Search PubMed⌕ Search

Biomedical subjects

S D Cook

Publications and source records attributed to S D Cook.

At least 217 records · Page 12Linked to original sources
PubMed1986

Transcriptional map of the measles virus genome.

We have constructed a recombinant DNA library of the measles virus genome and identified gene-specific clones containing sequences coding for portions of each of the six viral structural proteins, as well as clones coding for intercistronic sequences. By Northern blotting, we could order the clones according to the pattern of individual gene-specific and readthrough mRNAs. Clones corresponding to the N, P/C and M genes were identified by correlation of the mRNAs with their in vitro translation products; clones corresponding to the H, F and L genes were identified by indirect evidence. The results indicated that the gene order in measles virus is that of a typical paramyxovirus (3'-N,P/C,M,F,H,L-5'), but that the M and F transcripts each contain 1.5 times the coding capacity needed for synthesis of these proteins in vivo.

Cloning, Molecular↗
PubMed1986

Herpes simplex virus type 1 persistence and latency in cultured rabbit corneal epithelial cells, keratocytes, and endothelial cells.

Cell cultures of rabbit corneal epithelium, keratocytes, and endothelium were used to determine the lytic cycle of herpes simplex virus type 1. Viral growth was fastest in epithelial cells. A novel HSV-1 in-vitro latency system was established in the three distinct cell types. Cell cultures were inoculated at low multiplicities of infection with HSV-1. Temperature manipulation alone was used to induce and reactivate latent HSV-1 infections. The presence of cellular stress proteins was demonstrated at supraoptimal temperatures. All cell types were capable of maintaining latent viral infections under these conditions. Viral persistence was present in 20% of epithelial cell cultures at supraoptimal temperatures, but not in keratocyte cultures or endothelial cell cultures.

Animals↗
PubMed1986

The effect of post-sintering heat treatments on the tensile properties of Ti-6A1-4V alloy.

Previous studies have shown that the application of a porous coating to a solid substrate offers several advantages over current methods of implant fixation. However, the heat treatments required to sinter porous metal coatings have also been shown to cause significant decreases in the mechanical properties of the substrate. With Ti-6A1-4V alloy, sintering above the material beta transus results in a transformation from the as-received, equiaxed microstructure, recommended for surgical implants, to a lamellar alpha-beta microstructure. This lamellar structure has been shown to have inferior mechanical properties. In the present study, microstructural analysis and mechanical testing were performed on Ti-6A1-4V alloy subjected to various post-sintering heat treatments in an attempt to improve the mechanical properties. The microstructures examined were a fine and a coarse acicular alpha in a retained beta matrix. Tensile tests were performed on specimens containing these structures and results were compared with the lamellar and equiaxed microstructures. The fine acicular alpha structure was shown to exhibit the best tensile properties for the post-sintering Ti-6A1-4V alloy microstructures examined, displaying a 9.8% elongation value, as compared to the as-received, equiaxed microstructure value of 13.5%. This represents a significant improvement over the 5.1% value obtained with the lamellar microstructure.

Alloys↗
PubMed1986

Bone remodeling associated with a flexible femoral intramedullary implant.

The tissue response and bone remodeling associated with a flexible femoral intramedullary implant was evaluated. The implant consisted of wafers of porous Co-Cr-Mo alloy and microporous LTI pyrolytic carbon. Six wafers of each material were assembled in a stack and held together using a central acrylic rod. Radiography and histology demonstrated that these implants were associated with gross bone remodeling changes in the femoral shaft. The bone remodeling consisted of endosteal surface bone resorption and periosteal surface bone deposition, most likely due to a loss of structural support from the reamed medullary canal. The periosteal surface bone deposition resulted in an increase in femoral shaft diameter of 5% - 140%. The bone-implant interface consisted of a fibrous connective tissue with limited areas of bone ingrowth or bone apposition.

Animals↗
PubMed1986

Particulate aluminum oxide as a bone graft material.

The performance of particulate aluminum oxide (Al2O3) as a bone graft material was evaluated by comparison to two other graft materials, autogenous bone and particulate hydroxylapatite (HA). Holes were drilled through the medial cortex of both the distal femora and proximal tibiae in three dogs. The Al2O3, HA and autogenous bone were packed into the created defects and the rate and extent of defect healing examined. Particulate Al2O3 and HA were also placed on opposite sides of the median sacral crest in a spinal fusion procedure. One dog was sacrificed at 4, 8 and 12 weeks post-operative. The extent and rate of healing was superior with the autogenous bone, while the performance of the HA was superior to that of the Al2O3 at 4 and 8 weeks. However by 12 weeks, the performance of the two non-autogenous materials was equivalent. At 12 weeks the majority of the cancellous defect was infiltrated with viable bone with all three materials. In the spinal fusions, results were not as encouraging, with less bone present within the graft materials as compared to the cancellous defect implantations.

Aluminum↗
PubMed1986

Atraumatic osteolysis of the distal clavicle: histologic evidence of synovial pathogenesis. A case report.

Osteolysis of the distal clavicle was diagnosed in a young male athlete following many years as a baseball pitcher with a supplementary weightlifting program. There was no history of ligamentous injuries, contusions, fractures or separation of the acromioclavicular joint. As such, this case was categorized as "atraumatic" osteolysis. Non-decalcified histologic sections from the resected clavicle suggest that the pathogenesis of this atraumatic osteolysis arose from the synovium.

Adolescent↗
PubMed1986

The effect of the radial head and prosthetic radial head replacement on resisting valgus stress at the elbow.

Five fresh nonembalmed elbows were tested for resistance to valgus stress in their anatomic state, after radial head resection, and after insertion of Silastic and polymethylmethacrylate (PMMA) radial head replacements. The resistance to valgus stress was found to be reduced an average of 28% after radial head resection. The PMMA and Silastic implants restored valgus stiffness an average of 86% and 78% respectively, as compared to intact elbow values for corresponding flexion angles. Testing in pronation, supination and neutral forearm rotation demonstrated no difference in valgus stiffness. For each elbow, resistance to valgus stress was greatest at full extension and dropped approximately 30% at all other flexion angles as compared to corresponding full extension value. These data support the concept of the radial head as a stabilizer to valgus stress in the in vitro elbow. Further, this data demonstrated the ineffectiveness of current radial head replacement systems in restoring this biomechanical function and suggest that the use of a stiffer implant material may be beneficial in resisting valgus stress. Additional testing is indicated to determine the performance of a stiffer implant at the clinical and biological levels.

Adult↗
PubMed1986

Herpes simplex virus in the cornea; an ultrastructural study on viral reactivation.

Infectious HSV was isolated from the corneal disc of a patient with chronic stromal keratitis. A morphological study was performed on the corneal tissue after detection of HSV by organ culture. The characteristic features of HSV replication were observed within the keratocytes, including formation of nucleocapsid structures; encapsidation of viral DNA; envelopment and egress of virons. The following effects of viral replication upon cells were seen, margination and condensation of nuclear chromatin, formation of aberrant viral structures, re-duplication of nuclear membranes and cellular destruction. This study demonstrates that HSV replication occurs within keratocytes. HSV replication is an important step in the evolution of disciform herpetic keratitis.

Adult↗
PubMed1986

Histologic and microradiographic analysis of a revised porous-coated anatomic (PCA) patellar component. A case report.

A retrieved uncemented, porous-coated human patellar component was evaluated histologically and microradiographically. The metal portion of the component and porous coating were made of cobalt--chromium-based alloy. Because of adhesive capsulitis and inadequate knee flexion, the patient had revision surgery 11 months after the original total knee arthroplasty. Clinically, the device was not grossly loose. Contact microradiography of the porous material showed no calcified tissue ingrowth. Undecalcified histologic sections demonstrated only fibrous tissue ingrowth, with obvious bone-resorptive activity as well as numerous multinucleated giant cells adjacent to the porous metal.

Bone and Bones↗
PubMed1986

Potential role of paramyxoviruses in multiple sclerosis.

At the present time, the cause of multiple sclerosis (MS) remains unknown, although it seem likely that one or more infectious agents triggers the disease, perhaps through an autoimmune mechanism. In this article, evidence linking the paramyxoviruses, canine distemper, and measles to MS is reviewed.

Animals↗
PubMed1986

Upper extremity proprioception in idiopathic scoliosis.

Twenty-three patients with idiopathic scoliosis were tested for upper extremity proprioceptive function. All subjects had documented progression of deformity, with an average curvature of 34 degrees. The average ages for scoliotics and 18 control subjects were 16.1 and 20.8 years, respectively. Controls had no spinal deformity and underwent identical test procedures. The test results showed that scoliotic subjects had significant asymmetry between right and left limbs in their threshold for detection of joint motion (p less than or equal to 0.005) and in their ability to reproduce angles to which their elbow joint had been previously positioned (p less than or equal to 0.025). Slight asymmetry also was observed in the reproduction tests of the control group (p less than or equal to 0.013); however, there was no significant asymmetry seen in this group for the threshold test. Performance of bilateral limbs was designated good and bad for both groups; the limb that performed better in proprioceptive function was designated good limb. Analysis of data showed that the scoliotics' good and bad limbs performed inferiorly in both threshold and angle reproduction tests when compared with normal controls. The results of this study imply, but do not localize, a neurologic deficit in scoliotic patients.

Adolescent↗
PubMed1986

Metallurgical analysis of five failed cast cobalt-chromium-molybdenum alloy hip prostheses.

The clinical and metallurigical characteristics of five cast cobalt-chromium-molybdenum alloy femoral hip prostheses which failed in vivo were evaluated. The devices included: two of the Howmedica Muller-Charnley design, two of the Howmedica Charnley design, and one of the Zimmer Aufranc-Turner design. Fractographic analyses demonstrated that the five devices had failed by fatigue which originated on the lateral aspect. Failure occurred after an average in vivo time of 80.4 months (approximately 6.7 years). Only two of the devices had Rockwell hardness values that were within the ASTM specifications for the alloy. Upon metallurgical examination, moderate to severe levels of gas porosity, interdendritic shrinkage, and nonmetallic inclusions were found in all of the devices. As expected, extremely large grain sizes also were observed in the devices examined. These results indicate that the metallurgical flaws and defects associated with the cast cobalt-chromium-molybdenum alloys used in these devices may preclude successful longterm performance and warrant manufacturer's attention.

Aged↗
PubMed1985

The effect of surface treatments on the interface mechanics of LTI pyrolytic carbon implants.

A mechanical and histological evaluation of LTI pyrolytic carbon implants was undertaken to determine the effect of various surface treatments on the retention characteristics of the implants. Five types of surfaces were evaluated, including as-deposited, fine grit-blasted, coarse grit-blasted, ground, and plasma oxygenated. The four surface treatments were chosen in an attempt to emulate the morphology of the as-deposited implants. The implants were evaluated in vivo by placement transcortically in the femora of adult mongrel dogs for periods of 12 to 24 weeks. Although the as-deposited implants exhibited the greatest interface strength at 12 weeks the results of mechanical testing after 24 weeks implantation indicated no statistically significant difference among the interface strength values or among the interface stiffness values of the implants. The histologic response of the implants was similar; while all implants exhibited areas of direct implant-bone apposition, the as-deposited implants exhibited this behavior to the greatest extent. Thus the ability to duplicate the biological response to the as-deposited LTI carbon surface appears possible by one or more of the treatments evaluated.

Animals↗
PubMed1985

An evaluation of variables influencing implant fixation by direct bone apposition.

A systematic mechanical and histologic evaluation of design variables affecting bone apposition to various biocompatible materials was undertaken. The variables investigated included material elastic modulus, material surface texture, as well as material surface composition. The implant materials included polymethylmethacrylate (PMMA), low-temperature isotropic (LTI) pyrolytic carbon, commercially pure (C.P.) titanium, and aluminum oxide (Al2O3). Implant surface texture was varied by either polishing or grit-blasting the various materials. Implant surface composition was varied by applying a coating of ultra-low temperature isotropic (ULTI) pyrolytic carbon to the various implants. A total of 12 types of implants were evaluated in vivo by placement transcortically in the femora of adult mongrel dogs for a period of 32 weeks. Following sacrifice, mechanical push-out testing was performed to determine interface shear strength and interface shear stiffness. The results obtained from mechanical testing indicate that for implants fixed by direct bone apposition, interface stiffness and interface shear strength are not significantly affected by either implant elastic modulus or implant surface composition. Varying surface texture, however, significantly affected the interface response to the implants. For each elastic modulus group the roughened surfaced implants exhibited greater strengths than the corresponding smooth surfaced implants. Undecalcified histologic evaluation of the implants demonstrated that the roughened implants exhibited direct bone apposition, whereas the smooth implants exhibited various degrees of fibrous tissue encasement. Thus, for implants utilizing direct bone apposition fixation, it appears that of the parameters investigated, implant surface texture is the most significant.

Aluminum Oxide↗