Biomaterials, medical devices, and artificial organs最新文献

A new method for the covalent binding of heparin to artificial surfaces has been developed. The heparinized surface releases insignificant amounts of heparin and can be regarded as stable. The blood contact properties as studied in vitro revealed that the surface was highly thromboresistant in terms of reduced platelet adhesion, surface catalyzed adsorption and inhibition of thrombin and capacity to prevent clotting of nonanticoagulated blood.

In a test of a hypothesis of cell-to-cell communication via their endogeneous photon emissions, the nearly pure collagen fibers in tendon were found to exhibit the fiber optic property of axially conducting light, providing a mechanism for photon exchange between nonadjacent cells. Further, it was found that light penetrates farther along the tendon fibers when tension is applied to an end-illuminated tendon, establishing that an elastooptic mechanism exists for the modulation of photon signals in transit between cells, in the hypothesized system of cell-to-cell photon communication.

Cardiac pacing leads coated with povidone-[131I] were implanted in dogs and the leaching of radioactivity from the leads was monitored by external scintigraphy. The activity which had dissipated from the pacing leads was not as [131I]-iodide, but as povidone-[131I]. Only 50% (mean) of the activity remained on the pacing leads after two weeks while a significant amount of radioactivity was eliminated via urine and feces. The liver was a major site of accumulation of retained activity which had leached off the pacing leads. There was no evidence of large pieces of povidone-[131I] in the lungs of the dogs, all of which appeared healthy at the time of sacrifice. The results of this study support the conclusions of a long-term study indicating that povidone is a safe and suitable coating material for pacing leads.

While many devices that come into direct contact with patients' blood have been shown to be safe with respect to their effects on the cellular components and coagulation system of blood, many have not been examined with respect to their potential to activate the complement system. We present evidence that suggests that a combination of nylon plus polypropylene, and a combination of polyester plus polypropylene, found in blood microfilters used to protect patients from gaseous and particulate embolism during cardiopulmonary bypass, produce significant (p less than 0.01, p less than 0.05, respectively) C3a generation during incubation in heparinized plasma. Filter mesh composed of nylon plus polypropylene produced significantly more (p less than 0.01) C3a than the polyester plus polypropylene combination.

By utilizing the technique of cell elastimetry, which measures the negative pressure required to aspirate human polymorphonuclear leukocytes (PMNs) into a micropipette, a correlation between PMN deformability and cellular movement is confirmed. The effects of the synthetic chemotactic peptide, N-formyl-methionyl-leucyl-phenylalanine (f-met-leu-phe) on the deformability and chemotaxis of PMNs have been investigated, and a relationship between peptide concentrations and PMN deformability, which parallels the effects of the peptide on filter (chemotactic) studies, has been established. Experimental evidences indicate that alterations in PMN deformability occur as a natural consequence of stimulation of PMNs with a chemoattractant and that cellular deformation is a prerequisite to PMN movement. Introduction of this analytical technique into the study of PMN movement disorders has already yielded significant insights which implicate a membrane-associated abnormality intrinsic to the impaired motility of neonatal PMNs. This technique can, therefore, serve to provide a sensitive probe with which to dissect the various perturbations of PMN dysfunction. Cell elastimetry can also be utilized to generate quantitative information on mechanical and deformability properties of PMNs; such information is needed for the establishment of a rheological model (for PMNs) which can assist the analysis of almost every functional problem involving PMNs.

Plasma-sprayed alumina on 316L stainless steel discs was implanted in Sprague-Dawley rats for six months; at which time the animals were sacrificed, and selected tissues analyzed for aluminum concentration using atomic absorption spectrophotometry. The liver, testes, and kidneys exhibited significant increases in aluminum ion concentration.

Porosity is an essential component for long term function of small internal diameter synthetic vascular prostheses. Theoretically, porosity is required for healing by providing a scaffold for ingrowth of periprosthetic tissues. Porosity may be required for transfer of fluids and ions in prostheses even if tissue ingrowth does not occur. Increased permeability of vascular grafts has been shown to enhance tissue incorporation. Implants with pore sizes greater than 10 microns but less than 45 microns become ingrown with fibrohistiocytic tissue and capillaries. Implants with pore sizes greater than 45 microns are ingrown with organized fibrous tissue and minimal histiocytic response. The phenomenon of differential ingrowth may have important functional significance. Prostheses which heal with organized fibrous tissue have the potential for long term contracture, strangulation of vascularity and calcification. Fibrohistiocytic tissue has low mechanical strength and does not appear to contract or calcify. Elastomeric microporous vascular prostheses which are minimally ingrown or ingrown with fibrohistiocytic tissue maintain compliance after months of implantation. This study was designated to determine the effects of healing on the compliance of small internal diameter vascular replacements and to correlate the compliance to patency rates.

This investigation presents a new design of the femoral component used in total hip arthroplasty. The design utilizes a tensile component which screws into the femoral stem from the lateral side of the femur. The potential advantages of utilizing such a component are 1) PMMA cement may be not needed to hold the implant in place, 2) better stress distribution in the region of the greater trochanter is achieved, 3) reduced stress levels in the implant, and 4) the femoral stem may be shortened to reduce the amount of reaming required. Two dimensional, plane stress finite element models of the proximal end of a normal femur, a femur with the new implant design, and a femur with a control Charnley-Cobra femoral component were developed. Loads simulating a one-legged stance were applied on the models. The normal and shear stresses, the octehedral shearing stress and the directions of principal stress were calculated for comparison with the normal femur. There was distinct improvement in bone stress distribution for the femur with the experimental implant as compared to the femur with the control prosthesis. The stress concentration normally observed in the mid-shaft area of the Charnley femoral stem was also not seen in the new design.

The hemodynamic responses to increased afterload of the left ventricle were studied in conscious calves during exercise. The calves were chronically instrumented to measure (or derive) heart rate, stroke volume, cardiac output, iliac, superior mesenteric and renal flows and resistances, mean carotid, aortic, right atrial, pulmonary artery, and left atrial pressures, the systemic and pulmonary pressure gradients, and total systemic and total pulmonary resistances. The calves were also instrumented to produce reversible partial constriction of the ascending aorta and common carotid arteries and for cooling of the cervical vagus nerves. The hemodynamic responses to increased afterload were characterized during treadmill exercise at 2 mph. These responses were compared to the hemodynamic responses to bilateral carotid artery occlusion with and without vagal cooling.