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Biomedical subjects

D R Robinson

Publications and source records attributed to D R Robinson.

At least 109 records · Page 6Linked to original sources
PubMed1978

The effects of anti-inflammatory drugs on prostaglandin production by rheumatoid synovial tissue.

The effect of anti-inflammatory drugs on prostaglandin production by rheumatoid synovial tissue has been investigated. Synovial explants were maintained in tissue culture for periods up to six days and PGE2 concentrations in culture were determined by radioimmunoassay. The more potent nonsteroidal inhibitors of PGE2 production and their IC50 (micrometer) values were indomethacin 0.005, flufenamic acid 0.2, flurbiprofen 0.6, ibuprofen 2.0 , naproxen 6.0, phenylbutazone 10.0, and aspirin 20.0. Drugs with weak or insignificant effects were hydroxychloroquin, acetaminophen, azathioprine, chloroquin, penicillamine, gold Na thiomalate, and Na salicylate. Glucocorticoids were potent inhibitors; dexamethasone 0.003, prednisolone 0.01, hydrocortisone 0.03; while mineralocorticoids deoxycorticosterone and aldosterone were inactive at 1.0 micrometer. There is a reasonably good correlation between the IC50 concentrations of the nonsteroidal inhibitors and their peak free plasma concentration achieved during therapy in man. Inhibition of prostaglandin synthesis may contribute to the effects of many but not all anti-inflammatory drugs.

Adrenal Cortex Hormones↗
PubMed1977

Prostaglandin production by rheumatoid synovial cells: stimulation by a factor from human mononuclear Cells.

Human peripheral blood mononuclear cells (lymphocyte-monocyte) in culture release a solube factor which can stimulate, up to 200-fold, production of prostaglandin E2 by isolated, adherent, rheumatoid synovial cells. Production of the factor by the mononuclear cells is enhanced by phytohemagglutinin. This factor is similar in apparent mol vt (10,000-20,000) to that which also stimulates collagenase production by the same cells.

Arthritis, Rheumatoid↗
PubMed1976

Production of collagenase and prostaglandins by isolated adherent rheumatoid synovial cells.

We have studied cells dispersed with proteolytic enzymes from rheumatoid arthritic synovectomy specimens to determine the cell type(s) responsible for joint destruction. Initially 10-50% of these cells adhered to culture dishes within 24 hr and were of two main types: small, round cells and larger, stellate cells. During 1-4 days of culture, 5-25% had Fc receptors and 25-50% showed brisk phagocytosis. Daily producition, per 10(6) cells of collagenase (EC 3.4.24.3) (after trypsin pretreatment) was up to 70 mug of collagen fibrils lysed per min at 37 degrees (70 units), of prostaglandin (PGE2), up to about 1200 ng, and of lysozyme, up to about 100 mug. Under identical conditions of assay, fibroblasts grown from explants of synovium produced no detectable collagenase or lysozyme, and PGE2 was only 2-4 ng. With the dispersed cell preparations, macrophage markers (Fc receptors and lysozyme) were undetectable after 4 days and PGE2 decreased rapidly after about 7 more days. However, collagenase production continued for 3-25 weeks, and in some cultures, after cell passage. At these later stages, large, slow-growing stellate cells were predominant and could phagocytose carbon particles if incubated for greater than 6-8 hr. Indomethacin (14 muM) inhibited PGE2 but stimulated collagenase production whereas dexamethasone (10 nM) inhibited both. Production of PGE2 and collagenase in large amounts in vitro by these cells suggests that they may be involved in joint destruction in vivo. The precise origin of these synovial cells and the mechanisms responsible for the sustained production of collagenase at a high rate remain unidentified.

Arthritis, Rheumatoid↗
PubMed1975

Prostaglandins in the rheumatic diseases.

The prostaglandins may participate in the pathogenesis of the inflammatory rheumatic diseases by acting as mediators of inflammation and in promoting bone resorption. Levels of PGB (presumed to arise from PGE) in synovial fluids are elevated in the majority of a group of patients with inflammatory rheumatic diseases, as compared to similar patients treated with aspirin and indomethacin and patients with osteoarthritis. Rheumatoid synovium produces large amounts of PGE2 in organ culture. In addition, fibroblast cell lines derived from rheumatoid synovia synthesize more PGE and more cAMP than do cells from normal synovia or skin. The media from rheumatoid synovial organ cultures contain large quantities of bone-resorbing activity toward mouse calvaria in vitro. The bone resorption can be accounted for by PGE2 produced by the synovia, because the activity and PG synthesis are inhibited by more than 90% by incubation of the tissue with indomethacin, because it is quantitatively extractable into ether, and because it bears a relationship to the concentrations of PGE2 present, as measured by radioimmunoassay.

Arthritis, Rheumatoid↗
PubMed1975

Prostaglandin synthesis by rheumatoid synovium and its stimulation by colchicine.

The synthesis of prostaglandins by rheumatoid synovial tissue in organ culture was studied utilizing radioimmunoassay, with antisera to PGB1, PGF1alpha and PGF2alpha. It was established that PGE2 and PGF2alpha were the major prostaglandins formed by analyses of culture media with the two antisera to PGF, before and after alkali treatment. Indomethacin at 5 mug/ml suppressed prostaglandin synthesis, usually to less than 1% of control cultures. Colchicine, 0.1 mug/ml resulted in marked stimulation of prostaglandin synthesis, in some cases over 10 fold. It is suggested, because of the colchicine effect, that the state of the microtubules may regulate the rate of prostaglandin biosynthesis. It is possible that prostaglandin E2 produced by rheumatoid synovia may contribute to the pathogenesis of the inflammatory reaction and lead to destruction of juxta-articular bone in rheumatoid arthritis.

Arthritis, Rheumatoid↗
PubMed1975

Prostaglandin-stimulated bone resorption by rheumatoid synovia. A possible mechanism for bone destruction in rheumatoid arthritis.

Synovial tissue from patients with rheumatoid arthritis was maintained in organ culture for 3-14 days. Conditioned media from these synovial cultures contained bone resorption-stimulating activity, measured in vitro by using calcium release from mouse calvaria as the assay system. The synovial cultures also produce prostaglandin E2 (PGE2) as measured by serologic methods. The production of both the bone resorption-stimulating activity and PGE2 was inhibited by more than 90% by treatment of the synovial cultures with indomethacin (5 mug/ml). In contrast, treatment of the synovial cultures with colchicine (0.1 mug/ml) caused a marked and parallel increase in the concentration of both bone resorption-stimulating activity and PGE2 in the conditioned media. The bone resorption-stimulating activity was quantitatively extracted into diethyl ether. Within the limits of experimental error, all of the bone resorption-stimulating activity in medium was accounted for by its content of PGE2, itself a potent osteolytic factor. We conclude that the bone resorption-stimulating activity produced by rheumatoid synovia in culture is PGE2.

Arthritis, Rheumatoid↗
PubMed1973

Early warning of rejection?

The urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG), beta-galactosidase (GAL), beta-glucosidase (GLU), and alkaline phosphatase (AP) was studied in 83 patients with renal allografts. Thirty of these patients had stable graft function and their urinary enzyme levels provided a range of normal values. Urinary lactic dehydrogenase (LDH) was estimated in 29 normal subjects and in 11 patients with renal allografts. Serum values for the five enzymes were also obtained. Urinary NAG excretion was abnormally high in 16 out of 17 (94%) episodes of acute rejection. The other urinary enzymes were raised less frequently. In nine patients studied before the onset of rejection urinary NAG activity rose up to three weeks before changes in other tests of renal function. Serum enzyme levels were not found to be of value in the diagnosis of rejection.

Acute Disease↗