Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.1 (alkaline phosphatase)
 47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of cortisol on bone formation are complex and may be modulated by the presence of periosteal cells or by factors released by the periosteal tissue. To test these possibilities, cortisol was examined for its effects on the incorporation of 3H-proline into collagenase-digestible protein (CDP) and noncollagen protein (NCP), on DNA synthesis and on alkaline phosphatase activity in intact and in the periosteum and nonperiosteal bone of dissected calvariae from 21-day-old fetal rats. After 24 h of treatment, cortisol increased the incorporation of 3H-proline into CDP in intact bones and in the nonperiosteal bone of calvariae dissected after the culture. Cortisol inhibited the incorporation of 3H-thymidine into calvarial DNA but it caused a small increase in nonperiosteal DNA content. Cortisol did not affect the incorporation of 3H-proline into CDP in calvariae dissected prior to the culture if the periosteum and nonperiosteal central bone were incubated separately; the stimulatory effect was observed only if the two tissues were cultured in the same vial and were in contact. In contrast, cortisol stimulated alkaline phosphatase activity in the central nonperiosteal bone of calvariae dissected before or after the culture. After 72-96 h of treatment, cortisol inhibited the labeling of CDP, NCP, and DNA and the DNA content in intact bones and in both periosteal and nonperiosteal central bone of calvariae dissected after the culture. In contrast, when the periosteum was removed before the incubation, these inhibitory effects were observed in the periosteum and not in the nonperiosteal bone.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of cortisol on periosteal and nonperiosteal collagen and DNA synthesis in cultured rat calvariae. 643 Apr 99

Tissue culture techniques were used to study a number of factors and mechanisms which are important in the development and metabolism of bone tissue. As an example of an external factor influencing bone development, the importance of the composition of the gasphase which is in equilibrium with the fluid bathing osteoblasts and hypertrophic chondrocytes, was investigated in cultured metatarsal bone rudiments. In vivo, one expects the presence of an O2 gradient in the cartilaginous epiphyses of long bones: low O2 tension between the nonhypertrophic chondrocytes, high O2 tension in periosteum and hypertrophic zone, bordering the marrow cavity. The in vitro findings correlated with these expectations. High CO2 (5%) and high O2 (40%) tensions stimulated calcification; in air, calcification was severely inhibited. On the other hand, maturing chondrocytes were damaged by high O2 tensions. An important cellular mechanism in calcification is the intracellular accumulation of calcium (and phosphate) in osteoblasts and hypertrophic chondrocytes which can be demonstrated with the GBHA stain of Kashiwa [9]. The extracellular role of alkaline phosphatase (AP) present on the cell membranes of these cells was shown to be a less decisive factor in calcification. In the presence of AP inhibitor in a concentration high enough to inhibit AP activity to a large extent, calcification was shown to proceed normally. The effects of a number of hormones known to be important for the development and metabolism of bone tissue was studied using tissue culture (calvaria) as well as culture of different isolated bone cells. The parathyroid hormone (PTH) induced rise of the intracellular cAMP level was found to originate primarily from the osteoblasts not the osteoclasts. Isolated osteoblasts showed a high cAMP response after PTH addition. Cortisol was shown to inhibit PTH induced resorption but to potentiate PTH induced cAMP response in calvaria. Various PTH fragments (desamino 1-34, 2-34, 3-34) were shown to be active as stimulators of bone resorption (although they were less active in this respect than the intact molecule 1-84), but did not stimulate cAMP production in calvaria or isolated osteoblasts. The results obtained strengthened the hypothesis that cAMP is not the (only) mediator in PTH induced bone resorption.
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PMID:Regulatory mechanisms in the development of bone and cartilage: the use of tissue culture techniques in the study of the development of embryonic bone and cartilage: a perspective. 715 53

Investigations were carried out with homogenates from the organs of hens (liver, duodenum, pancreas, spleen, kidney, glandular and muscular stomach, ovary resp. testicle, periosteum,) as well as serums in which the general activity of the alkaline phosphatase was determined and parallel to this after an inhibition in the presence of 10 mM 1-phenylalanine or different concentrations (0.25--4 M) or urea, as well as with values of pH ranging from 9.0 up to 11.0, after a preincubation of urea for 10, 20 and 30 min with 3 M/l of after heating up to 56 degrees C for 10, 20 and 30 min. An electrophoresis of an agar gel was also carried out. Some stereospecific peculiarities of the alkaline phosphatase isoenzymes of the organs studied was found with regard to the inhibitors used. The selective inhibition, as well as the electrophoretic division of enzymes, did not produce any considerable differences, which can be used for practical ends.
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PMID:[Alkaline phosphatase activity and properties of the blood serum and organs of hens]. 723 24

Estrogen deficiency is well recognized as a cause of bone loss in rats and humans. Likewise, treatment with estrogen results in prevention of this loss. Initially, this effect was thought to be indirectly mediated but, more recently, estrogen receptors (ER) have been reported in osteosarcoma cells and primary cultures originating from surgical waste, suggesting a direct effect of this steroid hormone. Detection of ER in skeletal tissues, however, has remained elusive. The purpose of this investigation was to establish the efficacy of the highly sensitive reverse-transcription polymerase chain reaction (RT-PCR) technique to detect ER in a well defined skeletal tissue (calvarial periosteum) that is responsive to the hormone. Primers were made specific to rat ER sequences. Total RNA was extracted from rat uterus, liver, spleen, and the periosteum using an organic solvent method. cDNA was synthesized from 2 micrograms total RNA. cDNA corresponding to 40 ng total RNA/sample produced intense PCR products for ER. In descending order of intensity were uterus, liver, bone, and spleen. Importantly, a similar time-course for estrogen-induced down-regulation of steady-state mRNA levels for alkaline phosphatase and osteonectin was observed in calvarial periosteum and tissues known to express estrogen receptors. These data provide in vivo evidence of ER mRNA in bone and suggest that at least some of estrogen's action on bone is directly modulated.
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PMID:Estrogen receptor mRNA is expressed in vivo in rat calvarial periosteum. 748 34

We studied the effects of transforming growth factor-beta and basic fibroblast growth factor on the regulation of proliferation and osteochondrogenic differentiation of periosteum-derived cells, which have the potential to differentiate into bone and hypertrophic cartilage in vitro. Histological observation revealed that transforming growth factor-beta stimulated chondrogenesis of periosteum-derived cells while basic fibroblast growth factor stimulated proliferation of fibroblast-like cells and inhibited osteochondrogenic differentiation. Immunohistochemical studies revealed that basic fibroblast growth factor inhibited the expression of osteocalcin. Transforming growth factor-beta enhanced uronic acid content but decreased DNA content, alkaline phosphatase activity, and calcium content. In contrast, basic fibroblast growth factor enhanced DNA content but decreased alkaline phosphatase activity, calcium content, and uronic acid content. In addition, transforming growth factor-beta shortened the time-course of gene expression of type-X collagen whereas basic fibroblast growth factor inhibited the gene expression. These results indicate that transforming growth factor-beta stimulates osteochondrogenic differentiation of periosteum-derived cells but inhibits proliferation. They also indicate that basic fibroblast growth factor stimulates proliferation of periosteum-derived cells but inhibits osteochondrogenic differentiation.
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PMID:Regulation of proliferation and osteochondrogenic differentiation of periosteum-derived cells by transforming growth factor-beta and basic fibroblast growth factor. 771 71

Insulin-like growth factors (IGFs) are among the most abundant growth factors present in bone. In vitro, bone-derived cells both produce and respond to IGFs I and II, suggesting that these growth factors play an autocrine role in the regulation of bone turnover. In vivo, however, particularly in adult bone, their sites of expression have not been well documented. We have used, therefore, the technique of in situ hybridization to study the expression of the mRNAs for IGFs I and II and the type 1 IGF receptor in adult human osteophyte tissue. Throughout the developing osteophyte there was a strong association between osteogenesis and the expression of all three mRNA transcripts. The highest levels of expression were observed in active osteoblasts. Hybridization signals were weak or absent in flat cells lining quiescent surfaces and in cells of the bone marrow, including those that expressed alkaline phosphatase activity. Osteocytes and cells of the periosteum were negative. At sites of endochondral bone formation newly differentiated and hypertrophic chondrocytes expressed the mRNAs for IGFs and IGF receptor whereas cells of the perichondrium were negative. A striking finding of this investigation was that osteoclasts at sites of bone and calcified cartilage resorption expressed high levels of all three mRNA transcripts. These results support the hypothesis that locally produced IGFs are important regulators of bone formation. The differential expression of all three transcripts among cells of the osteoblast lineage suggests that IGFs may be involved in the maintenance of the mature osteoblast phenotype rather than in inducing the differentiation of marrow precursors or controlling the osteoblast-osteocyte transition.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Osteoblasts and osteoclasts in adult human osteophyte tissue express the mRNAs for insulin-like growth factors I and II and the type 1 IGF receptor. 778 31

Tetranectin is a protein shared by the blood and the extracellular matrix. Tetranectin is composed of four identical, noncovalently bound polypeptides each with a molecular mass of approximately 21 kD. There is some evidence that tetranectin may be involved in fibrinolysis and proteolysis during tissue remodeling, but its precise biological function is not known. Tetranectin is enriched in the cartilage of the shark, but the gene expression pattern in the mammalian skeletal system has not been determined. In the present study we have examined the expression pattern and putative function of tetranectin during osteogenesis. In the newborn mouse, strong tetranectin immunoreactivity was found in the newly formed woven bone around the cartilage anlage in the future bone marrow and along the periosteum forming the cortex. No tetranectin immunoreactivity was found in the proliferating and hypertrophic cartilage or in the surrounding skeletal muscle. Using an in vitro mineralizing system, we examined osteoblastic cells at different times during their growth and differentiation. Tetranectin mRNA appeared in the cultured osteoblastic cells in parallel with mineralization, in a pattern similar to that of bone sialoprotein, which is regarded as one of the late bone differentiation markers. To explore the putative biological role of tetranectin in osteogenesis we established stably transfected cell lines (PC12-tet) overexpressing recombinant tetranectin as evidenced by Northern and Western blot analysis and immunoprecipitation. Both control PC12 cells and PC12-tet cells injected into nude mice produced tumors containing bone material, as evidenced by von Kossa staining for calcium and immunostaining with bone sialoprotein and alkaline phosphatase antiserum. Nude mice tumors established from PC12-tet cells contained approximately fivefold more bone material than those produced by the untransfected PC12 cell line or by the PC12 cells transfected with the expression vector with no insert (Mann Whitney rank sum test, p < 0.01), supporting the notion that tetranectin may play an important direct and/or indirect role during osteogenesis. In conclusion, we have established a potential role for tetranectin as a bone matrix protein expressed in time and space coincident with mineralization in vivo and in vitro.
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PMID:A potential role for tetranectin in mineralization during osteogenesis. 779 25

Although the osteocyte is the most abundant among the highly differentiated cells of mature bone (osteocytes, lining cells, osteoblasts, and osteoclasts), its properties and functions are the least known and understood. Here we isolated osteocytes from mixed populations of bone cells liberated from fetal chick calvariae by alternate treatments with collagenase and EDTA. The osteocytes were removed from the bone cell populations by binding them via an osteocyte-specific antibody (MAb OB 7.3) to magnetic beads and removing the beads together with the coupled osteocytes from the population using a magnet. Isolated osteocytes were found to be highly differentiated, postmitotic cells that required their typical stellate morphology in culture. Osteocyte populations had alkaline phosphatase (ALP) activity somewhat lower than that of the osteoblast-like cell populations from which they were separated by the immunodissection procedure. On the single-cell level, the ALP activity was highly variable. Parathyroid hormone (PTH) receptors were found to be present on osteocytes as well as on osteoblast-like cells, but not on fibroblast-like cells of the outer periosteum. In response to PTH, osteocytes increased their intracellular levels of cAMP, as did the osteoblast-like cells. Osteocytes appeared to be somewhat more sensitive to PTH than osteoblasts. When seeded onto dentin slices, osteocytes did not corrode the dentin surface to any appraisable degree. We therefore found no evidence to support the notion that osteocytes play a role in the calcium homeostasis through osteocytic osteolysis. Whether osteocytes play an important role in perceiving and transducing hormonal and/or mechanical stimuli remains open for future research.
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PMID:Characteristics and properties of osteocytes in culture. 786 20

The ultrastructure of the reversal line during alveolar bone remodelling was investigated in the rat. Surface bone remodelling along the periosteum of the mandible was induced by the extraction of opposing maxillary molars. With transmission EM the reversal line was seen to be composed of a superficial electron-dense amorphous layer and a deep filamentous layer at 7 d after extraction. The reversal line exhibited strong alkaline phosphatase activity and contained acid mucopolysaccharide. Scanning EM of the surface of the line, exposed by sonication in distilled water, showed papillary structures, the surface of which appeared granular and exhibited a crystalline appearance. The tips of collagen fibrils of new bone were attached to the top of the papillae in the front area of bone formation. It is suggested that the reversal line is involved in the coupling of bone resorption and formation.
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PMID:Structural aspects of the reversal phase of alveolar bone remodelling. 792 48

Fibroblasts of the periodontal ligament, by their alkaline phosphatase (ALP) activity, are considered to play a role in the formation of acellular cementum. As a means of exploring this hypothesis, periodontal ligament explants from rat incisors were cultured in direct contact with bovine dentin slices in the presence of 10 mmol/L beta-glycerophosphate. Periosteal and pericardial tissue explants were maintained under similar conditions. After two weeks, the slices were harvested and processed for electron microscopic examination. Controls included periodontal ligament explants to which the ALP-inhibitor levamisole was added. The results suggest that only ALP-positive cultures from periodontal ligament and periosteum form mineralized layers along the dentin. After demineralization, layers consisted of fine filamentous or granular material of moderate electron-density and resembled afibrillar acellular cementum. Our findings support the hypothesis that periodontal ligament fibroblasts, by means of their ALP activity, play a pivotal role in the formation of acellular cementum.
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PMID:Formation of afibrillar acellular cementum-like layers induced by alkaline phosphatase activity from periodontal ligament explants maintained in vitro. 792 72


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