SEARCH · PubMed Health

Results for “LUBRICATION”

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 163 records · Page 9Linked to original sources

PubMed1999

Effect of protein lubrication on the wear properties of materials for prosthetic joints.

The effects of pre-dilution and other modifications of bovine serum lubricants on the wear properties of UHMW polyethylene acetabular cups were evaluated in a hip joint simulator. The wear rate increased, and a nonphysiological type of surface-pitting occurred, when the serum was pre-diluted to 40% or lower concentration. During the wear test, the equilibrium temperature and the precipitation of proteins were substantially greater with zirconia balls than with cobalt-chromium. Protein precipitation, a potential modulator of in vitro wear, was shown to be temperature, concentration, and time-dependent in water-bath tests, which indicated that ball-cup interface temperatures in the simulator must be above 60 degrees C, i.e., well above the bulk lubricant temperature, to account for wear test protein precipitation. Several modifications of serum that were, in part, intended to decrease the tendency for protein precipitation were found to markedly affect the wear properties of the two combinations of materials. In particular, modified serum, which lacked some of the higher molecular weight proteins, produced a much higher wear rate than a control serum with the same initial protein concentration. The results indicated directions for further research to clarify the lubricating properties of serum, and for developing a universal standard test lubricant.

Animals↗

PubMed2003

Mechanical effects of the intraarticular administration of high molecular weight hyaluronic acid plus phospholipid on synovial joint lubrication and prevention of articular cartilage degeneration in experimental osteoarthritis.

OBJECTIVE: To examine in vivo the effects of a mixture of high molecular weight hyaluronic acid (HA) plus phospholipids on joint lubrication and articular cartilage degeneration. METHODS: Experimental osteoarthritis (OA) of the right knee was induced by anterior cruciate and medial collateral ligament transection in 40 rabbits. The animals were subjected to 8 consecutive weekly intraarticular administrations of high molecular weight HA (the HA200 group), conventional molecular weight HA (the HA80 group), or high molecular weight HA plus L-delta dipalmitoyl phosphatidylcholine liposomes (the PHA group) and were killed 1 week after the final injection. The remaining transected right knees (the OA group) and randomly selected nontransected contralateral left knees (the control group) were collected simultaneously. Each group (n = 10) was divided into 2 equal subgroups, one of which was evaluated histologically while the other was subjected to a lubricating ability test using a pendulum friction tester. RESULTS: The injected knees had a tendency to demonstrate less damage to the articular cartilage compared with the OA group, and the histologic findings in all groups except for the PHA group differed significantly from the control group. There was a significant difference in the mean +/- SD friction coefficient between the control group (0.0100 +/- 0.00300) and the OA (0.0206 +/- 0.00649), HA200 (0.0190 +/- 0.00427), and HA80 (0.0177 +/- 0.00712) groups (P < 0.05 for each comparison), but not between the control group and the PHA group (0.0150 +/- 0.00330) (P = 0.15). CONCLUSION: To our knowledge, this is the first in vivo study to examine whether intraarticular injections of phospholipids influence joint lubrication by acting as a boundary lubricant, thus protecting articular cartilage from degenerative changes.

Animals↗

PubMed2007

Facilitated stent delivery using applied topical lubrication.

OBJECTIVES: The goal of this study was to assess the utility of topical lubrication to aid stent delivery in challenging anatomy and its effects on long-term clinical outcome. BACKGROUND: Failed stent delivery is encountered in up to 5% of percutaneous coronary interventions (PCI). METHODS: The effectiveness of topically applied lubrication to facilitate stent delivery after failed stent placement was evaluated in 20 (2.5%) out of 813 consecutive patients undergoing PCI. Initial attempts at stent delivery failed despite balloon predilatation and use of moderate-to-stiff guidewires in all patients. The lubricious solution used was Rotaglide, a phospholipid emulsion originally designed to reduce catheter friction during rotational atherectomy. Following unsuccessful delivery, stents were removed from the guiding catheters, topically saturated with Rotaglide, and deployment immediately reattempted. Procedural efficacy and long-term clinical outcomes were assessed. RESULTS: The study population included 20 patients aged 69 +/- 10 years, all of whom had complex lesions (ACC/AHA Class B(2) or C). Rotaglide lubricated stents were successfully deployed at the target lesions in 17 of the 20 patients (85%). Patients were followed 19.5 +/- 3.2 months after their index procedure. There were no periprocedural complications or subacute stent thromboses. Of the 14 patients with drug-eluting stents, none had clinical restenosis or target vessel revascularization. Target lesion revascularization secondary to restenosis was required in 1 of 3 patients treated with bare-metal stents. CONCLUSIONS: Topical lubrication is a simple and effective aid for stent delivery in complex lesions. Rotaglide appears safe and biocompatible with drug-eluting stents.

Aged↗

PubMed2006

Self-assembling peptides as injectable lubricants for osteoarthritis.

The self-assembly of peptides is explored as an alternative route towards the development of new injectable joint lubricants for osteoarthritis (OA). The versatility of the peptide chemistry allows the incorporation of behavior reminiscent of hyaluronic acid (HA), while the triggered in situ self-assembly provides easy delivery of the samples by injection due to the low viscosity of the peptide solutions (that are initially monomeric). Using design criteria based on the chemical properties of HA, a range of de novo peptides were prepared with systematic alterations of charge and hydrophilicity that self-assembled into nematic fluids and gels in physiological solution conditions. The frictional characteristics of the peptides were evaluated using cartilage on cartilage sliding contacts along with their rheological characteristics. Peptide P(11)-9, whose molecular, mesoscopic, and rheological properties most closely resembled HA was found to be the most effective lubricant amongst the peptides. In healthy static and dynamic friction testing (corresponding to healthy joints) P(11)-9 at 20-40 mg/mL performed similar to HA at 10 mg/mL. In friction tests with damaged cartilage (corresponding to early stage OA) P(11)-9 was a less efficient lubricant than HA, but still the best among all the peptides tested. The results indicate that de novo self-assembling peptides could be developed as an alternate therapeutic lubricant for early stage OA.

Amino Acid Sequence↗

PubMed1992

Physical and lubrication properties of magnesium stearate.

The lubrication properties of two commercial-grade magnesium stearates were studied. Their moisture contents and crystal structures were similar. There were minor differences in their fatty acid composition, but the differences did not affect the lubrication properties. The lubrication properties correlated with particle size distributions and specific surface area. The effect of these parameters was further studied with unmilled and milled chemically pure magnesium stearate. Milling decreased the particle size and increased the specific surface area. In both cases, the batch with a smaller particle size and larger specific surface area had considerably better lubricity.

Adjuvants, Pharmaceutic↗

PubMed2004

Acute toxicity investigations of ester-based lubricants by using biotests with algae and bacteria.

Although ester-based lubricants are ecologically acceptable due to their good biodegradability, there are still some environmental ecotoxicological impacts that have to be considered. Information on the acute ecotoxicological behavior of lubricants is obtained in this work using several single species bioassays. In previous studies it was observed that lubricating fluids containing additives for the enhancement of their technical performance were more problematic than base fluids especially with respect to algae growth inhibition. In order to clarify the influence of additives, the anti-wear additive tri-n-butyl phosphate was tested. It was very toxic to algae though not to bacteria. Additionally, a mixture of this additive with a base fluid is characterized. Despite the high toxicity of the single additive, the water extract of the mixture of tri-n-butyl phosphate with hydraulic base fluid caused almost no toxicity. Therefore, tri-n-butyl phosphate cannot explain the effect observed for the toxicity of water extracts of the commercially available lubricants.

Biological Assay↗

PubMed1992

Potential neurotoxin formation in thermally degraded synthetic ester turbine lubricants.

Under extreme conditions of thermal degradation, a potent neurotoxin, trimethylolpropane phosphate (TMPP), may be formed by reaction of tricresyl phosphate (TCP, an anti-wear additive) and trimethylolpropane esters (TMPE) of carboxylic acids that may be contained in turbine engine lubricant formulations. The neurotoxin is only formed at extreme temperatures (350-700 degrees C), which has minimized concern for use of the synthetic lubricants under intended applications; however, since researchers are often not privy to the proprietary composition of such lubricants, extreme caution should be exercised in studies of or applications of synthetic lubricants degraded under extreme conditions.

Animals↗

PubMed2005

[Use of lubricants in urology. Indications and results].

Lubricants are used for catheterization and/or endoscopic maneuvers. "The lubricant" should guarantee sufficient lubrification of the urinary tract, good visualization during endoscopy, and excellent local anesthesia. Additionally, asepsis or reliable control of the local bacterial flora of the urethra should be ensured. Modern lubricants fulfil these recommendations; in addition, they provide therapeutic opportunities for local therapy, for instance, of non-gonococcal urethritis. The latest results show that there are a few lubricants with antimicrobiotic influence on MRSA (methicillin-resistant Staphylococcus aureus), which is of great importance because of the steady increase in MRSA-dependent infections.

Anesthetics↗

PubMed2004

Isolation and characterization of novel strains of Pseudomonas aeruginosa and Serratia marcescens possessing high efficiency to degrade gasoline, kerosene, diesel oil, and lubricating oil.

Bacteria possessing high capacity to degrade gasoline, kerosene, diesel oil, and lubricating oil were screened from several areas of Hokkaido, Japan. Among isolates, two strains, WatG and HokM, which were identified as new strains of Pseudomonas aeruginosa and Serratia marcescens species, respectively, showed relatively high capacity and wide spectrum to degrade the hydrocarbons in gasoline, kerosene, diesel, and lubricating oil. About 90-95% of excess amount of total diesel oil and kerosene added to mineral salts media as a sole carbon source could be degraded by WatG within 2 and 3 weeks, respectively. The same amount of lubricating oil was 60% degraded within 2 weeks. Strain HokM was more capable than WatG in degrading aromatic compounds in gasoline. This strain could also degrade kerosene, diesel, and lubricating oil with a capacity of 50-60%. Thus, these two isolates have potential to be useful for bioremediation of sites highly contaminated with petroleum hydrocarbons.

Biodegradation, Environmental↗

PubMed2006

Effect of low protein concentration lubricants in hip simulators.

BACKGROUND: Proteins play an important role as boundary lubricants in vivo and in vitro. Hip simulator studies have tested various protein concentrations of lubricants. Several groups reported that nonphysiological pits were created with low protein concentrations. Our study showed details of wear findings with low protein concentrations. This may be the first mapping of the run-in wear morphology on ultra high molecular weight polyethylene (UHMWPE) cups. METHODS: The UHMWPE cups used were holding cobalt chrome (CoCr) balls. This study was run on orbital-type hip simulators at up to 1.0 million cycles (Mc). The lubricant was bovine calf serum (0, 3, 5, 7, 10, and 1 mg/ml protein concentrations). Two volumes of lubricant were used (40 and 16 ml). Volumetric wear rates were calculated and the cup surfaces were observed using reflected light microscopy (RLM) and scanning electron microscopy (SEM). RESULTS: The 40-ml volume showed a lower wear rate than the 160-ml volume. The RLM findings showed that the machine marks gradually disappeared up to 1.Mc, but there were no obvious pits on the polyethylene surface. The SEM findings showed nonphysiological wear phenomena in the 0-mg/ml protein concentration and physiological wear phenomena in the low protein concentrations. In the main bearing wear area, many nodules were observed with fibrils. In the peripheral bearing wear area, mainly ripples were observed. At the nonbearing wear area, folds were observed. CONCLUSIONS: Our study showed the microwear findings with low-protein serum: First, folds were formed, followed by ripples, and finally nodules accompanied by fibrils. During the run-in wear phase, nodules and fibrils had already appeared in the main bearing wear area. Thus, we need to investigate more details of the wear process when folds or ripples change to nodules at the main wear area in the run-in wear.

Animals↗

PubMed2005

A preliminary report on patient acceptance of a novel intra-oral lubricating device for the management of radiotherapy-related xerostomia.

Management of radiotherapy-related xerostomia is difficult. Saliva substitutes are helpful but the effects are short-lived. The purpose of the study was to develop a prototype intra-oral lubricating device for the management of radiotherapy-related xerostomia and to evaluate patient acceptance. An intra-oral lubricating device was fabricated that incorporated a reservoir in the palatal vault and permitted slow release of saliva substitute by the patient. Preliminary clinical testing was done in five patients with radiotherapy-related xerostomia. A measure incorporating seven questions was used to explore patient acceptance. The device was simple to fabricate using materials available in a technical laboratory. All patients were able to wear the device for at least 4 h per day throughout the test period. The device was considered easy to use and clean. Some impairment of speech and chewing was noted although this appeared to be related to the bulkiness of the reservoir. General oral comfort was improved due to the lubricating effect. The bulk of the reservoir was reduced as a consequence of patient feedback. The design addressed key problems associated with previous lubricating systems. Patient reports on oral functioning with the device in situ provided pivotal information on the device's utility.

Cranial Irradiation↗

PubMed1988

Effects of four lubricants used during incremental insertion of two types of visible light-activated composites.

The effect of alcohols, bonding resins, or dentin adhesives on the adhesive bond between the layers of visible light-activated composites when used as lubricant for composite instruments was investigated. The results of this study indicated that alcohols are not compatible with certain BIS-GMA-based and UEDMA-based composite systems (Herculite and Heliomolar composites were used for this investigation). Use of ethanol as a lubricant caused pure adhesive failure and low bond strength in UEDMA-based composite (Heliomolar), indicating that the bond strength was less than the cohesive strength of the composite. A bonding resin of a similar brand (or the same system) used to lubricate the composite instrument did not affect the bond strength of the bonded composite specimens. In light of this study, a bonding resin of the same resin system as the composite may be the most suitable and reliable material to be used for lubricating the composite instrument.

1-Propanol↗

PubMedDate not supplied

Relationship between biomedical catheter surface properties and lubricity as determined using textural analysis and multiple regression analysis.

In this study, the surface properties of and work required to remove 12 commercially available and developmental catheters from a model biological medium (agar), a measure of catheter lubricity, were characterised and the relationships between these properties were examined using multiple regression and correlation analysis. The work required for removal of catheter sections (7 cm) from a model biological medium (1% w/w agar) were examined using tensile analysis. The water wettability of the catheters were characterised using dynamic contact angle analysis, whereas surface roughness was determined using atomic force microscopy. Significant differences in the ease of removal were observed between the various catheters, with the silicone-based materials generally exhibiting the greatest ease of removal. Similarly, the catheters exhibited a range of advancing and receding contact angles that were dependent on the chemical nature of each catheter. Finally, whilst the microrugosities of the various catheters differed, no specific relationship to the chemical nature of the biomaterial was apparent. Using multiple regression analysis, the relationship between ease of removal, receding contact angle and surface roughness was defined as: Work done (N mm)=17.18+0.055 Rugosity (nm)-0.52 Receding contact angle ( degrees ) (r=0.49). Interestingly, whilst the relationship between ease of removal and surface roughness was significant (r=0.48, p=0.0005), in which catheter lubricity increased as the surface roughness decreased, this was not the case with the relationship between ease of removal and receding contact angle (r=-0.18, p>0.05). This study has therefore uniquely defined the contributions of each of these surface properties to catheter lubricity. Accordingly, in the design of urethral catheters, it is recommended that due consideration should be directed towards biomaterial surface roughness to ensure maximal ease of catheter removal. Furthermore, using the method described in this study, differences in the lubricity of the various catheters were observed that may be apparent in their clinical use.

Biocompatible Materials↗

PubMed2005

Protein-mediated boundary lubrication in arthroplasty.

Wear of articulated surfaces can be a major lifetime-limiting factor in arthroplasty. In the natural joint, lubrication is effected by the body's natural synovial fluid. Following arthroplasty, and the subsequent reformation of the synovial membrane, a fluid of similar composition surrounds the artificial joint. Synovial fluid contains, among many other constituents, a substantial concentration of the readily adsorbing protein albumin. The ability of human serum albumin to act as a boundary lubricant in joint prostheses has been investigated using a pin-on-disc tribometer. Circular dichroism spectroscopy was employed to follow the temperature- and time-dependent conformational changes of human serum albumin in the model lubricant solution. Effects of protein conformation and polymer surface hydrophilicity on protein adsorption and the resulting friction in the boundary lubrication regime have been investigated. Unfolded proteins preferentially adsorb onto hydrophobic polymer surfaces, where they form a compact, passivating layer and increase sliding friction-an effect that can be largely suppressed by rendering the substrate more hydrophilic. A molecular model for protein-mediated boundary friction is proposed to consolidate the observations. The relevance of the results for in vivo performance and ex vivo hip-joint testing are discussed.

Adsorption↗

PubMed2006

The effect of hyaluronic acid and phospholipid based lubricants on friction within a human cartilage damage model.

The lubricating abilities of different formulations of high molecular weight hyaluronic acid (HA), dipalmitoyl phosphatidylcholine (DPCC) and mixtures of both HA and DPCC were assessed in an in vitro model. Levels of start-up friction were determined using an osteoarthritis (OA) damaged human cartilage model set within a specially designed friction rig. To examine the long term benefits of HA, the extent of penetration of HA into cartilage tissue was investigated using fluorescently labelled HA and confocal microscopy. It was found that in this model, all formulations of HA and the majority of DPCC lubricants reduced friction (HA 5 and 10 mg ml(-1), DPPC 200 mg ml(-1) reductions of 51.9%, 46.7% and 46.5% respectively), compared to a Ringers solution control. Lubrication was found not to be concentration dependent for HA formulations, but concentration was key for DPCC lubrication (100 mg ml(-1) reduced friction by only 15.9%). By combining HA and DPCC (HA/DPPC; 5 mg ml(-1)/100 mg ml(-1) and 10 mg ml(-1)/200 mg ml(-1)), a further improvement was noted (69.5% and 61.9%, respectively) as the mean levels of friction were reduced by up to a further 17% than the most effective individual formulation (HA 5 mg ml(-1)). Penetration of HA into bovine cartilage by up to 300 microm from the surface was observed over a 48 h period. It was observed that HA specifically targeted the chondrocytes as it was primarily found within the lacunae surrounding the cells.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2004

Testing the ecotoxicology of vegetable versus mineral based lubricating oils: 1. Degradation rates using tropical marine microbes.

Vegetable-derived lubricants (VDL) might be more biodegradable than mineral-derived lubricants (MDL) due to the absence of high molecular weight aromatics, but this remains largely untested in tropical conditions. In this laboratory study, the degradation rates of 2-stroke, 4-stroke and hydraulic VDLs were compared with their MDL counterparts in the presence of mangrove and coral reef microbial communities. While MDLs were comprised largely of unresolved saturated and some aromatic hydrocarbons, their VDL counterparts contained, potentially more degradable, fatty acid methyl esters. Degradation of some VDL was observed by day 7, with the 2-stroke VDL markedly consumed by mangrove microorganisms and the hydraulic VDL degraded by both microorganism communities after this short period. All of the VDL groups were significantly more degraded than the comparable MDLs mineral oil lubricants over 14 days in the presence of either mangrove or coral reef microbial communities. In general the mangrove-sourced microorganisms more efficiently degraded the lubricants than reef-sourced microorganisms.

Animals↗

PubMed2004

Particle interaction of lubricated or unlubricated binary mixtures according to their particle size and densification mechanism.

The aim of this study is to assess an experimental approach for technological development of a direct compression formulation. A simple formula was considered composed by an active ingredient, a diluent and a lubricant. The active ingredient and diluent were selected as an example according to their typical densification mechanism: the nitrofurantoine, a fragmenting material, and the cellulose microcrystalline (Vivapur), which is a typical visco-elastic material, equally displaying good bind and disintegrant properties. For each ingredient, samples of different particle size distribution were selected. Initially, tabletability of pure materials was studied by a rotary press without magnesium stearate. Vivapur tabletability decreases with increase in particle size. The addition of magnesium stearate as lubricant decreases tabletability of Vivapur of greater particle size, while it kept unmodified that of Vivapur of lower particle size. Differences in tabletability can be related to differences in particle-particle interactions; for Vivapur of higher particle size (Vivapur 200, 102 and 101), the lower surface area develops lower surface available for bonds, while for Vivapur of lower particle size (99 and 105) the greater surface area allows high particle proximity favouring particle cohesivity. Nitrofurantoine shows great differences in compression behaviour according to its particle size distribution. Large crystals show poorer tabletability than fine crystals, further decreased by lubricant addition. The large crystals poor tabletability is due to their poor compactibility, in spite of high compressibility and plastic intrinsic deformability; in fact, in spite of the high densification tendency, the nature of the involved bonds is very weak. Nitrofurantoine samples were then mixed with Vivapurs in different proportions. Compression behaviour of binary mixes (tabletability and compressibility) was then evaluated according to diluents proportion in the mixes. The mix of either nitrofurantoine large crystals or fine crystals with cellulose microcrystalline showed a negative interaction in all proportions, whatever particle sizes. The lubricant addition induced a positive interaction with Vivapur of greater particle size distribution (200, 102 and 101) favouring higher particle adhesivity, while it maintained unaltered that of Vivapurs of lower particle size (105 and 99). Definitely, when cohesive forces are predominant (Vivapur 105 and 99), the establishment of adhesive bonds between nitrofurantoine and Vivapur remain unnoticed; on the contrary, when cohesion bonds between microcrystalline cellulose particles are weakened by the presence of magnesium stearate, the existence of adhesion bonds between particles of different nature is in evidence, leading to a positive interaction.

Compressive Strength↗

PubMed2006

Measurement of the surface energy of lubricated pharmaceutical powders by inverse gas chromatography.

The objective of the study was to determine whether lubrication of pharmaceutical powders with magnesium stearate (MgSt) results in a change in the surface energy of the powder, and to assess whether surface energy changes, if any, are correlated to lubricant concentration and blend time. The surface energies of microcrystalline cellulose (MCC), lactose, and blends of each material with MgSt, prepared at a range of concentrations and blending times were measured using inverse gas chromatography. The physical distribution of MgSt in the blend was mapped by energy dispersive spectrometry. Overall, there was a reduction in the dispersive surface energy of MCC-MgSt blends with increase in MgSt concentration, that was attributed to increasing coverage of the high-energy sites on microcrystalline cellulose by magnesium stearate. MgSt concentration had a larger effect on dispersive energy than the blending time of the powder with lubricant. X-ray maps of blend samples indicated a heterogeneous distribution of the lubricant in the blend and on the excipient particles. Measurement of the specific component of surface energy indicated that MgSt interacts with excipient powders through non-specific forces rather than acid-base interactions. No distinction among lactose-MgSt blends could be made on the basis of dispersive energy because of similar surface energies of the native materials.

Cellulose↗