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At least 343 records · Page 19Linked to original sources
PubMedDate not supplied

A biomechanical study of the static stabilizing effect of knee braces on medial stability.

The purpose of this project was to determine if commercially available braces could be shown to produce objective evidence of medial stabilization of the knee. Commercially available athletic braces were evaluated for their effect on abduction forces applied to a cadaver knee with no instability and with experimentally created medial instability. Under computer control, abduction forces were applied while simultaneous data were obtained from an electrogoniometer and transducers applied to the anterior cruciate ligament and the superficial medial collateral ligament at 0 degrees, 15 degrees, and 30 degrees of flexion. Our results showed a reduction in abduction angle using functional braces, whereas prophylactic braces demonstrated little or no protective effect.

Biomechanical Phenomena↗
PubMedDate not supplied

Preparation and stability of liposome-type artificial red blood cells stabilized with carboxymethylchitin.

Liposome-type artificial red blood cells stabilized with carboxymethylchitin (mean diameter 310 nm) were prepared by a two-step emulsification technique. Sheep haemolysate was dispersed as fine droplets in a lecithin solution in dichloromethane to yield a W/O-type emulsion. The W/O emulsion thus obtained was then dispersed in an aqueous carboxymethylchitin solution to give a W/O/W-type complex emulsion. Removal of the organic solvent by evaporation from the complex emulsion left an aqueous suspension of the artificial red blood cells. The haemoglobin-trapping efficiency of the cells was found strongly dependent on the pH of the carboxymethylchitin solution used. The artificial red blood cells underwent disintegration by the action of surfactants. When a comparison was made among those surfactants which have the same alkyl chain length, the degree of cell disintegration was in the increasing order, anionic greater than cationic greater than nonionic. Globulin and fibrinogen produced no disintegration of the cells while albumin disrupted the cells to a slight extent.

Animals↗
PubMed2000

Vertical facial pattern and orthodontic stability. Part II: Facial axis changes and stability.

Lateral cephalograms and study casts of 55 patients were evaluated to determine if any relationships exist between Facial Axis changes occurring during and after active treatment and either the pretreatment Jarabak Facial Height Quotient or the amount of post-treatment occlusal change, as measured with a weighted PAR score. No significant relationships could be found. There was instead a wide range of individual variation in the post-treatment behaviour of both the Facial Axis and the weighted PAR score, in both the total sample and three Jarabak Facial Height subgroups. Long-term Facial Axis changes occurring in individual patients, however, were not necessarily associated with occlusal deterioration. Since the Facial Axis is likely to change to some extent in the long-term, it was suggested that widely recommended methods for Facial Axis control during treatment should be considered primarily for functional and aesthetic reasons, rather than on the basis of directly ensuring long-term occlusal stability.

Adolescent↗
PubMed1993

[Dynamic fracture stabilization with the DYBASTAB--with the help of dynamic compensating stabilizers--DYNASTAB D-K--new outlook on treating fractures].

Dynamic stabilizer DYNASTAB D-K for functional, ambulatory treatment of fractures is presented. The possibility to include an active hinge enabling physiological movement of the injured or remaining in the injured zone joint allows for an early mobilization of the limb concerned. Solid, spatial screws anchoring enables early axial dynamization within the union zone. Plastic cubes reduce the weight and prevent disturbance of electrophysiology of the fracture healing. The hydraulic chamber pressure measurement taken at the load will permit the assessment of bony union consolidation.

Bone Screws↗
PubMed1975

[Comparative studies with various anticoagulant stabilizer combinations for the preservation of blood specimen in leukosis diagnosis. II. Testing the application possibilities of new anticoagulant stabilizer combinations for the hematologic diagnonsis of leukosis].

The anticoagulant Chelaplex III in aqueous solution with two new stabilizers (methenamine and tannin) was tested for the preservation of blood samples, together with another combination composed of oxalic acid and methenamine solution. The eventual aim was to test their suitability for use with blood specimens dried in the tube, but this was not done in the present experiments. It was shown that a combination of 5% oxalic acid with 36% methenamine was at least as good as the conventional Chelaplex III-formaldehyde combination for inhibiting coagulation, and it was relatively cheap.

Animals↗
PubMed1996

Glenohumeral stability. Biomechanical properties of passive and active stabilizers.

The shoulder is characterized foremost by its mobility and large range of motion. The glenohumeral joint is notable for its relative lack of bony constraint, relying heavily on the congruent articulating surfaces and surrounding soft tissue envelope for static and dynamic stability. Effective function in the articulation is achieved by a complex interaction between the various articular and soft tissue restraints. The rotator cuff muscles center the humeral head in the congruent glenoid fossa through the midrange of motion, when the capsuloligamentous structures are lax. However, incongruent joints, especially in positions of loading asymmetry (in external rotation), have larger translations that occur at the extremes of motion. Excessive translations are then effectively restricted by the mechanical properties of the inferior glenohumeral ligament. When the capsule is tightened anteriorly it results in an anterior tether and causes an associated posterior shift in contact on the glenoid. The posterior migration of the humeral head center and glenohumeral contact are again more pronounced in shoulders with reduced congruence. Additional studies of normal motion in different planes, the effects of rotator cuff pathology and dysfunction on the kinematics of the joint, proprioception of the capsule, and biomechanical tests of the inferior glenohumeral ligament and other components of the joint capsule at strain rates associated with injury, need to be conducted to understand the specifics of normal shoulder function and the pathophysiologic processes that occur during shoulder degeneration.

Biomechanical Phenomena↗
PubMed1997

Effect of lysozyme on the stability of polyester nanocapsules and nanoparticles: stabilization approaches.

The efficacy of colloidal particles as drug carriers is closely related to their interaction with proteins and enzymes in different body fluids. In the present work, we analysed the interaction phenomenon between lysozyme (LZM), a positively charged enzyme that is highly concentrated in mucosas, and two different drug carriers: nanocapsules made of an oily core coated by the polymer poly-epsilon-caprolactone (PECL) and nanoparticles made solely of PECL. Results showed that the interaction of LZM with these colloidal drug carriers is highly affected by their surface charge. Nanocapsules, because of their important negative charge (-40 mV), adsorbed a great amount of LZM, which is positively charged. This adsorption process, which was also evidenced by the significant reduction of the nanocapsules' negative surface charge, led to the degradation of the polymer coating and the aggregation of the nanocapsules. In contrast, nanoparticles had a low negative surface charge (-8 mV) and adsorbed only a small amount of LZM, which did not cause the destabilization of the system. Furthermore, the molecular weight of the polymer forming the nanoparticles did not change. Finally, it was observed that the destabilizing effects caused by the adsorption of LZM onto the nanocapsules can be prevented by previous adsorption of the cationic poly(amino acid) poly-L-lysine. Using this approach the adsorption of LZM was hindered and its consequences avoided.

Adsorption↗
PubMedDate not supplied

Thermally stabilized immunoconjugates: conjugation of antibodies to alkaline phosphatase stabilized with polymeric cross-linkers.

A method of conjugating poly(glutamic acid) poly(phosphorothioate)-cross-linked alkaline phosphatase to maleimide-derivatized immunoglobulin is described. Intramolecular autocatalyzed cross-linking of alkaline phosphatase at 2:1 to 4:1 polymer:enzyme ratios introduced 32-68 thiolates on the surface of the enzyme. Depending on the stoichiometry of polymer to enzyme, the cross-linked alkaline phosphatase retained 75-90% of its native catalytic activity. The cross-linked thiolate-functionalized alkaline phosphatase was conjugated to maleimide-derivatized immunoglobulin. Compared to a control prepared using non-cross-linked alkaline phosphatase, these conjugates were smaller in size and more stable to heat. The enzymatic activity of the cross-linked conjugates after incubation at 45 degrees C and pH 7.5 for 25 days was 35% higher than those of the highest-activity control conjugates. The conjugation process could be controlled by varying the stoichiometries of poly(glutamic acid) poly(phosphorothioate), alkaline phosphatase, and immunoglobulin.

Alkaline Phosphatase↗
PubMed1995

Protein stability as a function of denaturant concentration: the thermal stability of barnase in the presence of urea.

The conventional procedure for analyzing urea denaturation curves assumes that the free energy of unfolding (delta GU-F) is linearly related to [urea] that is, delta GU-F = delta GH2O(U-F)--m[urea], where m is a constant, specific for each protein, and delta GH2O(U-F) is the free energy of unfolding in water. This relationship can be measured directly, however, over only a small concentration range of approximately +/- 0.8 M urea around the midpoint of the unfolding transition. A nagging discrepancy (1.6 kcal mol-1) between delta GH2O(U-F) at 298 K of barnase extrapolated from such an equation and the equivalent value obtained from thermal unfolding measurements has stimulated a re-evaluation of the equation. Differential scanning calorimetric measurements have been made of the thermal unfolding of barnase in the presence of concentrations of urea between 0 and 4.5 M, the midpoint of the unfolding transition at 298 K, to test the denaturation equation over a wide range of [urea]. Values for delta GU-F at 298 K (delta G298U-F) for each concentration of urea were extrapolated from the calorimetrically measured enthalpies and the denaturational heat capacity change (delta Cdp) measured for that concentration of urea. A plot of delta G298U-F against [urea] deviates systematically from linearity and fits better the equation: delta G298U-F = 10.5 +/- 0.08 - ((2.65 +/- 0.05) x [urea]) + ((0.08 +/- 0.01) x [urea]2) kcal mol-1. The curvature in the plot leads to apparent values of m that increase when measurements are made at lower concentrations of urea. This could account for increases in m at low values of pH or in destabilized mutants since the protein denatures at lower concentrations of urea. It has been shown previously that small curvature in the free energy of unfolding versus [urea] leads to negligible errors in measurements of delta delta GU-F, the change in free energy of unfolding on mutation, providing that the curvature is similar for all mutants. The calorimetrically measured enthalpies of unfolding are decreased in the presence of urea while delta Cdp is increased. Both of these observations are consistent with an overall exothermic interaction between urea and protein with a net increase on unfolding.

Bacterial Proteins↗