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PubMedDate not supplied

On a possible connection between deficiency of cervical and Bartholin secretion, the use of vaginal lubricants and the incidence of Down's anomaly.

The rate of mongolism is well known to increase with maternal age and has been suggested by German to be connected with the frequency of intercourse. The occurrence is discussed in relation to the possible use of vaginal lubricants as a consequence of deficient cervical and Bartholin secretion. The implications of this idea are discussed.

Bartholin's Glands↗

PubMed2005

Lubricant and razor debridement in partial thickness burn.

By aiming to relieve pain from removing blisters in partial thickness burn, we tested whether the application of a sterile lubricant (KY-Jelly) on blisters and the use of a sterile razor to remove their roof can reduce algesia in humans, compared to a conventional method. A prospective randomized controlled designed study was performed on 20 patients. A visual pain scale was used by patients to evaluate pain experienced.

Adult↗

PubMed2006

Nanotechnology in action: overbased nanodetergents as lubricant oil additives.

The synthesis and study of oil-soluble metal carbonate colloids are of interest in the area of lubricant additives. These surfactant-stabilised nanoparticles are important components in marine and automotive engine oils. Recently introduced, environmentally driven legislation has focused on lowering of gaseous emissions by placing limits on the levels of phosphorous sulphur and ash allowed in engine oil systems. These chemical limits, coupled with improved engine performance and extended oil drainage intervals, have lead to renewed interest in the production of stable, efficient nanodetergent systems. To date, this has resulted in modification of existing surfactant structures and development of new generations of surfactants. This review covers the current state of research in the area of nanodetergents.

Journal Article↗

PubMed2004

Bioadhesive, rheological, lubricant and other aspects of an oral gel formulation intended for the treatment of xerostomia.

Xerostomia is commonly known as 'dry mouth' and is characterised by a reduction or loss in salivary production. A bioadhesive gel for its localised treatment was formulated to help enhance the residence time of the product, based on the polymer Carbopol 974P. The bioadhesion of various formulations was evaluated on different mucosal substrates, as simulations of the oral mucosa of xerostomic patients. Depending on the type of model substrate used, the mechanism of bioadhesion could alter. When the rheology of various formulations was examined, changes in bioadhesion were more easily interpreted, as the presence of other excipients caused an alteration in the rheological profile, with a change from a fully expanded and partially cross-linked system to an entangled system. Improving the lubricity of the product was considered important, with optimum incorporation of vegetable oil causing a desirable lowering of the observed friction of the product. The final complex formulation developed also contained salivary levels of electrolytes to help remineralisation of teeth, fluoride to prevent caries, zinc to enhance taste sensation, triclosan as the main anti-microbial/anti-inflammatory agent and non-cariogenic sweeteners with lemon flavour to increase the palatability of the product while stimulating any residual salivary function.

Acrylates↗

PubMed2002

The influence of the acetabular labrum seal, intact articular superficial zone and synovial fluid thixotropy on squeeze-film lubrication of a spherical synovial joint.

A model of synovial fluid (SF) filtration by articular cartilage (AC) in a step-loaded spherical synovial joint at rest is presented. The effects of joint pathology (such as a depleted acetabular labrum, a depleted cartilage superficial zone consistent with early osteoarthritis and an inflammatory SF) on the squeezed synovial film are also investigated. Biphasic mixture models for AC (ideal fluid and elastic porous transversely isotropic two-layer matrix) and for SF (ideal and thixotropic fluids) are applied and the following results are obtained. If the acetabular labrum is able to seal the pressurised SF between the articular surfaces (as in the normal hip joint), the fluid in the synovial film and in the cartilage within the labral ring is homogeneously pressurised. The articular surfaces remain separated by a fluid film for minutes. If the labrum is destroyed or absent and the SF can escape across the contact edge, the fluid pressure is non-homogeneous and with a small jump at the articular surface at the very moment of load application. The ensuing synovial film filtration by porous cartilage is lower for the normal cartilage (with the intact superficial zone) than if this zone is already depleted or rubbed off as in the early stage of primary osteoarthritis. Compared with the inflammatory (Newtonian) SF, the normal (thixotropic) fluid applies favourably in the squeezed film near the contact centre only, yielding a thicker SF film there, but not affecting the minimum thickness in the fluid film profile at a fixed time. For all that, in the unsealed case for both the normal and pathological joint, the macromolecular concentration of the hyaluronic acid-protein complex in the synovial film quickly increases due to the filtration in the greater part of the contact. A stable synovial gel film, thick on the order of 10(-7)m, protecting the articular surfaces from the intimate contact, is formed within a couple of seconds. Boundary lubrication by the synovial gel is established if sliding motion follows until a fresh SF is entrained into the contact. This theoretical prediction is open for experimental verifications.

Acetabulum↗

PubMed1999

Lubrication of the human ankle joint in walking with the synovial fluid filtrated by the cartilage with the surface zone worn out: steady pure sliding motion.

A mixture model of synovial fluid filtration by cartilage in the human ankle joint during walking is presented for steady sliding motion of the articular surfaces. In the paper the cartilage surface zone is assumed worn out. The same model has been recently applied to the squeeze-film problem for the human hip joint loaded by the body weight during standing (Hlavácek, Journal of Biomechanics 26, 1145-1150, 1151-1160, 1993; Hlavácek and Novák, Journal of Biomechanics 28, 1193-1198, 1199-1205, 1995). The linear biphasic model for cartilage (elastic porous matrix + ideal fluid) due to Prof. V. C. Mow and his co-workers and the biphasic model for synovial fluid (viscous fluid + ideal fluid), as used in the above-mentioned squeeze-film problem, are applied. For the physiologic parameters of the ankle joint during walking, a continuous synovial fluid film about 1 microm thick is maintained under steady entraining motion according to the classical model without the fluid transport across the articular surface. This is not the case in the filtration model with the cartilage surface zones worn out. On the contrary, this filtration model indicates that synovial fluid is intensively filtrated by such cartilage, so that no continuous fluid film is maintained and a synovial gel layer, about 10(-8) m thick, develops over the majority of the contact. Thus, if the cartilage surface zones are worn out, boundary lubrication should prevail in the ankle joint under steady sliding motion for the mean values of loading and the sliding velocity encountered in walking cycle.

Ankle Joint↗

PubMedDate not supplied

Reduction in snoring with phosphocholinamin, a long-acting tissue-lubricating agent.

The efficacy of a long-acting lubricating and coating agent, phosphocholinamin, in reducing snoring was tested in 12 persons, six of whom received the agent as nose drops and six of whom received a placebo (tap water nose drops). In all subjects, the noise level was measured continuously by using a microphone taped near the cricothyroid notch. In the group treated with phosphocholinamin, the maximum nocturnal decibel level was reduced by a mean +/- SD of 13 +/- 3%, and the snoring index (defined as the number of snores per hour of sleep) was reduced by 25 +/- 12%. In the group treated with placebo, the maximum nocturnal decibel level increased 9 +/- 22% and the snoring index increased 1 +/- 20%. The differences between the two groups were statistically significant (P less than .05). It is concluded that phosphocholinamin can provide a useful medical alternative in the treatment of snoring and that further trials of this agent are indicated.

Administration, Intranasal↗

PubMedDate not supplied

Conjugation of Cu,Zn-superoxide dismutase with succinylated gelatin: pharmacological activity and cell-lubricating function.

Superoxide dismutase (SOD) and succinylated gelatin (succinyl gelatin) were conjugated to improve in vivo pharmacological activity of SOD. Lysyl residues of human recombinant Cu,Zn-SOD were cross-linked with carboxyl residues of succinyl gelatin using 1-ethyl-3-[3- (dimethylamino)propyl]carbodiimide. Various chemical and pharmacokinetic parameters of the conjugate were determined. Analysis by atomic absorption spectrometry and amino acid composition revealed that the conjugate was composed of about 2.9 mol of succinyl gelatin (with a mean molecular weight of 23,000) to 1 mol of SOD and exhibited an apparent mean molecular weight of 98,000. The conjugate retained almost 100% of its original activity on a molar basis. When the succinyl gelatin-conjugated Cu,Zn-SOD (Suc-gel-SOD) was administered intravenously to mice, its plasma half-life was prolonged to 29.7 min compared with 4.5 min for native SOD. Tissue distribution analysis revealed that intravenously administered Suc-gel-SOD showed a much greater accumulation than native SOD in the liver followed by in decreasing order the kidney, the lung, and the spleen; native SOD was excreted more rapidly into urine before it accumulated in tissues. Furthermore, Suc-gel-SOD exhibited lower antigenicity and immunogenicity than native SOD, and it had a better therapeutic effect against ischemic edema of the foot pad in mice. The conjugate was found to accumulate more than native SOD in the ischemic foot pad. A newly added property of the conjugate is cell-lubricating activity, which facilitated cell passage through micropores and reduced hemolysis during cell passage in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2004

Phosphazene-based ionic liquids: synthesis, temperature-dependent viscosity, and effect as additives in water lubrication of silicon nitride ceramics.

Phosphazene rings with (dimethylamino)ethoxy (1, 2), pyridylmethoxy (3), or (dimethylamino)propoxy (4) chains were synthesized and quaternized at the substitutent nitrogen by treatment with methyl iodide at 35 degrees C over 3-6 h to give polyiodo salts, 5-8. Subsequent metathesis with LiN(SO(2)CF(3))(2) or NaBF(4) gave the respective ionic salts, 9-13. The amide salts, 9-12, were viscous liquids with pour points at 55-100 degrees C, and the tetrafluoroborate salt, 13, was a solid, mp 168 degrees C. The compositions of 2 and 5-13 were confirmed by elemental analysis and spectroscopic methods. Compounds 1, 2, and 4 were viscous liquids (d(25) = 1.67 g cm(-3); eta(25) = 0.76-1.56 mPa s(-1) ) with pour points at approximately 15 degrees C. The solid polyquaternary salts, 5-8, melted at 130-194 degrees C. The ionic liquids, 9-12, had an average density of approximately 1.73 g cm(-3) at 25 degrees C, and viscosities (25 degrees C) ranged between 68.3 and 139.2 mPa s(-1). A plot of the viscosities of 9-12 vs temperature revealed an almost linear correlation between 55 and 120 degrees C. Friction and wear properties of water with 0.25 wt % of 9-12 as boundary lubricant additives were evaluated on Si(3)N(4)/Si(3)N(4) ceramic interfaces. The most significant observation is that they caused a decrease in the running-in period.

Journal Article↗

PubMed2005

Enhanced lubricity in mixed alkanethiol monolayers.

The frictional properties of two-component mixed alkanethiol monolayers were investigated with frictional force microscopy. With large chain length differences, the two types of molecules segregated into large islands and reveal similar frictional properties as those of single-component monolayers. With small chain length differences, the completely mixed monolayers display a decreased friction as compared with single-component monolayers. This observation indicates that development of gauche kinks in the top portion of the mixed monolayers can enhance lubrication rather than increase friction, perhaps due to suppression of other energy dissipation channels.

Journal Article↗

PubMed2006

Tribochemical reaction dynamics of phosphoric ester lubricant additive by using a hybrid tight-binding quantum chemical molecular dynamics method.

To study the atomistic behavior of the phosphoric ester molecule on the nascent Fe surface under boundary lubrication conditions, we adopted a hybrid tight-binding quantum chemical molecular dynamics method. First, we investigated chemical interactions between phosphoric ester and the nascent Fe surface. Phosphoric ester was shown to interact with the nascent Fe surface, forming both covalent and ionic bonds. Formation and dissociation dynamics of covalent bonds during tribochemical reaction was clearly observed during the simulation. The effect of friction condition on the tribochemical reaction dynamics was then studied, and it was indicated that friction would influence the formation and the dissociation of covalent bonds. By using a hybrid tight-binding quantum chemical molecular dynamics method, we obtained insights on initial tribochemical reaction processes for the formation of tribofilm from the phosphoric ester molecule on the nascent Fe surface.

Journal Article↗

PubMed2004

Autophobic dewetting of Z-tetraol perfluoropolyether lubricant films on the amorphous nitrogenated carbon surface.

The thermodynamic stability of thin films of the perfluoropolyether (PFPE) Z-Tetraol, as a function of molecular weight, on amorphous nitrogenated carbon, CNx, is investigated. An optical surface analyzer is used to image the autophobic dewetting of the Z-Tetraol films. Film dewetting results when the PFPE film thickness applied to the CNx surface exceeds a critical value. This critical dewetting thickness is identified as the monolayer thickness of the adsorbed PFPE film via measurements of the changes in the surface energy as a function of lubricant film thickness. The observed dewetting coincides with the film thickness at which the disjoining pressure goes to zero. The critical dewetting thickness is dependent on the PFPE molecular weight.

Journal Article↗

PubMed2005

Surfactant boundary lubricant film modified by an amphiphilic diblock copolymer.

The effect of the uptake of a low-molecular-weight amphiphilic diblock copolymer on the morphology of didodecyldimethylammonium bromide (DDAB) adsorbed layers on mica, the interactions between two coated surfaces, and the frictional properties of the boundary film have been studied using an atomic force microscope and a dynamic surface forces apparatus nanotribometer. When DDAB-coated surfaces in aqueous solution were compressed, hemifusion or removal of the adsorbed surfactant bilayers could not be induced, and no frictional force could be measured between the surfaces, which display superior lateral cohesion and lubricant properties. Coadsorbing octadecyl end modified poly(ethylene oxide) chains at low density facilitates hemifusion, generating significant shear stress and leading to stick-slip instabilities. The mixed films regain their lateral cohesion at higher adsorbed copolymer densities, but an extra short-range attraction brings the adsorbed layers into adhesive contact without causing bilayer hemifusion. Here, noticeable frictional forces are also measured.

Journal Article↗

PubMed2006

Lubrication theory of drag on a scanning probe in structured water, near a hydrophilic surface.

The drag is evaluated, in lubrication theory, on a parabolic-cylindrical tip moving parallel to a flat sample, in water, close enough that the presumed nanometer-thick, structured-water, "interphase" coatings of both it and the sample overlap. Assuming coatings of width, w, and of viscosity, eta, much larger than bulk water's, the friction force is predicted to equal -2pietacRphi(D/2w), where R is the tip's radius of curvature, c is its speed, D is the tip-sample separation, and Phi is a universal function whose value only differs noticeably from ln(2w/D) for D < w.

Journal Article↗

PubMed2006

STM, QCM, and the windshield wiper effect: a joint theoretical-experimental study of adsorbate mobility and lubrication at high sliding rates.

We have observed that when mobile adsorbed films of benzene, tricresyl phosphate, and tertiary-butyl phenyl phosphate are present on the surface electrode of a quartz crystal microbalance (QCM), oscillation of the QCM produces clearer scanning tunneling microscope (STM) images of the electrode surface. This is in contrast to an immobile overlayer of iodobenzene, where oscillation of the QCM does not affect image quality. This observation is attributed to a "windshield wiper effect", where at MHz frequencies the tip motion maintains a region of the surface where the absorbate concentration is reduced, which leads to a clearer image. A straightforward model is presented that supports this conclusion and that provides guidelines for effective lubrication of contacts operating at MHz frequencies.

Journal Article↗

PubMed2001

Room-temperature ionic liquids: a novel versatile lubricant.

Alkylimidazolium tetrafluoroborates are promising versatile lubricants for the contact of steel/steel, steel/aluminium, steel/copper, steel/SiO2, Si3N4/SiO2, steel/Si(100), steel/sialon ceramics and Si3N4/sialon ceramics; they show excellent friction reduction, antiwear performance and high load-carrying capacity.

Journal Article↗

PubMed1977

The isolation and partial characterization of the major glycoprotein (LGP-I) from the articular lubricating fraction from bovine synovial fluid.

The articular lubricating fraction from bovine synovial fluid was prepared by repeated fractionation in three consecutive CsCl density gradients to remove completely traces of hyaluronic acid. The major glycoprotein consituent (LGP-I) was then isolated by repeated gel-permeation chromatography. The yield of the LGP-I component was about 20 mg/litre of synovial fluid. Sedimentation-equilibrium measurements showed that this glycoprotein was homogeneous and the mol.wt. was calculated to be 227500. Amino acids represented 43% (w/w) and carbohydrate constituents 44% (w/w) of the molecule. Threonine, glutamic acid, proline and lysine (224, 127, 242 and 128 residues/1000 residues respectively) were the major amino acids. Galactosamine, galactose and N-acetylneuraminic acid (202, 162 and 114 residues/molecule of LGP-I component respectively) accounted for 98% of the total carbohydrate residues present. Small amounts of mannose and glucosamine (1 and 9mol respectively/mol of LGP-I component) were also present. After treatment of LGP-I component with alkali and NaB3H4 radioactivity was incorporated into alpha-aminobutyric acid and alanine in a molar ratio of 4:1, and radioactive galactosaminitol was isolated by ion-exchange chromatography from a cleaved oligosaccharide fraction. These data demonstrate the presence of threonine and serine -O-GalNAc linkages, but only 25% of the theoretical likages involving threonine were cleaved by a beta-elimination reaction. Digestion of LGP-I component with Pronase followed by chromatography on DEAE-cellulose yielded glycopeptide fractions with a similar amino acid and carbohydrate composition to the intact molecule. Treatment of desialylated and intact LGP-I component with galactose oxidase followed by reduction with NaB3H4 revealed the presence of 52mol of terminal galactose in the intact molecule and 153mol of galactose/mol of LGP-I component after treatment with neuraminidase. The data indicate the LGP-I component is composed of a single polypeptide chain containg more than 150 oligaosaccharide side chains composed of O-GaINAc-Gal distributed over the length of the peptide chain and that terminal sialic acid residues are linked to galactose in two-thirds of these side chains.

Amino Acids↗

PubMed1979

The isolation and properties of a second glycoprotein (LGP-II) from the articular lubricating fraction from bovine synovial fluid.

A high-molecular-weight glycoprotein (LGP-I) was shown [Swann, Sotman, Dixon & Brooks (1977) Biochem. J. 161, 473--485] to be the major constituent in the articular lubricating fraction from bovine synovial fluid. In addition to the LGP-I component, a second glycoprotein (LGP-II) was also present. After fractionation of bovine synovial fluid by sequential sedimentation in CsCl density gradients, the LGP-I and LGP-II components were separated by gel-permeation chromatography. The LGP-II component was then purified by chromatography on DEAE Bio-Gel A and Bio-Gel P-150. The molecular weight of the LGP-II component was 48,800 calculated from sedimentation-equilibrium measurements. Amino acids represented 53% (w/w) and carbohydrate constituents 36% (w/w) of the molecule. Glutamic acid and lysine (144 and 100 residues/1000 residues) were the major amino acids. Glucosamine, mannose, galactose and N-acetylneuraminic acid [representing 8.0, 6.6, 9.5 and 11.9% (w/w) respectively] were the only carbohydrate constituents detected. Immunodiffusion analysis showed that LGP-II component did not form a detectable precipitin line with antiserum to bovine serum. It appears likely, therefore, that this glycoprotein is synthesized by the joint tissues and is not derived from serum.

Amino Acids↗