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Effect of rubber flooring in front of the feed bunk on the time budgets of dairy cattle.

The objective of this experiment was to study the effect of rubber flooring in front of the feed bunk on the immediate behavioral response of dairy cattle. Four groups of 12 dairy cattle were alternately housed in sections of a free-stall barn with either 1.85 m of rubber flooring or grooved concrete in the area in front of the feed bunk. Rubber flooring did not affect time spent eating. However, animals showed a slight, but detectable, increase in time standing without eating on the rubber surface (5.5%) compared with concrete (4.8%). For reasons that are unclear, this increase in time spent standing was not limited to the area in front of the feed bunk; animals spent 11.0% of the available time standing elsewhere in the pen (outside of the free stall but not in front of the feed bunk) when they had access to the rubber flooring, compared with 9.0% when housed with access to only concrete floors. In addition, animals spent slightly less time lying in the free stall when they had access to rubber in front of the feed bunk (52.5 vs. 54.3%). Time spent engaged in behaviors such as standing elsewhere in the pen and eating were variable over time. For example, time spent eating declined from 23.1 to 17.4% over the 6-wk trial. In conclusion, dairy cattle with access to rubber flooring in front of the feeder showed small differences in where and how much time they spent standing, although the biological implications of these small changes are unclear.

Animal Feed↗

Degradation of natural rubber by Achromobacter sp. NRB and evaluation of culture conditions.

A natural rubber degrading candidate was isolated from a soil sample from Aswan, Egypt. The strain was able to grow on natural rubber as a sole source for carbon and energy. According to its degradation behavior, it grew adhesively and in direct contact with the rubber substrate and led to disintegration of the material during cultivation. Furthermore, this strain was not able to form a clear zone (translucent halos) around bacterial colonies after cultivation on NR latex plates. Taxonomic analysis of the strain based on partial 16S rRNA similarity examinations indicated that bacterial candidate belongs to genus Achromobacter sp. Schiff's reagent staining tests performed during cultivation of the strain on NR latex gloves of different sizes, treated or nontreated, revealed that the strain was able to colonize the rubber surface. Formation of bacterial films and occurrence of compounds containing aldehyde groups during cultivation was observed. The tested strain showed a higher colonization efficiency on small or treated pieces of NR latex gloves, while a lower colonization efficiency was recognized when grown on large or nontreated NR latex gloves. Plackett-Burman experimental design, based on numerical modeling, was applied to evaluate the significance of culture conditions affecting natural rubber degradation by the bacterial candidate. Eleven variables through fourteen trials were studied simultaneously. Based on rubber mineralization data, the highest positive variables affecting rubber degradation were NR granules, K2HPO4, Na-succinate and NH4Cl, while MgSO4 x 7H2O and KH2PO4 were the lowest significant variables.

Achromobacter↗

Carcinogens in the workroom air in the rubber industry.

Only a few data are available on the occurrence of carcinogenic compounds in the air at workplaces in the rubber industry, with the exception of data on total particulates and solvents. The available information allows the indication of some specific workplaces with elevated exposure levels. Recent investigations of nitrosamines in the rubber industry indicate the widespread occurrence of considerable levels of nitrosodimethylamine and nitrosomorpholine. In an effort to elucidate the origin and formation of nitrosamines in this industry, chemicals as well as the air in various areas were analyzed. All chemicals used for rubber compounding contain nitrosamines if they are derivatives of secondary amines, eg, tetramethylthiuram, zinc diethyldithiocarbamate or N-oxydiethylene benzothiazolylsulfenamide. Accordingly, variable concentrations of airborne nitrosamines could be detected at places where rubber products are manufactured or stored. The nitrosamines found correspond to the compounded chemicals. The original nitrosamine level in rubber chemicals is not high enough to explain the amounts found in rubber products and in air. Therefore additional nitrosation had to be considered. The responsible nitrosating agents are described. Preliminary results show that, in most cases, either by elimination of the nitrosating agent or by the exchange of rubber chemicals nitrosamine levels in the work area can be drastically reduced.

Air Pollutants, Occupational↗

[Controlled cell cultivation. V. The effect of various rubbers on the isolated neurons of Limnaea stagnalis in culture].

Various domestic rubbers were tested for toxicity to cultured isolated neurons of Lymnaea stagnalis, the survival time of these cells, and their morphological differentiation being used as criteria. According to the effect towards the neurons, the tested materials could be divided into inert, low-toxic, and toxic ones. Type 52336/4 silicon rubber, the rubber of surgical gloves, and dry rubber of "b" type produce no unfavourable effect on isolated neurons. Stoppers of penicillin bottles, baby's dummies, and silicon-based BgO-1 "Germetic" paste are low-toxic rubbers. By contrast, silicon rubbers of 52336 and 14p-6 types, KLT-30 silicon paste and black rubber of HO-68-1 type decreased sharply the survival time of the neurons and depressed their morphological differentiation in culture.

Animals↗

Crossreactivity between allergens in natural rubber latex and banana studied by immunoblot inhibition.

BACKGROUND: An association between allergic reactions to natural rubber latex and to banana has been reported but the immunochemical properties of the putative cross-reacting allergens remain unknown. OBJECTIVE: To study extracts of banana and natural rubber latex and sera from latex-allergic patients for possible crossreacting allergens and IgE antibodies. METHODS: Sera from 22 latex-allergic patients and 22 control subjects with no evidence of allergy to latex or to banana were studied. All patients had positive and controls negative reactions in skin-prick testing using an eluate of latex gloves. IgE antibodies to natural rubber latex and to banana were evaluated by immunoblotting and by radioallergosorbent test (RAST) and crossreactivity between allergens in banana and natural rubber latex by immunoblot inhibition. Skin-prick testing was used to examine in vivo reactivity to banana. RESULTS: Ten of the 22 (45%) latex-allergic patients sera recognized altogether 14 allergens in banana by immunoblotting. The most frequently identified banana allergens were 23, 32, 36, 39 and 47 kDa proteins. The banana skin-prick test was positive in 14 of 18 (78%) latex-allergic patients studied and banana RAST in 12 of 14 patient sera tested. Fourteen of 21 interviewed patients reported symptoms from eating or handling bananas. In immunoblot inhibition studies a dose-dependent inhibition of IgE binding to banana extract with natural rubber latex proteins was observed in all five patient sera tested and, likewise, the binding of IgE to natural rubber latex extract was inhibited with banana proteins in four of the five patient sera. CONCLUSIONS: The present results confirm the existence of crossreacting allergens in natural rubber latex and banana and provide new information on the immunochemical nature and heterogeneity of these allergens.

Adult↗

Adhesion to silicone rubber of yeasts and bacteria isolated from voice prostheses: influence of salivary conditioning films.

Adhesion of yeasts and bacteria to silicone rubber is one of the first steps in the biodeterioration of silicone rubber voice prostheses. In this paper, adhesion of two streptococcal, staphylococcal, Candida albicans and Candida tropicalis strains, isolated from explanted voice prostheses was investigated to silicone rubber with and without a salivary conditioning film in a parallel-plate flow chamber. Within each microbial pair of one species, the strain with the most negative zeta potential adhered most slowly to negatively charged silicone rubber. No other clear relationships were obvious between adhesion to silicone rubber and microbial zeta potentials of cell-surface hydrophobicities, as by water contact angles. A 1.5-h adsorbed salivary conditioning film appeared to possess components, presumably albumin and lysozyme, slowing down the deposition of the yeasts and some of the streptococcal and staphylococcal isolates. In addition, microbial adhesion in a stationary end point was generally lower to silicone rubber with an adsorbed salivary conditioning film than without one. Nearly all microorganisms adhering to an adsorbed salivary conditioning film, yeasts as well as bacteria, were stimulated to detach by the passage of an air bubble through the chamber, but microorganisms adhering directly to the silicone rubber, especially C tropicalis strains, detached in far lower numbers under the influence of a passing air bubble. The present observations are in agreement with clinical in vivo findings that in patients with reduced saliva production after radiotherapy, the device life of the voice prosthesis is significantly shortened and suggests that isolated salivary components might be used as an anti-adhesive.

Bacteria↗

Comparison of rubber band ligation and haemorrhoidectomy for second- and third-degree haemorrhoids: a prospective clinical trial.

One hundred patients with second- or third-degree haemorrhoids were randomly allocated to haemorrhoidectomy (50) or rubber band ligation (50). Forty-two in each group presented with rectal bleeding; haemorrhoidectomy relieved 36 and rubber band ligation relieved 31 of this symptom. All patients had prolapsing haemorrhoids at presentation. One year after treatment 45 haemorrhoidectomy and 43 rubber band ligation patients were assessed. Haemorrhoidectomy relieved 44 of 45 patients and rubber band ligation relieved 34 of 43 (P < 0.05). Haemorrhoidectomy caused pain in all cases, lasting for more than 48 h in 35. Rubber band ligation was painless in 5 and produced pain for more than 48 h in 15. Mean time off work was 32 days for haemorrhoidectomy and 3 days for rubber band ligation (P < 0.001). Rubber band ligation as an outpatient procedure is an effective treatment for second- and third-degree haemorrhoids and should be considered before recourse to surgery.

Adult↗

Cloning and Sequencing of the cDNA Encoding the Rubber Elongation Factor of Hevea brasiliensis.

In Hevea brasiliensis, the rubber particle in the laticiferous vessel is the site of rubber (cis-1-4-polyisoprene) biosynthesis. A 14 kilodalton protein, rubber elongation factor (REF), is associated with the rubber particle in a ratio of one REF to one rubber molecule (Dennis M, Henzel W, Bell J, Kohr W, Light D [1989] J Biol Chem 264: 18618-18628; Dennis M, Light D [1989] J Biol Chem 264: 18608-18617). To obtain more information concerning the function of REF and its synthesis and assembly in the rubber particle, we isolated cDNA clones encoding REF. We used antibodies to REF to screen a Hevea leaf gammagt11 cDNA expression library and obtained several positive clones. Sequence analysis of the REF cDNA clones showed that the REF mRNA contains 121 nucleotides of 5'-nontranslated sequences and a 205 nucleotide 3'-nontranslated region. The open reading frame encodes the entire 14 kilodalton REF protein without any extra amino acids (Dennis M, Henzel W, Bell J, Kohr W, Light D [1989] J Biol Chem 264: 18618-18628). The REF cDNA was subcloned in pGEM-3Z/-4Z and expressed in vitro. The translation product is a 14 kilodalton protein that can be immunoprecipitated with antibodies to REF. Addition of microsomal membranes to the in vitro translation product did not alter the mobility of the REF protein. This, and the sequence data, indicate that REF is not made as a preprotein. Our results suggest that REF is synthesized on free polysomes in the laticifer cytoplasm and that assembly of the rubber particles is likely to occur in the cytosol.

Journal Article↗

Comparison of infrared coagulation and rubber band ligation for first and second degree haemorrhoids: a randomised prospective clinical trial.

One hundred and thirty seven previously untreated out-patients with first and second degree haemorrhoids were allocated at random to treatment by infrared coagulation (n=66) or rubber band ligation (n=71). Complete follow up was obtained in 122 patients (60 who had undergone infrared coagulation (group 1), and 62 rubber band ligation (group 2)) at periods from three months to one year after completion of treatment. Infrared coagulation produced a satisfactory outcome in 51 patients (85%): 34 were rendered asymptomatic and 17 improved. Rubber band ligation produced a satisfactory outcome in 57 patients (92%): 33 were rendered asymptomatic and 24 improved. Both methods were equally effective in first and second degree haemorrhoids. The incidence of side effects, particularly discomfort, during and after treatment was significantly higher in those treated by rubber band ligation (p less than 0.001). This appeared to be an appreciable deterrent to future patient compliance. The number of patients losing more than 24 hours from work was higher after rubber band ligation than after infrared coagulation. The number of treatments necessary to cure symptoms did not differ significantly between the two methods. Infrared coagulation was significantly faster than rubber band ligation (p less than 0.001). Infrared coagulation is a simple, fast, and effective outpatient method for the treatment of first and second degree haemorrhoids with fewer troublesome side effects and higher patient acceptability than rubber band ligation.

Adult↗

The transport of octamethylcyclotetrasiloxane (D4) and polydimethylsiloxane (PDMS) in lightly cross-linked silicone rubber.

The transport of octamethylcyclotetrasiloxane (D4), one of the major constituents of silicone fluids and rubbers, and low viscosity polydimethylsiloxane oil into a silica filled cross-linked silicone elastomeric rubber was measured as a function of temperature, cross-link density of the rubber, and concentration of the D4 in methanol solution. A small amount of material, approximately 3 wt%, is extracted from the rubber with hexane. The extraction process has a large effect upon D4 solubility in the rubber, increasing from approximately 160 to 180 wt% after extraction. The heats of solution for both penetrants into the rubber are essentially zero and the activation energies for diffusion are small, approximately 8 and 15 kJ molt(-1) for D4 and PDMS, respectively. The diffusion process is Fickian and the diffusion coefficient of D4 into silicone/silica rubbers is essentially independent of concentration over the concentration investigated, i.e. from 1 to 100 vol% D4 in methanol. The permeability, i.e. the product of the diffusion coefficient and the solubility, decreases rapidly for D4 concentrations less than 50 vol% (0.1 mol fraction). This suggests that the permeation of D4 out of any encapsulation device, such as a silicone breast implant, is linearly dependent upon the concentration of D4 in the prosthesis. Swelling is isotropic and was measured by dimensional changes in rectangular samples and correlates well with the volume of D4 sorbed.

Adsorption↗

[Changes of ciscoelastic behaviour during curing of polyether rubber impression material].

To obtain a precise impression, it is indispensable to understand changes of physical property of the material used, during curing. The authors measured the viscosity and the storage modulus of polyether rubber which was recently introduced as a commercial impression material and tried to make clear the curing mechanism of the material. The less the amount of catalyst added to the base material, the more approximative is the behaviour to the first-order reaction. But according as the amount of catalyst increases the behaviour becomes not to be regarded as the first-order reaction, i.e., it is surmised that the curing reaction becomes so complicated. The more the amount of catalyst and the higher the temperature after mixing, the shorter is the setting time. The curing reaction of polyether rubber impression material is supposed to be completed in about 3 hours after mixing. Polyether rubber impression material showed the highest storage modulus among the three rubber impression materials not used, namely, polyether, polysulfide and silicone rubber. The values of this highest modulus of polyether rubber were about 2.4approximately2.8 times of those of polysulfide and silicone rubber impression material in 3 hours after mixing.

Dental Impression Materials↗

Frequency and relevance of positive patch tests to cyclohexylthiophthalimide, a new rubber allergen.

Cyclohexylthiophtalimide (CTP) is currently the most widely used vulcanization retarder in the rubber industry. Little is known about sensitization to CTP, although positive tests to it do occur in patients exposed to rubber objects. A retrospective study of 350 patients who were patch tested with the standard rubber chemical series was conducted in two departments of dermatology, one in Nancy, France, and one in Leuven, Belgium. Sixteen (4.6%) out of the 350 patients had clear and 6 (1.7%) had doubtful positive reactions to CTP. Cross-sensitivity with other molecules could not be determined. The source of sensitization in most cases seems to have been protective rubber gloves at work. In the other cases, sensitization was suspected to have been caused by rubber shoes, elastic bands in underwear, or other rubber objects. The determination of the relevance of positive tests remains difficult, especially since little is known about the components of rubber products.

Adult↗

Hydrological eco-service of rubber plantations in Hainan Island and its effect on local economic development.

The impacts of economic forest on global environmental change (GEC) are one of the hot issues in environmental study. Based on the 3-year observation data and 40-year climate data, GEC and analysis of the hydrological dynamic characteristics of rubber plantations and estimate of the water balance in the rubber plantations in Hainan Island were made. The results showed that the rainfall intercepted by the canopy of the plantations accounted for 11.45% of the annual rainfall, the total runoff for 23.71%, the total evaporation and transpiration for 63.24%, the soil moisture storage for 1.6%. Analysis of the 40-year rainfall data in the 19 counties of Hainan Island during 1951-1990 showed that the large-scale substitution of the natural vegetation with the rubber plantations had no significant effect on the local rainfall in Hainan Island. The main reasons are (1) 80% of the rainfall in Hainan is brought by typhoons; (2) the proportion of 11.6% rubber plantations in total forest coverage in Hainan is not enough to influence the local rainfall in Hainan Island; and (3) although the rubber plantation is artificial vegetation, it has the similar function to the tropical rain forest. Analysis of the total water resource and total GDP of Hainan in 1997 showed that the economic benefit resulted from the water resource was 1.0 RMB Yuan/m3. The value of hydrological of the rubber plantation in Hainan was 113.9 million RMB Yuan/3 when compared with the tropical rain forest. The paper reaches conclusion that the hydrological eco-service function of rubber plantation has been enhanced after transformed from natural vegetation, which includes the natural service and powerful social service.

China↗

The protein content of dental rubber dams.

OBJECTIVES: The purpose of this study was to analyse the protein content of 17 commonly used rubber dams and to determine if they contained known allergenic proteins. METHODS: Proteins were eluted with buffer from 17 brands of commercially available rubber dams. The quantity of eluted protein was measured and expressed in micrograms in every gram of rubber. The molecular weights of the individual proteins eluted were then measured after resolution on sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and compared with those of known allergens. RESULTS: The rubber dams were shown to contain significant amounts of protein (950-5850 micrograms). The subsequent analysis of these proteins using SDS-PAGE confirmed that some of these proteins were of the same molecular weight as known allergens. CONCLUSIONS: The results of this study confirm that all the rubber dams tested contained significant amounts of protein. The molecular weights of these proteins correspond with those of known allergens, and they could, therefore, be a cause of hypersensitivity reactions to dental rubber dams.

Allergens↗

Nutritional evaluation of selected Nigerian rubber seed products--a chemical approach.

Four Nigerian rubber seed products (whole and shelled rubber seed flours and oils) were subjected to various chemical analyses to provide a basis for their nutritional evaluation. The shelled rubber seed oil was stored for 4 weeks under different temperatures, light and dark conditions and at water activities of 0.33 and 0.95, to assess changes in some of its indices of nutritional quality. From the results of these studies, it would appear that the rubber seed product can meet, to varying degrees, the recommended daily requirements for various nutrients such as protein, fat and mineral elements. The shelled rubber seed oil also promises to be a valuable edible oil with a very low saturated/unsaturated fatty acid ratio and which is rich in the essential fatty acid, linoleic acid. Generally, dark storage, non-extreme temperature, and a water activity of 0.33 proved to be relatively effective in maintaining the nutritive aspects of the shelled rubber seed oil.

Dietary Fats↗

Adsorption of mercury by carbonaceous adsorbents prepared from rubber of tyre wastes.

Rubber from tyre wastes has been used to prepare carbonaceous adsorbents and the products obtained have been tested as adsorbents for mercury in aqueous solution. The adsorbents have been prepared by applying thermal, chemical and combined (thermal and chemical or vice versa) treatments. Tyre rubber has been: heated at 400 or 900 degrees C for 2 h in N2, chemically-treated with H2SO4, HNO3 or H2SO4/HNO3 solution for 24 h, and in two successive steps first heated at 400 degrees C for 2h in N2 and then treated with a H2SO4/HNO3 solution for 24 h, or vice versa. Resultant products have been characterised in terms of elementary composition and textural properties. The adsorption of mercury has been studied from kinetic and equilibrium standpoints. The treatments effected to tyre rubber decrease the carbon content and the hydrogen content. The oxygen content and the nitrogen content increase for the chemically-treated products. The heat treatment of tyre rubber results in a larger development of surface area, microporosity, and mesoporosity than the chemical treatments. These treatments, however, produce a great creation of macropores. In comparison to the starting rubber, the adsorption process of mercury is faster when the material is heated or treated with the H2SO4, HNO3 or 1:3 H2SO4/HNO3 solution. These adsorbents are either a non-porous solid or possess a high mesopore volume or a wide pore size distribution in the macropore range. The adsorption capacity is larger for products prepared by heat, chemical and combined treatments of the rubber. A common textural characteristic of these adsorbents is their better developed microporosity. The ability to adsorb mercury is higher for the heated products than for the chemically-treated ones. The maximum adsorption of mercury is 211 mg g(-1). The constant Kf of the Freundlich equation is as high as 108.9 mg g(-1).

Adsorption↗

Absence of cross-reactivity of IgE antibodies from subjects allergic to Hevea brasiliensis latex with a new source of natural rubber latex from guayule (Parthenium argentatum).

BACKGROUND: Natural rubber latex sensitization is caused by proteins from the latex of Hevea brasiliensis, the Brazilian rubber tree. Alternative non-cross-reactive latex rubber sources are needed for the manufacture of nonallergenic medical devices (e.g., catheters) that require elasticity, which is not currently provided by synthetic materials. METHODS: We have studied the ability of IgE antibodies from subjects allergic to Hevea latex and IgG antibodies from hyperimmunized mice to detect proteins derived from guayule (Parthenium argentatum), an alternative rubber source, using a direct binding and competitive inhibition RAST and Western blot analysis. RESULTS: IgE antibodies from 62 subjects allergic to Hevea latex (46 adults and 16 children with spina bifida) and from serum pools of adults allergic to Hevea latex (n = 183), pediatric patients (n = 101), and patients with spina bifida (n = 53), as well as IgG antibodies from hyperimmunized mice, were unable to detect any proteins in guayule by RAST or Western blot analysis. No competitive inhibition of IgE anti-Hevea binding to Hevea solid phase was detected by the preincubation of sera from subjects allergic to Hevea latex with soluble guayule latex before RAST analysis. CONCLUSIONS: These results demonstrate that proteins in guayule latex are not cross-reactive with Hevea latex allergens. Devices that require the elasticity provided by rubber may be manufactured with guayule latex as an alternative rubber source for patients with Hevea latex allergy.

Adult↗

Bacterial degradation of natural rubber: a privilege of actinomycetes?

Using natural rubber latex as the sole source of carbon and energy 50 rubber-degrading bacteria were isolated. Out of those 50 isolates, 33 were identified as Streptomyces species and 8 as Micromonospora species. Screening of 1220 bacteria obtained from different culture collections revealed 46 additional rubber-degrading bacteria (Streptomyces 31 strains, Micromonospora 5, Actinoplanes 3, Nocardia 2, Dactylosporangium 1, Actinomadura 1, unidentified 3). All rubber-degrading isolates were identified as members of the actinomycetes, a large group of mycelium-forming Gram-positive bacteria. Interestingly no Gram-negative bacterium could be isolated. In most strains expression of extracellular rubber-degrading enzymes was repressed by glucose and/or succinate. The reduction of the average molecular mass of solution-cast films of natural rubber from 640000 to 25000 in liquid culture upon bacterial growth indicates the participation of an endo-cleavage mechanism of degradation.

Actinomycetales↗