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At least 19 recordsLinked to original sources
PubMed1977

Mechanism of surface lubrication: influence of duration of lubricant-excipient mixing on processing characteristics of powders and properties of compressed tablets.

A mathematical expression for tablet hardness was related to lubricant mixing by considering increases in the surface coverage with prolonged mixing time. The duration of lubricant mixing significantly changed the apparent bulk volume of the mix, ejection force during tableting, hardness, and disintegration and dissolution properties of tablets. These findings may provide some rationale for the changes in processing characteristics and properties of finished drug products often encountered in the scale-up of solid dosage formulations. Several lubrication mechanisms are discussed in connection with the duration of mixing effects and scanning microscopy studies.

Drug Compounding↗
PubMed1975

Influence of stone mixing agents, impression materials and lubricants on surface hardness and dimension of a dental stone die material.

The influence of different stone mixing agents, impression materials and lubrication methods on the surface hardness of a stone die material has been evaluated. For one impression material the dimensional effect of the mixing agents and lubrication on the dies was also studied. The stone die material was mixed with water or a gypsum hardener and allowed to set on surfaces of glass, agar-agar, polyether, polysulfide and silicone impression materials. The lubrication methods for the stone were mineral oil, water soluble lubricant and mineral oil followed by water soluble lubricant. The surface hardness was measured according to the Brinell test. The Brinell test was chosen after a comparative study of the Brinell, Vickers and Knoop hardness test methods. The results showed that gypsum hardener was preferable to distilled water. The impression materials appear to have influence on the surface hardness of stone. The effect differed on water mixed and hardener mixed stone which emphasizes the importance of the mixing agent. All lubrication decreased the surface hardness of stone. With hardener mixed stone the combination of mineral oil followed by water soluble lubricant seemed preferable. Neither the gypsum hardener nor the lubrication influenced the dimension of the stone die material.

Dental Impression Materials↗
PubMed1976

Lubrication and cartilage.

Mechanisms of lubrication of human synovial joints have been analysed in terms of the operating conditions of the joint, the synovial fluid and articular cartilage. In the hip and knee during a walking cycle the load may rise up to four times body weight. In the knee on dropping one metre the load may go up to 25 time body weight. The elastic modulus of cartilage is similar to that of the synthetic rubber of a car tyre. The cartilage surface is rough and in elderly specimens the centre line average is 2-75 mum. The friction force generated in reciprocating tests shows that both cartilage and synovial fluid are important in lubrication. The viscosity-shear rate relationships of normal synovial fluid show that it is non-Newtonian. Osteoarthrosic fluid is less so and rheumatoid fluid is more nearly Newtonian. Experiments with hip joints in a pendulum machine show that fluid film lubrication obtains at some phases of joint action. Boundary lubrication prevails under certain conditions and has been examined with a reciprocating friction machine. Digestion of hyaluronate does not alter the boundary lubrication, but trypsin digestion does. Surface active substances (lauryl sulphate and cetyl 3-ammonium bromide) give a lubricating ability similar to that of synovial fluid. The effectiveness of the two substances varies with pH.

Cartilage, Articular↗
PubMedDate not supplied

Boundary lubricating ability of synovial fluid in degenerative joint disease.

The boundary lubricating ability of eleven synovial fluids was measured in a miniaturized latex--glass test system. The specimens were obtained at necropsy from knees in which the degree of degenerative joint disease varied from none to very severe. The lubricating ability of the fluid was independent of the viscosity over a wide range of shear rates. It was not diminished even in advanced lesions. In two additional fluids, the mucin clot was poor; the lubricating ability of one of these was compromised. Thus, although degenerative joint disease, during its quiescent stages, is not associated with defective synovial lubrication, the possibility that transient defects might lead to cartilage wear during life has not been excluded. The measurements are believed to be valid indicators of boundary lubricating ability under physiological conditions despite the fact that the test surfaces were not cartilaginous and the loading was relatively low (up to 47 pounds per square inch).

Adult↗
PubMed1975

Demonstration of boundary lubrication by synovial fluid.

An account is given of an oscillatory rotating friction measurement apparatus which can be used for demonstration of boundary lubrication by synovial fluid when rubber and glass are employed as rubbing surfaces. A technical description of the apparatus is given. The greatest importance is placed on getting the apparatus to demonstrate reproducible results when saline and normal bovine synovial fluid are used as lubricant. The greatest variations are caused by differences in the cleaning of the rubber and in its tension. On the basis of bovine synovial fluid from ten different hock joints investigations were made of individual variations and changes occurring during storage at 4 degrees C. The individual variations were found to be of no importance; a decrease in the lubricating effect was observed only after storage for two months. Addition of trypsin confirmed that boundary lubrication by synovial fluid can be related to the protein component. The conclusion is that the apparatus is considered suitable for clinical investigations of boundary lubrication in connection with different joint diseases.

Animals↗
PubMed1976

The effect of vaginal lubricants on Neisseria gonorrhoeae.

The possible interference of vaginal lubricants in culture diagnosis of gonorrhea was investigated by studying in vitro effect of selected lubricants on Neisseria gonorrhoeae. Two lubricants widely used in family planning and other clinics were demonstrated to have a bactericidal effect on N. gonorrhoeae when tested with more than one method. Gonococci were killed on contact with Lubrifoam, even at a 10 per cent concentration, and an exposure time as short as one minute was sufficient to inhibit the growth on chocolate agar medium. The K-Y jelly showed less inhibitory effect than Lubrifoam. These findings suggest that certain vaginal lubricants have bactericidal effects and their presence can inhibit the growth of Neisseria gonorrhoeae.

Neisseria gonorrhoeae↗
PubMed1992

Characterization of a bovine synovial fluid lubricating factor. III. The interaction with hyaluronic acid.

Although hyaluronate is not a boundary lubricant in cartilaginous and latex:glass bearings, a distinct interaction with purified synovial lubricating factor (PSLF) was demonstrated by three means: 1) enhancement of lubricating ability in an artificial test system; 2) viscometry; 3) electron microscopy. The interaction was of a physical rather than a specific chemical type; it varied with the degree of purification of PSLF and of hyaluronate. The interaction accounts for retention of the relatively small PSLF molecule (approximately 280 kDa) with the synovial mucin on a 0.22 microns filter. The data provide evidence that hyaluronate and PSLF act synergistically in the boundary lubricating activity of animal joints.

Animals↗
PubMed1976

Pathological human synovial fluids. Viscosity and boundary lubricating properties.

On human synovial fluids obtained during operations from the knee joints of 80 patients with different joing disease, relative viscosity was measured at 3 different shear rates and the boundary lubrication was tested by the coefficient of friction in an artificial rubber/glass system. The results were evaluated in relation to the operative findings. The viscosity showed statistically significant differences between the synovial fluids from the knee joints with rheumatoid arthritis, osteoarthritis, and torn menisci, being lowest in rheumatoid synovial fluid and highest in synovial fluids from knee joints with torn menisci. Correlations were found in the variations in the viscosity and the degree of synovitis. The boundary lubrication also showed different values inrelation to the different diseases. Synovial fluid from knee joints with torn menisci seemed to act as the best lubricant and significantly better than rheumatoid synovial fluid. Variations in the boundary lubrications reflect successive degrees of cartilage degeneration.

Arthritis, Rheumatoid↗
PubMed1976

Comparative evaluation of tablet lubricants: effect of application method on tablet hardness and ejectability after compression.

The effect of four lubricants (stearic acid, magnesium stearate, calcium stearate, and talc) on the ejectability and hardness of statically compressed tablets of a lactose granulation was examined. Two methods of application of these lubricants, incorporation into the granulation and mixing with the granulation, were compared. In both methods, the energy consumption curves during ejection and the hardness curves with lubricant concentration were similar and showed complicated behavior at a lower concentration. The mixing method gave better results for ejectability and hardness than the incorporation method.

Drug Compounding↗
PubMed1975

The effect of vaginal lubricants on sperm motility in vitro.

Apart from the documentation of the spermicidal effects of KY Jelly and Surgilube, little information about the effect of vaginal lubricants on sperm motility has been available. Fifteen substances utilizable as vaginal lubricants were therefore tested for their effect on sperm motility in vitro. Petroleum jelly and glycerin had minimal detrimental effects on motility and apparently are the lubricants of choice when an infertility problem exists.

Contraceptive Agents, Female↗
PubMed1975

Some new evidence on human joint lubrication.

Theoretical consideration has been given to the use of pendulum machines which are used to examine the frictional properties of human joints by incorporating them as fulcra. As a result, a new type of pendulum machine has been built which incorporates the facility to apply sudden loads to the joint on starting the swinging motion, and also the ability to measure directly the frictional torque experienced by the joint. The results obtained from natural hip joints indicate the presence of squeeze film lubrication under conditions of sudden loading of a joint. In addition, a self-generated fluid film process was observed at low loads while at higher loads boundary lubrication appeared to be important. These results have been used to describe the lubrication regimens occurring in a normal activity such as walking. A single experiment carried out on a hip from a patient suffering from severe rheumatoid arthritis has also been reported and the frictional resistance was seen to be increased fifteenfold compared to a normal hip.

Arthritis, Rheumatoid↗
PubMed1979

The in vitro and in vivo effects of a surgical lubricant on the recovery of gonococci from the endocervical canal.

A surgical lubricant containing phenylmercuric borate, tested in vitro, was shown to alter the recovery of the gonococcus. In vivo studies of 150 patients, 60 (40%) of whom were infected with Neisseria gonorrhoeae, were performed to determine if examination with the surgical lubricant, as compared to tap water, altered the ability to recover N. gonorrhoeae from the cervix. Results indicated that although the surgical lubricant containing phenylmercuric borate was bacteriostatic in vitro, it did not alter the recovery of N. gonorrhoese from infected patients.

Adolescent↗
PubMed1975

Investigation of some materials as dry binders for direct compression in tablet manufacture. Part 5: Effects of lubricants and flow conditions.

The effect of talc, magnesium stearate, stearic acid, and Acrawax C, which are commonly used as lubricants, on the dry-binding efficiency of tragacanth, polyethylene glycol 4000, polyvinylpyrrolidone, and mannitol were investigated. The effect of Aerosil which is sometimes utilized as a flow conditioner for directly compressible powder blends was also studied. The type and concentration of lubricant or flow conditioner appeared to influence the binding efficiency of the binders investigated to various degrees. The results showed that the bonding characteristics of all the binders tested except mannitol were reduced by the addition of the lubricants and the flow conditioner.

Chemistry, Pharmaceutical↗
PubMed1977

Effect of shear mixing on in vitro drug release of capsule formulations containing lubricants.

The influence of shear mixing on the in vitro dissolution properties of several experimental capsule formulations containing lubricants was investigated. The studies were carried out in 2.8-liter laboratory V-blender equipped with a high-speed intensifier bar, using nitrofurantoin and procainamide hydrochloride as active drugs, powdered lactose and starch as excipients, and magnesium stearate and magnesium lauryl sulfate as lubricants. These studies revealed a pronounced inhibitory effect on drug dissolution due to shear in powder mixtures containing magnesium stearate; even at the maximum lubricant level of only 2%, high mixing markedly altered the in vitro dissolution rate. In systems with magnesium lauryl sulfate, the shear effect was less pronounced (nitrofurantoin blends) or absent (procainamide hydrochloride blends). The poor dissolution characteristics noted with magnesium stearate--shear combinations seem to result from the formation of a hydrophobic film around the powder mass, preventing wetting and deaggregation.

Capsules↗
PubMed1977

The adhesion of film coatings to tablet surfaces--the effect of some direct compression excipients and lubricants.

The effect of some direct compression excipients and lubricants on the adhesion of hydroxypropyl methyl cellulose films has been examined using a specially designed tensile testing apparatus (Fisher & Rowe, 1976). The adhesion was found to be influenced by both the roughness, including microporosity, of the tablet surface and its polarity. Tablets prepared from microcrystalline cellulose showed very high adhesions despite having relatively smooth surfaces, owing to the surface being saturated with hydroxyl groups able to form hydrogen bonds with the corresponding groups on the polymer. The addition of magnesium or calcium stearate to the tablet was found to decrease the adhesion, but the addition of stearic acid caused a significant increase. The effect of lubricant concentration on the adhesion could be expressed by an equation similar to that proposed by Hofrichter & McLaren (1948) for the adhesion of vinyl chloride/vinyl acetate copolymers to regenerated cellulose.

Adhesiveness↗
PubMed1977

[The significance of the characteristics of lubricating jellies in use during transurethral prostate resections with metallic sheaths (author's transl)].

If a metallic sheath is used during a transurethral resection of the prostate with high-frequency currents, the lubricating jelly has to exceed a prescribed conductivity, in order to prevent dangerous current-density spots within the urethra. Furthermore, the mechanical behaviour of the lubricating jelly and the mode of its application have to be considered carefully.

Burns, Electric↗
PubMed1978

[Biomechanical efficiency and biocompatibility of lubricating sprays PTFE or graphite (author's transl)].

The screws and plates used in operative treatment of fractures cause moments of friction between the bone screw head and the bone plate hole during the tightening of the screws. This results in hidden damage to the grinding metal surfaces, with the danger of erosion corrosion and in a reduction in the screw force. By covering the screw heads with the lubricating sprays PTFE or graphite friction was significantly reduced, the screw force increased by 40% and extensive damage to the surfaces avoided. Lubricating sprays or their extracts, in fetal calf serum or in dimethylsulfoxide, were added to fibroblast cultures. Toxicity was manifest as changes in the synthesis of DNA, as measured by autoradiography. Sprays or spray extracts in fetal calf serum did not inhibit cell proliferation. In vivo experiments in rats reflected the in vitro results, there being no evidence that toxic substances were released from the sprays by physiological solvents: There was a lack of histopathological changes in the inner organs and a local encapsulation of implants which was essentially like that in a teflon control group.

Aerosols↗
PubMedDate not supplied

Criteria for determining steam sterilization cycles for lubricated and nonlubricated mechanical equipment.

Requirements and procedures for determining steam sterilization cycles for lubricated and nonlubricated, complex, mechanical equipment are established. Factors affecting exposure times are discussed, as are procedures and data needed to determine the penetrability of steam into mechanical equipment, and the effect of lubricating oil in impeding steam penetration to the spore. The total effects of these factors in sterilizing times are presented. Sterilizers with a prevacuum cycle, which can remove air from the equipment efficiently and replace it with saturated steam, are recommended for complex mechanical equipment.

Equipment and Supplies, Hospital↗