The study on the feasibility of dietary supplementation with dimethyl silicone oil to prevent frothy rumen bloat in goats fed with high concentrate diets.

The current study was conducted to investigate the feasibility of high concentration diet (HCD) supplementation with Dimethyl Silicone Oil (DSO) to prevent frothy rumen bloat in goats. The treatments were control group (group C, feeding HCD) and test group (group T, feeding HCD supplemented with 0.1%DSO). The results showed that compared with the group C, the ruminal pH value, Microbial Crude Protein content of group T was extremely significantly higher (p < 0.01), the levels of acetic acid and propionic acid were significantly (p < 0.05) and extremely significantly (p < 0.01) lower in group T, respectively. The foam production and foam strength of the rumen fluid in the group T was extremely significantly lower (p < 0.01), the viscosity was extremely significantly (p < 0.01) higher than those of group C. The total gastrointestinal apparent digestibility of various nutrients, the rumen microbial relative abundance at the phylum level and genus level were not significantly different (p > 0.05). The results indicated that the supplementation of 0.1% DSO in HCD can significantly eliminate foam of the rumen fluid, and didn't disturb the ruminal microorganisms, no negatively affect on digestibility of nutrients in goats, thereby has the application prospect of preventing frothy rumen bloat.

The gas produced by rumen fermentation is wrapped in foam and cannot be discharged is the root cause of frothy bloat induced by a high concentration diet. In the present study, the feasibility of dietary supplementation with Dimethyl Silicone Oil (DSO) to prevent frothy bloat was preliminarily evaluated. The results indicated that DSO can significantly eliminate foam of the rumen fluid, and has not negatively effect on the ruminal microorganisms and the digestibility of nutrients in goats, thereby has the application prospect of preventing frothy bloat.

Distribution of Triamcinolone Acetonide after Intravitreal Injection into Silicone Oil-Filled Eye.

There is increasing use of the vitreous cavity as a reservoir for drug delivery. We study the intraocular migration and distribution of triamcinolone acetonide (TA) after injection into silicone oil tamponade agent during and after vitrectomy surgery ex vivo (pig eye) and in vitro (glass bottle). For ex vivo assessment, intraocular migration of TA was imaged using real-time FLASH MRI scans and high-resolution T2W imaging and the in vitro model was monitored continuously with a video camera. Results of the ex vivo experiment showed that the TA droplet sank to the interface of silicone oil and aqueous almost immediately after injection and remained inside the silicone oil bubble for as long as 16 minutes. The in vitro results showed that, after the shrinkage of the droplet, TA gradually precipitated leaving only a lump of whitish crystalline residue inside the droplet for about 100 minutes. TA then quickly broke the interface and dispersed into the underlying aqueous within 15 seconds, which may result in a momentary increase of local TA concentration in the aqueous portion and potentially toxic to the retina. Our study suggests that silicone oil may not be a good candidate as a drug reservoir for drugs like TA.

Intraventricular Silicone Oil: A Case Report.

Intracranial silicone oil is a rare complication of intraocular endotamponade with silicone oil. We describe a case of intraventricular silicone oil fortuitously observed 38 months after an intraocular tamponade for a complicated retinal detachment in an 82 year-old woman admitted in the Department of Neurology for a stroke. We confirm the migration of silicone oil along the optic nerve. We discuss this rare entity with a review of the few other cases reported in the medical literature. Intraventricular migration of silicone oil after intraocular endotamponade is usually asymptomatic but have to be known of the neurologists and the radiologists because of its differential diagnosis that are intraventricular hemorrhage and tumor.

Adhesion of heavy silicone oil to the anterior surfaces of the posterior lens capsule.

PURPOSE: To report a case of heavy silicone oil adhesion to the anterior surfaces of posterior lens capsule.
 METHODS: Descriptive case report.
 RESULTS: A healthy 56-year-old pseudophakic man presented with visual disturbance in his right eye for a week. There was a large irregular retinal tear at 5-7 o'clock, mild vitreous hemorrhage, and total retinal detachment. He underwent 23-G pars plana vitrectomy and heavy silicone oil tamponade was injected. The retina remained attached postoperatively and heavy silicone oil was removed 2 months later. Anatomic and functional success was achieved and his vision had improved. Five months later, he presented with blurred and decreased vision secondary to tiny droplets of heavy silicone oil at the anterior surfaces of the posterior capsule. After applying Nd:YAG laser capsulotomy, visual acuity improved and stayed stable during 1 year follow-up. 
 CONCLUSIONS: Heavy silicone oil adhesion to the anterior surfaces of the posterior lens capsule has not been reported before. This complication may be seen rarely and treated by Nd:YAG laser capsulotomy successfully.

Ionic strength affects tertiary structure and aggregation propensity of a monoclonal antibody adsorbed to silicone oil-water interfaces.

Therapeutic proteins formulated in prefilled syringes lubricated with silicone oil come in contact with silicone oil-water interfaces for their entire shelf lives. Thus, the interactions between protein and silicone oil were studied to determine the effect of silicone oil on a monoclonal antibody's stability, both at the interface and in the bulk solution. The influence of ionic strength on these interactions was also investigated through the addition of various monovalent and divalent salts to sample formulations. The tertiary structure of the antibody was perturbed when it adsorbed to the silicone oil-water interface in solutions at low ionic strength. However, the tertiary structure of the antibody at the interface was not perturbed when the ionic strength of the formulation was increased. Even at low ionic strength, the secondary structure of the antibody adsorbed to the silicone oil-water interface was retained, suggesting that at low ionic strength, the adsorbed antibody assumes a molten globule-like conformation. This partially unfolded species was aggregation-prone, especially during agitation. Silicone oil-induced aggregation of the antibody was inhibited at higher ionic strength.

Migration of silicone oil in the cerebral intraventricular system.

OBJECTIVE AND IMPORTANCE: Silicone oil is commonly used to tamponade the retina in the case of retinal detachment. We present a case in which silicone oils had migrated to the ventricles and the head computed tomographic (CT) scan was misread as intraventricular hemorrhage. CLINICAL PRESENTATION: We report a 72-year-old patient who was referred to us with the diagnosis of subarachnoid hemorrhage associated with intraventricular hemorrhage based on a head CT done in the emergency room for increased headaches. INTERVENTION: The density of the silicone oil on CT mimicked the density of blood and led to the initial misinterpretation of the head CT. A brain magnetic resonance imaging was done and confirmed the diagnosis of silicone oil that migrated from the eye to the subarachnoid space and intraventricular space. CONCLUSION: The possibility of the silicone oil causing chemical meningitis and possible hydrocephalus was raised, but the patient's headaches improved and it was decided not to pursue any further diagnostic work up.

Clinical device-related article evaluation of morphology and functions of a foldable capsular vitreous body in the rabbit eye.

We previously proposed a new strategy to replace a vitreous body with a novel foldable capsular vitreous body (FCVB). In this study, the FCVB was designed to mimic natural vitreous morphology, and evaluate its physiological functions compared with traditional silicone oil substitutes, in an established rabbit model of proliferative vitreoretinopathy. We found that FCVB was a very good replacement for closely mimicking the morphology and restoring the physiological functions, such as the support, refraction, and cellular barriers, of the rabbit vitreous body. The study has provided us with a novel research and therapy strategy that could effectively mimic the morphology and physiological function of the rabbit vitreous body.

The distribution, release kinetics, and biocompatibility of triamcinolone injected and dispersed in silicone oil.

PURPOSE: Triamcinolone acetonide (TA) has been proposed as an adjuvant to pars plana vitrectomy with silicone oil for the surgical treatment of proliferative vitreoretinopathy and proliferative diabetic retinopathy. However, to date no data about the distribution and pharmacokinetics of lipophilic TA injected into silicone oil have been reported. METHODS: An artificial vitreous space chamber was filled with silicone oil. TA was either injected or dispersed into silicone oil. TA release using a continuous flow model was measured spectrophotometrically. To determine the antiproliferative or cytotoxic effect of the released TA, monolayer cultures of retinal pigment epithelial cells (ARPE19) and retinal ganglion cells (RGC5) were used. Bromodeoxyuridine incorporation, MTT assay, and scanning electron microscopy were performed. RESULTS: Injected TA sank slowly through the silicone oil and started to sediment below the silicone oil bubble shortly after injection. After the simulated intravitreal injection, no TA could be retrieved from the silicone oil bubble. In contrast, when a suspension of silicone oil and TA was prepared before injection, stable noncytotoxic amounts of TA (25 microg/mL) could be retrieved for up to 90 days. After mere injection (without previous suspension in silicone oil), the sedimented TA crystals showed a pronounced cytotoxic effect. CONCLUSIONS: Intravitreally injected TA does not mix with silicone oil. TA crystals that sediment at the lower border of a silicone oil bubble may be harmful to retinal cells. A suspension of TA in silicone oil may exhibit safer extended release over several days.

An epidemic of sticky silicone oil at the Rotterdam Eye Hospital. Patient review and chemical analyses.

PURPOSE: To report and study the phenomenon of abnormal silicone oil adherent to the retina at the time of removal in a number of patients. MATERIALS AND METHODS: Chart review was performed to identify possible patient or procedural factors that could predispose to sticky silicone oil formation. Gas chromatography-mass spectroscopy and nuclear magnetic resonance spectroscopy analyses were performed on sticky silicone oil samples, on perfluorocarbon liquid and on silicone oil samples straight from the vial. RESULTS: Sticky silicone oil remnants were seen on the retina in 28 out of 234 silicone oil removal procedures between January 2001 and November 2002. Forceful removal was complicated in two patients by a choroidal hemorrhage and in one patient by a retinal tear. The use of perfluoro-octane (PFO; C(8)F(18)) rather than perfluorodecalin (C(10)F(18)) was related to the phenomenon (P < 0.001). Gas chromatography-mass spectroscopy analysis revealed a significant presence of PFO in samples of sticky silicone oil, and traces of partially fluorinated carbon liquid were found in the sticky oil as well as in the PFO samples. CONCLUSIONS: The use of PFO may have been a predisposing factor for the occurrence of sticky silicone oil. While the presence of silicone oil remnants on the retina did not cause lasting side effect, forceful attempts at removal can lead to complications.

Hazard assessment of silicone oils (polydimethylsiloxanes, PDMS) used in antifouling-/foul-release-products in the marine environment.

Non-eroding silicone-based coatings can effectively reduce fouling of ship hulls and are an alternative to biocidal and heavy metal-based antifoulings. The products, whose formulations and make up are closely guarded proprietary knowledge, consist of a silicone resin matrix and may contain unbound silicone oils (1-10%). If these oils leach out, they can have impacts on marine environments: PDMS are persistent, adsorb to suspended particulate matter and may settle into sediment. If oil films build up on sediments, infiltration may inhibit pore water exchange. PDMS do not bioaccumulate in marine organisms and soluble fractions have low toxicity to aquatic and benthic organisms. At higher exposures, undissolved silicone oil films or droplets can cause physical-mechanic effects with trapping and suffocation of organisms. These 'new' effects are not covered by current assessment schemes. PDMS make the case that very low water solubility and bioavailability do not necessarily preclude damage to marine environments.

Interaction with intraocular lens materials: does heavy silicone oil act like silicone oil?

PURPOSE: To determine the interaction of heavy silicone oil with various intraocular lens (IOL) materials and whether heavy silicone oil covers the silicone IOL optic as silicone oil does. SETTING: Department of Ophthalmology, Dokuz Eylul University, Izmir, Turkey. METHODS: The study group comprised 5 poly(methyl methacrylate) (PMMA) IOLs, 4 foldable silicone IOLs, 5 foldable hydrophilic acrylic IOLs, and 5 foldable hydrophobic acrylic IOLs. Each IOL was bathed in balanced salt solution (BSS) for 10 minutes and then placed in heavy silicone oil dyed with Sudan Black for another 10 minutes. Afterward, each IOL was reimmersed in BSS for 5 minutes and examined under the light microscope. Digital images were analyzed to determine the optic area covered with heavy silicone oil. RESULTS: The mean heavy silicone oil coverage was 7.05% +/- 7.88% (SD) (range 1.13% to 20.54%) on PMMA IOLs, 100% on silicone IOLs, 12.17% +/- 11.43% (range 1.25% to 31.52%) on hydrophobic acrylic IOLs, and 34.64% +/- 13.28% (range 12.57% to 44.42%) on hydrophilic acrylic IOLs. Heavy silicone oil coverage of silicone IOLs was statistically significantly greater than the coverage of other IOL materials. CONCLUSION: Heavy silicone oil acted the same as silicone oil and covered the entire surface of silicone IOLs.

The phenomenon of "sticky" silicone oil.

BACKGROUND: To investigate the reasons for difficulties removing silicone oil from the vitreous cavity due to putative adherence to the retina. METHODS: Gas chromatography-coupled mass spectroscopy of the headspace (GC/MS/HS) and gel permeation chromatography (GPC) were used to detect volatile compounds in silicone oil samples explanted from patients, qualitatively as well as quantitatively. Surface and interfacial tensions of the explanted samples were measured using the pendent-drop technique. To simulate the removal of silicone oil from the vitreous cavity, the contact between silicone oil and differently treated surfaces and various aspiration techniques were tested in vitro. RESULTS: The median concentration of perfluorodecalin in seven "sticky" samples was 2.4 times higher than in 14 non-sticky samples. In the sticky samples, the median surface tension of the aqueous phase was lower. The difficulty of aspirating silicone oil could be reproduced in vitro by reducing the surface tension of the aqueous environment of the silicone oil. CONCLUSION: The observed stickiness of silicone oil seems to be a matter of reduced surface tension of the surrounding aqueous material and/or contamination of silicone oil with perfluorocarbon liquid, which creates interruption of the material flow, giving the impression of adherence of the silicone oil to the retina.

Pathogenic implications of subretinal gas migration through pits and atypical colobomas of the optic nerve.

OBJECTIVE: To describe subretinal migration of gas and silicone oil in a series of patients with congenital cavitary optic disc anomalies and to further clarify the pathogenesis of the associated maculopathy. METHODS: Medical records of 4 female patients, aged 8 to 34 years, who developed subretinal gas migration after vitreous surgery for macular detachment associated with cavitary optic disc anomalies were reviewed. A theoretical model was used to calculate the pressure differential required to induce subretinal gas migration through an optic pit. RESULTS: The 4 patients had bilateral atypical optic nerve colobomas or a unilateral large optic pit. A definite defect in the tissue overlying the disc excavation could be seen in one eye, and intraoperative drainage of subretinal fluid through the disc anomaly was possible in all cases. Subretinal migration of gas or silicone oil was seen intraoperatively in one case and first appeared between 1 and 17 days postoperatively in the remaining cases. Theoretical calculations suggest that the pressure differential required for migration of gas through a small defect in the roof of a cavitary disc lesion is within the range of expected fluctuations in cerebrospinal fluid pressure. CONCLUSIONS: These observations provide clinical confirmation of a defect in tissue overlying cavitary optic disc anomalies and imply interconnections between the vitreous cavity, subarachnoid space, and subretinal space. We theorize that intermittent pressure gradients resulting from normal variations in intracranial pressure play a critical role in the pathogenesis of retinopathy associated with cavitary disc anomalies.

Interaction of intraocular lenses with various concentrations of silicone oil: an experimental study.

The aim of this study was to evaluate the interaction between various widely used intraocular lenses (IOLs) and silicone oils of different viscosities. Four groups of IOLs, including monoblock foldable hydrophilic acrylic IOLs (Morcher, type 92s); monoblock hydrophobic acrylic IOLs (Acrysof-SA60AT, Alcon); single-piece rigid polymethylmethacrylate (PMMA) IOLs (Intraocular Optical International-IOI-65130) and a three-piece foldable silicone optic IOL (CeeOn Edge 911A, Pharmacia UpJohn) were analyzed in vitro to determine the percentage adherence 1,000-centistoke, 1,300-centistoke or 5,000-centistokes silicone oil on the IOL optic. For each IOL type, there was no statistically significant difference in the mean silicone oil coverage (MSC) of the IOL optics for the different viscosities of silicone oil. Silicone IOLs had the highest MSC percentage (79.9%) whereas hydrophilic acrylic IOLs were the least silicone-covered IOLs (7.8%) compared to the other IOL types tested in this study. It is not the concentration of silicone oil that affects silicone oil coverage. When performing small-incision cataract surgery in patients who may require silicone oil injection, foldable hydrophilic acrylic or hydrophobic acrylic lenses should be preferred over standard foldable silicone lenses.

Effect of heparin surface modification in reducing silicone oil adherence to various intraocular lenses.

PURPOSE: To evaluate surface properties of various intraocular lenses (IOLs), including a newly fabricated heparin-surface-modified (HSM) silicone IOL, with special reference to their efficiency in reducing potential silicone oil adherence to the IOL optics. SETTING: Center for Research on Ocular Therapeutics and Biodevices, Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: Five groups of rigid and foldable IOLs were analyzed in an in vitro test for the percentage of silicone oil adherence: a single-piece foldable hydrophilic-acrylic IOL (n = 9); a single-piece rigid poly(methyl methacrylate) (PMMA) IOL with HSM coating of the lens optic (n = 9); a 3-piece foldable silicone optic IOL with HSM coating of the optic (n = 10); a single-piece standard rigid PMMA IOL (n = 7); and a standard 3-piece foldable silicone optic IOL (n = 9). After the IOLs were immersed in water and then in silicone oil, gross photographs taken. Image analysis was performed to evaluate the percentage of silicone oil coverage of the anterior and posterior surfaces of each IOL optic. RESULTS: The mean silicone oil coverage of the hydrophilic-acrylic IOLs was 5.6% +/- 2.5% (SD); of the HSM PMMA IOLs, 6.2% +/- 4.3%; of the HSM silicone optic IOLs, 6.7% +/- 3.2%; and of the standard PMMA IOLs, 20.3% +/- 13.3%. The mean silicone oil coverage was greatest on the standard silicone optic IOLs, 98.2% +/- 3.1%. CONCLUSIONS: Intraocular lenses with a hydrophilic optic have less tendency toward adherence to silicone oil than more hydrophobic designs. A foldable silicone IOL with heparin surface modification can significantly reduce potential silicone oil adherence, comparable to the level achievable with the rigid HSM PMMA designs. Two new foldable IOL styles, the HSM silicone IOL and IOLs in the general class of hydrophilic-acrylic, were highly efficacious in reducing silicone oil adherence. There is now a real choice of foldable lenses for patients with actual or potential vitreoretinal diseases.

Use of O44 as a solvent for silicone oil adhesions on intraocular lenses.

PURPOSE: To describe a solvent that removes silicone oil adhesions on intraocular lenses (IOLs). METHOD: The solvent O44 is a partially fluorinated alcane that dissolves silicone oil. Silicone oil adhesions on silicone and poly(methyl methacrylate) IOLs were treated with O44. The extent of silicone oil adhesions and the effectiveness of O44 were studied by gross microscopy. RESULTS: The solvent O44 removed silicone oil adhesions from both IOL types. CONCLUSION: The substance O44 may be a successful intraoperative tool to remove silicone oil IOL adhesions, avoiding IOL explantation.