[Bone development in angioma].
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A Danish anthropological collection of medieval human skeletons excavated in 1986 involves a mandible (No. 212) from an adult female born without the lower alveolar nerve and mandibular canal. It is believed that the defect has resulted in lack of tooth development on the affected side and that the mylohyoid nerve has partially compensated for this defect by development of teeth in localized areas. The defective mandibular dentition has caused a compensatory development of the alveolar process in the maxilla. The missing occlusal support has altered muscular traction on the mandible. This has caused an alteration in mandibular shape. Whether the asymmetric development of the mandible is caused by muscular dysfunction, by failure in angular growth apposition, or by a combination of these factors is discussed. The case presents valuable data in the ongoing discussion about the interaction between nerve tissue and tooth formation and about the interaction between occlusion, jaw morphology, and muscular traction. The study shows how archeological material in an interdisciplinary cooperation between archeological, embryological and orthodontic research can contribute to the clarification of current biological problems.
BACKGROUND: Understanding the determinants of adiposity in young children may be particularly critical for preventing adult obesity since the age at which body fatness reaches a postinfancy low point (typically 4-6 years) is inversely associated with obesity later in life. METHODS; We examined cross-sectional associations among fatness, leanness, and physical activity in 467 children (range 4-6 years). Activity was measured using accelerometry and parental report of children's television (TV) viewing. Dual energy X-ray absorptiometry was used to quantify body composition. RESULTS: Minutes spent in vigorous activity and TV viewing were the variables most consistently and most highly associated with adiposity. Children in the lowest quartile for vigorous activity had on average (absolute) body fat percentages that were 4% greater than those children in the highest quartile for vigorous activity. Body fat percentages for children in the highest category for TV viewing were on average 3% greater than those children who watched the least amount of TV. CONCLUSIONS: Low levels of vigorous physical activity and high levels of TV viewing are associated with fatness in young children during the adiposity rebound period. This suggests that increasing children's active play may be important in preventing obesity later in life.
Genetically modified mice and cells have provided important insights into the biological functions of the dimeric transcription factor complex AP1, in particular into its role in skeletal development. Data obtained from knockout mice revealed that some components, such as c-Fos are key regulators of bone cell differentiation, whereas others, like c-Jun, JunB and Fra-1 are essential in embryonic and/or postnatal development. Apart from identifying the specific roles of AP1 proteins in developmental processes, researchers are beginning to obtain a better molecular understanding of their cell-context dependent functions, their downstream target genes and how they regulate bone cell proliferation, differentiation, and apoptosis.
Large White male turkeys were fed rations containing 0, 12.5, 25, 50, 100, 200, 400, and 800 ppm added fluoride (F) from sodium fluoride in a corn-soybean assay diet containing tricalcium phosphate and 3 to 5 ppm F. The 800 ppm treatment was discontinued at 8 weeks because of low weight gains and a high incidence of leg disorders. Turkeys receiving defluorinated phosphate (32% calcium, 18% phosphorus) had significantly higher 4-week body weights than turkeys receiving tricalcium phosphate. Turkeys fed 0, 400, and 800 ppm F had significantly lower body weights at 8 weeks than turkeys fed 50 ppm F. A similar weight pattern was seen at 18 weeks, although the differences were not statistically significant. Based on growth response in this study, a requirement of 20 ppm F is proposed. Increasing levels of dietary F resulted in large increases in tibia F. Removal of high dietary F in certain groups at 8 weeks resulted in growth recovery and reduction in tibia F by 18 weeks. Elevated plasma alkaline phosphatase activity was observed with added dietary F of 400 and 800 ppm. At 4 weeks, tibiae from turkeys receiving high F had a trend (not statistically significant) toward lower percentage ash and a significantly lower breaking strength than controls. Compared to controls, tibiotarsi from turkeys on high F rations were significantly shorter, had thinner cortices, and had a narrower proliferative zone of proximal growth plates. A high incidence of tibial dyschondroplasia was observed, but it was not correlated with dietary treatment.
Target cells for 3H-labeled 1 alpha, 25(OH)2 vitamin D3 [1,25(OH)2D3, vitamin D] and its analog 3H-labeled 22-oxa-1 alpha, 25(OH)2 vitamin D3 (OCT) have been identified during endochondral and intramembranous ossification in developing, undecalcified, unembedded bone, using thaw-mount autoradiography. Two-day-old neonatal rats were injected with [3H]1,25(OH)2D3 or [3H]OCT; after 2 h leg, spine, and head were frozen and sectioned. In the epiphyseal-metaphyseal region specific nuclear concentrations of [3H]1,25(OH)2D3 and [3H]OCT were observed in identical cell populations, being low in cells of the articular and resting zone, intermediate in the proliferating zone, and highest in hypertrophic chondrocytes and in osteoblasts and precursor cells. In the primary spongiosa intertrabecular spaces there were a large number of cells with nuclear labeling--probably osteoblasts and precursor cells. In contrast, in the secondary spongiosa intertrabecular spaces, apparent blood-forming cells were mostly unlabeled. Osteoblasts along bone spicules and compact bone in long bones, vertebrae, and head also showed strong nuclear labeling, as did cells of the periosteum. These data suggest that 1,25(OH)2D3 and OCT regulate development, differentiation, and activities of chondrocytes and osteoblasts, including differentiation of resting chondrocytes into proliferating and hypertrophic chondrocytes that involve "chondroclastic" enlargement of lacunae and "trans-differentiation" of surviving hypertrophic chondrocytes; differentiation of stroma cells into osteoblasts; and in periosteum and other regions of intramembranous ossification differentiation of precursor cells and osteoblasts. Nuclear receptor binding and their selective and hierarchical distribution during cell differentiation appear to correspond to multiple genomic effects toward growth, regeneration and repair. The findings indicate a physiological significance and therapeutic potential of 1,25(OH)2D3 and in particular of its less hypercalcemic analog OCT.
Bone formation occurred ten days after transplantation of guinea-pig urinary bladder wall to the anterior abdominal wall. A quantitative analysis showed that the bone which formed in the tissues of the transplant site grew rapidly during the following week. Thereafter, bone growth slowed and remodelling became evident histologically. The bone continued to enlarge for up to six months but growth was mainly confined to an increase in thickness. Matrix vesicles were observed in the early bone formation, but later, when bone growth slowed, these structures could not be observed on the bone surfaces.
Development of the vertebrate skeleton is a highly complex process in which collagen type II plays a vital role in the formation of long bones via endochondral ossification. Collagen type II, which is encoded by a single COL2A1/ Col2a1 gene, is the most abundant structural protein in the cartilage matrix, where it undergoes complex interactions with several other proteins. The sequence of mature collagen type II chains, each with about 1,100 amino acids, is conserved between different mammalian species. There are 37 amino acid positions that are different between mouse and human collagen type II. Previously, we have demonstrated that transgenic mice, in which Col2a1 gene is knocked out, exhibit a lethal phenotype due to the absence of endochondral bone formation. To investigate whether the biological role of collagen type II is conserved between the species, human COL2A1 gene was expressed in Col2a1 null mice by crossing with transgenic mice in which human COL2A1 gene was integrated. The collagen type II from human gene rescued the lethal phenotype in null mice, indicating that the biological function of collagen type II is conserved between human and mouse. The animals exhibited normal endochondral bone formation and a normal growth plate in tibio-tarsal joint. Chondrocytes isolated from the cartilage of these mice secreted human protein, suggesting that the animals incorporated heterologous protein to form cartilage which is essentially "humanized." The animals reached puberty and produced normal progeny. A completely normal phenotype in newborns indicates that human COL2A1 gene is expressed properly both temporally and spatially. These animals may be useful to generate models to study the effect of COL2A1 mutations on skeletal development in humans by introducing mutated gene constructs either into embryos or by crossing with transgenic animals with COL2A1 mutations.
Bone development requires the recruitment of osteoclast precursors from surrounding mesenchyme, thereby allowing the key events of bone growth such as marrow cavity formation, capillary invasion, and matrix remodeling. We demonstrate that mice deficient in gelatinase B/matrix metalloproteinase (MMP)-9 exhibit a delay in osteoclast recruitment. Histological analysis and specialized invasion and bone resorption models show that MMP-9 is specifically required for the invasion of osteoclasts and endothelial cells into the discontinuously mineralized hypertrophic cartilage that fills the core of the diaphysis. However, MMPs other than MMP-9 are required for the passage of the cells through unmineralized type I collagen of the nascent bone collar, and play a role in resorption of mineralized matrix. MMP-9 stimulates the solubilization of unmineralized cartilage by MMP-13, a collagenase highly expressed in hypertrophic cartilage before osteoclast invasion. Hypertrophic cartilage also expresses vascular endothelial growth factor (VEGF), which binds to extracellular matrix and is made bioavailable by MMP-9 (Bergers, G., R. Brekken, G. McMahon, T.H. Vu, T. Itoh, K. Tamaki, K. Tanzawa, P. Thorpe, S. Itohara, Z. Werb, and D. Hanahan. 2000. Nat. Cell Biol. 2:737-744). We show that VEGF is a chemoattractant for osteoclasts. Moreover, invasion of osteoclasts into the hypertrophic cartilage requires VEGF because it is inhibited by blocking VEGF function. These observations identify specific actions of MMP-9 and VEGF that are critical for early bone development.
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Accumulation and cell death of neutrophils were studied by light and electron microscopy in neonatal mouse bone marrow. At the beginning of bone marrow hematopoiesis, the marrow cavity contained a large number of polymorphonuclear leukocytes. Polymorphs comprised approximately 75% of the total nucleated cells in the hematopoietic compartment of the newborn marrow, the majority being neutrophils. Mature neutrophils were sometimes crossing the endothelium of the marrow blood sinus. Neutrophils in neonatal marrow show features typical of apoptosis, e.g. formation of nuclear pockets and blebs, margination of compact nuclear chromatin to form sharply circumscribed masses, condensation of cytoplasm, and convolution of cell outlines. Dying neutrophils were devoured and digested by phagocytes. The occurrence of large-scale neutrophil death and removal of neutrophils by phagocytes in neonatal bone marrow are discussed in relation to programmed cell death in development of the fetal hematopoietic system.
In vitro observations suggest that inorganic phosphate (Pi) transport plays an important functional role in osteogenic cells and in their matrix vesicles for the initiation of matrix calcification. Recent studies have shown that the type III sodium-dependent Pi transporters, Glvr-1 and Glvr-2, are expressed in human osteoblast-like cells and have suggested a potential role for type III transporters in regulated Pi handling in osteogenic cells. To address the relevance of these findings in the context of bone formation in vivo and, in particular, in relation to matrix calcification, we investigated expression of the Glvr-1 transporter by in situ hybridization in developing embryonic murine metatarsals, using human Glvr-1 cDNA as a probe. In this model of endochondral ossification, expression of transcripts encoding Glvr-1 could be detected from day 17 of embryonic development. A hybridization signal for Glvr-1 was specifically observed in a subset of hypertrophic chondrocytes and could not be detected in osteoblasts. The expression of Glvr-1 mRNA was compared with that of transcripts encoding extracellular matrix proteins. Glvr-1 mRNA expression was confined to a population of early hypertrophic chondrocytes expressing type X collagen and to slightly more mature cells that express transcripts encoding osteopontin but lack type X collagen mRNA. No Glvr-1 transcripts were detected in fully differentiated hypertrophic chondrocytes. This pattern of Glvr-1 mRNA expression was maintained throughout embryonic development until after birth. In conclusion, the Glvr-1 phosphate transporter is selectively expressed in a subset of hypertrophic chondrocytes during endochondral bone formation, in a region where matrix mineralization proceeds. This observation represents the first in vivo evidence consistent with a potential role for this phosphate transporter in matrix calcification.
Basic helix-loop-helix (bHLH) transcription factors are implicated in cell lineage determination and differentiation. Dermo-1 encodes a bHLH transcription factor that shares extensive homology with another bHLH transcription factor, Twist. We have cloned and characterized human Dermo-1 from two different bone cytoplasmic DNA (cDNA) libraries. Dermo-1 mRNA and protein expression were examined in human embryo and adult tissue sections. Dermo-1 is expressed in a subset of mesodermally and ectodermally derived tissues. We further examined expression of Dermo-1/Twist in human tissues and cell lines. In addition, we observed Dermo-1 expression in response to basic fibroblast growth factor in osteoblastic cell lines. To evaluate the functionality of the human Dermo-1 transcription factor in osteoblast metabolism, we made stable osteoblastic cell lines that over- and underexpress human Dermo-1. These cell lines were analyzed and compared with previously published data of similar cell lines transfected with Twist. Our results demonstrate that Dermo-1 caused changes similar to Twist in the osteogenic properties of osteoblastic cells, such as morphology, bone marker gene expression, and biochemical response to cytokines. However, Dermo-1 expression also has unique effects in regulating the mechanism of proliferation, on alkaline phosphatase enzyme activity, and in temporal expression patterns. We speculate that expression of Twist and Dermo-1 maintains cells in an osteoprogenitor or preosteoblast-like state, respectively, and prevents premature or ectopic osteoblast differentiation. Therefore, Twist and Dermo-1 must be sequentially downregulated in order to initiate the cascade of events responsible for osteogenic cell differentiation. These results indicate that, during osteoblast development, Dermo-1 may inhibit osteoblast maturation and maintain cells in a preosteoblast phenotype by utilizing mechanisms similar but not identical to those utilized by Twist.
PURPOSE AND METHODS: In order to provide material for genetic analysis of fibrous dysplasia (FD), a cell line designated GBS-1 was established from a secondary bone malignant fibrous histiocytoma (MFH) developing in a rib of a 44-year-old male polyostotic FD patient. RESULTS: The GBS-1 cells are characterized by a pleomorphic spindle cell morphology with abundant mucus production. On transplantation to nude mouse subcutis the cell line forms myxoid-spindle cell sarcomas with giant cells, the myxoid product being positive for periodic acid-Schiff (PAS) and alcian blue (Al-B) stains and completely digested by hyaluronidase, mimicking the original tumor. Chromosome and genetic analyses revealed multiple structural and numerical abnormalities of chromosomes with a large number of unidentifiable chromosomes and p53 mutation in exon 7 with LOH in the counterpart. CONCLUSIONS: Since cell lines for FD have hitherto not been available, the GBS-1 cells should prove useful for genetic analyses of FD and also MFH of bone origin.
The calciotropic hormone 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] has been established to control skeletal tissue formation and biomineralization via the regulation of gene expression. This action involves the well-characterized nuclear 1,25(OH)2D3 receptor. However, it has been recognized that several cellular responses to 1,25(OH)2D3 may not to be related to the exclusive nuclear receptor. Indeed, this secosteroid is able to generate rapid responses that have been proposed to be mediated by interactions of the ligand, which is a putative cell membrane-associated rapid-response steroid (MARRS) binding protein for 1,25(OH)2D3 [1,25D3-MARRS]. The nongenomic pathway of 1,25(OH)2D3 was studied here in detail by immunolocalization of the 1,25D3-MARRS during the specific context of human prenatal development. Western blotting with proteins extracted from 4 week- to 27-week-old embryos was performed, evidencing a 65-kDa molecular species recognized by antibody Ab 099 generated against synthetic peptides corresponding to the N terminus of the 1,25D3-MARRS from chick intestinal basolateral membranes. Based on this biochemical conservation of protein in the human species, the temporospatial expression patterns were established in the craniofacial skeleton at the same ages. Comparative analysis was performed in teeth and bones from early morphogenesis to terminal cell differentiation and extracellular biomineralization. The data show the potential implication of 1,25D3-MARRS in the heterogeneous cell population including ameloblasts, odontoblasts, osteoblasts, and osteoclasts. The epithelial-mesenchymal cascade related to odontogenesis was coincident with a sequence of up- and down-regulation of immunoreactive 1,25D3-MARRS. Biomineralization was associated with a striking up-regulation in the adjoining secretory cells in all tissues. Finally, osteoclasts appeared also to express the 1,25D3-MARRS during these early phases of bone modeling. Previously obtained data of the nuclear vitamin D receptor (VDR) expression and this study on 1,25D3-MARRS suggest the existence of cross-talk between the genomic and nongenomic pathways during human development.
In this paper we present a new instrument for measurements on long bones. The instrument is based on the use of a digital coordinatometer-goniometer connected to an optical collimator: such device allows angles as well as lengths to be measured. With regard to observing procedures, an innovative method for bone axis location by points has been applied. It is also possible to locate an axis using a symmetry and tangency criterion. As for torsion angles, the proposed technique is absolutely new; it utilizes a reference plane, which the bone must be leaned against, and the symmetry conditions that are generated by rotating the bone around an axis orthogonal to this plane. In order to verify the precision of the new instrument (digital osteogoniometer), several tests were performed. For this purpose we have studied the results of measurements carried out with the new instrument as well as with traditional apparatuses by four different observers on a sample of 10 skeletons (humerus, radius, ulna, femur, tibia of left side). The analysis of intrapersonal and interpersonal differences points out that the new osteogoniometer is more precise in angular measurements than traditional instruments. Moreover the time requested for carrying out measurements prooved to be shorter, above all with regard to torsion angles measurements.
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The galectins are a family of low molecular weight, calcium-independent mammalian carbohydrate binding proteins that exhibit specificity for beta-galactoside derivatives. We have examined the expression pattern of galectin-3 in the developing mouse embryo by in situ hybridisation and immunohistochemistry. In the embryo proper, galectin-3 message and protein are first detected in notochord, starting from 8.5 days post coitum (dpc), and persist until this structure disappears. Galectin-3 is later found in cartilage primordia and in developing skin from 13.5 dpc. This very restricted and dynamic pattern suggests that galectin-3 may participate in the establishment and/or maintenance of notochord as well as the formation of cartilage and differentiation of skin. Finally, we find that galectin-3, which is identical to the macrophage marker Mac-2, is also expressed in embryonic macrophages.