Bone stmcture

Pa.g et s Disease of Bone. Paget s disease, osteitis deformans, occurs mainly ia people over 40. About twice as many men as women are affected. The disease, caused by faulty utilisation of may be mild and asymptomatic requiring Httle or no treatment. Clinical signs are high alkaline phosphatase and high urine hydroxyproline as weU as abnormal bone stmcture which usually goes unrecognised until discovered accidentally by routine x-ray examination (32). 

Gallium nitrate is used clinically, at lower doses than for treating tumors, to treat hypercalcemia associated with bone cancers. " It incorporates into bone at very low levels and prevents calcium resorption, leading also to higher phosphate and collagen levels, and hence sturdier bone stmcture. ... 

Riiegsegger P. Imaging of Bone Stmcture. 2nd ed. Boca Raton CRC Press, 2001 1-24. Paulus M, Gleason S, Kennel S, Hunsicker P, Johnson D. High resolution X-ray computed tomography an emerging tool for small animal cancer research. Neoplasia 2000 2(l-2) 62-70. 

Fig. 15 Similarity of cancellous bone stmctures and PLA foam macrostmctures. Reprinted from [148] with permission from Elsevier...

Both chloramphenicol and thiamphenicol cause reversible bone marrow suppression (9). The irreversible, often fatal, aplastic anemia, however, is only seen for chloramphenicol (9). This rare (1 in 10,000—45,000) chloramphenicol toxicity has been linked to the nitroaromatic function (1,9). Thiamphenicol, which is less toxic than chloramphenicol in regard to aplastic anemia, lacks potency as can be seen in Table 1, and thiamphenicol has never found much usage in the United States. An analogue of thiamphenicol having antimicrobial potencies equivalent to chloramphenicol was sought. Florfenicol (2) was selected for further development from a number of closely related stmctures. 

Resorption of bone tissue occurs in total hip joint replacement patients if sufficient stresses are not adequately transmitted to the remaining bone in exactiy the same way that the bone transmitted those stresses originally. Therefore, the design and proper placement of the neck coUar and hip stem must be effective in recreating anatomical stmcture. 

Isolation and Structure Determination. The isolation and stmcture elucidation of vitamin D are closely related to the efforts to understand and cure tickets and related bone diseases. The advent of the use of soft coal, the migra tion of people to cities, and the tendency of people and animals to spend less time in sunshine caused a decline in the abiUty of populations to synthesize sufficient quantities of vitamin D. This led to the increased incidence of tickets, beginning around the mid-1600s (3). 

X-rays were discovered by Wilhelm Roentgen in 1895. Soon after their discovery Roentgen used x-rays to image the bones in a human hand. The x-rays transmitted through the hand (phenomenon 1) were recorded on photographic film. The bones or other dense objects absorb x-rays more than do soft tissues or less dense materials (phenomenon 2). This method of imaging the internal stmcture of an object is known as x-ray radiography. 

Biological functions of Ca(Il) ion are numerous but maybe classified ia one of three categories the formation of soHd skeletal material such as bone, teeth, and shell the stabilizing of proteia conformational stmcture and the most varied, the abiUty of Ca(Il) to trigger certain physiological activities such as muscle contraction and the release of hormones (qv). 

The diversity in primary, secondary, tertiary, and quaternary stmctures of proteins means that few generalisations can be made concerning their chemical properties. Some fulfil stmctural roles, such as the collagens (found in bone) and keratin (found in claws and beaks), and are insoluble in all solvents. Others, such as albumins or globulins of plasma, are very soluble in water. Still others, which form part of membranes of cells, are partly hydrophilic ( water-loving , hence water-soluble) and partly lipophilic ( lipid-loving , hence fat-soluble). 

Bone is composed of living cells in a ceramic matrix. The matrix itself consists of inorganic (ceramic) and organic matter, along with water. The composition and structure of bones are very complex, and simulating a material similar to bone by artificial means is very difficult. CBPCs, however, hold promise toward producing materials similar to bone in composition, if not in exact stmcture. 

Osteoblasts become trapped in lacunae, in the process of forming the bone and are then termed osteocytes . Osteocytes are considered to be important in the mineralization process. Thus, if an artificial bone is to be fabricated that should eventually be mineralized to a natural bone, then the artificial bone should have a porous stmcture with canaliculi and lacunae. The porous stmcture will enable new osteocytes to enter the artificial bone and cause mineralization. 

As we move from the periphery of the bone to the center, the stmcture becomes anisotropic and tubular. This structure, called osteons , consists of tubes of approximately 200-/rm diameter with a central canal called the Haversian canal to house blood vessels. Lamellae are arranged concentric to this canal and parallel to the... 

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