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At least 577 records · Page 32Linked to original sources
PubMed1994

Enhancement of self-association of human spectrin by polyethylene glycol.

1. In the presence of polyethylene glycol, the self-association of human spectrin is enhanced in a manner that depends approx. exponentially on the mass concentration of polyethylene glycol. 2. For a given mass concentration, the enhancement is independent of the molecular weight of the polyethylene glycol. 3. These data are consistent with the operation of excluded volume effects, and support the contention that the association of spectrin is likely to be increased in the presence of the high concentration of hemoglobin within the erythrocyte in vivo.

Binding Sites↗
PubMed1992

Biological activities of polyethylene-glycol immunoglobulin conjugates. Resistance to enzymatic degradation.

Serum IgG has been covalently bonded to polyethylene glycols of either 2000 or 8000 molecular weight to produce immunoglobulin conjugates with 4.4-27.2% of primary amines bonded to polyethylene glycol. Polyethylene glycol immunoglobulin conjugates retain the ability, comparable to native IgG, to bind to a range of protein and microbial antigens, but have a reduced ability to bind to Fc receptors or to fix complement C3. When 6.8% or more of available primary amines are conjugated, IgG-PEG conjugates are impervious to trypsin, and at 14% or more conjugation, more resistant than native IgG to pepsin and chymotrypsin. We suggest that PEG-Ig conjugates may be useful for the oral treatment of various gastrointestinal diseases in which secretory humoral immunity is insufficient.

Antigens, Protozoan↗
PubMed1985

Induction of elongation factor Tu-GDP crystal polymorphism by polyethylene glycol contaminants.

Trypsin-modified elongation factor (EF-)Tu-GDP from Escherichia coli is known to crystallize in several different unit cells under apparently identical conditions. The crystal polymorphism was investigated and found to be correlated with the source of polyethylene glycol used in the crystallization procedure. The use of highly purified polyethylene glycol promoted the growth of a new crystal form belonging to space group P2(1)2(1)2(1) with cell dimensions of a = 71.9 A, b = 74.7 A, c = 170.9 A and two molecules per asymmetric unit. In extensive crystallization trials, substances that typically contaminate commercial preparations of polyethylene glycol were screened. The final results show that the presence of the divalent anions, HPO4(2-) or SO4(2-), at different concentrations induce the growth of two known crystal forms belonging to space groups C222(1) and P4(3)2(1)2. The relevancy of the findings is discussed.

Crystallization↗
PubMed1980

Comparison between inactivated Sendai virus, polyethylene glycol and Tween 80 as permeabilizing agents for introduction of neurospora endonuclease into X-irradiated cells.

Inactivated Sendai virus, polyethylene glycol and Tween 80 were employed as agents to make X-irradiated CHO cells permeable for Neurospora endonuclease, in studies designed to evaluate the influence of this enzyme on the frequencies of X-ray-induced chromosome aberrations. Polyethylene glycol and Tween 80 were found not to be very efficient in making cells permeable. Besides, polyethylene glycol was found to increase the frequencies of X-ray-induced chromosomal aberrations.

Animals↗
PubMed1978

The effects of partially filled polyethylene tube intraosseous implants in rats.

Polyethylene tubes obturated flush at one end and 1 mm. short at the opposite end with gutta percha and Grossman's cement as the cementing media were implanted in rat tibias. The gutta-percha, the set Grossman's cement, and the polyethylene implant were well tolerated by the rat intraosseous tissues. There was no significant inflammatory response at either the flush end or the short end of the polyethylene implant.

Animals↗
PubMed1986

Anticonvulsant activity of two polyethylene glycols in mice.

The anticonvulsant activity of two polyethylene glycols of different molecular weight (400 and 4000) was tested in mice. The two substances were inactive in the maximal electroshock test, but, when intraperitoneally administered, were efficacious in the pentetrazole and strychnine seizure tests. Polyethylene glycol 4000 showed the most potent anticonvulsant action. On the contrary, when polyethylene glycols were orally administered, they did not alter the time for seizure onset and for death.

Animals↗
PubMed1991

Wear of cross-linked polyethylene against itself: a material suitable for surface replacement of the finger joint.

Cross-linking of polyethylene (XLPE) has dramatically improved its properties in industrial applications, and it may also have some application in the field of human joint replacement. Additionally it has the advantage of permitting a lower molecular weight base material to be used, so that components may be injection moulded rather than machined. This study therefore investigates the wear resistance of medical grade cross-linked polyethylene (XLPE), cross-linked by a silane-grafting process, with a molecular weight between cross links of 5430 g mol(-1). This first report investigates the wear resistance of XLPE against itself, because for certain joints, such as the metacarpo-phalangeal joint, the material may have a high enough wear resistance to allow both bearing surfaces to be made from it. Tests were carried out both on a reciprocating pin and plate machine with pins loaded at 10 and 40 N and also on a new finger joint simulator, which simulates the loads applied to and the movements of, the metacarpo-phalangeal joint. An average wear rate of 1.8 x 10(-6) mm3 N-1 m-1 was found (range 0.9-2.75 x 10(-6) mm3 N-1 m-1). This is about six times greater than the wear rate of non-cross-linked ultra high molecular weight polyethylene (UHMWPE) against stainless steel, but for applications with low loading, such as the metacarpo-phalangeal joint, this material is shown to have adequate wear resistance. The coefficient of friction was 0.1, which is similar to that of UHMWPE on stainless steel.

Humans↗
PubMed1983

Silane cross-linked polyethylene for prosthetic applications. Part I. Certain physical and mechanical properties related to the nature of the material.

Certain physical and mechanical tests have been conducted and scanning electron microscopy carried out in order to characterize a high density polyethylene cross-linked using vinyl trimethoxysilane. It is suggested that this cross-linked polyethylene could be an alternative to high molecular weight polyethylene for prosthetic applications.

Biomechanical Phenomena↗
PubMed1984

Silane crosslinked polyethylene for prosthetic applications. II. Creep and wear behaviour and a preliminary moulding test.

Creep and wear tests have been carried out on a high density polyethylene crosslinked using a silane. A comparison of the results with those obtained for ultra high molecular weight polyethylene (RCH 1000) indicates the superiority of the crosslinked material. It can be injection moulded without difficulty. It is our conclusion that silane crosslinked polyethylene is an exciting prospect in the field of prosthetic materials.

Biocompatible Materials↗
PubMed1989

Use of high-performance polyethylene fibres as a reinforcing phase in poly(methylmethacrylate) bone cement.

First results are presented concerning the elastic and ultimate mechanical behaviour of p(MMA) bone cement reinforced with as-received and surface-modified Spectra 900 polyethylene fibres. Even though the surface chemistry and reactivity of the fibres was modified, the surface oxidation and surface grafting treatments of the polyethylene fibres apparently did not significantly affect the mechanical properties of the polyethylene-reinforced p(MMA) bone cement or improve the interfacial bonding. This may be attributed to the rather unfavourable area-to-volume ratio of PE fibres for such treatments, as well as to the necessarily low content of PE fibres in the bone cement which does not allow a clear differentiation between the various samples.

Bone Cements↗
PubMed1992

ESCA investigation of low-temperature ammonia plasma-treated polyethylene substrate for immobilization of protein.

A low-temperature radiofrequency plasma excited in anhydrous ammonia was used to modify polyethylene substrate surfaces for covalent immobilization of proteins. Electron spectroscopy for chemical application (ESCA) was used for surface characterization of polyethylene to a depth scale of 7 nm. The data revealed that surface modification is extensive and occurs in seconds at low discharge power. Primary amino functionalities were detected on the polyethylene surface and the level is dependent on plasma parameters. 125I-labelled antibodies covalently attached to amino groups via glutaraldehyde allowed the conditions for optimum level of primary amine to be established. Both ESCA data and protein loadings are in excellent agreement.

Ammonia↗
PubMed1995

Comparison of covalently and physically cross-linked polyethylene glycol-based hydrogels for the prevention of postoperative adhesions in a rat model.

A covalently and a physicochemically cross-linked hydrogel, both based primarily on polyethylene glycol and both formed in situ, were compared side by side in a rat uterine horn devascularization and serosal injury model for efficacy in adhesion prevention. The primary difference between the two materials was the nature of their cross-linking. The covalently cross-linked hydrogel was a photopolymerized polyethylene glycol-co-lactic acid diacrylate, and the physically cross-linked hydrogel was a polyethylene glycol-co-polypropylene glycol, Poloxamer 407. In the surgical model employed, application of the covalently cross-linked hydrogel reduced the extent of adhesion formation from 75 +/- 10% in the control group to 16 +/- 6% (mean +/- s.d., P < 0.001). Application of the physically cross-linked hydrogel reduced adhesion formation to 38 +/- 19% (P < 0.01). Retention of the two hydrogels upon the site of application was also evaluated. The covalently cross-linked hydrogel formed a continuous barrier upon the uterine horns for more than 4 d, while the physicochemically cross-linked hydrogel was present upon the uterine horns for less than 2 d. This difference in retention was probably the cause of the difference in efficacy and may be attributed to the nature of the cross-linking.

Animals↗
PubMed1986

Polyethylene glycol-enhanced nephelometric quantification of bovine submaxillary mucin with Helix pomatia lectin.

A new principle for quantification of intact mucin has been developed. The method is reproducible, simple, and sensitive at the submicrogram level and can be performed within an hour. The procedure involves incubation of mucin (bovine submaxillary mucin) and polyethylene glycol with the lectin from the snail Helix pomatia and the complexes formed are quantitated by nephelometry. Polyethylene glycol was found to enhance the affinitin reaction in a dose-dependent fashion. Increasing concentrations of acetate or citrate led to decreasing light scattering of the polyethylene glycol--bovine submaxillary mucin--H. pomatia lectin reaction mixture. Results from displacement studies with N-acetyl-galactosamine suggest that H. pomatia lectin may contain an allosteric type of regulatory site. The quantitative results obtained with bovine submaxillary mucin using the new method correlated well with those obtained with an established method for neuraminic acid determination after neuraminidase digestion (R = 0.969, P less than 0.001; n = 24).

Animals↗
PubMed1986

Study on the pre-haemolytic complex formed upon polyethylene glycol-induced activation of mouse complement.

The stability and nature of haemolytic activity generated in normal mouse serum upon precipitation with a critical amount of polyethylene glycol and incubation of the redissolved precipitate in the presence of 10 mM EDTA were investigated. The activity appeared to be stable at 0 degrees C which enabled further analysis. The haemolytic mixture was subfractionated by repeated differential polyethylene glycol precipitation yielding two preparations with little or no haemolytic activity by themselves, but which regained activity upon recombination. Material precipitating between 4 and 9% polyethylene glycol became haemolytic when combined with C5-deficient serum. The ultracentrifugation profile of this subfraction strongly suggested the presence of C56-complexes.

Animals↗
PubMed1981

Concentration of human respiratory syncytial virus using ammonium sulfate, polyethylene glycol or hollow fiber ultrafiltration.

Human respiratory syncytial virus was concentrated by polyethylene glycol or ammonium sulfate precipitation as well as by hollow ultrafiltration. Recoveries obtained were respectively 49.4%, 47.7%, and 75.2%; however, further analysis of these results by resuspension experiments showed that all the infectivity could be recovered from the different concentrates. The protein content of polyethylene glycol concentrates was much lower than those of ammonium sulfate or hollow fiber ultrafiltration. Electron microscopy revealed that the morphological integrity of virus particles was unaffected by the concentration methods used. Purified virus was obtained when polyethylene glycol concentrates were centrifuged through two successive density gradients.

Ammonium Sulfate↗
PubMed1984

Polyethylene glycol as a protector against head and neck irradiation.

Mice injected i.p. with polyethylene glycols (PEG) 20 min prior to head and neck X irradiation with 1650 rad showed improved survival, increased food and water consumption, and retention of body weight compared with irradiated controls. The LD 50/15 for PEG-treated mice was 1900 +/- 108 rad compared to 1527 +/- 56 for the controls. PEG of molecular weights 200, 400, and 600 afforded significant levels of radioprotection; PEG of molecular weights 1000, 1450, 4000, and 20,000 when given at maximum tolerated doses (approximately 0.5 LD 50) did not. The degree of radioprotection by PEG with molecular 400 given 20 min before irradiation increased with dose up to the maximum tolerated dose of 6.4 g/Kg. Significant, but lower, levels of radioprotection were observed when the PEG was given 5 min after irradiation. Mice injected i.p. with PEG, cystamine, 5-thioglucose, chlorpromazine, polyethylene glycol monomethyl ether or polyvinylpyrrolidone all had comparable survival levels. Polypropylene glycol, polyethylene glycol diacrylate, and polycaprolactonediol were more toxic than PEG and showed no radioprotection.

Animals↗
PubMed2004

Rhinolithiasis: a very late complication after dacryocystorhinostomy with rubber-gum and polyethylene stenting.

PURPOSE: To describe a rare case of rhinolith formation 21 years after dacryocystorhinostomy (DCR) with rubber gum and polyethylene tubing surgery. DESIGN: Interventional case report. METHODS: A 23-year-old-woman underwent uneventful left DCR with rubber gum and polyethylene tubing for chronic dacryocystitis. Twenty-one years later, she presented with purulent rhinorrhea, nasal obstruction, and facial pain. Computed tomography revealed a radiopaque density in the left nasal cavity. RESULTS: A rubber gum foreign body embedded with granulation tissue and a huge rhinolith was removed endoscopically through the anterior nares. After surgery, the patient reported immediate and complete relief of symptoms. CONCLUSION: Rhinoliths can develop progressively several years after DCR as a result of foreign body reaction to rubber gum or polyethylene tubing. This rare complication should be ruled out in patients complaining of purulent rhinorrhea who underwent DCR with tubing before the early 1980s.

Adult↗
PubMed2004

Wear of a highly cross-linked polyethylene liner associated with metallic deposition on a ceramic femoral head.

A 68-year-old patient underwent revision surgery for recurrent dislocation of a ceramic-on-polyethylene uncemented hip arthroplasty implanted 6 months previously. The aluminum oxide femoral head was found to have titanium deposition measuring 5 by 10 mm in an area articulating with the highly cross-linked polyethylene liner. The liner was observed to possess severe scratching produced by articulation with the titanium deposited on the ceramic head. Despite improved scratch resistance of ceramic-bearing surfaces, irregularities introduced by metallic deposition after recurrent dislocation can damage a highly cross-linked polyethylene liner.

Aged↗