Skeletal remodelling

Slemenda, C. W., Peacock, M., Hui, S., Zhou, L., and Johnston, C. C. (1997). Reduced rates of skeletal remodeling are associated with increased bone mineral density during the development of peak skeletal mass. ]BMR 12, 676-682. 

Bone turnover Skeletal turnover Skeletal metabolism Bone remodelling... 

PTH is the most important regulator of bone remodelling and calcium homeostasis. PTH is an 84-amino acid polypeptide and is secreted by the parathyroid glands in response to reductions in blood levels of ionised calcium. The primary physiological effect of PTH is to increase serum calcium. To this aim, PTH acts on the kidney to decrease urine calcium, increase mine phosphate, and increase the conversion of 25-OH-vitamin D to l,25-(OH)2-vitamin D. PTH acts on bone acutely to increase bone resorption and thus release skeletal calcium into the circulation. However, due to the coupling of bone resorption and bone formation, the longer-term effect of increased PTH secretion is to increase both bone resorption and bone formation. 

Pulmonary hypertension develops late in the course of COPD, usually after the development of severe hypoxemia. It is the most common cardiovascular complication of COPD and can result in cor pulmonale, or right-sided heart failure. Hypoxemia plays the primary role in the development of pulmonary hypertension by causing vasoconstriction of the pulmonary arteries and by promoting vessel wall remodeling. Destruction of the pulmonary capillary bed by emphysema further contributes by increasing the pressure required to perfuse the pulmonary vascular bed. Cor pulmonale is associated with venous stasis and thrombosis that may result in pulmonary embolism. Another important systemic effect is the progressive loss of skeletal muscle mass, which contributes to exercise limitations and declining health status. 

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... 

B. R. Troen, Skeletal Development and Remodeling in Health, Disease, and Aging, 2006,1068, 165. 

Witten, P.E., Hansen, A., Hall, B.K. (2001) Features of Mono- and Mnltinncleated Bone Resorbing Cells of the Zebrafish Danio Rerio and Their Contribntion to Skeletal Development, Remodeling and Growth. Journal of Morhology 250, 197-207. 

Bone tissue has a rather unique capability among human tissues in response to injury or other changes that alter its mechanical requirements it can continuously remodel itself to meet those mechanical needs best [51, 52], For example, when a bone fractures, the body creates new bone to connect the broken fragments together, and then remodels the new bone to optimize its mechanical function in the particular region of the skeleton that the fracture has occurred. Human skeletal tissue has several functions, but, when a bone is fractured by trauma, or removed surgically due to disease or tumor formation, we only seek solutions so that its mechanical function can be carried out [53, 54],... 

Horackova et al. (28) Guinea pig LAD ligation Skeletal myoblasts vs. cardiac fibroblasts vs. cardiomyocytes Myotube formation in SKMB-treated animals SKMB superior to CM and CFs regarding remodeling functional improvement in SKMB-treated animals no comparison regarding the LV function... 

Looking at the results of both preclinical and clinical studies, we recognize the potential of cardiac cell transplantation to alter outcomes. However, we have to admit that in most cases, we do not understand how different cell types improve LV function. Increases in microvascular density, diastolic and systolic function, and an attenuated remodeling, are all reported after the application of many different cell types, but the exact mechanisms are unclear. Only a few studies address the elec-trophysiologic fate of the injected cells (71,72). In these studies, skeletal myoblasts were found to be isolated from the surrounding myocardium, and they underwent severe... 

The role of cells residing within skeletal tissues is to maintain a balance between the processes of resorption and formation. When these two processes are essentially equal, a conservation-mode of remodeling exists... 

Because Cd accumulation in bones is considerably lower that concentrations found in liver and kidney, it was initially hypothesized that that skeletal effects were secondary to renal toxicity. This notion is still reported in several texts. A number of rodent studies have been conducted that clearly demonstrate Cd-induced skeletal effects at lower concentrations and/or at shorter exposure durations than is needed to induce renal toxicity. Many in vivo studies involve measuring the rates of 45Ca mobilization trombone. Calcium naturally is released trombones as they are remodeled. Remodeling is the process by which bone is broken down and rebuilt in order to optimize structure and architecture. Approximately 7-8% of the skeletal system (by mass) is remodeled annually. Calcium is mobilized as small packets of bone are released. In experiments with rodents, 45Ca was released trombones nearly twice as quickly as control animals after 10 days of dietary Cd exposure at 50ppm. This Ca release preceded renal toxicity symptoms. Similar studies showed increased 45Ca release from both dog and mice as early as three days post Cd exposure via the diet. 

There is apparent potential for extensive remodeling of the skeletal system in the postnatal period extra ribs become vertebral arches and fused ribs and other skeletal malformations disappear prior to... 

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