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Biomedical subjects

J A Oates

Publications and source records attributed to J A Oates.

At least 37 records · Page 2Linked to original sources
PubMed1996

Identification of the major urinary metabolite of the F2-isoprostane 8-iso-prostaglandin F2alpha in humans.

F2-isoprostanes are prostaglandin-like products of nonenzymatic lipid peroxidation. Measurement of levels of endogenous unmetabolized F2-isoprostanes has proven to be a valuable approach to assess oxidative stress in vivo. However, measurement of levels of urinary metabolites of F2-isoprostanes in timed urine collections offers an advantage over measuring unmetabolized F2-isoprostanes, e. g. in a plasma sample, in that it can provide an integrated index of isoprostane production over time. Therefore, we sought to identify the major urinary metabolite in humans of one of the more abundant F2-isoprostanes produced, 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha). 20 microCi of tritiated 8-iso-PGF2alpha was infused over 1 h into a male volunteer. 75% of the infused radioactivity was excreted into the urine during the following 4.5 h and was combined with urine collected for 4 h from a rhesus monkey following infusion of 500 microg of unlabeled 8-iso-PGF2alpha. Urinary metabolites were isolated and purified by adsorption chromatography and high pressure liquid chromatography. The major urinary metabolite, representing 29% of the total extractable recovered radioactivity in the urine, was structurally identified by gas chromatography and mass spectrometry as 2,3-dinor-5, 6-dihydro-8-iso-prostaglandin F2alpha. The identification of 2, 3-dinor-5,6-dihydro-prostaglandin F2alpha as the major urinary metabolite of 8-iso-prostaglandin F2alpha provides the basis for the development of methods of assay for its quantification as a means to obtain an integrated assessment of oxidative stress status in humans.

Animals↗
PubMed1996

Incorporation of 12(S)-hydroxyeicosatetraenoic acid into the phosphatidylcholine signaling pathway.

The incorporation of 12-lipoxygenase metabolites into phospholipids (PLs) could modify second messengers such as diacylglycerols (DAG) and phosphatidic acids. Incubation of [(14)C]12(S)-HETE (1 microM) with bovine pulmonary artery endothelial cells (BPAEC), resulted in its incorporation in PLs with concentration-dependent kinetics. After a 4 h incubation, the proportion of radioactive phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS) + phosphatidylinositol (PI) isolated by TLC, was 77.9%, 16.4% and 5.7%, respectively. In PC, [(14)C]12(S)-HETE was incorporated at the position 2 of the glycerol. Three major peaks of radioactive PC were isolated on RP-HPLC which were hydrolysed by phospholipase C (PLC). The resulting diacylglycerols were derivatized and identified by GC/MS as 1-oleyl-, 1-stearoyl- and 1-palmitoyl-2-[12-HETE] PC. BPAEC were incubated with [(14)C]12(S)-HETE (1 microM) before stimulation with bradykinin (1 microM). (A) 1-acyl-2-[12-HETE] diacylglycerols were isolated, derivatized and analysed by MS. We identified a major ion with m/z = 926 that corresponds to the molecular ion of authentic 1-stearoyl-2-12(S)-HETE DAG, and 2 other ions with m/z = 924 and 898 that correspond to the molecular ions of 1-oleyl- and 1-palmitoyl-2-12(S)-HETE DAG, respectively. (B) Radioactive PA was isolated and hydrolysed by alkaline phosphatase. The MS of resulting diacylglycerols identified 1-stearoyl-, 1-oleyl-, and 1-palmitoyl-2-12(S)-HETE phosphatidic acids. The quantities of 12-HETE PA and the 3 major 12-HETE diacylglycerols were shown to increase following bradykinin stimulation. Thus, the incorporation of 12(S)-HETE into PLs results in the production of altered phosphatidic acids and diacylglycerols. The time-course of increases in 1-acyl-2-(12-HETE) phosphatidic acids and 1-acyl-2-(12-HETE) diacylglycerols showed maximal concentrations 1 and 2 min after bradykinin stimulation, respectively, followed by the decrease of both compounds. Propranolol, an inhibitor of PA phosphohydrolase, totally abolished the bradykinin-induced increase in 12-HETE DAG while increasing the magnitude and duration of 12-HETE PA release. The inhibiting effect of propranolol on bradykinin-induced increase of 12-HETE DAG demonstrates that 12-HETE PA is the principal precursor for 12-HETE DAG. This affords a novel method for confirming the major role of phospholipase D in PC metabolic pathways triggered during cell signaling.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1995

Increase in circulating products of lipid peroxidation (F2-isoprostanes) in smokers. Smoking as a cause of oxidative damage.

BACKGROUND: It has been hypothesized that the pathogenesis of diseases induced by cigarette smoking involves oxidative damage by free radicals. However, definitive evidence that smoking causes the oxidative modification of target molecules in vivo is lacking. We conducted a study to determine whether the production of F2-isoprostanes, which are novel products of lipid peroxidation, is enhanced in persons who smoke. METHODS: We measured the levels of free F2-isoprostanes in plasma, the levels of F2-isoprostanes esterified to plasma lipids, and the urinary excretion of metabolites of F2-isoprostanes in 10 smokers and 10 nonsmokers matched for age and sex. The short-term effects of smoking (three cigarettes smoked over 30 minutes) and the effects of two weeks of abstinence from smoking on levels of F2-isoprostanes in the circulation were also determined in the smokers. RESULTS: Plasma levels of free and esterified F2-isoprostanes were significantly higher in the smokers (242 +/- 147 and 574 +/- 217 pmol per liter, respectively) than in the nonsmokers (103 +/- 19 and 345 +/- 65 pmol per liter; P = 0.02 for free F2-isoprostanes and P = 0.03 for esterified F2-isoprostanes). Smoking had no short-term effects on the circulating levels of F2-isoprostanes. However, the levels of free and esterified F2-isoprostanes fell significantly after two weeks of abstinence from smoking (250 +/- 156 and 624 +/- 214 pmol per liter, respectively, before the cessation of smoking, as compared with 156 +/- 67 and 469 +/- 108 pmol per liter after two weeks' cessation; P = 0.03 for free F2-isoprostanes and P = 0.02 for esterified F2-isoprostanes). CONCLUSIONS: The increased levels of F2-isoprostanes in the circulation of persons who smoke support the hypothesis that smoking can cause the oxidative modification of important biologic molecules in vivo.

Adult↗
PubMed1995

Case report: lanreotide in the management of hypercalcemia of malignancy.

The management of hypercalcemia of malignancy (HCM) is difficult if the underlying neoplasm cannot be treated successfully. The overexpression of parathyroid hormone-related protein (PTHrP) by various neoplasms is a common mechanism of HCM and usually is a premorbid event. Current pharmacologic measures to control HCM are directed more toward inhibiting the action rather than inhibiting the secretion of PTHrP. The somatostatin congeners are a novel class of drugs that can inhibit some excessive hormonal states. In this report, the authors summarize an observation made using lanreotide, an investigational somatostatin congener, in treating a patient with a neuroendocrine neoplasm. Lanreotide administration resulted in normalizing the serum calcium levels while decreasing plasma PTHrP concentrations. The chronic administration of lanreotide produced a stable radiographic response and controlled the HCM without adverse side effects. The somatostatin congeners potentially offer another therapeutic modality in managing HCM.

Aged↗
PubMed1995

Improved diagnosis of mastocytosis by measurement of the major urinary metabolite of prostaglandin D2.

Symptoms of mastocytosis have been attributed to the overproduction of both histamine and prostaglandin (PG) D2. Recently, we developed an assay for the major urinary metabolite of PGD2 (PGD-M), 9 alpha,11 beta-dihydroxy-15-oxo-2,3,18,19-tetranorprost-5-ene-1,20-dioic acid, and demonstrated that urinary excretion of this compound is markedly increased in patients with mastocytosis. It had been shown previously that measurement of the urinary excretion of histamine metabolites provides a more sensitive biochemical diagnostic indicator of systemic mastocytosis than does measurement of unmetabolized histamine. Therefore, we examined the correlation between the urinary excretion of the histamine metabolite, NT-methylhistamine, and PGD-M in urine samples from patients with mastocytosis. Urinary excretion of NT-methylhistamine and PGD-M was measured in 46 urine samples from 17 patients with histologically documented mastocytosis. Both compounds were quantified by mass spectrometry. In all urine collections showing an increase above normal (2 SD above the mean) in the excretion of NT-methylhistamine, the fold increase above normal in the urinary excretion of PGD-M was substantially greater. Further, in some urine samples from four patients whose excretion of NT-methylhistamine was consistently normal, the excretion of PGD-M was increased above normal by as much as 300%. These data indicate that quantification of the urinary excretion of PGD-M is a more sensitive biochemical diagnostic indicator of mastocytosis than is the quantification of NT-methylhistamine.

Adult↗
PubMed1994

Eicosanoids in bronchoalveolar lavage fluid of aspirin-intolerant patients with asthma after aspirin challenge.

We have recently shown that oral aspirin provocation leads to an increase in LTE4 and a reduction in 11-dehydro-TXB2 levels in urine of patients with aspirin induced-asthma (AIA). To test the hypothesis that cyclooxygenase inhibition and an enhancement of cysteinyl-leukotriene production occurs in the lungs of patients with AIA, we examined the eicosanoid levels in bronchoalveolar lavage fluid obtained 30 min after lysine-aspirin or placebo inhalation in 10 patients with AIA. Eosinophil cationic protein (ECP) levels were determined to evaluate eosinophil activation. Six asthmatics nonsensitive to aspirin (NA) underwent challenge with placebo. The dose of lysine-aspirin inhaled by patients with AIA was equal to that which had produced > or = 20% fall in FEV1. Compared with NA, patients with AIA had: (1) eicosanoid levels, particularly PGE2 and TXB2, elevated and (2) higher number of eosinophils and ECP. The overproduction of eicosanoids could be related to a distinct eosinophilic inflammation in airways of patients with AIA. Inhalation of lysine-aspirin had no effects on 12-HETE and 15-HETE levels, but it markedly depressed cyclooxygenase products and significantly enhanced leukotriene production in the lungs of patients with AIA.

Adult↗
PubMed1994

Effect of oral prednisone on airway inflammatory mediators in atopic asthma.

The mechanism of steroid action in asthma is unknown. Because steroids have effects in vitro on eicosanoid synthesis, we determined the effect of oral prednisone for 6 to 9 days on eicosanoid levels in bronchoalveolar lavage (BAL) fluid of 14 atopic asthmatic volunteers at baseline and after allergen instillation. We also determined the effect of prednisone on the ex vivo release of eicosanoids from macrophage-rich BAL-fluid cells. Prednisone reduced symptoms and inhaler use but had no significant effect on BAL-fluid eicosanoid levels. At baseline, prostaglandin D2 (PGD2) levels were 101 +/- 37 pg/ml in BAL fluid (mean +/- SEM), versus 66 +/- 18 pg/ml after prednisone; likewise, 5-hydroxy eicosatetraenoic acid (5-HETE) levels were 59 +/- 15 versus 78 +/- 21; leukotriene E4 (LTE4) levels were 35 +/- 13 versus 51 +/- 21, and 15-hydroxy eicosatetraenoic acid (15-HETE) levels were 29 +/- 8 versus 19 +/- 7. Allergen-stimulated levels of PGD2 were 1274 +/- 565 versus 1468 +/- 679 after prednisone; likewise, allergen-stimulated 5-HETE levels were 95 +/- 21 versus 82 +/- 21; those of LTE4 were 54 +/- 20 versus 91 +/- 51; and those of 15-HETE were 63 +/- 19 versus 60 +/- 25. Prednisone reduced the synthesis of eicosanoids in macrophage-rich BAL-fluid cells in vitro. LTB4 levels fell significantly from 35 +/- 6.4 ng/10(6) BAL-fluid cells to 17 +/- 5.4 after prednisone; likewise, levels of thromboxane B2 (TXB2) fell from 35.7 +/- 7.5 to 20.7 +/- 6.6. Part of the action of steroids may involve alteration in macrophage eicosanoid synthesis.

Administration, Oral↗
PubMed1992

Identification of skin as a major site of prostaglandin D2 release following oral administration of niacin in humans.

Oral administration of niacin (nicotinic acid) at pharmacologic doses that reduce serum cholesterol levels induces intense flushing in humans. We have recently shown that the vasodilation following ingestion of niacin is due to the release of prostaglandin (PG) D2. However, the site from which PGD2 is released is not known. It has previously been shown that topical application of methylnicotinate causes local cutaneous erythema. Thus, we investigated whether topical methylnicotinate causes a release of PGD2 locally from skin and the possibility that skin may be a major contributor to the release of PGD2 when niacin is administered by mouth. Topical administration of methylnicotinate (10(-1) M) to the forearms of human volunteers resulted in 58- to 122-times increases in levels of PGD2 and 25- to 33-times increases in levels of the metabolite of PGD2, 9 alpha,11 beta-PGF2, in blood drawn from the antecubital vein draining the treated sites. Increased levels of PGD2 and 9 alpha,11 beta-PGF2 were not found in blood drawn simultaneously from veins in the contralateral arm, indicating that the PGD2 was released from the site of methylnicotinate application. The release of PGD2 in response to topically applied methylnicotinate occurred in a dose-dependent manner over the concentration range of 10(-3) to 10(-1) M. The release of PGD2 was not accompanied by a release of histamine, suggesting that the release of PGD2 was not from the mast cell. Following oral ingestion of niacin, levels of PGD2 in superficial venous blood draining the skin were 14 to 1200 times higher than the level in arterial blood supplying the skin of the same arm. This finding indicates that the skin is a major site from which PGD2 is released following oral ingestion of niacin. These studies thus indicate that the cutaneous vasodilation that occurs following oral administration of niacin is primarily due to a release of PGD2 from a niacin responsive cell that resides in the skin.

Administration, Oral↗
PubMed1991

Administration of carbamazepine in the nucleus of the solitary tract inhibits the antihypertensive effect of clonidine.

The effects of carbamazepine administration into the nucleus tractus solitarii (NTS) on central alpha 2-adrenergic cardiovascular function were studied in normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR). Stereotaxic microinjections of carbamazepine (288 ng/60 nl) into the NTS of SHR transiently increased blood pressure, heart rate, and renal sympathetic nerve activity. These effects were followed by a modest depressor and bradycardic effect, with no change in sympathetic nerve activity. In addition, previous intra-NTS administration of carbamazepine attenuated the antihypertensive effect of the centrally acting alpha 2-adrenoceptor agonist, clonidine. Similar carbamazepine effects were observed in the WKY rats. These results suggest that some of the cardiovascular changes observed during carbamazepine treatment involve antagonism of central noradrenergic mechanisms.

Animals↗
PubMed1991

Substitution of 15-hydroxyeicosatetraenoic acid in the phosphoinositide signaling pathway.

Consideration of how 15-hydroxyeicosatetraenoic acid (15-HETE) might exert its biological actions led us to investigate the consequences of its incorporation into bovine pulmonary arterial endothelial cell (BPAEC) phospholipids [3H]15(S)-HETE was incorporated mainly (89%) into phosphatidylinositols, predominantly as 1-stearoyl-2-(15-HETE) phosphatidylinositol. By contrast 5(S)- and 12(S)-HETE are incorporated largely into phosphatidylcholine. 15-HETE had a long persistence in the phosphatidylinositols of BPAEC with a half-life of 12 h; its uptake was concentration-dependent, and it accumulated so that 2-(15-HETE) phosphatidylinositol accounted for 10.9% of total phosphatidylinositol after four sequential 1-h incubations of cells with 1 microM 15(S)-HETE. After incubating BPAEC with 15(S)-HETE, stimulation of the cells with bradykinin led to an increase in the levels of 15-HETE. Following addition of bradykinin to cells exposed to [3H]15(S)-HETE, a radiolabeled diacylglycerol was isolated. A mass spectrum of its pentafluorobenzoyl (PFBO) trimethylsilyl (Me3Si) derivative obtained with direct electron capture negative ion chemical ionization mass spectrometry (DNICI/MS) revealed a molecular anion and fragment ions that were identical with those observed with the PFBO/Me3Si derivative of authentic 1-stearoyl-2-(15-HETE) diacylglycerol. There was a lesser quantity of 1-oleoyl-2-(15-HETE) diacylglycerol. An increase in the quantity of 1-stearoyl-2-(15-HETE) diacylglycerol from 6 +/- 1.4 pmol/10(7) cells in the basal state to 12.7 +/- 3.5 after bradykinin was measured by DNICI/MS utilizing a deuterium-labeled analog as an internal standard. Thus, incorporation of 15(S)-HETE into the phosphatidylinositol of these cells led to the release of altered second messengers.

Animals↗
PubMed1991

Quantification of the major urinary metabolite of prostaglandin D2 by a stable isotope dilution mass spectrometric assay.

Prostaglandin D2 (PGD2) has been found to be an important pathophysiological mediator in a number of human disorders. Thus a means to assess the endogenous production of PGD2 is of considerable clinical value. To accomplish this goal, we developed a method for the quantification of the major urinary metabolite of PGD2, 9 alpha, 11 beta-dihydroxy-15-oxo-2,3,18,19-tetranorprost-5-ene-1,20-dioic acid, by gas chromatography/negative ion chemical ionization mass spectrometry. This metabolite was chemically synthesized and converted to an 18O4-labeled derivative for use as an internal standard. Novel derivatization and purification procedures were incorporated in the assay taking advantage of the ability of the lower side chain of this molecule to undergo cyclization at acidic pH to form a hemiketal, gamma-lactone, and uncyclization with methoximation. Precision of the assay is +/- 7% and accuracy is 96%. The lower limit of sensitivity is approximately 50 pg. Normal levels for the urinary excretion of this metabolite in 18 normal adults was found to be 1.08 +/- 0.72 ng/mg creatinine (mean +/- 2SD). Substantial elevations in the urinary excretion of the metabolite were found in clinical situations in which prostaglandin D2 has been shown to be released in increased quantities. Thus, this assay provides a sensitive and accurate method to assess endogenous production of prostaglandin D2 as a means to explore the pathophysiological role of prostaglandin D2 in human disease.

Gas Chromatography-Mass Spectrometry↗
PubMed1991

Biochemical diagnosis of systemic mast cell disorders.

Systemic mastocytosis is characterized by an abnormal proliferation of tissue mast cells. Symptoms of mastocytosis are primarily attributed to the release of mast cell mediators during episodes of systemic activation of the excessive numbers of mast cells. Thus, biochemical evidence for the release of increased quantities of mast cell secretory products can suggest or confirm, depending on the clinical situation, a diagnosis of systemic mastocytosis. A major advantage of the biochemical approach to the diagnosis of systemic mast cell disease is that it has allowed the recognition of a class of patients in whom episodes of systemic mastocyte activation can be unequivocally documented biochemically but in whom clear-cut evidence of abnormal mast cell proliferation is lacking by current histologic criteria. Although the release of increased quantities of mast cell mediators can be demonstrated during episodes of mast cell activation in such patients, mediator levels are usually normal at quiescent times. By contrast, patients with proliferative mast cell disease (mastocytosis) usually exhibit chronic overproduction of mast cell mediators. Mast cell secretory products that can be measured in an attempt to obtain biochemical evidence of systemic mast cell activation include histamine, prostaglandin D2, tryptase, and heparin. The analytical approaches to assessing release of those individual mast cell products are evaluated. In general, the diagnosis and investigation of patients with systemic mast cell activation can best be accomplished by concerted use of histologic examination of key tissues together with analysis of chemical markers of the mast cell.

Flushing↗
PubMed1991

A stable isotope dilution mass spectrometric assay for the major urinary metabolite of PGD2.

1. A sensitive and specific negative ion chemical ionization mass spectrometric assay for the major urinary metabolite of PGD2 has been developed employing a chemically synthesized [18(0)4]-labelled internal standard. 2. The finding that increased urinary excretion of this metabolite occurs in a number of clinical situations suggests that the assay may prove to be a valuable tool to explore the role of PGD2 in the pathophysiology of human disease.

Asthma↗
PubMed1991

Biochemical diagnosis of systemic mast cell disorders.

Systemic mastocytosis is characterized by an abnormal proliferation of tissue mast cells. Symptoms of mastocytosis are primarily attributed to the release of mast cell mediators during episodes of systemic activation of the excessive numbers of mast cells. Thus, biochemical evidence for the release of increased quantities of mast cell secretory products can suggest or confirm, depending on the clinical situation, a diagnosis of systemic mastocytosis. A major advantage of the biochemical approach to the diagnosis of systemic mast cell disease is that it has allowed the recognition of a class of patients in whom episodes of systemic mastocytes activation can be unequivocally documented biochemically but in whom clear-cut evidence of abnormal mast cell proliferation is lacking by current histologic criteria. Although the release of increased quantities of mast cell mediators can be demonstrated during episodes of mast cell activation in such patients, mediator levels are usually normal at quiescent times. By contrast, patients with proliferative mast cell disease (mastocytosis) usually exhibit chronic overproduction of mast cell mediators. Mast cell secretory products that can be measured in an attempt to obtain biochemical evidence of systemic mast cell activation include histamine, prostaglandin D2, tryptase, and heparin. The analytical approaches to assessing release of those individual mast cell products are evaluated. In general, the diagnosis and investigation of patients with systemic mast cell activation can best be accomplished by concerted use of histologic examination of key tissues together with analysis of chemical markers of the mast cell.

Humans↗
PubMed1990

Platelet-vessel wall interactions in individuals who smoke cigarettes.

Our studies have shown that there an increased excretion of urinary metabolites of thromboxane A2 in healthy, young male chronic smokers. This arachidonic acid metabolite from platelets reflects evidence of increased activation in vivo. These data contrast with the ex vivo study of platelets in chronic smokers and point out the fact that selection of cells for ex vivo study may not appropriately reflect the in vivo pathophysiologic situation. The platelet activation related to chronic smoking appears to result from both a direct, non-sympathoadrenally mediated activation which is rapidly inducible and reversible as well as a more persistent activation which long outlasts the smoke exposure. This latter mechanism appears to result from persistent vascular damage as reflected by the enhanced prostacyclin metabolite excretion. The acute, direct effect of smoking on the platelet appears to be a minor component of the altered platelet function. This latter inference may account for the inability in some studies to observe a small incremental, acute change superimposed on the persistently increased platelet reactivity secondary to the enhanced interactions with a damaged vasculature.

Blood Platelets↗
PubMed1990

Inhibition of eicosanoid biosynthesis by glucocorticoids in humans.

Therapeutic doses of glucocorticoids are thought to inhibit prostaglandin and leukotriene formation in humans. Several studies in animals, however, have failed to demonstrate modulation of eicosanoid biosynthesis by steroids in vivo. We administered prednisone (60 mg/day) to eight healthy volunteers and measured eicosanoid formation by a variety of cell types in vivo and ex vivo, using sensitive and specific physicochemical assays. We found that the in vivo course of prednisone failed to inhibit the synthesis of thromboxane A2, prostaglandin I2 (prostacyclin), prostaglandin E2, and leukotriene E4 in vivo and of leukotriene B4 ex vivo. Biosynthesis of leukotriene B4, thromboxane B2, and prostaglandins F2 and E2 by macrophage-rich bronchoalveolar lavage cells was strongly suppressed. These findings indicate that therapeutic regimens of glucocorticoids suppress eicosanoid biosynthesis in human macrophages but not in a number of other cell types with steroid receptors, the capacity for eicosanoid formation, and lipocortin-like material.

Adult↗