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PubMed1982

Toxicity evaluation of a novel filler free silicone rubber biomaterial by cell culture techniques.

Cytotoxicity of a novel filler free silicone rubber (FFSR) was evaluated by studying its effect on mouse L929 cells. Silastic and a laboratory rubber tubing (RT) were used as control materials. Three different experimental methods were used. In method A, after six days of cell culturing in the sample extracts, there were 95, 80, and 50% of control viable cells for FFSR, Silastic, and RT, respectively. Similarly, in method B, after six days of direct contact between samples and the cells, there were 80, 40, and 20% of control viable cells for FFSR, Silastic, and RT, respectively. For the Agar Overlay Test, method C, the cells under the FFSR samples were normal and healthy compared to those under Silastic and RT. From these studies it was concluded that FFSR had the least cytotoxicity of the three materials studied.

Animals↗

PubMed1984

Covalent coupling of polysaccharides to silicon and silicon rubber surfaces.

A method to produce a hydrogel by covalently coupling dextran polysaccharide to silicon and silicon rubber surfaces is described. A bifunctional epoxysilane was used as coupling mediator and the conditions for the reaction were optimized. Coupling of the silane to silicon rubber was possible only after oxidation of the surface by plasma etching. The reaction between the epoxy-group and dextran was concentration dependent and required high concentrations of dextran. The turnover rate of fibrinogen in solution at the hydrophilic surface was found to be high when measured by ellipsometry.

Adsorption↗

PubMed1995

Study of aging of silicone rubber biomaterials with NMR.

Multinuclear nuclear magnetic resonance (NMR) spectroscopy (29Si, 13C, 1H) is used to characterize the aging process of silicone rubber-based biomaterials in a rat model. 1H NMR relaxation measurements (spin-lattice, T1, and spin-spin, T2, relaxation times) were performed to better understand the molecular dynamics of polysiloxane chains in implants. After 1 year of implantation in animals, changes in the 1H T2 relaxation times and the NMR spectra were observed in polydimethylsiloxane, Silastic sheets and chin implants, while these measurements remain unchanged in finger joints. Very small amounts of fat were detected in all types of silicone rubber implants at the end of the implantation period. This work shows that free silicone migrates from the implants to adjacent tissues and distant sites, such as spleen or liver, and is chemically modified.

Animals↗

PubMed1981

Transport of prostaglandins through silicone rubber.

The in vitro release profiles of the F-series of prostaglandins were determined from a silicone rubber matrix of constant surface area. Silicone rubber was selective toward prostaglandin transport and offers potential as a controlled-release delivery system. Drug release patterns were dependent on the lipophilicity of the prostaglandin molecule. For dinoprost (prostaglandin F2 alpha), the following sequences was observed: methyl ester greater than free acid greater than tromethamine salt. The biologically potent carboprost methyl [(15S)-15-methylprostaglandin F2 alpha methyl ester] was release considerably faster than the methyl ester of the parent dinoprost molecule, while release of the tromethamine salt of the two prostaglandins was similar. Permeability rates of the salts were depressed substantially when compared to their respective C-1 methyl esters. Results from independent membrane transport studies supported the observed dependence of steady-state flux on the chemical structure of the prostaglandin molecule. Plots of the amount released per unit area versus the square root of time were linear except for the initial drug release phase, and the total amount of prostaglandin released increased as the initial loading dose was raised. The data were analyzed according to a physical model describing drug release from inert matrix systems. The observed concentration dependence was consistent with the predictions of the model.

Diffusion↗

PubMed1983

Effect of different water-soluble additives on water sorption into silicone rubber.

The ability of ethylene glycol; glycerin; polyethylene glycols 200, 400, and 6000; polysorbate 80; and lactose dispersed in silicone rubber, to promote water sorption into the polymer was investigated in water and in isotonic (pH 7.4) phosphate buffer. Polyethylene glycols 200 and 400, lactose, and, especially, glycerin were effective water carriers. Marked differences in the kinetics of rubber swelling were observed, depending on the carrier. The swelling patterns relative to ethylene glycol, glycerin, and polyethylene glycol 200 showed a maximum due to significant leaching of these additives from the polymer. Steady swelling degrees were afforded by polyethylene glycols 400 and 6000 and by polysorbate 80. The interdependent processes of polymer imbibition and carrier release were speeded up without altering their kinetic patterns by increasing the initial surface-volume ratio of the devices. A proportionality resulted between maximal swelling and initial carrier concentration, although the swelling patterns were substantially unaffected by this variable.

Adsorption↗

PubMed1983

Contamination of injectable solutions with 2-mercaptobenzothiazole leached from rubber closures.

An impurity, discovered in a sample of digoxin injectable solution commercially packaged in a syringe for single-dose delivery, was found to originate from the rubber closure of the syringe and was identified as 2-mercaptobenzothiazole, a common accelerator for rubber vulcanization. Several similarly packaged injectable solutions of a variety of drugs from various manufacturers were examined and over half contained 2-mercaptobenzothiazole. The compound was identified by UV spectrophotometry (including a pH-dependent shift in its absorbance maximum), by mass spectrometry, and by comparison with standard 2-mercaptobenzothiazole using silica gel and reverse-phase high-performance liquid chromatography (HPLC). The presence of this impurity in injectable solutions may have implications with regard to toxicity and may interfere with the assay of digoxin injectable solution by HPLC.

Benzothiazoles↗

PubMed1990

A prospective study of infrared coagulation, injection and rubber band ligation in the treatment of haemorrhoids.

One hundred patients with non-prolapsing and one hundred with prolapsing haemorrhoids were allocated to receive conventional treatment (CT) by injection sclerotherapy or rubber band ligation, or infrared photocoagulation (IRC). Significantly more patients with nonprolapsing haemorrhoids were symptom free after IRC (81%) than CT (59%) at three months. (Chi2 = 4.4, p = 0.05). There was no significant difference in the outcome at 1 or 4 years. Likewise for prolapsing haemorrhoids, there was no significant difference in the outcome of IRC or CT at 3 months, one or 4 years. However, recurrence of prolapse was more common after IRC (54%) than rubber band ligation (RBL) (27%) at 1 year (Chi2 = 3.46, p less than 0.1). IRC was significantly less painful than CT (p less than 0.001). IRC is a safe, rapid, non-invasive alternative to CT, which is acceptable to the patient and give similar results, though RBL provides more rapid and longer lasting relief from prolapse.

Adult↗

PubMed1978

The embolization of vascular malformations of the spinal cord with low-viscosity silicone rubber.

Development of the low-viscosity silicone rubber has made possible the successful embolization and complete obliteration of 9 out of 11 vascular malformations of the spinal cord treated with this material. The procedure is particularly useful in patients where the malformation is fed by a limited number of posterior radicular feeders without any supply from the anterior spinal artery. One patient with a supply from the anterior spinal artery. One patient with a supply from both anterior and posterior feeders was successfully embolized after a temporary occlusion of the anterior spinal radicular feeder. Seven patients out of 11 embolized with silicone rubber showed a clinical improvement of their signs and symptoms.

Adult↗

PubMed1989

Rubber band ligation for piles can be disastrous in HIV-positive patients.

We report a patient with haemorrhoids treated with rubber band ligation who developed a huge supralevator abscess. A diverting sigmoidostomy had to be established as surgical drainage via the rectum was not adequate. Eventually the patient accepted the HIV-testing which proved positive. Six months later the sigmoidostomy was still needed as the abscess cavity remained large. We conclude that rubber band ligation in HIV-positive patients should be abandoned.

Abscess↗

PubMed1993

Complications of rubber band ligation of symptomatic internal hemorrhoids.

In a prospective study, 512 patients undergoing hemorrhoidal band ligation over a seven-year period were followed up to focus on complications. Thirteen patients (2.5 percent) were hospitalized: six with delayed massive rectal bleeding, three with urinary retention, pain, and fever (one developed perianal abscess), and three others with severe pain due to prolapsed thrombotic hemorrhoids (one developed difficulty in urination). One patient developed perianal abscess and perianal fistula two months after ligation. Twenty-four patients (4.6 percent) suffered from minor complications: 11 patients had painful thrombosed hemorrhoids; five experienced slippage of bands; three had mild bleeding; two developed band-related mucosal ulcer; one experienced each time, after two subsequent ligations, priapism lasting several hours; and difficulty in urination and tender induration above the dentate line occurred in two other patients. Rubber band ligation is, in effect, a miniature hemorrhoidectomy and has been considered, until recent reports of fatalities associated with this procedure, as an effective, safe, and efficient method of treating symptomatic second-degree and third-degree hemorrhoids. We conclude that the ability to handle complications that occur secondary to the rubber band ligation and, thereby, prevent sepsis and the low rate of major complications in our study justify reliance on this method of treating symptomatic hemorrhoids.

Female↗

PubMed1998

New rubber-band loader to facilitate use of hemorrhoid ligator.

The placement of rubber bands on a ligator is often difficult and frustrating, especially when the operator is wearing gloves. A newly designed rubber-band loader with grooves and a pusher places the bands on the ligator easily, simultaneously, and quickly even under these conditions.

Hemorrhoids↗

PubMed1987

Late results of silicone rubber perianal suture for rectal prolapse.

Twenty-one patients were reviewed five to 12 years after silicone rubber perianal suture for rectal prolapse. Sixteen patients (76 percent) were continent with control of prolapse and two patients (9 percent) suffered only from occasional prolapse or incontinence. Rebanding for silicone cutout or fracture was required in four patients and a second rebanding operation was needed in two. Silicone rubber perianal suture for rectal prolapse stands the test of time and might be recommended for more widespread use in younger patients.

Adult↗

PubMed1983

A randomized comparison of single and multiple rubber band ligations.

One hundred consecutive office patients with internal hemorrhoidal disease were treated by rubber band ligations. They were assigned randomly to one, two, or three ligations at one session. No statistically significant differences in morbidity or complications resulted from multiple ligations, as compared with one ligation. No serious complications were encountered in any of the treatment groups. These results confirm that multiple rubber band ligation is as safe and effective a procedure for managing internal hemorrhoidal disease as single ligations.

Adult↗

PubMed2003

Molecular mapping of genes conferring field resistance to South American Leaf Blight ( Microcyclus ulei) in rubber tree.

The South American Leaf Blight (SALB), caused by the fungus Microcyclus ulei, is the major rubber tree disease in all Central and South America. A population of 192 progeny individuals derived from a cross between a resistant clone and a susceptible cultivated clone was planted in a field trial in French Guiana in order to evaluate the resistance parameters under real infestation conditions. The resistance type (RT), the presence of stromata (ST) and the level of attack (AT) were observed 20-times on a 22-months period, and semi-quantitative evaluation of stromata was registered only once. The search for QTLs was performed using the Kruskal-Wallis test, Interval Mapping and the Composite Interval Mapping method. One major QTL located on linkage group g13 was detected on the RO 38 map, responsible for 36 to 89% of the phenotypic variance of resistance. This resistance QTL corresponds to one that had previously been detected under controlled conditions of infestation and we called it M13-1bn. Surprisingly, the effect of this QTL was larger under natural conditions of infestation than under controlled inoculation. Other minor QTLs (four on the RO38 map and one on the PB 260 map) were also detected. The type of resistance brought by M13-1bn, as well as its durability, are discussed. Applications for rubber tree breeding programs are considered.

Bacteria↗

PubMed2002

Derivative spectrophotometry in the determination of phenyl-beta-naphthylamine used as an antioxidant in rubber mixtures.

A method for the determination of phenyl-beta-naphthylamine (PBN) in ternary mixtures by second-derivative spectrophotometry is described. The procedure works without any separation step of PBN from the other polymer additives. By applying the second-derivative spectrophotometry, Beer's law was valid over the range 0.25-10 micro g mL(-1). The proposed method has been applied to the determination PBN in synthetic ternary mixtures and rubber samples. A comparative study of the results obtained using the second and the third-derivative spectrophotometric methods is presented and evaluated. The derivative spectrophotometric method indicated that the amount of PBN found after extraction from the rubber samples was 0.97+/-0.02 g/100 g of sample.

Journal Article↗

PubMed2003

Pitfalls in assessment of progesterone production by granulosa cells cultured in contact with silicone rubber or paraffin oil.

BACKGROUND: The influence of silicone templates, used for compartmentalization of culture dishes, on progesterone accumulation in granulosa cell cultures is studied and compared with the effect of paraffin oil, which is frequently used to cover oocyte/embryo cultures. METHODS: Human granulosa-lutein cells were cultured in culture dishes compartmentalized by silicone templates, or in polystyrene plates under paraffin oil. Progesterone concentrations in the culture supernatant were compared with controls cultured in polystyrene plates. RESULTS: The progesterone concentration in culture supernatant was grossly reduced in silicone template cultures (2+/-0.7% of control). No inhibitory activity was identified in medium conditioned by preincubation with silicone rubber, but progesterone was absorbed from spiked medium incubated in silicone templates (recovery <2%). Progesterone concentration in culture supernatant was also reduced by a paraffin oil overlay (38+/-3% of control). From steroid spiked microdrops under oil, <2% of progesterone and 85+/-4% of estradiol was recovered. CONCLUSION: The steroidogenesis of cells cultured in silicone templates or under oil cannot be assessed correctly. It has to be considered that the concentration of lipophilic compounds may be grossly changed due to absorption by silicone rubber or paraffin oil.

Cell Culture Techniques↗

PubMed1977

The abortifacient and oxytocic effects of an intravaginal silicone rubber device containing a 0.5% concentration of 15(S)-15-methyl-prostaglandin F2alpha methyl ester.

Abortion was successfully induced by intravaginal insertion of a silicone rubber device impregnated with an 0.5% concentration of 15(S)-15-methyl-prostaglandin F2alpha methyl ester in 20 of 25 patients by prostaglandin alone and in an additional three patients by prostaglandin with a concomitant oxytocin infusion. The mean abortion time for the 23 successful abortions was 15.46 hours. Uterine activity was monitored in six patients and uterine response to the vaginal insertion of the prostaglandin-impregnated device was characterized by a gradual rise in amplitude of contractions and intrauterine baseline tonus accompanied by a rapid increase in the frequency of contractions. Induction of abortion by intravaginal administration of a silicone rubber device impregnated with prostaglandin eliminates the hazards associated with intra-amniotic instillation and offers the advantage of a single administration with the option of reversibility if a patient should be hypersensitive to the drug.

Abortion, Induced↗

PubMed1993

Histopathological effects of silicone rubber 'Ovabloc' on the human fallopian tube.

OBJECTIVE: To study the histopathological effects of silicone rubber on the human fallopian tube. METHODS: A prospective longitudinal study at Benha University Hospital and Boulak Eldakrour General Hospital, Egypt. Nine patients who were on the waiting list for hysterectomy and requested postponing of their operation for personal reasons. RESULTS: Our results suggest that silicone rubber induces histopathological changes in the form of ciliary loss and intracellular changes. CONCLUSIONS: These effects tend to increase with the increase of the duration of tubal plugging and are best seen by electron microscopy.

Adult↗