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At least 721 records · Page 40Linked to original sources
PubMed1998

Influence of silicone (PDMS) surface texture on human skin fibroblast proliferation as determined by cell cycle analysis.

In vivo biocompatibility of soft-tissue implants is often hampered by development of capsules that eventually might contract and impair implant function. It has been shown that capsule formation can be significantly reduced by using materials with textured surface elements in the micron range. In this study the interaction of human fibroblasts with silicone surfaces was analyzed using cell cycle analysis. Silicone was textured with 2, 5, and 10 microns wide grooves (2MU, 5MU, 10MU, respectively) or kept smooth (SMT). Cell cycle analysis was performed after staining of cells with propidium iodide. Cells proliferated on the fibronectin-preadsorbed silicone, as demonstrated by increased coverage and occurrence of subpopulations in the S and G2/M phase of the cell cycle. Cells on SMT went faster into the S phase than cells on textured silicones. Cells on 10MU showed less proliferation than cells on 2MU and 5MU. Besides the basic percentages of cells in the different cycle phases, DNA profiles were also influenced by incubation time and texture, especially with respect to the presence of hypodiploid populations and asymmetry of the G0/G1 peak. Finally scatter characteristics were influenced. 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay data did not reveal significant differences among the different samples. Fibronectin preadsorption of silicone only resulted in slightly higher MTT conversion. Cell cycle analysis proved to be a sensitive screening method for proliferation on the silicone surfaces and provided information beyond the normal G0/G1, S and G2/M subpopulations.

Biocompatible Materials↗
PubMed2004

Immunogenetic differences between Caucasian women with and those without silicone implants in whom myositis develops.

OBJECTIVE: To determine whether patients in whom myositis develops after they receive silicone breast implants have distinct clinical, serologic, and/or immunogenetic features compared with patients with myositis who do not have silicone implants. METHODS: A preliminary case series study was followed by a larger, independent, matched case-control study to evaluate women in whom myositis developed after they received silicone implants (MASI patients) compared with healthy women with silicone implants and women with myositis but without silicone implants (idiopathic inflammatory myopathy; IIM patients). RESULTS: In a preliminary study, 11 MASI patients differed from 76 IIM patients in having an increased frequency of HLA-DQA1*0102 (odds ratio [OR] 9.8, 95% confidence interval [95% CI] 1.77-96.79) and decreased frequencies of the myositis-associated risk factor DRB1*0301 (OR 0.1 [95% CI 0.002-0.63]) and its linked allele DQA1*0501 (OR 0.2 [95% CI 0.02-0.87]). A subsequent independent, matched case-control study revealed that although clinical features and autoantibodies did not differ significantly between the MASI and IIM groups, MASI patients again had decreased frequencies of DRB1*0301 (OR 0.2 [95% CI 0.07-0.72]) and DQA1*0501 (OR 0.2 [95% CI 0.08-0.84]) compared with IIM patients. Additional comparisons between MASI patients from both studies combined (n = 37) and a larger population of IIM patients (n = 453) suggested that HLA-DQA1*0102 may be uniquely associated with MASI (OR 2.6 [95% CI 1.25-5.46]). CONCLUSION: Women in whom inflammatory myopathy develops after they receive silicone implants constitute an immunogenetically distinct group of patients with myositis. These and other data suggest that autoimmune diseases as now defined may consist of multiple distinct entities, each of which is characterized by different genes and environmental exposures.

Adult↗
PubMed1988

Silicone rubber temporomandibular joint (TMJ) meniscal replacements: postimplant histopathologic and material evaluation.

Medical grade silicone rubber has long been considered a suitable meniscal replacement, but there has been increasing concern about migration of this material into adjacent tissues. The objectives of this study were to determine the definitive composition of tissue-incorporated material which is presumed by light microscopy to be silicone and to identify long term histopathologic sequelae of meniscal replacements. Adult female patients underwent meniscectomy and replacement with silicone rubber (Silastic) implants. After 12 to 18 months, recurrence of symptoms in 8% of these cases led to implant removal with excision of peri-implant fibrous pseudocapsules. Excised tissues, including one preauricular lymph node and implants were submitted for light microscopy, SEM, and energy dispersive x-ray microanalysis (EDX) for the identification of elemental composition, critical surface tension measurement, and internal reflection infrared spectroscopy. EDX revealed prominent peaks for silicon in both pseudocapsular and nodal tissues. Morphologic findings surrounding the long-term implants included foreign body reaction, synovitis, dystrophic calcification, fibrocartilaginous metaplasia, hyalinization, and scarring. Particulate silicone debris induced a pathologic response in the tissues and migrated to nodes. These findings suggest that periodic evaluation be performed over the life of such implants to rule out breakdown under function. These findings should intensify the search for improvements or replacements for silicone rubber as an interpositional material in the temporomandibular joint.

Calcinosis↗
PubMed2005

Preparation of cells cultured on silicon wafers for mass spectrometry analysis.

The distribution of specific atoms and molecules within living cells is of high interest in bio-medical research. Laser secondary neutral mass spectrometry (laser-SNMS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) detect atoms with high sensitivity and spatial resolution. The application of these methods to cultured cells requires special preparation techniques preserving morphological and chemical integrity of the living cells. The cells should, therefore, be grown on a conducting material preventing charging of the sample during ion bombardment. Silicon is currently used as the preferred support material for non-biological samples in mass spectrometry. This study investigates (1) the influence of silicon surfaces on cell growth and (2) the suitability of a sandwiched, rapid freezing method to analyse transmembrane ion gradients. Human melanoma cells were grown on silicon with polished or etched surfaces. Growth kinetics were studied using the Sulforhodamine-B assay. Number, shape, and morphology of the cells were assessed by epifluorescence microscopy of calcein AM- and DAPI-stained cells. Cells were subjected to rapid freezing, freeze-fracturing, and freeze-drying prior to analysis by TOF-SIMS and laser-SNMS. While cell numbers and morphology on the rough silicon wafers were impaired, morphology and growth kinetics of cells on polished silicon were identical to control cells on cell culture tested polystyrene. TOF-SIMS and laser-SNMS resulted in high-resolution elemental images and mass spectra. Measurement of the intracellular Na+ and K+ concentrations revealed a ratio as observed in living cells. In conclusion, culturing cells on polished silicon wafers followed by sandwiched, rapid freezing is an adequate preparation method to study intracellular ion distribution with mass spectrometry.

Cell Culture Techniques↗
PubMed1996

Comparative epitope mapping of antibodies to collagen in women with silicone breast implants, systemic lupus erythematosus and rheumatoid arthritis.

Previous work has shown that women with silicone gel breast implants have an increased frequency of autoantibodies to collagen types I and II. 70 women without a specific autoimmune disease, using criteria of the American College of Rheumatology, but who had silicone breast implants were studied for the presence of serum antibodies to native and denatured human types I and II collagen by ELISA. 82 women with systemic lupus erythematosus (SLE), 94 women with rheumatoid arthritis (RA), and 133 healthy controls were also studied. There was a high frequency of autoantibodies to collagen in each of the groups when compared to the healthy controls. The specificities of these antibodies were found to differ markedly when examined by immunoblotting using peptides derived by cyanogen bromide digestion of the collagens. Sera from women with silicone implants reacted with multiple peptides of type I collagen in an individual-specific manner, but sera from women with SLE or RA reacted weakly with a restricted range of peptides. Against type II collagen, sera from women with RA reacted strongly with multiple peptides, while sera from women with silicone implants or SLE reacted only weakly or not at all. The patterns of reactivity against collagens by sera from women with silicone implants suggest that silicone can act as an adjuvant to enhance the immunogenicity of type I collagen.

Adult↗
PubMed1987

Milk and blood levels of silicon and selenium status in bovine mastitis.

Milk and blood levels of silicon, selenium and the selenoenzyme glutathione peroxidase (GSH-Px) were measured in 20 healthy and 21 mastitic cows. In milk samples from healthy quarters the mean silicon concentration was 0.81 and in affected ones 0.39 ppm. In serum the mean silicon values were 1.63 and 1.02 ppm respectively. The selenium status was not altered but the level of erythrocyte GSH-Px was lowered in mastitic animals. Silicon is known to have marked effects on free radical formation, lipid peroxidation and macrophage activity. Its possible role in infection and inflammation is evaluated. Some of the functions of silicon may resemble those of selenium. The possibility of lowered levels of silicon and of the selenoenzyme in mastitis calls for experimentation with dietary or pharmaceutical supplementation of these trace elements.

Animals↗
PubMedDate not supplied

Ultrastructure of the anterior lens capsule after vitrectomy with silicone oil injection. Correlation of clinical and morphological features.

To clarify the mechanical difficulties experienced when performing anterior capsulorhexis in vitrectomized eyes filled with silicone oil. Five anterior lens capsules removed from eyes with a silicone oil history were submitted to light and electron microscopic analysis and then compared to two capsules from eyes with trauma history and seven capsules from eyes without silicone oil or trauma history. Comparable abnormalities of the inner and outer surface of the anterior lens capsule were consistently observed after silicone oil fill of the vitreous cavity or after traumatic impact to the lens: patches of multilayer epithelial cells with interspersed capsule material and connective tissue were observed on the posterior surface of the anterior lens capsule. The development of this anterior subcapsular tissue plaque is obviously influenced not only by the PVR process or by side effects of the surgical procedure but also by the silicone oil tamponade or a trauma history. The plaque can be considered primarily responsible for the increased mechanical resistance of the lens capsule in all eyes with silicone oil / trauma history examined in this study.

Cataract Extraction↗
PubMed1993

Silicon prevents post laminectomy epidural root adhesions. An experimental study in rats.

An experimental study was designed to test the efficacy of a silicon barrier around a nerve root in order to prevent post operative epidural root scar adhesions. In 32 Sprague-Dawley rats a lumbar nerve root was microsurgically exposed bilaterally. In 16 animals a silicon tube, prepared with a longitudinal cut along half of its wall, was placed around one nerve root, while the contralateral side served as control. In another group of 12 animals, an autologous subcutaneous fat graft was placed on the exposed root. A group of 4 animals served as the control group which had not been operated upon. No post operative neurological deficit was observed in any of the animals. All animals were sacrificed 60 days after the operation and a block of tissue including the nerve roots were resected bilaterally without removal of the silicon or fat graft. Longitudinal and transverse cuts of the roots were stained with Haematoxilin and Eosin and with Masson's trichrome collagen stain. The roots in the "unoperated" control group were clean of any scar tissue. In 13 out of 16 animals, silicon prevented scar formation around the root as opposed to scar adhesions around control root on the contralateral side and as compared to unoperated roots. In the silicon group, adhesions penetrated only through the longitudinal narrow cut edge of the tube. Fat did not prevent adhesions in 11 out of 12 animals. We conclude that a silicon barrier is an effective method preventing post operative epidural root scarring in rats.

Animals↗
PubMed1982

Complications after silicone injection therapy in aesthetic plastic surgery.

Silicone injection therapy plays a significant, but limited, role in soft tissue augmentation. It is confined only to a tissue defect, folds, and deep wrinkles of the face. It is important to use only a small amount of injectable silicone (1-2 ml) in one area of the face at a time. Massage is applied over the injected area for 5-6 minutes. The following side effects and complications are observed: diminished volume, descending of silicone fluid due to the gravity, and silicone granuloma formation. Liquid silicone should be available, for the time being, only to surgeons for experimental purposes, because of the danger of complications and abuse. In this experimental study, the author applied 1,677 silicone injections (only in the face).

Face↗
PubMed1990

Dermal and subdermal tissue filling with fetal connective tissue and cartilage, collagen, and silicone: experimental study in the pig compared with clinical results. A new technique of dermis mini-autograft injections.

The early reaction to the injection of silicone, collagen, and lyophilized heterologous fetal connective and cartilage tissues into the limiting zone deep dermis-superficial subcutaneous tissue was histologically examined in the pig and compared with clinical results. The inflammatory reaction to lyophilized heterologous fetal tissue is considerably more intense than that to collagen and silicone and lasts for several weeks. Therefore, it is not recommended for soft tissue filling in the face. Admitting an inferior antigenicity of fetal tissues, the authors suggest that enzymatically denaturalized collagen should be manufactured from heterologous fetal connective tissue, to be then further tested. The reaction of tissue to silicone and collagen is minimal. Silicone is preferred for dermal injections since in clinical experience it remains in the site of injection much longer. For subdermal injections, however, collagen is preferred. Based on experience with over 600 patients since 1958, the first author continues using liquid silicone. The lack of complications is probably a result of the fact that only small amounts (milliliters) of silicone were used in wrinkles or small depressions in the dermal layer and that from the beginning injection into the subcutaneous tissue was avoided. Since 1988 a new technique for the treatment of wrinkles and skin depressions with injections of dermal miniautografts has been used with satisfactory results.

Animals↗
PubMed1986

Temporary use of intraocular silicone oil in the treatment of complicated retinal detachment.

Complicated retinal detachments in 99 eyes were successfully managed by intraocular injections of silicone oil with or without pars plana vitrectomy. The silicone was then subsequently removed after panretinal photocoagulation. Any remaining anterior vitreous cortex near the vitreous base and/or preretinal proliferative tissue causing traction of the retina was also removed by a vitrectome or extracted by a hooked needle after the silicone-fluid exchange had been performed. The preretinal proliferation occurred in some cases even after silicone oil had been removed. Recurrent detachments were discovered in 8 of the 99 eyes and were managed successfully by reinjections of the silicone. Other silicone reinjections were required in two eyes with diabetic retinopathy and two nondiabetic eyes because of frequent rebleeding into the vitreous cavity.

Eye↗
PubMed1989

Silicone oil in the anterior chamber.

A total of 42 cases (42 eyes) with silicone oil in the anterior chamber after pars plana vitrectomy (PPV) and after silicone oil injection into the vitreous cavity (SIV) were analyzed. The main complications caused by silicone oil were corneal endothelial cell damage and secondary glaucoma. Specular microscopy showed decreased cell density, apparent pleomorphism of endothelial cells, and increased corneal thickness. In some cases, edematous and necrotic endothelial cells were found. The characteristic optical artifacts resulting from silicone oil coming into contact with the endothelium, such as a bright reflex, reversed pattern of illumination, and interference fringes, were also observed. There was a definite correlation between elevated intraocular pressure (IOP) and the presence of silicone oil in the anterior chamber; the IOP dropped significantly on removal of the oil. The treatment and prevention of conditions involving silicone oil in the anterior chamber are briefly discussed.

Adolescent↗
PubMed1986

Detection and localization of silicon and associated elements in vertebrate bone tissue by imaging ion microscopy.

The growing long bones from normal embryonic chicks and young rats have been examined in situ by imaging ion microscopy, a highly sensitive technique for elemental detection and localization. In tibial diaphyses from chick and rat, treated with anhydrous ethylene glycol, embedded in Spurr medium, and dry sectioned 1-2 microns thick, analyses revealed the presence of silicon, calcium, magnesium, carbon, and oxygen. Silicon localization was principally extracellular in the tissues. Comparison of single element maps of silicon and calcium indicated that silicon specifically appeared in putative uncalcified osteoid regions of tibiae. Detection and imaging of silicon by ion microscopy support results of earlier work by Carlisle, who demonstrated the element in osteoid of rat and mouse bone by electron probe microanalysis. The current data offer the possibility for characterizing more completely silicon interaction in vertebrate calcified tissues.

Animals↗
PubMed1997

Biochemical interactions among silicon, iron and ascorbic acid in the rat.

A 2 x 2 x 2 factorial experiment was conducted using two dietary levels each (mg/kg of diet) of silicon, 0 and 500; iron, 35 and 187; and ascorbic acid, 0 and 900, to identify biochemical interactions occurring among these nutrients. Supplemental silicon, in conjunction with the higher dietary-iron level, prevented the plasma-iron decreasing effect observed for the higher level of iron in the absence of silicon. In the absence of ascorbic acid, silicon also increased iron concentration in the liver. Lower growth of the silicon and iron-supplemented rats is believed to be a response to a subsequent iron-imposed aberration of copper or zinc metabolism. This is supported by decreased intestinal metallothionein, increased weights (g/100 g body weight) of liver, heart, and testes, and decreased packed-cell volume and hemoglobin concentration. The lower plasma-iron level associated with the higher level of dietary iron appeared to be an expression of the iron-imposed reduction of liver copper stores. Ascorbic acid decreased plasma-iron concentration and prevented the silicon-related increase in liver iron.

Animals↗
PubMed2005

The course of epiphora after failure of silicone intubation for congenital nasolacrimal duct obstruction.

BACKGROUND: One of the indications for dacryocystorhinostomy (DCR) in children with congenital nasolacrimal duct obstruction (CNLDO) is failure of silicone intubation. We evaluated the course of epiphora after failure of silicone intubation for CNLDO when DCR was not performed. METHODS: In a comparative cohort study carried out at a tertiary referral center, ten eyes of seven consecutive children who had failure of silicone intubation manifested as persistent epiphora over 2 months and whose parents refused DCR were followed up for an average of 50.4 months (range 33-70 months). Three lacrimal drainage systems of three other children who had failure of silicone intubation underwent uneventful DCR. RESULTS: In eight (80%) of the ten consecutive eyes with congenital nasolacrimal duct obstruction (six of the seven children, 86%), there was spontaneous complete resolution of the epiphora and normal dye disappearance test (DDT) at the end of the follow-up period. One child with Down's syndrome, allergic rhinitis, asthma and multiple site obstructions had improvement of symptoms but abnormal DDT. The epiphora in all three children who underwent DCR had disappeared by 6 months after surgery when the silicone tube was removed. No complications were noted during the follow-up. CONCLUSIONS: Epiphora can spontaneously resolve after failure of silicone intubation in CNLDO, and DCR should no longer considered be compulsory in such cases unless complications evolve.

Child, Preschool↗
PubMed2006

The combined use of perfluorohexyloctane (F6H8) and silicone oil as an intraocular tamponade in the treatment of severe retinal detachment.

BACKGROUND: The purpose of this study was to investigate the combined use of perfluorohexyloctane (F6H8) and 1,000-centistoke silicone oil as a long-term intraocular tamponade in the treatment of complicated retinal detachment. METHODS: Sixty consecutive eyes affected by complicated retinal detachment with (1) retinal breaks of the lower two quadrants and severe proliferative vitreoretinopathy, (2) inferior giant retinal tear, (3) penetrating trauma or (4) choroidal detachment underwent pars plana vitrectomy using a combined internal tamponade of F6H8 and silicone oil. The double filling (DF) was removed after 40-50 days. The anatomical outcome and the complications due to the DF are reported. RESULTS: Retinal reattachment was achieved in all but one patient. Thirty-eight (63%) eyes needed further surgery with silicone oil tamponade. Silicone oil was successfully removed in 22 eyes. Sixteen (27%) eyes had retained silicone oil at the last follow-up examination. One eye showed persistent retinal detachment despite further surgery. Main complications of the DF were recurrent retinal detachment of the upper retina in six (10%) eyes and membrane formation in 25 (42%) eyes. CONCLUSIONS: A combined internal tamponade of F6H8 and silicone oil may be a useful tool in the treatment of complicated retinal detachment involving the lower quadrants of the retina.

Adolescent↗
PubMed1998

Results of penetrating keratoplasty in bullous silicone oil keratopathy.

BACKGROUND: To evaluate the results of penetrating keratoplasty (PK) in bullous silicone oil keratopathy (BSK). MATERIAL AND METHODS: PK for BSK was performed in 13 patients, aged from 31 to 82 years. In all patients, pars plana vitrectomy (PPV) with silicone oil implantation (SOI) had been previously performed as the definitive surgery: for complicated retinal detachment with advanced proliferative vitreoretinopathy in 12 eyes and for diabetic traction detachment in one eye. Seven patients were monocular. All 13 eyes were aphakic and there was a long-lasting contact of silicone oil with the corneal endothelium. Before keratoplasty, each eye underwent between two and five operations, on average three, for retinal detachment or late complications of SOI. The interval between SOI and PK was from 11 to 79 months. The patients were followed up for 12-52 months. RESULTS: At the last follow-up examination, a clear graft was found in 6 out of 13 eyes (46%). The six clear grafts were found in the ten eyes where silicone oil had been removed before keratoplasty. The graft became opaque in all three eyes in which silicone oil had not been removed. Six out of seven eyes with failed grafts atrophied. Visual acuity improved in all six eyes with the clear graft from had movement preoperatively to 0.05-0.25. The decreased visual acuity was caused by irreparable damage to the macula, which resulted from high myopia, proliferative vitreoretinopathy or long-lasting detachment of the macula. CONCLUSIONS: PK in BSK was successful only in those eyes in which the attached retina enabled the removal of the silicone oil before the PK. The reattached retina and useful visual acuity before the development of BSK were the preconditions for functional success of the PK.

Adult↗
PubMed1989

Clinical trials of a new polytetrafluoroethylene-silicone graft.

A self-sealing polytetrafluoroethelene (PTFE)-silicone graft designed to be used early after implantation was placed in 30 end-stage renal disease patients. Thirty-five conventional PTFE grafts were used in the control group. All patients were followed for 1 year. In the PTFE-silicone graft group, median time for first use was 1 day after implantation. Conventional PTFE grafts were first used 2 to 4 weeks after implantation. Early punctures of the PTFE-silicone grafts (first 10 sessions), although more difficult to perform than late punctures, were not more difficult than punctures of conventional PTFE grafts. Late punctures in PTFE-silicone grafts were easier than conventional PTFE graft punctures. Bleeding after needle removal was significantly decreased after early and late punctures of PTFE-silicone grafts compared with conventional PTFE grafts (p less than 0.001). The PTFE-silicone graft can be used immediately after implantation, sparing patients additional access procedures for short-term dialysis. This results in less morbidity, decreased bleeding complications, shorter hospital stay, and a significant reduction in expenses.

Blood Vessel Prosthesis↗