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PubMed2004

Mechanisms regulating differential activation of membrane-mediated signaling by 1alpha,25(OH)2D3 and 24R,25(OH)2D3.

Vitamin D metabolites 1alpha,25(OH)(2)D(3) and 24R,25(OH)(2)D(3) regulate endochondral ossification in a cell maturation-dependent manner via membrane-mediated mechanisms. 24R,25(OH)(2)D(3) stimulates PKC activity in chondrocytes from the growth plate resting zone, whereas 1alpha,25(OH)(2)D(3) stimulates PKC in growth zone chondrocytes. We used the rat costochondral growth plate cartilage cell model to study how these responses are differentially regulated. 1alpha,25(OH)(2)D(3) acts on PKC, MAP kinase, and downstream physiological responses via phosphatidylinositol-specific PLC-beta; 24R,25(OH)(2)D(3) acts via PLD. In both cases, diacylglycerol (DAG) is increased, activating PKC. Both cell types possess membrane and nuclear receptors for 1alpha,25(OH)(2)D(3), but the mechanisms that render the 1alpha,25(OH)(2)D(3) pathway silent in resting zone cells or the 24R,25(OH)(2)D(3) pathway silent in growth zone cells are unclear. PLA(2) is pivotal in this process. 1alpha,25(OH)(2)D(3) stimulates PLA(2) activity in growth zone cells and 24R,25(OH)(2)D(3) inhibits PLA(2) activity in resting zone cells. Both processes result in PKC activation. To understand how negative regulation of PLA(2) results in increased PKC activity in resting zone cells, we used PLA(2) activating peptide to stimulate PLA(2) activity and examined cell response. PLAP is not expressed in resting zone cells in vivo, supporting the hypothesis that PLA(2) activation is inhibitory to 24R,25(OH)(2)D(3) action in these cells.

24,25-Dihydroxyvitamin D 3↗
PubMed1999

Retinoid signaling is required for chondrocyte maturation and endochondral bone formation during limb skeletogenesis.

Retinoids have long been known to influence skeletogenesis but the specific roles played by these effectors and their nuclear receptors remain unclear. Thus, it is not known whether endogenous retinoids are present in developing skeletal elements, whether expression of the retinoic acid receptor (RAR) genes alpha, beta, and gamma changes during chondrocyte maturation, or how interference with retinoid signaling affects skeletogenesis. We found that immature chondrocytes present in stage 27 (Day 5.5) chick embryo humerus exhibited low and diffuse expression of RARalpha and gamma, while RARbeta expression was strong in perichondrium. Emergence of hypertrophic chondrocytes in Day 8-10 embryo limbs was accompanied by a marked and selective up-regulation of RARgamma gene expression. The RARgamma-rich type X collagen-expressing hypertrophic chondrocytes lay below metaphyseal prehypertrophic chondrocytes expressing Indian hedgehog (Ihh) and were followed by mineralizing chondrocytes undergoing endochondral ossification. Bioassays revealed that cartilaginous elements in Day 5.5, 8.5, and 10 chick embryo limbs all contained endogenous retinoids; strikingly, the perichondrial tissues surrounding the cartilages contained very large amounts of retinoids. Implantation of beads filled with retinoid antagonist Ro 41-5253 or AGN 193109 near the humeral anlagens in stage 21 (Day 3.5) or stage 27 chick embryos severely affected humerus development. In comparison to their normal counterparts, antagonist-treated humeri in Day 8.5-10 chick embryos were significantly shorter and abnormally bent; their diaphyseal chondrocytes had remained prehypertrophic Ihh-expressing cells, did not express RARgamma, and were not undergoing endochondral ossification. Interestingly, formation of an intramembranous bony collar around the diaphysis was not affected by antagonist treatment. Using chondrocyte cultures, we found that the antagonists effectively interfered with the ability of all-trans-retinoic acid to induce terminal cell maturation. The results provide clear evidence that retinoid-dependent and RAR-mediated mechanisms are required for completion of the chondrocyte maturation process and endochondral ossification in the developing limb. These mechanisms may be positively influenced by cooperative interactions between the chondrocytes and their retinoid-rich perichondrial tissues.

Animals↗
PubMed2004

Dmp1-deficient mice display severe defects in cartilage formation responsible for a chondrodysplasia-like phenotype.

Understanding the molecular mechanisms by which cartilage formation is regulated is essential toward understanding the physiology of both embryonic bone development and postnatal bone growth. Although much is known about growth factor signaling in cartilage formation, the regulatory role of noncollagenous matrix proteins in this process are still largely unknown. In the present studies, we present evidence for a critical role of DMP1 (dentin matrix protein 1) in postnatal chondrogenesis. The Dmp1 gene was originally identified from a rat incisor cDNA library and has been shown to play an important role in late stage dentinogenesis. Whereas no apparent abnormalities were observed in prenatal bone development, Dmp1-deficient (Dmp1(-/-)) mice unexpectedly develop a severe defect in cartilage formation during postnatal chondrogenesis. Vertebrae and long bones in Dmp1-deficient (Dmp1(-/-)) mice are shorter and wider with delayed and malformed secondary ossification centers and an irregular and highly expanded growth plate, results of both a highly expanded proliferation and a highly expanded hypertrophic zone creating a phenotype resembling dwarfism with chondrodysplasia. This phenotype appears to be due to increased cell proliferation in the proliferating zone and reduced apoptosis in the hypertrophic zone. In addition, blood vessel invasion is impaired in the epiphyses of Dmp1(-/-) mice. These findings show that DMP1 is essential for normal postnatal chondrogenesis and subsequent osteogenesis.

Animals↗
PubMed2001

Ossification of tracheal cartilage in aged humans: a histological and immunohistochemical analysis.

Tracheal cartilage has been considered as permanent cartilage without endochondral ossification. We examined ossification of the tracheal cartilage in 25 adults (mean age 67.8 years; range 20-87 years; male:female = 17:8). Thirteen cases (52%) demonstrated ossification of the tracheal cartilage, accompanied by the formation of lamellar bones with fatty bone marrow. Ossification was observed at the lateral peripheral region of the tracheal cartilage, while vascular invasion into the cartilage was seen even where no ossification was present. Twenty-two cases (88%) showed marked hyalinization in the central region of the tracheal cartilage. Type II collagen was immunolocalized in the cartilage matrix, except for in the central hyalinized area, while type I collagen was immunolocalized around the perichondrium and ossified areas in the tracheal cartilage. Type X collagen immunolocalized on territorial matrices around the lacunae near the ossified regions. These results suggest that tracheal cartilage in aged humans frequently ossifies physiologically, and that aging promotes osteogenesis, even in permanent cartilage.

Adult↗
PubMed2004

Costal cartilages--a clue for determination of sex.

Mineralization and ossification in the human costal cartilages were studied radiologically. The aim of our study was to evaluate differences between males and females with respect to patterns of costal cartilage calcification and also with respect to ageing. Material for this study consists of 1044 chest and abdominal radiograms of the Czech population from the Department of Radiology (537 males and 507 females). Further radiograms of 18 chest plates were obtained at routine necropsy of cadavers. The radiograms were examined for pattern of ossification of the costal cartilage. The first rib cartilages were not considered because there are no sex differences. The lower ribs exhibit sexual dimorphism. Mineralization and ossification changes appear at the end of puberty and their occurrence increases with age. The sexual difference in pattern of human costal cartilages is statistically significant and thus highly predictive of sex determination.

Adolescent↗
PubMed1979

Ossification and mineralization in the tendons of the chicken (Gallus domesticus).

Fifty broiler chickens of both sexes were used in this study. The chickens were bought at 8 weeks old and kept until 40 weeks old. During this period the development of ossification and mineralization was followed. The chickens were killed at weekly intervals. After having been examined fresh, the tendons were fixed in appropriate fixatives and processed for histological and histochemical examination. The earliest signs of mineralization were noted at 15 weeks and mineralization was apparent on X-ray photographs at 20 weeks. The development of ossification of the tendons has been described. The fibroblasts transformed into osteoblasts which secreted around the cells and later between the fibres. This was followed by the appearance of osteoblasts and resorption cavities and then the latter became lined by osteoblasts, and osteones were formed.

Animals↗
PubMed1997

Onset of epiphyseal mineralization and growth plate closure in radiographically normal and dysplastic Labrador retrievers.

OBJECTIVE: To determine whether onset of mineralization of the femoral and proximal tibial epiphyses and age at closure of the femoral and acetabular triradiate growth plates was different for Labrador Retrievers that were radiographically normal or that had canine hip dysplasia (CHD). DESIGN: Cohort study. ANIMALS: 36 Labrador Retriever puppies. PROCEDURE: Puppies were radiographed every other day from the time they were 8 to 10 days old until ossification of the femoral heads was apparent. Radiographs were then obtained weekly until puppies were 1 month old and then monthly until puppies were 8 to 12 months old. Age at which mineralization was first observed in the proximal and distal femoral and proximal tibial epiphyses and at which the femoral capital, triradiate acetabular, and distal femoral growth plates were no longer radiographically visible were recorded. Fifteen dogs were euthanatized and necropsied to determine whether dogs had CHD. RESULTS: There were 26 radiographically normal left and right hip joints and 10 dysplastic left and right hip joints. Onset of mineralization of the proximal femoral epiphyses and of the right proximal tibial epiphysis was significantly later in dysplastic than in radiographically normal puppies. The left femoral capital growth plates closed significantly later in dysplastic than in radiographically normal joints, but other differences in growth plate closure were not detected. CLINICAL IMPLICATIONS: Endochondral ossification may be abnormal in dogs with CHD. The disease appears to affect multiple joints, even though it is most evident clinically in the hip joint.

Aging↗
PubMed2006

The discoidin domain receptor DDR2 is a receptor for type X collagen.

During endochondral ossification, collagen X is deposited in the hypertrophic zone of the growth plate. Our previous results have shown that collagen X is capable of interacting directly with chondrocytes, primarily via integrin alpha2beta1. In this study, we determined whether collagen X could also interact with the non-integrin collagen receptors, discoidin domain receptors (DDRs), DDR1 or DDR2. The widely expressed DDRs are receptor tyrosine kinases that are activated by a number of different collagen types. Collagen X was found to be a much better ligand for DDR2 than for DDR1. Collagen X bound to the DDR2 extracellular domain with high affinity and stimulated DDR2 autophosphorylation, the first step in transmembrane signalling. Expression of DDR2 in the epiphyseal plate was confirmed by RT-PCR and immunohistochemistry. The spatial expression of DDR2 in the hypertrophic zone of the growth plate is consistent with a physiological interaction of DDR2 with collagen X. Surprisingly, the discoidin domain of DDR2, which fully contains the binding sites for the fibrillar collagens I and II, was not sufficient for collagen X binding. The nature of the DDR2 binding site(s) within collagen X was further analysed. In addition to a collagenous domain, collagen X contains a C-terminal NC1 domain. DDR2 was found to recognise the triple-helical region of collagen X as well as the NC1 domain. Binding to the collagenous region was dependent on the triple-helical conformation. DDR2 autophosphorylation was induced by the collagen X triple-helical region but not the NC1 domain, indicating that the triple-helical region of collagen X contains a specific DDR2 binding site that is capable of receptor activation. Our study is the first to describe a non-fibrillar collagen ligand for DDR2 and will form the basis for further studies into the biological function of collagen X during endochondral ossification.

Animals↗
PubMed1987

Skeletal age assessment using the first, second, and third fingers of the hand.

The purpose of this study was to determine whether skeletal age assessments using the first, second, and third fingers of the hand are as valid as those using the entire hand-wrist. Previous studies have demonstrated that treatment can be better oriented to the unique physiologic characteristics of the individual if skeletal age is used to assess maturational status. The sample was selected from the files of the Bolton-Brush Foundation and consisted of radiographs of 19 male and 20 female subjects whose yearly hand-wrist radiographs were available covering the age span of 10 to 16 years for girls and 12 to 18 years for male subjects. Two maturity indicators, the sesamoid and the epiphyseal-diaphyseal stages of ossification, were evaluated. Reliability of the method was tested by the t test for paired comparisons and the Pearson product-moment correlation. To determine the validity of the method, an analysis of variance (ANOVA) was used. In addition, the Pearson product-moment correlations between the two methods were performed and the 95% confidence intervals for mean differences for each sex and time were calculated. As indicated by the ANOVA, the two methods differed by a statistically significant amount, with the three-fingers assessments being slightly more advanced than the hand-wrist assessments. Although they differed, for the male subjects, the three-fingers method never deviated from that of the hand-wrist by more than 2.89 months with a minimum deviation of 0.32 months. For the female subjects, the maximum deviation was 4.45 months with a minimum of 1.55 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

Prenatal toxicity of xylene.

Prenatal inhalation toxicity of xylene (industrial mixture of isomers) was studied in experiments of white Wistar rats exposed daily (6 hours a day, 5 days in a week) to concentrations of 10, 50 (MAC for xylene in the air of work environment in Bulgaria) and 500 mg.m-3 throughout the period of gestation from the first to the 21st day. Both routine teratological indices and biochemical and physiological methods of observation were used to evaluate the integrity of the individual organs - liver, brain, lungs and myocardium of the generation in the postnatal period of development. In concentrations of 50 and 500 mg.m-3, xylene exhibits pronounced embryotoxic and teratogenic effects. Postimplantation embryonal mortality increases, the process of physical development of the fetus is delayed, the incidence of induced anomalies of internal organs (hydrocephalus, microphthalmia, intracerebral haematomas, haemorrhages in the liver) is enhanced, the processes of ossification of the sternum and the skull are impaired. In concentrations of 50 and 500 mg.m-3, xylene causes disturbances in postnatal development of F1 generation. The concentration of 50 mg.m-3 is the threshold of the embryotropic effect of the solvent. Measures for the protection of women at work are proposed to reduce industrial hazard of developing antenatal pathology in the newborn of workwomen in xylene works.

Abnormalities, Drug-Induced↗
PubMed1999

Rickets on MR images.

BACKGROUND: The pathologic changes at the physis in patients with rickets have been well demonstrated histologically. Radiographs can depict only the associated osseous abnormalities. PATIENTS AND METHODS: We report two children in whom MR imaging demonstrated rachitic changes in the physeal cartilage beyond the well-recognized bony features. RESULTS: The striking appearance of the physes and the physes of the secondary ossification centers confirm that MR imaging can successfully evaluate the cartilaginous structures of the developing skeleton. CONCLUSION: Though MR imaging is clearly unnecessary for the diagnosis of rickets, it is important that the typical features are not misinterpreted as other pathology.

Bone and Bones↗
PubMed1991

[Ultrasonography of the borderline between normal and pathological state of the hip in newborn infants (borderline hip)].

Infant hips are classified, according to Graf, in 4 US types on the basis of the morphologic changes in both the cartilaginous and the bony roofs (type I, II, III, IV). Out of 6,000 examined hips, 170 (2.8%) were considered, which could be classified neither as type I (mature) nor as type II (delayed/immature ossification). These hips were called borderline hips. They exhibited some characteristic US features: good bone modeling, rounded cotyle, and alpha angle 60 degrees +/- 2. They were always observed during the first month of the patients' life. Anamnestic data were not specific (27.5% breech delivery, and 13% oligohydramnios); clinics sometimes overestimated the actual anatomic development (64/170 cases with positivity of Ortolani's sign and/or restricted abduction; 25% of patients presented with no suspicious signs). Dynamic hip examination showed only physiological cranial deflection of the cartilaginous roof. Finally, borderline hips developed into type I hips in 99% of cases, within the third month of the patients' life.

Follow-Up Studies↗
PubMed1994

Physiology of bone healing and bone grafts.

Contemporary head and neck hard tissue reconstruction incorporates bone transfers in the treatment of osseous discontinuity defects subsequent to congenital malformation, traumatic injury, ablative oncologic surgery, and failures of physiologic osteosynthesis. Bone grafts may also be applied in contour augmentation and in strengthening and stabilization roles in congenital and acquired aesthetic as well as posttraumatic deformities. The osseous healing process is dynamic and unique. An understanding of the physiology of these processes allows the reconstructive surgeon to choose techniques and donor sites appropriate to specific requirements, to maximize transplanted bone volume, to achieve consistent and reliable results, and to modulate the osseous healing process in a favorable direction.

Bone Regeneration↗
PubMed1998

Aerobic exercise for a patient with chronic multisystem impairments.

Many patients with long-term disabilities have inactive lifestyles that put them at risk for chronic diseases and secondary disabilities. The purpose of this case report is to illustrate the process of aerobic exercise prescription for a patient with chronic multisystem impairments. The patient was a 43-year-old man who incurred a traumatic brain injury and multiple fractures in a motorcycle accident 15 years previously. He subsequently developed heterotopic ossification around the right hip. In addition, the patient had a history of smoking. We chose a "nontraditional" mode of exercise for the patient that we believed would be safe and effective and would accommodate his neurologic and orthopedic impairments. The mode of exercise used was an apparatus in which the upper and lower extremities alternately flexed and extended in a nonreciprocal fashion. The patient attended 12 exercise sessions over a 1-month period, during which he demonstrated acute and chronic physiological responses appropriate for the exercise stimulus.

Activities of Daily Living↗
PubMed1998

Mechanobiology of skeletal regeneration.

Skeletal regeneration is accomplished by a cascade of biologic processes that may include differentiation of pluripotential tissue, endochondral ossification, and bone remodeling. It has been shown that all these processes are influenced strongly by the local tissue mechanical loading history. This article reviews some of the mechanobiologic principles that are thought to guide the differentiation of mesenchymal tissue into bone, cartilage, or fibrous tissue during the initial phase of regeneration. Cyclic motion and the associated shear stresses cause cell proliferation and the production of a large callus in the early phases of fracture healing. For intermittently imposed loading in the regenerating tissue: (1) direct intramembranous bone formation is permitted in areas of low stress and strain; (2) low to moderate magnitudes of tensile strain and hydrostatic tensile stress may stimulate intramembranous ossification; (3) poor vascularity can promote chondrogenesis in an otherwise osteogenic environment; (4) hydrostatic compressive stress is a stimulus for chondrogenesis; (5) high tensile strain is a stimulus for the net production of fibrous tissue; and (6) tensile strain with a superimposed hydrostatic compressive stress will stimulate the development of fibrocartilage. Finite element models are used to show that the patterns of tissue differentiation observed in fracture healing and distraction osteogenesis can be predicted from these fundamental mechanobiologic concepts. In areas of cartilage formation, subsequent endochondral ossification normally will proceed, but it can be inhibited by intermittent hydrostatic compressive stress and accelerated by octahedral shear stress (or strain). Later, bone remodeling at these sites can be expected to follow the same mechanobiologic adaptation rules as normal bone.

Adaptation, Physiological↗
PubMed2001

A comparison of the USDA ossification-based maturity system to a system based on dentition.

Two studies using commercially fed cattle were conducted to determine the relationship of the USDA bone ossification-based maturity system to one based on the number of permanent incisors present at slaughter. These studies showed that 91.5 to 100% of cattle with zero permanent incisors (< 23.8 mo of age), 89.1 to 97.5% of cattle with two permanent incisors (23.8 to 30.4 mo of age), 75 to 82.2% of cattle with four permanent incisors (30.4 to 38.0 mo of age), 64 to 72.5% of cattle with six permanent incisors (38.0 to 45.3 mo of age), and 40% of cattle with eight permanent incisors (> 45.3 mo of age) were graded as A maturity by the USDA maturity classification system. Kappa tests revealed no statistical relationship between the dentition- and skeletal ossification-based maturity systems. Dentition-based maturity agreed with ossification/lean maturity for only 162 of 1,264 carcasses in Exp. 1 and only 54 of 200 carcasses in Exp. 2. Cattle with two, four, six, or eight permanent incisors were classified in more youthful categories of USDA bone ossification/lean maturity than they should have been. Male cattle were more likely to be misclassified into a younger age category by the USDA system than were female cattle. It seems that determining physiological maturity by number of permanent incisors rather than by the current USDA method of subjectively evaluating skeletal and lean maturity may prove to be a more accurate technique of sorting beef carcasses into less-variable age groups.

Age Determination by Teeth↗
PubMed2002

Effects of nicotine on the healing of extraction sockets in rats. A histological study.

The aim of the present study was to evaluate, histologically, the influence of nicotine on the socket healing after tooth extraction in rats. Eighty animals were divided into 4 groups of 20 rats each (2 control and 2 test groups). In the first and second test groups, the animals received one dose of nicotine hemisulfate solution once or twice daily, respectively. In the control groups, the animals received sterile saline once or twice daily. All solutions were injected subcutaneously on the dorsum of the animals for 4 weeks. The results showed that nicotine delayed alveolar healing, especially in terms of organization of connective tissue and osteoneogenesis. Angiogenesis was considerably impaired in the ossification area and in the gingival tissues as well. We concluded that the impairment of the healing of extraction sockets was found to be directly related to the drug dosage.

Animals↗