanced LDH activity may reflect hypoxic conditions due to the accumulation of heavy metals and toxic compounds of tobacco smoke in the placental tissue. A high content of heavy metal particles, found in placental samples from Stará Ľubovňa in our previous studies, might contribute to the increased LDH activity in placentas from this region. We hypothesize that fine metal particles deposited in the placental tissue might be phagocytozed by the syncytiotrophoblast, thus contributing to the decreased oxygen level in placental tissue., A. Kaiglová, E. Reichrtová, A. Adamčáková, L. Wsólová., and Obsahuje bibliografii
Spontaneously hypertensive rats (SHR) are characterized by enhanced nifedipine-sensitive component of sympathetic vasoconstriction. Our study tried to elucidate the mechanisms responsible for long-term reduction of blood pressure (BP) in SHR subjected to early transient captopril treatment. Adult untreated SHR aged 30-34 weeks were compared with animals subjected to chronic captopril treatment for 6 weeks either in youth (between 4 and 10 weeks of age) or in adulthood (between 24 and 30 weeks of age). Antihypertensive effects of captopril were more pronounced in young than adult SHR. This was due to greater attenuation of sympathetic and nifedipine-sensitive BP components and prevention of residual BP rise in young captopril-treated SHR in which the reductions of nifedipine-sensitive BP component and residual BP persisted for 20 weeks after captopril withdrawal. The magnitude of nifedipine-sensitive component of sympathetic vasoconstriction is decisive for BP maintenance not only in untreated SHR but also in SHR during active captopril treatment by or after its withdrawal., J. Zicha, Z. Dobešová,J. Kuneš., and Obsahuje bibliografii a bibliografické odkazy