PubMed Health⌕ Search

Biomedical subjects

D J Simmons

Publications and source records attributed to D J Simmons.

At least 145 records · Page 8Linked to original sources
PubMedDate not supplied

Negatively charged beads and transforming growth factor-beta1 stimulate bone repair in rabbits.

Previous studies have shown the osteogenic potential of negatively charged Sephadex beads when used to heal osseous defects in an animal model. The present study examined the effect of adding the growth factors transforming growth factor-beta1 and basic fibroblast growth factor to negatively charged Sephadex beads and neutral (non-osteogenic) Sephadex beads in a critical size calvarial defect in rabbits. New Zealand White rabbits were divided into six groups of five rabbits; 15 mm parietal defects were created and filled with either negatively charged Sephadex beads (three groups) or neutral Sephadex beads (three groups). Each group received either 2 microg of transforming growth factor-beta1, 1 microg of basic fibroblast growth factor, or buffer (control). Animals were killed at 5 weeks, and their calvaria were submitted to plain radiographic and histomorphometric analyses. Defects treated with negatively charged Sephadex beads produced significantly more new trabecular bone than neutral Sephadex beads (p < 0.01), whereas the neutral beads treated with transforming growth factor-beta1 formed significantly more bone than controls. The addition of transforming growth factor-beta1 to negatively charged beads resulted in near closure of the craniotomy defect. The application of transforming growth factor-beta1 to this model resulted in significantly more ectopic bone (p < 0.01) outside the defect on the dural and periosteal surfaces. Basic fibroblast growth factor, in the dose used, appeared to have an inhibitory effect on new bone formation fostered by negatively charged Sephadex beads. This study suggests that the addition of transforming growth factor-beta1 to the known osteoconductive matrix of negatively charged Sephadex beads may be therapeutically useful in nonhealing bony defects.

Journal Article↗
PubMedDate not supplied

Chondrocyte-to-osteocyte transformation in grafts of perichondrium-free epiphyseal cartilage.

When perichondrium-free pieces of embryonic quail epiphyseal cartilage are incubated on the chorioallantoic membranes of chick embryos, 2 developmental changes are observed. First, most grafts develop a periosteum in which the osteoblasts and osteocytes are of donor, i.e., chondrocytic origin. No such periosteum is observed around explants of demineralized, inductive bone matrix. Second, the matrix surrounding some chondrocytes within the original graft became more bone-like with respect to staining pattern, birefringence and collagen morphology. We conclude that, under some conditions, the avian chondrocyte may in situ or subsequent to release from the cartilage lacuna synthesize a bone-like matrix and, in this sense, be thought to have undergone a "transformation" into an osteocytic or osteoblastic type of cell.

Allantois↗
PubMedDate not supplied

The effect of varus stress on the moving rabbit knee joint.

Unicompartmental osteoarthritis was produced by applying varus stress to moving rabbit knee joints. Degenerative changes were confined to the medial tibial and the medial femoral articular surfaces. Within the range of varus stress used, duration appears to be more important than magnitude of varus stress in determining the severity of cartilage damage. The calcified zone remained histologically unchanged despite advanced changes in the noncalcified zone superficial to the tidemark. Intrachondral degenerative cysts were frequently found in the basilar layers of the noncalcified cartilage adjacent to the tidemark where shear stresses were likely to be highest and diffusible nutrients least available. Highly cellular cartilaginous tissue was noted in the subchondral marrow spaces in the specimens with advanced cartilage degeneration. These areas appeared to be continuous with the overlying degenerated cartilage through gaps in the calcified cartilage. Subchondral bone did not show remarkable trabecular thickening despite advanced degenerative changes in the articular cartilage.

Animals↗
PubMedDate not supplied

Burn-associated bone disease in sheep: roles of immobilization and endogenous corticosteroids.

To determine the role of immobilization in the pathogenesis of burn-associated bone disease, we selected the sheep as a model to study the effects of burn injury compared with a sham-burned control group. Seven of the sheep were subjected to controlled 40% flame burn, and seven underwent anesthesia with arterial and venous cannulation but without burn. After labeling newly formed bone with tetracycline and calcein, the sheep were killed 2 weeks after burn or sham burn, and the iliac crest and lumbar vertebrae were analyzed for histomorphometry. Analysis failed to demonstrate a significant reduction of bone formation rate in the burned sheep. Osteoid area and surface and osteoblast surface, which correlated significantly with bone formation rate (r = 0.49, p < 0.025), were reduced in the burned sheep. Results suggest that immobilization may play a primary role in the pathogenesis of burn-associated bone disease, but the presence of differences in other histomorphometric features indicates the bone disease is multifactorial.

Adrenal Cortex Hormones↗
PubMedDate not supplied

Winner of the AlbertTrillat Young Investigator Award. The effects of aggressive notchplasty on the normal knee in dogs.

We assessed the possible association between an aggressive intercondylar notchplasty and histopathologic, radiographic, and gait changes to the knee. Three groups of six adult greyhounds were observed for 6 months. Group I dogs had a sham operation. Group II dogs had a 4-mm notchplasty of the lateral femoral condyle where it articulates with the lateral tibial spine. Group III dogs had a 7- to 8-mm notchplasty of the lateral femoral condyle to simulate the long-term effects of an overly aggressive notchplasty. Force plate gait analyses were not significantly different for any dogs at 3 and 6 months. Histopathologic studies (hematoxylin and eosin and safranin O stains) revealed notchplasty area remodeling with a thin layer of lamellar bone covered by fibrous connective tissue. Both Group II and III dogs had significant loss of lateral femoral condyle and trochlear groove articular surface proteoglycans. The radiographic notch width index remained unchanged throughout the study for Group I; the indexes increased immediately after surgery in Groups II and III because of the notchplasty, but after 6 months these values returned to near-preoperative measurements. An aggressive intercondylar notchplasty caused articular cartilage histopathologic changes at 6 months consistent with those found in knees with early degenerative arthritis. Significant refilling of a non-impinged notchplasty occurred by 6 months after surgery. Our results raise concern about the effects of aggressive intercondylar notch widening in humans.

Analysis of Variance↗
PubMedDate not supplied

3-D femoral stress analysis using CT scans and p-version FEM.

The potential of the finite element method as a computational aid for making objective clinical decisions has not yet been exploited due to the unreliability of the results obtained. The main reasons for this may be attributed to the poor quality of the finite elements available in the conventional softwares, improper modeling of the three dimensional problem, and errors introduced by incorrect representation of geometry and material properties. Herein, we report an attempt to derive a three-dimensional finite element model for the adult human femur which permits reliable representation of the local stress patterns. The geometry was obtained by serial computed tomography scans. The mechanical properties were based on laboratory tests and information available in the literature. The analysis is performed with a new generation software. Preliminary results suggest that the scheme could be automated and used for in vivo analysis.

Biomechanical Phenomena↗