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Biomedical subjects

D G Allan

Publications and source records attributed to D G Allan.

12 recordsLinked to original sources
PubMed2000

Multidrug resistance-1 gene expression does not increase during tumor progression in the MGH-OGS murine osteosarcoma tumor model.

In addition to its possible role in drug resistance, expression of the multidrug resistance-1 gene may also be associated with a more malignant phenotype and tumor progression. This study evaluated its expression during tumor progression in the MGH-OGS transplantable murine osteosarcoma tumor model. Three variables of tumor progression were analyzed: tumor size, local recurrence, and metastasis. With a highly sensitive reverse transcription-polymerase chain reaction method, mRNA levels of multidrug resistance-1 were compared in primary tumors of different sizes. In addition, the levels were compared in primary, locally recurrent, and metastatic tumors isolated from individual mice. No significant difference was found in the levels of expression with increasing primary tumor size. In addition, the levels in primary, locally recurrent, and metastatic tumors were not significantly different. Our results indicate that--at least in the MGH-OGS tumor model, which is analogous to the majority of spontaneously occurring human osteosarcomas in that it has low levels of multidrug resistance-1/P-glycoprotein and is sensitive to doxorubicin--there is no evidence of upregulation of multidrug resistance-1 expression during tumor progression.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Meniscal transplantation and degenerative articular change: an experimental study in the rabbit.

Over the past several decades, scientific evidence has substantiated the vital role of the meniscus in the function of the knee. Using a modified Mankin method, this study evaluated the efficacy of immediate and delayed meniscal transplantation to prevent the degenerative articular changes seen after medial meniscectomy. Significantly fewer degenerative changes occurred in the articular cartilage from New Zealand white rabbits receiving a meniscal transplantation immediately after meniscectomy when compared with control animals killed 3 months after meniscectomy (P < .05). Rabbits who received a delayed transplantation 3 months after meniscectomy and were killed at 6 months, showed significantly fewer degenerative changes in the articular cartilage compared with control animals killed 6 months (P < .05) or 3 months (P < .05) after meniscectomy. These studies show that both immediate and delayed meniscal allograft transplantation offer some initial protection to the cartilaginous surfaces of the knee following meniscectomy. These studies also suggest that delayed meniscal transplantation may reverse initial postmeniscectomy degenerative changes for the short term.

Animals↗
PubMed1995

Complex acetabular reconstruction for metastatic tumor.

Twenty-six hips were reconstructed in 25 patients with periacetabular metastatic lesions. Twelve hip reconstructions were performed using a modified Harrington technique with polymethyl methacrylate, cancellous screws, and reinforcement rings (type I). Fourteen hip reconstructions were performed using bulk bone-graft and reinforcement rings (type II). According to the Musculoskeletal Tumor Society functional rating score, there was no appreciable difference between the two types of reconstructions. Either technique can give satisfactory results depending on the anatomic location and extent of bone loss. Careful patient selection is the prime determinant of a successful outcome.

Acetabulum↗
PubMed1994

Fresh osteochondral allografts for advanced giant cell tumors at the knee.

Sixteen patients with advanced giant cell tumors presenting at the knee were treated with complete tumor resection and reconstruction using fresh osteochondral allografts. All patients had one or more of the following indications for tumor resection (as opposed to curettage): tumor recurrence, pathologic fracture, or destruction of the subchondral bone plate. At the 3-15-year follow-up period (mean, 9 years), two grafts have been revised to second fresh grafts because of fracture and one graft has been converted to an allograft-implant composite reconstruction. One joint was fused because of late infection. Functional assessment was carried out in 13 patients, and 8 were good or excellent, 4 were fair, and 1 was poor. The authors conclude that the fresh osteochondral allograft is a viable treatment alternative to prosthetic arthroplasty in advanced, benign, aggressive bone tumors.

Adult↗
PubMed1993

[Fresh osteochondral transplants in the treatment of advanced giant cell tumors].

Eighteen patients with advanced giant cell tumors were treated with complete tumor resection and reconstruction using fresh osteochondral allografts. All patients had one or more of the following indications for tumor resection (as opposed to curettage): tumor recurrence, pathological fracture, or destruction of the subchondral bone plate. At the 4- to 16-year follow-up (mean 9 years), two grafts were revised to a second fresh graft because of fracture, one graft was converted to an allograft implant composite and two joints were fused because of infection. The functional results were assessed in 14 patients: 9 were good or excellent, 4 fair and 1 poor. We conclude that the fresh osteochondral allograft is a viable treatment alternative to prosthetic replacement in advanced benign, aggressive bone tumors.

Adult↗
PubMed1993

Bone grafts in hip replacement surgery. The pelvic side.

Replacement arthroplasty of the hip may require restoration of bone stock to provide support for the acetabular implant and to restore anatomy and leg lengths. This article discusses the indications, surgical technique, results, and controversies of using bulk autograft bone to provide cup support for primary hip replacement in hip dysplasia. In addition, the use of allograft bone to restore bone stock in the revision situation is covered. The indications, surgical technique, and results of the use of both morsellized and bulk allograft bone are presented.

Acetabulum↗
PubMed1993

Revision arthroplasty of the proximal femur using allograft bone.

Revision arthroplasty of the hip may require restoration of bone stock on the femoral side to provide bone support for the new implant and restore anatomy and leg length. Large cortical defects can be reconstructed best with allograft bone because of the quality and quantity of the bone required. In this article, the surgical technique and results of cortical allograft as full circumferential and cortical strut grafts are presented.

Adult↗
PubMed1991

Proximal femoral allografts in revision hip arthroplasty.

We followed prospectively 69 patients with 78 proximal femoral allografts performed for revision of total hip arthroplasty for an average of 36 months (range 29 to 68). Large fragment proximal femoral allografts and cortical strut allografts were successful in 85%. Grafts smaller than 3 cm in length (calcar grafts) were clinically successful in 81%, but 50% underwent significant radiographic resorption. We conclude that large proximal femoral allografts and cortical strut allografts provide dependable reconstruction of bone stock deficiencies during revision total hip arthroplasty.

Adult↗
PubMed1990

Vertebral end-plate failure in porcine and bovine models of spinal fracture instrumentation.

The use of mature porcine and immature bovine spines as models for the assessment of spinal fracture instrumentation is commonplace. By comparing the load-displacement characteristics of these spine segments and observing the fracture type, this study investigated the tendency of immature bovine spines to fail prematurely at the vertebral physis, disrupting biomechanical evaluation of spinal fracture fixation devices. Load to failure of the spines was determined using the Instron Universal Testing Machine and a specially designed endcap. In axial compression, the 10-16-week-old calf spines failed at 12,845 +/- 1,466 N, compared with mature pig spines at 17,300 +/- 5,170 N (p less than 0.05). Axial compression with flexion caused consistent failure through an end-plate in both species: 995 +/- 156 N for the calf spines and 2,025 +/- 575 N for the porcine spines (p less than 0.005). It was concluded that the tendency for immature bovine spines to fail more readily at the cartilaginous end-plate makes the calf spine a less desirable model.

Aging↗
PubMed1988

Off-road recreational motor vehicle accidents: hospitalization and deaths.

There is increasing concern over the unregulated use of recreational off-road motor vehicles. A review of 207 patients admitted to a tertiary care hospital over a 5-year period, as well as deaths due to use of recreational vehicles, elicited the following information. Recreational accidents predominantly involved men in their mid-twenties. Children younger than 16 years were more frequently involved in all-terrain vehicle (ATV) or dirt-bike accidents and constituted more than one-third of the total. There was a ninefold increase in ATV accidents over the study period, so that by 1985 ATVs were the primary cause of off-road injuries (52%). The musculoskeletal system was most frequently injured (66%) followed by the head and face (25%). There was permanent disability in 10.6%, and 33% of the recreational deaths were in children younger than 16 years. The inherent instability of ATVs was confirmed by the finding that in 60% of accidents the vehicle had rolled or flipped. Stricter licensing requirements should be implemented, and public education is required to draw attention to the danger of these vehicles, particularly to children. There is a need for proper safety equipment and driver training. The issue of vehicle design must also be addressed by the industries concerned.

Accidents↗