The influence of long-term hypodynamy on the calcium and phosphorus levels was studied in the bones of Japanese quails. The hypodynamy evoked different changes in the calcium and phosphorus content in males and females. The calcium content in the marrow of femurs was only changed in the hens, while in cockerels it was significantly decreased in the upper part and marrow of the tibia. Furthermore, changes in the phosphorus content were observed only in the tibia of cockerels., J. Antalíková, M. Baranovská, I. Mravcová, V. Sabo, P. Škrobánek., and Obsahuje bibliografii
Here we analyzed associations between muscles mass, total bone mineral content (BMC), lumbar spine bone density (BMD L1-L4) and serum or urine hormones in healthy peripubertal girls. Total BMC and areal BMD L1-L4, muscle mass and fat were measured by dual-energy X-ray absorptiometry (DXA). Muscle force (N) was estimated by a dynamometer. Circulating estradiol, folliclestimulating hormone (FSH), luteinizing hormone (LH), 25-hydroxy vitamin D, parathyroid hormone (PTH), insulin-like growth factor 1 (IGF-1), leptin, osteocalcin, bone isoenzyme of alkaline phosphatase (bALP) and total calcium and phosphorus were quantified as the nocturnal melatonin and serotonin urinary excretion. Partial correlations adjusted for height, Tanner score and physical activity confirmed positive relationships between BMC or BMD L1-L4 (Z-score) and lean mass or fat. Furthermore, positive relationship was observed between BMC or BMD L1-L4 (Z-score) and serum leptin. After adjustment for Tanner score and physical activity, positive associations were observed between lean mass and IGF-1, leptin levels or muscle force. We proved positive relationships between bone mass and serum leptin in peripubertal girls., V. Cirmanova, I. Zofkova, P. Kasalicky, V. Lanska, M. Bayer, L. Starka, R. Kanceva., and Obsahuje bibliografii
Osteoporotic fractures are the result of low density and especially inferior bone quality (microarchitecture) caused by both internal (genes, hormones) and external (life style) influences. Bone mechanosensors are extremely important for the overall integrity of the skeleton, because in response to mechanical load they activate its modeling, resulting in an increase in bone density and strength. The largest physiological loads are caused by muscle contractions. Bone mass in adult men has a closer relationship to muscle mass than is case in women. The sexual differences in the relationship between bone and muscle mass are also apparent in children. Based on the mechanostatic theory, the muscle-bone unit has been defined as a functional system whose components are under the common control of the hormones of the somatotropin-IGF-I axis, sexual steroids, certain adipose tissue hormones and vitamin D. The osteogenic effects of somatotropin-IGF-I system are based on the stimulation of bone formation, as well as increase in muscle mass. Moreover, somatotropin decreases the bone mechanostat threshold and reinforces the effect of physical stress on bone formation. The system, via the muscle-bone unit, plays a significant role in the development of the childhood skeleton as well as in its stability during adulthood. The muscle and bone are also the targets of androgens, which increase bone formation and the growth of muscle mass in men and women, independently of IGF-I. The role of further above-mentioned hormones in regulation of this unified functional complex is also discussed., I. Žofková., and Obsahuje bibliografii a bibliografické odkazy
Our study aimed to investigate subacute exposure to alcohol in relation to bone microstructure of mice. Animals from experimental (E) group drank a solution composed of 15 % ethanol and water for 14 days (one remodeling cycle), while those from control (C) group drank only water. In the compact bone of E group, decreased bone formation and increased porosity were observed which corresponds with lower levels of serum alkaline phosphatase and glutathione. Alcohol significantly increased sizes of primary osteon's vascular canals and decreased those of secondary osteons, Haversian canals. Relative bone volume, bone mineral density (BMD), relative bone volume without marrow cavity were also lower in E group. On the contrary, trabecular bone microstructure did not differ significantly between E and C groups. Liver function test showed higher levels of alanine aminotransferase, aspartate aminotransferase in alcohol-fed mice. Serum calcium, phosphate were significantly lower in E group. According to our study, only changes in compact bone microstructure of mice following one remodeling cycle were observed due to both direct and indirect effects of alcohol., A. Sarocka, V. Kovacova, R. Omelka, M. Bauerova, E. Kapusta, Z. Goc, G. Formicki, M. Martiniakova., and Obsahuje bibliografii
Leptin, a cytokine-like hormone secreted by adipocytes, is known to regulate food intake but has also emerged as a significant factor in the regulation of bone mass. In humans, states of energy deprivation with low serum leptin have been associated with low bone mass. In mice, leptin deficiency led to increased trabecular bone mass with overall decrease in cortical bone. Leptin regulates bone metabolism indirectly in the hypothalamus thereby activating the sympathetic nervous system (SNS). In addition to the SNS, leptin also interacts with various hypothalamic neuropeptides, such as cocaine- and amphetamine-regulated transcript, neuropeptide Y and/or neuromedin U, which might modulate the effects of leptin on bone. In osteoblasts sympathetic signaling is further gated by the transcriptional factors called molecular clock. As a result, bone loss is accelerated showing that the central effect of leptin seems to be antiosteogenic. Additionally, leptin has a direct anabolic effect within the bone driving the differentiation of bone marrow stem cells into the osteoblastic cell lineage. Besides the interaction between the central and peripheral pathways, the overall effect of leptin on bone might be bimodal depending on leptin serum concentrations. Regulatory pathways triggering osteoblast activity might open new possibilities for anabolic treatment of osteoporosis., V. Cirmanová, M. Bayer, L. Stárka, K. Zajíčková., and Obsahuje bibliografii a bibliografické odkazy
Mechanical behavior of biological structures under dynamic loading generally depends on elastic as well as viscous properties of biological materials. The significance of “viscous” parameters in real situations remains to be elucidated. Behavior of rheological models consisting of a combination of inertial body and two Voigt’s bodies were described mathematically with respect to inverse problem solution, and behavior in impulse and harmonic loadings was analyzed. Samples of walls of porcine and human aorta thoracica in transverse direction and samples of human bone (caput femoris, substantia compacta) were measured. Deformation responses of human skin in vivo were also measured. Values of elastic moduli of porcine aorta walls were in the interval from 102 kPa to 103 kPa, values of viscous coefficients were in the interval from 102 Pa.s to 103 Pa.s. The value of shear stress moduli of human caput femoris, substantia compacta range from 52.7 to 161.1 MPa, and viscous coefficients were in the interval from 27.3 to 98.9 kPa.s. The role of viscous coefficients is significant for relatively high loading frequencies - in our materials above 8 Hz in aorta walls and 5 Hz for bones. In bones, the viscosity reduced maximum deformation corresponding to short rectangular stress., M. Kuchařová, S. Ďoubal, P. Klemera, P. Rejchrt, M. Navrátil., and Obsahuje bibliografii