Bone cell response

The principal cells in bone are the osteoclasts and osteoblasts. Osteoclasts, the cells responsible for resorption of bone, are derived from hematopoietic stem cells. Osteoblasts are derived from local mesenchymal cells. They are the pivotal bone cell, responsible for bone formation. Skeletal tissues are remodelled throughout a lifetime, alternating resorption phases by osteoclasts with periods of intense collagen synthesis. This balance is under the control of mechanical and hormonal stimuli, which ensure the appropriate performance of the bone. Skeletal tissues have three... 

Peck, W. A., Carpenter, J., Messinger, K., De Bra, D. Cyclic 3 ,5 -adenosine monophosphate in isolated bone cells Response to low concentrations of parathyroid hormone. Endocrinology 92, 692 (1973)... 

Brighton, C.T., Okerehe, E., Pollack, S., et al. (1992) In vitro bone-cell response to a capacitively coupled electrical field. Role of field strength, pulse pattern and duty cycle. Clinical Orthopedics and Related Research 285 255-262... 

Significant studies prove the interest in this kind of membrane. Among them we mention the work of Lambricht and Schubert [17] on emulsification with microchannels, and the study of Popat et al. [18] that proves that the bone cell response can be significantly improved using controlled nanoarchitecture (alumina membranes fabricated using a two-step anodization process and which present pore sizes of 30-80 nm). 

The effects of substrate characteristics on bone cell response to the mechanical environment... 

The effect of substrate characteristics on primary human bone cell response to mechanical loading was investigated in this study. The substrates comprised organic and... 

Alves, C M., Yang, Y., Carnes, D.L, Ong, J.L., Sylvia, V.L., Dean, D.D., Agrawal, C.M., and Reis, R.L. (2007) Modulating bone cells response onto starch-based biomaterials by surface plasma treatment and protein adsorption. J. Biomater., 28 (2), 307 315. 

Hydroxy vitamin D pools ia the blood and is transported on DBF to the kidney, where further hydroxylation takes place at C-1 or C-24 ia response to calcium levels. l-Hydroxylation occurs primarily ia the kidney mitochondria and is cataly2ed by a mixed-function monooxygenase with a specific cytochrome P-450 (52,179,180). 1 a- and 24-Hydroxylation of 25-hydroxycholecalciferol has also been shown to take place ia the placenta of pregnant mammals and ia bone cells, as well as ia the epidermis. Low phosphate levels also stimulate 1,25-dihydtoxycholecalciferol production, which ia turn stimulates intestinal calcium as well as phosphoms absorption. It also mobilizes these minerals from bone and decreases their kidney excretion. Together with PTH, calcitriol also stimulates renal reabsorption of the calcium and phosphoms by the proximal tubules (51,141,181—183). 

Osteoblasts are the primary cells responsible for bone formation. They are derived from mesenchymal (stromal) cells that first differentiate into pre-osteoblasts and then into mature, bone matrix producing osteoblasts. Inactivated or resting osteoblasts become lining cells and thus a reservoir for bone forming cells to be activated at the next remodelling cycle. Osteoblasts trapped and embedded in the mineralised matrix are called osteocyts, and are important for many properties of living bone. 

Osteoclasts Cells responsible for bone resorption during the... 

Mehler, M., Mabie, P., Zhu, G., Gokhan, S. and Kessler, J. Developmental changes in progenitor cell responsiveness to bone morphogenetic proteins differentially modulate progressive CNS lineages. Dev. Neurosci 22 74-85, 2000. 

Kowolenko, M., Tracy, L. and Lawrence, D.A., Early effects of lead on bone marrow cell responsiveness in mice challenged with L. monocytogenes, Fund. Appl. Toxicol. 17, 75, 1991. 

In response to the presence of antigenic stimuli, in seasonal allergic rhinitis (hay fever), mast cells and basophils are sensitised and inflammatory mediators, such as leukotrienes and prostaglandins, are released. Osteocytes are bone cells involved in bone formation. 

Asahara T, Masuda H, Takahashi T, Kalka C, Pastore C, Silver M, Kearne M, Magner M, Isner JM. Bone marrow origin of endothelial progenitor cells responsible for postnatal vasculogenesis in physiological and pathological neovascularization. Circ Res 1999 85 221-228. 

Vitamin D3 is a precursor of the hormone 1,25-dihy-droxyvitamin D3. Vitamin D3 is essential for normal calcium and phosphorus metabolism. It is formed from 7-dehydrocholesterol by ultraviolet photolysis in the skin. Insufficient exposure to sunlight and absence of vitamin D3 in the diet leads to rickets, a condition characterized by weak, malformed bones. Vitamin D3 is inactive, but it is converted into an active compound by two hydroxylation reactions that occur in different organs. The first hydroxylation occurs in the liver, which produces 25-hydroxyvita-min D3, abbreviated 25(OH)D3 the second hydroxylation occurs in the kidney and gives rise to the active product 1,25-dihydroxy vitamin D3 24,25 (OH)2D3 (fig. 24.13). The hydroxylation at position 1 that occurs in the kidney is stimulated by parathyroid hormone (PTH), which is secreted from the parathyroid gland in response to low circulating levels of calcium. In the presence of adequate calcium, 25(OH)D3 is converted into an inactive metabolite, 24,25 (OH)2D3. The active derivative of vitamin D3 is considered a hormone because it is transported from the kidneys to target cells, where it binds to nuclear receptors that are analogous to those of typical steroid hormones. l,25(OH)2D3 stimulates calcium transport by intestinal cells and increases calcium uptake by osteoblasts (precursors of bone cells). 

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