Skeletal system

Bone mineral density can be measured at various sites throughout the skeletal system and by various methods. The site of measurement can be either central (hip and/or spine) or peripheral (heel, forearm, or hand). Dual-energy x-ray absorptiometry (DXA) can be used to measure central and peripheral sites of bone mineral density. Quantitative ultrasound, peripheral quantitative computed tomography, radiographic absorptiometry, and single-energy x-ray absorptiometry are used to measure peripheral sites. 

The user interface, the interpreter, and the inference engine together comprise the ES shell or a skeletal system. As these components are largely independent of the specific application, all that is needed to create a working ES from the shell is to feed it with rules and facts. 

Nevertheless, their potential use in large treatments will depend on systemic actions, since the beneficial effects may be counterbalanced by deleterious consequences on the cardiovascular (Hegele-Hartung et al. 1997) and skeletal systems (Gallagher et al. 1993). Moreover, most pure antiestrogens have a poor oral bio availability. Therefore, the use of other routes of administration, such as intravenously, is mandatory. In some cases, to circumvent such problems, the production of nanospheres loaded with the pure antiestrogen RU 58668 has been tested (Ameller et al. 2004). 

In doses of 1.2 mg Ni/kg and up to 20 mg Ni/kg, nickel chloride caused increased resorption rates and a number of malformations in murine foetuses, specific to the foetal skeletal system, as shown by atomic absorption [425]. It was believed that nickel chloride might influence embryos during the passage through the oviduct, with subsequent effect on the development after implantation [426]. Preimplantation mouse embryos have also been used to investigate toxic effects of nickel chloride on early embryo development in vitro, and a dose-dependent effect has been found [427]. 

The bone becomes depleted of calcium salts when the urine is acidic over a relatively long period. This was shown by Goto (17) who fed rabbits large doses of hydrochloric acid. He then showed that urinary calcium loss occurred in concert with a marked reduction in mass of the skeletal system, and also that the total non-fat dry weight of bone decreased,implying a loss of bone matrix. A dose-dependent, dietary acid induced loss of labelled calcium from rat bone has been reported by Thorn and his coworkers (18). They demonstrated that in response to graded doses of ascorbic acid, cells in tissue culture, and bones in whole animals fed such doses were depleted of the labelled calcium. 

Curium metal and its compounds are radioactive bone-seeking poisons that attack the skeletal system of humans and animals. Care must be used in handling them. 

Nicotine is teratogenic in mice skeletal system malformations occurred in the offspring of pregnant mice injected subcutaneously with nicotine between days 9 and 11 of gestation/ It has also been found to cause behavioral changes in animals after experimental prenatal exposure/... 

Berkelium accumulates in the skeletal system. The radiation can cause damage to red blood cells. The maximum permissible body burden reported for the isotope Bk-249 in the human skeleton is 0.4 ng (Cunningham, B.B., 1968, Berkelium. In The Encyclopedia of the Chemical Elements. C.A. Hampel, ed., p. 48. New York Reinhold Book Corporation). 

Exposure to Cf radiation can cause cancer. Similar to other radioactive elements, californium can accumulate in the skeletal system, causing damage to the red cell forming mechanism. 

Kenney MA, McCoy H. 1992. A review of biointeractions of Ni and Mg. I. Enzyme, endocrine, transport, and skeletal systems. Magnes Res 5 215-222. 

This description assumes that the examiner is familiar with the anatomy of the skeletal system of the common laboratory animals as well as with directional terms used in anatomy (Notes 1 to 3). 

Mechanism of Action An electrolyte that is essential for the function and integrity of the nervous, muscular, and skeletal systems. Calcium plays an important role in normal cardiac and renal function, respiration, blood coagulation, and cell membrane and capillary permeability. It helps regulate the release and storage of neurotransmitters and hormones, and it neutralizes or reduces gastric acid (increase pH). Calcium acetate combines with dietary phosphate to form insoluble calcium phosphate. Therapeutic Effect Replaces calcium in deficiency states controls hyperphosphatemia in end-stage renal disease. 

Endothelins interact with several endocrine systems, increasing the secretion of renin, aldosterone, vasopressin, and ANP. They exert a variety of actions on the central and peripheral nervous systems, the gastrointestinal system, the liver, the urinary tract, the male and female reproductive systems, the eye, the skeletal system, and the skin. Finally, ET-1 is a potent mitogen for vascular smooth muscle cells, cardiac myocytes, and glomerular mesangial cells. 

The bisphosphonates are analogs of pyrophosphate in which the P-O-P bond has been replaced with a nonhydrolyzable P-C-P bond (Figure 42-4). Etidronate, pamidronate, and alendronate have now been joined by risedronate, tiludronate, ibandronate, and zoledronate for clinical use. The bisphosphonates owe at least part of their clinical usefulness and toxicity to their ability to retard formation and dissolution of hydroxyapatite crystals within and outside the skeletal system. They localize to regions of bone resorption and so exert their greatest effects on osteoclasts. However, the exact mechanism by which they selectively inhibit bone resorption is not clear. 

The inorganic crystals are typically orientated in a precise way if they are part of a skeletal system. The crystals show evidence of a variety of normal growth processes, e. g. spiral and dendritic forms. 

Miller, E. J. A review of biochemical studies on the genetic distinct collagens of the skeletal system. Clin. Orthop. 92, 260 (1973)... 

Sulfation of the carbohydrate chain occurs after the monosaccharide to be sulfated has been incorporated into the growing carbohydrate j chain. The source of the sulfate is 3 -phosphoadenosyl-5 -phospho-sulfate (PAPS, a molecule of AMP with a sulfate group attached to the 5-phosphate). Sulfotransferases cause the sulfation of the carbohydrate chain at specific sites. [Note An example of the synthesis of a sulfated glycosaminoglycan, chondroitin sulfate, is shown in Figure 14.11.] PAPS is also the sulfur donor in glycosphingolipid synthesis. [Note A defect in the sulfation process results in one of several autosomal recessive disorders that affect the proper development and maintenance of the skeletal system. This illustrates Ihe importance of the sulfation step.]... 

Biochemical individuality, which is genetically determined, is accompanied by. and in a sense based upon, anatomical individuality, which must also have a genetic origin. Substantial differences, often oflaige magnitude, exist between the digestive tracts, the muscular systems, the circulatory systems. the skeletal systems, the nervous systems, and the endocrine systems of so-called normal people. Similar distinctiveness is observed at the microscopic level, for example in the size, shape and distribution of neurons in... 

The more classical Itinehoii of parathyroid hormone is concerned with its control of the maintenance of constant circulating calcium levels. Its action is on 11) Ihe kidney, where it increases the phosphate in the urine. (2) the skeletal system, where it causes calcium resorplion from bone, and t3l the digestive system, where it accelerates (stimulates) calcium absorption into the hitskI The hormone and gland exhibit characteristics of feedback control when the concentration of calcium tons in the blood falls, the secretion of the hormone increases, and when their concentration rises, the secretion of hormone decreases... 

---