Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RUBBER”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38Linked to original sources
PubMed2000

Degradation of latex and of natural rubber by Streptomyces strain La 7.

Streptomyces strain La 7 was isolated from the banquete of a city high way in Karlsruhe. According to partial 16S rRNA gene sequencing it was identical with Streptomyces albogriseolus and Streptomyces viridodiastaticus. DNA-DNA-similarity studies revealed 80.3-82.4% similarity between each of two of the three strains. Although phylogenetically closely related, Streptomyces strain La 7 differed from the two reference strains by morphological as well as physiological features and might represent a new species aside of S. albogriseolus and S. viridodiastaticus. The new Streptomyces strain La 7 was grown in a medium containing a latex emulsion or squares of natural rubber gloves as the only carbon source. On agar plates with a latex overlay agar, translucent halo formation around the colonies was observed. The unvulcanized latex was metabolized and the carbon from the isoprene units was apparently used for cell growth. In shake cultures with unlimited oxygen supply, during 60 days of incubation, 140 mg of the 175 mg totally emulgated latex were degraded exponentially. In sterile control flasks about 3% of the initial amount of latex could not be recovered after incubation on a shaker, presumably due to photochemical transformation. During static incubation of sterile medium, the latex formed a sticky layer at the surface of the medium and on the glass walls and recovery of the material was more difficult. Estimation of the protein content of cells from total nitrogen resulted in about 50% of the degraded latex being incorporated into cells, if a standard cell composition was assumed. Direct protein analysis according to Bradford (1976) gave much lower estimates, presumably due to a low content of aromatic amino acids. Stripes of natural rubber were degraded by Streptomyces strain La 7 during 70 days to an extent of about 30%. Scanning electron microscopy demonstrated, that hyphes of Streptomyces strain La 7 colonized and penetrated the latex surface with a concomitant deterioration of the latex material.

Bacterial Typing Techniques↗
PubMedDate not supplied

Natural rubber latex allergy: spectrum, diagnostic approach, and therapy.

Latex allergy has reached epidemic proportions in the United States and is increasingly recognized as a significant contributor to morbidity and mortality during medical and surgical procedures. Ultimately, many of the affected patients with recognized latex sensitivity and those who are not yet diagnosed will receive treatment for their allergic reactions to latex in emergency departments. Consequently, emergency physicians must have a comprehensive understanding of the etiology, epidemiology, pathogenesis, treatment, and management of these challenging patients. Groups at high risk include spina bifida cystica patients, health care workers, latex industry workers, specific food-allergy patients, and patients with a history of atopy or multiple surgical procedures. Sensitization to latex antigens is commonly encountered in health care workers wearing latex gloves with high latex allergen concentrations and in workers using powdered latex surgical gloves. Exposure to air-borne allergens and water-soluble IgE reactive latex antigens from natural rubber latex products in sensitized individuals can result in type I (immediate) hypersensitivity reactions. Clinical manifestations include contact urticaria, dermatitis, allergic rhinitis, conjunctivitis, asthma, angioedema, and anaphylaxis. Diagnostic tools include serological assays and skin prick testing. At present, latex avoidance is the only available treatment and is the key to preventing allergic reactions in latex-sensitized individuals. Health care worker sensitization to latex antigens in natural rubber products is becoming an increasing contributor to workers' liability and disability claims. Specific action can be taken to reduce occupational and patient exposure to latex antigens.

Anaphylaxis↗
PubMed2003

Studies of the thermal degradation of waste rubber.

One kind of Chinese waste tire's sample was pyrolyzed under an inert atmosphere by using thermo-gravimetric apparatus (TGA) and differential thermal analysis (DTA). Different pyrolysis temperature ranges were determined according to the reaction transition temperature obtained by TGA and DTA. Then, at each temperature range, the pyrolysis gaseous products were analyzed by gas chromatography (GC). The influence of the temperature range on the relative yields of the major decomposition products is studied, and a mechanism for the formation of the main components was also investigated. The results indicate that pyrolysis of waste rubber follows the radical mechanism, and the major products are not seriously affected by increasing the temperature from room temperature to 420 degrees C and from 421 to 600 degrees C, but the degradation of blend rubber is different for each of the compositional elastomer.

Environmental Pollution↗
PubMed1999

Biomonitoring of genotoxic risk in workers in a rubber factory: comparison of the Comet assay with cytogenetic methods and immunology.

Several substances used in rubber processing are known to be genotoxic. Workers in a rubber tyre factory, exposed to a broad spectrum of contaminants such as benzo[a]pyrene, benzo-fluoranthene, naphthalene, acetonaphthene, alkenes and 1,3-butadiene have been regularly examined for several years: chromosomal aberrations in lymphocytes, mutagenicity of urine (by use of the Ames test) and various parameters of blood and urine were assessed. An elevated level of mercapturic acid derivatives was found in the urine of employees, which is indicative of environmental exposure to toxicants with alkylating activity. We have now extended this study by examining genotoxicity with the modified Comet assay in parallel with chromosomal aberrations and micronucleus formation as well as immunological endpoints. Twenty-nine exposed workers from this factory were compared with 22 non-exposed administrative staff working in the same factory, as well as with 22 laboratory workers. The absolute numbers of peripheral leukocytes were significantly higher in the exposed group than in either of the control groups (p < 0.001). The erythrocyte mean cell volume was significantly higher in exposed workers in comparison with laboratory controls (p < 0.05). Percentages of lymphocytes, polymorphonuclear leukocytes, monocytes and eosinophils were not altered. The proliferative response of T- and B-cells to mitogen treatment when calculated per number of lymphocytes and adjusted for smoking, age and years of exposure did not differ between exposed and control groups. Endogenous strand breaks (including alkali-labile sites) and altered bases (formamidopyrimidine glycosylase- and endonuclease III-sensitive sites) were measured by the Comet assay in lymphocyte DNA. Exposed workers had significantly elevated levels of DNA breaks compared with office workers (p < 0.00001) or with laboratory controls (p < 0.00001). Micronuclei occurred at significantly higher frequencies in the exposed group than in controls (p < 0.00001), though the frequencies were all within the normal range. Significant correlations were seen between individual values of strand breaks, micronuclei and chromatid/chromosome breaks and certain immunological parameters.

Adult↗
PubMed2000

Great advantages in using a natural rubber instead of a synthetic SBR in a pro-oxidant system for degradable LDPE.

Different pro-oxidant systems are used in degradable low-density polyethylene (LDPE). The main question is the degradation products and not the degradation time from the used materials. The pro-oxidant formulation used consisted of manganese stearate and natural rubber (NR) or manganese stearate and a synthetic, styrene-butadiene copolymer rubber (SBR). The samples were heated in air at 100 degrees C in sealed glass vials. The molecular weight changes were measured by size exclusion chromatography (SEC). The volatile and nonvolatile degradation products have been identified by gas chromatography-mass spectrometry (GC/MS). A wide variety of degradation products were identified, including ketones, carboxylic acids, keto acids, dicarboxylic acids, and furanones as a homologous series. Benzaldehyde, acetophenone, benzoic acid, benzyl benzoate, and two benzene derivative compounds were identified only in the LDPE-SBR system. These aromatic compounds originate from the styrene part of SBR. The advantages using pro-oxidant containing NR are more effective degradation of LDPE without any aromatic degradation products.

Butadienes↗
PubMedDate not supplied

Crab shell chitin whisker reinforced natural rubber nanocomposites. 1. Processing and swelling behavior.

Nanocomposite materials were obtained from a colloidal suspension of chitin whiskers as the reinforcing phase and latex of both unvulcanized and prevulcanized natural rubber as the matrix. The chitin whiskers, prepared by acid hydrolysis of chitin from crab shell, consisted of slender parallelepiped rods with an aspect ratio close to 16. After the two aqueous suspensions were mixed and strirred, solid composite films were obtained either by freeze-drying and hot-pressing or by casting and evaporating the preparations. The processing and swelling behavior of composite films were evaluated. It was concluded that the whiskers form a rigid network assumed to be governed by a percolation mechanism in the evaporated samples only. Comparatively, better resistance of evaporated samples than hot-pressed ones against swelling in an organic solvent medium is good evidence for the existence of a rigid chitin network. The values of diffusion coefficient, bound rubber content, and relative weight loss also supported the presence of a three-dimensional chitin network within the evaporated samples. The mechanical behavior of the composites gives additional insight and evidence for this fact (part 2).

Animals↗
PubMedDate not supplied

Crab shell chitin whiskers reinforced natural rubber nanocomposites. 3. Effect of chemical modification of chitin whiskers.

The purpose of this study was to chemically modify the surface of chitin whiskers and to investigate the effect of the incorporation of these modified whiskers into a natural rubber (NR) matrix on the properties of the ensuing nanocomposite. Different chemical coupling agents were tested, namely, phenyl isocyanate (PI), alkenyl succinic anhydride (ASA) (Accosize 18 from American Cyanamid), and 3-isopropenyl-alpha,alpha'-dimethylbenzyl isocyanate (TMI). The extent of chemical modification was evaluated by Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and surface energy analysis. After chemical modification, nanocomposite films were obtained using a toluene natural rubber solution in which the whiskers were dispersed. Their mechanical properties were found to be inferior to those of unmodified chitin/NR composites presented in our previous study. In fact, even though there is an increase in filler-matrix interaction as a result of chemical modification of the chitin whiskers, this does not contribute to the improvement in the mechanical properties of the resulting nanocomposite. It is concluded that this loss of performance is due to the partial destruction of the three-dimensional network of chitin whiskers assumed to be present in the unmodified composites.

Animals↗
PubMed2000

Nasal provocation test in the diagnosis of natural rubber latex allergy.

BACKGROUND: Natural rubber latex (NRL) allergy in workers using rubber gloves has been an occupational health problem for the last 10 years. In the case of the occupational agents, clinical history may be far from conclusive; hence, appropriate provocation should be carried out. The objective was to evaluate the usefulness of the nasal challenge test in the diagnosis of allergic rhinitis in subjects occupationally exposed to NRL. METHODS: A single-blind, placebo-controlled study was conducted in 16 nurses with respiratory symptoms (bronchial asthma and/or rhinitis) related to NRL exposure as well as positive skin prick test (SPT) response to NRL. The controls were nine nurses with asthma and/or perennial rhinitis unrelated to NRL exposure; six atopic patients not occupationally exposed to NRL, with asthma and/or perennial rhinitis; and six healthy subjects. All the controls had negative results of SPT with NRL. Patients with a history of anaphylaxis or positive results of RAST to NRL were not considered in the study. The "nasal pool" technique was used to evaluate the cellular response and changes in protein level and ECP concentration in nasal washings after topical provocation with allergen or placebo. RESULTS: A significant increase was noted in eosinophil and basophil number, albumin/total protein ratio, and ECP level only in NRL SPT-positive patients subjected to nasal challenge with NRL. Neither bronchial nor systemic reactions were found after the nasal provocation with NRL. CONCLUSIONS: The nasal challenge test appears to be useful for diagnosing occupational rhinitis in NRL-sensitized patients.

Adult↗
PubMed1993

Carcinoma of the scrotum associated with rubber urinals. Case report.

A paraplegic patient, who had worn a rubber urinal in close contact with the scrotum for over 40 years, developed carcinoma of the scrotum. It is likely that this is a previously unsuspected example of chemical carcinogenesis, and in view of this, we believe that the use of rubber urinals should be discontinued.

Carcinoma, Squamous Cell↗
PubMed1993

Rubber dam usage related to restoration quality and survival.

The effects of rubber dam or cotton roll isolation on the initial quality and later survival of 644 amalgam and 149 anterior enamel-bonded composite resin restorations were evaluated over periods of up to 15 and 10 years, respectively. All restorations were placed by one operator and their quality assessed at the time of finishing, using seven clinical characteristics. The influence of six other clinical parameters on the survival of the restorations was also evaluated. There were no clinically-significant differences present in the initial high quality of the restorations, or in their later survivals, which could be directly related to the use or otherwise of rubber dam. Overall, the restoration survivals were excellent. However, there were significantly more amalgam restoration failures, from bulk fracture, in patients with severe bruxism.

Chi-Square Distribution↗
PubMed1998

The dental management of patients with natural rubber latex allergy.

Reports of allergic reactions to natural rubber latex have increased during the past two decades with both dental personnel and patients being affected. A dental management protocol is outlined for patients who have latex allergy. This includes: the identification of patients at high risk for developing latex allergy; the creation of a controlled, 'latex free' environment in the dental surgery; and the provision of emergency drugs and equipment that are free from natural rubber latex and may be required for the management of an allergic reaction.

Clinical Protocols↗
PubMed1999

Natural rubber latex allergy.

Rubber is an important industrial and consumer product encountered in many household items and medical devices. Whereas the chemical additives used in its manufacture are well recognized as a cause of delayed-type hypersensitivity (allergic contact dermatitis), it is only during the past decade that immediate-type allergy to natural rubber latex (NRL) proteins (latex allergy) has emerged as a serious health issue. Frequent, prolonged wearing of NRL gloves, especially amongst health care workers, is a major risk factor for such sensitization. Latex allergy is now an important medical, occupational, medico-legal and financial problem, and it is essential that policies are developed to reduce it. Undiagnosed latex allergy is potentially very serious for patients. This article briefly overviews latex allergy with emphasis on the practical issues of diagnosis and management.

Allergens↗
PubMed2004

Cross-reactivity between obeche wood (Triplochiton scleroxylon) and natural rubber latex.

BACKGROUND: Several studies have shown that allergy to natural rubber latex is associated with cross reactivity to other plants. We have investigated a possible cross reactivity with a tree belonging to the Sterculiaceae family, Tryplochiton scleroxylon, in a patient allergic to obeche wood, that began to suffer symptoms of allergy in contact with latex. METHODS: Determinations of specific IgE by CAP to obeche, natural rubber latex (NRL) and recombinant allergens of latex were done. Immunoblotting was performed to study allergens detected by serum of our patient. CAP-inhibition methods were used to study cross-reactive between NRL and obeche wood. RESULTS: In obeche extract, 4 bands were found of an apparent molecular weight of 18, 38, 75 and 199 kDa. In NRL extract the allergens have a molecular weight around 18, 21, 32, 38, 60, 70 and 199 kDa. IgE to latex was almost completely inhibited (96%) by the obeche extract in CAP-inhibition studies. Using obeche extract as inhibitor, IgE binding to native hevein (nHevb 6.02) was reduced by 25%. CONCLUSIONS: The results obtained in CAP-inhibition demonstrate the existence of cross-reactivity between proteins in NRL and obeche wood. In our patient, a band of apparent molecular weight of 38 kDa could be the most important allergen.

Adult↗
PubMed2000

Molecular cloning, expression, and functional analysis of a cis-prenyltransferase from Arabidopsis thaliana. Implications in rubber biosynthesis.

cis-Prenyltransferase catalyzes the sequential condensation of isopentenyl diphosphate with allylic diphosphate to synthesize polyprenyl diphosphates that play vital roles in cellular activity. Despite potential significance of cis-prenyltransferase in plant growth and development, no gene of the enzyme has been cloned from higher plants. Using sequence information of the conserved region of cis-prenyltransferase cloned recently from Escherichia coli, Micrococcus luteus, and yeast, we have isolated and characterized the first plant cis-prenyltransferase from Arabidopsis thaliana. Sequence analysis revealed that the protein is highly homologous in several conserved regions to cis-prenyltransferases from M. luteus, E. coli, and yeast. In vitro analyses using the recombinant protein overexpressed in E. coli revealed that the enzyme catalyzed the formation of polyprenyl diphosphates ranging in carbon number from 100 to 130 with a predominance of C(120). The enzyme exhibited a higher affinity for farnesyl diphosphate than for geranylgeranyl diphosphate, with the K(m) values being 0.13 and 3.62 micrometer, respectively, but a lower affinity for isopentenyl diphosphate, with a K(m) value of 23 micrometer. In vitro rubber biosynthesis analysis indicated that the Arabidopsis cis-prenyltransferase itself could not catalyze the formation of higher molecular weight polyprenyl diphosphates similar to natural rubber. A reverse transcriptase-polymerase chain reaction analysis showed that the gene was expressed at low levels in Arabidopsis plant, in which expression of the cis-prenyltransferase in leaf and root was higher than that in stem, flower, and silique. These results indicate the tissue-specific expression of cis-prenyltransferase and suggest a potential role and significance of the enzyme in the polyisoprenoid biosynthesis in plants.

Amino Acid Sequence↗
PubMed2003

Contamination of drinking water by coliforms from biofilms grown on rubber-coated valves.

In water samples from drinking water distribution systems, coliform bacteria (predominantly Citrobacter species) were repeatedly detected. Disinfection and flushing of the systems did not erase the problem. The pattern of the coliform occurrences indicated contamination originating from biofilms. After inspection of internal surfaces of the systems, no significant biofilm growth was observed on pipe surfaces, but in a number of cases, visible biofilms were detected on rubber-coated valves which harboured the same coliform species as those found in the drinking water samples. In these cases, the rubber-coated valves seemed to act as point sources for the contamination of water.

Biofilms↗
PubMedDate not supplied

Mortality among male rubber workers in Finland.

The deaths of male rubber workers in two processing departments and a tire and tube manufacturing department of a Finnish rubber plant were studied. The number of person-years at risk was 7,049. Follow-up continued for 24 yr, from January 1, 1953 to December 31, 1976. The total number of deaths was 29 compared with 43 expected (relative risk = 0.7). Only 5 deaths from cardiovascular diseases were found vs. 17.9 expected. The relative risk of death from cancer was 1.0 (7/6.8) and 1.7 (5/2.9) for workers who were exposed for more than 10 yr. For other causes of death the relative risk was not dependent on the length of exposure.

Adolescent↗
PubMed2003

Alkylphenol and bisphenol A levels in rubber products.

Levels of p-t-butylphenol (PTBP), p-t-octylphenol (PTOP), p-nonylphenol (NP) and bisphenol A (BPA) in rubber products in food-contact use, infant-related use and other uses are reported. Of 60 rubber products tested, PTOP was found in three in a concentration range of 2.2-37 microgram g(-1), and NP in 15 in a concentration range of 2.6-513 microgram g(-1). PTBP and BPA were not found in any sample. PTOP and NP were not detected in any infant-related sample, regardless of the material type. In contrast, among the samples with food contact and with other uses, the percentages containing PTOP or NP were 33 and 43%, respectively. A migration test was performed on eight samples containing NP and used in food-contact environments. The migration level of NP from spatulas to n-heptane was 0.83-1.52 microgram ml(-1). The average migration rates to water, 20% ethanol and n-heptane were 0.03, 0.7 and 6.6%, respectively.

Benzhydryl Compounds↗