PubMed Health⌕ Search

Biomedical subjects

R A Metcalfe

Publications and source records attributed to R A Metcalfe.

At least 37 records · Page 2Linked to original sources
PubMed1994

Stimulation of extraocular muscle fibroblasts by cytokines and hypoxia: possible role in thyroid-associated ophthalmopathy.

OBJECTIVE: Smoking is a risk factor for the development of thyroid-associated ophthalmopathy, an inflammatory process primarily affecting the fibroblasts in extraocular muscles. We wished to determine whether the extraocular muscle fibroblasts are more sensitive than dermal fibroblasts to T-cell derived cytokines, as a reason for this anatomical localization, and whether hypoxia alters fibroblast function, as one explanation for the susceptibility conferred by smoking. DESIGN: Fibroblasts derived from the skin or extraocular muscles of healthy subjects were cultured with cytokines under normal (5% CO2:95% air) and hypoxic (5% CO2:95% N2) conditions. MEASUREMENTS: Glycosaminoglycan, protein and DNA synthesis were measured by assessing incorporation of D-6-3H-glucosamine, 3H-amino acids, and 3H-thymidine respectively. RESULTS: alpha-interferon and interleukin-6 had no effect on fibroblasts. gamma-interferon, tumour necrosis factor and interleukin-1 stimulated glycosaminoglycan synthesis; this effect was greater in orbital than in dermal fibroblasts with gamma-interferon and interleukin-1 (P < 0.05). The same cytokines stimulated total protein with a greater response in orbital fibroblasts with gamma-interferon. Interleukin-1 inhibited DNA synthesis in orbital fibroblasts but stimulated DNA synthesis in dermal fibroblasts (P < 0.01); tumour necrosis factor also displayed a differential effect (P < 0.01). Hypoxia caused a significant increase in glycosaminoglycan, protein and DNA synthesis in both types of fibroblasts, under both basal and cytokine-treated conditions (P < 0.05). CONCLUSIONS: Extraocular muscle fibroblasts respond differently from dermal fibroblasts following cytokine stimulation, which may explain in part the anatomical localization of ophthalmopathy. Hypoxia stimulates fibroblasts and this could contribute, as an enhancing factor, to the adverse effects of smoking on thyroid eye disease.

Cells, Cultured↗
PubMed1994

Immunoglobulin class and subclass distribution of eye muscle and fibroblast antibodies in patients with thyroid-associated ophthalmopathy.

OBJECTIVE: The investigation of the antibody response in thyroid-associated ophthalmopathy (TAO) using different antigens and assays has given inconsistent results. We have analysed antibodies against eye muscle and control antigens in a large group of TAO patients to assess whether specific eye muscle antibodies exist in TAO. We have also evaluated the presence of IgA and IgM class antibodies and examined IgG subclass distribution. DESIGN: Sera were obtained from all patients (TAO, Graves' disease without ophthalmopathy and Hashimoto's thyroiditis) within one year of diagnosis. Sera were also collected from healthy controls, with no family history of autoimmune thyroid disease. PATIENTS: Thirty-eight patients had Graves' disease with Grade III or greater TAO; 15 patients had Graves' disease without ophthalmopathy and nine had Hashimoto's thyroiditis without any eye signs. The control group consisted of 14 subjects. MEASUREMENTS: Antibodies against porcine eye and skeletal muscle, human eye (membrane and soluble antigen) and skeletal muscle, human thyroid microsomal and thyroglobulin antigens and dermal and orbital fibroblast antigens were assessed using ELISA. Antibody isotypes and IgG subclasses were studied for porcine and human eye muscle antibodies. Eye muscle (porcine and human) and orbital fibroblast antibodies were further analysed by immunoblotting. RESULTS: There were no significant differences in the ability of either IgG or IgA in sera from the different groups to bind porcine and human eye muscle antigens. There was a significant correlation (P < 0.0001) between the binding to porcine eye muscle and skeletal muscle antigens (for both IgG and IgA). There was no difference between sera from TAO patients and control subjects in their binding to eye muscle fibroblasts for both IgG and IgA antibodies. However, IgA antibody activity against dermal fibroblasts differed significantly between TAO patients and controls (P < 0.05). By immunoblotting, the frequency of IgA antibodies recognizing 21 kDa (40% of patients) and 62 kDa (52%) bands in porcine eye muscle blots and 20, 24 and 38 kDa bands in blots of human eye muscle (soluble) antigen differed significantly between patients with TAO and controls (P < 0.05 in all cases). IgG antibodies recognizing 80 and 92 kDa bands in blots of the subcellular membrane antigen prepared from orbital fibroblasts were found more frequently in patients with TAO compared with controls (P < 0.05 in both cases). CONCLUSIONS: We found no evidence that eye muscle membrane or fibroblast antibodies are present in a significant proportion of TAO patients, using ELISAs based on antigens prepared from several sources. We have also failed to demonstrate the presence of previously described specific, TAO-associated antibodies, including those directed against a 64 kDa protein in eye muscle and a 23 kDa protein in fibroblasts. IgA class antibodies reactive with orbital components appeared to be more strongly associated with TAO than those of the IgG class, though even this relationship is weak. These results suggest that antibodies are of secondary importance in the pathogenesis of TAO, which is most likely a T cell-mediated disorder.

Animals↗
PubMed1994

Expression of the costimulatory molecule B7/BB1 in autoimmune thyroid disease.

Efficient antigen presentation requires the provision of a costimulatory signal, the best characterized of which is B7/BB1. It is unclear whether thyroid cells expressing class II molecules can present autoantigens to T cells, although this has been suggested as an important mechanism in the initiation of Graves' disease and Hashimoto's thyroiditis. We have found that thyroid cells from patients with thyroid autoimmunity do not express B7/BB1 in vivo or in vitro, even after activation with the cytokines interleukin-1 or gamma-interferon, or with a phorbol ester. Increased numbers of CD20+ B cells and CD14+ dendritic cells expressing B7/BB1 were found in intrathyroidal lymphocyte preparations from such patients compared to peripheral blood. These results suggest that conventional antigen-presenting cells rather than thyroid cells provide B7/BB1 costimulatory activity in autoimmune thyroid disease, and argue against a role for the thyroid cells themselves in autoantigen presentation to T cells via the B7/BB1 pathway.

Antigens, CD↗
PubMed1993

Analysis of fibroblast-stimulating activity in IgG from patients with Graves' dermopathy.

Conflicting results have been reported on the effect of IgGs from patients with Graves' dermopathy on dermal fibroblast function. We have analyzed 14 dermopathy IgGs prepared by protein G affinity chromatography. These caused FRTL-5 thyroid cells to synthesize significantly greater amounts of glycosaminoglycans (GAG) and protein than IgGs from normal controls (p < 0.05). [3H]Thymidine incorporation was also significantly increased (p < 0.05) and there was a significant correlation between all three parameters and the ability of these IgGs to stimulate iodide incorporation (p < 0.001). Dermopathy and control IgGs caused a modest increase in GAG synthesis by dermal fibroblasts but there was no significant difference between the two types of IgG. Increased GAG production was detectable in both culture medium and the extracellular matrix, and there was no difference between fibroblasts derived from the arm and leg. Conditioned medium from thyroid cells treated with dermopathy or control IgGs caused a greater increase in GAG production than the IgGs alone, but again there was no difference between the two sources of IgG. Neither control nor dermopathy IgG affected fibroblast protein synthesis or [3H]thymidine incorporation. Our results argue against a role for circulating IgGs in mediating Graves' dermopathy and make it unlikely that the TSH receptor antibodies are acting directly on a functional receptor expressed by dermal fibroblasts in this disorder.

Cell Line↗
PubMed1993

Adhesion molecule monoclonal antibodies inhibit experimental autoimmune thyroiditis.

To examine the role played by adhesion molecules in thyroid autoimmunity, we have assessed the effect of administering monoclonal antibodies (mAb) against intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) in experimental autoimmune thyroiditis, induced by immunizing rats with thyroglobulin in complete Freund's adjuvant. The antibody against LFA-1, but not against ICAM-1, reduced thyroglobulin antibody production (P < 0.01) and both antibodies caused a significant reduction (P < 0.002) in the severity of the thyroidal lymphocytic infiltration. In vitro, both mAb impaired the proliferative response of splenic and lymph node T cells to thyroglobulin, but only the antibody against LFA-1 reduced thyroid cell killing assessed using splenic lymphocytes as effectors. Monoclonal antibodies against both these adhesion molecules appear to inhibit cell-mediated autoimmunity in vivo, but only the LFA-1 mAb reduced the autoantibody response.

Animals↗
PubMed1992

A simple bioassay for epidermal growth factor using pig thyrocytes.

A bioassay for epidermal growth factor (EGF) is described using an eluted stain assay (ESTA) of dehydrogenase activity in pig thyrocytes. Optimal responsiveness to EGF was obtained in confluent cultures of primary pig thyrocytes cultured with EGF or biological samples containing EGF for either 24 or 48 h. Dehydrogenase activity was determined by measuring the production and then the release of a coloured formazan product produced by reduction of a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide substrate added to the cells. The assay responded equally to mouse, human and recombinant EGF and was suitable for measuring EGF activity in some but not all biological fluids. Specificity of detection of EGF activity was confirmed using antibody to EGF. The ESTA assay compared favourably with the radioreceptor assay for EGF in terms of sensitivity to EGF with half-maximal activation at 0.24 +/- 0.06 nmol/l (mean +/- S.E.M., n = 22 experiments) for the ESTA assay and 0.60 +/- 0.13 nmol/l (n = 7 experiments) for the radioreceptor assay.

Animals↗
PubMed1991

The visual defect in multiple sclerosis and optic neuritis. A combined psychophysical and electrophysiological investigation.

Chromatic and achromatic visual function were investigated using psychophysical and evoked potential techniques in 32 patients with multiple sclerosis (MS) or optic neuritis. There was no evidence for either chromatic or achromatic vision being selectively damaged. There was, however, some evidence that demyelination of the optic nerve causes a visual defect in which the transmission of high temporal frequencies is imparied. In some patients either a red or blue deficit was evident, but overall there was no evidence of a wavelength specific colour vision defect in our patient group. Reduction of chromatic sensitivity as determined psychophysically had a statistically significant correlation with the amplitude and latency of the chromatic visual evoked potential.

Adult↗
PubMed1990

The secretory characteristics of epidermal growth factor in human saliva.

A series of unstimulated and stimulated saliva samples from healthy volunteers was tested for EGF by radioimmunoassay. Salivary EGF, like other salivary constituents, was secreted in a diurnal pattern. On stimulation the rate of EGF secretion doubled but the concentration fell by 70% because of dilution by salivary fluid. EGF secretion was positively related to saliva flow (p = 0.00001) but the coefficient of correlation was low (r = 0.47). Over a period of 30 min continual salivary stimulation, EGF was released in a bimodal pattern with peaks occurring at 3 and 12 min. Subsequently, EGF secretion remained stable at a rate of release that was approx. 80% of the initial peak value (7.4 ng/min). Chromatography indicated that both high and low molecular-weight forms of EGF were present in unstimulated and stimulated saliva and that the low-weight form predominated. However, the proportion of high molecular-weight EGF increased from 18 to 38% of the total on short-term (3 min) stimulation.

Adolescent↗
PubMed1989

Rheumatoid arthritis and motor neurone disease--an association?

Three patients with rheumatoid arthritis and motor neurone disease are presented. The neurological syndrome supervened after 2, 19 and 23 years of polyarthritis and led to death within 4 years. The diagnosis of motor neurone disease was confirmed at post mortem in one case. Common immunological mechanisms may account for this previously unreported association.

Adult↗
PubMed1988

Genetic factors in myasthenia gravis: a family study.

We studied forty-four patients with myasthenia gravis (MG) and their families. Thirty percent of patients had a confirmed family history of autoimmune disease; in one case this was MG. In all the families with autoimmune disease, the affected relatives were related to the patients through the maternal line. HLA-B8 and DR3 were increased in patients due to the high incidence of these antigens in female, nonthymoma patients with onset before 40 years. HLA-B5 was increased in patients with older onset. The haplotype A1-B8-DR3 was not found to be increased given the presence of B8 or DR3.

Adolescent↗
PubMed1987

The incidence of craniocervical bony anomalies in the adult Chiari malformation.

Detailed linear, angular and surface area measurements were undertaken on the lateral skull radiographs of 32 patients with proven idiopathic adult Chiari type 1 malformation. Basal angles were larger, the clivus was shorter and Klaus' index was reduced in patients compared to normal controls. The size of the posterior fossa was smaller in patients than in controls. By discriminant analysis of the skull X-ray data it was possible to identify correctly two thirds of patients as belonging to the patient group. The findings indicate that craniocervical bony anomalies in the adult Chiari malformation are commoner than was previously realised, and they support the view that tonsillar herniation in these patients results from bony occipital dysplasia.

Adolescent↗
PubMed1986

Magnetic resonance imaging in syringomyelia.

The aim of the study was to assess the reliability of magnetic resonance imaging (MRI) in the detection of syrinx cavities and to determine the proportion of cavities associated with Chiari malformation. MRI was performed in over 120 patients with neurologic deficits referable to the cranio-cervical junction. Forty-one patients were also evaluated by CT myelography (CTM). CTM demonstrated appearances consistent with intramedullary cavitation in 14 patients. MRI detected 11 of these but in 3 the appearances, including cord size, were normal. In the entire study 27 syrinx cavities were demonstrated by MRI, 8 associated with trauma, posterior fossa or spinal tumours, or spinal dysraphism. Of the remaining 19, tonsillar ectopia was present in 10 (53%). It is concluded that a lack of concordance between MRI and CTM exists in the detection of small cavities in the normal sized cord, and that syringomyelia without evidence of tonsillar ectopia is identifiable by MRI more frequently than might be anticipated.

Adolescent↗