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Biomedical subjects

D G Murray

Publications and source records attributed to D G Murray.

At least 19 recordsLinked to original sources
PubMed1992

A gene associated with cell division and drug resistance in Giardia duodenalis.

A 3000 bp cDNA insert (G6/1) from Giardia duodenalis, cloned into Escherichia coli is located on chromosome 3 of Giardia stocks which have 3 chromosomes detectable by field-inversion gel electrophoresis in the range 650-800 kb and on chromosome 3 and/or 4 of stocks with 4 chromosomes in this size range. The loss of this sequence from chromosome 4 but not chromosome 3 was associated with the induction of drug resistance in a previously sensitive laboratory stock. G6/1 appears to represent a single copy gene in Giardia as determined by hybridization of the probe to cleaved genomic DNA. Furthermore, the sequences flanking at least 12 kb of G6/1 are the same when G6/1 appears on both chromosomes 3 and 4. The cDNA encodes a protein associated with the nuclei of trophozoites during some stages of growth of the parasite. In a non-dividing culture, the antigen is associated with the nuclei of about 30% of trophozoites and fewer in a dividing culture. Three Giardia stocks with obvious chromosome rearrangements, which grow poorly and fail to divide normally, apparently lack the DNA sequence G6/1.

Animals↗
PubMed1992

Knee extensor mechanics after subtotal excision of the patella.

Two sets of six fresh frozen autopsy specimens were used to test the quadriceps force requirements for knee extension after sequential distal-to-proximal and proximal-to-distal excisions of the patella. The quadriceps force as a function of knee flexion angle was recorded for varying amounts of excision and compared with the results for total patellectomy. Excision of the proximal one half or less resulted in lower force requirements when compared with total patellectomy. The effects of removal of the proximal three-fourths length of patella were inconsistent and actually increased the force requirements in three knees. The effects of distal to proximal excisions indicate a biomechanical advantage to maintaining a fragment equal to at least three fourths the length of the proximal patella. Retaining a fragment of adequate size preserves at least some of the mechanical advantage provided by the intact patella.

Aged↗
PubMed1990

Blood products: optimal use, conservation, and safety.

A review of our experience in total joint arthroplasty revealed that the cell saver was not cost-effective in the case of routine primary hip or knee replacement. Its use should be restricted to cases of revision hip and knee surgery in which infection has been ruled out. Preoperative aspiration remains the most reliable method for accomplishing this. However, if the aspiration is negative and the intra-articular fluid obtained at the time of surgery is suspicious for infection, either in appearance or on Gram stain or cell count, it is best to abandon use of the cell saver. Predonation should be routine for all hip replacement cases unless there are specific contraindications. In general, there is good acceptance of this program by patients, although a few have specifically indicated they would prefer to run the risk of homologous transfusion. Two units available for primary replacement are more than ample. In cases of revisions, a first revision justifies a minimum of 3 units. For complex revision cases involving patients with three or more previous procedures on the hip, or those requiring significant bone resection or large segment grafting, the maximum possible number of units should be obtained. Autologous blood reinfusion should be done for essentially the same indications as homologous transfusion even though risks are sharply reduced. The local source for autologous collection will then follow its own specific protocol for the disposition of remaining units. In every case, the surgical technique should be careful and directed toward limiting intraoperative blood loss.

Blood Transfusion, Autologous↗
PubMed1986

Mechanical factors in electrode-induced osteogenesis.

Previous experiments have suggested that mechanical activity of electrode implants may contribute to the observed bone formation that has been attributed to the electrical currents. This was tested by implanting movable and stationary wires in the medullary canal of the rabbit femora or tibiae. The moving implants uniformly showed significant medullary bone formation at the wire, whereas the stationary ones did not. This bone persisted for as long as 8 weeks and was mostly resorbed by 12 weeks as the implants became fixed. The new trabecular bone closely resembled that typically seen at electrically active implants. Implant motion may have a more important role in electrically induced osteogenesis than previously thought.

Animals↗
PubMed1986

In vivo construction of a metal-backed, high-molecular-weight polyethylene cup during McKee-Farrar revision total joint arthroplasty. A case report.

The need for revision total hip arthroplasty after metal-to-metal articulating prostheses is well known. An alternative to conventional acetabular revision in the clinical circumstance of isolated femoral component loosening is in vivo construction of a metal-backed, high-molecular-weight polyethylene (HMWPE) acetabular component. This surgical approach reduces the likelihood of intraoperative acetabular bone loss, should minimize subsequent loosening, and virtually eliminates the source of metallic wear debris. Follow-up evaluation after 3 years revealed maintenance of the acetabular component position and a satisfactory clinical result. In vivo construction of a metal-backed HMWPE acetabular component is an effective alternative in the management of this potentially difficult orthopedic problem.

Acetabulum↗
PubMed1986

Experience with the variable axis knee prosthesis.

In an evaluation of 245 variable axis total knee arthroplasties, no significant deterioration of results were found five to nine years after implantation. The patellar problems originally reported diminished with the use of a patellar button, widening of the flange on the femoral component and the increased use of lateral retinacular release. The local complications were: severe patellar problems, 6.9%; ligamentous laxity, 2.9%; aseptic loosening, 1.2%; deep infections, 2.0%; supracondylar fractures, 1.2%; peroneal nerve palsy, 1.6%.

Aged↗
PubMed1985

Complications of Variable Axis total knee arthroplasty.

Three hundred seventy-six patients were treated by a Variable Axis total knee arthroplasty between 1974 and 1980 and were reviewed for mechanical and orthopedic complications of their surgery. Sixty-five patients had significant complications. Twenty-eight (7.4%) patients developed significant problems with their patellae, 13 (3.4%) patients required reoperation for patellar realignment, and four (1.0%) patients had a patellar resurfacing for retropatellar pain. Two (0.5%) cases of aseptic loosening of the femoral component required revision surgery. There was no aseptic loosening of the tibial component. Other complications included a ligamentous instability (2.9%), postoperative joint stiffness (1.6%), peroneal nerve palsy (1.3%), supracondylar fractures (1.0%), and postoperative joint infection (1.8%).

Femoral Fractures↗
PubMed1978

The influence of design on the transmission of torque across knee prostheses.

Knee prostheses of eight different designs were tested experimentally to determine the axial torque necessary to rotate the tibial component relative to the femoral component with the prosthesis positioned at or near full extension. The results represent transmitted torque as a function of axial rotation. For six designs, the transmitted torque was 11.3 newton-meters (100 inch-pounds) or greater at 6 degrees of rotation, with an axial load of 1556.8 newtons (350 pounds). These prostheses either had close conformation between femoral and tibial components, or were mechanically linked. In these prostheses, the geometry of the articulating surfaces was the primary determinant of torque. For the other two types, under similar loading conditions the transmitted torques were 2.5 newton-meters (twenty-two inch-pounds) at 6 degrees of rotation. These prostheses were designed to allow greater freedom for rotation, and hence for them the primary determinant of torque was friction between the articulating surfaces. The predictive value of this torque characteristic relative to the incidence of loosening will have to be determined by comparison with clinical experience.

Biomechanical Phenomena↗
PubMed1977

Herbert total knee prosthesis: combined laboratory and clinical assessment.

We tested the Herbert knee prosthesis, which was designed to restore intrinsic stability with limited degrees of freedom for rotation to severely damaged or deformed knees, in a knee simulator. These tests indicated a tendency for the prosthesis to fracture through the medial femoral housing after cycling for the equivalent of one to three years of normal use. In a clinical series of thirty-five knees treated with the prosthesis, there were five failures similar to those produced by laboratory testing. On the basis of this combined study, the Herbert prosthesis appears to have design characteristics that seriously limit its usefulness for long-term knee replacement. Testing in a knee simulator in this case appeared to be a valid predictor of clinical failure.

Biomechanical Phenomena↗
PubMed1975

An ultrastructural study of the biocompatibility of poly(2-hydroxyethyl methacrylate) in bone.

Because of the unique properties for swelling in a fluid medium and variable modulus of elasticity, hydrophilic methacrylates may be of potential usefulness for implanting prosthetic devices in bone. To investigate the biocompatibility, electron micrographic studies were done on specimens of poly(2-hydroxyethyl methacrylate) imbedded in bone for varying periods of time. Ultrastructural examination revealed progressive ossification of surrounding connective tissue up to the tissue polymer junction over a 6 month period. There was no evidence of inflammatory response. Based upon this study, it would appear that bone adjusts to an implant of hydrophilic methacrylate by ossification to the implant junction. This supports continued studies into the usefulness of this material as an implant.

Acrylates↗