Multinucleated cell

Skeletal muscle is made up of many muscle fibers (Figure 1) each of which is a multinucleated cell that was formed during development by the fusion of many cells (myoblasts). Skeletal muscle is formed from precursor myoblasts which arise... 

Osteoclasts are multinucleated cells derived from pluripotent hematopoietic stem cells. Osteoclasts possess an apical membrane domain, exhibiting a ruffled border that plays a key role in bone resorption (Figure 48-12). A proton-translocating ATPase expels protons across the ruffled border into the resorption area, which is the microenvironment of low pH shown in the figure. This lowers the local pH to 4.0 or less, thus increasing the solubility of hydroxyapatite and allowing demineralization to occur. Lysosomal acid proteases are released that digest the now accessible matrix proteins. 

Note that osteoclasts are multinucleated cells often associated with small depressions on the surface of bone. They function to reabsorb calcified bone)... 

Kurihara N, Bertolini D, Suda T, Akiyama Y, Roodman CD (1990) IL-6 stimulates osteoclast-like multinucleated cell formation in long term human marrow cultures by inducing IL-1 release. J Immunol 144 4226-4230... 

Prassolov, V., Ivanov, D., Hein, S., Rutter, G., Miink, C., Lohler, J. and Stocking, C. (2001b) The Mus cervicolor MuLV isolate M813 is highly fusogenic and induces a T-cell lymphoma associated with large multinucleated cells. Virologyl Q, 39-49. 

Table 6.1. The range of blood cells that are ultimately produced upon the differentiation of pluripotential stem cells (see text for details). (Note that osteoclasts are multinucleated cells often associated with small depressions on the surface of bone they function to reabsorb calcified bone)...

In a two-year study (United States National Toxicology Program, 1989 Kari et al., 1992), dose-dependent hepatic morphological changes (anisokaryosis, elevated frequency of multinucleated cells) were observed in male mice. In a long-term feeding study (0.8% in the diet) (Shibata et al., 1991), hepatic centrilobular hypertrophy was observed in males and forestomach hyperplasia in both males and females, while no non-neoplastic changes in the kidney were reported. 

FIGURE 5-31 Structure of skeletal muscle, (a) Muscle fibers consist of single, elongated, multinucleated cells that arise from the fusion of many precursor cells. Within the fibers are many myofibrils (only six are shown here for simplicity) surrounded by the membranous sarcoplasmic reticulum. The organization of thick and thin filaments in the myofibril gives it a striated appearance. When muscle contracts, the I bands narrow and the Z disks come closer together, as seen in electron micrographs of (b) relaxed and (c) contracted muscle. 

Lycopene inhibited the TRAP+ multinucleated cell formation in both vehicle- and PTH-treated cultures. The cells that were stained with the NBT reduction product formazan were decreased by treatment with 10-5 M lycopene, indicating that lycopene inhibited the formation of ROS-secreting osteoclasts (Figure 16). 

The effects of lycopene on osteoclast formation and bone resorption were also reported by Ishimi et al. (1999) in murine osteoclasts formed in coculture with calvarial osteoblasts (Ishimi et al., 1999). Their results differed from those of Rao et al. (2003) in that they found that lycopene inhibited the PTH-induced, but not the basal, TRAP+ multinucleated cell formation. Furthermore, they could not demonstrate any effect of lycopene on bone resorption. They also did not study the effect of lycopene on ROS production. 

Electron microscopy of Ankistrodesmus braunii. (a-c) Cells from cultures treated with reverse osmosis fraction (d, e) cells from cultures treated with catechol, (a) cell containing several nuclei (N) and a single chloroplast (Ch) with abundant starch, (b) Detail from (a) showing an abortive cell plate (arrows) between two of the nuclei (N). (c) The cell plates are associated with irregularly oriented microtubules (arrows), (d) Multinucleate cells with randomly oriented developing septa (arrows) and several chloroplasts with abundant starch, (e) A cluster of fully developed endospores still enclosed in the mother cell wall (arrow). 

Skeletal muscle moves the bones attached to joints. These muscles are composed of bundles of long, multinucleated cells. The cytoplasm contains a high concentration of a special macromolecular contractile-protein complex, actomyosin (Chap. 5). There is also an elaborate membranous network called the sarcoplasmic reticulum that has a high Ca2+ content. The contractile-protein complex has a banded appearance under microscopy. 

Osteoclasts are multinucleated cells found on the endosteal surface of bone, in Haversian systems and periosteal surfaces. PTH activates osteoclasts (indirectly via osteoblasts that possess PTH receptors). Calcitonin is a potent inhibitor of osteoclast activity. Local cytokine factors, including interleukin-1 (IL-1), tumour-necrosis factor (TNF), TGF- 0 and interferon-y (INF-y), are important regulators. Osteoclast resorption of bone releases collagen peptides, pyridinoline cross-links and calcium from the bone matrix, through the action of lysosomal enzymes (collagenases and cathepsins). The collagen breakdown products in serum and urine (e.g. hydroxyproline) can be used as biochemical markers. 

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