Local electronic structure and nanolevel hierarchical organization of bone tissue: theory and NEXAFS study.

Theoretical and experimental investigations of native bone are carried out to understand relationships between its hierarchical organization and local electronic and atomic structure of the mineralized phase. The 3D superlattice model of a coplanar assembly of the hydroxyapatite (HAP) nanocrystallites separated by the hydrated nanolayers is introduced to account the interplay of short-, long- and super-range order parameters in bone tissue. The model is applied to (i) predict and rationalize the HAP-to-bone spectral changes in the electronic structure and (ii) describe the mechanisms ensuring the link of the hierarchical organization with the electronic structure of the mineralized phase in bone. To check the predictions the near-edge x-ray absorption fine structure (NEXAFS) at the Ca 2p, P 2p and O 1s thresholds is measured for native bone and compared with NEXAFS for reference compounds. The NEXAFS analysis has demonstrated the essential hierarchy induced HAP-to-bone red shifts of the Ca and P 2p-to-valence transitions. The lowest O 1s excitation line at 532.2 eV in bone is assigned with superposition of core transitions in the hydroxide OH-(H2O) m anions, Ca2+(H2O) n cations, the carboxyl groups inside the collagen and [PO4]2- and [PO4]- anions with unsaturated P-O bonds.

[CHARACTERISTICS OF OSTEOCYTE CELL LINES FROM BONES FORMED AS A RESULT OF MEMBRANOUS (SKULL BONES) AND CHONDRAL (LONG BONES) OSSIFICATION].

The aim of this work was to analyze the literature data and the results of authors' own research, to answer the question--if the osteocytes of bone tissues resulting from membranous and chondral ossification, belong to one or to different cell lines. The differences between the cells of osteocyte lines derived from bones resulting from membranous and chondral ossification were established in: 1) the magnitude of the mechanical signal, initiating the development of the process of mechanotransduction; 2) the nature of the relationship between the magnitude of the mechanical signal that initiates the reorganization of the architecture of bone structures and the resource of their strength; in membranous bones significantly lower mechanical signal caused a substantially greater increment of bone strength resource; 3) the biological activity of bone structures, bone fragments formed from membranous tissue were more optimal for transplantation; 4) the characteristics of expression of functional markers of bone cells at different stages of their differentiation; 5) the nature of the reaction of bone cells to mechanical stress; 6) the sensitivity of bone cells to one of the factors controlling the process of mechanotransduction (PGI2); 7) the functioning of osteocytes during lactation. These differences reflect the functional requirements to the bones of the skeleton--the supporting function in the bones of the limbs and the shaping and protection in the bones of the cranial vault. These data suggest that the results of research conducted on the bones of the skull, should not be transferred to the entire skeleton as a whole.

[Hierarchically organized model of interconnected cellular and tissue mechanisms of calcium exchange between bone and blood].

The objective of this study was to propose, on the basis of the results of authors' own research and literature data, the hierarchically organized model of the interrelation of morphological mechanisms with the participation of biochemical bases of Ca2+ exchange between bone and blood. It is shown that osteocytes control the activity of main known mechanism of skeleton architecture remodeling (osteoclast-osteoblast remodeling, modeling, osteocyte remodeling etc.), that is the destruction and formation of mineral matrix component, thus influencing calcium turnover between bone and blood. The hierarchical organization of the mechanisms of this exchange is established. The first level of Ca2+ metabolism corresponds to the borderline between bone and takes place without bone matrix disintegration by paracellular energy-free Ca2+ diffusion from blood to bone and transcellular energy-dependent Ca2+ transfer from bone to blood. At the second level, calcium exchanger takes place at the borderline between between bone matrix and extracellular fluid by osteocyte remodeling during resorption or formation of the matrix of lacunar-canalicular system walls. The third level includes the mechanisms of osteoclast-osteoblast remodeling acting at the borderline between bone and blood. The mass of rapidly exchanging calcium pool was calculated to reach 58,5 g, thus being 11 times higher than previously suggected.

[Precision error minimization algorithm for dual-energy X-ray absorptiometry to clinically insignificant values].

OBJECTIVE: To propose an algorithm for using dual-energy X-ray absorptiometry (DEXA) on the basis of the authors' findings and the data available in the literature on the estimation of the projectional bone mineral density (PBMD), which can minimize the precision error (PE) to clinically insignificant values while solving the problems of diagnosis, prognosis, and therapeutic effectiveness monitoring in a specific patient. MATERIAL AND METHODS: The results of the authors' ex vivo studies and literature data on PE during DEXA in a densitometry room were systematized. RESULTS: The performed analysis allowed the elaboration of a PE minimizing algorithm in the individual control in terms of clinical problems to be solved. The elements of a working place passport system, which allow the head of a radiological service to control the work of a densitometry room and a densitometer operator to make self-control, have been developed. CONCLUSION: The elaborated algorithm for using DEXA in a densitometry room to estimate PBMD permits one to minimize PE when solving the problems of diagnosis, prognosis, and therapeutic effectiveness monitoring in a specific patient in the clinically permissible limits.

[Osteocytes and the pathways of mechanical homeostasis optimization from the point of view of functional osteology].

The aim of this work was to determine, on the basis of the results of authors' own research and literature data, the main pathways of osteocyte (OC) influence on the mechanical homeostasis of the skeleton. The following pathways of reorganization of the architecture of bone structures are postulated: at the ultrastructural level without direct cell participation, through the bone matrix synthesis by osteoblasts and OC, through bone matrix resorption by osteoclasts and OC, the latter being able to resorb the surrounding mineral and organic matrix both separately, and conjointly. This reorganization results in local changes of the mechanical characteristics of bones due to changes in: porosity of interstitial spaces, transport ability of the lacunar-canalicular system, porosity of the area of osteoblastic-osteoclastic remodeling, modeling of bone structures. From the point of view of adaptation theory it is highly significant that the subtle local control of bone structures is able to induce changes in the parameters of the mechanical environment, which, on the one hand, would correspond to OC metabolic requirements and, on the other hand, would support the parameters of body mineral homeostasis.

[Osteocytic bone remodeling: history of the problem, morphological markers].

On the basis of the authors' own results and the analysis of the literature, the morphological markers of resorptive and synthetic phases of osteocytic bone remodeling under physiological conditions, are discussed. Their application by different authors is considered taking into account the history of the research of the osteocyte role in bone matrix metabolism (synthesis and resorption). Currently, there arose an urgent need for the quantitative assessment of osteocyte remodeling by combining routine histological methods of the osseous tissue study with the possibilities of modern image analysis systems.

[Hierarchy of spiral organization of skeletal structures. Interrelationship between structure and functions].

The objective of this review is to discuss the interrelationship between hierarchy of spiral organization of the structural elements of the skeleton and its mechanical characteristics with regard to functional-biological expediency. The following hierarchic levels of spiral organization of skeletal structures are defined: collagen chains, collagen molecules, microfibrils, fibrils, collagen fibers, osteon network and organization of osseous macrostructure responsible for torsion effect in weight bearing. This spiral organization creates the conditions, under which the directions of domineering forces in the bone usually do not coincide with the direction of the longitudinal crystallite axes. It causes shifting deformity between the adjacent crystallites. which should be taken into account alongside with distraction-compression deformity. These features form the basis of nano-level mechanism responsible for mechanical characteristics of bone tissue.

[Dynamic assessment of bone tissue osteocytic remodeling using a noninvasive method].

Projectional bone mineral density (PBMD) in the proximal region of both femoral bones, the distal part of the forearm bones on both sides and in the lumbar vertebrae was studied with the method of dual energy roentgen absorption (DEXA) in two male volunteers at the age of 40 and 60 years on a daily basis during one month. On the basis of the results of the estimation of each area of interest (AI) M(av), oscillation range (4(sigma)) and the greatest difference were calculated. In addition to it, a statistic mathematic modeling was conducted through smoothing out the dynamic rows of the results achieved for each AI. It was found out that the average oscillation range exceeded 9% of the average index value, which is thrice as much as the method reproducibility error. This kind of investigation in the process of treatment allows monitoring its efficiency taking into consideration both mechanisms (osteoblastic-osteoclastic remodeling and osteocytic remodeling) as well as estimating the toxic effects of medical agents on bone cells. As a result of statistic mathematic modeling, cercaseptane periodicity of PBMD changes with the average period of 5.5 days was found. The authors see the cause of these short-term changes in osteocytic remodeling and suggest to use a dynamic successive PBMD measurements during 7-10 days as a way of non-invasive monitoring of osteocyte resorption-synthetic activity in AI.

[Interconnection of morpho-functional changes at various levels of the cortical bone hierarchic organization in aging].

The authors define two groups of levels of cortical bone hierarchic organization. The first three levels (molecular, supra-molecular and tissue) are characterized by age-dependent changes in connections and geometry of collagen fibers, deviations in orientation and interaction between collagen and minerals, increase in crystallinity and size of the latter, resulting in matrix hypermineralization. It causes water and organic fraction displacement, as well as intermolecular space reduction, which provides for lesser amount of matrix deformations under the influence of mechanical forces. At the next three levels (structural-functional, organ-forming structures, organ) adaptation processes contribute to deformation increase due to a greater volume of cavities (Haversian canals and medullar cavity of the diaphysis of long tubular bones). These are due to the fact that osseous tissue cells possess superior and inferior thresholds of deformation perception, and through modeling/remodeling provide for extracellular matrix migration in the direction limited by these thresholds. Bone geometry changes leading to bone mass loss are also caused by age-dependent rise of the inferior threshold of sensitivity to mechanical impulses and decrease of muscle functional activity. Prevention of the described changes may be possible through elaboration of new, pathogenesis-based ways of drug therapy, including 1) osseous tissue mineralization reduction with the help of osteocyte pump regulators for predominant washing out of Ca2+, 2) lowering the threshold of electric impulses initiation arising in the osteocyte network under mechanical deformations.

[Role of biorhythms in scatter of data of serial red blood cell tests in the preoperative period].

Serial preoperative tests carried out in 826 and 382 patients with primary total and revision hip arthroplasty, respectively, revealed a considerable data scatter in red blood cell values that exceeded instrumental errors. Thirty-day examinations of 7 healthy volunteers indicated the similar data scatter and the change fluctuations in the indices under study. The peripheral blood levels of erythrocytes (Er) and hemoglobin (Hb) fluctuated at hemicircaseptanic intervals and the mean content of hemoglobin (MCH) in the red blood cells did at circaseptanic intervals. There were fluctuations around the trend whose value changed with the circadiseptanic (Er and Hb) and circavigintanic (MCH) periods. It is suggested that these biorhythms are a cause in the observed data scatter.

[Levels of bone mineral matrix organization and the mechanisms determining parameters of its formation].

Authors suggest to regard bone mineral matrix as the four-level structure. The first level is represented by an internal structure of a mineral, the second--by mineral morphological structure, the third--by coplanar association of minerals, and the fourth--by macroassociation of minerals in a single complex inside each bone. The most probable mechanisms determining stability of reproduction of mineral matrix parameters on each of these levels are shown. As a result of their functioning, the variants of bone mineral matrix structures are formed that are the programmed reflection of specificity of the given site of organic structures.

[Aging of the osseous tissue. Theoretical basis for new directions of mechanotransduction optimization].

On the basis on literature studies and the results of personal studies, the authors describe ultra- and micro-structural changes in the osseous tissue associated with the process of aging. Functional disturbances in tissue processes causing osseous tissue loss and osteoporosis development are characterized. It is suggested that the described changes are induced by age-dependent hypermineralization of the osseous tissue with the consequent disturbances of mechano-transduction. A hypothesis is discussed concerning a novel approach to pharmacological treatment of osteoporosis. Development of a new group of drugs controlling the calcium exchange between the osseous compartment and the blood is considered. Presumed pathogenetic and clinical effects of these drugs are described.

[Biorhythmic characteristics of patients with total primary and revision hip replacement].

Age-dependent fluctuations of primary total and revision endoprosthesis have been found which appear to reflect changes in the activity of the inflammation process that can be regarded to be an element of periodic diseases. This seems to depend on the regulatory-metabolic shifts caused by aging.

[The limits of fluctuations of the laboratory findings in the preoperative period during uncomplicated revision endoprosthesing of the hip joint]. / Predely kolebanii laboratornykh pokazatelei v predoperatsionnom periode pri neoslozhnennom revizionnom éndoprotezirovanii tazobedrennogo sustava.

The revision endoprosthesis of the hip joint for aseptic loose components was performed in 482 patients (297 women and 185 men). Before operation the assessment of 44 laboratory indices was made which included clinical blood tests, investigation of the coagulating system, protein and mineral exchange, enzymatic activity and other biochemical criteria. The postoperative course was even, without variations. The work shows the limits of deviations of the parameters with respect to normal condition and gender. The authors believe that they can be considered as a variant of the clinically adequate reaction rather than as a criterion of the unfavorable prognosis of the postoperative course.

[Biorhythmical characterization of exacerbations of the degenerative-dystrophic process in patients with the impaired hip joint]. / Bioritmicheskaia kharakteristika obostrenii degenerativno-distroficheskogo protsessa u patsientov s porazheniem tazobedrennogo sustava.

The age-dependent structure of the contingents treated conservatively at the local outpatient clinics (197 women aged 17-82 and 59 men aged 25-85) and patients subjected to operations of total endoprosthesis of the hip joint for coxarthrosis (663 women aged 19-89 and 304 men aged 22-82) was investigated. The structure of the indices under study was found to fluctuate with the average period length 10.7 years (sigma = 2.7 years), 8.2 years (sigma = 3.5 years), 7.3 days (sigma = 3.0 years), 9.5 years (sigma = 2.1 years) respectively. A comparison of the fluctuation curves of the age-dependent structure of the women treated conservatively and operated upon showed the coincidence of the maximums in 35, 43, 60, 65, 69, 74-74 years of age, in men--in 34-35, 41, 75-76. It can be supposed that the revealed age-dependent fluctuations of activity of the inflammatory process and the pain syndrome correspondingly might be considered as an element of the periodic disease in pathogenesis of degenerative-dystrophic lesions of the hip joint.

[Seasonal fluctuations of intraoperative blood loss in hip joint replacement]. / Sezonnye kolebaniia intraoperatsionnoi krovopoteri pri éndoprotezirovanii tazobedrennogo systava.

Under analysis was the level of intraoperative blood loss in total endopropsthesis of the hip joint in 513 patients operated upon for degenerative-dystrophic processes of consequences of trauma in the period from 1996 to 1999. The assessment of seasonal variations of its value was made. It was shown that the volume of blood loss is dependent on two groups of factors: medical and associated with the influence of the environment. The least "chronorisk" of excessive blood loss was noted in the period from July to November, the greatest--from January to June (with the maximum in March and reduction in May).

[Emergency endoprosthesis of the hip joint. Risk of hospital mortality]. / Ekstrennoe éndoprotezirovanie tazobedrennogo sustava. Risk gospital'noi letal'nosti.

An analysis of case histories of 854 patients operated upon for fractures of the proximal part of the femoral bone at the R.R. Vreden Research Institute of Traumatology and Orthopedics for the period from September 1997 to December 2000 was made in order to assess the intrahospital lethality. The maximum season fluctuations were found to take place in October and March, minimum in September, December and April. The trend was characterized by a gradual rise from September to June. The authors associate these fluctuations with the action of external rhythmically changing factors, the growing trend--with the role of the factor of tiredness of the medical personnel. It was also shown that duration of the time interval from operation to the moment of death as well as the diversity of the value of this index was maximum in December-January and December correspondingly.

[Space-time organization of bone tissue remodeling in vertebral bodies after femur osteotomy]. / Struktura prostranstvenno-vremennoi organizatsii remodelirovaniia kostnoi tkani tel pozvonkov posle osteotomii bedrennoi kosti.

Roentgenometric and roentgenodensitometric chronobiological characteristics of space and time remodeling of the bone tissue in tail vertebra XI and XII after osteotomy of the right femur are described. Examination of 179 white non-inbred male rats revealed circadian periodicity of vertebral bone tissue remodeling. Dynamics of asymmetry of this process also has a circadian periodicity.

[Weak stress factors in the prevention of postoperative complications in elective orthopedic surgery]. / Slabye stressogennye faktory--élement profilaktiki posleoperatsionnykh oslozhnenii pri planovoi ortopedichekoi khirurgii.

Based on their personal and literature data the authors propose to use weak stressogenic factors (pyrogenal and interrupting normobaric hypoxia) as an element of preoperative preparation of patients for prevention of postoperative complications. The using of this method made the frequency of postoperative complications in the area of the operation wound twice as rare, outside the wound--three times as rare.