To determine the role of postinspiratory inspiratory activity of the diaphragm in the biphasic ventilatory response to hypoxia in unanesthetized rats, we examined diaphragmatic activity at its peak (DI), at the end of expiration (DE), and ventilation in adult unanesthetized rats during poikilocapnic hypoxia (10 % O2) sustained for 20 min. Hypoxia induced an initial increase in ventilation followed by a consistent decline. Tidal volume (VT), frequency of breathing (fR), DI and DE at first increased, then VT and DE decreased, while fR and DI remained enhanced. Phasic activation of the diaphragm (DI - DE) increased significantly at 10, 15 and 20 min of hypoxia. These results indicate that 1) the ventilatory response of unanesthetized rats to sustained hypoxia has a typical biphasic character and 2) the increased end-expiratory activity of the diaphragm limits its phasic inspiratory activation, but this increase cannot explain the secondary decline in tidal volume and ventilation., H. Maxová, M. Vízek., and Obsahuje bibliografii
The production of the pineal hormone melatonin is synchronized with day-night cycle via multisynaptic pathway including suprachiasmatic nucleus linking several physiological functions to diurnal cycle. The recent data indicate that impaired melatonin production is involved in several cardiovascular pathologies including hypertension and ischemic heart disease. However, the mechanisms of melatonin effect on cardiovascular system are still not completely understood. The activation of melatonin receptors on endothelial and vascular smooth muscle cells and antioxidant properties of melatonin could be responsible for the melatonin effects on vascular tone. However, the data from in vitro studies are controversial making the explanation of the melatonin effect on blood pressure in vivo difficult. In vivo, melatonin also attenuates sympathetic tone by direct activation of melatonin receptors, scavenging free radicals or increasing NO availability in the central nervous system. The central and peripheral antiadrenergic action of chronic melatonin treatment might eliminate the mechanisms counter-regulating decreased blood pressure, providing thus additional cardioprotective mechanism. The extraordinary antioxidant activity and antilipidemic effects of melatonin may enhance the modulation of blood pressure by melatonin and probably play the most important role in the amelioration of target organ damage by chronic melatonin treatment. Further investigation of these mechanisms should provide novel knowledge about pathophysiological mechanisms of cardiovascular diseases, additional explanation for their circadian and seasonal variability and potentially generate new impulses for the development of therapeutic arsenal., Ľ. Paulis, F. Šimko., and Obsahuje bibliografii a bibliografické odkazy
The goal of the research is to investigate the special effect of ovarian-menstrual cycle phases on the level of women’s blood pressure and characteristics of Mayer waves. 77 women aged 18-19 were tested under condition close to the state of basal metabolism in follicular phase (I), ovulation (II) and luteal phase (III) of ovarian-menstrual cycle. In phases II and III, the increase of mean and diastolic blood pressure level, in comparison with phase I in the prone position at rest and with psycho-emotional loading, were observed. The distinctions between variation parameters of R-R interval duration, stroke volume and its synchronization in phases II and III, in comparison with phase I, were observed in the prone position at rest, during tilt-test and with psycho-emotional loading. The substantial level of relationship between the power of Mayer waves and mean and diastolic blood pressure, mainly in phase I under conditions of all types, is observed. The maximum peak amplitude of stroke volume spectrogram is associated with pressure levels in the range of 0.04-0.15 Hz (ρ from -0.33 to -0.64). The obtained results indicate the possible participation of spontaneous baroreflex sensitivity characteristics in keeping blood pressure level in women., O. I. Lutsenko, S. O. Kovalenko., and Obsahuje bibliografii
Type 2 diabetes mellitus (T2DM) is associated with increased fracture risk; the underlying mechanism remains unexplained. This study aimed to investigate the relationships between body composition and bone and glucose metabolism in postmenopausal women wit h T2DM. Dual-energy X-ray absorptiometry was used to measure bone mineral density (BMD) and body composition. A total of 68 postme nopausal women with T2DM and 71 controls were eligible for the study. In contrast to normal BMD in T2DM, a similar prevalence of low-trauma fractures was observed in both groups. T2DM women had significantly higher Trunk fat% and A/G ratio and significantly lower Legs LM% and Legs FM%. Legs LM% was significantly lower in fractured T2DM group and negatively correlated with glycaem ia and HbA1c (p<0.01). Serum osteocalcin was significantly lower in T2DM and inversely correlated with FM%, Trunk FM% and A/G ratio (p<0.01) and positively correlated with Legs FM% and total LM% (p<0.05). In conclusion, abdominal obesity and decrease in mu scle mass may contribute to low bone formation in T2DM women. Further research is needed to unravel underlying pathophysiological mechanisms and to determine whether maintenance of muscle mass, especially in the lower extremities and/or reduction of centra l fat mass can prevent fractures., I. Raška Jr., M. Rašková, V. Zikán, J. Škrha., and Obsahuje bibliografii
In the present paper we describe changes of anatomical parameters in inbred Lewis strain rats, namely their body weight, body weight gain per week, absolute and relative heart, thyroid gland and skeletal muscle weights, that are assumed to reflect experimentally altered thyroid status. The hyperthyroid state was induced by DL-thyroxine or Na 3,3',5-triiodo-L-thyronine, while methimazole was employed for inducing hypothyroidism. We have found that when compared to euthyroid rats, hypothyroidism resulted in a significantly lower body weight gain, absolute and relative heart weight and, in contrast, in a significant increase of absolute and relative thyroid gland weight. On the other hand, hyperthyroidism led to a significant increase of absolute and relative heart weight and to a significant reduction of absolute and relative thyroid gland weight. However, the body mass was not significantly altered in hyperthyroidism as compared with euthyroid rats. We conclude that our protocol leads to chronic hyper- or hypothyroidism as demonstrated by body, heart and thyroid gland weight changes. These anatomical data can thus be utilized as supplemental criteria for the assessment of the thyroid state of experimental rats., T. Soukup, G. Zachařová, V. Smerdu, I. Jirmanová., and Obsahuje bibliografii
The aim of the current study was to clarify the effect of high sucrose diet (HSD) on bile formation (BF) in rats with hereditary hypertriglyceridemia (HHTg). Potentially positive effects were studied for boldine, a natural choleretic agent. Administration of HSD to HHTg rats led to increased triglyceride deposition in the liver. HSD reduced BF as a consequence of decreased biliary secretion of bile acids (BA) and glutathione. Responsible mechanism was down-regulation of hepatic transporters for BA and glutathione, Bsep and Mrp2, respectively. Moreover, gene expressions of transporters for other constituents of bile, namely Abcg5/8 for cholesterol, Abcb4 for phospholipids, and Oatp1a4 for xenobiotics, were also reduced by HSD. Boldine partially attenuated cholestatic effect of HSD by promotion of biliary secretion of BA through up-regulation of Bsep and Ntcp, and by increase in biliary secretion of glutathione as a consequence of its increased hepatic disposition. This study demonstrates mechanisms of impaired BF during nonalcoholic fatty liver disease induced by HSD. Altered function of responsible transporters suggests also potential for changes in kinetics of drugs, which may complicate pharmacotherapy in subjects with high intake of sucrose, and with fatty liver disease. Sucrose induced alterations in BF may be alleviated by administration of boldine., M. Zagorova, A. Prasnicka, Z. Kadova, E. Dolezelova, L. Kazdova, J. Cermanova, L. Rozkydalova, M. Hroch, J. Mokry, S. Micuda., and Obsahuje bibliografii
The peak bone mass and the rate of bone loss are in part genetically determined. It has been suggested that bone mineral density (BMD) may be related to allelic variation in the apolipoprotein E (ApoE) gene locus. ApoE is important in the receptor-mediated clearance of chylomicron particles from the plasma, Apo E4 having the highest and Apo E2 the lowest receptor affinity. Chylomicrons are the main carrier of vitamin K in the plasma; vitamin K plays an important role in the carboxylation of osteocalcin. We have tested the hypothesis that persons with E4 variant would have lower BMD and increased bone turnover than those with E2 variant. A total of 18 ApoE 2/2 and ApoE 4/4 homozygotes were selected from 873 patients who were examined for the ApoE genotype. BMD in lumbar vertebral, femoral neck and distal forearm was measured and plasma concentrations of osteocalcin and C-terminal fragments of collagen (CTx) were determined. BMD values (expressed as T-score) at the three specified sites were -0.12± 1.72, -0.52± 1.32 and -0.52± 0.81 in ApoE 2/2 group and -0.24± 1.22, 0.00± 0.84 and -0.17± 1.07 in the ApoE 4/4 group. Plasma osteocalcin and CTx were within normal limits in both groups. In conclusion, we did not observe any association of ApoE genotype with BMD and biochemical markers of bone metabolism in ApoE 2/2 and ApoE 4/4 homozygotes., T. Štulc, R. Češka, A. Hořínek, J. Štěpán., and Obsahuje bibliografii
Bone is a target tissue for hormones, such as the sex steroids, parathormon, vitamin D, calcitonin, glucocorticoids, and thyroid hormones. In the last decade, other “non-classic” hormones that modulate the bone tissue have been identified. While incretins (GIP and GLP-1) inhibit bone remodeling, angiotensin acts to promote remodeling. Bone morphogenetic protein (BMP) has also been found to have anabolic effects on the skeleton by activating bone formation during embryonic development, as well as in the postnatal period of life. Bone has also been identified as an endocrine tissue that produces a number of hormones, that bind to and modulate extra-skeletal receptors. Osteocalcin occupies a central position in this context. It can increase insulin secretion, insulin sensitivity and regulate metabolism of fatty acids. Moreover, osteocalcin also influences phosphate metabolism via osteocyte-derived FGF23 (which targets the kidneys and parathyroid glands to control phosphate reabsorption and metabolism of vitamin D). Finally, osteocalcin stimulates testosterone synthesis in Leydig cells and thus may play some role in male fertility. Further studies are necessary to confirm clinically important roles for skeletal tissue in systemic regulations., I. Zofkova., and Obsahuje bibliografii
We investigated the renal response to direct renal nerve stimulation, 2 weeks following reversal of 24-h unilateral (left) ureteric obstruction. Renal nerve stimulation caused a 13-15 % fall in renal blood flow, in 4 groups of anesthetized rats following ureteric obstruction (n=9) or a sham operation (n=7) both with (n=9) and without (n=7) treatment with the mixed ETA/B receptor antagonist, bosentan. In the sham-operated rats, renal nerve stimulation did not change glomerular filtration rate but reduced urine flow rate (37±3 %, P<0.001), and absolute (38±4 %, P<0.001) and fractional (35±5 %, P<0.01) sodium excretion. Following unilateral ureteric obstruction, renal nerve stimulation increased glomerular filtration rate by 22±3 % (P<0.01), but reduced urine flow rate (14±2 %, P<0.001) and fractional sodium excretion (23±5 %, P<0.01). Bosentan treatment had no effect on baseline or renal responses to renal nerve stimulation in the sham group but normalized the renal response to renal nerve stimulation in the unilateral ureteric obstruction group. We conclude that 14 days after a 24-h period of unilateral ureteric obstruction there is an increase in GFR in response to direct renal nerve stimulation, which is due, in part, to the actions of endothelin at the time of obstruction., F. T. Hammad, A. M. Wheatley, G. Davis., and Obsahuje bibliografii
Functional magnetic resonance imaging (fMRI) was used to demonstrate the brain activation during volitional control of breathing in nine healthy human subjects. This type of breathing was induced by acoustic stimuli dictating the respiratory frequency. During the period of dictated breathing not only the frontal and temporal lobes of the brain, but also the parietal lobes were bilaterally activated. The frontal lobe was activated bilaterally in all subjects, with frequent activation of Brodmann areas 4 and 6. In the parietal lobe, activation could mostly be demonstrated in gyrus postcentralis and the same was true for area 22 in the temporal lobe., V. Šmejkal, R. Druga, J. Tintěra., and Obsahuje bibliografii