Jocelyn M. Zika

Contribution of collagen and mineral to the elastic-plastic properties of bone

Tension testing of wet bovine haversian cortical bone demonstrated marked plastic behavior. Progressive surface decalcification of this bone with dilute hydrochloric acid resulted in progressive decreases in the tension yield point and the ultimate stress with no change in the yield strain or ultimate strain unless decalcification was complete. The slope of the plastic region remained identical throughout decalcification. These findings are consistent with an elastic-perfectly plastic model for the mineral phase of bone tissue in which the mineral contributes the major portion of the tension yield strength. The slope or stiffness of the plastic region of the stress-strain curve is a function only of the properties of collagen, which itself plays a minor role in the tension yield strength of bone.

The effect of histocompatibility matching on canine frozen bone allografts.

The value of histocompatibility matching in frozen bone allografts was studied in a canine cancellous ulnar segmental-replacement model. Frozen bone that was exchanged across strong and weak transplantation barriers was evaluated histologically and radiographically at thirteen and twenty-six weeks after grafting. Histological grading criteria quantified the type of union at each end of the graft and the degree of remodeling of the marrow, spongiosa, and compacta. Radiographic grading criteria included the presence of union at each end of the graft and the degree of remodeling of the graft segment. In vitro studies for serum antibody and cell-mediated immunity were carried out by isotopic cytotoxicity methods at seven intervals during the twenty-six-week study period. Histologically, the strong-barrier allografts had fewer osseous unions and less reorganization of spongiosa and marrow when compared with autograft controls at both thirteen and twenty-six weeks. Radiographically, the strong-barrier allografts at thirteen weeks had fewer unions and marked resorption of grafts material when compared with autograft controls. There were no differences between weak transplantation-barrier grafts and control autografts radiographically or histologically at thirteen and twenty-six weeks after grafting. Frozen bone allografts did not elicit detectable serum antibody or lymphocytes that were cytotoxic for donor cells.

Biological and physical properties of autogenous vascularized fibular grafts in dogs.

The biological and biomechanical properties of normal fibulae, fibulae that had had a sham operation, and both vascularized and non-vascularized autogenous grafts were studied in dogs at three months after the operation. The study was designed to quantify and correlate changes in these properties in orthotopic, stably fixed, weight-bearing grafts and to provide a baseline for additional studies of allografts. The grafts were eight centimeters long and internally fixed. The mechanical properties of the grafts were studied by torsional testing. Metabolic turnover of the grafts was evaluated by preoperative labeling of the dogs with 3H-tetracycline for resorption of bone mineral and with 3H-proline for turnover of collagen. Cortical bone area and porosity were measured. Postoperative formation of bone was evaluated by sequential labeling with fluorochrome. The vascularized grafts resembled the fibulae that had had a sham operation and those that had not had an operation with regard to the total number of osteons and the remodeling process, as measured both morphometrically and metabolically. The vascularized grafts were stronger and stiffer than the non-vascularized grafts and were not different from the bones that had had a sham operation. In contrast, the non-vascularized grafts were smaller, weaker, less stiff, and more porotic, had fewer osteons, and demonstrated increased turnover and resorption compared with the vascularized grafts, the bones that had had a sham operation, and the bones that had not been operated on.

Improved acceptance of frozen bone allografts in genetically mismatched dogs by immunosuppression.

UNLABELLED We studied the role of immunosuppressive therapy in improving the incorporation of frozen bone allografts exchanged across strong transplantation barriers in a canine cancellous ulnar segmental replacement model. Dogs receiving frozen bone from donors with major histocompatibility differences received one of three different immunosuppressive treatments. In two groups, azathioprine and prednisolone were administered for either twenty-eight or fifty-six days; anti-lymphocyte globulin was added for another twenty-eight-day group in a third regimen. Frozen bone was evaluated radiographically and histologically by criteria that quantified the biological characteristics of the bone itself and union between the graft and host at thirteen and twenty-six weeks after grafting. Graft incorporation in these animals was compared with graft acceptance in a similar group of untreated animals and in untreated animals in which bone was exchanged across weak transplantation barriers. Complications of immunosuppression included wound drainage, infection, weight loss, and falling white-blood-cell counts. Seven of the original thirty-seven animals died as a direct result of these complications. After twenty-six weeks the grafts in the recipients receiving immunosuppression appeared radiographically and histologically indistinguishable from those in the untreated, genetically closely matched group and from autografts. They were significantly better incorporated than identical allografts placed in untreated, genetically disparate recipients. There was no difference in the effectiveness of any of the immunosuppressive programs. CLINICAL RELEVANCE Immunosuppression improves the biological outcome of otherwise poorly performing frozen bone allografts in dogs. This finding suggests that treatments that modify the immunological response of the host without major side effects may be useful clinically in improving the success of massive frozen bone allografts.

Cyclosporin a and tissue antigen matching in bone transplantation: Fibular allografts studied in the dog

We studied the mechanical, metabolic, and histologic properties of short-term nonvascularized cortical bone grafts in a canine fibular graft model. Sham operated nonvascularized autotransplanted and allotransplanted bones were compared. The allografts were performed between dog leukocyte antigen (DLA) class I and II matched; DLA class I and II mismatched; and cyclosporin A (CsA) treated, DLA class I and II mismatched animals. Cyclosporin was given for 1 month, and all the animals were followed for 3 months after surgery. Mechanical properties were investigated using standard torsional tests, metabolic kinetics were assessed using isotopic prelabeling techniques, and histomorphometric analysis of cross-sectional area properties and sequential fluorochrome labels were performed. Autografts were mechanically stronger and stiffer than all the types of allograft. CsA-treated, DLA-mismatched allografts performed better than matched allografts. These in turn were stronger than non-CsA-treated, mismatched allografts, which underwent nearly complete resorption. These relationships were preserved in the metabolic and histologic analyses. In this short-term animal study, although DLA matching resulted in a slight improvement in graft outcome, mismatched grafts in dogs receiving a short course of cyclosporin A fared even better.

Relative and absolute changes in skin collagen mass in the rat

Abstract 1. 1. Whole skins of male and female Fischer rats from 2 weeks to 26 months old were analyzed for relative and total collagen mass. 2. 2. Total collagen mass of skin increased throughout life until a decrease was seen in the oldest male animals at 26 months of age. The collagen mass of skin was twice as large in males as compared to females. The relative content of collagen as a percent of skin weight reached a maximum value at 4 months after which it declined. As a percent of body weight, the collagen concentration became constant by 10–12 weeks. 3. 3. Relative and absolute changes in skin collagen are not parallel throughout life, due to alterations in the mass of noncollagenous proteins and lipids. Thus, relative measurements of skin collagen cannot be used as indices of the metabolic state. 4. 4. A comparison was made between the increase of collagen mass in skin, tendon and bone of male rats. Tendon and bone increased rapidly in collagen mass prior to the rapid increase of skin collagen mass.

The role of osmic acid in the treatment of immune synovitis

Thirty-seven New Zealand rabbits were observed for up to 1 year after their knee joints were instilled with 1 ml of 1% osmic acid. A selective destruction of synovial lining cells occurred with a concurrent synovitis, but lining cell regenerated by the eighth week. Nonprogressive abnormalities were also present in the cartilage. When an immune synovitis was induced in both knees of 16 rabbits, the osmic acid treated joint demonstrated a significantly greater synovitis and progressive aberrations compared to the untreated knee.

Comparison of whole calvarial bones and long bones during early growth in rats. Histology and collagen composition

The distribution of ossified collagen (bone) and uncalcified collagen (fibrous tissue and cartilage) was compared histologically for rat and dog calvaria at birth. The relative amount of bone and uncalcified collagen was quantitated morphologically for rat calvaria during the first four weeks of rapid growth. Whereas dog calvaria are essentially ossified at birth, rat calvaria at birth consist mostly of fibrous tissue but rapidly become ossified with growth. Bacterial collagenase was used to separate uncalcified collagen from calcified collagen of whole membranous bones (frontal and parietal) and long bones (femur and humerus) at birth from man, monkey, dog, guinea pig, rabbit and rat. By this means quantitative changes in the relative fractions of the two forms of collagen were determined during the first eight weeks of postnatal growth for each type of rat bone. Quantitative biochemical data on whole rat bones (calvarium, femur, humerus) confirmed measurements based on histology which showed that at birth rat calvaria are mostly uncalcified as compared to other species whose bones are mostly ossified at birth. With growth rat membranous bones ossify more rapidly than long bones.

Effects on bone of vascular interruption: Turnover and morphology in isotope-prelabelled rats

The effects of bone devascularization were evaluated histologically and metabolically in rats prelabelled with 45Ca, 3H-tetracycline and 3H-proline by quantifying cortical bone resorption and formation. The interruption of blood supply to bone without invading its integrity resulted in a marked increase in bone turnover (resorption and formation) during the first and second months. The stimulated increase in bone resorption and formation did not affect the resultant mass of collagen and calcium. Thus, the increase in bone resorption was compensated by an equivalent increase in bone formation.

Comparison of whole calvarial bones and long bones during early growth in rats. II. Turnover of calcified and uncalcified collagen masses.

The increase of total collagen and its destruction were compared for whole calvaria and long bones from young growing rats prelabeledin utero with3H-L-proline. Rats were compared from birth to 16 weeks of age. Long bones and calvaria were isolated as intact anatomical units for autoradiography or separated by collagenase into calcified and uncalcified collagens. Autoradiography using14C-L-proline demonstrated eccentric remodeling of bone collagen. With growth the mass of calcified collagen (bone) increased rapidly in calvaria and long bones. A similar increase in the mass of uncalcified collagen (mainly cartilage) occurred in the long bones; a very small increase occurred in the fibrous tissue of calvaria.Total and specific radioactivities of collagens at each age were compared to that present at birth. With growth remodeling an almost complete loss of pre-existing radioactive collagen occurred from uncalcified fibrous tissue of calvaria as compared to a smaller but substantial loss from the uncalcified cartilage of long bones. A marked loss of calcified collagen occurred in long bones as compared to a smaller loss from calvarial bones. The isotopic data indicate a large turnover of fibrous tissue (type I collagen) with growth remodeling as compared to a smaller turnover of bone (calcified, type I collagen) and cartilage (type II collagen). The turnover rate of skeletal collagens depends upon whether the collagen is calcified or not, and not upon the type of collagen.