PubMed · 4581567
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J Vogel, E Müller, E Harzendorf. 1973. [Computer-assisted respiratory function diagnosis].. https://pubmed.ncbi.nlm.nih.gov/4581567/
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Polyurethanes are widely used as biomaterials for medical implants because of their excellent mechanical properties and moderate biocompatibility. However, the demand for more bioresistant and biocompatible polyurethanes to meet the needs of long-term implant devices still remains an important issue. Since most biological interactions with materials occur at the interface, a significant number of studies for improving the biocompatibility of polyurethanes have concentrated on surface modification. It is well known that additives used in polymeric materials as processing aids, mold releasing agents, antioxidants, etc., migrate to the surface and change the surface properties of the material. Under certain conditions polymeric additives may also migrate toward surfaces. This study describes two fluorine-containing, surface-modifying macromolecules (SMMs) that have been evaluated for their ability to inhibit polyurethane degradation. These materials actively migrate to the upper surface of a material film when they are mixed with a base polymeric materia. Contact angle measurements for the mixture of SMM with base polyurethane indicate that the surface becomes more hydrophobic after adding the SMMs, while X-ray photoelectron spectroscopy analysis shows an enrichment of fluorine on the polymer surfaces. Differential scanning calorimetry thermograms indicate that the micro-structure, as defined by the thermal transitions of the base polymer, are not altered by the addition of SMMs. Enzyme-induced biodegradation tests exhibit a significant reduction of polyurethane degradation in the presence of these surface-resident materials. The results indicate that the SMMs have the potential to resist hydrolytic degradation mediated by lysosomal enzymes while generating a surface chemistry on the native elastomer which is similar in nature to that of a fluoropolymer, e.g., Teflon.
Osteoporosis has become a major public health problem in many western countries in which about 25% of women by the age of 65 will have had osteopenic fractures. The most important contributing factor to this condition is loss of gonadal function. This progressive disease, characterized by reduction in bone mass, may be prevented by estrogen replacement therapy. While there are several methods of diagnosing the disease when already established, there is no method that can identify women at high risk of developing osteoporosis. We have developed a biological test in which the serum of postmenopausal women is added to rat osteoprogenitor cell culture and its influence on proliferation, differentiation and mineralization of bone cells is determined. The serum of 20 menopausal women was examined by the biological test and the results compared to the findings of dual photon absorptiometry. This showed that rapid bone-losers had a significantly lower mineralization index as compared to nonosteopenic women (p < 0.0001). The proliferation index (cell count) and alkaline phosphatase activity did not show significant differences between osteopenic and nonosteopenic groups. This preliminary study showed that a test based on serum reacting with a culture of bone cells to induce mineralization may be of value in the diagnosis of osteoporosis.
High calcium intake during childhood has been suggested to increase bone mass accrual, potentially resulting in a greater peak bone mass. Whether the effects of calcium supplementation on bone mass accrual vary from one skeletal region to another, and to what extent the level of spontaneous calcium intake may affect the magnitude of the response has, however, not yet been clearly established. In a double-blind, placebo-controlled study, 149 healthy prepubertal girls aged 7.9+/-0.1 yr (mean+/-SEM) were either allocated two food products containing 850 mg of calcium (Ca-suppl.) or not (placebo) on a daily basis for 1 yr. Areal bone mineral density (BMD), bone mineral content (BMC), and bone size were determined at six sites by dual-energy x-ray absorptiometry. The difference in BMD gain between calcium-supplemented (Ca-suppl.) and placebo was greater at radial (metaphysis and diaphysis) and femoral (neck, trochanter, and diaphyses) sites (7-12 mg/cm2 per yr) than in the lumbar spine (2 mg/cm2 per yr). The difference in BMD gains between Ca-suppl. and placebo was greatest in girls with a spontaneous calcium intake below the median of 880 mg/d. The increase in mean BMD of the 6 sites in the low-calcium consumers was accompanied by increased gains in mean BMC, bone size, and statural height. These results suggest a possible positive effect of calcium supplementation on skeletal growth at that age. In conclusion, calcium-enriched foods significantly increased bone mass accrual in prepubertal girls, with a preferential effect in the appendicular skeleton, and greater benefit at lower spontaneous calcium intake.