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At least 343 records · Page 19Linked to original sources
PubMed2006

Incorporation of deuterium-labelled analogs of isopentenyl diphosphate for the elucidation of the stereochemistry of rubber biosynthesis.

A series of six deuterium-labelled analogs of isopententyl diphosphate (IPP) was prepared to investigate the detailed stereochemical course of addition of C5 units during rubber biosynthesis in Hevea brasiliensis and Parthenium argentatum. These analogs were incorporated into the cis-polyisoprene chain by rubber transferase in rubber particles, and the stereochemistry was determined by 2H-NMR analysis of the polymer or of levulinic acid derivatives obtained from its ozonolytic degradation. Results indicate that rubber chain elongation occurs with loss of the pro-S hydrogen of IPP, addition of the allylic diphosphate to the si face of IPP and inversion of stereochemistry at the carbon bearing the diphosphate.

Alkenes↗
PubMed2000

Natural rubber latex allergy in children: a follow-up study.

BACKGROUND: Natural rubber latex (NRL) allergy occurs frequently in children with spina bifida and other children with disorders requiring multiple operations. Also atopic children who have not undergone surgery can be sensitized to NRL, but the outcome of these children has not been studied. OBJECTIVE: To study how NRL-allergic children manage at home and whether their skin prick test (SPT) reactivity, latex RAST or IgE antibody levels to NRL allergens change during the follow-up. METHODS: Twenty-four NRL-allergic children who had not undergone surgery and eight children with histories of multiple operations were followed up for a mean of 2.8 years. Clinical symptoms were recorded and all children were re-examined with SPT, latex RAST and ELISA for IgE antibodies to prohevein (Hev b 6.01), hevein (Hev b 6.02) and rubber elongation factor (REF, Hev b 1). RESULTS: Nineteen of the 24 NRL-allergic children (79%) who had not undergone surgery had occasionally contacts to balloons and other NRL products at home, and 10 of them experienced symptoms ranging from contact urticaria to systemic reactions. Three of the eight NRL-allergic children with a history of multiple operations had contacts to rubber balloons without any symptoms, and five children underwent 1-8 uneventful operations in a latex-free environment. SPT reactivity to NRL allergens, latex-RAST or IgE antibody levels to prohevein or hevein did not change in either group of NRL-allergic children during the follow-up. CONCLUSIONS: Occurrence of clinical symptoms and no decrease in SPT reactivity or IgE levels to NRL allergens in the course of the present follow-up study imply that more attention should be paid to the protection of NRL-allergic children from rubber contacts in the home environment.

Adolescent↗
PubMed1997

Use of oxygen-permeable silicone rubber pouches for growing mass cultures of bacteria.

Growth of most bacteria often involves the use of expensive incubated shaker systems. In this report, oxygen-permeable silicone rubber pouches, with oxygen permeability over 100 times higher than other polymers, were employed for growing bacterial cultures. With little, if any, agitation oxygen-permeable silicone rubber pouches produced bacterial growth rates equivalent to growth rates obtained in shaker flasks. The silicone rubber pouch described has a glass cuvette integrated into its design that permits readings of bacterial density without opening the pouch. One can sterilize and store powdered bacterial culture medium in silicone rubber pouches; therefore, bacterial cultures can be initiated by simply adding water and bacteria.

Bacteriological Techniques↗
PubMed2002

Management of occupational allergy to natural rubber latex in a medical center: the importance of quantitative latex allergen measurement and objective follow-up.

When our employees began coming to the Occupational Health Service, Dermatology, and Allergy Clinics with symptoms of allergy to rubber gloves 12 years ago, the Mayo Clinic initiated 3 responses. (1) The Allergic Disease Research Laboratory adapted well-established technology to measure both the IgE antibody specific to natural rubber allergens, and by use of this IgE antibody, the allergens in rubber products and in the air of the workplace. (2) The Division of Allergic Diseases and Internal Medicine reviewed the prevalence and severity of the problem. (3) The Clinical Practice Committee appointed a multidisciplinary task force to implement measures to reduce exposure. The 3 sections of this article describe the Mayo Clinic's experience of successful control of this occupational health problem. Use of only gloves with low or undetectable allergen content greatly reduced the concentration of allergen in the work site, reduced the number of new cases of occupational allergy to rubber, and allowed individuals with latex allergy to work at their usual jobs.

Air Pollutants, Occupational↗
PubMedDate not supplied

Analysis of residual vulcanization accelerators in baby bottle rubber teats.

An analytical method was established for the determination of dialkyldithiocarbamates (DTCs) in chloroform-acetone extracts from rubber teats for baby bottles. DTCs in the extracts were derivatized into ethyl esters and analysed by gas chromatography employing nitrogen-phosphorus detection. Dimethyldithiocarbamate and diethyldithiocarbamate were detected at levels up to 3.2 micrograms/g rubber and up to 4.6 micrograms/g rubber (as dithiocarbamic acid), respectively, in the extracts from commercially available isoprene rubber tests. DTCs can form secondary amines by acid hydrolysis, although the levels of DTCs in the extracts only made a minor contribution to the total level of measured secondary amine precursors.

Acetone↗
PubMedDate not supplied

Toxicological aspects of chemical hazards in the rubber industry.

Only three recognized strong carcinogens are used in the Swedish rubber industry: mineral oil, ethylene thiourea, and trichloroethylene. Besides, many curing agents, accelerators, antioxidants/antiozonants, and retarders may possess mutagenic and/or carcinogenic activity and may thus contribute to the total cancer risk in the rubber industry. Irritating compounds as well as modifiers of biotransformation further contribute to the complex exposure panorama of the rubber industry. Cancer risks in the work environment of the rubber industry can probably be more effectively reduced by general sanitary measures aimed at reduction of total exposure than by specific regulation of only a few established carcinogenic chemicals.

Antioxidants↗
PubMed1992

Effect of the mosquito repellent DEET and long-wave ultraviolet radiation on permeation of the herbicide 2,4-D and the insecticide DDT in natural rubber gloves.

Studies were conducted to determine the effect of a commonly used insect repellent, DEET (N,N-diethyl-m-toluamide), on the permeability of rubber gloves used as chemical protective clothing (CPC) by pesticide applicators. Glove permeation analysis was conducted with an automated in vitro diffusion analysis (AIDA) method employing an in-house, flow-through permeation cell design. Permeation of 14C-ring-labeled 2,4-D (2,4-dichlorophenoxyacetic acid) in natural rubber glove material was 2.4 +/- 1.81% at 48 hr after treatment of the glove with 2,4-D applied with DEET; this was not significantly different (Student's t-test; p less than 0.05) from 3.2 +/- 3.46% permeation of 2,4-D observed without DEET. Similarly, there was no significant difference between the permeation of pp'-DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) applied with DEET (11.7 +/- 5.02%) and without DEET (11.4 +/- 4.86%) to natural rubber glove material. Scanning electron microscopy of the natural rubber glove material, however, demonstrated disruption of the surface ultrastructure following a 24-hr treatment with DEET. The AIDA analysis also suggested that exposure of the glove material to long-wave ultraviolet (UVA) radiation enhanced the glove permeability to 2,4-D (6.2 +/- 0.73% [+UVA]; 0.3% +/- 0.14% [-UVA]) but had no effect on the permeation of DDT. Because the CPC of pesticide applicators is commonly exposed to solar UVA, this finding may raise concerns about the efficacy and safety of CPC in general.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1993

Modeling the temperature dependence of N-methylpyrrolidone permeation through butyl- and natural-rubber gloves.

This paper describes the temperature dependence of N-methylpyrrolidone (NMP) permeation through gloves used in microelectronics fabrication facilities. One type of butyl-rubber glove (North B161), two types of natural-rubber gloves (Edmont Puretek and Ansell Pacific White), and a natural rubber/nitrile/neoprene-blend glove (Pioneer Trionic) were tested at four temperatures from 25-50 degrees C using the ASTM F739-85 permeation test method. The butyl-rubber glove showed no breakthrough after four hours of exposure at any temperature. The variations with temperature of measured breakthrough times (BT) and steady-state permeation rates (SSPR) for the other gloves were described well by Arrhenius relationships, with BT values decreasing by factors of 7-10 and SSPR values increasing by factors of 4-6 over the temperature range studied. Extrapolation to 70 and 93 degrees C, the temperatures at which degreasing is often performed, yielded BT values of < 2 min and < 0.5 min, respectively, in all cases. With the exception of the butyl-rubber glove, following an initial exposure at 25 degrees C and air drying overnight, low levels of NMP vapor were detected off-gassing from the inner surfaces of the gloves. Experimental results were then compared to those expected from several permeation models. Estimates of the equilibrium solvent solubility, S, were calculated using a model based on three-dimensional solubility parameters. Estimates of the solvent diffusion coefficient, D, were obtained from correlations with either the solvent kinematic viscosity or the product of the Flory interaction parameter, chi, and the solvent molar volume. Combining these values of D and S in Fickian diffusion equations gave modeled BT estimates that were within 23% of experimental values over the temperature range examined. Modeled SSPR values were within 50% (typically within 25%) of experimental values. Another model based on a generalized Arrhenius relationship also provided useful but generally less accurate estimates of the changes in BT and SSPR values with temperature.

Elastomers↗
PubMed2006

Assessment of occupational genotoxic risk in the production of rubber tyres.

A broad spectrum of substances is used in the rubber industry, many of them being genotoxic and/or carcinogenic. Convincing evidence of an excess of certain forms of cancer among rubber workers has been provided. The objective of this study was to determine the genotoxic effects in a group of individuals engaged in the production of rubber tyres from a Portuguese factory. Peripheral blood samples were collected from 32 exposed workers and 32 controls, and micronucleus (MN) test, sister chromatid exchanges (SCE) and comet assay were performed. Urinary thioethers were measured as a general biomarker of exposure to electrophilic compounds, and genetic polymorphisms in metabolizing enzymes (CYP2E1 Dra I, EPHX1 codons 113 and 139, GSTP1 codon 105, and GSTM1 and GSTT1 deletion polymorphisms) were analysed as susceptibility biomarkers. Excretion of thioethers was found significantly higher in rubber workers. Also, a non-significant increase in MN frequency related to time of exposure and no effect in SCE were observed in the exposed. Comet assay data showed decreased TL values in the exposed population with respect to the control group, this might indicate the induction of crosslinks by the substances present in the workplace environment. Significant increase in MN frequency was obtained for GSTT1 null exposed individuals with respect to positive ones, and interaction with GSTP1 polymorphism was found. Higher levels of cytogenetic test frequencies were observed in epoxide hydrolase expected low activity donors with respect to medium and high activity individuals. No effect of CYP2E1 or GSTM1 variants was obtained in the biomarkers analysed.

Adult↗
PubMed1997

Visual evoked potentials in rubber factory workers.

Pattern reversal visual evoked potentials (pVEP) were studied in 39 male rubber factory workers in the age range of 18-55 years and 20 control subjects (aged 18-46 years) not exposed to the rubber factory environment. Results revealed that 20 (51%) rubber factory workers had abnormal latencies of wave P1 (dominant component of pVEP) as per accepted criteria of 99% tolerance limit set for the control group (i.e. any value above mean +3 SD of control was considered abnormal). The section-wise per cent distribution of abnormalities was vulcanization (83%), tubing (75%), calendering (60%), loading (38%) and mixing (14%). This study provides electrophysiological evidence that rubber factory environments affect the conduction processes in optical pathways from their origin in the retina to striate cortex. However, this study has its limitations in not identifying the specific chemical(s) causing these changes in VEP.

Adult↗
PubMed1987

The permeability of detachable latex rubber balloons. An in vitro study.

Previous studies have shown that a silicone rubber balloon filled with a hyperosmolar solution of contrast medium expands and may rupture because the wall acts as a semipermeable membrane. The deflation of latex rubber balloons in vivo has been attributed to the same cause. The authors investigated the behavior of latex rubber balloons filled with metrizamide solutions ranging from hyperosmolar to hypo-osmolar relative to plasma. When balloons were immersed in plasma, tritiated water passed bidirectionally through the wall at a rate unrelated to the concentration or volume of the contrast medium in the balloon. There was no exchange of sodium ions across the wall, and the osmolality of the metrizamide did not change over a period of up to six weeks. The authors conclude that deflation of a latex rubber balloon during the first few hours or days is not due to osmosis.

Animals↗
PubMed2000

Allergic reaction after rubber dam placement.

In the last few years allergic reactions to natural rubber latex (NRL) have increased in dental practice affecting both the dental team and patients. Some case reports discuss the potential risks of hypersensitivity to NRL products. An adverse patient reaction after dental rubber dam placement is reported. About 1 min after the isolation of the tooth with a rubber dam the patient presented signs and symptoms of hypersensitivity. Oxygen and intravenous hydrocortisone were administered and the patient kept under observation. After 2 h she had stable vital signs and no more allergics symptoms. It is unclear whether components of the NRL dam or the cornstarch powder incorporated with the rubber dam was responsible for the allergic reaction. Dentists must be aware of the health problem and be prepared for an adequate management in dental practice.

Adult↗
PubMed1994

Promotion of Escherichia coli adherence to rubber slices by adsorbed fibronectin.

Biomaterial-associated infections are a problem in the use of endoprosthetic materials in the palliative treatment of malignant obstructive jaundice. Fibronectin has been reported to mediate adherence of bacteria to host tissue and biomaterials. Adsorption of fibronectin to rubber--representing material used for biliary drainage--and subsequent adherence of Escherichia coli strain PSS1 and E. coli strain NG7C (which binds to immobilised fibronectin) were investigated. Quantitative adsorption of fibronectin to rubber slices was studied with 125I-labelled, purified human plasma fibronectin. In buffer solutions, fibronectin showed a high affinity for rubber slices. Adherence of the E. coli strains to uncoated rubber slices was similar and was significantly inhibited by the presence of plasma components and bile. Adherence of E. coli PSS1 to fibronectin-coated slices was poor. In contrast, E. coli NG7C adhered efficiently to coated slices in proportion to the amount of adsorbed fibronectin; adherence was not reduced by the presence of albumin or bile, or the fibronectin-binding ligands gelatin, heparin and fibrinogen. However, pre-digestion of coated slices with trypsin significantly reduced adherence.

Adsorption↗
PubMed2005

Shock-wave theory for rupture of rubber.

This Letter presents a theory for the rupture of rubber. Unlike conventional cracks, ruptures in rubber travel faster than the speed of sound and consist of two oblique shocks that meet at a point. Physical features of rubber needed for this phenomenon include Kelvin dissipation and an increase of toughness as rubber retracts. There are three levels of theoretical description: an approximate continuum theory, an exact analytical solution of a slightly simplified discrete problem, and numerical solution of realistic and fully nonlinear equations of motion.

Acoustics↗
PubMed2006

Delayed type allergic reaction following the use of nonlatex rubber dam during endodontic treatment.

AIM: To describe the development of a delayed type allergic reaction 24 h following the use of nonlatex rubber dam during endodontic treatment. The symptoms were alleviated with adequate medication; however, the patient rejected any further analysis. SUMMARY: In recent years, allergic reactions because of latex rubber dam and gloves have received more attention. Nonlatex products are advocated in clinical use in cases where the patient presents an allergic background. Although rare, adverse reactions may be encountered even with these products. In this article, a very rare case is presented in which a patient developed signs of allergy 24 h after the utilization of nonlatex rubber dam and gloves during endodontic treatment. Signs including visible redness on the mucosa, submucosal oedema and desquamation in the vestibular mucosa were observed. With proper medication, the signs and symptoms were alleviated. Although the patient was referred to an allergy specialist for patch testing, she did not accept any further analysis. KEY LEARNING POINTS: This case emphasizes the necessity of precautions during the management of latex-allergic patients in clinical practice. The unusual response encountered in this patient does not undermine the usefulness of nonlatex rubber dam and gloves in sensitive individuals.

Dermatitis, Allergic Contact↗
PubMed1979

Allergy to rubber condom urinals and medical adhesives in male spinal injury patients.

In the National Spinal Injuries Unit at Stoke Mandeville Hospital, rubber condom urinals, kept on the penis with a medical adhesive, are used for incontinent male patients where possible. However, contact allergy to rubber condoms and/or the adhesives is a common problem and can cause considerable morbidity in paralysed patients. This paper investigates the rubber chemicals and adhesives most commonly implicated in causing contact allergy. The survey was divided into two parts: 1. Patch testing symptomatic inpatients 2. A questionnaire sent to new patients from January 1974 to ascertain the overall incidence of contact allergy. It was found that allergy to mercaptobenzthiazole (MBT)- and thiuram-containing condoms was relatively common and that latex/petroleum tube medical adhesives most commonly caused adhesive allergy. It is suggested that a condom made of the least allergenic rubber and an adhesive causing the least number of allergic reactions should be used from the outset for paralysed patients requiring a condom urinal.

Adhesives↗
PubMed1988

Rubber contact urticaria. Allergenic properties of 19 brands of latex gloves.

To compare the immediate skin test reactivity of various latex (natural rubber) surgical and cleaning gloves, prick tests were performed on 40 latex-allergic persons, 26 of whom were sensitized by surgical and 14 by cleaning latex gloves. 6/17 surgical gloves tested and 1/2 cleaning gloves caused positive reactions in almost all (over 87%) of the allergic subjects. In contrast, the frequencies of positive reactions to 4 other surgical latex gloves were as low as 8-21%, suggesting that not all surgical gloves are equally allergenic. Control prick tests with 1 synthetic rubber and 1 polyvinyl chloride (PVC) glove were negative in all subjects. 2 surgical latex gloves causing either a high or low number of positive prick tests in allergic subjects were analyzed with high-pressure liquid chromatography (HPLC). Similar allergenic protein fractions were detected, which showed protein peaks at MW 2000, 5000 and 30,000 daltons. Corresponding proteins were detected in 1 latex cleaning glove analyzed and in natural rubber. This result confirms that allergenic proteins persist in various surgical and cleaning latex gloves after manufacture from natural rubber and may cause contact urticaria symptoms in sensitized people.

Adult↗
PubMed1976

Cancer mortality among rubber workers: an epidemiologic study.

Several previous epidemiologic studies of the rubber industry--an industry that uses many chemicals--have identified excess mortality from certain specific cancers. In this study, four cohorts of active and retired workers, at four major rubber-tire plants, were identified historically and followed for the ten-year period from 1964 to 1973. The cancer mortality of these four population was compared, separately and combined, with that of the general community. For all cancers combined, there was a slight excess above the expected number of deaths, whereas for some specific cancers (stomach, colon, prostate, and neoplasms of the lymphatic and hematopoietic system) there was a marked excess of deaths. Proportional mortality analysis at other small plants revealed similar excesses for these cancers, and some excess for lung, bladder, and CNS cancers. Analysis of detailed individual work histories reveals an association of certain cancers with specific job exposures; in particular, lymphatic leukemia and solvent exposure, and lung cancer and curing-room exposure. For both bladder cancer and stomach cancer, preliminary analyses indicate an association with groups of jobs in adjacent production stages (handling and mixing raw ingredients, and processing the "green" precured rubber, respectively). Further analytic studies are currently under way to identify groups of rubber workers at increased risk of other specific cancers.

Adult↗