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Biomedical subjects

R C Thompson

Publications and source records attributed to R C Thompson.

At least 199 records · Page 11Linked to original sources
PubMed1993

Fractures in large-segment allografts.

Sixteen of thirty-five large-segment allografts that had been implanted after resection for neoplastic conditions, and had been followed for a minimum of thirty-six months, were found to have fractured at a mean of twenty-six months after the implantation. Thirteen of the fractures were treated operatively, and we found a lack of vascularization and soft-tissue attachments to the graft at the fracture site. For seven fractured grafts, there were radiographic and clinical signs of union with the host bone. Eight of the sixteen grafts that had fractured were salvaged with one or more autogenous bone grafts, and two healed spontaneously. Thus, twenty-nine of the thirty-five grafting procedures were considered to have been successful in that the initial objective--provision of a functional segment for skeletal replacement--had been achieved. Multivariate analysis revealed a significant correlation for fracture in patients who were receiving chemotherapy when internal fixation of the graft had included devices that penetrated the cortices of the graft (p < 0.05).

Adolescent↗
PubMed1993

Deformity following fracture in diabetic neuropathic osteoarthropathy. Operative management of adults who have type-I diabetes.

We studied fifteen lower extremities that had a deformity following a fracture in the region of the ankle or the tarsal bones, in fourteen adults who had type-I diabetes and neuropathic osteoarthropathy. The skeletal deformities associated with these fractures were either diagnosed late (two limbs) or occurred in lower extremities that had been treated by means other than non-weight-bearing and immobilization (thirteen limbs). All deformities were severe and secondary to a non-union or malunion of the fracture; all were ultimately treated with operative reconstruction. Before the reconstruction, the limbs had had either persistent ulceration associated with an uncorrectable skeletal deformity (four) or a severe deformity that was difficult to contain with a custom-made orthosis (eleven). The most recent result was considered a success when the ulceration had healed, the involved foot was planti-grade, and the involved limb was capable of bearing weight with use of a patellar tendon-bearing orthosis. Following reconstruction, ten patients had a plantigrade foot without ulceration, three had a plantigrade foot with a persistent draining ulcer, and one had a foot that was not plantigrade. In the limbs that had an ulcer at the time of the operation, there was one successful outcome and three failures. In contrast, the outcome was successful for ten of the limbs that had not had an ulcer and a failure for one. There were three complications following sixteen operative reconstructive procedures in the fourteen patients, including one infection and two instances of accelerated bone resorption and collapse.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Morphological characterization of adult Echinococcus granulosus as a means of determining transmission patterns.

Host induced changes in morphological characters of the rostellar hooks of Echinococcus granulosus were used to determine the origin of infection in definitive hosts in rural areas of southeastern Australia where wild and domestic cycles of transmission may interact. The morphological characters studied vary depending on the species of intermediate host (macropod marsupials, sheep) in which protoscoleces develop, and these characters are retained in adult worms. It was therefore possible to determine whether definitive hosts (dingoes and foxes) acquired infection by consuming protoscoleces of E. granulosus from macropods or from sheep. The results correlated well with the known distribution of intermediate hosts and illustrate the practical value of such morphological markers in epidemiological studies.

Animals↗
PubMed1993

Histochemical and immunohistochemical characterization of cells constituting the giant cell tumor of bone.

Enzymatic activity and cell membrane proteins were characterized in cells from five giant cell tumors of bone (GCTs). Naphthyl alpha esterase (NAE) and acid phosphatase (AP) activity was noted within both the mononuclear and multinucleated cells of each tumor. In each tumor, all mononucleated cell populations displayed tartrate-sensitive AP activity, whereas the multinucleated cell populations demonstrated variable expression of tartrate-sensitive and tartrate-resistant AP activity. Analysis of cell membrane proteins included attempts at immunodetection of mannose receptor, OKM-1 antigen (OKM-1a), colony-stimulating factor-1 receptor (CSF-1r), and platelet-derived growth factor receptor (PDGFr). None of these membrane antigens were elicited on multinucleated cells. In contrast, the mannose receptor, OKM-1a, and PDGFr all were detected on the mononucleated cells within each tumor. These data demonstrate that a population of mononucleated, not multinucleated cells, expresses features unique to mature mononuclear phagocytes and establishes the presence of a membrane receptor, PDGFr, associated with mitogenesis of mesenchymal cells.

Acid Phosphatase↗
PubMed1992

Failure of IL-1 receptor antagonist and monoclonal anti-IL-1 receptor antibody to inhibit antigen-specific immune responses in vivo.

rIL-1R antagonist (rIL-1ra) and 35F5, a neutralizing mAb, have been shown to inhibit the ability of IL-1 alpha and IL-1 beta to bind to type I but not type II murine receptors. Additionally, IL-1ra and 35F5 inhibit a variety of inflammatory responses in vitro and in vivo. In the present report we have evaluated the activity of human IL-1ra and 35F5 in murine Ag-specific cell-mediated and humoral immune response models. Administration of IL-1ra, either twice daily or as a continuous infusion, did not inhibit the cytolytic T lymphocyte response to allogeneic splenocytes. The CTL response was also not inhibited by daily administration of 35F5. The delayed type hypersensitivity response to oxazolone was similarly refractory to administration of IL-1ra and 35F5. In the humoral immune response models, neither the splenic plaque response to SRBC nor the IgG or IgM response to TNP-keyhole limpet hemocyanin was inhibited by treatment with IL-1ra or 35F5. These data suggest that signaling through the type I IL-1R is not required for these Ag-specific immune responses.

Animals↗
PubMed1992

Subchondral damage after acute transarticular loading: an in vitro model of joint injury.

Intact canine metacarpophalangeal and metatarsophalangeal joints were subjected to a variety of loads in vitro. Intraarticular fracture occurred in 19 joints loaded to an average force of 2.4 +/- 0.4 kN with a corresponding loading rate of 88 +/- 23 kN/s. The remaining 29 joints were without gross evidence of fracture with an average load and loading rate of 1.7 +/- 0.9 kN and 64 +/- 32 kN/s, respectively. In the fractured specimens, damage to the zone of calcified cartilage and subchondral bone was much more extensive than was initially evident by gross inspection when assessed by scanning electron microscopy. Cracks with associated step-off displacement at the zone of calcified cartilage were found distant to the gross fractures. These findings were confirmed histologically. In addition, cracks localized to the zone of calcified cartilage were commonly identified histologically in specimens loaded in the range of 1.9-2.8 kN, but were not grossly fractured. The contact area determined with pressure-sensitive film increased with increasing load up to the point of fracture. The average pressure generated at the articular cartilage surface at the time of fracture in this model is > or = 40 MPa, and the fracture occurred at the contact site. Our findings suggest that failure in acute transarticular loading begins in the zone of calcified cartilage and subsequently involves the subchondral bone and overlying cartilage. This type of injury may contribute to the development of osteoarthritis after intraarticular fracture, or at high loads that do not result in gross fracture.

Animals↗
PubMed1992

Comparative studies on the growth dynamics of two genetically distinct isolates of Giardia duodenalis in vitro.

The in vitro growth behaviour of the intestinal protozoan Giardia duodenalis was studied in detail and comparisons were made between two genetically and biologically distinct cloned isolates. Replicates of each clone were grown at six different initial cell concentrations and in culture media at four different pH values. Significant differences in in vitro growth were found between the two isolates, BAH12 and P1. BAH12 had a specific narrow pH requirement, with satisfactory growth only obtained at pH 6. The mean generation time of BAH12 at pH 6 between days 1 and 3 was 10.8 h, compared to an average of 6 h for the same period for P1, both at pH 6 and pH 7. Comparative health of cultures was assessed during both the pH and growth experiments using a suite of six variables. Consistent changes in the health of cultures over time were found to reflect growth behaviour over time. These results provide the first detailed evidence that genetically different isolates of Giardia may differ in such fundamental biological parameters as growth rate and pH requirements. These differences may have important epidemiological and taxonomic implications.

Analysis of Variance↗
PubMed1992

Albendazole as a future antigiardial agent.

Albendazole, one of the more recently developed of the benzimidazole carbamate anthelmintics, has the broadest spectrum of activity of the benzimidazoles released to date. In this article, Jim Reynoldson, Andrew Thompson and John Horton discuss the role of this drug in the fight against giardiasis.

Journal Article↗
PubMed1992

Interleukin-1 receptor antagonist (IL-1ra) as a probe and as a treatment for IL-1 mediated disease.

The natural human IL-1 receptor antagonist (IL-1ra) has been produced in a recombinant organism and has been used to study IL-1 action in vivo. The receptor antagonist mitigates the pathophysiology associated with animal models of ulcerative colitis through reducing IL-1 mediated neutrophil recruitment into the affected tissue. It also reduces joint swelling and damage in an animal model of rheumatoid arthritis, possibly by reducing IL-1 mediated synthesis of proteases by the synovial fibroblasts and chondrocytes of the joint. The receptor antagonist is not immunosuppressive in rodents, indicating that it is working by blocking the inflammatory reaction rather than any underlying defect in specific immunity.

Amino Acid Sequence↗
PubMed1992

The uptake and conversion of L-[U14C-] aspartate and L-[U14C-] alanine to 14CO2 by intact trophozoites of Giardia duodenalis.

1. Intact trophozoites of Giardia duodenalis (clone P1C10) took up and metabolised L-[U14C-] aspartate to 14CO2 at rates of 10.27 +/- 0.76 and 27.6 +/- 2.07 ng hr-1 10(-6) cells in a simple maintenance medium (MM) and in a complex bile supplemented (BIS-33) medium respectively. 2. Intact trophozoite of G. duodenalis (clone P1C10) also took up and metabolised L-[U14C-] alanine to 14CO2 at rates of 20.6 +/- 1.1 and 91.4 +/- 17.5 ng hr-1 10(-6) cells in the simple (MM) and complex (BIS-33) medium respectively. 3. trophozoite sonicates contained significant levels of aspartate-2-oxoglutarate transaminase (AST; EC 2.6.1.1) and alanine-2-oxoglutarate transaminase (ALT; EC 2.6.2.2.). Specific activities (at 23 degrees C) were 95.1 +/- 11.3 and 87.3 +/- 9.8 nmol (min)-1 (mg protein)-1 respectively. 4. These observations suggest that Giardia has the capacity to utilise aspartate and alanine and possibly other amino acids as alternative sources of energy. 5. The extrusion or uptake of alanine by Giardia trophozoites may be dictated by the intracellular redox-status of the protozoan parasite or components in the external mileu.

Alanine↗
PubMed1992

IL-1 receptor antagonist inhibits monocyte chemotactic peptide 1 generation by human mesangial cells.

The elicitation of neutrophils and monocytes from the circulation into the inflamed glomerulus is a key process in the pathogenesis of proliferative glomerulonephritis. The aim of this study was to determine the factors which regulate the expression and synthesis of the monocyte specific chemotaxin, monocyte chemotactic peptide 1 (MCP-1). Mesangial cells in culture did not constitutively express MCP-1, but could be induced to express both MCP-1 mRNA and antigenic MCP-1 by either stimulation with IL-1 alpha or TNF alpha, which are also stimuli for interleukin 8 (IL-8/NAP-1) expression and release. Pre-treatment of mesangial cells with the IL-1 receptor antagonist (IL-1ra) induced dose-dependent inhibition of both the expression of MCP-1 and IL-8 mRNA as well as the release of both chemotactic peptides in response to IL-1 alpha, while the receptor antagonist had no significant effect on TNF alpha induced MCP-1 and IL-8 generation. This study demonstrates that the IL-1 receptor antagonist was four times more effective at inhibiting the IL-1 induced expression and release of IL-8 compared to that of MCP-1. These results suggest that mesangial cell-derived MCP-1 may play an important role in the recruitment of monocytes in glomerular inflammation and that an IL-1 receptor antagonist may have therapeutic potential for the treatment of glomerulonephritis.

Base Sequence↗
PubMed1992

Muscle protein breakdown during endotoxemia in rats and after treatment with interleukin-1 receptor antagonist (IL-1ra).

The purpose of this study was to examine the effect of endotoxemia on muscle protein degradation and to test the hypothesis that muscle proteolysis during endotoxemia is regulated by interleukin-1 (IL-1). Both total and myofibrillar protein breakdown rates in incubated extensor digitorum longus muscles were increased after the subcutaneous injection of 0.1 or 1.0 mg/kg endotoxin in rats. The endotoxin-induced increase in muscle protein breakdown was blunted by IL-1 receptor antagonist, administered intraperitoneally at a total dose of 45 or 105 mg/kg. Results suggest that endotoxemia in rats gives rise to sepsislike changes in muscle protein breakdown. Increased muscle protein breakdown during endotoxemia may be regulated, at least in part, by IL-1.

Animals↗
PubMed1992

Rapid regulation of corticotropin-releasing hormone gene transcription in vivo.

Regulation of corticotropin-releasing hormone (CRH) gene expression in vivo was assessed via in situ hybridization histochemistry, using probes directed against an intronic sequence of the CRH gene. Initial characterization of the CRH intron (CRHin) probe revealed specific localization of signal to the nuclear compartment of neurons in the medial parvocellular paraventricular hypothalamus, which are known to produce CRH peptide and mRNA. Abundance of CRHin signal was low, commensurate with a low resting pool of CRH heteronuclear RNA (hnRNA), representing CRH primary transcript. Regulation of CRH hnRNA levels was assessed after acute glucocorticoid synthesis blockade by injection of metyrapone. Metyrapone inhibits the conversion of 11-deoxycorticosterone to corticosterone, thereby rapidly depleting glucocorticoids and serving as a discrete stimulus for hypothalamo-pituitary-adreno-cortical activation. Plasma hormone measurements verified the efficacy of treatment, as metyrapone-treated rats showed extremely low basal corticosterone levels at all postinjection time points, while exhibiting progressive increases in plasma ACTH release over the 60-min postinjection period. CRH hnRNA levels were markedly increased 15-30 min after metyrapone injection, consistent with a rapid induction of CRH gene transcription in response to the stimulatory event. CRH mRNA, on the other hand, did not exceed control levels until 60 min post metyrapone, illustrative of a temporal lag between transcriptional changes and detectable changes in mRNA pools. Additional sections from metyrapone-and vehicle-treated rats were hybridized with probes complementary to mRNA encoding the immediate-early gene c-fos. c-fos was not present under unstimulated conditions yet was rapidly induced upon metyrapone treatment or vehicle injection (15 min).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1992

Impending fracture associated with bone destruction.

In the patient with metastatic bone disease, destruction of bone threatens the structural support of the skeletal system. Osteoporosis, stress-risers, and the open-section effect result in pain, immobilization, and fractures. The establishment of more clear-cut indications for prophylactic fixation will lessen the morbidity associated with a pathologic fracture.

Bone Neoplasms↗