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Biomedical subjects

K W Marshall

Publications and source records attributed to K W Marshall.

At least 19 recordsLinked to original sources
PubMed1999

Comparative study of normal and osteoarthritic canine synovial fluid using 500 MHz 1H magnetic resonance spectroscopy.

High resolution 1H nuclear magnetic resonance spectroscopy has been used to investigate and compare the metabolic profiles of normal and osteoarthritic synovial fluids in a canine model of osteoarthritis. The spectra of osteoarthritic synovial fluid showed (a) increased concentrations of lactate, pyruvate, lipoprotein-associated fatty acids, and glycerol as well as the ketones hydroxybutyrate and hydroxyisobutyrate, (b) reduced levels of glucose, and (c) elevated levels of N-acetylglycoproteins, acetate, and acetamide compared with healthy normal canine synovial fluid. An increase was also observed in the concentrations of the amino acids alanine and isoleucine. These results suggest that (a) the intraarticular environment in canine osteoarthritis is more hypoxic and acidotic than in a normal joint, (b) lipolysis may play an increasingly important role as a source of energy in osteoarthritis, and (c) the N-acetylglycoprotein polymer component of synovial fluid (mostly hyaluronan) seems to be increasingly fragmented and degraded into acetate by way of an acetamide intermediate with progressive osteoarthritis. The observed changes in the biochemical profile of canine osteoarthritic synovial fluid may be useful in understanding alterations in joint metabolism consequent to arthritic diseases and helpful in identifying potential markers of osteoarthritis.

Animals↗
PubMed1999

1H NMR investigation of changes in the metabolic profile of synovial fluid in bilateral canine osteoarthritis with unilateral joint denervation.

OBJECTIVE: High resolution 1H-nuclear magnetic resonance (NMR) techniques have been used to compare the effects of unilateral knee-joint denervation on the biochemical profiles of synovial fluid in a bilateral canine model of osteoarthritis. METHOD: Paired synovial fluid samples were obtained from seven dogs all of which had previously undergone bilateral anterior cruciate ligament transection, unilateral knee denervation and contralateral sham nerve exposure. All synovial fluid samples were then analyzed using 500 MHz 1H-CPMG spin-echo NMR Spectroscopy to assess differences in endogenous metabolite levels between the paired fluids. RESULTS: The results indicate statistically significant increases in glycerol, hydroxybutyrate, glutamine/glutamate, creatinine/creatine, acetate and N-acetyl-glycoprotein concentrations in synovial fluids from denervated with respect to control knees. Furthermore, significant trends towards elevated lactate, alanine and pyruvate levels in the denervated knee fluids are consistent with our previous findings comparing NMR spectroscopy metabolic profiles of normal and osteoarthritic canine synovial fluids. CONCLUSION: This study lends support to the principle of neurogenic acceleration of OA in that the observed differences in metabolite concentrations found in the denervated knee fluids seem to correlate with metabolic changes resulting from aggravation of the OA process caused by joint denervation.

Animals↗
PubMed1999

Practical implications of cyclooxygenase-2--specific inhibitors in orthopedics.

Nonsteroidal anti-inflammatory drugs (NSAIDs) lead to severe and unpredictable side effects that are costly for individuals and the economy overall. As baby boomers enter their osteoarthritis years, there will be an increasing demand for safe and effective arthritis therapies. Animal and human data suggest that celecoxib, a cyclooxygenase-2-specific inhibitor, will provide an efficacious treatment without the side effects of conventional NSAIDs. Clinicians will need to determine individually and collegially how best to incorporate this new class of drugs into comprehensive treatment algorithms.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1998

Resurfacing of articular cartilage explants with genetically-modified human chondrocytes in vitro.

OBJECTIVE: We are attempting to genetically-modify chondrocytes transplanted to cartilage in vitro as a prelude to gene therapy trials in patients with osteoarthritis. DESIGN: With human cartilage and chondrocytes, we have explored the duration of binding of chondrocytes to cartilage in vitro and the expression of the beta-galactosidase gene introduced into the chondrocytes through infection with an adenoviral vector both before and after transplant of the chondrocytes to cartilage. RESULTS: Transplanted chondrocytes continued to bind to cartilage explants at 45 days in our longest trial. We could successfully infect chondrocytes with adenovirus at least 35 days after we transplanted the chondrocytes to cartilage. Expression of the beta-galactosidase gene continued throughout the duration of each trial. CONCLUSIONS: These results raise the possibility of repairing and rebuilding cartilage by resurfacing the cartilage with genetically modified chondrocytes. The ability to infect chondrocytes well after transplant raises the possibility of repeated infections of surface chondrocytes as an alternative to repeated injections of chondrocytes into the joint space.

Adenoviridae↗
PubMed1998

Lymphoproliferative disorders: CT findings in immunocompromised children.

OBJECTIVE: The objective was to evaluate the CT imaging appearance, distribution of disease, type of immunocompromised state, and outcome of children with Epstein-Barr virus-induced lymphoproliferative disorders. MATERIALS AND METHODS: Medical records and imaging studies (from four tertiary children's medical centers) were reviewed for pathologically proven cases of lymphoproliferative disorders in patients less than 20 years old. Trends between the CT imaging appearance, distribution, and type of immunocompromised state and prognosis were noted and analyzed with Fisher's exact test. RESULTS: Twenty-seven cases were identified (mean age, 7 years 8 months). Eighteen children had undergone solid organ transplantation (heart, n = 9; liver, n = 7; kidney, n = 2), and four had undergone bone marrow transplantation. Five patients had primary immunodeficiencies. The CT appearance of lymphoproliferative disorders varied and included lymphadenopathy, focal mass or masses, and diffuse infiltration and enlargement of organs without focal mass. The distribution of disease included abdomen (n = 17), chest (n = 10), neck (n = 8), and brain (n = 1). In eight of nine heart transplant recipients, the disease predominantly involved the chest and neck, whereas in all seven liver transplant recipients, the disease was isolated to the abdomen (p = .001). The overall mortality rate of 44% was less related to anatomic extent (multiorgan, 46%; localized, 43%) than to type of immune dysfunction (p = .001): bone marrow transplantation (100%), primary immunodeficiency (80%), heart transplantation (55%), liver transplantation (0%), and kidney transplantation (0%). CONCLUSION: Lymphoproliferative disorders in children had a variable distribution, imaging appearance, and outcome. However, in recipients of solid organ transplants, the disease tended to occur in the anatomic region of the transplant. Mortality rates were more closely related to the type of underlying immune dysfunction than to distribution of disease.

Bone Marrow Transplantation↗
PubMed1998

Air bag-related deaths and serious injuries in children: injury patterns and imaging findings.

BACKGROUND AND PURPOSE: As of November 1, 1997, automotive air-bag deployments occurring in low-speed collisions had resulted in the deaths of 49 children and in the serious injuries of 19 children in the United States. The purpose of this study was to investigate the patterns of injury occurring in this new mechanism of pediatric trauma. METHODS: In search of common patterns of injury, three pediatric radiologists retrospectively evaluated the available autopsy and imaging studies in 11 such cases not previously reported in the medical literature, in addition to three published case studies. RESULTS: The cause of death or serious injury in every case was the direct result of neurologic injury. Injury patterns differed according to the child's age and type of restraint used at the time of collision. Crush injury to the skull predominated in infant victims traveling in rear-facing child safety seats, and both cranial and cervical spine trauma occurred in older children traveling restrained, improperly restrained, or unrestrained in the vehicle's front passenger seat. CONCLUSION: Air-bag systems pose a potentially fatal threat to the front-seat child passenger. This is directly related to the biomechanics at impact placing the child closer to the deploying air bag. An understanding of the biomechanics provides the radiologist insight into the two types of injury patterns observed.

Air Bags↗
PubMed1997

A single capsaicin injection partially depletes neuropeptides but does not ameliorate inflammation severity in established feline antigen induced arthritis.

OBJECTIVE: To investigate the effect of the neuropeptide depleting agent capsaicin on neuropeptides in both synovial and nonsynovial articular tissues and on the relative degree of joint inflammation in established antigen induced arthritis (AIA). METHODS: AIA was created in both knees in 3 cats. Once AIA was established, the left knee of each animal received a single 0.5 ml injection of capsaicin (0.3 mg/ml). Three days later, the knees were harvested and dissected into 11 regions. Eleven articular cartilage tissues from both the experimental (capsaicin) and control (non-capsaicin) knees were examined for the immunocytochemical presence of substance P (SP) and calcitonin gene related peptide (CGRP). Additionally, the synovium was examined to determine the severity of joint inflammation. RESULTS: Nerve fibers immunoreactive for SP or CGRP were found in all 11 tissues in each of the non-capsaicin treated AIA knees. Both perivascular and "free" SP and CGRP immunoreactive fibers were present in all 11 articular structures. In the knees treated with capsaicin, however, 48% of the joint tissues examined completely lacked SP immunoreactivity, while 12% had no CGRP immunoreactivity. Inflammatory disease severity was not ameliorated by the single intraarticular injection of capsaicin used in this study. CONCLUSION: These data indicate that SP and CGRP immunoreactivity is maintained in synovial and nonsynovial articular tissues of non-capsaicin treated knees during subacute joint inflammation. In the capsaicin treated AIA knees, however, there was partial neuropeptide depletion. Nerve fibers containing SP were more sensitive to the peptide depleting effects of capsaicin than were CGRP positive fibers. Depletion of SP and CGRP from some joint tissues did not correlate with a decrease in joint inflammation. Studies incorporating a broad range of dosages will be required to determine whether intraarticular treatment with capsaicin can effectively deplete neuropeptides and thereby ameliorate established inflammatory arthritis.

Animals↗
PubMed1996

Isolation of picomolar affinity anti-c-erbB-2 single-chain Fv by molecular evolution of the complementarity determining regions in the center of the antibody binding site.

We determined the extent to which additional binding energy could be achieved by diversifying the complementarity determining regions (CDRs) located in the center of the antibody combining site of C6.5, a human single-chain Fv (scFv) isolated from a non-immune phage library which binds the tumor antigen c-erbB-2. CDR3 of the light (V(L)) and heavy (V(H)) chain variable region of C6.5 were sequentially mutated, the mutant scFv displayed on phage, and higher affinity mutants selected on antigen. Mutation of V(L) CDR3 yielded a scFv (C6ML3-9) with a 16-fold lower Kd (1.0 x 10(-9) M) than C6.5. Due to its length of 20 amino acids, four V(H) CDR3 libraries of C6ML3-9 were constructed. The greatest increase in affinity from a single library was ninefold (Kd = 1.1 x 10(-10) M). Combination of mutations isolated from separate V(H) CDR3 libraries yielded additional ninefold decreases in Kd, resulting in a scFv with a 1230-fold increase in affinity from wild-type C6.5 (Kd = 1.3 x 10(-11) M). The increase in affinity, and its absolute value, are comparable to the largest values observed for antibody affinity maturation in vivo or in vitro and indicate that mutation of V(L) and V(H) CDR3 may be a particularly efficient means to increase antibody affinity. This result, combined with the location of amino acid conservation and substitution, suggests an overall strategy for in vitro antibody affinity maturation. In addition, the affinities and binding kinetics of the single-chain Fv provide reagents with potential tumor targeting abilities not previously available.

Alanine↗
PubMed1996

Endurance-trained and untrained skeletal muscle bioenergetics observed with magnetic resonance spectroscopy.

Resting and submaximal isometric exercise 31P magnetic resonance spectroscopy (MRS) was carried out on 7 endurance-trained males (26.0 +/- 3 yrs) and 7 sedentary males (27.0 +/- 4 yrs). Spectral analysis provided peak areas of phosphocreatine (PCr), inorganic phosphate (Pi), adenosine triphosphate (ATP), and the chemical shift of Pi relative to PCr. The ratio of PCr/Pi was moderately lower during rest (preexercise p = .13, postexercise p = .18), and significantly higher during exercise (p < .05) in the trained subjects. Intracellular pH patterns were the same for both groups; a transient alkalosis was observed at the onset of exercise with a return to resting levels after 2 min. Differences suggest improved ATP resynthesis rate in the trained subjects during exercise. Intracellular pH changes can be attributed to the utilization of hydrogen ions that accompany PCr hydrolysis during work. The findings are congruent with previous reports indicating a superior oxidative capacity in trained skeletal muscle.

Adenosine Triphosphate↗
PubMed1996

Arthroscopic anterior cruciate ligament transection induces canine osteoarthritis.

OBJECTIVE: To determine whether arthroscopic anterior cruciate ligament (ACL) transection in the canine knee can be an effective alternative method for creating canine osteoarthritis (OA). METHODS: Six adult dogs underwent arthroscopic examination of the left knee with a 2.7 mm 30 degrees fiberoptic arthroscope. The articular surfaces of the femoral condyles, tibial plateaus, and patella were examined for evidence of OA. The ACL was directly visualized and transected. Care was taken to avoid iatrogenic articular cartilage injury. The animals were sacrificed 2 to 6 months after ACL transection. Both the ACL transected and ACL intact knees from each animal were assessed for gross pathology and histology. RESULTS: The dogs experienced minimal perioperative pain and rapidly returned to their preinjury level of activity. Gross and histological examination of articular cartilage confirmed this approach induced OA in every ACL transected knee. No contralateral ACL intact knee developed degenerative OA changes. CONCLUSION: Arthroscopic ACL transection is an effective method for creating canine OA. This approach has several methodological advantages relative to other techniques.

Animals↗
PubMed1996

Bilateral canine model of osteoarthritis.

OBJECTIVE: To determine whether bilateral arthroscopic anterior cruciate ligament (ACL) transection creates symmetrical osteoarthritis (OA) in canine knees. METHODS: Six dogs underwent bilateral arthroscopic ACL transections. The animals were sacrificed at intervals ranging from 2 to 12 months post ACL transection. Both knees in each animal were assessed for gross pathology, histology, and biochemistry. RESULTS: The limited invasiveness of arthroscopic ACL transection allowed bilateral ACL transections to be performed with minimal animal morbidity. Gross pathological, histological, and biochemical assessments of bilaterally ACL transected canine knees consistently confirmed the induction of OA changes in both knees. Of note, there was no significant difference in the degree of articular cartilage degeneration created in each pair of knees. CONCLUSION: Bilateral ACL transection induces symmetrical canine knee OA. This approach provides a potent model for investigating fundamental OA mechanisms and therapeutic approaches, since one knee can be experimentally manipulated while the other knee is used as a control. This allows each animal to be its own internal control, avoiding the interanimal variability associated with the unilateral canine OA model.

Animals↗
PubMed1995

Prediction of peptide affinity to HLA DRB1*0401.

A method to predict quantitatively peptide binding to HLA DRB1*0401 has been developed using a data set of the relative contributions of each of the naturally occurring amino acids in the context of a simplified peptide back-bone. The prediction assumed that the relative role of each of the peptide side chains could be treated independently and could be measured by assaying each of the 20 naturally occurring amino acids at the central 11 positions of a 13-residue peptide previously shown to contain the minimal requirements for high-affinity binding to HLA-DR proteins. The resultant database was shown to have predictive value when tested on a set of 13 unrelated peptides known to bind DRB1*0401 with a wide range of apparent affinity. The database was tested further by analyzing myelin basic protein. All 13 amino acid peptides containing a hydrophobic amino acid at the third position were synthesized and assayed for binding purified DRB1*0401. In every case, the measured affinity correlated with the predictive values within the experimental error of the assays. Finally, the ability to predict peptide binding to MHC class II molecules was shown to help in identifying T cell determinants. The specificity of DRB1*0401-restricted T cell hybridomas against human serum albumin corresponded to two peptides, predicted and shown to bind the class II protein with high affinity.

Amino Acid Sequence↗
PubMed1995

Quantitation of articular cartilage using magnetic resonance imaging and three-dimensional reconstruction.

A quadrature knee coil was used in conjunction with a magnetic resonance imaging scanner for quantitation of test phantom volumes, ex vivo bovine cartilage thickness, and in vivo human articular cartilage volumes. Optimal magnetic resonance parameters were obtained by testing a series of spin-echo and gradient-echo pulse sequences to determine the sequence that provided the highest resolution of articular cartilage and best defined the cartilage interfaces with synovial fluid and subchondral bone. Extensive testing revealed that two sequences were required to define articular cartilage accurately: a spoiled gradient-echo sequence and a steady state free-precession sequence. Three-dimensional reconstruction and statistical analyses of test phantoms and of bovine and human cartilage images were performed. Differences between actual phantom volumes and three-dimensional measurements demonstrated that, as magnetic resonance slice thickness was increased, the measurement variability also increased (coefficient of variation ranging from 1.7 +/- 1.3% for 1.0 mm slice thickness to 22.7 +/- 1.9% for 3.0 mm slice thickness). When the phantom volume was greater than 1,800 mm3, the intraobserver, interobserver and interscan accuracies were greater than 97, 98, and 96%, respectively. This high degree of reproducibility pertained for the data on in vivo human cartilage data also. For experienced observers, the intraobserver and interobserver reproducibility were greater than 98 and 97%, respectively. The interscan reproducibility was greater than 98%. These data demonstrate that improved magnetic resonance pulse sequencing, in conjunction with three-dimensional reconstruction and measurement techniques, can accurately and reproducibly measure the volume of articular cartilage. Clinical application of this approach offers the potential for early diagnosis of osteoarthritis and for serial, noninvasive assessment of changes in articular cartilage volume in response to therapeutic modalities.

Adult↗
PubMed1995

Prediction of peptide affinity to HLA DR molecules.

A method to quantitatively predict peptide binding to HLA DRB1*0401, B1*0101, and B1*1501 has been developed using a dataset of the relative contributions of each of the naturally occurring amino acids in the context of a simplified peptide backbone. The prediction assumed that the relative role of each of the peptide sidechains could be treated independently and could be measured by assaying each of the twenty naturally occurring amino acids at the central eleven positions of a 13 residue peptide previously shown to contain the minimal requirements for high affinity binding to HLA DR proteins. Three separate databases were generated. They were shown to have predictive value when tested on a set of 13 unrelated peptides known to bind the DR proteins with a wide range of apparent affinity. The DRB1*0401 database was tested further by analyzing myelin basic protein. All 13 amino acid peptides containing a hydrophobic amino acid at the third position were synthesized and assayed for binding purified DRB1*0401. In every case, the measured affinity correlated with the predictive values within the experimental error of the assays. Finally, the ability to predict peptide binding to MHC class II molecules was shown to help in identifying T cell determinants. The specificity of DRB1*0401 restricted T cell hybridomas against human serum albumin corresponded to two peptides, predicted, and shown to bind the class II protein with high affinity.

Amino Acid Sequence↗