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PubMed1999

[A study of vitrectomy for retinal redetachment with silicone oil retained].

OBJECTIVE: To evaluate the outcome of vitrectomy for retinal redetachment in eyes with silicone oil tamponade and investigate the indications and surgical techniques of this surgery. METHODS: A total of 17 eyes (17 cases), in which retinal redetachment developed after the management of silicone oil tamponade, underwent pars plana vitrectomy with silicone oil retained. Directed by endoilluminator, membrane peeling, membrane inside-cut, full thickness retinal incision, internal drainage, endolaser, removal of subretinal perfluorocarbon liquids and injection of additional silicone oil, etc. were performed to make retinal reattachment. RESULTS: 14 eyes achieved retinal reattachment in total 17 eyes (82.4%). During operation, silicone oil migrated into anterior chamber in 1 eye and into suprachoroidal space in 1 eye. There was 1 eye with vitreous hemorrhage and ocular hypertension postoperatively. Retinal reattachment was not achieved in 3 eyes. CONCLUSIONS: Vitrectomy with silicone oil retained is an effective management for retinal redetachment of eyes with silicone oil tamponade. The advantages of this method are economical and time-saving. But the surgeon should be well trained and competent with vitrectomy.

Adolescent↗

PubMed1999

Silicone oil tamponade combined with lensectomy preserving anterior lens capsule.

PURPOSE: To investigate the therapeutic effect and indication of silicone oil tamponade combined with lensectomy preserving anterior lens capsule. METHODS: Silicone oil tamponade combined with lensectomy preserving anterior lens capsule was performed in 33 cases (33 eyes) of high myopia, proliferative vitroretinopathy (PVR) D grade and giant retinal tear (GRT). 10 cases were only eye and 11 cases had harder nucleus of lens. The surgical methods included: 1. smashing lens nucleus and lensectomy preserving complete anterior capsule; 2. vitrectomy and membrane peeling; 3. usage of liquid perfluorocarbin or retinotomy for drainage; 4. silicone oil tamponade; 5. postoperative Nd; YAG laser for anterior capsulectomy. RESULTS: Follow-up time was 6 months or more in 29 cases. Total retinal reattachment was achieved in 22 cases, macular retinal reattachment in 5 cases. The visual acuity was 20/800 to 20/200 in 13 cases, 20/100 to 20/50 in 12 cases. Visual acuity was significantly improved in GRT group (P < 0.05). Complications included unexpected anterior capsule break intraoperatively, anterior capsule opacity, silicone oil emulsification and liquid perfluorocarbin remaining postoperatively. CONCLUSIONS: Silicone oil tamponade combined with lensectomy preserving anterior capsule was safe and can reduce the operative complications. The indications included: 1. GRT complicated with high myopia; 2. advanced PVR cases complicated with high myopia in which silicone oil must be used; 3. severe lens opacity cases in which silicone oil must be used; 4. complex retinal detachment of only eye.

Adolescent↗

PubMed2004

[Effects of soil available silicon on growth, development and physiological functions of soybean].

Soybean plants were planted in pots to investigate the effects of soil available silicon on their growth, development and physiological functions. When the content of soil available silicon was 55.1-202.8 mg.kg-1, the protease and lipase activities of germinating seed were increased with increasing soil available silicon content, amylase activity had no obvious change, and the respiration rate of seedlings was accelerated. The bioactivity of seed was increased, but the germination rate had no significant change. The photosynthesis rate, root activity, and nitrate reductase activity of soybean seedlings were enhanced, but the chlorophyll content in leaves had no significant change during seedling growth. The transpiration rate was decreased, while the water utilization efficiency and leaf water content were increased, and the capacity of drought-resistance was promoted. When the available silicon content was > 202.8 mg.kg-1, the abovementioned physiological functions had no significant changes. There was a positively linear relationship between the silicon content in soybean seedlings and the available silicon content in soil (r = 0.994). It could be concluded that the silicon absorbed from soil improved the physiological functions of soybean germinating seed and seedlings. As a result, the seed germination and seedlings growth rate were enhanced.

Germination↗

PubMed2004

Silicones used in permanent and semi-permanent hair dyes to reduce the fading and color change process of dyed hair occurred by wash-out or UV radiation.

Different kinds of silicones were incorporated directly into permanent and semi-permanent hair dyes. To ensure that the silicone was deposited to the hair fibers Si deposition was measured. Hair treated with a silicone free control or the silicone modified hair dyes was tested for color and lightness change (fading) by washing the treated tresses several times and measuring the color change. In a second experiment, hair treated with permanent hair dye was treated with UV radiation to show if silicones can reduce the color change initiated by UV light. The influence of the silicones to dry combing forces of permanent dyed hair untreated and treated with UV was also investigated. The tests showed that dimethiconol/dimethicone mixtures can reduce the washout of hair colorant clearly and silicone resins like trimethylsiloxysilcate or propylphenylsilsesquioxane are able to decrease the color change occurred by UV radiation in dyed hair.

Colorimetry↗

PubMed2005

[Intraocular pressure values following vitrectomy with silicone oil tamponade].

Secondary glaucoma is a relatively common complication after pars plana vitrectomy and silicone oil injection for repair of complex retinal detachment. The aim of this study was to evaluate the influence of silicone oil tamponade on intraocular pressure elevation and to identify the mechanism of this elevation. The study included 45 eyes of 45 patients who had undergone pars plana vitrectomy and silicone oil tamponade for repair of complex retinal detachment. Ophthalmic examination was performed before vitrectomy, and one and six months after vitrectomy. The increase in intraocular pressure was measured one month postoperatively in 37.77% of patients. The mechanism of intraocular pressure increase was silicone oil emulsification in 52.98%, closure of Ando's iridectomy in 23.54%, and idiopathic angle closure glaucoma in 23.54% of patients with elevated intraocular pressure. After silicone oil removal, elevated intraocular pressure persisted in 7 (15.55%) patients; in 5 patients it was controlled medically, while two patients underwent glaucoma surgery. Six months postoperatively 3 patients developed secondary neovascular glaucoma due to the prolipherative ischemic disease. Elevation of intraocular pressure following vitrectomy with silicone oil tamponade had a temporary effect, as it did not lead to permament intraocular pressure elevation but regressed after silicone oil removal from the eye.

Glaucoma↗

PubMed1992

Macrophage interleukin 1 response to injected silicone in a rat model.

Observations of silicone granuloma formation and migration of silicone to regional lymph nodes have indicated a need for more research into the possible immunological responses to silicone. The present study was undertaken to assess the effect of injected silicone particles on the ability of splenic macrophages to produce interleukin 1 (IL-1) and to determine the relative quantities produced. Lewis rats were divided into 4 groups: Group 1 animals (n = 3) were injected subcutaneously with sterile saline (2.5 ml) and served as control animals; Group 2 animals (n = 3) also served as control subjects, but macrophages isolated from these animals were exposed to lipopolysaccharide (LPS); Group 3 animals (n = 3) were injected subcutaneously with Freund's complete adjuvant (FCA) (2.5 ml) to serve as FCA control animals; and Group 4 animals (n = 3) received a subcutaneous injection of a sonicated slurry of equal parts FCA and silicone (2.5 ml each). IL-1 production was not significantly increased in splenic macrophages from animals exposed to the silicone slurry (p greater than 0.20) 8 months after injection as compared with control animals or animals given FCA alone. Macrophages exposed to LPS, a known mitogen, had significantly elevated IL-1 production. Subcutaneously injected silicone particles did not elicit an increase in IL-1 production in rat macrophages.

Animals↗

PubMed2006

[Comparative study of nanosized and microsized silicon dioxide on spermatogenesis function of male rats].

OBJECTIVE: To compare the effects of nanosized and microsized silicon dioxide on spermatogenesis function of male rats exposed by inhalation. METHODS: 45 male rats were randomly divided into control group and four experimental groups which were exposed by 100 mg/m3 or 300 mg/m3 nanosized and microsized silicon dioxide in inhalation chambers 2 hours every other day. Age-matched rats were exposed to room air with the same condition and served as controls. 65 days later, the testicular and epididymal viscera coefficients, the quantity and quality of sperm were examined and the histopathological assessment was done. The changes in biochemical parameters in serum and testes were also measured. RESULTS: Nanosized silicon dioxide could induce histopathological changes of testes in rats, and the effect was higher than that of microsized particles at the same concentration. Nanosized silicon dioxide could reduce the sperm counts of rats and the testicular LDH-C4 activities, increase MDA levels in the testes and the effect was higher than that of microsized particles at the same concentration. Nanosized silicon dioxide could lead to the reduction of sperm motility, testicular LDH-C4 activities and 8-hydroxydeoxyguanosine (8-OHdG) concentration in serum elevation in particles-exposed rats compared with the control animals, but there are no significant difference compared with that of microsized particles at the same concentration. CONCLUSION: The present findings suggest a different effect of impairment of sperm production and maturation induced by inhalation of nanosized and microsized silicon dioxide, and nanosized silicon dioxide exerted more severe reaction.

Animals↗

PubMed1990

[The effect of filler content on properties of polyaddition-type silicone impression material].

The effect of quartz filler content on viscosity, dynamic viscoelasticity and tensile stress of polyaddition-type silicone impression materials were investigated. A hydrogen polydimethylsiloxane (H-silicone) and two vinyl polydimethylsiloxane (V-silicone) silicone prepolymers were prepared. Quartz fillers were mixed to them at contents between 0 and 50% by weight. The viscosity of these rubber compounds and mechanical properties of set materials were measured by a cone and plate viscometer, the dynamic shear test and the tension test, respectively. Viscosity eta storage modulus G' and tensile stress sigma increased with the amount of filler increase. G' and sigma were decreased by use of a V-silicone prepolymer which had a high average molecular weight and the material was more flexible. This suggests that the characteristics of the silicone prepolymer greatly affect the mechanical properties of the impression materials. Therefore, the appropriate molecular design for silicone prepolymer and reasonable filler content should be considered to make impression materials that have suitable properties for clinical use.

Dental Impression Materials↗

PubMed1990

Silicon measurement in serum and urine by direct current plasma emission spectrometry.

Elemental silicon, present as soluble silicic acid in serum and urine, has been measured by direct current plasma emission spectrometry. The method is precise and accurate, yields a standard curve that is linear up to 1000 mumol/L, and requires only a simple dilution in 10 mL/L HNO3. No spectral or background interferences have been observed from serum or urine; the absolute detection limit for silicon was 0.5 mumol/L. Silicon concentrations in serum increase by up to 20-fold in patients with chronic renal failure on hemodialysis, an increase apparently related to dietary silicon intake. No relationship with aluminum was observed in hemodialysis patients, with or without aluminum toxicity. In the undialyzed patient with chronic renal failure, the concentrations of silicon in plasma increased with decreasing glomerular filtration rate. This increase may protect renal-failure patients from possible aluminum toxicity by promoting formation of the relatively inactive aluminosilicate complex. Silicon concentrations in urine of healthy individuals exceed their serum concentrations by 20- to 100-fold. Silicon excretion in patients with renal stones was not different from that in healthy controls and showed no relationship with calcium and (or) oxalate excretion.

Aluminum↗

PubMed1989

[An experimental study of the measuring system of the mean film thickness of white silicone through image analysis].

Clinically, the fitness test of a denture base employing white silicone has been widely used, and there are several methods for assessing the results. However, none of the conventional methods of assessment are completely objective or quantitative. For solving these problems, a new system has been developed for measuring the mean film thickness of white silicone based on image analyzing. There are several factors that affect the results of the fitness test of the denture base, such as the shape of the denture, the condition of the mucosa within denture bearing area, bite force and the state of occlusal contact. Then, using the new system, these factors were examined for clinical application of the mean film thickness of white silicone. The experiments are composed of three stages. In the first stage, the white silicone was pressurized between two of tablets involved in three types, with a pressurizer. These data resulted in a regression equation applying the rheological equation. In the second stage, pressurizing tests were performed on the models of jaw mucosa with uniform compressibility. The models were categorized into three types according to their compressibility. A result was the more compressible the models of jaw mucosa are, the thicker the white silicone film is. In the third stage, the compressibilities were mixed in the models of jaw mucosa. In the pressurizing test, the compressing dies were modeled on the denture base. Five loading points were established on the surface. Correlation between data obtained from the results of the pressurizing test at each loading point was investigated. The results from these experiments were as follows. 1. The regression equation was established from the compressing test of white silicone between tablets of rigid type. H = 0.236 (r1r2/square root of P) -0.0008 R = 0.977 H: mean film thickness of white silicone R: coefficient of correlation P: loading volume r1: 1/2 of the major side of the each tablet r2: 1/2 of the minor side of the each tablet Units are expressed in the C. G. S system. The film thickness was more highly correlated with the distance to the open system of each tablet than the area.

Denture Bases↗

PubMed1994

Silicone breast implant litigation (Part 1).

Silicone breast implant litigation has escalated in the past couple of years with the Food and Drug Administration (FDA) investigation of silicone gel implants which resulted in finally removing the silicone gel implants from the market. Plaintiffs have linked various medical problems to the presence of silicone in the body. The FDA has stated that there is no medical evidence that silicone causes autoimmune disease. Silicone has never been shown to cause breast cancer. Breast implants can result in complications such as capsule contracture, gel bleed, implant rupture, calcifications around the implants, and possibly interference with mammography in the diagnosis of breast cancer. Plaintiffs have claimed that the implant manufacturers knew of the defects in the silicone shell implant covering, and covered up the facts. The product liability action has become a class action, and a proposed settlement has been made in terms of which implant recipients with any problems will be reimbursed. Furthermore, there will be coverage for future implant problems over the next 30 years. There will still be some litigation by those patients who have opted out of the settlement agreement.

Breast Implants↗

PubMed1994

Talc deposition in skin and tissues surrounding silicone gel-containing prosthetic devices.

BACKGROUND AND DESIGN: Periprosthetic capsule formation is the most common cause of morbidity associated with silicone gel-filled breast implants. All implant recipients develop capsules. However, the extent of capsule formation varies greatly among patients, ranging from a thin flexible membrane to a constrictive inelastic band of sclerotic collagen. Although silicone gel bleed has been proposed as the most likely cause of excessive capsular sclerosis, liquid silicone did not induce fibrosis in early clinical trials. Because many implant modifications have been introduced since the original studies were performed, a more plausible explanation for excess capsular sclerosis is the inadvertent introduction of a fibrogenic contaminant. The skin and periprosthetic tissues removed from 41 women during implant revision surgery were examined for the presence of foreign substances that might contribute to capsular sclerosis. Tissue was examined histologically with and without polarizing filters and with scanning electron microscopy equipped for energy-dispersive x-ray analysis. RESULTS: A high incidence of talc was found within the skin and tissues adjacent to silicone-containing breast prostheses. Birefringent talc crystals, identified in 71% of the patients, were observed within nodular granulomas and perivascular histiocytes. Two specimens containing talc crystals were analyzed by energy-dispersive roentgenographic analysis, which confirmed the identity of the crystalline material as talc. Among 10 capsules examined by direct immunofluorescence, there was no evidence of immune complex deposition. CONCLUSIONS: The high incidence of talc deposition in the skin and tissues surrounding silicone implants suggests that talc either is introduced at the time of implant surgery (possibly in association with the silicone elastomer bag, tissue sizers, or surgical gloves) or is released into the tissues as a silicone gel contaminant during gel bleed. Talc, a known sclerosing agent, may contribute to periprosthetic fibrosclerosis.

Adult↗

PubMed1996

Kikuchi's histiocytic necrotizing lymphadenitis associated with ruptured silicone breast implant.

OBJECTIVE: In this report we explore the relationship between Kikuchi's necrotizing lymphadenitis (Kikuchi-Fujimoto disease, KD) and a leaky silicone breast implant. PATIENT: The simultaneous occurrence of KD and silicone lymphadenopathy in an axillary lymph node of a patient with a leaking silicone breast implant is reported. Since both KD and silicone implants have been implicated in autoimmune diseases, including systemic lupus erythematosus, serologic tests for antinuclear antibodies and rheumatoid factor were performed. RESULTS: Axillary lymph nodes showed both silicone lymphadenopathy, as well as classic morphologic and immunophenotypic features of KD. Screening tests for systemic autoimmune disorders were within normal range, suggesting that the unusual Kikuchi's-like immune reaction in one axillary lymph node was localized. The patient has no evidence of progressive immunologic disorders 3 years later. Subsequent lymph node biopsies showed silicone adenopathy with no evidence of KD. CONCLUSIONS: Our findings indicate that silicone compounds may be associated with transient abnormal immune reactions and lend further support to the hypothesis that KD represents an exuberant T-cell-mediated immune response to a variety of nonspecific stimuli.

Adult↗

PubMed1996

[Treatment of vitreoretinal proliferation in rhegmatogenous detachment and silicone oil tamponade].

PURPOSE: To describe our technique of vitrectomy and silicone oil tamponade for managing retinal detachment and to report the last results according to the posterior and anterior proliferative vitreoretinopathy. METHODS: A retrospective study was conducted in 108 patients who underwent vitreoretinal surgery and silicone oil tamponade for proliferative vitreo-retinopathy, 64% patients had already been operated without success and 42% underwent vitrectomy with SF6 or C3F8. Diffuse posterior proliferative vitreo-retinopathy (grade C3-D) was present in 64% patients and anterior proliferative vitreoretinopathy was present in 43.5%. Silicone oil was removed in 79% patients after a mean duration of 6.3 months. It was replaced by 16% C3F8. All patients were followed for a minimum of 6 months. RESULTS: Before silicone oil removal, 55% of the retinas were reattached posterior to the scleral buckle with one operation, 78% after 2 operations and 88% after 3 or 4 operations. An average of 2.1 vitrectomy surgeries were performed. Reproliferation was correlated with the anterior proliferative vitreo-retinopathy (p < 0.001), posterior proliferative vitreo-retinopathy (p < 0.01) or previous vitrectomy (p < 0.05). The final visual acuity was 1/20 or better in 61% of the eyes and 2/10 or better in 30.5%. After silicone oil removal, 8% retinas redetached, 21% of the eyes had hypertony, 7.5% had hypotony and 7% of the corneas had dystrophy. CONCLUSION: Silicone oil tamponade was effective for the treatment of retinal detachments with proliferative vitreo-retinopathy. Since the main complications were hypertony and corneal dystrophy, silicone oil should be reserved for severe proliferative vitreo-retinopathy cases.

Adult↗

PubMed1997

Assessment and longevity of the silicone gel breast implant.

Many patients are now consulting plastic surgeons for evaluation of their silicone gel breast implants. This study assesses the accuracy of a clinician's ability to determine if a silicone gel breast implant has failed. In addition, it sheds light on the long-term integrity of the silicone gel breast implant. This study examined the condition of 350 silicone gel breast implants in a group of 159 of the authors' patients who previously had undergone augmentation mammaplasty or breast reconstruction. These women underwent secondary open procedures including capsulotomy or capsulectomy for fibrous capsule contractures, exchange of implants, or other revisional surgery. The condition of the implant was noted at the time of this secondary operation. The preoperative evaluation, which included the patient's history and physical examination and often mammography, was then matched against the operative findings to determine the pertinent factors that predict the integrity of a silicone gel breast implant. A history of trauma and/or a reported change in shape of a patient's breast correlated with implant failure. An analysis of implant failure as a function of implant age revealed that 63 percent of silicone gel breast implants in place 12 years or greater in this study population were not intact. A change in the patient's physical examination, including a softened breast consistency and/or the presence of a nodule or mass adjacent to an implant, also was suggestive of implant failure. Several different mammographic presentations of implants that were not intact were identified. This modality predicted implant failure in 89 percent of implants studied. It is hoped that this information will help clinicians to make a more accurate assessment of the condition of a patient's silicone gel breast implant. It should be noted that all women in our study underwent secondary procedures, as stated above. The results obtained apply to this patient group but may not specifically pertain to the general implant-bearing population.

Breast Implants↗

PubMed1999

A comparison of autoantibody production in asymptomatic and symptomatic women with silicone breast implants.

OBJECTIVE: We previously reported an increased preponderance of a broad range of autoantibodies in symptomatic women with silicone breast implants. The objective of this study was to investigate the frequency of autoantibody production in asymptomatic compared to symptomatic women with silicone implants. One hundred twenty-two asymptomatic women were recruited to our center for autoantibody detection through an advocate dealing with breast implant liabilities. METHODS: Autoantibody detection in 86 asymptomatic women was done blindly on a panel of 15 different antibodies (dsDNA, ssDNA, histones, SSA/Ro, SSB/La, RNP, cardiolipin, phosphatidylserine, pyruvate dehydrogenase, Scl-70, NC-1, silicone, collagen I, II, and IV). Clinical variables, specific questioning about related silicone implant symptoms, and a rheumatological examination were performed blindly by a certified rheumatologist. The findings were recorded and at a later stage compared with positive autoantibody detection. The normal control group consisted of age and sex matched Israeli women without known autoimmune disease. In the positive control group were symptomatic women previously tested for antibody production. The autoantibodies were assessed by ELISA. Values from individual patients were considered positive only when greater than 3 standard deviations above the control mean. RESULTS: The mean ages of 86 asymptomatic and 116 symptomatic women were 46.2+/-11.2 and 45.7+/-8.3 years, respectively. Breast implants were in place for a mean period of 8.2+/-5.0 years in the asymptomatic group and 15.0+/-5.6 years in the symptomatic group. The incidence of increased titers of autoantibodies ranged from 2 to 13% for 13 different autoantibodies among asymptomatic women. Among symptomatic women, 20% harbored 4 autoantibodies and 8% had 6 autoantibodies. The most common antibodies in the asymptomatic group were: dsDNA 8%; ssDNA 9%; SSB/La 13%; silicone 9%; collagen II 9%. No autoantibodies were found for NC-1, Scl-70, or RNP. Among the symptomatic group, the most common autoantibodies were histone ribosomal phosphate, SSA, SSB, Scl-70, cardiolipin, phosphatidylserine, GM2-ganglioside, and NC-1. Comparison of autoantibody incidence in asymptomatic and symptomatic women with silicone breast implants revealed an increased incidence of anti-SSB/La and anticollagen II in both groups. Polyclonality was more prominent in the group of symptomatic women with silicone breast implants, but also evident in 3 asymptomatic women. CONCLUSION: The mean duration of implant in the asymptomatic group was significantly less compared with the symptomatic group (p<0.01). The development of autoantibodies may be related to implant duration.

Adult↗

PubMed2005

Chirality transfer from silicon to carbon.

The exploitation of the asymmetry at silicon in stereoselective synthesis is an exceptionally challenging task. Initially, silicon-stereogenic silanes have been utilized to elucidate the stereochemical course of substitution reactions at silicon. Apart from these mechanistic investigations, only a handful of synthetic applications with an asymmetrically substituted silicon as the stereochemical controller have been reported to date. In these transformations the chiral silicon functions as a chiral auxiliary. Conversely, a direct transfer of chirality from silicon to carbon during bond formation and cleavage at silicon has remained open until its recent realization in both inter- and intramolecular reactions. In this Concept, the pivotal considerations in relation to the nature of suitable silanes as well as mechanistic prerequisites for an efficient chirality transfer will be discussed.

Journal Article↗

PubMed2002

Growth promotion and an increase in cell wall extensibility by silicon in rice and some other Poaceae seedlings.

The effect of silicon on organ growth and its mechanisms of action were studied in rice ( Oryza sativa L. cv. Koshihikari), oat ( Avena sativa L. cv. Victory), and wheat ( Triticum aestivum L. cv. Daichino-Minori) seedlings grown in the dark. Applying silicon in the form of silicic acid to these seedlings via culture solution resulted in growth promotion of third (rice) or second (oat and wheat) leaves. The optimal concentration of silicon was 5-10 mM. No growth promotion was observed in early organs, such as coleoptiles or first leaves. In silicon-treated rice third leaves, the epidermal cell length increased, especially in the basal regions, without any effect on the number of cells, showing that silicon promoted cell elongation but not cell division. Silicon also increased the cell wall extensibility significantly in the basal regions of rice third leaves. These results indicate that silicon stimulates growth of rice and some other Poaceae leaves by increasing cell wall extensibility.

Journal Article↗