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PubMed2001

Stress relaxation studies of granules as a function of different lubricants.

Viscoelastic properties of granules may be studied using stress relaxation. The effect of viscoelastic properties of different lubricants, namely magnesium stearate (Mgst), talc and precirol, on granule compaction properties was examined using texture analyzer TA-XT2i at low pressure. Normalized compact curves of stress relaxation have been discussed in relation to some parameters (flowability, porosity, viscoelasticity as well as particle size). The literature shows that viscoelasticity is always present and it produces an accompanying plastic deformation.This study revealed that bonding in compacted granules lubricated with Mgst was higher than those in compacts lubricated with the other two lubricants being studied. When studying the partial porosity of granule beds, we see that this is the result of stored energy, like the tablet case and the problem of its capping. The small stress relaxation due to talc or precirol suggested that these materials deformed principally by energy storage. However, a qualitative characterization of Mgst as tablet lubricant would be that it avoids the accumulation of stress in the compact that causes the problem of capping due to the entrapped air and therefore facilitates the optimization of pharmaceutical manufacturing. It has been possible to normalize stress relaxation using the Wischert model, represented by the sum of several exponentials, according to the nature of the lubricant. The use of texture analyzer TA-XT2i was considered to be a good technique for the evaluation of the stress relaxation of solid particles in the compression process at low pressure. It permitted the observation that viscoelasticity is influenced by the lubricant used. The brittle fracture index, like Carr's index values, has been correlated with the viscoelastic characteristics of granules.

Diglycerides↗

PubMed1998

Effects of two new lubricants on the mutagenicity of scooter exhaust particulate matter.

Scooter exhaust particulate matter, which is known to be mutagenic, has caused heavy air pollution in Shanghai. There are about 400,000 scooters in the city, and the number will not significantly decrease for several years. In order to manage the pollution caused by scooter emissions, many new catalytic instruments and additives were developed. In this paper, the effect of two new lubricants on the emission of scooter exhaust particulate matter was evaluated using gas chromatography/mass spectrometer (GC/MS), in vitro Salmonella/microsomal assay and the in vivo mouse micronucleus assay. The purpose was to learn if these new lubricants could have the ability to reduce the exhausts of particulate matter, and decrease the mutagenicity of exhaust particles. The domestic Jinniao (TN36L) vehicle was chosen as the test vehicle. The results showed that the two new lubricants reduced the emission of scooter exhaust particulate matter, including the quantity of particulate matter and the organic substances adsorbed onto the particles. Compared with the control oil, the two new lubricants reduced the emission of particulate matter by 33% and 36%. When using the two new lubricants, only 20 and 23 kinds of compounds were identified separately in the organic extracts of the exhaust particulate matter by GC/MS, while 45 kinds of compounds were detected in the organic extracts of the exhaust particulate matter when the control oil was used. Mutagenicities of the extracts of scooter exhaust particulate matter were significantly reduced when the two new lubricants were used, including the number of histidine-independent colonies over the background in TA98 with and without S9 mix in the Salmonella test (F2 sample); and the frequencies of bone marrow micronucleated polychromatic erythrocytes in the mouse micronucleus assay (both F1 and F2 samples). These results seem to indicate that these new lubricants can effectively reduce the pollution of scooter exhaust particulate.

Animals↗

PubMed2005

Impact of solid-state properties on lubrication efficacy of magnesium stearate.

The advent of high-speed tableting and slug capsule-filling machines has ushered in an increasingly important role for the lubricants to enact during manufacturing of dosage forms. Although lubricants help in processing, they can also adversely affect the flow properties and dissolution profile of the drug. It is thus critical to maintain a balance between these two behaviors, by understanding the underlying mechanisms and using their optimum concentration in the formulation. The source and manufacturing process inculcate different solid-state properties to magnesium stearate, the most commonly used lubricant, leading to variations in its lubrication efficacy. However, there has been no complete study relating the lubrication efficacy of magnesium stearate to various levels of solid state. Hence, this study was aimed at comprehensively scrutinizing the role of molecular, particle, and bulk level properties of solid state on the lubrication efficacy of magnesium stearate. A method based on net work done during compression using texture analyzer, was developed and validated to analyze its performance. Particle and bulk-level properties were studied using microscopy, particle size analysis, and particle surface area determination, and molecular level was characterized using thermal, spectroscopic, and crystallographic methods. Interplay of solid-state characteristics such as particle size, degree of agglomeration, and crystal habit were found to markedly influence the lubrication potential of magnesium stearate.

Calorimetry, Differential Scanning↗

PubMed2005

Preferences and practices related to vaginal lubrication: implications for microbicide acceptability and clinical testing.

BACKGROUND: Research on vaginal microbicides for HIV prevention is progressing rapidly; the first large-scale effectiveness trials were launched in 2004. The majority of candidate microbicides are formulated as gels, which will act as lubricants when used during sex. Preferences and practices regarding lubrication during sex, therefore, likely influence microbicide acceptability and use. Researchers seek to maximize consistent and correct use of candidate microbicides during clinical trials to enable valid estimates of product effectiveness, and if proven effective, microbicides will be widely used only if acceptable. METHODS: We conducted a comprehensive literature review and interviewed 13 key informants from nine countries in Africa, Asia, Latin America, and North America. RESULTS: We found that norms and practices regarding lubrication during sex exist in many different countries. Despite significant variation, common themes emerged. In the majority of countries, women's genital hygiene is highly valued, and women are expected to achieve a moderate amount of vaginal lubrication during sex that is neither excessive nor inadequate. Women may try to achieve this by engaging in a wide variety of vaginal practices. CONCLUSIONS: Even though some informants expressed concerns about the acceptability of lubricating microbicides in some settings, they thought that microbicides should be developed, that women and men may be willing to accept a certain level of increased lubrication in exchange for protection from HIV, and that lubricating microbicides may be considered more acceptable when perceived as genital hygiene products. Recommendations are made on how to take vaginal practices into account during clinical testing of microbicides.

Administration, Intravaginal↗

PubMed1998

The effects of coital lubricants on sperm motility in vitro.

Infertility affects approximately 15% of couples, and in about one-third the primary cause is a male factor. Patients undergoing infertility investigations frequently experience sexual dysfunction, which often is due to inadequate vaginal lubrication. This can lead to increased use of coital lubricants. The effects of such lubricants on sperm motility have not been widely studied, although sperm motility is one of the best prognostic indicators of fertilization. Using a prospective longitudinal control-based study, we analysed the effect of adding four lubricants: KY jelly, baby oil, olive oil and saliva on sperm motion in 16 samples from patients undergoing infertility investigations. Sperm samples were prepared by density gradient centrifugation prior to mixing with lubricants. Motility parameters were determined using computer-assisted semen analysis after 5, 15 and 30 min. All lubricants except baby oil significantly decreased percentage progressive motility, progressive velocity, curvilinear velocity and lateral head displacement at 12.5% concentration. At a lower concentration of 6.25%, both olive oil and saliva still significantly reduced progressive motility parameters, while KY jelly diminished head movement parameters. Hence, even at these very low concentrations, coital lubricants impair sperm motility and thus may adversely affect fertility.

Cellulose↗

PubMed2001

Gel lubrication of the tracheal tube cuff reduces pulmonary aspiration.

BACKGROUND: Leakage of fluid occurs along the longitudinal folds within the wall of an inflated high-volume, low-pressure cuff. Theoretically, lubrication of the cuff with a water-soluble gel might prevent aspiration by plugging the channels in the cuff wall. Pulmonary aspiration during anesthesia has been linked with postoperative pneumonia and during critical illness causes ventilator-associated pneumonia. METHODS: Lubricated cuffs were compared with nonlubricated cuffs for leakage of dye placed in the subglottic space to the tracheobronchial tree in a benchtop model (n = 5) and in a prospective double-blinded randomized controlled trial of anesthetized patients (n = 36). The duration of the efficacy of the lubricant was determined in a prospective open observational study of critically ill patients with tracheostomies (n = 9). Dye was detected clinically by dye coloration of secretions during tracheal suctioning. RESULTS: In the benchtop model the incidence of leakage was 0% in the lubrication group and 100% in the nonlubrication group (P < 0.01). Dye leakage in anesthetized patients was 11% in the lubrication group and 83% in the nonlubrication group (P < 0.0001). In the critically ill patients with lubricated cuffed tracheostomy tubes, leakage first occurred after a median period of 48 h (range, 24-120 h). CONCLUSIONS: Cuff lubrication with a water-soluble gel reduces pulmonary aspiration in anesthetized patients. In the critically ill patient with a tracheostomy the protective effect is lost after 24-120 h.

Adult↗

PubMed2005

Flammability of common ocular lubricants in an oxygen-rich environment.

PURPOSE: Approximately 100 surgical fires take place in the United States each year. Recently, an ophthalmic lubricant was blamed for burning a child's eye while oxygen was administered during surgery. This study sought to determine whether four common ocular lubricants would ignite and sustain combustion in an oxygen-rich or standard room air environment. METHODS: A model head was modified to allow placement of a cow eye and marked with 1-inch gradations from the eye. A nasal cannula supplied room air and 100% oxygen at flow rates of 0, 2, 4, and 6 L/minute. Four common ocular lubricants were chosen and placed on the eye before attempted ignition. The ignition source (an AccuTemp disposable electrocautery unit and unipolar and bipolar cautery set at 10, 20, and 30 watts) was brought down from the hairline toward the cannula. Each lubricant was tested with each ignition source and each room air/oxygen flow rate. RESULTS: None of the ocular lubricants ignited under any of the experimental environments tested. A small surface flame was noted with the AccuTemp electrocautery unit, but it did not create a flash fire during the experiment. CONCLUSIONS: The ocular lubricants in this experiment showed no detectable tendency to ignite, even with direct application of the ignition source. Factors such as body hair or oxygen pooling likely provided the conditions necessary for the surgical fire. Most importantly, the ophthalmic lubricants tested actually protected the corneal epithelium and decreased damage to the conjunctiva and lids.

Animals↗

PubMed2006

Impact of wearing an intra-oral lubricating device on oral health in dry mouth patients.

OBJECTIVE: To establish whether an intra-oral lubricating device for dry mouth alters the oral environment. DESIGN: A single-blind randomized cross-over study. METHOD: Twenty-nine dentate subjects from the Sjogren's syndrome clinic attended on five occasions at 4-week intervals. They were randomized, having the device fitted on either the second or the fourth visit for the experimental period, whilst using their preferred method of lubrication throughout the rest of the study. The preferred methods of lubrication were either water (group 1, n = 10) or saliva substitute (group 2, n = 9) or sugar-free chewing gum (group 3, n = 10). At each visit microbiological, unstimulated and stimulated saliva samples were collected. Dry mouth score, speech test and periodontal indices were recorded. RESULTS: The water lubrication group (1) had a resting salivary flow greater than lubrication groups (2 and 3) by post-ANOVA contrasts (P < 0.001). The postdevice data also demonstrated a salivary flow greater than lubrication group (3) by post-ANOVA contrasts (P < 0.05). The epithelial cell count using the Spearman correlation was high, possibly reflecting increased viscosity of the saliva (P = 0.044). The speech test indicated that the experimental subjects had difficulty in speaking (P = 0.001). This was slightly easier postdevice wear. Streptococcus mutans (P = 0.009) and Lactobacillus (P = 0.058) increased in the saliva after wearing the device. Salivary flow rate, Candida albicans, oral dryness, speaking and periodontal indices were unchanged. CONCLUSIONS: The oral environment was altered by wearing a lubricating device with an increase in the numbers of Strep. mutans and Lactobacillus. Clinical dryness and speech test correlated with the mean whole salivary flow suggesting a screening method for xerostomia.

Adult↗

PubMed2001

The effect of femoral head diameter upon lubrication and wear of metal-on-metal total hip replacements.

It has been found that a remarkable reduction in the wear of metal-on-metal hip joints can be achieved by simply increasing the diameter of the joint. A tribological evaluation of metal-on-metal joints of 16, 22.225, 28 and 36 mm diameter was conducted in 25 per cent bovine serum using a hip joint simulator. The joints were subject to dynamic motion and loading cycles simulating walking for both lubrication and wear studies. For each size of joint in the lubrication study, an electrical resistivity technique was used to detect the extent of surface separation through a complete walking cycle. Wear of each size of joint was measured gravimetrically in wear tests of at least 2 x 10(6) cycles duration. Joints of 16 and 22.225 mm diameter showed no surface separation in the lubrication study. This suggested that wear would be proportional to the sliding distance and hence joint size in this boundary lubrication regime. A 28 mm diameter joint showed only limited evidence of surface separation suggesting that these joints were operating in a mixed lubrication regime. A 36 mm diameter joint showed surface separation for considerable parts of each walking cycle and hence evidence of the formation of a protective lubricating film. Wear testing of 16 and 22.225 mm diameter metal-on-metal joints gave mean wear rates of 4.85 and 6.30 mm3/10(6) cycles respectively. The ratio of these wear rates, 0.77, is approximately the same as the joint diameters ratio, 16/22.225 or 0.72, as expected from simple wear theory for dry or boundary lubrication conditions. No bedding-in was observed with these smaller diameter joints. For the 28 mm diameter joint, from 0 to 2 x 10(6) cycles, the mean wear rate was 1.62 mm3/10(6) cycles as the joints bedded-in. Following bedding-in, from 2.0 x 10(6) to 4.7 x 10(6) cycles, the wear rate was 0.54 mm3/10(6) cycles. As reported previously by Goldsmith et al. in 2000 [1], the mean steady state wear rate of the 36 mm diameter joints was lower than those of all the other diameters at 0.07 mm3/10(6) cycles. For a range of joints of various diameters, subjected to identical test conditions, mean wear rates differed by almost two orders of magnitude. This study has demonstrated that the application of sound tribological principles to prosthetic design can reduce the wear of metal-on-metal joints, using currently available materials, to a negligible level.

Arthroplasty, Replacement, Hip↗

PubMed1993

Asperity lubrication in human joints.

The asperity lubrication in human joints is examined in the present paper, with particular reference to the tertiary undulation with wavelengths of around 20-45 microns. It was found that, under dynamic physiological loading conditions, the secondary waviness of the cartilaginous surface (typically 0.5 mm wavelength) could be effectively flattened to sustain a fluid film of 0.1-0.3 micron thick, while the tertiary waviness could be squashed to sustain a much thinner fluid film of 0.01 micron (10 nm) thick with normal synovial fluid as the lubricant. The calculated film thickness for the tertiary undulation was less than 5 nm when the ankle joint was lubricated by Ringer's solution or pathological synovial fluids, or when only quasi-static loading conditions were considered, while a sufficiently thick fluid film could still be formed when the secondary undulations were considered alone. It was thus suggested that the fluid film lubrication mechanism was operative for human joints with normal synovial fluid as the lubricant under physiological dynamic loading conditions and the mixed lubrication mechanism could take over when static loading conditions prevailed or when watery lubricants (eta approximately 0.001 Pa s) were used.

Ankle Joint↗

PubMed1999

The effect of phospholipase digestion upon the boundary lubricating ability of synovial fluid.

OBJECTIVE: To identify the boundary lubricant in synovial fluid (SF). Is synovial lubrication mediated by surface active phospholipid as opposed to mucinous glycoprotein? METHODS: A sonicated preparation of phosphatidylcholine and bovine SF were tested in vitro in a bearing of latex oscillating against polished glass under a load of 0.35 x 10(6) N/m2. The friction apparatus isolates conditions of boundary lubrication and has been validated against a cartilaginous bearing. Coefficient of friction (mu) was measured and compared against mu from physiologic saline, which served as a control. Separate digestions were carried out upon the SF with trypsin, phospholipase C, and phospholipase A2 in the presence and absence of proteolytic inhibitors. RESULTS: Digestions of bovine SF by phospholipase C in the presence of protease inhibitors did not remove boundary lubricating ability compared to an undigested control (p = 0.89). Digestion of bovine SF with trypsin removed all lubricating ability and raised friction (p = 0.004). Commercial purified phospholipase C contained trypsin-like activity when activity was tested with N alpha-benzoyl-L-arginine ethyl ester as substrate. Similar results were observed for phospholipase A2, which possesses a lower amount of trypsin activity. CONCLUSION: The results indicate that phospholipid does not play a prominent role in synovial fluid's ability to lubricate an artificial bearing. Rather, the boundary lubricating ability of SF is attributable to lubricin, a mucinous glycoprotein.

Animals↗

PubMed2004

Lubricating ability of aspirated synovial fluid from emergency department patients with knee joint synovitis.

OBJECTIVE: To determine if joint effusions encountered in the emergency department (ED) requiring arthrocentesis possess normal lubricating ability or evidence cartilage degeneration. Chondroprotection of articulating joint surfaces is provided by lubricin, a mucinous glycoprotein that is a product of megakaryocyte-stimulating factor gene (GenBank U70136) expression. Loss of synovial fluid's (SF) lubricating ability has been implicated in the pathogenesis of degenerative joint disease. METHODS: A retrospective ED observational study from May 1, 1999, to October 1, 2000, of adult and pediatric patients presenting with radiographically negative knee joint complaints and clinical evidence of joint effusion. Knee joints were aspirated by the emergency physician and the synovial fluid tested for lubricating ability and collagen type II degeneration. Lubricating ability was assayed in vitro in an arthrotripsometer oscillating latex apposed to polished glass under a load of 0.35 106 N/m2. Results were reported as the coefficient of friction ( micro ) relative to that of a 0.9% NaCl control; negative deltamicro value indicates lubrication. Comparisons of deltamicro were made to normal SF and aspirates from patients with osteoarthritis (OA) and rheumatoid arthritis. Collagen type II fragments were measured by a novel sandwich ELISA. RESULTS: Synovial fluid aliquots (n = 57) lubricated poorly with deltamicro = -0.045 (95% confidence interval = -0.006, -0.083) compared to normal SF with D micro = -0.095 (95% CI = -0.088, -0.101). Only 20.6% of knee joint aspirates possessed normal lubricating ability. An association exists between nucleated cell count and deltamicro described by a logarithmic function. Collagen type II fragments were present in aspirates at a concentration of 0.636 microg/ml (95% CI 0.495-0.777 microg/ml), significantly higher than 0.173 microg/ml (95% CI 0.154-0.193 microg/ml) in the OA comparison group. CONCLUSION: Knee joints with synovitis, commonly encountered in the ED, are frequently nonlubricated bearings and display catabolism of collagen type II. This may play a role in acute cartilage destruction ultimately resulting in posttraumatic OA.

Adolescent↗

PubMed1995

Mechanical test method on the estimation of the lubricant performance by hyaluronic acid.

Cases with loss of articular cartilage or lowering of articular lubricant performance are frequent among patients afflicted by various gonarthropathies or those fitted with prosthetic joints. The management of such cases has necessitated evaluation studies on the clinical efficacy of using high molecular weight hyaluronic acid as an artificial synovial fluid with a view to improving articular lubricant performance. The proper implementation of such evaluation studies on lubrication performance requires testing methods capable of assessing basic lubricant performance not only with respect to articular cartilage alone but also with respect to various other combinations of materials, i.e., lubrication between articular bone and artificial joints, etc. In the present study, first, a simple standard lubricant performance test using several small readily procurable test specimens was devised. Then, this test was employed to evaluate the basic lubricant properties of hyaluronic acid intended for use as artificial synovial fluid.

Aged↗

PubMed1999

Environmentally friendly lubricating oil candidate.

Synthetic lubricating oils based on renewable sources, excluding petroleum, have a great importance among all of the lubricating oil alternatives that are included in the research field about clean and environmentally friendly lubricating oil technologies. One of the environmentally friendly lubricating oils is a vegetable oil-based product. In this study, the esterification product of oleic acid with a fraction of molasses fusel oil as a lubricating oil candidate was determined according to the American Society for Testing and Materials (ASTM) standard tests. The results indicate that the ester product can be used as an environmental friendly lubricating oil or lubricating oil additive.

Alcohols↗

PubMed2006

Application of two-dimensional spectral surface plasmon resonance to imaging of pressure distribution in elastohydrodynamic lubricant films.

What we believe to be a novel two-dimensional spectral surface plasmon resonance imaging technique determining pressure distribution in elastohydrodynamic lubricant films is presented. This technique makes use of the spectral characteristics associated with the surface plasmon resonance (SPR) effect, and it provides more spectral information in refractive index mapping than conventional contrast SPR imaging. Two-dimensional imaging is demonstrated and applied to a highly pressurized liquid lubricant trapped inside an elastohydrodynamic lubrication (EHL) dimple. The hydrostatic pressure inside the EHL dimple causes a localized change of the refractive index of the lubrication oil. This also results in a shift in the spectral SPR absorption dip. By monitoring the color changes within the SPR image and calibrating with lubricants of known refractive index profiles, we can obtain a direct measurement of the refractive index distribution within the EHL dimple. PB 2400 lubricant dimples were studied in our experiments. The proposed SPR imaging approach is irrespective of the absolute lubricant film thickness h, therefore overcoming the major limitations of a conventional optical interference technique. With further development of the two-dimensional refractive index mapping technique, widespread applications in various fields are possible, including high-throughput sensors and the detection of bioaffinity interactions.

Journal Article↗

PubMed1996

Does additional lubrication reduce condom failure?

It has been suggested that using additional spermicide with condoms provides added contraceptive effect and protection from infection, and that water-based lubricants may lower condom breakage rates. This questionnaire-based study investigated the use of additional lubrication with condoms amongst 525 female students presenting for post-coital contraception, and the current and past experience of condom and additional lubrication use amongst 481 controls attending the same health centre. Of those requesting post-coital contraception, 83% claimed condom failure as the cause, with 66% of the control group having also experienced condom failure at some time. Use of additional water-based lubrication was significantly associated with lower condom failure rates (odds ratio 8.88, 95% C.I.: 3.79, 20.8). Gender, regularity of use of condoms and using oil-based lubricants were not associated with higher failure rates. Additional lubricant use was not significantly associated with increased condom slippage.

Condoms↗

PubMed1981

The lubricating activity of synovial fluid glycoproteins.

Friction measurements were performed on fractions prepared from bovine synovial fluid by using a cartilage on glass apparatus. A fraction containing lubricating glycoprotein-I (LGP-I) as the only detectable component at concentrations of 30-50 microgram/ml was able to lubricate in an identical manner to whole synovial fluid. These data indicate that LGP-I is th molecule responsible for the lubricating ability of synovial fluid. 125Iodine-labeled LGP-I also lubricated in a manner similar to synovial fluid, whereas when this sample was reduced and alkylated or treated with neuraminidase, the lubricating activity was greatly decreased. In tests to measure binding of 125I LGP-I to cartilage, an initial linear increase in binding was observed, followed by a decrease in binding at higher concentrations. In contrast, both the reduced and alkylated and the neuraminidase treated samples did not show the same concentration-dependent binding to the cartilage. It is suggested, therefore, that at least part of the lubricating ability of LGP-I is dependent upon its ability to bind to articular cartilage.

Amino Acids↗

PubMed1994

Biomaterials lubricated for minimum frictional resistance.

To improve the frictional characteristics of a biomaterial, the mechanical performance of a lubricated surface was studied. In vitro friction tests showed that the coefficient of dynamic friction of the lubricated surface was about 0.01 against rabbit bladder and the coefficient of static friction increased with the preload period. The efficacy of a lubricated cystoscope was evaluated by an in vivo test simulating cystoscope operation. The maximal and the total resistance force on the cystoscope model were found to decrease with the surface lubrication. Histological study revealed that urethral damage caused by rubbing with the cystoscope model was reduced by this lubrication technique. Presumably, prolonged retention of water on the lubricated surface region prevented tissue adhesion to the foreign material.

Animals↗