In bone tissues

The Ga and Ga isotopes were studied, eg, as citrate salts, for detection of tumors. Ga concentrates in bone tissues and Ga seem to have a tumor-specific affinity. Additional data are available (41,42). 

Hydroxyapatite (HA) coating on the surface of the hip stem and the acetabular cup is the most recent advancement in artificial hip joint implant technology. This substance is a form of calcium phosphate, which is sprayed onto the hip implant. It is a material found in combination with calcium carbonate in bone tissue, and bones can easily adapt to it. When bone tissue does grow into HA, the tissue then fixes the hip joint implant permanently in position. These HA coatings are only used in press-fit, noncemented implants. 

Hartsook, E., Cowan, R.L., Chandler, P.T. and Whelan.J.B. 1956 The relative retention of strontium and calcium in bone tissue. Journal of Biological Chemistry 218 911-919. 

Under normal circumstances, the skeleton undergoes a dynamic process of bone remodeling. Bone tissue responds to stress and injury through continuous replacement and repair. This process is completed by the basic multicellular unit, which includes both osteoblasts and osteoclasts. Osteoclasts are involved with resorption or breakdown of bone and continuously create microscopic cavities in bone tissue. Osteoblasts are involved in bone formation and continuously mineralize new bone in the cavities created by osteoclasts. Until peak bone mass is achieved between the ages of 25 and 35, bone formation exceeds bone resorption for an overall increase in bone mass. Trabecular bone is more susceptible to bone remodeling in part owing to its larger surface area. 

Fig. 6.3 Schematic illustration of bone modelling and remodelling. Bio-inorganic hybrid nanomaterials are kept fresh in bone tissue.

Ordered mesoporous silica have already been studied as carriers for drug delivery [1,2] recently, their use has also been proposed in bone tissue engineering [3,4], in combination with bioactive glass-ceramic scaffolds [5,6]. The kinetics of ibuprofen release in SBF [7] from MCM-41 silica with similar pore diameter has shown puzzling discontinuities [3,6,8] aim of the present work is to assess whether these anomalies may be related to structural changes in the MCM-41 mesoporous spheres under the adopted conditions. 

Droloxifene (3-hydroxy-tamoxifen) behaves as an estrogen agonist in bone tissue and several lipid and coagulation markers in castrated rat models and does not show stimulation of the endometrial epithelium in preclinical studies (Ke et al. 1997). Endometrial stimulation has, however, been observed in clinical trials, which, together with the fact that as an estrogen agonist it is ten times less potent than tamoxifen in bone tissue and lipid metabolism (Hendrix et al. 2001) and that in a recent head-to-head comparison with tamoxifen droloxifene was demonstrated not to be superior in any parameter of breast cancer treatment efficacy (Buzdar et al. 2002), has resulted in cancellation of its clinical development. 

The concept of sarcopenia is not as well known as osteoporosis, which is the equivalent in bone tissue loss. Even though an older patient has not lost weight, sarcopenia can still be present because of an increased amount of fat tissue. It is important to check the patients for muscle strength as this is a condition which we are able to treat successfully if discovered in time. There are several other reasons for loss of muscle strength in the elderly, such as sickness, inactivity and poor nutrition (Doherty 2003). 

Excretion of Ca-r-r phosphates is significantly higher in leukemia patients in comparison with healthy controls. Vitamin D3 levels in patients with leukemia are significantly lower (18.8+0.5 vs 32.1+2.0). In acute leukemia changes are revealed in bone tissue collagen with an increase of oxyproline and asparaginic acid concentrations (fig. 5). 

Strontium-90, a radioactive strontium isotope with a half-hfe of 29 years, is a dangerous fallout source of radiation from atmospheric nuclear bombs. If a person is exposed to it, it will rapidly accumulate in bone tissue and interfere with the production of new red blood cells... 

Some compounds, such as strontium chromate and strontium fluoride, are carcinogens and toxic if ingested. Strontium-90 is particularly dangerous because it is a radioactive bone-seeker that replaces the calcium in bone tissue. Radiation poisoning and death may occur in people exposed to excessive doses of Sr-90. Strontium-90, as well as some other radioisotopes that are produced by explosions of nuclear weapons and then transported atmospherically, may be inhaled by plants and animals many miles from the source of the detonation. This and other factors led to the ban on atmospheric testing of nuclear and thermonuclear weapons. 

In the past decade Raman spectroscopy has assumed an important role in musculoskeletal tissue studies, especially in bone tissue studies. Applications to a wide range of problems in basic biology, biomechanics, and medicine have appeared in the journal literature. Most workers have used cell cultures or excised bone tissue, including human biopsy and cadaveric tissue. We expect that Raman spectroscopy will become increasingly important in such studies, as more life scientists and engineers learn how to employ it. Just as importantly, recent reports of non-invasive spectroscopy suggest that Raman spectroscopy may have a role in human subjects studies of bone development, function, and disease. 

Lindh U, Brune D, Nordberg G, etal. 1980. Levels of antimony, arsenic, cadmium, copper, lead, mercury, selenium, silver, tin and zinc in bone tissue of industrially exposed workers. Sci Total Environ 16 109-116. 

Liquid crystalline, ferroelectric, and photochromic systems Controlled drug-delivery from polyphosphazenes Use in bone tissue engineering... 

Inorganic lead may be absorbed through the GI tract, the respiratory system, and the skin. Ingested inorganic lead is absorbed more efficiently from the GI tract of children than that of adults, readily crosses the placenta, and in children penetrates the blood-brain barrier. Initially, lead is distributed in the blood, liver, and kidney after prolonged exposure, as much as 95% of the body burden of lead is found in bone tissue. 

Doty, S.B. (1989) Cell-to-cell communication in bone tissue. The Biological Mechanism of Tooth Eruption and Root Resorption. Editor, Z. Davidovitch 61-69. EBSCO Media, Birmingham, Alabama... 

Kufahl, R.H. and Saha, S. (1990) A theoretical model for stress-generated fluid flow in the canaliculi-lacunae network in bone tissue. Journal of Biomechanics 23 171-180... 

Owan, M. and Triffitt, J.T. (1976) Extravascular albumin in bone tissue. Journal of Physiology 257 293-307... 

Schroder and co-workers (Schroder etal., 1999,2000) studied PolyP metabolism in bone tissues and osteblast cultures. They revealed that PolyP metabolism in human osteoblasts was modulated by stimulators of osteoblast proliferation and differentiation (Leyhausen et al., 1998). A combined treatment of the cells with dexamethasone, ft-glycerophosphate, epidermal growth factor (EGF), and ascorbic acid resulted in a dramatic decrease in PolyP content. This decrease is caused mainly by a decrease in the amount of soluble long-chain PolyPs. The amount of this PolyP fraction, but not the amount of insoluble long-chain PolyPs, further decreases after additional treatment of the cells with la, 25-dihydroxy vitamin D3. The decrease in PolyP content during treatment with dexamethasone, ft-glycerophosphate, EGF and ascorbic acid is accompanied by a decrease in exopolyphosphatase activity. However, additional treatment with la, 25-dihydroxyvitamin D3 results in a significant increase of the enzyme activity. Therefore, it is reasonable to assume that PolyP... 

Exopolyphosphatase activity in osteoblasts is much higher than in other mammalian cells and tissues tested. Moreover, endopolyphosphatase activity is present in bone-forming osteoblasts (Schroder et al., 2000). All of these data suggest that, besides PPi, PolyP is involved in the mineralization process in bone tissue. 

In view of the fact that PolyP is probably involved in the regulation of phosphate metabolism in bone tissues (Schroder et al, 1999 2000), attempts were made to prove the potential therapeutic uses of PolyPs in the treatment of some bone diseases. 

Partridge, K. A., and Oreffo, R. O. C. (2004) Gene deliveiy in bone tissue engineering Progress and prospects using viral and nonviral strategies. Tissue Eng. 10, 295-307. 

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