PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Polyethylenes”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 19 recordsLinked to original sources
PubMed1992

Tissue response to intraperitoneal implants of polyethylene oxide-modified polyethylene terephthalate.

Polyethylene terephthalate films surface modified with polyethylene oxide of mol wt 18,500 g/mol (18.5 k) by a previously described technique, were implanted in the peritoneal cavity of mice, along with their respective untreated controls, for periods of 1-28 d. The implants were retrieved and examined for tissue reactivity and cellular adherence. The control polyethylene terephthalate surfaces showed an initial inflammatory reaction followed by an extensive fibrotic response with a mean thickness of 60 microns at 28 d. By contrast, polyethylene oxide-modified polyethylene terephthalate showed only a mild inflammatory response and no fibrotic encapsulation throughout the implantation period: at 28 d a cellular monolayer was observed. Apparently either the polyethylene oxide-modified surface was stimulating less inflammation, which was in turn stimulating less fibroblastic overgrowth, or the cellular adhesion to the polyethylene oxide-modified surface was too weak to support cellular multilayers.

Animals↗
PubMedDate not supplied

[Differences in polyethylene wear in hip joint prostheses with ceramic- and with metal-polyethylene combination of the articulation surfaces--a study of surgical and of autopsy materials].

Pseudocapsules of artificial hip joints with ceramic- and metal on polyethylene combination of the articulating surfaces from 126 revision arthroplasties and 41 autopsies were studied histologically with semiquantitative evaluation of the polyethylene wear. The results were compared with reports of laboratory tests in the literature. We found in the autopsy specimens as well as in the biopsies from revision arthroplasties of prostheses implanted for 4 to 8 years three times less polyethylene wear particles released from the ceramic on polyethylene prostheses. The newly established synovium surrounding prostheses with ceramic heads appeared 20% reduced in thickness with minor villous transformation. Different types of metal on polyethylene prostheses revealed no differences in wear behaviour with the exception of the bipolar prostheses which showed a markedly increased polyethylene wear.

Adult↗
PubMed1991

Biological responses to polyethylene oxide modified polyethylene terephthalate surfaces.

Polyethylene oxide (PEO) of molecular weights 5,000, 10,000, 18,500, and 100,000 g/mol was covalently grafted to surfaces of otherwise cell adhesive polyethylene terephthalate (PET) films. Analysis of these surfaces by measurement of contact angles and ESCA verified the presence of the grafted PEO. Protein adsorption assays of radiolabeled albumin and fibrinogen showed a marked reduction in adsorbed protein for the 18,500 and 100,000 molecular weight PEO coupled surfaces. Cell growth assays using human foreskin fibroblasts in culture showed that the higher-molecular-weight PEO surfaces supported cell growth to a much lower extent than the two lower-molecular-weight PEOs. Flow of whole blood over these surfaces and visualization of platelet adherence using epifluorescence video-microscopy showed very low platelet adherence only on the two higher-molecular-weight PEO coupled surfaces. Scanning electron microscopy corroborated these results. It was concluded that PEO of molecular weights neighboring 18,500 and higher was effective in reducing protein adsorption and cellular interactions on these surfaces.

Adsorption↗
PubMed2026

Diet-dependent effects of an environmentally relevant dose of polyethylene and polyethylene terephthalate on white adipose tissue and systemic insulin resistance in mice.

As human exposure to micro- and nanoplastics (NPs) is unavoidable, it remains unclear whether dietary composition can modulate their health impacts. To address this, we investigated the metabolic effects of two common yet understudied polymers, polyethylene (PE) and polyethylene terephthalate (PET), in mice with either healthy or energy-dense diet. C57BL/6 J male mice were exposed to an environmentally relevant dose of PE or PET (100 nm, 25 mg/kg BW/day) for 29 weeks under either a normal diet (ND) or a high-fat diet (HFD). The metabolic consequence of NP exposure was highly diet-dependent. In ND-fed mice, PE and PET reduced white adipose tissue (WAT) mass, with PET inducing metabolic changes that toward a lipodystrophy-like state. Conversely, in HFD-fed mice, both polymers impaired systemic insulin sensitivity. Regardless of diet, PE and PET promoted immunoglobin G (IgG) accumulation in epididymal WAT, with PE-exposed lean mice exhibited the most robust IgG elevation, WAT fibrosis and impaired adipogenesis. These findings demonstrate that chronic, environmentally relevant PE or PET exposure disrupts metabolic health in male mice under both dietary contexts. While dietary composition dictates the specific metabolic phenotype, it does not prevent adverse outcomes. This complicates lifestyle-based mitigation strategies and underscores the urgent need for environmental source controls.

Insulin Sensitivity↗
PubMed1991

In vitro studies of water activity and bacterial growth inhibition of sucrose-polyethylene glycol 400-hydrogen peroxide and xylose-polyethylene glycol 400-hydrogen peroxide pastes used to treat infected wounds.

Water activity and bacterial growth inhibition have been studied in formulations comprising either sucrose or xylose along with polyethylene glycol 400 and hydrogen peroxide. The pastes are chemically stable for 6 months if stored at 2 to 8 degrees C and have been shown to lower water activity to levels below those essential for bacterial growth and to be bactericidal even when diluted up to 50% with serum. Of the organisms tested, Staphylococcus aureus proved the least susceptible to the bactericidal effects of these pastes, and candida and gram-negative organisms proved the most susceptible. Pastes without hydrogen peroxide were less rapidly bactericidal than pastes with hydrogen peroxide, while polyethylene glycol 400 itself was found to have considerable antimicrobial activity. It is suggested that sucrose paste may be of benefit as a treatment for infected and malodorous wounds.

Animals↗
PubMed1992

Comparison of alumina-polyethylene and metal-polyethylene in clinical trials.

The dimensional changes of hip sockets of Müller-type total endoprostheses is the subject of this article. Regular anteroposterior roentgenographs of the pelvis were taken to determine the orientation of the center of the prosthetic head in relation to the wire marker of the polyethylene cup. Three different materials used for the femoral balls and matched with polyethylene as socket material were investigated, and the results of the displacement of the ball into the socket were compared. Both creep and wear contribute to the dimensional changes of the hip sockets; the proportional amount of each mechanism is not known. Data from laboratory examinations suggest a relatively high rate of creep in the first six months after implantation. With longer periods, the dimensional changes are predominately caused by wear. In the beginning of joint function, measurements show a high rate of the yearly dimensional changes. The head shifts up to 0.5 mm per year and diminishes after five years to rates of 0.1-0.2 mm, respectively. All dimensional changes that exceed a shift of the head of 0.2 mm per year are considered to be unfavorable and to contribute to loosening of the implants. Using metallic balls (Protasul-2), 64% had a wear rate of less than 0.2 mm; of those using Prostasul-10, 77% had lower rates than 0.2 mm. In patients where ceramic balls were implanted, the displacement rate was below 0.2 mm per year in 95%. Therefore, ceramic seems to be the most favorable material.

Aluminum Oxide↗
PubMed1976

Polyethylene glycol-induced mammalian cell hybridization: effect of polyethylene glycol molecular weight and concentration.

The effects of polyethylene glycol (PEG) molecular weight and concentration on mammalian cell hybridization were studied. The peak hybridization-inducing activity with all grades of PEG from 400-6000 was found to occur in the concentration range of 50-55%. However, changes in concentration were seen to have different quantitative effects with different grades of PEG. For monolayer fusions, PEG 1000 at 50% seems to be the optimal combination of PEG molecular weight and concentration, in terms of both efficiency of hybridization and relative insensitivity to dilution effects.

Cell Fusion↗
PubMed1978

Blood plasma/implant interfaces FT--IR studies of adsorption on polyethylene and heparin-treated polyethylene surfaces.

Described is an attenuated total reflection (ATR), Fourier Transform infrared (FT--IR) technique useful for studying the adsorption of blood plasma proteins onto polymer surfaces. This technique had the advantage of employing whole blood plasma and has detected differences between the species adsorbed onto heparin-treated polymers as compared to the species adsorbed on untreated polymers. Differences detected consist of 1) changes in conformation and/or composition of proteins adsorbed on treated and untreated polymers, and 2) changes in amounts of carbohydrate-containing materials on the treated and untreated polymer surfaces. The advantages of FT-IR are its extreme sensitivity and its ability to work with highly complex systems such as whole blood plasma. These abilities should be of great value for providing direct molecular level information concerning protein adsorption from intact blood systems.

Adsorption↗
PubMed1990

Polyethylene glycol 400 penetration of the colonic epithelial barrier of the rat.

Permeability changes of polyethylene glycol 400 have been seen in patients with inflammatory bowel diseases. Because the colon can be involved in inflammatory bowel disease, the mechanisms, kinetics, and influence of intraluminal factors on polyethylene glycol 400 permeation of perfused colonic segments of rats were studied. The absorption rate of polyethylene glycol 400 was linearly related to its luminal concentration (r = 0.94), suggesting that passive diffusion is a significant mechanism involved in polyethylene glycol 400 absorption. Changing the perfusate pH from 6.0 to 7.5 did not affect water absorption or polyethylene glycol 400 permeation. Increasing luminal osmolarity significantly decreased water and polyethylene glycol 400 absorption (P less than 0.01). The relationship between polyethylene glycol 400 and water absorption at different luminal osmolarities was linear (r = 0.97). At luminal osmolarity of 0.3 osm/L, 14.3% of polyethylene glycol 400 absorption was mediated by passive diffusion and 85.7% was mediated by convection. The solvent drag reflection coefficient for polyethylene glycol 400 in the colon was 0.03. Taurocholic acid (10 mmol/L) and chenodeoxycholic acid (5 mmol/L) decreased polyethylene glycol 400 and water absorption (P less than 0.01). Addition of 1 micrograms/mL of 16,16-dimethyl prostaglandin E2, 2 mmol/L of dibutyryladenosine-3',5'-cyclic monophosphate, or 10 mmol/L of aminophylline significantly decreased water and polyethylene glycol 400 absorption (P less than 0.01). These studies demonstrate that polyethylene glycol 400 permeation of the colon is mediated by both passive diffusion and solvent drag. Convective absorption is the major mechanism of polyethylene glycol 400 permeation of the colon. Polyethylene glycol 400 permeation is modified by bile acids, prostaglandins, and cyclic nucleotides through changes in water flux.

16,16-Dimethylprostaglandin E2↗
PubMed1991

The arthroscopic evaluation and characteristics of severe polyethylene wear in total knee arthroplasty.

Four hundred eighty-seven porous-coated anatomic (PCA) total arthroplasties were performed by the same surgeon between January 1982 and December 1989. Forty-three patients developed an effusion, pain, or decreased range of motion after a period of pain-free function. Average time to onset of symptoms was 4.5 years. Joint fluid aspirations were sterile and revealed the presence of high-density polyethylene crystals, best seen under a polarizing microscope. Thirty-three of these patients were arthroscopically evaluated. Extensive polyethylene wear and delamination were identified. Wear was most extensive on the medial tibial plateau. Patellar polyethylene wear was also identified. Substantial femoral component abrasions were present in areas where exposure of the tibial and patellar base plates had occurred. Diffuse granulomatous synovial tissue revealed an extensive foreign-body giant-cell reaction to polyethylene particles. In all patients, temporary symptomatic relief was obtained after arthroscopy. Thirty-two patients have, subsequently, had revision surgery. Intraoperative findings and biopsies at the time of revision confirmed the arthroscopic observations. Arthroscopy allowed the accurate diagnosis of polyethylene wear, provided temporary symptomatic relief, and facilitated preoperative revision planning. Polyethylene wear in PCA total knee replacements was related to patient characteristics (larger, younger, more active patients), nonconforming femotibial articular surfaces, thin polyethylene, heat-pressed polyethylene, and nonrigid mechanical attachment of polyethylene to metal base plate. Younger, more active, larger patients with total knee arthroplasties should be observed closely for evidence of polyethylene wear.

Aged↗
PubMed1991

Catastrophic wear of tibial polyethylene inserts.

A number of factors play an important role in the wear-resistance of tibial polyethylene inserts. Among these are manufacturing processes that adversely affect the wear-resistance of polyethylene (such as heat treatments to the articular surface or gamma irradiation used for sterilization), tibio-femoral articular geometry, polyethylene thickness, knee alignment, femoral-component-bearing surface material, modularity of the tibial inserts and tibial trays, and quality of the polyethylene itself. The authors report an unusually high rate of failure by wear of tibial polyethylene inserts from a series of 176 Porous Coated Anatomic (PCA) knees in which there were eight revisions (4.5% of the series) performed for tibial polyethylene wear at an average of 60 months. Nine additional knees (5.1%) had thinning of greater than 30% of the initial polyethylene thickness. Four of the unsuccessful knees revealed areas of osteolysis filled with membranes containing large amounts of particulate polyethylene. In addition to the 176 knees from a series from a Los Angeles university, the cases of five other knees in four patients who came for treatment from outside hospitals with full-thickness wear of the tibial polyethylene are discussed. One of these five knees was a cementless PCA knee that developed massive osteolysis in response to the particulate polyethylene debris.

Chromium Alloys↗
PubMed2026

Polyethylene transformation by a psychrotolerant Rhodococcus strain assessed by transcriptomics and 13C-isotope tracing.

Polyethylene is increasingly accumulating in nature, including remote places like the Arctic. While abiotic processes fragment polyethylene in situ, biotic transformation by microorganisms is assumed to occur. However, the enzymes and pathways involved remain poorly characterized. In this study, we used an in-house biobank from cold environments to screen for potential bacteria capable of degrading polyethylene by screening the strains in silico using the database PlasticDB and in vivo using a fluorescence-based assay. Using transcriptomic and proteomic analyses to identify genes in promising candidate strains that encode extracellular enzymes potentially capable of degrading PE, we selected a Rhodococcus erythropolis strain and two of its enzymes: a hypothetical protein (Hypr1) and a lipase family protein (Lip2). Expressing the candidate genes heterologously in Escherichia coli resulted in positive results in the fluorescence-based assay for polyethylene transformation. Applying 13C-labelled polyethylene for assessing and estimating polyethylene transformation and carbon assimilation, we found that R. erythropolis and both untransformed and recombinant E. coli extracellularly transformed the initially added polyethylene after 70 days. In addition, untransformed E. coli and R. erythropolis converted small, but significant amounts of polyethylene-derived carbon to carbon dioxide. The 13C-label was also traced into the bacterial biomass of R. erythropolis. Overall, our results provide evidence for biotic transformation of untreated polyethylene and suggests a hypothetical protein and a lipase family protein as two novel enzyme candidates associated with PE transformation.

Rhodococcus↗
PubMed1992

Polyethylene glycol superoxide dismutase and catalase attenuate increased blood-brain barrier permeability after ischemia in piglets.

BACKGROUND AND PURPOSE: Transport of urea across the blood-brain barrier is increased during postischemic cerebral reperfusion in the piglet. Ischemia/reperfusion also has been observed to increase apparent superoxide anion generation on the surface of the brain. The present study was designed to address the hypothesis that the increased transfer of urea into the brain after ischemia/reperfusion could be due to superoxide anion-induced alterations in blood-brain barrier permeability. METHODS: Blood-to-brain transfer of carbon-14-labeled urea was measured in four groups (n = 7 each) of newborn pigs: 1) control (no ischemia, no pretreatment), 2) pretreatment with polyethylene glycol superoxide dismutase (1,000 IU/kg) and polyethylene glycol catalase (10,000 IU/kg i.v.) but no ischemia, 3) no pretreatment and 20 minutes of ischemia followed by 2 hours of reperfusion, and 4) pretreatment with polyethylene glycol superoxide dismutase and polyethylene glycol catalase in addition to ischemia/reperfusion. The following brain regions were investigated: cerebrum, caudate, midbrain, pons, medulla, and cerebellum. RESULTS: Polyethylene glycol superoxide dismutase inhibited generation of superoxide anion by the brain during reperfusion after ischemia. Regional transfer of [14C]urea from blood to brain increased at 2 hours' reperfusion. This ischemia-induced increase in blood-to-brain transfer of [14C]urea was attenuated by pretreatment with polyethylene glycol superoxide dismutase and polyethylene glycol catalase: e.g., cerebrum Kin was 28 +/- 2 in the control group, 26 +/- 3 in the pretreated/no ischemia group, 67 +/- 5 in the untreated/ischemia group, and 40 +/- 2 ml.g-1.s-1.10(6) in the pretreated/ischemia group. After ischemia/reperfusion, cerebral blood flow was unchanged by pretreatment with polyethylene glycol superoxide dismutase and polyethylene glycol catalase. CONCLUSIONS: These data suggest that production of a partially reduced species of oxygen contributes to the increased urea transfer across the blood-brain barrier after ischemia in the newborn pig.

Animals↗
PubMed1990

The biomechanical problems of polyethylene as a bearing surface.

The metal backings of acetabular components can reduce the available polyethylene thickness, often to an alarming extent. This study indicated that the pitting and cracking of thin polyethylene surfaces have some similarities to tibial and patellar bearings and that creep-related deformation occurred more frequently in thin polyethylene components. Additionally, it appears that dimensional tolerances of the polyethylene inserts are difficult to maintain and may result in a nonuniform fit of both the femoral head into the component and the component into its own metal backing, which can lead to component separation. It is difficult to accurately measure the changes in material and mechanical properties of polyethylene over time. An additional ramification is that flaws, such as voids in the polyethylene, cannot be attributed to problems of bulk supply, fabrication, or postmanufacturing treatment. Orthopedic device manufacturers should keep samples of each lot of polyethylene used and provide components with serial numbers so that the source, composition, and properties of the original bulk material and material "as fabricated" can be documented. This would permit researchers studying revisions or postmortem samples to determine the changes in the polyethylene over time in vivo, thus improving the understanding of this crucial material. If manufacturers were to include dimensions and tolerances of the polyethylene inserts in their product literature, accurate measurements of wear of retrieved specimens may be possible.

Acetabulum↗
PubMed1992

Brain and tissue distribution of polyethylene glycol-conjugated superoxide dismutase in rats.

BACKGROUND AND PURPOSE: The purpose of this study was to determine the distribution of polyethylene glycol-conjugated superoxide dismutase in the brain, cerebrospinal fluid, and various organs. METHODS: Distribution of iodine-125-labeled polyethylene glycol-conjugated superoxide dismutase was determined in three groups of male Sprague-Dawley rats: a normotensive sham control group (n = 9) and groups given 125I-labeled polyethylene glycol-conjugated superoxide dismutase either 30 minutes before (n = 10) or 30 minutes after (n = 7) norepinephrine-induced hypertensive injury. RESULTS: In the first 30 minutes after intravenous administration, polyethylene glycol-conjugated superoxide dismutase plasma activity declined to 70% of the initial value and then decreased negligibly between 30 and 90 minutes. Levels of 125I-labeled polyethylene glycol-conjugated superoxide dismutase in normotensive animals were low in the brain and cerebrospinal fluid and highest in kidney. Brain levels of polyethylene glycol-conjugated superoxide dismutase were elevated only in those rats that received it before hypertensive injury; however, cerebrospinal fluid levels were elevated in animals receiving the drug either before or after hypertensive injury. CONCLUSION: Our results suggest that the blood-brain barrier becomes more permeable to polyethylene glycol-conjugated superoxide dismutase only during the hypertensive period but that the blood-cerebrospinal fluid barrier sustains more permanent injury. We suggest that the therapeutic effectiveness of polyethylene glycol-conjugated superoxide dismutase in hypertensive brain injury is due to its action in the vascular wall or to its extracellular activity in the cerebrospinal fluid.

Animals↗
PubMed1992

Polyethylene wear in unicondylar knee prostheses. 106 retrieved Marmor, PCA, and St Georg tibial components compared.

106 unicondylar knee replacement tibial components were retrieved and analyzed for the amount and type of polyethylene wear. Three different designs were retrieved which had essentially the same femorotibial conformity. Each design showed a characteristic failure pattern. The polyethylene of PCA tibial components showed serious delamination after only short durations, as a result of heat pressing. St Georg sledge prostheses showed some delamination after 4 years' duration due to sub-surface cracks which were initiated by fusion defects in the polyethylene; metal backing of the components did not affect delamination of this prosthesis. The Marmor designs showed the least wear, with shiny depressions and surface pitting; no delamination was observed in the Marmor prosthesis. Molecular weight determination by gel permeation chromatography and analysis of crystallinity using Fourier transformation infra-red spectroscopy demonstrated that St George polyethylene had higher molecular weight and crystallinity than Marmor polyethylene. In some of the components investigated, crystallinity and molecular weight of the polyethylene were reduced under the wear track when compared with the unworn polyethylene. Since fusion defects may cause delamination of polyethylene we urge manufacturers to reduce the number of such defects.

Corrosion↗
PubMed1992

Surface-immobilized polyethylene oxide for bacterial repellence.

Polyethylene terephthalate films were surface-modified with polyethylene oxide (18,500 g/mol) using a solution technique described previously. These films were investigated for their resistance to bacterial adhesion. Three bacterial strains most commonly associated with implant infections, Staphylococcus epidermidis, Staphylococcus aureus and Pseudomonas aeruginosa, were cultured in tryptic soya broth, human plasma and human serum on the polymeric substrates. Significant reductions (between 70 and 95%) in adherent bacteria were observed on the polyethylene oxide-modified substrates compared to the untreated control polyethylene terephthalate. Surface modification with polyethylene oxide may reduce the risk of implant-associated infections. Plasma fibrinogen was observed to play an important role in the adhesion of all three of these species on both the polyethylene oxide-modified and control polyethylene terephthalate materials.

Bacterial Adhesion↗