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PubMed1990

Rubber-degrading enzyme from a bacterial culture.

Rubber-degrading activity was found in the extracellular culture medium of Xanthomonas sp. strain 35Y which was grown on natural rubber latex. Natural rubber in the latex state was degraded by the crude enzyme, and two fractions were separately observed by gel permeation chromatography of the reaction products. One fraction was of higher molecular weight (HMW) with a very wide MW distribution from 10 to 10, and the other fraction was of lower molecular weight (LMW) with a MW of a few hundred. H-nuclear magnetic resonance spectra of the partially purified fractions were those expected of cis-1,4-polyisoprene mixtures with the structure OHC-CH(2)-(-CH(2)-C(-CH(3)) = CH-CH(2)-)(n)-CH(2)-C(=O)-CH(3), with average values of n of about 113 and 2 for HMW and LMW fractions, respectively. The LMW fraction consisted mostly of one component in gas-liquid chromatography as well as in gel permeation chromatography, and the main component was identified as 12-oxo-4,8-dimethyl trideca-4,8-diene-1-al (acetonyl diprenyl acetoaldehyde, A(l)P(2)A(t)) by C-nuclear magnetic resonance and gas chromatography-mass spectra. Not only the latices of natural and synthetic isoprene rubber, but also some kinds of low-MW polyisoprene compounds of cis-1,4 type, were degraded by the crude enzyme. The rubber-degrading reaction was found to be at least partly oxygenase catalyzed from the incorporation of O into A(l)P(2)A(t) under an O(2) atmosphere.

Journal Article↗
PubMed1997

Streptococcus thermophilus and its biosurfactants inhibit adhesion by Candida spp. on silicone rubber.

The adhesion of yeasts, two Candida albicans and two Candida tropicalis strains isolated from naturally colonized voice prostheses, to silicone rubber with and without a salivary conditioning film in the absence and presence of adhering Streptococcus thermophilus B, a biosurfactant-releasing dairy isolate, was studied. Coverage of 1 to 4% of the surface of silicone rubber substrata with adhering S. thermophilus B gave significant reductions in the initial yeast adhesion regardless of the presence of a conditioning film. Mechanistically, this interference in yeast adhesion by S. thermophilus B was not due to direct physical effects but to biosurfactant release by the adhering bacteria, because experiments with S. thermophilus B cells that had released their biosurfactants prior to adhesion to silicone rubber and competition with yeasts did not show interference with initial yeast adhesion. The amounts of biosurfactants released were highest for mid-exponential- and early-stationary-phase bacteria (37 mg.g of cells-1 [dry weight]), but biosurfactants released by stationary-phase bacteria (14 mg.g of cells-1 [dry weight]) were the most surface active. The crude biosurfactants released were mixtures of various components, with a glycolipid-like component being the most surface active. A lipid-enriched biosurfactant fraction reduced the surface tension of an aqueous solution to about 35 mJ.m-2 at a concentration of only 0.5 mg.ml-1. The amount of biosurfactant released per S. thermophilus B cell was estimated to be sufficient to cover approximately 12 times the area of the cross section of the bacterium, making biosurfactant release a powerful defense weapon in the postadhesion competition of the bacterium with microorganisms such as yeasts. Preadsorption of biosurfactants to the silicone rubber prior to allowing yeasts to adhere was as effective against C. albicans GB 1/2 adhesion as covering 1 to 2% of the silicone rubber surface with adhering S. thermophilus B, but a preadsorbed biosurfactant layer was less effective against C. tropicalis GB 9/9.

Adsorption↗
PubMed1995

Comparison of the Burdizzo and rubber ring methods for castrating and tail docking lambs.

The behavioural and plasma cortisol changes in groups of six lambs, five to six days old, were used to compare the acute effects of four methods of castration and tail docking: Burdizzo, standard sized and small rubber rings, and a combined method in which the application of a standard rubber ring was followed immediately by the application of the Burdizzo just distal to it. A control group was also included. Active behaviours such as foot stamping and restlessness increased markedly only after the treatments with rubber rings. Less time was spent in abnormal postures, and the increases in plasma cortisol were least after the combined method. It was concluded that the lambs treated by all the methods suffered considerable acute pain, for up to three hours in some cases, but that the combined method produced the least pain as judged by the behavioural and physiological indices measured, and that the small rubber rings produced more intense pain for a shorter time than the standard rubber rings.

Acute Disease↗
PubMed2005

Reproducibility of sterilized rubber impressions.

Impressions, dentures and other dental appliances may be contaminated with oral micro-flora or other organisms of varying pathogenicity from patient's saliva and blood. Several approaches have been tried to control the transmission of infectious organisms via dental impressions and because disinfection is less effective and has several drawbacks for impression characterization, several sterilization methods have been suggested. This study evaluated the reproducibility of rubber impressions after sterilization by different methods. Dimensional accuracy and wettability of two rubber impression materials (vinyl polysiloxane and polyether) were evaluated after sterilization by each of three well-known methods (immersion in 2% glutaraldehyde for 10 h, autoclaving and microwave radiation). Non-sterilized impressions served as control. The effect of the tray material on impression accuracy and the effect of topical surfactant on the wettability were also evaluated. One-way ANOVA with Dunnett's method was used for statistical analysis. All sterilizing methods reduced the reproducibility of rubber impressions, although not always significantly. Microwave sterilization had a small effect on both accuracy and wettability. The greater effects of the other methods could usually be overcome by using ceramic trays and by spraying impression surfaces with surfactant before pouring the gypsum mix. There was one exception: glutaraldehyde still degraded dimensional accuracy even with ceramic trays and surfactant. We conclude that a) sterilization of rubber impressions made on acrylic trays was usually associated with a degree of dimensional change; b) microwave energy seems to be a suitable technique for sterilizing rubber impressions; c) topical surfactant application helped restore wettability of sterilized impressions.

Ceramics↗
PubMed1993

Retention and strength of silicone-rubber catheters. A report of five cases of retention and analysis of catheter strength.

Five patients had a silicone-rubber catheter that broke during attempted removal. Mechanical testing was performed to determine the tensile strength of silicone-rubber as well as of polyvinyl chloride catheters. Silicone-rubber catheters were found to have a low tensile strength. The pull-out force of ten indwelling silicone-rubber catheters was also measured. The pullout force measured from a patient who had a cast was close to 40 per cent of the strength of the silicone-rubber catheters.

Bone Diseases↗
PubMed2002

Effects of tail docking using a rubber ring with or without anesthetic on behavior and production of lactating cows.

Production and behavioral measures were recorded to determine the level of stress and pain associated with tail docking adult dairy cows with a rubber ring. The possible advantages of using an epidural anesthetic were also examined. Sixty-four lactating, mixed-parity, Holstein cows were randomly assigned to one of four treatment groups. The treatments were rubber ring docking with epidural anesthetic (RRA), rubber ring docking without anesthetic (RR), control with epidural anesthetic (CA), and control without anesthetic (C). Behavior was examined on d 0, +1, +2, and +6. Milk production and feed intake were monitored. Cows exhibited subtle behavioral changes following application of rubber rings, as well as after epidural administration on d 0 and tail amputation on d +6. After treatment on d 0, the RR, RRA, and CA groups displayed less tail shaking than the C group. The RR and RRA cows continued to exhibit less tail shaking on d +1, +2, and +6. Also on d 0, the RR and RRA groups held their tails in the raised position less than the C and CA groups. After amputation on d +6, the RR and RRA groups spent longer with their tails pressed to their bodies than the C and CA groups. No significant differences in milk production or feed intake were found. Results suggest that tail-docking adult dairy cattle with rubber rings causes, at most, mild discomfort and that there is no benefit in using an epidural anesthetic. However, long-term effects need to be investigated.

Amputation, Surgical↗
PubMed2002

Enamel fluoride retention after application of fluoride-containing rubber cups.

PURPOSE: To compare the fluoride retention in bovine enamel after using fluoride-containing rubber cups or a conventional rubber cup in combination with a fluoride-containing polishing paste. MATERIALS AND METHODS: From each of 20 bovine incisors, 5 enamel slabs with a diameter of 3 mm were sectioned and assigned to 5 groups (A,B,C,D,E). Group A was left untreated and served as the negative control. Group B was polished with a rubber cup combined with a fluoride-containing prophylaxis paste for 10 s (Hawe Cleanic). Groups C and D were treated in the same manner by using a fluoride-containing rubber cup with 2,262 ppm or 9,048 ppm fluoride as NaF. Group E enamel was brushed for 10 s with a toothbrush and a slurry of distilled water and fluoride gel with 12,500 ppm fluoride as NaF and AmF (Elmex Gelee) and served as the positive control. Th e specimens were analyzed using the method of Caslavska et al. After determining the KOH soluble fluoride on the enamel surface, the content of structurally bound fluoride was analyzed in three consecutive layers of 30 microm. ANOVA with Bonferroni correction was used for statistical analysis (P< 0.05). RESULTS: For the KOH-soluble fluoride, Groups B and D accumulated more KOH-soluble fluoride than the negative control and less than the positive control. With respect to the structurally bound fluoride, the accumulation in Group D was higher when compared to all other groups. It was concluded that a rubber cup with 9,048 ppm fluoride may be an effective alternative to the use of a fluoride-containing prophylaxis paste.

Amines↗
PubMedDate not supplied

Preservation of compliance in a small diameter microporous, silicone rubber vascular prosthesis.

Compliance is believed to be a significant factor in maintaining the patency of small diameter vascular grafts. This study evaluated the compliance changes with time of microporous Replamineform silicone rubber prostheses. The compliance of 15 canine femoral artery interpositions (4 mm internal diameter X 6 cm length) was measured by in-vivo electromagnetic rheoangiometry immediately following implantation and at intervals to eight months. At implantation, silicone rubber grafts were overcompliant (15.0 +/- 1.1% radial change/mmHg X 10(-2); mean +/- S.E.) compared to the proximal artery (7.7 +/- .6%). The compliance of the prostheses decreased within two weeks (6.3 +/- .9%) and remained isocompliant to the proximal artery for eight months. The compliance determinations for the silicone rubber grafts were compared with those from PTFE prostheses and vein grafts acquired by the same method in a previous study. The analysis demonstrates the preservation of isocompliance of the silicone rubber prostheses compared to the native arteries. In contrast, the minimally compliant vein grafts and PTFE prostheses continued to decrease in compliance following implantation. This microporous silicone rubber graft may improve the success of small internal diameter arterial reconstructions by eliminating failures caused by compliance mismatch between the artery and the prosthesis.

Animals↗
PubMed1998

Comparison of vacuum extraction delivery between the conventional metal cup and the new soft rubber cup.

To compare the effectiveness and complications of vacuum extraction delivery between the conventional metal cup and the silicone rubber cup. A prospective randomized clinical trial of 90 pregnant women requiring assisted vaginal delivery who met the predetermined criteria for vacuum extraction were allocated to delivery by the Malstrom metal cup (46 cases) or the silicone rubber cup (44 cases). The two groups were similar in respect of age, parity gestational age and indications for assisted vaginal delivery. The mean and median numbers of tractions and time from cup application to delivery were not significantly different between the groups. The overall success rate was higher in the metal cup (89.1%) than in the rubber cup (79.5%) but not significantly different. The silicone cup was more likely to fail in cases of occiput posterior position, excessive caput, and severe degree of molding. There were no significant differences between groups in terms of Apgar scores, birth canal injury, and maternal blood loss. Scalp injuries occurred more frequently with the metal than with the rubber cup (P = 0.006). Vacuum extraction delivery with the silicone rubber cup is associated with reduced scalp injuries but has a greater tendency to fail when the fetus presents in occiput posterior position, has excessive caput or severe degree of molding.

Adolescent↗
PubMed1998

Pulmonary effects of inhaled dust and fumes: exposure-response study in rubber workers.

Lung function changes and respiratory symptoms were investigated in a cross-sectional study in rubber workers exposed to dust and fumes. To exclude acute pulmonary effects related to "rubber fumes," lung function was measured in curing workers at the start and end of the day shift. Exposure to inhalable dust was measured in all production areas. The results were compared with a reference population from the same geographical region. This study indicates that exposure to "rubber fumes" in curing workers was not related to cross-shift and cross-week decreases in pulmonary function at levels approximately 1 mg/m3 (AM) inhalable dust and 260 micrograms/m3 cyclohexane soluble fraction (CSF). Cross-sectional analyses gave indications for a small loss in pulmonary function in all rubber workers. This decrease in lung function was associated with 10 years of exposure to an average of 2.0 mg/m3 inhalable dust. Our study showed a mean annual decline of 0.08% for the FEV1/FVC ratio and of 10 ml/s for the MMEF. Self-reported chronic respiratory symptoms were not related to dust exposure.

Adult↗
PubMed1984

Mortality among rubber workers: VIII. Industrial products workers.

This report compares the mortality experience of 6,533 men employed in the industrial products division of a rubber manufacturing company with that of U.S. males and of other rubber workers. For most causes of death the mortality rates of industrial products workers were lower than those of U.S. males and similar to those of other rubber workers. Relative to other rubber workers, men in the industrial products division had a 50% excess of deaths from lymphoma, a 90% excess of deaths from multiple myeloma, and a 20% excess of deaths from bladder cancer during the study period. The excesses of lymphoma and multiple myeloma were strongest during recent follow-up in 1970-78 (observed/expected deaths: 10/4.3 for lymphoma; 10/4.4 for multiple myeloma), whereas bladder cancer mortality was not excessive during this calendar period.

Aged↗
PubMed1995

Measurement of protein in natural rubber latex.

Latex from the Brazilian rubber tree (Hevea brasiliensis) is the source of virtually all commercial natural rubber (cis-1,4-polyisoprene). Products made from natural rubber latex include gloves, condoms, and hundreds of different medical devices. However, recent reports of widespread life-threatening latex-associated Type I allergies have focused attention on latex proteins as serious allergens. In this paper, we describe a method that permits accurate and reproducible determination of protein in latex and that includes a procedure for solubilizing latex proteins and removing rubber. Also, we show that interfering substances in latex can be removed by precipitating proteins with sodium deoxycholate and trichloroacetic acid, and that latex proteins can be recovered and quantified with 2,2'-bicinchoninic acid.

Electrophoresis, Polyacrylamide Gel↗
PubMed1996

Biodegradation of rubber particles in soil.

The biodegradation of rubber particles in rubber-soil mixtures at different rubber contents was monitored by the carbon dioxide production. The cumulative carbon dioxide production was modelled according to a two parameter exponential function. The model provides an excellent fit (R2 > 0.98) for the observed data. The two parameters yield a reliable estimate of the half-life for the process observed, but estimation of the true half-life of rubber in soil will need more research.

Biodegradation, Environmental↗
PubMed1993

Phospholipid impregnation of abdominal rubber drains: resistance to bacterial adherence but no effect on drain-induced bacterial translocation.

In order to evaluate the effect of surface modification of biomaterials on bacterial adherence and bacterial translocation after intraperitoneal biomaterial implantation, phosphatidylcholine- or phosphatidylinositol-impregnated rubber drain pieces, which had been intraperitoneally implanted in the rat for 2 and 7 days, or unimplanted, were incubated in vitro with 3H-labelled Escherichia coli and Enterobacter cloacae. As compared with unimpregnated pieces, the adherence of bacteria significantly decreased to phosphatidylcholine- and phosphatidylinositol-impregnated rubber drain pieces that were either unimplanted or implanted for 2 days, but not for 7 days. The supplementation of albumin in the medium reduced the adherence of bacteria to the unimplanted, unimpregnated drain pieces, but did not further decrease adherence of bacteria to the unimplanted, phospholipid-impregnated brain pieces. Bacterial growth was inhibited after incubation in nutrient broth supplemented with phospholipids. The incidence of enteric bacterial translocation induced by intraperitoneal drain implantation did not differ between phospholipid-impregnated and unimpregnated drain pieces. Scanning electron microscopy revealed a large amount of biofilm and fibrous deposition on the surface of the implanted, phospholipid-impregnated rubber drain pieces. Thus, phospholipid impregnation of rubber drains reduces bacterial adherence and inhibits bacterial growth, without influencing the incidence of bacterial translocation.

Abdomen↗
PubMed2005

Biological monitoring of carbon disulphide and phthalate exposure in the contemporary rubber industry.

OBJECTIVES: We studied the range in urinary levels of 2-thiothiazolidine-4-carboxyl acid (TTCA), a metabolite of CS2 and phthalic acid (PA), a common metabolite of phthalates, across factories and departments in the contemporary rubber manufacturing industry. METHODS: Spot urine samples from 101 rubber workers employed in nine different factories were collected on Sunday and during the workweek on Tuesday, Wednesday and Thursday at approximately 4 pm. In total, 386 urine samples were successfully analyzed. RESULTS: Levels of both biomarkers increased significantly by a factor 2 (paired t-test P-value <0.05) during the working week as compared to the Sunday biomarker levels with absolute increases of approximately 70 microg/l and 5 micromol/mol creatinine for PA and TTCA, respectively. Levels in both biomarkers did not differ markedly between working days. Increases seemed to be restricted to specific factories and/or departments (e.g. molding and curing). CONCLUSIONS: The results of this study demonstrate that rubber workers in the contemporary rubber industry are exposed to phthalates and low levels of CS2 ( approximately 0.05 ppm) as measured by PA and TTCA, respectively. Exposures to both compounds are largely driven by specific circumstances in factories. Therefore, when estimating exposures to phthalates and CS2 detailed information should be collected on the type and amount of phthalate containing ester plasticizers, dithiocarbamates and thiurams used. Preferably, personal exposure data should be collected. In this case, biological monitoring seems a reasonable approach. However, in the case of PA attention should be given to individual background levels as this could lead to a substantial overestimation of the occupational contribution to total phthalate exposure.

Air Pollutants, Occupational↗
PubMed1997

Assessment of exposure to carcinogenic N-nitrosamines in the rubber industry.

Exposures to volatile nitrosamines were measured at 24 rubber manufacturing plants from 1992 to 1995. A total of 709 exposure measurements were taken in general areas or personal breathing zones to estimate exposure according to production types (seals, joints, tyres, gloves, etc.) and production steps, from mixing to storage. Five different nitrosamines were identified. N-Nitrosodimethylamine is the most frequently encountered nitrosamine and represents the most important fraction of the total nitrosamine concentration measured in a given sample. This fact is consistent with the use of rubber additives containing corresponding amine precursors. One hundred and forty-one of the 709 values exceeded the German target value (TRK) of 2.5 micrograms/m3 for all nitrosamines present from rubber vulcanisation, the only available standard for occupational nitrosamine exposures. The salt bath curing process generates particularly high nitrosamine levels, 90% of the 96 measurements being over the TRK, with many values exceeding 20 micrograms/m3. The reasons why the TRK is exceeded are generally well identified. To reduce nitrosamine emission levels it would be advisable to eliminate nitrogen oxide sources, principally by using a process other than salt bath curing, and to develop different rubber stocks that do not contain secondary aliphatic amine functional groups ("safe amines").

Adult↗
PubMed2003

Short-term and long-term results of combined sclerotherapy and rubber band ligation of hemorrhoids and mucosal prolapse.

PURPOSE: Rubber band ligation is a common office procedure for symptomatic hemorrhoids. The aim of the study was to assess our short-term and long-term results of combined sclerotherapy and rubber band ligation in the management of hemorrhoids and incomplete mucosal prolapse. METHODS: Data on 6,739 patients who had previous combined sclerotherapy and rubber band ligation by the senior authors (GLN and PRD) were retrieved from the database dating between January 1976 and June 2000. These patients either had hemorrhoids or incomplete mucosal prolapse. Furthermore, questionnaires were sent to a random sample of 2,400 patients. Telephone interviews were performed for 600 of the nonrespondents. RESULTS: Of 6,739 patients (3,683 males; mean age, 46.7 years) in the database, 4,686 (70 percent) received the procedure once, and 2,053 (30 percent) received the procedure more than once. There were 5,689 patients (84 percent) who had their procedures performed consecutively within a planned period, and only 1,050 patients (16 percent) had repeat procedures after a period of more than 12 months from their last treatments. Thus, the recurrence rate was 16 percent. The overall complication rate was 3.1 percent, with minor bleeding being the major complaint. With regard to the questionnaire, 44 percent responded. The mean follow-up period was 6.5 (range, 1-11) years. There were patients who had residual symptoms of bleeding (19 percent), itch (21 percent), and lump (20 percent). However, 58 percent of patients who replied were asymptomatic. With satisfaction scores ranging from +3 to -3 (+3 indicating complete satisfaction and -3 indicating complete dissatisfaction), 90 percent scored >/=1, 9 percent scored 0 or less, and 1 percent did not specify a score. Hemorrhoidectomy was required in 7.7 percent of the responders. Of 600 phone interviews with the nonrespondents, 152 responded to the questionnaires. Although there was less satisfaction from the phone respondents, which may have accounted for the initial nonresponse, no statistical difference was detected in residual symptoms. CONCLUSIONS: Combined triple sclerotherapy and rubber band ligation is an effective treatment for early hemorrhoids and incomplete mucosal prolapse, with low rates of recurrence, complications, and hemorrhoidectomy, and it can be repeated easily.

Adolescent↗
PubMed2006

Longitudinal multiple rubber band ligation: an alternative method to treat mucosal prolapse of the anterior rectal wall.

PURPOSE: The aim of this study is to present a new approach for the treatment of mucosal prolapse of the anterior rectal wall using a multiple longitudinal rubber band ligation procedure. METHODS: The therapeutic approach using multiple longitudinal rubber band ligations on anterior rectal wall was undertaken in 17 patients after failure of conventional medical treatment. RESULTS: Double rubber band ligation was undertaken in seven patients and triple ligation in nine patients. In a median follow up of 12 months fourteen patients (87.5 percent) showed complete and persistent remission of symptoms. Two patients remained symptomatic and were treated by a second session of rubber band ligation which was successful in one of them. No complications occurred in this present series except in one patient with internal rectal prolapse patient who complained of persistent pain for seven days. CONCLUSIONS: These encouraging results have suggested this method as an effective alternative in the relief of this usually very symptomatic disorder.

Adult↗