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J M Dayer

Publications and source records attributed to J M Dayer.

At least 217 records · Page 12Linked to original sources
PubMed1981

[Destruction and inflammation of the joints in rheumatoid arthritis: a pathogenic hypothesis (author's transl)].

On the basis of recent in vitro studies, the authors hypothetize on the mechanism of joint destruction in rheumatoid arthritis. They suggest that the leading part is played by the cells of the synovial membrane, which have been found in cultures to secrete biochemical substances, such as collagenase or PGE2, involved in the destruction of articular surfaces. The secretion of these substances is considerably increased by soluble factors produced by monocytes under the influence of lymphocytes, and lymphocytes are known to participate in the chronic inflammatory reaction characteristic of the disease. Such a pathogenic sequence might lead to new therapeutic approaches.

Arthritis, Rheumatoid↗
PubMed1981

Factors modulating the response of a porcine renal tubular cell line to calcitonin and antidiuretic hormone.

A cell line (LLC-PK1) isolated from porcine kidney increases 3'5'-cyclic adenosine monophosphate (cAMP) content when incubated with salmon calcitonin (SCT) or antidiuretic hormone (ADH). We have examined several factors which modulate the hormone-induced changes in cAMP levels in these cells. Preincubation with increasing concentrations of SCT results in a dose-dependent decrease in cAMP levels in cells retested with this hormone. Addition of 3-isobutyl-l-methylxanthine (IBMX) to cells preincubated with SCT results in 15--30-fold increases in cAMP levels compared to cells preincubated without this hormone. These observations suggest that the decrease in SCT-induced cAMP response in cells pretreated with this hormone is related at least in part to stimulation of phosphodiesterase activity. Preincubation with ADH does not affect subsequent cAMP response to either ADH or SCT, suggesting that these hormones interact with different cell surface receptors. Cell cycle and plating density also affect cAMP levels. cAMP content per cell increases with increasing cell density, which is associated with an increase in the SCT-induced cAMP response. These studies illustrate that factors other than receptor occupancy modulate cAMP responses of these cells to specific hormones.

1-Methyl-3-isobutylxanthine↗
PubMed1981

Stimulation of rheumatoid synovial cell collagenase and prostaglandin production by partially purified lymphocyte-activating factor (interleukin 1).

Human macrophages produce in culture a factor termed mononuclear cell factor (MCF) that increases the production of collagenase and prostaglandins by isolated adherent rheumatoid synovial cells. A factor with similar biologic activity is also produced by the murine macrophage cell line P388D1. By using a sequential purification scheme involving ammonium sulfate fractionation; chromatography on DEAE-cellulose, Sephacryl S-200, and phenyl-Sepharose; and discontinuous polyacrylamide gel electrophoresis, the P388D1 cell-derived, synovial cell-stimulating factor was copurified with the lymphocyte-activating factor [LAF; interleukin 1 (IL 1)]. The specific activity of the partially purified LAF (IL 1) was approximately 15,000-fold higher than that of the LAF (IL 1) in the original P388D1 cell culture supernatant. On the basis of (i) the copurification of the P388D1 cell-derived LAF (IL 1) and synovial cell-stimulating factors; (ii) the similarity in cell of origin, molecular weight, and phenylglyoxal sensitivity of human MCF and murine LAF (IL 1); and (iii) the presence of LAF (IL 1) activity in preparations of partially purified human MCF, we have postulated that LAF (IL 1) may have effects on cell targets that are nonlymphoid in nature and also that human MCF may be similar to, or identical with human LAF (IL 1). The results of these studies have raised the possibility that LAF (IL 1) may play a role in macrophage-mediated activation of synovial cells and lymphocytes which are involved in the inflammatory responses associated with rheumatoid arthritis.

Arthritis, Rheumatoid↗
PubMed1981

Interaction of ouabain with the Na+ pump in intact epithelial cells.

To determine the specificity and efficacy of [(3)H]ouabain binding as a quantitative measure of the Na(+) pump (Na(+), K(+)-ATPase) and as a marker for the localization of pumps involved in transepithelial Na(+)-transport, we analyzed the interaction of [(3)H]ouabain with its receptor in pig kidney epithelial (LLC-PK(1)) cells. When these epithelial cells are depleted of Na(+) and exposed to 2 muM [(3)H]ouabain in a Na(+)-free medium, binding is reduced by 90 percent. When depleted of K(+) and incubated in a K(+)- free medium, the ouabain binding rate is increase compared with that measured at 5 mM. This increase is only demonstable when Na(+) is present. The increased rate could be attributed to the predominance of the Na(+)-stimulated phosphorylated form of the pump, as K(+) is not readily available to stimulate dephosphorylation. However, some binding in the K(+)-free medium is attributable to pump turnover (and therefore, recycling of K(+)), because analysis of K(+)-washout kinetics demonstrated that addition of 2 muM ouabain to K(+)-depleted cells increased the rate of K(+) loss. These results indicate that in intact epithelial cells, unlike isolated membrane preparations, the most favorable condition for supporting ouabain binding occurs when the Na(+), K(+)-ATPase is operating in the Na(+)-pump mode or is phosphorylated in the presence of Na(+). When LLC-PK(1) cells were exposed to ouabain at 4 degrees C, binding was reduced by 97 percent. Upon rewarming, the rate of binding was greater than that obtained on cells kept at a constant 37 degrees C. However, even at this accelerated rate, the time to reach equilibrium was beyond what is required for cells, swollen by exposure to cold, to recover normal volume. Thus, results from studies that have attempted to use ouabain to eliminate the contribution of the conventional Na(+) pump to volume recovery must be reevaluated if the exposure to ouabain was done in the cold or under conditions in which the Na(+) pump is not operating.

Animals↗
PubMed1981

Calcitonin stimulates plasminogen activator in porcine renal tubular cells: LLC-PK1.

Plasminogen activators are highly selective proteases that activate the proenzyme plasminogen to the general protease, plasmin. We studied a porcine kidney cell line, originally isolated as a high producer of plasminogen activator, in which activities of cellular adenylate cyclase and cAMP-dependent protein kinase are increased in response to calcitonin. We found that salmon calcitonin, in the concentration range 0.03-300 nM, increased plasminogen activator production up to approximately 1,000-fold and concurrently inhibited cell multiplication; both of these effects were reversible. Human calcitonin was approximately 0.01 times as potent as salmon calcitonin, corresponding to potency differences observed in other biological systems. Plasminogen activator production was also stimulated by other agents that raise cellular cAMP levels such as cholera toxin, phosphodiesterase inhibitors, and vasopressin, but not to the same extent as by calcitonins. The rapidity and sensitivity of the plasminogen activator determination and other cellular responses may make it possible in the future to use this cell stain in a convenient bioassay for calcitonins and their analogues.

Animals↗
PubMed1981

Factors regulating the response of cells cultured from human giant cell tumors of bone to parathyroid hormone.

Exposure of cells cultured from human giant cell tumors of bone to parathyroid hormone (PTH) results in an increase in the intracellular cAMP content. When cells are preincubated with PTH for periods as short as 10 min and then reexposed to this hormone, there is a decrease in the subsequent PTH-induced cAMP response. This decrease is inversely related to the concentration of PTH present during the preincubation. To investigate the factors responsible for this decrease in hormone response, we used a synthetic substituted analog of bovine PTH, [Nle8, Nle18, Tyr34]bPTH-(3-34) amide (PTH-Inh), which had previously been shown to be a competitive inhibitor of PTH-induced cAMP response in renal and bone-derived tissues. Incubation of these cultured cells with this analog failed to increase intracellular cAMP levels. In contrast to the results obtained with native hormone, when cells were preincubated with PTH-Inh, the acute cAMP response to native PTH after the removal of PTH-Inh was not diminished. In addition, simultaneous preincubation with native PTH and PTH-Inh partially overcame desensitization to PTH. These results suggest that occupancy of the PTH receptor alone is not sufficient to cause desensitization. Rather, steps subsequent to hormone binding, including activation of adenylate cyclase, may be required for the induction of a state of desensitization to PTH.

1-Methyl-3-isobutylxanthine↗
PubMed1980

Modulation of cyclic AMP-dependent protein kinase by vasopressin and calcitonin in cultured porcine renal LLC-PK1 cells.

We have previously demonstrated that a cultured porcine kidney cell, LLC-PK(1), maintains the characteristics of a polar renal epithelial cell in culture, and responds to salmon calcitonin and [arginine]vasopressin by increasing cyclic AMP content. To demonstrate the usefulness of this cell line as a model for the study of the biochemical events distal to cyclic AMP production, the activation of cyclic AMP-dependent protein kinase was examined. Intact cells in monolayer demonstrated progressive increases in cyclic AMP content and activation of protein kinase in response to [arginine]vasopressin (2-200nm) and salmon calcitonin (0.03-30nm) with both hormones fully activating the enzyme at a cell cyclic AMP content of 35pmol/mg of protein. Of the total cyclic AMP-dependent protein kinase activity, 80% was found in the 27000g supernatant fraction of sonicated cell material, and this soluble protein kinase could be fully activated by hormone. Conversely, the 27000g pellet contained a significant proportion of cyclic AMP-independent protein kinase and only 20% of total cell cyclic AMP-dependent protein kinase; the latter showed little response to hormone. On the basis of DEAE-cellulose chromatography, type II protein kinase was the predominant isoenzyme in both soluble and particulate fractions of the LLC-PK(1) cells and the soluble fractions of rat and guinea-pig renal medulla. Thus, the LLC-PK(1) cell line can serve as a model for hormonal modulation of protein kinase and as a potential source for defining the endogenous substrates for these enzymes.

Animals↗
PubMed1980

Parathyroid hormone modulates protein kinase in giant cell tumors of human bone.

The physiological effects of parathyroid hormone (PTH) in bone are mediated at least in part by cyclic AMP. The biochemical events subsequent to this step have not been well characterized in this tissue. Giant cell tumors of bone (GT) increase cyclic AMP in response to PTH. This response can be inhibited by an analogue of bovine PTH, [Nle8, Nle18, Tyr34] bPTH-(3-34) amide (PTH-Inh). Cyclic AMP content and cyclic AMP-dependent protein kinase (cAMP-PK) were assayed in fresh tumors and cells in culture incubated with 1 microgram/ml of bPTH and/or PTH-Inh. PTH fully activated cAMP-PK in GT, and PTH-Inh completely inhibited PTH-stimulated increases in cyclic AMP content and cAMP-PK activity. When endogenous protein substrates were sought for cAMP-PK, three phosphoproteins of 55,000, 43,000, and 38,000 mol wt maximally increased their phosphorylation by 30% after 12-min incubation with bPTH. Dephosphorylation of proteins of 200,000 and 120,000 mol wt was also observed. These data are consistent with the hypothesis that PTH action in bone is mediated by the phosphorylation and dephosphorylation of specific substrates.

Bone Neoplasms↗
PubMed1980

Interactions among rheumatoid synovial cells and monocyte-macrophages: production of collagenase-stimulating factor by human monocytes exposed to concanavalin A or immunoglobulin Fc fragments.

Adherent synovial cells (ASC) were obtained from minced synovium from patients with rheumatoid arthritis by dissociating the lining cells from the extracellular matrix and dispersing them with proteases. These cells produce high levels of latent collagenase in primary culture. With passage of ASC, collagenase levels decrease but can be stimulated by a soluble factor (MCF) released in vitro from cultured human blood monocyte-macrophages. Monocyte cultures exposed to aggregated immunoglobulin, Fc fragments of immunoglobulin or concanavalin A (Con A) increase production of MCF several-fold more than the control cultures. MCF production by monocytes exposed to Fab fragments does not differ from controls. Although aggregated immunoglobulin, Fc fragments, and Con A stimulate PGE2 synthesis and secretion by human monocytes, the effects on MCF production are not mediated by PGE2 since concentrations of indomethacin that completely block PGE2 production do not inhibit MCF production. These findings of increased production of MCF by monocytes in response to substances that probably exert their effects via surface receptors could be relevant in interpreting the in vivo role of immune complexes in diseases associated with connective tissue destruction.

Arthritis, Rheumatoid↗
PubMed1980

Regulation by Fc fragments of the secretion of collagenase, PGE2, and lysozyme by mouse peritoneal macrophages.

Fc fragments of human IgG can stimulate resident mouse macrophages in culture to secret collagenase, to increase PGE2 secretion, and to decrease the secretion of lysozyme. Active synthesis and secretion were shown by the progressive accumulation of these products in the extracellular medium and inhibition of secretion by cycloheximide. A dose-dependent effect of Fc fragments was demonstrable. Brief exposure of cells to Fc fragments was sufficient to cause the macrophages to secrete collagenase and large amounts of PGE2 for prolonged periods of time, suggesting that a sustained activation rather than temporary modulation of the cells had occurred. Con A had similar effects on macrophage secretory activity. These findings indicate that proteins that bind to specific macrophage plasma membrane receptors may stimulate the secretion of products that promote the inflammatory response.

Animals↗
PubMed1979

Regulation of hormone-induced cyclic AMP response to parathyroid hormone and prostaglandin E2 in cells cultured from human giant cell tumors of bone.

Cells dispersed from human giant cell tumors of bone and grown in monolayer culture increase intracellular cyclic AMP (cAMP) when incubated with parathyroid hormone (PTH) or prostaglandin E2 (PGE2). When cells are continuously exposed to PTH, cAMP levels increase acutely but then decrease rapidly to pretreatment values despite continued presence of hormone or addition of new hormone. Preincubation of cells with PTH for periods as short as 10 min results in a decrease in the capacity of cells to increase cAMP content when re-exposed to maximal stimulatory concentrations of PTH. The decrease in the magnitude of the PTH-induced cAMP response observed in cells pretreated with this hormone is dependent on the concentration of PTH present during the preincubation. The loss of cAMP response in cells pretreated with either PGE2 or PTH is hormone specific in that cells made refractory by pretreatment with one hormone still increase cAMP content when exposed to the other. Although the cells are not releasing measurable amounts of prostaglandins into the medium, pretreatment with indomethacin results in an increase in the magnitude of the cAMP response to PGE2. The PTH-induced cAMP response is not affected by indomethacin pretreatment. The loss of PTH responsiveness produced by hormone preincubation is consistent with the phenomenon of "down-regulation" observed with ligand-receptor interactions in a variety of tissues.

1-Methyl-3-isobutylxanthine↗
PubMed1979

Stimulation of collagenase production by collagen in mammalian cell cultures.

In this study, we investigated the possible regulatory role of collagen in collagenase production by cultured human skin fibroblasts and human and rabbit synovial cells. Addition of types I, II or III collagen in solution to the culture media markedly stimulated trypsin-activable collagenase activity in these cultures. In the human cell cultures the stimulatory effect of collagen was further enhanced by a soluble factor isolated from human monocyte culture media (Dayer, Russell and Krane, 1977). Both native and denatured forms of collagen stimulated enzyme production; their relative efficacy varied among the different types. The native form of both types I and II collagen showed a greater effect on collagenase production than the corresponding denatured form, whereas with type III collagen the denatured form was more effective.

Animals↗
PubMed1979

Prostaglandins and their regulation in rheumatoid inflammation.

Prostaglandins, especially PGE2 and PGI2, appear to participate in the development of inflammatory reactions. While these PGs may act to promote inflammation, they may also inhibit immune reactions; this effect is largely related to stimulation of adenylate cyclase. Human rheumatoid synovial tissue explants and derived adherent synovial cells (ASC) in vitro produce large amounts of PG, primarily PGE2, which may participate in the pathogenesis of rheumatoid inflammation and promote the osteoclastic resorption of juxtaarticular bone. Rheumatoid synovial organ cultures are unusual in that they derive a significant proportion of archidonic acid substrate for the PGE2 synthesis from triglycerides, while ASC utilize primarily phospholipids. Aspirin-like, nonsteroidal anti-inflammatory drugs inhibit PGE2 synthesis by rheumatoid synovial organ cultures at concentrations similar to those achieved in plasma during therapy. Glucocorticoids are also potent inhibitors of PGE2 synthesis, and evidence from experiments with tissue labeled with 1-[14C]arachidonic acid indicates that glucocorticoids do not act to inhibit arachidonic acid release, as has been postulated for other tissues. Human peripheral blood mononuclear cells produce a factor (MCF) that regularly stimulates the production of PGE2 and collagenase from resting ASC often by over 100-fold. The MCF appears to be produced by monocytes, and its production by monocytes is enhanced by lectin-stimulated T-cells. The ability of ASC to respond to exogenous PGE2 stimulation of cAMP synthesis is inhibited or stimulated by factors that increase or decrease PGE2 levels, respectively, in the cultures. The MCF augments the responsiveness of cAMP response to PGE2 in indomethacin-treated cultures. These in vitro experiments suggest that the pathogenesis of rheumatoid inflammation involves interactions between monocyte-macrophages, lymphocytes, and synovial cells regulating the production of PGE2, cAMP, and other factors.

Animals↗