[Effect of dosed diet restriction on physiological remodeling and bioelectric properties of bone].

The effect of dosed diet restriction on the physiological remodeling and bioelectric properties of bone tissue was studied in 48 male Wistar rats 3- and 18-months of age. The rate of bone tissue apposition was studied by the dynamic histomorphometry method (intravital tetracycline labeling). Electric potentials on the periosteal surface of the freshly isolated femurs were recorded. The magnitude of dielectric loss factor was determined to assess the quality of bone tissue. The control rats received a standard diet. The experimental rats received a limited diet (60 % of the standard mass) for 28 days. The magnitude and rate of the bone tissue apposition on the endosteal and periosteal surface of the tibia were less by 38.4% and 122.7% respectively in experimental rats after dosed diet restriction. Electric potential in the metaphyseal-epiphyseal growth zones of the femur was 29.7% lower, and the dielectric loss factor increased by 15.8%. The bone tissue apposition rate and the electric potential magnitude were increased 10 days after completion of the dosed diet restriction. The magnitude of the dielectric loss factor decreased after returning to the standard diet. Key words: dosed diet restriction, bone, remodelling, bioelectric properties.

[Effects of hypokinesia and hypoxia on the bone static electrogenesis].

It was studied the conformities to law of quasistatic electric potential (QSEP) distribution on the periosteal surface of 64 adult Vistar rats-males fresh exited femur and their changes after dosed hypokinesia and hypoxia influences. The maximal negative sizes of QSEP were incorporated in epiphyseal-metaphyseal departments and minimal--in the central part of bone diaphysis. Conformities to law of QSEP distribution on the periosteal surface fresh exited bone represented the physiology unevenness of metabolic processes intensity in the different bone departments. Reparative regeneration was accompanied with strengthening of electro-negativity of reparations and adjacent parts and changing of physiology character of QSEP distribution on the periosteal surface of the damaged bone. Hypokinesia disturbed of bone static electrogenesis. It was accompanied with diminishing of QSEP size especially in bone parts which had hight level of metabolism. Dosed an intermittent normobarical and hypobarical hypoxia activated of bone static electrogenesis. More considerably increasing of QSEP in old rats was obtained after the intermittent hypobarical hypoxia influences.

[The stress generated potential in the femur during different modes of mechanical loading in rats].

It was studied the stress generated potential (SGP) of moist femur bones of 24 Vistar rats-males in normo- and hypokinesia conditions. The mechanical loading on bone was evened 30-50 and 100% from animal body mass. The mechanical pressure was carried out in axial direction. The rats stay in hard hypokinesia for 28 days. In all experiments Ag-AgCl with a salt bridge from 0,9% NaCl in 2% agar were utilized (Cochran G.V. et al., 1989). It was set that amplitude of electric potential which arises up in bones at the mechanical loading depends on the level of this loading. However there is a certain optimum of the mechanical loading which provides the maximal increase of SGP. This optimum is in the range of physiology level of loadings. At development of hypokinetic osteopenia SGP diminished most substantially in the range ofphysiology level loadings also. It may be one of reasons of low efficiency of the physical loadings at development age-old osteopenia and slow renewal of bone tissue after hypokinesia.

[Impedance testing of compact bone tissue in hypokinetic rats].

The bioelectrical impedance method was used for determination of compact bone status in white rats after 28th days of strong hypokinesia. It was shown that the lowering of mechanical loading leads to disturbances in dielectric properties and changes in electrical impedance parameters. These disturbances had different direction and manifestation. It was distinguished the two typical variants of bone dielectric properties changes. The first variant was more characteristic for early stages of hypokinetic osteodestruction, the second variant was more characteristic for the fully development hypokinetic disturbances. It was determine a correlation between the changes in electrical impedance parameters and mane components of bone matrix. The results of this study show that hyperhydratation of bone tissue play important role in hypokinetic changes of bone dielectric properties. Electroimpedance method may be used for early diagnostic of bone state in clinic and experiments.

[The model of hypokinesia in rats and preventing its negative effects].

The special container for modeling of long-term hypokinesia state in rats was developed. Such construction allows us to examine simultaneously hypokinesia and its negative influence correction by gas mixture regulated with different oxygen partial pressure.

[The modeling of experimental osteopenia in rats and development of prophylaxis technology]. / Modeliuvannia eksperymental'noï osteopeniï ta rozrobka tekhnolohiï ïï profilaktyky u shchuriv.

An appliance for hind limb unloading in rats and the technology for preventing of inactivity osteopenia have been developed.