Lamellar Bone Tissue Research Articles

Morphofunctional characteristics оs penis of mammals

ABSTRACT The aim of this work was to analyze the issues of the morphofunctional organization of the baculum (os penis) of mammals. In many mammals, to give strength and density to the organ, bone tissue is present in the penis, which forms the bone of the penis (os penis or baculum). This structure is evolutionarily young; it is present only in representatives of the evolutionarily youngest class of vertebrates - the class of mammals. The baculum is present in the penis of both marsupials and representatives of the orders of placental mammals (many rodents, some chiropterans, pinnipeds, cetaceans, some predators, prosimians and some monkeys). Bone tissue is usually located in the anterior region of the penis between the cavernous and spongy bodies. The baculum is an unpaired bone of an elongated shape; it can have the shape of a rod or plate, straight or curved. In cross-section, in representatives of different species, the bone can be round, square, triangular, or flat. Most often, the baculum is a cylindrical rod, expanded at the base and apex; in the proximal and distal parts there are outgrowths of various shapes. The histogenesis of bone tissue during the formation of the os penis in embryogenesis occurs via indirect osteogenesis. At the site of the future os penis, a cartilaginous model is formed from the mesenchyme, in place of which bone tissue then develops. The basis of the baculum is formed by lamellar bone tissue, in which osteons are well expressed. In the superficial zones of the baculum, coarse fibrous (reticulofibrous) bone tissue, as well as fibrous cartilaginous tissue, was identified. The baculum has been found to increase the overall rigidity of the penis when flexing during copulation. It was revealed that larger baculums are present in mammals, which are characterized by a longer duration of copulation.

A MODERN VIEW ON REPARATIVE OSTEOGENESIS: MAIN STAGES AND THEIR PATTERNS

Introduction. Reparative osteogenesis is a staged mechanism that ensures the restoration of damaged bone tissue. The study and summarization of current data about bone defect regeneration is the basis for the search and development of methods to improve this process. The aim of the study is to analyze and systematize the current data about reparative osteogenesis, describe the main stages and their patterns. Materials and methods. Searching the relevant sources using online scientific databases and keywords. Selection of publications for review. Further analysis and synthesis of information. The results. Despite different interpretations of the stages of reparative osteogenesis by researchers, they all describe the same coordinated process. The following key stages have been identified: haematoma formation, inflammation, MSC involvement and angiogenesis, cartilage, connective and bone tissue formation, their subsequent reorganisation, ossification and remodelling. Each of these stages involves specific cellular elements, local and general regulatory factors. The development of osteogenic cells and mechanisms of intercellular interaction, as well as the main signalling pathways and molecules (Wnt, RANK/RANKL/OPG, BMPs, HIF, etc.) that regulate osteo- and angiogenesis are described. The role of hypoxia in the process of bone regeneration and angiogenesis is highlighted. The H-type vessels and their participation in the regulation of osteogenesis are considered. Attention is paid to the phenomenon of ‘chondrocyte transdifferentiation’, which is one of the sources of osteoblasts during endochondral ossification. In the context of remodelling, the law of bone biomechanics and piezoelectric adaptive remodelling, as well as bone multicellular units as microsystems that ensure the restructuring of coarse fibrous bone tissue into lamellar bone tissue, are described. Conclusions. Reparative osteogenesis is a complicated and coordinated process at both the cellular and molecular levels. The regeneration process depends on numerous local and systemic factors and the optimization search is carried out at each stage

Reparative osteogenesis in mandible in cases of filling a bone defect with hydroxyapatite-containing osteotropic material and injecting the surrounding soft tissues with thymalin: experimental and morphological study.

Aim of the study was to identify the morphological features of reparative osteogenesis in the lower jaw bone of rats in cases of filling a bone defect with hydroxyapatite-containing osteotropic material (bone graft "Biomin GT") and injecting the surrounding soft tissues with thymalin. Materials and Methods: An experiment was conducted on 48 mature rats of the WAG population weighing 160-180 grams which were divided into four groups. Group 1 included 12 rats with a simulated holey defect in the lower jaw. Group 2 included 12 rats with a simulated holey defect in the lower jaw followed by its closure with hydroxyapatite-containing osteotropic material (bone graft "Biomin GT"). Group 3 included 12 rats with a simulated holey defect in the lower jaw with injecting the surrounding soft tissues with thymalin. Group 4 included 12 rats with a simulated holey defect in the lower jaw followed by its closure with hydroxyapatite-containing osteotropic material (bone graft "Biomin GT") and injecting the surrounding soft tissues with thymalin. The material for the morphological study was a fragment of the lower jaw from the area of the simulated holey defect. Histological, morphometric and statistical research methods were used. Results: In this study, it was shown by the authors an activation of reparative osteogenesis in the lower jaw under conditions of simultaneous filling the bone defect with hydroxyapatite-containing osteotropic material (bone graft "Biomin GT") and injection the surrounding bone defect soft tissue with thymalin. Stimulation of reparative osteogenesis in the lower jaw of rats occurred due to rapid cleaning of the bone defect cavity from necrotic tissues and hematoma fragments; a decrease in the number of neutrophil leukocytes, an increase in the number and morphofunctional state of monocytes, macrophages, lymphocytes, cells of fibroblastic differon; balanced change (increase or decrease) in the number and morphofunctional state of bone forming osteoblasts and bone resorbing osteoclasts depending on the stage of reparative osteogenesis; activation of hematopoietic processes in lamellar bone tissue from the regenerate; activation of bone tissue mineralization processes. Conclusions: Thymalin injection in the soft tissues surrounding the bone defect in the lower jaw, filled with hydroxyapatite-containing osteotropic material (bone graft "Biomin GT"), significantly stimulates the process of reparative osteogenesis, which makes it possible to recommend this technique in dentistry for treatment the patients with mandible bone tissue defects.

Применение секретома ММСК для стимуляции репаративного остеогенеза: экспериментальное исследование

The article is devoted to the study of the effect obtained by using a regenerative medicine drug (secretome of multipotent mesenchymal stromal cells) to stimulate reparative regeneration of a long tubular bone after a fracture. The presented materials are a fragment of comprehensive studies on the mechanisms of reparative regeneration of bone tissue under the conditions of the use of cellular products. The work was carried out on outbred white rats, in which the state of the bone regenerate was studied on the 30th and 120th days after injury. After the fracture, the animals were kept under normal conditions, without immobilization or restriction of motor activity. The work used methods of anatomical preparation and light microscopy. Studies have shown that the use of a secretome was accompanied by a more reliable consolidation of fragments behind the ossification of the callus, in the structure of which by the final period of the experiment lamellar bone tissue predominated, against which foci were observed reticulofibrous bone tissue and small fragments of cartilaginous tissue with signs of osteolysis and replacement with bone tissue. In the control group, the reparative process occurred more slowly, foci of cartilaginous tissue remained in the structure of the regenerate for a long time, and the bone tissue was represented mainly by reticulofibrous tissue. A significant amount of connective tissue was revealed between the fragments. All this indicates instability and unreliable consolidation of fragments. Apparently, the secretome of multipotent mesenchymal stromal cells stimulates the repair of bone tissue in fractures by improving the trophic supply in the healing area, against the background of which the formation and remodeling of callus is activated.

Microarchitectonics and histomorphometric parameters of bone tissue during remodeling

The article shows and statistically substantiates thepeculiarities of remodeling and structure of cortical andmedullary bone tissue in two age groups (160- and 225days) of laying hens before and during egg-laying. Theaim of the study was to analyze the structural organization of bone tissue in different states of performance.The material for the study was the ulnae of the forearmof laying hens of two experimental groups. Histological studies: fixed in a 10% solution of neutral formalin,decalcified in Wilenson's fluid, dehydrated in alcoholsof increasing concentration, embedded in paraffin, prepared transverse sections from the middle third of thediaphysis, stained by Frankel, Hart, Malory, hematoxylin and eosin. Microscopy and morphometric studies were performed using an Axiolar plus microscope(Carl Zeiss), photographs were taken and measuredusing a Sigeta MDC-200 video camera (eyepiece x10,lenses x25/0.50, x40/0.65, 100/0.25) integrated with anAxiolar plus personal computer (Carl Zeiss). Statisticalprocessing of digital material was performed by Student's t-test. Changes in the structure of cortical bonetissue during the study period are associated with physiological remodeling. This is evidenced by the presenceof cementing lines of individual osteons, semi-osteonsand Haversian canals with an enlarged diameter. Theabsence or insignificant development of the insertionsystem of the forming bone plates indicates a low rateof physiological remodeling of the compact bone substance. The external general system of plates does notchange the structure. The internal general system ofbone plates is unevenly developed. From 160 to 225days of age, the development and accumulation ofmedullary bone tissue occurs, which is confirmed bya significant increase in the area of trabeculae by 2.8times (P3 = 0.999), a complication of their structureand a decrease in the area of intertrabecular spaces by1.7 times (P2 = 0.99). A significantly higher 3.4-fold(P1 = 0.95) volume of osteoblast nuclei at 160 days indicates their active functional activity - the formationof trabeculae of medullary bone tissue. During the period of 160 days, special attention should be paid to thebalance of the diet of laying hens to ensure the formation of a sufficient amount of high-quality medullarybone tissue. Key words: lamellar bone tissue, cortical, medullary, spongy and compact substance, restructuring,histomorphometry, laying hens.

Comparative evaluation of osseointegration of new percutaneous implants made of Ti Grade 4 ultrafine‑grained alloy

Introduction It has been shown that titanium implants with a structured surface provide an increased rate of osseointegration what makes their application quite promising.The purpose of this work was to conduct a comparative evaluation of the efficiency of osseointegration of new percutaneous implants for prosthetics made of ultrafine-grained Ti Grade 4 alloy.Materials and methods The study was carried out on 12 male rabbits of the Soviet Chinchilla breed. Six rabbits of the control group had implants made of Ti6Al4V powder using selective laser sintering technology that were osseointegrated into the tibia, 6 rabbits of the experimental group had implants made of Ti Grade 4 by equal channel angular pressing. The formation of the "bone-implant" block was examined 26 weeks after the implantation.Results Histologically, after 26 weeks of the experiment, porous changes, enlargement of the Haversian canals, and pronounced osteoclastic resorption were not detected in the animals of the experimental group throughout the stump in the compact plate. Around the implant, a bony case repeating the bone shape was formed, represented by lamellar bone tissue. Using X-ray electron probe microanalysis, it was found that in the substrate formed on the surface of the implant in rabbits of the experimental group, there was significantly more calcium in all areas over the implant relative to the animals of the control group. In the control group, relative to the experimental group, an increased level of C-reactive protein in blood serum was retained longer. Complications and significant clinical and laboratory abnormalities were not found in both groups during the entire experiment.Discussion Our data are consistent with the results of other experimental studies, which unambiguously noted that titanium implants with a structured surface show increased osseointegration characteristics in comparative studies relative to implants without modification of the structure of the material of the threaded surface. The absence of complications and undesirable reactions of the animal organism also indicates the acceptable safety of the tested products.Conclusion Osseointegration of a percutaneous implant that has a mixed nanocrystalline and ultrafine-grained structure was more effective than the reference implant. This makes the use of such implant promising for solving clinical problems in prosthetics.

Origins of slow growth on the crocodilian stem lineage

Crocodilians grow slowly and have low metabolic rates similar to other living reptiles, but palaeohistology indicates that they evolved from an ancestor with higher growth rates.1,2,3,4,5 It remains unclear when slow growth appeared in the clade due to the sparse data on key divergences among early Mesozoic members of their stem lineage. We present new osteohistological data from a broad sample of early crocodylomorphs, evaluated in a phylogenetic context alongside other pseudosuchians. We find that the transition to slow-growing bone types during mid-late ontogeny occurred around the origin of Crocodylomorpha during the Late Triassic. Earlier-diverging pseudosuchians had high maximum growth rates, as indicated by the presence of woven bone during middle and (sometimes) late ontogeny.6,7,8,9 Large-bodied pseudosuchians in particular exhibit some of the fastest-growing bone types, giving evidence for prolonged, rapid growth. By contrast, early-branching crocodylomorphs, including a new large-bodied taxon, had slow maximum rates of bone deposition, as evidenced by the presence of predominantly parallel-fibered or lamellar bone tissue during middle-late ontogeny. Late Triassic crocodylomorphs show skeletal anatomy consistent with "active" terrestrial habits,10,11,12 and their slow growth rates reject hypotheses linking this transition with sedentary, semiaquatic lifestyles or sprawling posture. Faster-growing pseudosuchian lineages go extinct in the Triassic, whereas slow-growing crocodylomorphs do not. This contrasts with the Jurassic radiation of fast-growing dinosaurs on the bird-stem lineage,13 suggesting that the End-Triassic mass extinction initiated a divergent distribution of growth strategies that persist in present-day archosaurs.

Paleobiological implications of the bone histology of the extinct Australian marsupial Nimbadon lavarackorum

AbstractDespite the recognition that bone histology provides much information about the life history and biology of extinct animals, osteohistology of extinct marsupials is sorely lacking. We studied the bone histology of the ca. 15-million-year-old Nimbadon lavarackorum from Australia to obtain insight into its biology. The histology of thin sections of five femora and five tibiae of juveniles, subadult, and adult Nimbadon lavarackorum was studied. Growth marks in the bones suggest that N. lavarackorum took at least 7–8 years (and likely longer) to reach skeletal maturity. The predominant bone tissue during early ontogeny is parallel-fibered bone, whereas an even slower rate of bone formation is indicated by the presence of lamellar bone tissue in the periosteal parts of the compacta in older individuals. Deposition of bone was interrupted periodically by lines of arrested growth or annuli. This cyclical growth strategy indicates that growth in N. lavarackorum was affected by the prevailing environmental conditions and available resources, as well as seasonal physiological factors such as decreasing body temperatures and metabolic rates.

EXPERIMENTAL AND MORPHOLOGICAL ASSESSMENT OF THE INFLUENCE OF HYDROXYAPATITE-CONTAINING OSTEOTROPIC MATERIAL AND ELECTRICAL STIMULATION ON REPARATIVE OSTEOGENESIS OF THE LOWER JAW.

Aim: The aim of the study was to reveal the peculiarities of reparative osteogenesis in experimental lower jaw defect under the conditions of hydroxyapatite-containing osteotropic material application and electrical stimulation. Materials and Methods: An experiment was conducted on 48 mature male rats of the WAG population. All animals were divided into 4 groups (12 animals in each group). Group 1 included rats that were not subjected to any manipulations. Group 2 included rats that were modeled with a perforated defect of the lower jaw body. Group 3 included rats that were modeled with a perforated defect similar to group 2, the cavity of which was filled with synthetic bone graft "Biomin GT" (RAPID, Ukraine). Group 4 included animals that were modeled with a perforated defect similar to groups 2-3, the cavity of which was filled with synthetic bone graft "Biomin GT". In animals of group 4, a microdevice for electrical action was implanted subcutaneously in the neck area on the side of the simulated bone defect. Morphological and statistical methods were used. Results: The research carried out by the authors proved that the use of the above-mentioned bone replacement material helps to increase the regenerative potential of the bone tissue of the lower jaw, but does not lead to the formation of a full-fledged bone regenerate, as evidenced by the results of the morphometry of the regenerate (the specific volume of lamellar bone tissue accounted for 54.9%); disordered localization of bone beams, which were characterized by reduced signs of mineralization; the presence in connective, osteogenic fibroreticular and lamellar bone tissues the encapsulated bone graft granules with the presence of inflammatory cell infiltration. In cases the combined use of synthetic bone graft "Biomin GT" and electrical stimulation, the authors noted more intensive reparative osteogenesis processes in the bone defect of the lower jaw compared to cases when only one bone graft was used, but they also did not lead to the formation of a full-fledged bone regenerate. Conclusions: The experimental and morphological study conducted by the authors proved that the use of hydroxyapatite-containing osteotropic material ("Biomin GT"), especially in cases of its combined use with electrical stimulation, significantly activates reparative osteogenesis in the bone defect of the lower jaw, which does not lead to the formation of a full-fledged bone regenerate.

Comparative postcranial osteohistology and bone histovariability of aquatic and terrestrial turtles: the case of the South American Phrynops hilarii, Hydromedusa tectifera (Pleurodira, Chelidae), and Chelonoidis chilensis (Cryptodira, Testudinidae).

This article presents a detailed comparative analysis of the bone microstructure of three extant species of South American turtles. The main histological characteristics of postcranial bones are identified, as well as the intraskeletal, ontogenetic and interspecific variation between aquatic and terrestrial species. For this purpose, thin sections of postcranial bones (seventh cervical vertebra, coracoid, scapula, humerus, radius, ulna, ischium, ilium, pubis, femur, tibia, and fibula) of juvenile and adult specimens of aquatic (Phrynops hilarii and Hydromedusa tectifera) and terrestrial (Chelonoidis chilensis) turtles were analyzed. Bone histology revealed an intraskeletal variation of the microanatomical and microstructural organization in these turtles. The cortical bone is composed of poorly vascularized lamellar and parallel-fibered bone tissue interrupted with lines of arrested growth (LAGs), reflecting a cyclical slow growth rate throughout these turtles' life. Although in the adult specimens a growth rate decrease was observed, none of them have reached somatic maturity. The juvenile and the adult of Chelonoidis chilensis, unlike the aquatic species studied, presented a higher vascularization in their bones, which could imply a faster growth rate in this land specie. The number of LAGs was higher in the stylopodial and zeugopodial bones, which would make these elements suitable for approximate age estimations. Pectoral and pelvic girdle bones also exhibited a good record of LAGs. The information here obtained on extant species represents a powerful tool for the interpretation of paleobiological traits present in closely related fossil forms.

ИЗУЧЕНИЕ ВАСКУЛЯРИЗАЦИИ И РЕПАРАТИВНОЙ РЕГЕНЕРАЦИИ ПЛАСТИНЧАТОЙ КОСТНОЙ ТКАНИ В ИСКУССТВЕННО СМОДЕЛИРОВАННЫХ ДЕФЕКТАХ ВЕРХНЕЙ ЧЕЛЮСТИ (экспериментальное исследование)

Subject. Regeneration is one of the most relevant problems of medicine and biology. As it was before and as it is now, the field of investigation, which is connected with regeneration exploring, is a range of heated debates. There is a direct correlation between regeneration of bones and local metabolism, mineralization and early vascularization, which supplies nourishment and oxygenation of cell structure of the regenerate. Owing to these factors, the bone has only its mechanic properties. This prerequisite has made a lot of investigators to pay attention for vascular-regeneration complex in zone of forming bone regenerate and its mineralization. 
 Such adverse circumstances like lack of local circulation, substantial fragment diastasis, excessive instability and etc. do not generate or form delayed intermediate callus. It should be highlighted that there are significant successes in solving reparative regeneration and cortical bone vascularization problems. Nevertheless, a number of problems are not still tackled, they regard to vascularization and reparative regeneration lamellar bone tissue, particularly, middle zone of the facial bone.
 Objectives. The study on the base of the experimental researches, to explore the dynamics of reparative regeneration lamellar bone tissue with simulated different size defects of naso-frontal area of rabbit maxilla. 
 Methodology. Materials of the experiment are comprised of IV series of experiments on 68 adults (from 6 months to a year), both sexes rabbits, of “Chinchilla” breed, weighing from 2.5–3.0 kg. 
 All animals were kept in the vivarium of the experimental sector of
 Institute of Medical Radiology of the Academy of Medical Sciences of the USSR. The investigations included microangiographic, histological and metering quantity of vessels by laser densitometry.
 Results. It is noted that vascularization abruptly decreases in remote periods of the observation (180, 365 days) and a tendency in an amount reduction of the regenerate vessels, which the proved by histological researches results. 
 Conclsion. Healing of naso-frontalis area defects with a height of 5 mm and more flows from mostly fibrocartilaginous compound, under unfavorable conditions are not restored by bone regenerate.

A Biocompatible Ultrananocrystalline Diamond (UNCD) Coating for a New Generation of Dental Implants.

Implant therapy using osseointegratable titanium (Ti) dental implants has revolutionized clinical dental practice and has shown a high rate of success. However, because a metallic implant is in contact with body tissues and fluids in vivo, ions/particles can be released into the biological milieu as a result of corrosion or biotribocorrosion. Ultrananocrystalline diamond (UNCD) coatings possess a synergistic combination of mechanical, tribological, and chemical properties, which makes UNCD highly biocompatible. In addition, because the UNCD coating is made of carbon (C), a component of human DNA, cells, and molecules, it is potentially a highly biocompatible coating for medical implant devices. The aim of the present research was to evaluate tissue response to UNCD-coated titanium micro-implants using a murine model designed to evaluate biocompatibility. Non-coated (n = 10) and UNCD-coated (n = 10) orthodontic Ti micro-implants were placed in the hematopoietic bone marrow of the tibia of male Wistar rats. The animals were euthanized 30 days post implantation. The tibiae were resected, and ground histologic sections were obtained and stained with toluidine blue. Histologically, both groups showed lamellar bone tissue in contact with the implants (osseointegration). No inflammatory or multinucleated giant cells were observed. Histomorphometric evaluation showed no statistically significant differences in the percentage of BIC between groups (C: 53.40 ± 13% vs. UNCD: 58.82 ± 9%, p > 0.05). UNCD showed good biocompatibility properties. Although the percentage of BIC (osseointegration) was similar in UNCD-coated and control Ti micro-implants, the documented tribological properties of UNCD make it a superior implant coating material. Given the current surge in the use of nano-coatings, nanofilms, and nanostructured surfaces to enhance the biocompatibility of biomedical implants, the results of the present study contribute valuable data for the manufacture of UNCD coatings as a new generation of superior dental implants.

A multiscale finite element investigation on the role of intra- and extra-fibrillar mineralisation on the elastic properties of bone tissue

Lamellar bone is one of the fundamental structural units of bone tissue and it consists of mineralised collagen fibrils (MCFs) embedded within an extra-fibrillar matrix comprised of hydroxyapatite minerals distributed throughout a matrix of non-collagenous proteins (NCPs). While both intra- and extra-fibrillar phases provide a critical contribution to tissue-level behaviour, the mechanical implications of their structural arrangement, and in particular the relative distribution of HA minerals between both phases, remains poorly understood. This study presents a multiscale finite element framework to investigate the role of intra- and extra-fibrillar mineralisation on the elastic properties of bone tissue by considering two levels of structural hierarchy. At the nanoscale, representative volume elements (RVEs) of both MCFs and the extra-fibrillar matrix were developed, and a homogenisation strategy was used to determine the effective elastic properties of each phase. At the sub-micron level, an RVE of lamellar bone that accounted for newly reported patterns of mineral platelets encircling collagen fibrils was used to predict the effective response of lamellar bone tissue, with material properties established from the previous length scale. The results demonstrated that the overall mineral content in the tissue is the biggest contributor to the effective elastic properties of lamellar bone. While this is perhaps unsurprising, importantly, it was demonstrated that the extra-fibrillar matrix (and mineral therein) is the phase that makes the primary contribution to the elastic response of the tissue. The two main reasons that the extra-fibrillar matrix dominated the load-bearing response are (i) the greater proportion of mineral content compared to the intra-fibrillar regions and (ii) the highly ordered arrangement of mineral platelets that are aligned to the longitudinal axis of MCFs. Both of these features resulted in extra-fibrillar mineral strain ratios that were consistently higher than intra-fibrillar mineral strain ratios under axial loading. As a result, the predicted elastic properties of MCFs were much lower than the extra-fibrillar matrix, indicating that intra-fibrillar mineralisation only provided a modest contribution to the stiffness of bone tissue. Collectively, the predicted results of the multiscale approach compared well to the range properties measured through various experimental testing methods, highlighting its potential to provide further insight into the role of sub-tissue features of tissue biomechanics.

Строение и места наименьшей устойчивости костно-сухожильных соединений сгибателей пальца лошади

We studied the peculiarities of the structure and functions of bone tendon compounds (enthusis). The subject of the study is a horse. Subject of investigation – places of attachment of tendons of superficial finger flexor, deep finger flexor. Light microscopy, polarization microscopy and biomechanics were used. The general patterns of the structure of enthesis that belong to the fibrous cartilage and fibrous types are established. In the enthesis of the fibrous cartilage type there are zones of tendon, fibrous cartilage, mineralized fibrous cartilage, lamellar bone tissue. Areas of tendon, reticulofibrous bone tissue, lamellar bone tissue were identified in fibrous type enthesis. Biomechanical enthesis of different types are different. In fibrous cartilaginous entesis, the microhardness of tissues changes smoothly, in fibrous – more dramatically. It is shown that the fibrous-cartilaginous enthesis are adapted to dissipate the stresses that arise when the tendon is stretched. Fibrous-type enthesis tightly fix tendons on the bone. The revealed structural and functional features ensure the functional reliability of the entheses. But there are also places of least stability – stress concentration zones. These are the mineralization front, as well as the resorption cavities that occur during the remodeling of mineralized cartilage and subchondral bone. During overloads, they can be injured and lead to the occurrence of enthesopathies.

MORPHOLOGICAL FEATURES OF TUBULAR BONES REPARATIVE REGENERATION UNDER THE INFLUENCE OF ANTITUMOR CHEMOTHERAPEUTICS

The aim: Determination of morphological features of reparative regeneration of diaphysis defect of long tubular bones under the influence of antitumor chemotherapeutics in a model experiment. Materials and methods: 96 white nonlinear rats after application of the perforated defect of the femur were administered the appropriate antitumor drug (doxorubicin, 5-fluorouracil, methotrexate) three times with an interval of 21 days. Morphological features of bone tissue formation and remodeling in the regenerate area were studied using histological and morphometric methods. Results: The inhibitory effect of antitumor chemotherapeutics on the formation of regenerate, expressed by slowing down the process of bone tissue differentiation was found. This is confirmed by a decrease in the area of reticulofibrous and lamellar bone tissue, chaotic arrangement and narrowing of bone trabeculae with uneven color, slow formation of bonding lines between the maternal bone and the regenerate. Conclusions: The revealed morphological features of reparative regeneration of the diaphysis defect of long tubular bones under the influence of antitumor chemotherapeutics doxorubicin, 5-fluorouracil and methotrexate in a model experiment indicate a slowing of reparative regeneration processes at all stages of recovery after injury.

Bone histology of dinocephalians (Therapsida, Dinocephalia): palaeobiological and palaeoecological inferences

AbstractWe investigate the bone histology of multiple skeletal elements of dinocephalian taxa from the middle PermianTapinocephalusAssemblage Zone of the Karoo Basin of South Africa. The results show that the cortex is predominantly composed of fibrolamellar bone, suggesting rapid osteogenesis for these basal non‐mammalian therapsids. However, in a few skeletal elements, growth marks interrupt the deposition of the fibrolamellar bone tissue, indicating periodic arrests in growth. Ontogenetic differences are observed among the specimens studied: the majority have fibrolamellar bone deposited up to the peripheral margin of the bone wall, indicating continuous fast growth right up to the time of death, while a few specimens have avascular lamellar bone tissue with multiple, closely spaced rest lines, indicating maturity and a slowing down of growth prior to death. Several taxon‐specific histological variations in terms of orientation of vascular canals and primary osteons, incidence of growth marks, and extent of secondary medullary reconstruction suggest slight differences in growth trajectories between the different taxa. The skeletal elements of the herbivorous taxa (Keratocephalus,MoschopsandStruthiocephalus) and the omnivorousJonkeria, previously studied, are characterized by a thick cortex, and extensively developed medullary spongiosa, suggestive of semi‐aquatic habits. In contrast, the femoral histology of the carnivorousAnteosaurussuggests that it was more terrestrial.

Морфологічні аспекти репаративної регенерації кісткової тканини в умовах впливу протипухлинної хіміотерапії

The occurrence of fractures in the development of cancer in the body is due to changes in bone metabolism in the form of osteoporosis and metastatic bone damage. Their appearance leads to the postponement or cessation of treatment of cancer, which affects the life expectancy of such patients and the chances of recovery. Antitumor chemotherapy, as one of the main methods of cancer treatment, is prescribed for long-term courses and affects the healing of fractures. However, according to the literature, the effect of antitumor chemotherapeutics on reparative regeneration is poorly understood today. The purpose of the work is to study the morphological features of reparative osteogenesis under the influence of antitumor chemotherapy. Materials and methods. The study was performed on 96 white laboratory male rats 7 months of age weighing 230±10 g. All animals had a perforated defect with a diameter of 2 mm spherical cutter to the bone marrow canal in the middle third of the femoral shaft. Animals were divided into control (n = 24, without chemotherapy) and three experimental groups (I, II, III, n = 72), which after injury and every 21 days of the study were administered intraperitoneal anticancer chemotherapeutics: I (n = 24) – doxorubicin (60 mg / m²), II (n = 24) – 5-fluorouracil (600 mg / m²), III (n = 24) – methotrexate (40 mg / m²). On the 15th, 30th, 45th, 60th days after injury, the animals were removed from the experiment, followed by removal of the injured long tubular bones. Histological preparations stained with hematoxylin-eosin, followed by their morphometry, scanning electron microscopy with the method of X-ray energy dispersion spectroscopy, immunohistochemical examination were performed. Results and discussion. Antitumor chemotherapeutics causes delayed callus formation, which is manifested by an increase in the area of connective and reticulofibrous bone tissue in the regenerate, along with the slow formation of lamellar bone tissue. Chemotherapy leads to disorders of phosphorus-calcium metabolism both in the regenerate and in the maternal bone in the form of reducing the intensity of mineralization of the newly formed bone matrix and slowing down the remodeling activity of the maternal bone. Chemotherapy is accompanied by an increase in the expression of the bone resorption marker cathepsin K and a decrease in the expression of the osteopontin bone marker, which indicates a delay in the formation of regenerate in the area of injury and a decrease in the rate of reparative regeneration. Conclusion. The most pronounced delay in the processes of remodeling of bone regenerate was found with the use of doxorubicin and methotrexate, while 5-fluorouracil showed less inhibitory effect on these processes

Inter-element variation in the bone histology ofAnteosaurus(Dinocephalia, Anteosauridae) from theTapinocephalusAssemblage Zone of the Karoo Basin of South Africa

Despite its abundance in the Permian fossil record of South Africa, little is known about the life history of Anteosaurus. Here we examine the bone microstructure of multiple skeletal elements of Anteosaurus from the Tapinocephalus Assemblage Zone of the Karoo Basin. The bone histology of Anteosaurus magnificus reveals that the cortex is composed of highly vascularized, uninterrupted fibrolamellar bone tissue surrounding the inner spongy medullary region. However, the histology of two ribs and a previously described femur of another Anteosaurus taxon revealed an interrupted growth pattern with lines of arrested growth and peripheral rest lines occurring in the compacta, indicating periodic pauses in growth possibly linked to the slowing down of growth during maturity. Given that the fibula of the same individual has well-vascularised fibrolamellar bone tissue without any growth marks in the cortex; this suggests variation in skeletal growth. Based on our histological results, three growth dynamic stages are deduced for the genus Anteosaurus: (i) the earliest growth stage is represented by the predominance of highly vascularized, uninterrupted fibrolamellar bone tissue in the inner cortex, which suggests rapid periosteal bone deposition during early ontogeny; (ii) the next stage of growth shows periodic interruptions in the bone deposition as indicated by the deposition of lines of arrested growth; (iii) the third stage shows the development of lamellar bone tissue with rest lines in the peripheral part of the cortex suggesting a slowing down of growth prior to death. Most of the skeletal elements are characterized by thick bone walls, extensive secondary reconstruction and the complete infilling of the medullary cavity. However, the radius and a previously studied femur have open medullary cavities with struts of bony trabeculae. Based on histologic structures and comparisons with extant taxa, it is likely that Anteosaurus may have been more terrestrial as its osteology point towards terrestriality, but it may have occasionally inhabited ephemeral pools like modern semi-aquatic Hippopotamus.

Reparative histogenesis of bone tissue in femoral fractures in rats using biocomposite material along with immunocorrection

The paper studies the effect of the RVI biocomposite material belonging to the group of osteoplastic biocomposite materials, the RV-2 immunomodulator – a synthetic dipeptide inducing an immunocorrective effect, and combinations of these drugs on the reparative histogenesis of bone tissue in femoral fractures in rats. It was found that the remodeling of the primary bone callus into the secondary one in the fracture of the studied animals was of a diverse nature. This process was the most pronounced in the group where the components were used in complex, i.e. the bone defect was filled with RVI during the surgery, as well as RV-2 was injected intramuscularly to rats at a dose of 10 mcg per 1 kg of live weight for five days, starting immediately after the surgery. Well-formed coarse-fibrous connective tissue callus was recorded in animals of this group. The connective tissue was stained more intensely which indicates a denser arrangement of fibers in the callus. Focal cartilage tissue spanning bone fragments was observed within the callus. At the periphery of the site the cartilaginous callus was subjected to endochondral ossification with replacement by coarse-fibrous trabeculae with elements of lamellar bone tissue having haversian canals in the center. The inter-girdle spaces were filled with elements of the myeloid bone marrow in the forming bone tissue. Markedly proliferated osteoblasts were visible in the cambial layer of the periosteum. The bone tissue ratio increased up to (60.21 ± 2.62)%, which significantly exceeded the same indicator in the control group and in all experimental groups. The low content of connective tissue and the high ratio of bone tissue indicated more active osteogenesis processes and reparative regeneration in comparison with other groups.

Results of morphological studies of bone tissue regeneration based on conceptual approaches in surgical dentistry

Oral and maxillofacial implantology has a trend towards continuous improvement. The problem being developed lies in the plane of restoration of defects in the jaw bone formed for various reasons. The range of implantation materials is constantly changing, but their structure remains unchanged – monolithic. Digital technology allows us the creation of structured implants. We have proposed designs consisting of a face-centered cubic crystal lattice and developed a technological map. Morphological studies carried out after 1, 3, 4 and 9 months after transplantation of an implant with cells of 250, 550, and 850 microns in size, showed that during these periods all cells contained lamellar bone tissue with the only difference that about a number of smaller bridges at 4 months still there are separate islands of coarse fibrous bone. This indicates a promising direction in reconstructive surgery. A retrospective study over a 15-year follow-up period after plastic surgery showed their ineffectiveness. Out of 85 plastic surgeries performed, complications were detected in 9 (37.5%) patients, which indicates the need to search for new changes in the structure of materials. Recently, in certain clinical cases, certain successes have already been achieved. However, more research is still at the theoretical development stage without the use of preclinical experimental and clinical trials.