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Biomedical subjects

V K Popov

Publications and source records attributed to V K Popov.

At least 19 recordsLinked to original sources
PubMed2004

Evolution of the regulation of the environmental radiation protection and monitoring in the Russian Federation.

The evolution of the Russian Federation legislation and regulation concerning the radiation protection of the population, the environment and the monitoring is presented. The main federal laws--"On the Environmental Protection", "On the Atomic Energy Use", "On the Radiation Safety of Population", etc. as well as standards of radiation safety, sanitary and hygienic norms, international agreements and conventions are briefly summarized. Main directions towards further improvement of the environmental radioprotection regulation in Russia are pointed out.

Environment↗
PubMed2004

Laser stereolithography and supercritical fluid processing for custom-designed implant fabrication.

This paper describes the laser photopolymerization of a liquid mixture of polyfunctional acrylic monomers, photoinitiator and hydroxyapatite (HA). Pure polymeric and composite materials of specific shape and structure were fabricated by laser stereolithography based on images derived from three-dimensional (3D) computer modeling. The polymeric objects then were treated with supercritical carbon dioxide to remove potentially toxic residues (monomers, low molecular weight oligomers, etc.) and to provide interconnective microporosity. Finally, samples were implanted into white rats (diastolic epiphysis of femoral bone) to study living tissue response and processes of osteointegration and osteoinduction. It was shown that incorporation of HA into the composite implant structure encouraged periosteal as well as endosteal osteogenesis and improved their osteointegrative characteristics in particular. Supercritical carbon dioxide treatment significantly enhanced the biocompatibility of the materials, increasing the area of direct contact of the implant surface with regenerated bone tissue.

Animals↗
PubMed2003

Properties of calcium phosphate coatings deposited and modified with lasers.

Physical, chemical and biological properties of calcium phosphate coatings fabricated by a pulse laser deposition method at room temperature (RT PLD) have been studied. In vitro evaluation of RT PLD coatings on bioresorbable polymers (Poly-epsilon-caprolactone and Poly-L-lactide) have been carried out. It was shown that both polymers support osteoblast growth, with increased cell activity, alkaline phosphatase activity and total protein content on those surfaces that have been coated. The advantages of RT PLD coatings in biomaterials surface optimization are discussed.

Journal Article↗
PubMed2001

Osteoblast growth on titanium foils coated with hydroxyapatite by pulsed laser ablation.

Pulsed laser ablation is a new method for deposition of thin layers of hydroxyapatite (HA) on to biomaterial surfaces. In this paper, we report activity and morphology of osteoblasts grown on HA surfaces fabricated using different laser conditions. Two sets of films were deposited from dense HA targets, at three different laser fluences: 3, 6 and 9 Jcm(-2). One set of the surfaces was annealed at 575 degrees C to increase the crystallinity of the deposited films. Primary human osteoblasts were seeded onto the material surfaces and cytoskeletal actin organisation was examined using confocal laser scanning microscopy. The annealed surfaces supported greater cell attachment and more defined cytoskeletal actin organisation. Cell activity, measured using the alamar Blue assay, was also found to be significantly higher on the annealed samples. In addition, our results show distinct trends that correlate with the laser fluence used for deposition. The cell activity increases with increasing fluence. This pattern was repeated for alkaline phosphatase production by the cells. Differences in cell spreading were apparent which were correlated with the fluence used to deposit the HA. The optimum surface for initial attachment and spreading of osteoblasts was one of the HA films deposited using 9 J cm(-2) laser fluence and subsequently annealed at 575 degrees C.

Alkaline Phosphatase↗
PubMed2000

Physical, chemical, and biological characterization of pulsed laser deposited and plasma sputtered hydroxyapatite thin films on titanium alloy.

The physical, chemical, and biological properties of pulsed laser deposited (PLD) and plasma sputtered (PS) hydroxyapatite (HA) coatings were compared. Human osteoblast-like cell responses to these coatings in vitro were assayed for proliferation and phenotypic expression. PS coatings formed smooth and continuous thin films that followed the contours of the substrate surface. PLD coatings consisted of numerous spheroidal micro- and macroparticles. The crystallinity of all coatings was quantified by comparison with the HA target used for both the PS and PLD processes. The XRD and FTIR results indicated that unannealed PLD coatings deposited at room temperature had X-ray spectra consistent with an amorphous structure and were found to dissolve after only a few hours in saline solution. Annealing at 400 degrees C increased the crystallinity (87-98%), which resulted in improved stability and cell activity. The PS coatings showed greater chemical stability than the unannealed PLD coatings and contained an approximate 15% crystalline phase, increasing to 65% postannealing. Cell proliferation and alkaline phosphatase production were significantly higher on unannealed PS specimens than the other coating treatments. There may be benefits in engineering the presence of a minor percentage of a microcrystalline phase in an amorphous or nanometer scale polycrystalline HA structure.

Alloys↗
PubMed1999

Daily copper supplement effects on copper balance in trained subjects during prolonged restriction of muscular activity.

The aim of this study was to assess the effect of a daily intake of copper supplements on negative copper balance during prolonged exposure to hypokinesia (decreased number of kilometers per day). During hypokinesia (HK), negative copper balance is shown by increased, not by decreased, serum copper concentration, as it happens in other situations. Studies were done during a 30-d prehypokinetic period and a 364-d hypokinetic period. Forty male trained volunteers aged 22-26 yr with a peak oxygen uptake of 66.4 mL/min/kg and with an average of 13.7 km/d running distance were chosen as subjects. They were equally divided into four groups: unsupplemented ambulatory control subjects (UACS), unsupplemented hypokinetic subjects (UHKS), supplemented hypokinetic subjects (SHKS), and supplemented ambulatory control subjects (SACS). The SACS and SHKS groups took 0.09 mg copper carbonate/kg body weight daily. The SHKS and UHKS groups were maintained under an average running distance of 1.7 km/d, whereas the SACS and UACS groups did not experience any modifications in their normal training routines. During the 30-d prehypokinetic period and the 346-d hypokinetic period, urinary excretion of copper, calcium, and magnesium and serum concentrations of copper, calcium, and magnesium were measured. Copper loss in feces and copper balance was also determined. In both UHKS and SHKS groups, urinary excretion of copper, calcium, and magnesium and concentrations of copper, magnesium, and calcium in serum increased significantly when compared with the SACS and UACS groups. Loss of copper in feces was also increased significantly in the SHKS and UHKS groups when compared with the UACS and SACS groups. Throughout the study, the copper balance was negative in the SHKS and UHKS groups, whereas in the SACS and UACS groups, the copper balance was positive. It was concluded that a daily intake of copper supplements cannot be used to prevent copper deficiency shown by increased copper concentration. Copper supplements also failed to prevent negative copper balance and copper losses in feces and urine in endurance-trained subjects during prolonged exposure to HK.

Adult↗
PubMed1998

Changes in thyroid hormones and lipids in endurance trained volunteers during acute and rigorous bed rest conditions.

The aim of this study was to evaluate the effect of an acute rigorous bed rest (ABR) (abrupt confinement to a rigorous bed rest regimen) and a rigorous bed rest (RBR) regimen on serum concentrations of thyroid hormones and lipids. The studies were done during seven days of a pre bed rest period and during seven days of an ABR and RBR period. Thirty endurance trained male volunteers aged 22 to 26 years with a peak oxygen uptake of 66.0 mL.min-1.kg-1 and running an average of 14.0 km.day-1 were chosen as subjects. They were divided equally into three groups: (one) ten athletes placed under ambulatory conditions served as ambulatory control subjects (ACS), (two) ten athletes subjected to an acute rigorous bed rest regimen served as acute bed rested subjects (ABRS) and (three) ten athletes submitted to a rigorous bed rest regimen served as rigorous bed rested subjects (RBRS). For the simulation of the effect of ABR the ABRS group was submitted abruptly to a rigorous bed rest regimen. They did not have any prior knowledge of the exact date and time when they would be asked to submit to the RBR. For the simulation of the effect of RBR the RBRS group was subjected to a rigorous bed rest regimen on a predetermined date and time known to them right from the start of the study. During the pre bed rest period and during the ABR and RBR periods serum concentrations of thyroxine (T3), triiodothyronine (T4), thyroid-stimulating hormone (TSH), cholesterol, triglycerides, total protein and albumin were measured. In the ABRS and RBRS groups serum concentrations of T3, T4, TSH, cholesterol, triglycerides, total protein and albumin increased significantly when compared with the ACS group. Serum concentrations of thyroid hormones and lipids in the ABRS group increased much faster and were more pronounced than in the RBRS group. It is concluded that exposure to RBR and, especially, to ABR conditions induces significant increases in serum concentrations of thyroid hormones and lipids. These changes occurred much earlier and were much greater in the ABRS group than in the RBRS group.

Adult↗
PubMed1998

Morphometric examination of glomerulus and juxta glomerural system of rat kidney during prolonged restriction of motor activity.

The aim of this study was to examine the structural changes of glomerular and juxta glomerular system (JGS) of the kidney of rats during prolonged restriction of motor activity (hypokinesia). The studies were performed during 90 days of hypokinesia (HK) on 144 male Wistar rats divided into two groups: Group one placed under ordinary vivarium conditions and serving as vivarium control rats (VCR) and Group two subjected to HK and serving as hypokinetic rats (HKR). For the simulation of the hypokinetic effect the HKR group was kept in small individual cages made of wood that restricted the movements of rats in all directions without hindering food and water intake. During a prehypokinetic period of 15 days and the hypokinetic period of 90 days, body weight and food intake were measured and morphometric examinations were done to measure the cortical and juxta medullary glomerulus on kidney sections from the VCR and HKR groups (eight rats from each group). Body weight and food intake decreased significantly in the HKR groups when compared with the VCR group. Kidney weight of rats increased, the superficial volume decreased and that of the juxta medullary glomerules increased, whereas juxta glomerular granularity indexes decreased significantly in the HKR group when compared with the VCR group. The measured parameters did not change significantly in the VCR group when compared with the baseline control values. It was concluded that prolonged exposure to HK induces a significant increase in the kidney weight and a relationship appeared between variations of the volume of cortical and juxta medullary glomerulus and the function of the juxtaglomerular apparatus.

Algorithms↗
PubMed1998

[The tissue reaction to acrylic plastics modified by supercritical extraction with carbon dioxide].

The process of extraction of admixtures from acryl plastic widely used in dentistry by means of supercritical carbon dioxide (sc-CO2) was studied and effects of extraction conditions on biocompatibility and toxicity of resultant materials assessed, sc-CO2 effectively purified the specimens from toxic compounds (monomers and low-molecular oligomers, methylmethacrylate, dichloroethane) and notably improved the biocompatability of polymer implants. Tissue reaction to ethacryl and protacryl depends on the degree of implant polymerization and duration of extraction of toxic substances from polymer.

Acrylic Resins↗
PubMed1997

Thermal and diffusion processes in laser-induced stress relaxation and reshaping of cartilage.

The thermodynamic characteristics of the 'bound-to-free' phase transformation of water are studied by means of differential microcalorimetry and FTIR spectroscopy. This phase transition controls the stress relaxation and reshaping of cartilage which we have observed previously under moderate laser heating. It is shown that the FTIR spectrum of bound water in cartilage differs from that of free water in cartilage, and that both show differences to the FTIR spectrum of pure water. The proportion of bound water in cartilage is found to be of the order 4%. We have examined water liberation and absorption kinetics and found them to be controlled by diffusion through the tissue and also by the bound-to-free water transformation. The theoretical modelling and experimental data allowed calculation of diffusion coefficients and the activation energy for water transfer. The latter was found to be close to the heat of phase transformation of water. We have established that the drying and wetting processes in cartilage are reversible (fully or in a part, depending on the temperature of preliminary drying) and can be described by identical solutions of the diffusion problem, with coefficients of water diffusion being the same. The mechanism of water diffusion in cartilaginous tissue is also discussed.

Animals↗
PubMed1997

Atomic force microscopic study of the surface morphology of apatite films deposited by pulsed laser ablation.

Atomic force microscopy (AFM) has been used to study the surface morphology of apatite films deposited on metallic and polyethylene substrates by laser ablation using KrF and transversely excited atmospheric CO2 lasers. The films are found to consist of a smooth apatite coating with macroparticles scattered on the surface. A wide variety of macroparticles, differing in size, shape and roughness, were found and analysed employing the high spatial resolution of AFM (< 1 nm). We have investigated the correlation between the apatite film morphology and the deposition conditions. Of particular importance are laser fluence, gas pressure, the nature of the target and the substrate temperature. We have explained these dependencies on the basis of a theoretical model which includes evaporation and a cluster-type laser ablation mechanism.

Apatites↗
PubMed1997

[Enhancing the biocompatibility of dentures made from polymethylmethacrylate by using hydroxyapatite].

Twenty or 50 weight-percent of hydroxyapatite (Polystome) was added in suspensions of AKR-15 copolymer and acid monomers, then the mixtures were molded and subjected to thermal treatment. Admixtures (supercritical CO2) were extracted from the composites in parallel with infrared spectroscopic measurement of the concentration of methylmetacrylate toxic monomers. Hydroxyapatite in 20% concentration decreased the release of toxic substances from the composite, whereas 50% concentration of the agent did not produce this effect. Three patients with intolerance of acrylic plastic were effectively treated using this method.

Biocompatible Materials↗
PubMed1996

[Biocompatible coatings for metallic implants obtained by laser spraying].

Use of various lasers and regimens for spraying the coatings and for additional thermal processing makes it possible to purposefully alter the morphology, composition, and crystallinity of the coatings, and hence, the optimal coatings, as regards their biological activity, may be created. Replacement of eximer lasers with CO2 lasers makes the spraying process cheaper and comparable in efficacy with the plasma process, with the quality of coatings and reproducibility of their parameters appreciably improved. Experiments with coatings of three types, sprayed by CO2 lasers, demonstrated that they met the mechanical and physico-chemical requirements of biocompatibility.

Biocompatible Materials↗
PubMed1996

[The structural characteristics of the bony tissue at the surface of an implant with hydroxyapatite spray-coated with excimer and CO2 lasers].

Rat experiments were performed to study osteogenesis and osseointegration in implanting fragments of dental titanic implants into the spongy bone. The implant spray-coating with hydroxyapatite produced by excimer and CO2 lasers stimulates osteogenesis. Bone tissue integration with implant proceeds more actively in response to CO2 laser radiation. The weakest integration was registered between the metal and bone tissues.

Animals↗
PubMed1989

[Relation of optokinetic nystagmus and the width of the visual field].

Optokinetic nystagmus (OKN) was elicited in humans by a moving vertical grating wide 30-170 degrees. A large range of velocities (10-120 degrees/sec) and a constant spatial stimulus frequency (0.13 cycle/degree) were used. It has been shown that the qualitative and quantitative OKN parameters can be controlled by stimulus area width. The optimal OKN was found under conditions of the whole field stimulation. Progressive masking of the periphery caused a OKN reduction whose magnitude was fixed in different stimulus ranges. The elimination of central stimulation resulted in a complete OKN suppression. The role of the stimulation eccentricity and of the stationary edges in the observed OKN changes is discussed. The findings offer a possibility for a more precise evaluation of OK responses.

Adult↗
PubMedDate not supplied

[Bone marrow hematopoiesis in polymer composite implants in long-term bone marrow cultures].

The morphological composition of cells on implants made of different composition materials was studied on the model of long-term bone marrow cultures at cultivation for 28 days. Three samples of materials were investigated: polymethyl methacrylate (PMMC), PMMC with hydroxyapatite (HA) and PMMC with HA and subsequent processing with supercritical carbon dioxide. A gradual rise in total number of cells was observed on the implants for 4 weeks as well as increasing number of stromal and hemopoietic cells. With increasing time of cultivation the share of stromal cells was growing while the percent of hemopoietic cells fell. The greater number of hemopoietic cells was observed on the samples of the implants made from composites containing HA vs implants made from the initial PMMC.

Animals↗
PubMedDate not supplied

[Parity principle and kinematic asymmetries in the otolith system].

Using a mathematical model, otolith stimulation in response to man's movements in a system rotating with a constant angular velocity was examined. Man moved his head or body forward or sideward obeying the trapezoidal rule. The resulting accelerations that acted upon the left and right otoliths were determined. The existence of two otoliths that are symmetrical relative to the sagittal plane was found to be responsible for the left-right asymmetry that accompanied movements in the rotating system, the asymmetry being most distinct during tilts to the left or to the right.

Acceleration↗