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Biomedical subjects

D R Robinson

Publications and source records attributed to D R Robinson.

At least 91 records · Page 5Linked to original sources
PubMed1984

Dietary menhaden oil lowers plasma prostaglandins and calcium in mice bearing the prostaglandin-producing HSDM1 fibrosarcoma.

The omega 3 class of polyunsaturated fatty acids, particularly eicosapentaenoic acid (EPA, 20:5), has been shown to alter the patterns of arachidonic acid (20:4) metabolism in both in vitro and in vivo systems. To examine further the role of arachidonic acid conversion to prostaglandins (PG) in hypercalcemic mice bearing the PG-producing HSDM1 fibrosarcoma, we have performed experiments in which control and tumor-bearing animals were fed diets either low (0.1-0.2% of total fatty acid) or high (17%) in EPA. In all five experiments performed, tumor-bearing mice eating control diets had markedly elevated (average sixfold above control) plasma concentrations of 13,14-dihydro-15-keto-PGE2 (PGE2-M), while in mice bearing HSDM1 tumors and eating the EPA-enriched menhaden oil diet, the elevation was reduced to only twice control values. The increase in plasma calcium concentration (approximately 2.5 mg/dl above control) in tumor-bearing animals was also reduced significantly (P less than 0.05) to only 1.3 mg/dl above control in mice eating the diet enriched in EPA. Plasma immunoreactive hydroxy fatty acids (i12-HETE) and sulfidopeptide leukotrienes (iSRS) were not elevated in tumor-bearing mice and were unaffected by diet. The contents of PGE2, PGF2 alpha, and 6-keto-PGF1 alpha were lower in tumor tissue from animals eating the diet high in EPA, whereas the tissue contents of i12-HETE and iSRS were not altered by diet. Fatty acid analysis of liver and tumor tissue revealed marked increases in certain omega 3 fatty acids (20:5, 22:5, and 22:6) from animals eating the enriched diet. Body weights, tumor weights, and tumor histology were not significantly altered by diet. To determine whether dietary calcium played a role in the elevation of plasma calcium in mice bearing the HSDM1 tumor and the reduction of plasma calcium in animals fed EPA, we compared results in mice fed diets containing 0.80% (normal) and 0.015% (deficient) calcium. The increases in plasma calcium and PGE2-M observed in tumor-bearing mice were the same on both normal and very low calcium intakes. We conclude, in mice of the Swiss albino strain bearing the HSDM1 fibrosarcoma, that consumption of a diet enriched in EPA reduces the production of cyclooxygenase products of arachidonic acid metabolism and thereby reduces the elevation of plasma calcium concentration. Dietary enrichment with EPA did not alter the production of serologically determined lipoxygenase products of arachidonic acid.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1984

Immunologically induced generation of tetraene and pentaene leukotrienes in the peritoneal cavities of menhaden-fed rats.

The generation of sulfidopeptide leukotrienes and leukotriene B (LTB) in response to an IgG-mediated immune complex reaction in the peritoneal cavities of rats fed either a menhaden oil-supplemented diet or a beef tallow-supplemented diet for 9 to 10 wk was determined with the combined techniques of radioimmunoassay (RIA) and reverse-phase high performance liquid chromatography. Rats on the fish fat diet (FFD) incorporated eicosapentaenoic acid (EPA) into pulmonary and splenic tissues with an EPA:arachidonic acid ratio of approximately 2:1, whereas rats on the beef fat diet (BFD) showed no detectable EPA. The estimated total quantities of immunoreactive sulfidopeptide leukotrienes generated by each group of rats were similar, ranging from 70 to 99 ng/ rat in the FFD groups and 65 to 109 ng/rat in the BFD groups; for rats on the FFD this total included the pentaene products LTC5, LTD5, and LTE5 in quantities ranging from 24 to 39 ng/rat. The total quantities of immunoreactive LTB generated in the two groups of rats were similar, being 6 to 29 ng LTB4/rat for the BFD groups and the sum of LTB4 and LTB5 of 8 to 36 ng/rat for the FFD groups. There was a two- to seven-fold preferential generation of immunoreactive LTB5 over LTB4 in the FFD rats. LTC5 was equipotent with LTC4 in contracting guinea pig pulmonary parenchymal strips and ileal tissues. In contrast, LTB5 was 1/30 to 1/60 as potent and did not reach the same maximum as LTB4 in eliciting neutrophil chemotaxis. The finding that FFD favors the immunologic generation of LTB5, which has attenuated biologic activity when compared to LTB4, suggests that EPA-enriched tissues may produce less pro-inflammatory activity than tissues that are EPA-poor.

Animals↗
PubMed1984

Dietary fish oil augments the induction of arthritis in rats immunized with type II collagen.

Certain dietary-induced changes in tissue levels of polyunsaturated fatty acids are known to modify inflammatory reactions, possibly through changes in the synthesis of mediators of inflammation derived from fatty acids, including prostaglandins and leukotrienes. We have therefore examined the effects of a fish oil diet, enriched in highly unsaturated (delta-17) long chain fatty acids, on collagen arthritis. Weanling female Sprague-Dawley rats were maintained on a diet with fat provided by either fish oil (containing 14.5% 5, 8, 11, 14, 17-eicosapentaenoic acid; EPA) or, as a control, beef tallow (containing less than 0.05% EPA). They were immunized with native chick type II collagen emulsified in incomplete Freund's adjuvant 5 to 6 wk later. There was an increased incidence of arthritis in the rats receiving the fish oil compared with the group receiving the beef diet (88 vs 61%, p less than 0.001), but there was no significant difference in the severity of joint inflammation of arthritic rats in the two groups. The mean serum titer of IgG antibodies to type II collagen, measured by an enzyme-linked immunosorbent assay (ELISA), was decreased in the group receiving the fish oil (p less than 0.001), whereas the hemagglutinating antibody titer and delayed-type hypersensitivity to collagen were similar in the two groups. Primary synovial explant cultures from fish oil-treated rats produced only 21 to 24% as much PGE2 as beef tallow-treated controls, and this reduction in the experimental group was not accompanied by any detectable increase in PGE3, the E-prostaglandin derived from the arachidonic acid analogue, EPA, in fish oil. These data demonstrate that inductive mechanisms in collagen arthritis can be altered by diet-induced changes in tissue fatty acid composition without essential fatty acid deficiency. The reason(s) for this effect is unknown, but it is possible that changes in the cyclooxygenase or lipoxygenase products of polyunsaturated fatty acids are involved.

Alprostadil↗
PubMed1984

Expiratory flow limitation in large and small airways.

Obstructive airways diseases constitute 75% of all chronic respiratory diseases. This article briefly reviews the physlologic basis for flow limitation in large and small airways. Application of the physiologic principles described can lead to a better understanding of the normal mechanics of breathing and the various alterations resulting from diseases that limit airflow.

Airway Resistance↗
PubMed1983

Prostaglandins and the mechanism of action of anti-inflammatory drugs.

Aspirin and a large number of nonsteroidal anti-inflammatory drugs act primarily through the inhibition of prostaglandin synthesis by inhibiting the enzyme cyclooxygenase. Other groups of biologically active polyunsaturated fatty acid derivatives including the leukotrienes, are generally not inhibited by this class of drugs in the same concentration ranges. Inhibition of the vasodilator prostaglandins, prostaglandin E2 and prostacyclin, as well as the leukotrienes, may reduce their inflammatory effects in several disease states. In addition, prostaglandin synthesis is also inhibited by glucocorticoids even though their mode of action may involve other effects as well. Prostaglandin E2 stimulates the osteoclastic reabsorption of juxtaarticular bone; its inhibition by nonsteroidal anti-inflammatory agents may, therefore, retard the process of bone erosion in rheumatoid arthritis and in other inflammatory processes. Inhibition of prostaglandin synthesis by these drugs accounts for many of their major toxic effects, including gastritis, which is the most common side effect; precipitation or aggravation of renal failure; fluid retention; hyperkalemia; antiplatelet effects with hemorrhagic phenomena; and aggravation of asthma and rhinosinusitis. Inhibition of prostaglandin synthesis can, therefore, account for most of the therapeutic as well as toxic effects of the nonsteroidal anti-inflammatory agents. Inhibition of pathways of synthesis of other important mediators, such as leukotrienes, are currently under investigation and may provide another approach for the development of new therapeutic agents.

Anti-Inflammatory Agents↗
PubMed1983

Effects of dietary enrichment with eicosapentaenoic acid upon autoimmune nephritis in female NZB X NZW/F1 mice.

A menhaden oil diet, rich in eicosapentaenoic acid, protected female NZB X NZW/F1 mice from autoimmune nephritis. Only 15% of mice treated with the diet from weaning had died with severe renal disease at 19 months, versus 98% of controls on a beef tallow diet. The menhaden oil also protected these mice from renal disease when instituted at 4 and 5 months of age and, under these conditions, levels of anti-native DNA antibodies were similar in both dietary groups. Our data suggest that the menhaden oil diet may act primarily to reduce inflammation via the ability of eicosapentaenoic acid to alter the production of prostaglandins and leukotrienes.

Animals↗
PubMed1982

A diet enriched with eicosapentaenoic acid suppresses autoimmune nephritis in female (NZB x NZW) F1 mice.

A diet containing menhaden oil, rich in EPA, protected (NZB x NZW) F1 mice from developing lupus nephritis. Only 16% of mice treated with this diet from 5-6 weeks of age developed severe renal disease by 19 months of age, as opposed to 100% of controls. The menhaden oil diet, when delayed until mice were 5 months of age, also reduced the incidence of renal disease, and under these conditions anti-n-DNA and anti-ss-DNA antibodies were similar in treated and control groups. We suggest that EPA, an AA analogue, may reduce inflammation by altering the production of PGs and LTs.

Age Factors↗
PubMed1981

Mechanism of stimulation of prostaglandin synthesis by a factor from rheumatoid synovial tissue.

Rheumatoid synovial cell monolayers, with [1-14C]arachidonic acid ([1-14C]AA) incorporated into cell lipids, are stimulated by a factor (RSF) produced by explant cultures of rheumatoid synovial tissue to produce up to 50-fold increases in [1-14C]prostaglandin E2 and [1-14C]prostaglandin I2. In contrast, levels of free [1-14C]AA released from RSF-stimulated cells are generally lower than [1-14C]AA levels in cultures of untreated cells. These observations are inconsistent with a mechanism of prostaglandin stimulation consisting of an increase in phospholipase activity, because this mechanism would increase free AA levels as well as prostaglandins. A mechanism is proposed in which free AA is maintained at low steady-state levels by reacylation of free AA into phospholipids at a rate more rapid than its reaction with cyclooxygenase to form prostaglandins. In this mechanism, stimulation of the rate of the cyclooxygenase step by RSF accounts for increased prostaglandin synthesis as well as the decreased release of AA. On the basis of data previously reported by others, it is suggested that this mechanism may also be applicable to the stimulation of prostaglandin synthesis by several other agents. Preliminary characterization of the RSF indicates that it is a protein, and molecular seive chromatography indicates that its molecular weight is about 18,000. The production of RSF by rheumatoid synovial tissue is suppressed to undetectable levels by 1 microM dexamethasone.

Arachidonic Acid↗
PubMed1981

Dietary enrichment with the polyunsaturated fatty acid eicosapentaenoic acid prevents proteinuria and prolongs survival in NZB x NZW F1 mice.

Prostaglandins and related compounds are active mediators of inflammation, but data concerning their role in the pathogenesis of the glomerulonephritis of New Zealand Black x New Zealand White (NZB x NZW) F1 mice are conflicting. Dietary eicosapentaenoic acid (EPA, C20:5), a fatty acid analogue of arachidonic acid (C20:4), has been shown to impair platelet aggregation in humans, apparently through inhibition of the synthesis of prostaglandins and thromboxanes from arachidonic acid. We report here the effects of a diet high in EPA on the development of renal disease and survival in female NZB x NZW F1 mice. Animals from 4--5 wk of age were fed diets containing 25% lipid, supplied either as beef tallow or menhaden oil, with fatty acid analysis of less than 0.05 and 14.4% EPA, respectively. In the first experiment, by 13.5 mo of age, mice on the beef tallow diet had all (9/9) developed proteinuria and the majority (6/9) had died, with renal histologic examination revealing severe glomerulonephritis. In contrast, none of 10 menhaden oil-fed animals had developed proteinuria, and all were alive at this time (P less than 0.005 for both proteinuria and survival). In a second experiment using 50 mice in each dietary group, 56% of the beef tallow group vs. none of the menhaden oil group had developed proteinuria at 9 mo of age (P less than 0.005). Native DNA binding at 6 mo of age was 23.9 +/- 14.7 vs. 10.1 +/- 9.7% in the beef and menhaden oil groups, respectively (P less than 0.01). Weights were similar in all groups, and there was no evidence of essential fatty acid deficiency in any group. These results demonstrate that a diet high in EPA protects NZB x NZW F1 mice from the development of glomerulonephritis.

Animals↗
PubMed1981

Control of fever associated with visceral cancers by indomethacin.

Fever commonly complicates intra-abdominal cancer when there are peritoneal or liver metastases but no infection. Although aspirin and acetaminophen have little or no effect on this fever and its debilitating effects, we have found that indomethacin dramatically and completely eliminates the fever. This observation and the measured decrease in urinary excretion of prostaglandin E2 suggest that fever associated with visceral tumors may be mediated by prostaglandins.

Abdominal Neoplasms↗
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↗
PubMed1979

Collagenase and prostaglandin in connective tissue destruction: cell-cell and humoral interactions.

Connective tissue destruction is a major characteristic of chornic rheumatoid arthritis (RA). This process is accompanied by local cellular and humoral inflammatory reactions. Long-term cultures of adherent synovial cells (ASC) from patients with RA produce large amounts of collagenase and prostaglandin (PGE2), two substances that play a role in the degradation of joint structures. Lvels of collagenase and PGE2 can be stimulated (up to several hundred-fold) with a soluble factor (MCF) from cultured peripheral blood mononuclear cells (MW approximately 14,000). The monocyte-macrophages alone produce MCF but can be stimulated directly with Fc fragments of immunoglobulin or concanavalin A to increase MCF production. Addition of T lymphocytes in the presence of lectin or antigen significantly enhances the production of MCF. MCF affects other biological processes in synovial cells such as the rate of collagen synthesis, cell proliferation and sensitivity to PGE2 as well as collagen itself can further modulate collagenase release by the synovial cells and function in an amplificative loop. The understanding of these interactions between cells, mediator-effector substances and connective tissue substrates may provide a basis for devising more rational approaches to therapy of the destructive lesions which characterize RA.

Arthritis, Rheumatoid↗
PubMed1978

Unusual renal manifestations of Wegener's granulomatosis. Report of two cases.

Two patients with previously undescribed renal manifestations of Wegener's granulomatosis are described. A 24 year old man, who presented with typical necrotizing granulomatous sinus disease and cavitary pulmonary lesions, had multiple bilateral renal arterial aneurysms demonstrated angiographically. One of these aneurysms ruptured, leading to a massive perinephric hematoma. The bleeding artery was successfully occluded with Gelfoam embolization, thereby obviating the need for nephrectomy. A 60 year old woman presented with glomerulonephritis and mononeuritis multiplex two years before the development of classic necrotizing granulomatous inflammation of her sinuses and nose, along with pulmonary nodules. In addition, her left ureter became obstructed due to necrotizing vasculitis of the periureteral vessels. Both patients responded dramatically to cyclophosphamide therapy. The diagnosis of Wegener's granulomatosis should be considered in patients who present with multiple renal aneurysms, a spontaneous perinephric hematoma, necrotizing glomerulitis or ureteral obstruction due to vasculitis, even though the characteristic granulomatous respiratory involvement may be absent at that time. It is important to recognize these unusual renal manifestations as features of Wegener's granulomatosis because of the therapeutic efficacy of cytotoxic immunosuppressive agents in this disease.

Adult↗