muramidase and Fractures--Bone

Topics: Animals; Cartilage; Chick Embryo; Culture Techniques; Electric Stimulation; Electromagnetic Fields; Fractures, Bone; Glycosaminoglycans; Muramidase; Wound Healing

Multilayered gelatin coatings were created to mimic growth factor profiles that normally occur during fracture healing. A model was developed to relate crosslinking and loading of individual layers to protein release. Modeling was simplified by dividing release profiles into three phases. The diffusion-controlled phase was determined by calculating periods of constant diffusivity for each homogeneous layer within devices. Diffusivity was a power law function of crosslinking. Fick's second law of diffusion was then used to determine release during the diffusion-controlled phase. Secondary diffusivity was determined by summing resistances of each successive homogeneous layer. The initial burst phase was defined as events proceeding the diffusion-controlled phase. Percentage of drug burst was a linear function of crosslinking. Release during the degradation-controlled phase, events following diffusion-controlled phase, was estimated based on first order hydrolysis of crosslinks. The model predicted time-variant release of differently labeled protein measured experimentally, and it can be used to design coatings to recreate the cascade of biomolecules that determine natural bone repair.

Topics: Animals; Coated Materials, Biocompatible; Cross-Linking Reagents; Culture Techniques; Delayed-Action Preparations; Diffusion; Fractures, Bone; Gelatin; Glutaral; Growth Substances; Models, Theoretical; Muramidase; Wound Healing

Investigations have suggested that lysozyme (E.C. 3.2.1.17) is involved in bone mineralization. High concentrations of lysozyme is found in the growth plate near cartilage bone junction, where it is located at the collagen fibrils and in the ground substance. Quantitative studies of lysozyme levels were made in ossifying tissue of healing fractures, to confirm the existence of this relationship on bone repair. Callous tissue, serum samples and normal bone was collected from 42 rats at 15 intervalls during a 50 day healing period. Agar gel diffusion test was used for quantitation of lysozyme. Electrophoresis of tissue extract and standard henn egg white lysozyme served as control. Lysozyme levels in callous tissue increased significantly (4--5-fold) from 4.--21. day p. trauma and subsequently decreased. The concentration in serum samples did not change significantly. Changes in Ca concentration and histological studies during tests confirm a direct relationship between bone mineralization and lysozyme level changes.

Topics: Animals; Bony Callus; Calcium; Femoral Fractures; Fractures, Bone; Muramidase; Osteogenesis; Rats; Wound Healing