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Biomedical subjects

A A Doktorov

Publications and source records attributed to A A Doktorov.

At least 19 recordsLinked to original sources
PubMed2005

[Experimental study of osseointegration of zirconium and titanium dental implants].

In an experiment performed on pigs, methods of light and scanning electron microscopy were used to study the interaction of zirconium and titanium dental implants with bone 6 months following their insertion. Distinct features of integration of both implant types with bone structures were detected. Sites of direct contact of bone structures with metal were found to undergo constant remodeling according to biochemical and metabolic conditions in each zone of an implant surface. Statistically the degree of interactive properties of zirconium implants significantly exceeded similar parameter for titanium screws. Along the perimeter of the zones of bone contact with zirconium implants greater numbers of forming and formed bone areas were revealed as compared to the zones of bone contact with titanium implants, where erosion lacunae were more numerous. The complex of research methods used in this study have not revealed distinct changes in the structure of osteocytes, located in immediate proximity to the metal surface in comparison with more distant sites in the bone.

Animals↗
PubMed2004

[Interrelation of matrix vesicles with spatial distribution of mineral component in fibrous and hyaline cartilages].

Mineral components of the human fibrous and hyaline cartilages were studied by the methods of light, scanning, transmission electron microscopy and cryofractography. The interterritorial matrix of the fibrous cartilage was found to contain not only the local deposits of mineral in matrix vesicles, but also the calcified collagen fibrils and interfibrillar spaces forming the collagen fibers and occupying its major part. In the hyaline cartilage and in the territorial matrix of fibrous cartilage, mineral deposits were located in mineralized conglomerates, the basis of which was formed by matrix vesicles, surrounded by collagen fibrils and interfibrillar space substance. Such conglomerates participate in the formation of calcospherites.

Cartilage↗
PubMed2003

Structure of human vertebral lamellar bone in age-associated involution and osteoporosis.

We compared the structure of lamellar bone in anterolateral zones of vertebral bodies in adult and senile subjects in health and osteoporosis. The appearance of structural signs of age-related osteopenia and enlargement of coplanar consolidations of the bone matrix crystals were noted. Osteopenia was more pronounced in osteoporosis, while the structural organization of the mineral component did not differ from that in age-matched controls.

Adolescent↗
PubMed2002

Structural changes in abdominal aorta and vena cava inferior after experimental microwave destruction.

We studied morphological changes in rat abdominal aorta and vena cava inferior induced by endovascular microwave destruction. This treatment induced thrombosis and necrosis of the vascular walls, but fibrous framework was not completely destroyed. Then we observed irreversible changes in vessels: obliteration, atrophy of the aorta walls, and sclerosis of venous walls. The preserved fibrous framework of the vessel walls probably plays a role of a framework for the formation of fibrous tissue.

Animals↗
PubMed2002

[Ultrastructural organization of the human lamellar bone tissue mineral component in aged and elderly].

The lamellar bone mineral component in mature and senile age was studied using the methods of transmission electron microscopy and cryofractography. This component was shown to be formed by crystals (13-4 x 7-8 x 3-4 nm) of the prismatic shape that formed coplanar units (29-3 x 18-21 x 3-4 nm). The peculiarities of mineral particle distribution inside and between the collagen fibrils, as well as on the completely formed areas of bone surface, were detected. It was established that the length and the width of coplanar crystal aggregates was significantly higher in senile age as compared to similar linear parameters defined in persons of mature age (by 17-20 and 5-9%, respectively).

Adult↗
PubMed2002

[Structural organization of compact and cancellous tissue of human rib in aging].

Using the scanning electron microscopy the thickness of external and internal layers of compact bone of the rib as well as the structure of its cancellous bone was investigated in humans aged from 19 to 89 years. The differences of bone remodeling mechanism were found in men and women of the older age groups. In men, the gradual attenuation of osseous structures was taking place. In women, bone loss was found to be rapidly progressing due to the elimination of its structural elements (transformation of compact layer into cancellous bone and disappearance of some part of trabeculae from the latter).

Adult↗
PubMed2001

Morphological changes in the liver after microwave destruction.

We studied morphological changes in the liver after local MW-destruction. Microwave radiation damaged vascular walls with the formation of extensive necrotic focus; demarcation zone appeared 24 h after exposure, encapsulation occurred after 7 days, and replacement with a fine cicatrix formed by mature connective tissue after 4 months.

Animals↗
PubMed2000

[The bone regeneration process under chymotrypsin exposure (an experimental study)].

Disturbance of femur diaphysis compact substance was induced experimentally in rabbits. In the course of the operation single administration of crystalline chimotripsin into the wound was performed and its influence on bony structures regeneration was studied. Methods of light and scanning electron microscopy revealed that reparative processes started earlier and were more active than that in control. This promotes regenerate formation and complete healing of bone defect. Intramuscular administration of proteolytic enzyme does not exert essential influence on bone regeneration.

Animals↗
PubMed1996

[The experimental validation of the potential use of hydroxyapatite-containing preparations for the obturation of the dentin tubules in prepared teeth].

Ultramicroscopic hydroxyapatite (UMHA) was used for obturation of dentine tubules of prepared teeth in dog experiments. Scanning electron microscopy showed that amorphous layer on the tooth surface prevents the penetration of UMHA in the tubules. This layer is not removed by the traditional treatment with alcohol and ether. Exposure of dentin to primer sintac altered the amorphous layer, but did not completely remove it. Solutions consisting of 10% citric acid and 3% iron chloride or 10% EDTA completely removed the amorphous layer in 1 min and permitted hydroxyapatite penetrate in the dentin canaliculi and obturate them. The agent more effectively penetrates in the dentin tubules of vital teeth than of pulp-free ones.

Animals↗
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↗
PubMed1993

[Features of the relief of the mineralized surface of the lacunae and canaliculi in lamellar bone].

By means of cryofractography relief of mineralized surface of lacunae and canaliculi of human lamellar bone has been studied. Their walls consist of mineralized collagen fibrils and mineralized ground substance. The intrafibrillar crystals are rod-shaped and are arranged as elongated helicoidal chains. Mineral crystals localized in the interfibrillar spaces are plate-shaped and are arranged in parallel layers. Net of microcanaliculi with diameter of 20-50 nm is found in bone matrix. This increases the surface available for the exchange between mineral and bone extracellular fluid.

Adult↗
PubMed1993

[Involvement of the anterior longitudinal ligament of the spine in the morphogenesis of osteophytes in spondylosis deformans].

Morphology and relief of the mineralizing front of osteophytes associated with lumbar spondylosis have been studied by means of scanning electron microscopy. During osteophyte formation deep-laid fibers of anterior longitudinal ligament of the spine undergo mineralization followed by their resorption and subsequent replacement by bone structures. Osteophyte surface at its apex consists of mineralized fibers of longitudinal ligament of the spine, formed by mineralized cartilage structures in the area adjacent to the intervertebral disk and by resting bone surface with zone of bone formation and resorption in the area adjacent to longitudinal ligament of the spine.

Aged↗
PubMed1991

[Morpho-functional correlations of the structure of bone cells and adjoining bone matrix in the developing bone].

By means of scanning and transmissive electron microscopy methods structure of the developing bone has been studied. Interconnection of the cell structure and spatial organization of the adjoining matrix has been demonstrated. On the surface of the growing bone not only forming areas have been revealed, where under osteoblasts at various functional states, osteoid layer is determined, but also areas of resorption and completed osteogenesis. This demonstrates an interrupted character of osteogenesis at modelling. At the same time for the remodelling process presence of erosive lacunae is specific; they are filled with a newly deposited collagenous matrix. Therefore, it is possible to suppose that formation of the bone as an organ during the postnatal development includes in itself both mechanisms supporting its form at outgrowth of the osseous matrix volume (modeling) and its continuous rearrangement and adaptation to real conditions of functioning (remodelling).

Animals↗
PubMed1990

[Morphological aspects of the mineral phase of the bone].

By means of light, scanning and transmission electron microscopy structure of the mineral phase of human compact bone have been studied. Mechanical properties of deorganified bone samples have been determined. High compressive strength may be in connection with interactions of plate-like mineral particles at the level of hydrate shell of the bone mineral crystallites.

Adult↗
PubMed1988

[Morphofunctional characteristics of the endosteum].

Basing on the literature data analysis, modern notions concerning endosteum structure, its connections with the bone and bone marrow are presented. Participation of the endosteum in processes of osteogenesis and resorption, as well as its changes with ageing are discussed.

Aging↗
PubMed1987

[Spatial organization of the lacunar-canalicular system in the structures of bone lamellae].

By means of light microscopical techniques and scanning electron microscopy spatial organization of the lacunar-canalicular system (LCS) has been studied in structures of a mature lamellar bone. A method for making corrosive casts of osseous lacunae and canaliculi is suggested, owing to which their spatial organization can be analysed. Certain data on interconnections of the osseous lacunae with each other and with vascular canals and natural surfaces of the bone are presented. The role of LCS as a component of the microcirculatory bed of the lamellar bone is discussed.

Adult↗