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At least 883 records · Page 49Linked to original sources
PubMed2000

Integrin-mediated signaling regulates AP-1 transcription factors and proliferation in osteoblasts.

Since osteoblast proliferation is critical for bone development, the effect of bone extracellular matrix (ECM) proteins on osteoblast signaling and proliferation in serum-free medium was investigated. Proliferation was highest in primary rat calvarial osteoblasts cells grown on fibronectin but less on type I collagen; osteonectin and poly-L-lysine did not support early proliferation. Fibronectin and type I collagen binding requires integrins, whereas cell adhesion to osteonectin or poly-L-lysine does not involve integrins. Therefore, the role of integrins in osteoblast signaling, leading to the induction of AP-1 transcription factors (c-fos and c-jun) which are important in cell proliferation, was studied. c-fos and c-jun message levels were increased at 60 min in osteoblasts plated onto fibronectin or collagen, but not in cells on osteonectin or poly-L-lysine. Protein synthesis was not required for c-fos mRNA expression; however, kinase activity was necessary for c-fos induction. In cells plated onto fibronectin, c-fos mRNA levels were controlled by protein kinase C and phosphotyrosine kinase signaling pathways. In contrast, c-fos levels in collagen-adhering cells may involve protein kinase A. The signaling pathway involving the phosphorylation of focal adhesion kinase and mitogen-activated kinases was also shown to be transiently increased in osteoblasts on fibronectin and type I collagen, but not in cells on poly-L-lysine. These results demonstrate that osteoblast binding to the extracellular matrix through integrins induces c-fos and c-jun, and that both fibronectin and collagen affect these AP-1 transcription factors through protein kinase-sensitive pathways. Thus, osteoblast proliferation is modulated differentially by specific ECM components.

Animals↗
PubMed1994

Tartrate-resistant acid phosphatase accumulated in the matrix of developing medullary bone induced by estrogen treatment of male Japanese quail.

Tartrate-resistant acid phosphatase (TRAP) in medullary bone matrix and bone cells was histochemically examined employing estrogen-induced medullary bone of male Japanese quail. Within 2 days after estrogen administration, medullary bone matrix was identified and the matrix and osteoblasts were negative for TRAP activity. Osteoclasts showing TRAP activity were occasionally seen. By 4 days, the projection of medullary bone trabeculae was seen and TRAP became positive in the deeper part of the bone matrix of trabeculae as well as the matrix located near cortical bone, but the surface areas and extending margins of medullary bone trabeculae were negative in activity. Osteoblasts were also negative for TRAP activity. By 7 days, TRAP-positive bone matrix conspicuously increased accompanying increment of bone volume, but TRAP-negative bone matrix was still seen at the surface areas or extending areas of the medullary bone trabeculae. Osteoblasts showed no reaction product. Osteoclasts showing TRAP activity increased in number. The results demonstrate that TRAP accumulates in medullary bone matrix with bone formation. Circumstantial evidence suggests that medullary bone osteoblasts may be involved in TRAP accumulation in the matrix despite their negative activity.

Acid Phosphatase↗
PubMed1976

[Constitutional familial leucocytopenia with partial Pelger anomaly and delayed development of bone (author's transl)].

The clinical and hematological findings in 4 boys of a family with a chronic constitutional leukocytopenia are described. Possible X-chromosomal sex-linked genetic transmission, the benign clinical course as well as the association with clinical and cytological hints of the involvement of the lymphatic cellular immunological system suggest a disease of its own. It was classified as a mild form of myelolymphatic insufficiency similar to reticular dysgenesis. The significance of Pelger-Huët anomalies of neutrophils demonstrated in the blood of the mother and of Pelger-like forms in the blood of children are discussed.

Adult↗
PubMed1994

Peak bone mass.

Peak bone mass, which can be defined as the amount of bony tissue present at the end of the skeletal maturation, is an important determinant of osteoporotic fracture risk. Measurement of bone mass development. The bone mass of a given part of the skeleton is directly dependent upon both its volume or size and the density of the mineralized tissue contained within the periosteal envelope. The techniques of single-1 and dural-energy photon or X-ray absorptiometry measure the so-called 'areal' or 'surface' bone mineral density (BMD), a variable which has been shown to be directly related to bone strength. Bone mass gain during puberty. During puberty the gender difference in bone mass becomes expressed. This difference appears to be essentially due to a more prolonged bone maturation period in males than in females, with a larger increase in bone size and cortical thickness. Puberty affects bone size much more than the volumetric mineral density. There is no significant sex difference in the volumetric trabecular density at the end of pubertal maturation. During puberty, the accumulation rate in areal BMD at both the lumbar spine and femoral neck levels increases to four- to sixfold over a 3- and 4-year period in females and males, respectively. Change in bone mass accumulation rate is less marked in long bone diaphyses. There is an asynchrony between the gain in statural height and bone mass growth. This phenomenon may be responsible for the occurrence of a transient period of a relative increase in bone fragility that may account for the pattern of fracture incidence during adolescence.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1990

The effect of strain on bone cell prostaglandin E2 release: a new experimental method.

A new method of investigating the mechanisms of strain-induced bone remodeling has been developed. Bone cells were subjected to cyclical strains in vitro by computer-controlled stretching of the plastic substrate on which they were cultured, enabling both physiological and pathological strains to be investigated. Physiological strains have not previously been investigated in vitro. The prostaglandin E2 (PGE2) released by the cells was found to depend on the strain magnitude. It was independent of cycle time, and 5 hours after straining had ceased, it had returned to control levels. These results are similar to the in vivo findings that bone remodeling is dependent on strain magnitude and not strain frequency, indicating that PGE2 may play an important role in strain-induced bone remodeling. The relationship between PGE2 release and strain magnitude was biphasic, with particularly high levels being released at strains that would be associated with either abnormally strenuous activity or microstructural bone damage. It is therefore possible that PGE2 stimulates the osteogenesis caused by increased functional demands, and initiates the remodeling caused by bone damage. This new method of investigating strain-induced remodeling is useful, as any cell type, any mediator, and any strain pattern or parameter can be individually studied.

Alkaline Phosphatase↗
PubMed2002

[New PMMA bone cements for vacuum mixing systems].

In cemented total hip replacement, fractures and cracks in the cement mantle may facilitate mechanical loosening of the prosthesis. Especially large voids and flaws within the cement can cause fatigue fractures. Reduction of cement porosity is a logical step in the attempt to improve the quality and durability of bone cement. An effective reduction of pores during vacuum mixing requires prechilling of Palacos R at 4 degrees C. For easier handling, new bone cements have been developed with characteristics similar to Palacos R, but with no chilling necessary prior to mixing under vacuum. In our study two newly developed bone cements (Palamed G, VersaBond) and a bone cement used widely in clinics (Palacos R) were mixed in three different vacuum mixing systems (Optivac, MixOR, Palamix). Macro-, micro-, and total porosity and bending strength (ISO 5833) were determined. All three mixing systems proved effective in reducing porosity and showed constant mixing results. All cement specimens that we tested fulfilled the ISO requirements for bending strength. VersaBond yielded the lowest porosities, but showed lower viscosity compared to Palacos R and Palamed G. The new cements are equal in vitro to Palacos R with regard to bending strength, but further clinical studies are necessary before widespread use is advisable.

Arthroplasty, Replacement, Hip↗
PubMed2003

The development of bone metastases as the first sign of metastatic spread in patients with primary solid tumours.

The purpose of this retrospective study was to investigate the incidence of bone metastases as the first sign of metastatic spread in patients with primary solid malignant tumours. Between January 1987 and December 1998, we treated 867 patients suffering from primary solid malignant tumours. Their average age was 67 (range: 30-96) years and all were thoroughly investigated with a complete physical examination and laboratory tests as well as imaging studies and bone scans. No bone metastases were found at the time of the initial diagnosis, and the patients were then re-assessed every 6 months for the first 5 years and then once a year. We found that, regardless of treatment, bone metastases appeared in a certain number of patients and that after excluding patients with prostate cancer a bone metastasis was the first sign of "recurrence" in 1.3% of the patients with a known primary solid malignant tumour.

Adult↗
PubMed1993

Restricted usage of T-cell receptor V alpha sequence and variable-joining pairs after normal T-cell development and bone marrow transplantation.

TCR V alpha 3 and V alpha 5 transcripts in PBLs from healthy individuals of multiple age groups and from BMT recipients were analyzed. PCR, cloning, and sequencing studies revealed significant V-J junctional diversity among TCR transcripts from all tested blood samples, as provided both by N/P-region addition and exonuclease activity. However, results illustrated restrictions in TCR alpha diversity at several additional levels. First, V alpha 5 and V alpha 3 gene families, which were expected to be composed of multiple members, were dominated in each case by a single sequence at the transcript level. Second, restrictions existed in V-J pairing in that J alpha genes, which were encoded toward the 5' region of the locus, were rearranged frequently with V alpha 3 and rarely with V alpha 5. Conversely, J alpha genes encoded toward the 3' region of the locus preferentially rearranged with V alpha 5. Healthy individuals showed few differences with regard to V-J pairing patterns, while one of three BMT recipients demonstrated a skewed usage of 3' J alpha genes. In total, results demonstrated qualitative restrictions that may limit the working TCR repertoire in human peripheral tissues, both among BMT recipients and their healthy donors.

Adolescent↗
PubMed1989

Distribution of expression of 2AR (osteopontin) in the embryonic mouse inner ear revealed by in situ hybridisation.

Using in situ hybridisation we have determined the distribution of expression of 2ar (also known as osteopontin, bone sialoprotein 1 or 44-kDa bone phosphoprotein) in the developing mouse inner ear. We have identified several discrete sites, both osteogenic and non-osteogenic, that express 2ar from embryonic day 16.5 (E16.5). In addition to the regions of developing bone of the calvaria and temporal bone, we have found 2ar expression in the epithelium of the sensory maculae (but not in the organ of Corti), in the vestibular and auditory ganglia and nerves (but not in the nerves that innervate the whiskers in the snout), in the epithelium that lines the endolymphatic sac (but not in the neighbouring and contiguous endolymphatic duct) and also in the epithelium that lines the semicircular canals. We found also individual cells scattered throughout the brain, loose mesenchyme and blood vessels of the head that were expressing 2ar. Several of the sites in the inner ear, for example the maculae and the endolymphatic sac, are known to be involved in the production of calcified matrix. The results extend the range of tissue types known to express the protein and demonstrate that tissues of histologically similar appearance can nonetheless differ in their gene expression.

Animals↗