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(1) An apparatus has been constructed to measure the coefficient of friction of synovial membrane against a glass slider. (2) Provision was made to vary the load on the specimens. (3) The coefficient of friction varied from 0-006 to 0-07. (4) A presentation similar to that used in the Sommerfeld analysis of journal bearings indicated that in these experiments synovial membrane was lubricated in the hydrodynamic regimen.
Silicone 300 has been evaluated as an artificial lubricant in osteoarthrotic joints by means of a pilot study in five inpatients and a control trial of 25 outpatients with 40 osteoarthrotic knees. Sequential analysis showed a significant benefit from saline compared with silicone at one week follow-up and no significant difference at one month.Measurement of stiffness with a knee arthrograph showed no difference in reduction of stiffness between the two substances. In a study of 18 rabbits there was no evidence that silicone was retained in the joint cavity for longer than 48 hours. There was a failure of clearance of iodinated serum albumin for as long as three to four days after the injection of silicone, suggesting some obstruction to lymphatic outflow. Experimentally produced cartilaginous defects did not heal quicker with the injection of silicone into the joint.
Three subjects, all smokers, handling stainless steel tubes suffered repeated attacks of general malaise, chills, and fever lasting for several hours, mainly after gas soldering. Provocations by rubbing smoking tobacco against a tube produced similar attacks, and leucocytosis, after a few hours. The presence of fluorine on the tubes and in the febrifacient tobacco was shown. A fluorocarbon polymer lubricant was suspected of causing the attacks. Heating (1000 degrees C) of the tubes eliminated the effect.
Spatially resolved and time-resolved understanding of complex fluid situations compose a new frontier in physical chemistry. Here we draw attention to the significance of spatially resolving systems whose ensemble average differs fundamentally from the spatially resolved individual elements. We take examples from the field of fluid phospholipid bilayers, to which macromolecules adsorb; the field of polymer physics, when flexible chains adsorb to the solid-liquid interface; and from the field of lubrication, when two solids are squeezed close together with confined fluid retained between them.
Immunofluorescence for hyaluronic acid occurred intracellularly in morphologically highly specialized areas in the adult human inner ear, for instance in the cuticular plates of all types of hair cells, at the apposition between outer hair cells and Deiter's cell bodies and in the near-surface area of Hensen's cells. The cytoskeletal organization in these regions is characterized by tightly packed filamentous proteins. Under physiological stimulus these regions undergo micromechanical change, either actively moving (force generation) or passively vibrating with changes in elasticity. Hyaluronic acid might therefore act as a friction-reducing molecular lubricant. In the lateral wall of the cochlea an accumulation of hyaluronic acid occurred in the loose connective tissue of the spiral ligament, in particular close to the stria vascularis. Due to its complex molecular network, hyaluronic acid offers considerable resistance to bulk flow of water and may exclude molecules. The basal cell region of the stria vascularis is thus given additional support to minimize (seal?) the stria vascularis towards all other areas except the endolymphatic space. Here, hyaluronic acid could act as a molecular filter.
Upon exposure to blood, rapid adsorption of proteins is the initial event at the contacting surface, followed by the adhesion of platelets and other blood components. Surfaces absorbing albumin appear to possess antithrombotic character in discouraging adhesion of platelets. Therefore, for the development of a blood contacting device, the interfacial events are extremely important and need serious investigation. We have attempted to observe the variations in competitive adsorption of fibrinogen and albumin onto the polyetherurethane urea (PEUU) surface in the presence of external lubricant, such as calcium stearate and silicone fluid coating. It seems, in the presence of such mediators, that fibrinogen adsorption is increased relatively with reduction in albumin at the surface.
A three-dimensional structural model for salivary statherin in aqueous phase has been developed using structure prediction, circular dichroism, molecular modeling, and mechanics. The relevant structural features of statherin are N-terminal helix segment connected to a long poly-L-proline type II segment, which is followed by a short extended structure. Using this model, the hydroxyapatite binding ability of statherin has been explained. The hydroxyapatite binding region is comprised of the N-terminal acidic residues (Asp-pSer-pSer-Glu-Glu) and Glu-26, which are clustered together in space. Partial conformational unfolding and oriented aggregation of several statherin molecules at the enamel surface provides an amphipathic film that is responsible for the boundary lubrication exhibited by statherin.
We report on a severe allergic reaction during urethral catheterisation, initially erroneously attributed to natural rubber latex (NRL). However, the negative investigations for latex, the uneventful further applications of NRL, the positive skin test and basophil activation test for chlorhexidine strongly support diagnosis of chlorhexidine anaphylaxis. This case illustrates that it is not widely appreciated that "innocent" products such as urethral lubricants may elicit serious life-threatening reactions. Careful inspection of the medical records is once again re-emphasised to be mandatory in order to avert subsequent anaphylaxis.
The effects of the amounts of lubricants (magnesium stearate 0-5% and talc 0-3%) and changes in compaction rate and tablet porosity on the mechanism of drug release from high drug-load controlled-release theophylline tablets have been examined. Drug release was satisfactorily described by a surface-erosion model that takes into account the geometry of the tablet, differential radial and axial erosion rates, and the initial burst effect (r2 > 0.99 for all formulations). The axial and radial erosion rate constants were inversely proportional to the amount of magnesium stearate in the formulation (P < 0.0001). The most dramatic reductions in erosion rate occurred between 0 and 1% magnesium stearate content. For magnesium stearate concentrations > or =2.5% the ratio of radial to axial erosion rate constants was essentially constant at 3 (approx.); however, for formulations with magnesium stearate < or =1% the ratio tended toward unity. Reducing matrix porosity over the range 26 to 14% resulted in reduced erosion rates. However, a threshold of 17% (approx.) porosity was identified below which further reductions in porosity resulted in only incremental changes in release rates. The rate of erosion and drug release was insensitive to changes in machine speed over the range 20 to 100 rev min(-1). For highly loaded matrix tablets containing sparingly soluble drugs, such as theophylline, magnesium stearate at appropriate levels can modulate the erosion rate constants and act as an effective release-controlling excipient. Drug-release profiles are predictable and relatively robust in terms of changes in compaction rate and applied force routinely encountered in large-scale tablet manufacturing.
In the model intended for short-term loading (such as during the walking cycle) of a human synovial joint in the lower extremities, cartilage lubricated by Newtonian synovial fluid is considered to be incompressible elastic and subchondral bone is considered to be rigid. The model is non-diffusional, i.e. no interstitial fluid flow occurs across the articular surfaces. A simple plane strain case of the human ankle joint is considered. For high steady loading applied in the centre of the stationary tibial arc and for steady sliding of the talar arc, this model shows that individual physiological variations in the geometry of the articular surfaces have only a small effect on the contact stress distribution and the fluid film thickness. If this load is applied eccentrically in the tibial arc, the contact pressure distribution varies more with surface geometry, but the minimum fluid film thickness differs little from that for symmetric loading. The maximum contact pressure is placed eccentrically in this case, but its value is changed only little when compared to the central loading of the same value. In order to explain different distribution patterns of subchondral bone mineralization, it is anticipated that the total load peaks of periodic time-dependent loads are transmitted centrally in some incongruent joints and eccentrically in others.
A full numerical solution procedure has been developed for the microelastohydrodynamic lubrication analysis of a stationary compliant wavy layered surface firmly bonded to a rigid substrate. The results obtained have been compared with those using a simplified method adopted by Dowson and Jin(1) and good agreement has been obtained.
This paper describes the development of practical Fourier transform infrared (FT-IR) methods for the determination of acid number (AN) and base number (BN) in lubricants through the combined use of signal transduction via stoichiometric reactions and differential spectroscopy to circumvent matrix effects. Trifluoroacetic acid and potassium phthalimide were used as stoichiometric reactants to provide infrared (IR) signals proportional to the basic and acidic constituents present in oils. Samples were initially diluted with 1-propanol, then split, with one half treated with the stoichiometric reactant and the other half with a blank reagent, their spectra collected, and a differential spectrum obtained to ratio out the invariant spectral contributions from the sample. Quantitation for AN and BN was based on measurement of the peak height of the v(C = O) or v(COO) absorptions, respectively, of the products of the corresponding stoichiometric reactions, yielding a standard error of calibration of < 0.1 mg KOH/g oil. The AN/BN FT-IR methods were validated by the analysis of a wide range of new and used oils supplied by third parties, which had been analyzed by ASTM methods. Good correlations were obtained between the chemical and FT-IR methods, indicating that the measures are on the whole comparable. From a practical perspective, these new FT-IR methods have significant advantages over ASTM titrimetric methods in terms of environmental considerations, sample size, and speed of analysis, as well as the variety of oil types that can be handled. FT-IR analysis combining stoichiometric signal transduction with differential spectroscopy may be of wider utility as an alternative to titration in the determination of acid or basic constituents in complex nonaqueous systems.
An elderly woman developed lipoid pneumonia due to the inhalation of mist from a spray lubricant that she was using as a liniment for sore back and neck muscles. This unusual practice is reported to be common among older people bothered by rheumatism. The potential for this complication to occur in other patients leads us to present this case report.
Fifteen bacterial monocultures were isolated from lubricant-contaminated wastewater of an electric power station in Sofia. Six isolates showed best growth in liquid media with 1.5% hexadecane, and on mineral salt agar plates supplemented with one of the following hydrocarbons: n-hexadecane, paraffin, kerosene and samples of wastewater. The ability of all isolates to produce extracellular hydrolytic enzymes and surface-active glycolipids was assessed on the basis of their growth on hydrocarbons. The study of this relatively closed micro-ecosystem revealed the existence of well-balanced microbial consortium where different members have their own role and support each other. On this basis, an alternative approach is proposed for bioaugmented clean up of wastewater contaminated with hydrocarbons and organic polymers using a mixed culture of indigenous bacteria that combines the best producers of glycolipids and hydrolytic enzymes.
Certain wear metals (Fe, Cr, Ni, Cu and Zn) of various lubrication oils were determined by means of ICP-OES and FAAS. The kerosene dilution method, which is used widely together with ICP-OES, was applied with both methods here. Calibration standards were made from a commercial organo-metallic standard. Our aim was to clarify the possibility of using the quick kerosene dilution method together with FAAS for a rapid check for certain indicator metals. Metal determinations with FAAS were accurate enough for quantitative work in machine condition diagnostics and waste oil characterization, when compared with those with ICP-OES.
Morphological and biophysical techniques described in this study have shown that membrane derangement occurs in human cataractous lenses. The data suggest that these disruptions were globules, vacuoles, multilamellar membranes and clusters of highly undulating membranes. Deleterious structural damage of the lens fibre cell plasma membranes serve as the primary light-scattering centres that cause the observed lens opacity. Nuclear cataract, a major cause of loss of lens transparency in the aging human, has been thought to be associated with oxidative damage, particularly at the site of the nuclear plasma membrane. Phospholipid molecules modified by oxygen accumulate in the lipid bilayer, change its geometry and impair lipid-lipid and protein-lipid interactions in lenticular fibre membranes. Lipid peroxidation (LPO) is a causative and pathogenic factor in cataract. Increased concentrations of primary molecular LPO products (diene conjugates, lipid hydroperoxides, oxy-derivatives of phospholipid fatty acids) and end-fluorescent LPO products have been detected in the lipid moieties of aqueous humour samples and human lenses obtained from patients with senile and complicated cataracts as compared with normal donors. In the present study, a rapid and simple high-performance liquid chromatographic (HPLC) assay for determination of imidazole-containing dipeptides in the aqueous humour of the eye was developed. The method was applied to determine the pharmacokinetic parameters and the time-course of N-acetylcarnosine and L-carnosine-related product in the eye, following a single dosage of topical ocular administration of peptide. Utilising data from pharmacokinetic studies and the specific purity of the N-acetylcarnosine (NAC) ingredient as a source of the pharmacological principle L-carnosine, we have created an ophthalmic time-release prodrug form including the US FDA-approved carboxymethylcellulose lubricant and other essential ingredients (Can-C, private label Nu-Eyes). This formulation increases the intraocular absorption of L-carnosine in the aqueous humour and optimises its specific antioxidant activity in vivo while reducing the toxic effects of lipid peroxides on the crystalline lens. L-carnosine that enters the aqueous humour can accumulate in the lens tissue for a reasonable period of time. The presence of L-carnosine in transparent crystalline lenses during normal aging was detected and its concentration in this case was about 25 microM. At different stages of cataract development, the level of L-carnosine drastically decreased, reaching about 5 microM in ripe human cataracts. However, administration of pure L-carnosine (1% solution) to the rabbit eye (instillation or subconjunctival injection) does not lead to accumulation of this natural compound in the aqueous humour at the time level over 30 minutes at a concentration exceeding that in placebo-treated matched eyes, and its effective concentration is exhausted more rapidly. Use of NAC prodrug eye drops optimises the clinical effects of L-carnosine in the treatment of ophthalmic disorders (such as prevention and reversal of cataracts in human and animal [canine] eyes). The data provided predict a clinical effect with NAC ophthalmic prodrug, and show that the magnitude and duration of this effect are directly related to the bioavailability of L-carnosine released from NAC in the aqueous humour of the anterior eye segment. The ophthalmic NAC drug shows promise in the treatment of a range of ophthalmic disorders that have a component of oxidative stress in their pathogenesis (including cataract, glaucoma, dry eye, vitreous floaters, inflammatory disorders, and corneal, retinal and systemic diseases [such as diabetes mellitus and its ophthalmic complications]). There is a need for further and better collaboration between Innovative Vision Products' cataract control and ophthalmic services, improved education of people affected by cataract, a commitment that N-acetylcarnosine eye drops will be the preferred treatment before orthodox cataract surgery is attempted, and consideration of outcomes and a possible role of the NAC drug cataract treatment as source of referral for orthodox surgical, ophthalmic and optometric services.
The Centers for Disease Control and Prevention and the American Dental Association guidelines recommend sterilization of dental handpieces after each use. Steam autoclaving is the most commonly used sterilization method. However, pressurized steam causes corrosion and partial combustion of the handpiece lubricant, leaving a sticky carbon residue on the turbine which must then be replaced after several usages. Replacement of autoclave-damaged dental handpieces represents a major expense for dentists that may be avoided through the use of less destructive sterilization techniques.
We used Panaxylocaine as a suitable lubricant with gargling before insertion of laryngeal mask for twenty preoperative breast cancer patients. Patients were divided into two groups; Control group (N = 10) received water-based lidocaine gel just before insertion of laryngeal mask, and Panaxylocaine group (N = 10) received Panaxylocaine as a premedication for breast cancer operation. Compared to water-based lidocaine gel, Panaxylocaine was more effective for oral discomfort after insertion of laryngeal mask. But there was no difference between two groups about oral paresthesia. We conclude that Panaxylocaine is a good premedication before insertion of laryngeal mask preventing oral and pharyngeal complications.