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PubMed2000

Induction of hypergammaglobulinemia and macrophage activation by silicone gels and oils in female A.SW mice.

Although most published epidemiological studies have found little evidence of systemic autoimmune disease associated with silicone breast implants, there still remains a question of whether silicones can cause local and/or systemic immune dysfunction. This study further investigates the effects of silicones on autoantibody and immunoglobulin production and macrophage activation in female A.SW mice. Sixty mice were divided among four treatment groups receiving a 0.5-ml intraperitoneal injection of either phosphate-buffered saline (PBS), pristane, silicone gel, or silicone oil. Test bleeds were taken periodically for 6 months. In contrast to pristane, neither silicone gel nor silicone oil induced lupus-associated antinuclear autoantibodies (immunoglobulin G [IgG] anti-nRNP/Sm, Su, and ribosomal P) or lupus nephritis. However, serum IgM became elevated persistently within 1 month of silicone gel or silicone oil administration. Also, the level of IgG3 was clearly elevated in silicone oil-treated mice. In contrast, IgG1, IgG2a, and IgG2b levels were not affected greatly by either silicone gel or oil. Furthermore, peritoneal macrophages from silicone- and pristane-treated mice produced higher levels of interleukin-1beta (IL-1beta) and IL-6 than those from PBS-treated mice after lipopolysaccharide stimulation. These results suggest that silicone gels and oils are capable of inducing hypergammaglobulinemia and activating macrophages in female A.SW mice.

Animals↗
PubMed1999

Timing of retinal redetachment after removal of intraocular silicone oil tamponade.

PURPOSE: To evaluate the interval between removal of intraocular silicone oil tamponade and retinal redetachment after pars plana vitrectomy, and to investigate factors influencing the length of the interval. PATIENTS AND METHODS: The retrospective study included 42 eyes of 42 consecutive patients who experienced a retinal redetachment after silicone oil had been removed 8.0+/-6.2 months after an initial pars plana vitrectomy including intraocular silicone oil (5,000 centistokes) tamponade. Pars plana vitrectomy had been performed for proliferative vitreoretinopathy caused by complicated rhegmatogenous retinal detachment. RESULTS: The retina redetached 2 days to 5.5 months after silicone oil removal (mean +/- SD, 1.3+/-1.4 months; median, 18 days). Thirteen (30%) of all 42 redetachments occurred in the first 9 days, 21 (50%) of all 42 retinal redetachments occurred in the first 18 days, and 32 (75%) of all 42 retinal redetachments occurred in the first 50 days. The interval between silicone oil removal and retinal redetachment was statistically (by analysis of variance) independent of the method of silicone removal (transpupillary drainage vs via pars plana sclerotomies), refractive error of the eye (P = .62), time between initial pars plana vitrectomy and silicone oil removal (P = .99), visual acuity before silicone oil removal (P = .26), type of anesthesia (P = .69), gender (P = .80), and age (P = .48) of the patients. CONCLUSION: The risk of retinal redetachment decreases steeply with increasing time after silicone oil removal. Three to 5 months after oil removal, retinal redetachment becomes unlikely. The time of retinal redetachment is statistically independent of the method of silicone oil removal, refractive error, time between the preceding pars plana vitrectomy and silicone oil removal, visual acuity before silicone oil removal, type of anesthesia, and gender and age of the patents. These data may be important for scheduling reexaminations and for counseling patients in their planned activities after removal of intraocular silicone oil tamponade.

Adolescent↗
PubMed1992

Silicon accumulation in dialysis patients.

Plasma silicon measurements have been obtained in patients with end-stage renal disease on chronic dialysis therapy. The mean +/- SE values for normal plasma silicon concentrations are .15 +/- .02 mg/L. All dialysis groups showed marked elevations in their plasma silicon that correlated with the silicon content of their respective dialysis fluids. The values of two different hemodialysis groups and a peritoneal dialysis group were 4.6 +/- .4, 2.5 +/- .2, and 1.9 +/- 1.2 mg/L, respectively. The silicon content of their respective dialysis fluids were 4.0 +/- .7, 0.5 +/- .4, and 0 +/- .1 mg/L. The ultrafiltrability of plasma silicon through Cuprophane membranes was 79 +/- 2%. Hemodialysis patients drinking high-silicon well water showed significantly higher plasma silicon levels than patients drinking lower silicon municipal water. It is concluded that use of dialysis fluid with elevated silicon levels and the consumption of water containing high concentrations of silicon are two important determinants of silicon levels in a dialysis population. We observed no overt effects of silicon accumulation on the health status of our dialysis patients.

Dialysis Solutions↗
PubMed1994

Silicon tissue assays in nonaugmented cadaveric patients: is there a baseline level?

Microscopic silicone in various tissues in the bodies of females with breast implants has led to the possible incrimination of these implants with connective-tissue disorders. Current technology precludes accurate silicone measurements, but all compounds containing the element silicon (which would include silicone) may be measured accurately. Direct positive correlations of silicon assays with silicone measured levels were confirmed by adding known amounts of silicone oil as a control. With the ubiquitous nature of organosilicons (food containers, syringes, etc.), we hypothesized that baseline silicon levels could be detected in tissues of cadavers without silicone breast augmentation. Ten cadavers were examined. Tissue samples were derived from subcutaneous fat, nipple, breast tissue, liver, spleen, and axillary nodes. Nine of 10 cadavers had silicon levels in various tissues. Measurements were performed by direct current atomic emission spectroscopy. The baseline data were compared with those from four augmented patients who underwent capsulectomies and implant removal. Silicon levels were fivefold higher in the augmented patients than in the nonaugmented cadavers. No difference in levels was noted if the patient had an intact or ruptured implant and/or was symptomatic versus asymptomatic for immunologic disease. This study was designed to measure baseline silicon levels in the normal population. It also has established an accurate level of measurement of tissue silicone.

Aged↗
PubMed1994

Immunotoxicity of 180 day exposure to polydimethylsiloxane (silicone) fluid, gel and elastomer and polyurethane disks in female B6C3F1 mice.

Millions of people have been exposed to silicones which are present in consumer goods such as cosmetics and toiletries, processed foods and household products. In addition, silicones have been used extensively in medical practice as a lubricant in tubing and syringes, and as implantable devices. A silicone widely used in medical practice is polydimethylsiloxane. This study was undertaken to determine the immunotoxicologic potential of long term exposure to the principal constituents of breast implants: silicone fluid, silicone gel and silicone elastomer. An alternative covering for devices containing silicone gels, polyurethane, was also included in the study. Silicone fluid and gel were injected subcutaneously into female B6C3F1 mice (1 ml/mouse) and 6 mm disks of silicone elastomer or polyurethane were implanted subcutaneously. There were no treatment-related deaths or overt signs of toxicity during the 180 day exposure. None of the tested materials had notable effects on body or organ weights, erythrocytes or leukocytes in the blood, blood chemistries such as alanine aminotransferase, urea nitrogen, glucose, albumin or total protein, or serum CH 50 or C3 levels. The cellularity of the bone marrow and responses to CSF-GM and CSF-M were normal. The tested silicones and polyurethane marginally reduced the level of Ig+ cells in the spleen but did not consistently alter the distribution of T cell surface markers. The antibody response to sheep erythrocytes was not markedly altered, nor were proliferative responses to concanavalin A, phytohemagglutinin, lipopolysaccharide or allogeneic cells. Reticuloendothelial function was normal, as was phagocytosis of chicken erythrocytes and Covaspheres by adherent peritoneal cells. Natural killer cell activity was depressed in all silicone treatment groups and in mice implanted with polyurethane. No silicone or polyurethane treatment group displayed altered susceptibility to a challenge with Listeria monocytogenes, Streptococcus pneumoniae or the B16F10 tumor. The only consistent effect of 180 day exposure to silicone materials or polyurethane was a modest depression of natural killer cell activity.

Animals↗
PubMed2005

An all-silicon Raman laser.

The possibility of light generation and/or amplification in silicon has attracted a great deal of attention for silicon-based optoelectronic applications owing to the potential for forming inexpensive, monolithic integrated optical components. Because of its indirect bandgap, bulk silicon shows very inefficient band-to-band radiative electron-hole recombination. Light emission in silicon has thus focused on the use of silicon engineered materials such as nanocrystals, Si/SiO2 superlattices, erbium-doped silicon-rich oxides, surface-textured bulk silicon and Si/SiGe quantum cascade structures. Stimulated Raman scattering (SRS) has recently been demonstrated as a mechanism to generate optical gain in planar silicon waveguide structures. In fact, net optical gain in the range 2-11 dB due to SRS has been reported in centimetre-sized silicon waveguides using pulsed pumping. Recently, a lasing experiment involving silicon as the gain medium by way of SRS was reported, where the ring laser cavity was formed by an 8-m-long optical fibre. Here we report the experimental demonstration of Raman lasing in a compact, all-silicon, waveguide cavity on a single silicon chip. This demonstration represents an important step towards producing practical continuous-wave optical amplifiers and lasers that could be integrated with other optoelectronic components onto CMOS-compatible silicon chips.

Journal Article↗
PubMed1995

Induction of type II collagen arthritis in the DA rat using silicone gels and oils as adjuvant.

The relative safety (or otherwise) of silicone gel filled breast implants remains a controversial issue. The Dark Agouti (DA) rat has been shown recently to have a high susceptibility for developing arthritis. This study determined the arthritogenic potential of silicone gel, silicone oil, and the low molecular weight octamethylcyclotetrasiloxane (D4), by either mixing it with bovine collagen II (BII) or by injecting silicone gel alone in DA rats. Three separate experiments were performed using 110 female DA rats with 10 rats per treatment group. The incidence of collagen induced arthritis was as follows: Experiment I (6 micrograms BII)- PBS = 0/10, silicone gel = 4/10, and IFA = 8/9; Experiment II (125 micrograms BII)- PBS = 0/10, silicone gel = 7/10, IFA = 10/10, 1,000 cs silicone oil = 3/10, D4 = 0/10, and 1% D4 in 1,000 cs silicone oil = 1/10; Experiment III (adjuvant alone)-IFA = 8/10, silicone gel = 0/10. Anti-BII antibodies were formed in most of the rats treated with either silicone gel or IFA mixed with BII and these groups of rats showed a positive DTH reaction. The PBS treated rats were negative for both anti-BII antibodies and DTH reaction. Silicone gel taken from a commercial breast implant thus is capable of mediating collagen induced arthritis in the DA rat. However, silicone gel alone does not appear to be arthritogenic.

Adjuvants, Immunologic↗
PubMed1997

From cadavers to implants: silicon tissue assays of medical devices.

A plethora of data has been used to condemn and defend the role of silicone and its association with "adjuvant disease." In the ongoing attempt to enhance our knowledge, we have chosen to identify tissue silicon levels in patients with saline implants or tissue expanders. We have compared these levels with tissue samples from a variety of patients with and without medicinal silicone devices from both the northeast and southwest United States over a 4-year period. All specimens were harvested by a "no touch" technique, non-formalin fixed, frozen, and shipped to an independent toxicology laboratory for analysis. Inductively coupled plasma atomic emission spectroscopy was used to obtain the tissue silicon measurements. Silicon tissue values in cadaveric tissue (n = 20 cadavers; n = 120 specimens) averaged 2.2 mcg/gm of tissue with undetectable silicon levels in over 50 percent of the specimens (range 0 to 45 mcg/gm; median = 0). Silicon levels surrounding port-a-catheter devices (n = 15 patients; n = 15 specimens) averaged 8.04 mcg/gm of tissue (range 0 to 41 mcg/gm; median = 0). Tissue levels in the capsules surrounding saline (n = 10 patients; n = 22 specimens) and silicone implants (n = 31 patients; n = 58 specimens) averaged 292 mcg/gm (range 0 to 1380 mcg/gm; median = 110) and 1439 mcg/gm (range 0 to 9800 mcg/gm, median = 490), respectively. Tissue levels, however, from distant sites (n = 22 specimens) in these same patients were equivalent to the cadaveric nonaugmented values (average = 3.2 mcg/gm; range 0 to 5.8 mcg/gm; median = 2.7). The results imply that there is a continuum of exposure to silicone medical devices based on the mechanical properties of silicone. The data seem to suggest that there may be a progression of measurable tissue silicon levels based on the amount of environmental or device-related silicone exposure a person has over his or her lifetime. It is our hope that these levels will serve as a baseline for our continuing knowledge of implantable medical devices.

Adjuvants, Immunologic↗
PubMed1999

The influence of silicone implantation on murine lupus in MRL lpr/lpr mice.

OBJECTIVE: The use of silicone breast implants has been implicated in the development of autoimmune connective tissue diseases including systemic lupus erythematosus (SLE). We examined the influence of implanted silicones in MRL lpr/lpr and MRL +/+ mice, to determine whether silicone increases autoimmunity and exacerbates experimental lupus. METHODS: Mice were implanted with either silicone gel or silicone oil (polydimethylsiloxane; PDMS), while saline injected mice were used as controls. Proteinuria levels, palpation of lymphadenopathy, serum autoantibodies, circulating cytokines, and weight change were monitored for 18 weeks, when terminal glomerulonephritis was evaluated by histopathological techniques. Proteins were extracted from the surface of recovered implants, and the composition and immune reactive status of the silicone-binding proteins (SBP) were investigated. RESULTS: No adverse influence of silicone gel or silicone oil on the clinical aspects of lupus was observed. However, anti-DNA antibodies were significantly increased in MRL mice implanted with silicone gel compared to the control animals, and rheumatoid factor titers were modestly increased in implanted MRL lpr/lpr mice. Serum cytokine levels were influenced by silicone implantation in MRL lpr/lpr mice (but not MRL +/+ mice), with interleukin 1 (IL-1) levels increased in gel implanted animals and IL-2 levels elevated in PDMS (silicone oil) implanted mice. Different SBP were detected on implants recovered from MRL lpr/lpr mice compared with MRL +/+ mice, and Western blotting revealed the presence of strong autoantibodies to SBP in sera from MRL lpr/lpr mice, but not MRL +/+ mice. CONCLUSION: These findings suggest that silicone implantation may influence immunological responses during murine lupus, including the provocation or exacerbation of autoantibodies. However, these immune modifications did not appear to influence the clinical variables of this experimental lupus model.

Animals↗
PubMed2006

Silicon gel sheeting for preventing and treating hypertrophic and keloid scars.

BACKGROUND: Keloid and hypertrophic scars are common and are caused by a proliferation of dermal tissue following skin injury. They cause functional and psychological problems for patients, and their management can be difficult. The use of silicon gel sheeting to prevent and treat hypertrophic scarring is still relatively new, and started in 1981 with treatment of burn scars. OBJECTIVES: To determine the effectiveness of silicon gel sheeting for: (1) prevention of hypertrophic or keloid scarring in people with newly healed wounds (e.g. post surgery); (2) treatment of established scarring in people with existing keloid or hypertrophic scars. SEARCH STRATEGY: Trials were identified from searches of the Cochrane Wounds Group Specialised Register (searched September 2005), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 3, 2005); MEDLINE (1989 to June 2002); EMBASE (1988 to May 2002); CINAHL (1982 to May 2002) and reference lists of articles and relevant reviews. The major supplier of silicon gel sheeting (Smith and Nephew) was approached for details of unpublished, ongoing and recently published trials. SELECTION CRITERIA: Any randomised or quasi-randomised controlled trials, or controlled clinical trials comparing silicon gel sheeting for prevention or treatment of hypertrophic or keloid scars against no treatment, placebo, or any other treatment type except surgery. DATA COLLECTION AND ANALYSIS: All relevant trials were assessed for methodological quality. Data were extracted independently by both reviewers using a standardized form, and the results cross-checked. All trials, meeting the selection criteria were assessed for methodological quality. MAIN RESULTS: Thirteen trials, involving 559 people, ranging in age from 2 to 81 years, were included in the review. The trials compared adhesive silicon gel sheeting with control; non-silicon gel sheeting; silicon gel plates with added Vitamin E; laser therapy; triamcinolone acetonide injection, and non-adhesive silicon gel sheeting. In the prevention studies, when compared with a no treatment option; whilst silicon gel sheeting reduced the incidence of hypertrophic scarring in people prone to scarring, (RR 0.46, 95% CI 0.21 to 0.98) these studies were highly susceptible to bias. Silicon gel sheeting produced a statistically significant improvement in scar elasticity, (RR 8.60, 95% CI 2.55 to 29.02), but again these studies were highly susceptible to bias. AUTHORS' CONCLUSIONS: Trials evaluating silicon gel sheeting as a treatment for hypertrophic and keloid scarring are of poor quality and highly susceptible to bias. There is weak evidence of a benefit of silicon gel sheeting as a prevention for abnormal scarring in high risk individuals but the poor quality of research means a great deal of uncertainty prevails.

Cicatrix, Hypertrophic↗
PubMed1986

Silicon as an essential trace element in animal nutrition.

Within the last decade silicon has been recognized as participating in the normal metabolism of higher animals and as being an essential trace element. Silicon is found to perform an important role in connective tissue, especially in bone and cartilage. Bone and cartilage abnormalities are associated with a reduction in matrix components, resulting in the establishment of a requirement for silicon in collagen and glycosaminoglycan formation. Silicon's primary effect in bone and cartilage is on the matrix, with formation of the organic matrix appearing to be more severely affected by silicon deficiency than the mineralization process. Additional support for silicon's metabolic role in connective tissue is provided by the finding that silicon is a major ion of osteogenic cells and is present in especially high concentrations in the metabolically active state of the cell; furthermore, silicon reaches relatively high levels in the mitochondria of these cells. Further studies also indicate that silicon participates in the biochemistry of the subcellular enzyme-containing structures. Silicon also forms important interrelationships with other elements. Although it is clear from the body of recent work that silicon performs a specific metabolic function, a structural role has also been proposed for it in connective tissue. A relationship established between silicon and ageing probably relates to glycosaminoglycan changes.

Animals↗
PubMed1993

Cellular responses to silicone and polyurethane prosthetic surfaces.

Prosthetic devices composed of silicone or polyurethane are commonly used in surgery. These devices elicit a soft tissue reaction which may frequently be complicated by capsule formation. Histologically the capsule comprises both cellular (fibroblasts and endothelial cells (EC)) and matrix components (predominantly collagen type I). We hypothesized that the function of the cellular elements is altered by exposure to prosthetic materials and that this alteration contributes to capsule formation. To test this hypothesis, we utilized specific in vitro assays of cell function (attachment, proliferation, matrix gel contraction), which closely mimic in vivo cellular events, in order to define the responses of EC and fibroblasts to prosthetic surfaces (foam polyurethane, flat silicone, and textured silicone). Morphologic changes were evaluated by scanning electron microscopy (SEM). Attachment of both cell types to all prosthetic surfaces was significantly decreased compared to control (HUVEC: control, 55 +/- 1; foam polyurethane, 19 +/- 4*; flat silicone, 25 +/- 3*; textured silicone, 36 +/- 1*; fibroblast: control, 93 +/- 6; foam polyurethane, 21 +/- 4*; flat silicone, 57 +/- 5*; textured silicone, 44 +/- 5* (*P < 0.05 = significant; units, percentage spread)). Fibroblast proliferation was significantly decreased on foam polyurethane (0.1 +/- 0.03*) and textured silicone (0.18 +/- 0.05*), but not on flat silicone (0.79 +/- 0.2; control = 0.96 +/- .2). In contrast, HUVEC proliferation was significantly decreased on both silicone surfaces but not on polyurethane (units, cpm/cell; control, 0.26 +/- 0.05; foam polyurethane, 0.15 +/- 0.05; flat silicone, 0.08 +/- 0.03*; textured silicone, 0.02 +/- 0.01*).(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Adhesion↗
PubMed2001

Combined use of partially fluorinated alkanes, perfluorocarbon liquids and silicone oil: an experimental study.

BACKGROUND: Partially fluorinated alkanes (FALKs) are a new class of substances which can be used in vitreoretinal surgery as an intraoperative tool and as a long-term tamponade. The aim of this in vitro study was (1) to investigate the solubility of FALKs in silicone oil during direct exchange, (2) to study their combined use and solubility in PFCLs, (3) to evaluate their lipophilic properties and (4) to investigate the possibility of preparing "heavy silicone oil". METHODS: (1) Four different FALKs (F6H6, F6H8, O44 and O62) were directly exchanged with silicone oil (5,000 mPas). The dissolved amount of fluorocarbons in the removed silicone oil was determined by gas chromatography and by gravimetry. Furthermore, the diffusion phenomena during the exchange process were studied. (2) The behaviour of FALKs in PFCLs was investigated and the solubility of the resulting mixtures in silicone oil was measured. (3) The solubility of FALKs and PFCLs in native olive oil was analysed. (4) Different FALKs were added to silicone oil and measurements of the resulting specific gravity and the viscosity were performed. RESULTS: (1) FALKs dissolved in silicone oil up to the following values: F6H6=45 m%, F6H8=54 m%, 044=100 m%, O62=18 m%. (2) FALKs dissolved in PFCL, thereby changing the physicochemical properties of PFCL depending on the type of FALK and ratio used. (3) The lipophilic properties of FALKs and PFCLs could be characterized by their dissolution in native olive oil (F6H8=23.4 m%, 044=16.7 m%, F6H6=12.3 m%, 062=5.3 m%, PFD=1.1 m%, PFO=0.6 m%). (4) It was possible to prepare "heavy silicone oil" e.g. by adding 30 vol% F6H8, resulting in a specific gravity of 1.08 g/ml, or by adding 80 vol% 044, resulting in a specific gravity of 1.25 g/ml, but decreasing the viscosity of the mixtures dramatically. CONCLUSION: (1) If FALKs are used as an intraoperative tool, a direct exchange with silicone oil should be avoided owing to their capacity to dissolve in silicone oil, resulting in a mixture with unpredictable properties. (2) A combined use with PFCLs and silicone oil is possible, if the right ratio is chosen. (3) The solubility of FALKs in native olive oil may be an indicator for their tissue penetration and may render feasible their use as a long-term tamponade. (3) "Heavy silicone oil" preparation using FALKs is possible, but the mixture needs further evaluation in terms of emulsification, mobilization of oligosiloxanes, tissue penetration and long-term stability.

Drug Combinations↗
PubMed1994

Immunotoxicity of silicone: implications of oxidant balance towards adjuvant activity.

A variety of mechanisms can be proposed to explain the potential effects of silicone and silicone by-products on the immune response. In this paper, we discuss information on the chemistry of silicon and silicone gels/elastomers, and the manufacture of silicone breast implants as they pertain to the bioreactivity of silicone. Moreover, with reference to silicone-mediated human adjuvant disease, an overview of experimental adjuvant-induced arthritis is presented; comparisons with graft-versus-host disease and chemically induced autoimmunity then follow. Particular attention is paid to similarities in the characteristics of silicone and classic lipid adjuvants. For example, macrophage activation is presumed to be a central event in silicone-induced autoimmunity. Since those genes uniquely expressed in macrophages activated by plastic adherence are similar to those induced by lipopolysaccharide, adherence to silicone rubber may initiate an inflammatory response by the same mechanism. Macrophage effects would also include the erosion of implants through the generation of oxidants and localized pH changes. The degradation products of silicone are also implicated in the adjuvant effects of silicone implants. There is evidence to suggest that oxidants produced by inflammatory cells preferentially inactivate CD8+ suppressor T cells. This could then lead to an inflammatory state, perhaps through oxidant-induced transcription factors such as NF-kB, resulting in a long-term pro-oxidant imbalance that manifests itself as a breakdown in immunological self-tolerance. The authors hypothesize that autoreactivity following oxidant stress evolved to enhance inflammatory repair mechanisms after tissue, cell or molecular damage by oxidants.

Animals↗
PubMed1998

Early peripheral nerve healing in collagen and silicone tube implants: myofibroblasts and the cellular response.

Injuries to peripheral nerves innervating a limb cause paralysis, and can necessitate amputation. The inability of the nerves to regenerate spontaneously and the limitations of autograft procedures led to the development of treatments involving insertion of the nerve ends into prosthetic tubular devices. Previous work showed that 'entubulation' of the nerve ends in a silicone tube containing a specific porous, resorbable collagen-GAG (CG) copolymer, serving as an analog of extracellular matrix, improved regeneration compared to an empty silicone tube. However, long-term treatment with silicone tubes produced constriction that caused partial degradation of the regenerated axons; for this and other reasons, implementation of a nondegradable tube may require a second surgical procedure for removal. In this study the silicone tube was replaced with porous and non-porous collagen tubes in order to produce fully degradable devices. CG-filled collagen tubes and controls (CG-filled silicone tubes and empty collagen and silicone tubes) were implanted in a 10-mm gap in the rat sciatic nerve, with three rats in each group. The regeneration was evaluated after six weeks using light microscope images of cross sections of the nerve that were digitized and analyzed. Histograms of the diameters of the axons were generated and compared. The cellular response to the implanted biomaterials was assessed histologically, and immunohistochemistry was performed using an antibody to alpha-smooth muscle actin in order to determine the presence of myofibroblasts (contractile cells). Axonal regrowth was comparable in porous collagen, non-porous collagen, and silicone tubes filled with a CG matrix. These results support the implementation of a degradable collagen tube in place of a silicone device. Confirming earlier work, regeneration through the silicone and collagen tubes was enhanced by the CG copolymer, compared to empty tubes. A notable finding was a continuous layer of myofibroblasts on the surfaces of all of the six silicone tube prostheses, but on the inner surface of only one of six collagen tubes (Fisher's exact tests; P < 0.01). This is the first report of contractile capsules around silicone tubes, and supports the use of degradable collagen tubes in peripheral nerve regeneration. Macrophages were found bordering both the silicone and collagen tubes, and in the case of the collagen tubes, appeared to be participating in the regulation of the tubes.

Absorbable Implants↗
PubMed2002

Is prophylactic 360-degree laser retinopexy protective? Risk factors for retinal redetachment after removal of silicone oil.

OBJECTIVES: To identify risk factors for retinal redetachment after removal of silicone oil. To determine the effectiveness of prophylactic laser in preventing retinal redetachment after removal of silicone oil. DESIGN: A nonrandomized retrospective comparative interventional trial. PARTICIPANTS: Three hundred seventy-six patients undergoing vitrectomy with silicone oil tamponade for rhegmatogenous retinal detachment at one institution over a 4-year period. Two hundred eighty-seven patients with fully attached retinas subsequently underwent removal of silicone oil. One hundred thirty-eight cases had undergone prophylactic 360 degrees laser retinopexy before removal of silicone oil, either at the time of their final retinal reattachment procedure (n = 36) or as a separate supplementary procedure (n = 102). METHODS: A retrospective case note review was performed to identify clinical and demographic factors associated with increased or reduced odds of retinal redetachment after removal of silicone oil. Both univariate and multiple variable analysis were used to identify significant risk factors. MAIN OUTCOME MEASURES: Incidence of retinal redetachment after removal of silicone oil. RESULTS: Median follow-up after removal of silicone oil was 272 days. Three hundred sixty-degree prophylactic laser retinopexy was associated with a reduction from 26% to 14% in the incidence of redetachment after removal of silicone oil (adjusted odds ratio, 0.42; 95% confidence interval, 0.22-0.78; P = 0.006). Patients requiring further retinal reattachment surgery after their first oil procedure were at twice the odds of re-detachment after oil removal (adjusted odds ratio, 2.10; 95% confidence interval, 1.03-4.26; P = 0.04). CONCLUSIONS: The need for retinal reattachment surgery subsequent to a first silicone oil procedure was associated with twice the odds of retinal redetachment after removal of silicone oil. Prophylactic laser retinopexy may halve the incidence of retinal redetachment after removal of silicone oil.

Adolescent↗
PubMedDate not supplied

Use of perfluorocarbon liquids, silicone oil, and 5-fluorouracil in the management of experimental PVR.

PURPOSE: To evaluate the toxicity and efficacy of 5-fluorouracil (5-FU) in combination with perfluoroperhydrophenanthrene (Vitreon), silicone oil, or a combination of silicone oil and Vitreon in a ratio of 3:2 in the management of experimental proliferative vitreoretinopathy (PVR). METHODS: Toxicity study. Seventy rabbit eyes underwent vitrectomy followed by intravitreal injection of 5-FU in doses of 800, 400, or 200 microg: Group 1, 5-FU alone; Group 2, 5-FU plus 1 mL Vitreon; Group 3, 5-FU plus 1 mL silicone oil; Group 4, 5-FU plus 0.6 mL silicone oil and 0.4 mL Vitreon; Group 5, 0.6 mL silicone oil plus 0.4 mL Vitreon. Electroretinography was performed preoperatively and 8 weeks postoperatively before the animals were sacrificed. Efficacy study. Seventy-two rabbit eyes underwent vitrectomy and were injected intravitreally with 100,000-200,000 retinal pigment epithelial cells to induce PVR. Groups were injected with 200 microg 5-FU alone or with 1 mL silicone oil, 1 mL Vitreon, or a combination of 0.6 mL silicone oil and 0.4 mL Vitreon. Others were given only 1 mL Vitreon or 1 mL silicone oil. The animals were followed for 8-12 weeks; PVR was graded using Fastenberg's system. RESULTS: Toxicity study. Eyes given 200 microg 5-FU, silicone, and Vitreon showed mild inflammation and vitritis which resolved in 1 week; the dose was nontoxic by electroretinography and histopathology. Doses of 400 and 800 microg 5-FU were toxic. Efficacy study. Clinical severity of PVR was less in the groups which received 5-FU plus vitreous substitutes when compared to the control groups at all time points. The lowest incidences were in groups given 5-FU plus Vitreon or 5-FU plus Vitreon and silicone oil: 33.33% and 11.11%, respectively. CONCLUSIONS: A dose of 200 microg 5-FU with silicone oil and Vitreon combined was nontoxic to the rabbit retina. The combination of 5-FU, Vitreon, and silicone oil showed significant efficacy in the prevention of experimental PVR.

Animals↗
PubMed2003

Visual outcomes of silicone oil versus gas tamponade for macular hole surgery.

PURPOSE: To determine the effectiveness of silicone oil versus gas tamponade to treat macular holes. METHODS: A retrospective review of patients who underwent macular hole repair with either silicone oil or gas tamponade. RESULTS: Data collected from 66 eyes from a retina only practice (Retina and Vitreous of Texas) were reviewed to assess visual outcomes of surgery with silicone oil versus 14% C3F8 gas tamponade. 21 eyes were non-randomized to silicone oil tamponade and 45 eyes underwent gas tamponade. The average overall follow-up time was 11.8 months. Stage 2 holes constituted 9% of the holes; stage 3 and 4 made up 75%; recurrent holes were 11%; and 5% were traumatic holes. Of the macular holes not treated previously, 81.3% (13 of 16) were sealed successfully with silicone oil tamponade while 83.7% (36 of 43) of the gas-treated eyes were sealed. The overall primary closure rate was 83.1% (49 of 59). The pre-operative decimal visual acuity was 0.104 (20/192) for the silicone oil group and 0.193 (20/104) for the gas-treated group. The post-operative decimal visual acuity at 1 year was 0.208 (20/96) for the silicone oil group and 0.453 (20/44) for the gas-treated group. The reopening rate for the silicone oil group was 14% (3 of 21) and 9% (4 of 45) for the gas-treated group. The need for cataract surgery post macular hole repair was 36% (4 of 11 phakic patients) for the silicone oil group and 61% (17 of 28 phakic patients) for the gas-treated group. CONCLUSIONS: With short-term follow-up silicone oil tamponade and gas tamponade are both successful in anatomic closure of macular holes. In eyes with macular holes surgically repaired with gas tamponade significant improvements in visual acuity are seen more frequently than eyes treated with silicone oil tamponade. Toxicity of silicone oil to the retinal pigment epithelium and/or photoreceptors may play a role in these results.

Aged↗