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Biomedical subjects

R R LeVier

Publications and source records attributed to R R LeVier.

11 recordsLinked to original sources

The breast implant controversy.

The breast implant issue is a "bad news/good news" story. For many women with implants, the controversy has caused a fair degree of anxiety which may or may not be resolved as further information becomes available. It has also taken its toll on Dow Corning. Whole lines of medical products have been eliminated or are being phase out. The development of new medical applications has been terminated. As a consequence, employees have lost their jobs. What the effect will be on the biomedical industry as a whole remains to be seen (11). While silicones have been an important component in various medical devices, it is likely that other materials can be used as replacements. However, suppliers of non-silicone materials are also reevaluating their role in this market. For example, Du Pont, the nation's largest chemical company, has determined that the unpredictable and excessive costs of doing business with manufacturers of implantable medical devices no longer justifies the unrestricted sale of standard raw materials into this industry. Other companies are quietly following suit. On the up side, it is possible that the research being driven by this controversy will result in a greater understanding of the immunologic implications of xenobiotics, of the importance of nonbiased observations, of the need for ready access to valid data sets, and of the opportunity for valid scientific information to guide legal decisions. Only time will tell.

Animals↗

Positive identification of silicone in human mammary capsular tissue.

A specific quantitative assay was developed to determine silicone concentrations in contracted mammary capsular tissue. The concentrations of silicone in tissues from 14 patients with gel-filled implants varied from 15 to 9800 micrograms polydimethylsiloxane per gram of tissue. This silicone is probably a high-molecular-weight polymer that has diffused through the implant envelope. Samples from a patient with saline-filled implants contained no silicone. The concentration of silicone was not related to capsule age. The polymer in these tissues appeared to be unaltered, in that no evidence of metabolic products was found.

Breast↗

Occurrence and activity of myofibroblasts in human capsular tissue surrounding mammary implants.

Capsular tissue obtained from a series of 16 patients with silicone mammary implants was exposed in vitro to smooth-muscle stimulants and relaxants. Capsule relaxation was produced in 75 percent of the patients. The most active antagonists were papaverine and veratrine. Capsule contracture was produced in 69 percent of the patients. The most active agonists were histamine and epinephrine. Myofibroblasts were identified in several capsules. These data support the hypothesis that the myofibroblasts is a probable cause of capsular contracture.

Adolescent↗

Clinical evaluation of the new compound diphenylsilanediol for ani-epileptic efficacy and toxicity.

A controlled clinical trial of the anti-epileptic efficacy and toxic side effects of diphenylsilanediol was conducted on 24 client-owned epileptic dogs. Data obtained from an abbreviated procedural treatment program indicated that diphenylsilanediol compared favorably with primidone as an anti-epileptic compound, but had limiting toxic side effects to the liver, pancreas, and possibly to other tissues. There was a mean reduction of 60.7% in seizure frequency in 15 epileptic dogs treated with diphenylsilanediol when compared with their pretreatment frequency. There was a mean reduction of 55.6% in seizure frequency in 9 spileptic control dogs treated with primidone. Samples of blood obtained from the dogs in the program on the 4th, 8th, 12th, 24th, and 36th weeks of treatment were examined for complete blood cell count, blood urea nitrogen, liver function, and pancreatic function. Toxic side effects were not seen among the primidone-treated control dogs, with the exception of occasional dose-related drowsiness. Among the diphenylsilanediol-treated dogs, 3 developed liver disease, 2 developed definite pancreatic changes, and 2 showed evidence of bone marrow suppression. Four dogs died during treatment with diphenylsilanediol, whereas no deaths occurred during the same interval of primidone therapy.

Animals↗

Distribution of silicon in the adult rat and rhesus monkey.

The distribution of silicon in tissues of the rat and rhesus monkey was determined using a colorimetric method specifically designed for biological materials. Soft-tissue silicon levels in both species varied from 1 to 33 mug silicon/g dry weight (ppm) excepting the primate lung and lymph nodes, which averaged 942 ppm and 101 ppm, respectively. This distribution may reflect flow-through of silicon in the form of particulates and water-soluble silicate contaminates in the environment and food effectively masking tissue or organ-specific silicon of functional significance. The silicon content of the whole rat femur was 38 ppm as determined by emission spectroscopy, whereas the monkey femur shaft was 43 ppm and the femur head containing the epiphysis was 456 ppm. This silicon may be functionally involved in the calcification process as suggested by others. The silicon content of rat liver subcellular fractions was also determined. The supernatant, nuclei/debris, and mitochondrial portions contained 0.6-1.0 mug silicon/g liver equivalents, whereas the microsomal fraction contained only 0.2 mug silicon/g liver equivalents.

Animals↗