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J B Warren

Publications and source records attributed to J B Warren.

At least 37 records · Page 2Linked to original sources
PubMed1993

Nitric oxide, but not interleukin-1, mediates the local blood flow response to lipopolysaccharide in rabbit skin.

Lipopolysaccharide can mimic many aspects of the inflammatory response to gram-negative bacteria. In rabbit and rat skin, lipopolysaccharide induces neutrophil accumulation and an increase in blood flow. Interleukin-1, tumor necrosis factor-alpha and the vasodilator, nitric oxide (NO) have been implicated in the biological responses to lipopolysaccharide and gram-negative bacteria. In the present study, we characterized the local vascular response to E. coli lipopolysaccharide in rabbit skin and investigated its dependence on de novo protein synthesis, NO, interleukin-1 and neutrophils. The local vascular response to the intradermal injection of lipopolysaccharide was determined by measuring changes in local blood flow with a laser-Doppler flowmeter. Injections of lipopolysaccharide (3, 10 and 30 micrograms/site) induced a dose-related increase in blood flow, with a maximum at 2 h. The response to 10 micrograms/site lipopolysaccharide was abolished by co-injection of actinomycin D (4 x 10(-9) mol/site), reduced by 60% by NG-nitro-L-arginine methyl ester (10(-7) mol/site) and suppressed by 82% in rabbits pretreated with dexamethasone (2 mg/kg, i.v.). However, the lipopolysaccharide-induced increase in blood flow was not affected by co-injection of recombinant human interleukin-1 receptor antagonist (7.0 x 10(-11) mol/site) or by systemic neutrophil depletion. These results demonstrate that lipopolysaccharide causes delayed vasodilatation of the rabbit cutaneous microvasculature which depends on protein synthesis and involves in part the release of NO. However, this response does not depend on interleukin-1 or neutrophils. The vasodilator effect of lipopolysaccharide may involve the expression of the inducible form of NO synthase in the vessel wall, through a mechanism independent of interleukin-1.

Animals↗
PubMed1993

Opposing roles of cyclic AMP in the vascular control of edema formation.

Eight agents that increase the intracellular concentration of cyclic AMP were tested for their effect on edema formation. The specificity of the agents for vascular smooth muscle or the endothelium was determined by measuring vasodilation with a laser Doppler flow probe and cAMP production by endothelial cells and vascular smooth muscle cells in culture. The agents were injected intradermally in anesthetized rabbit skin and the local accumulation of 125I-labeled albumin in response to intradermal bradykinin was measured. Iloprost, prostaglandin E1, prostaglandin E2, pituitary adenylate cyclase activating polypeptide (PACAP), and vasoactive intestinal polypeptide (VIP) potentiated bradykinin-induced edema. These same agents also increased blood flow and vascular smooth muscle cAMP concentrations, but did not increase endothelial cell cAMP production. Albuterol suppressed edema formation, did not cause vasodilation, but did increase endothelial cell cAMP concentrations. The phosphodiesterase inhibitor rolipram did not cause vasodilation, but suppressed edema and potentiated the cAMP response to albuterol in cultured endothelial cells. L-Isoproterenol affected both cell types. At a lower concentration L-isoproterenol was a potent stimulus to endothelial cell cAMP production and inhibited edema formation; a higher dose had additional effects on vascular smooth muscle and significantly increased blood flow. These findings support the hypothesis that increasing intracellular cAMP concentrations in vascular smooth muscle promotes edema via increased blood flow. In contrast, increasing cAMP concentrations in endothelium may suppress edema by enhancing the permeability barrier.

Albuterol↗
PubMed1993

Involvement of nitric oxide synthase in the delayed vasodilator response to ultraviolet light irradiation of rat skin in vivo.

1. The role of nitric oxide synthase and cyclo-oxygenase in the skin blood flow response to ultraviolet light B (u.v.B) irradiation was investigated in the rat in vivo. 2. Local skin blood flow changes were measured in the shaved dorsal skin of anaesthetized male Sprague-Dawley rats with a laser Doppler flow probe. 3. u.v.B irradiation caused delayed onset vasodilation and by 18 h basal blood flow increased by 125 +/- 25% (P < 0.05, n = 12 rats, mean +/- s.e. mean). 4. Indomethacin, 3 nmol per site, NG-nitro-L-arginine methyl ester (L-NAME) 100 nmol per site, but not D-NAME 100 nmol per site, injected locally 17.5 h after u.v.B irradiation abolished the 18 h increase in blood flow. 5. The nitric oxide synthase inhibitor L-NAME, NG-monomethyl-L-arginine (L-NMMA) and canavanine, 10 and 100 nmol per site injected at 17.5 h, suppressed significantly the u.v.B 18 h response in a dose-dependent manner. The order of potency was L-NAME > canavanine = L-NMMA. The effect of L-NAME was reversed partially by the co-injection of an excess of L-arginine. 6. Topical application of the corticosteroid, clobetasol 17-propionate, immediately after irradiation inhibited the 18 h u.v.B response in a dose-dependent manner. 7. The delayed onset microcirculatory vasodilation induced by u.v.B involves both nitric oxide synthase and cyclo-oxygenase in this in vivo model. Topical corticosteroids may attenuate the response by inhibiting both prostaglandin and nitric oxide synthesis pathways.

Amino Acid Oxidoreductases↗
PubMed1993

Adenylate cyclase-mediated vascular responses of rabbit aorta, mesenteric artery and skin microcirculation.

1. The importance of adenylate cyclase-mediated vascular relaxation in the macro and microcirculation was assessed in rabbit aortic and coeliac artery bioassay rings in vitro and skin microvessels in vivo. 2. The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP38), the beta-agonist, isoprenaline, and the prostaglandins, PGE1 and PGE2, were compared with the activity of nitroprusside, which acts by stimulating guanylate cyclase. 3. In aortic tissue the relative relaxant potencies were (-log M EC50, 100% = response to nitroprusside 10(-6) M): nitroprusside 7.0, PACAP38 6.8, isoprenaline 6.3; PGE1 and PGE2 were weak constrictors. In coeliac artery rings relative potencies were (-log M EC50, 100% = response to nitroprusside 10(-5) M): PACAP38 6.6, PGE1 6.6, nitroprusside 6.5, PGE2 4.9, and isoprenaline 4.3. 4. Comparative potencies when injected into anaesthetized rabbit skin in vivo were (-log mol/site required to increase blood red cell flux by 75%): PACAP38 13.0, PGE2 10.7, isoprenaline 9.7, PGE1 9.1, nitroprusside < 7. 5. Nitroprusside, the most effective relaxant tested in the aorta, was 10(7) fold less potent than PACAP in its effect on skin blood flow. PGE1 and PGE2 were constrictors of the aorta, of intermediate effect in the coeliac artery, but potent vasodilators of the microcirculation. 6. In this model, the importance of adenylate cyclase-mediated vascular relaxation increases with decreasing vessel size.

Adenylyl Cyclases↗
PubMed1993

Nitric oxide attenuates cardiac myocyte contraction.

Cardiac muscle fibers have microvessels in close proximity, the distance from the nearest capillary being no greater than 8 microns. We performed experiments on isolated, electrically stimulated, contracting guinea pig cardiac myocytes to test whether NO from endothelium or nitrovasodilators or directly superfused in solution might affect myocyte contractility. In endothelium-myocyte coculture experiments, 10(-7) M bradykinin reduced myocyte shortening by 11 +/- 3.5%. This effect was abolished in the presence of NG-nitro-L-arginine methyl ester and was unaffected by indomethacin. Sodium nitroprusside, but not organic nitrovasodilators, reduced myocyte contraction amplitude by 23% at 3 x 10(-5) M. This effect was reversed by methylene blue. Superfusion with NO solution had an effect similar to sodium nitroprusside, as did exposure to 8-bromoguanosine 3',5'-cyclic monophosphate. Thus the present study shows that cardiac myocyte contraction is attenuated by NO, which appears to act via production of guanosine 3',5'-cyclic monophosphate within the myocytes. Because cardiac myocytes in vivo are in such close proximity to endothelium, the effects of endothelial products on cardiac myocyte contractility may be important in myocardial function.

Animals↗
PubMed1992

Pituitary adenylate cyclase activating polypeptide is a potent vasodilator and oedema potentiator in rabbit skin in vivo.

1. The effects of pituitary adenylate cyclase activating polypeptide (PACAP) on microvascular blood flow and plasma protein leakage were investigated in rabbit skin in vivo. 2. Intradermal injection of PACAP38, the 38 amino acid form of the peptide, caused a dose-dependent increase in blood flow measured by a 133Xe clearance technique. An equivalent increase in blood flow was induced by 10(-12) mol per site of PACAP38, 10(-12) mol per site of human alpha-calcitonin gene-related peptide (CGRP) and 10(-10) mol per site of vasoactive intestinal polypeptide (VIP). 3. The vasodilator activity of PACAP38 was not significantly different from that of the 27 amino acid form of the peptide, PACAP27, when measured with a laser Doppler flow meter, causing a 104 +/- 14% compared with 110 +/- 18% increase above basal blood flow at 10(-12) mol per site respectively. 4. At 10(-12) mol per site the effect of PACAP38 was longer lasting than that of CGRP. Blood flow remained significantly increased above control at 2 h with PACAP38 (P less than 0.05) whereas blood flow after intradermal CGRP had returned to control values by this time. 5. PACAP38 injected alone had no significant effect on microvascular leakage of 125I-labelled albumin. However, PACAP38 significantly potentiated bradykinin-induced oedema where it was approximately 100 fold more potent than VIP. 6. Oedema potentiation induced by PACAP38 was not inhibited by indomethacin at a dose which did inhibit potentiation of bradykinin-induced oedema by arachidonic acid.7. PACAP38 is at least as potent as other peptides which have been postulated to be involved in the inflammatory response when tested in rabbit skin in vivo. PACAP may contribute to both the hyperaemia and oedema components of inflammation.

Animals↗
PubMed1992

Endotoxin-induced vasodilatation in anaesthetized rat skin involves nitric oxide and prostaglandin synthesis.

1. The effect of intradermally injected endotoxin on skin blood flow was investigated in anaesthetized male Wistar rats in vivo. 2. Local skin blood flow changes were measured hourly for 6 h in the shaved dorsal skin with a laser-Doppler flow probe and compared to changes in control sites which had been injected with 100 microliters of phosphate-buffered saline. By 3 h, skin blood flow increased above basal by 129 +/- 27% and 186 +/- 29% with 1 and 10 micrograms of endotoxin respectively. Blood flow remained significantly elevated at 6 h, the corresponding figures being 129 +/- 24% and 154 +/- 31% (P less than 0.05, n = 6 rats, mean +/- s.e.mean). 3. In further experiments, the response to 3 micrograms of endotoxin was measured at 4 h and treatment with a cyclo-oxygenase inhibitor, nitric oxide synthase inhibitors or a topical steroid all significantly inhibited this response (P less than 0.05 in each case, n = 6 rats in each group with duplicate sites in each animal). 4. Indomethacin 3 x 10(-9) mol per site injected 3.5 h after injection of endotoxin suppressed the mean 4 h response to endotoxin by 78%; NG-nitro-L-arginine methyl ester (L-NAME) 10(-7) mol per site suppressed the response by 95%; NG-monomethyl-L-arginine (L-NMMA) 10(-7) mol per site suppressed the response by 50%; whereas the D-isomer of NG-monomethyl-arginine 10(-7) mol per site had no significant effect.5. Topical application of the corticosteroid, betamethasone 17-valerate (1% solution) 18 h before injection of endotoxin inhibited the mean 4 h response to endotoxin by 66% and the 6 h response by 48%.6. In the same model, the vasodilator response to arachidonic acid was inhibited by both indomethacin and nitric oxide synthase inhibitors (P<0.05 in each case).7. These data suggest that the microcirculatory vasodilator response to endotoxin and arachidonic acid injected locally involves both nitric oxide synthase and cyclo-oxygenase in this in vivo model.

Amino Acid Oxidoreductases↗
PubMed1992

Inhibition in the rat of nitric oxide synthesis in vivo does not attenuate the hypotensive action of acetylcholine, ATP or bradykinin.

The hypotensive action of acetylcholine in vivo may be dependent on the release of the novel vasorelaxant, endothelium-derived relaxing factor (EDRF)/nitric oxide (NO), by the vascular endothelium. However, using two different inhibitors of NO synthesis, NG-monomethyl-L-arginine (L-NMMA, 100 mg/kg) and NG-nitro-L-arginine methyl ester (L-NAME, 100 mg/kg), we have been unable to attenuate the hypotensive action of intravenous (i.v.) boluses of acetylcholine in anesthetized rats. L-NMMA also failed to alter the hypotensive effect of i.v. bradykinin and adenosine triphosphate (ATP). NO generation by a column of cultured endothelial cells was, however, completely abolished by L-NMMA. The hypotensive effect of acetylcholine was not affected by glibenclamide at a dose which blocks the effect of i.v. cromakalim, a drug which opens ATP-sensitive K+ channels. The rapid hypotensive response to i.v. bolus acetylcholine, ATP and bradykinin remains unexplained.

Acetylcholine↗
PubMed1992

Nitric oxide production within cardiac myocytes reduces their contractility in endotoxemia.

We investigated whether increased nitric oxide (NO) synthase activity within cardiac myocytes contributes to the depressed cardiac contractility observed in endotoxic shock. Isolated ventricular myocytes were studied to examine the effects of substrates and inhibitors of NO synthase on myocyte contractility. When stimulated electrically, the resting length of myocytes from control animals shortened by 5.3 +/- 0.3% (means +/- SE, n = 32). Baseline contraction of myocytes from endotoxin-treated animals was reduced to 3.0 +/- 0.3% (n = 17, P < 0.001). The NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME, 10(-4) M) had no effect on myocytes from control animals, but it increased the contraction of myocytes from endotoxin-treated animals by 40% (fractional shortening increased to 4.3 +/- 0.4%, P < 0.01). Similar results were obtained with NG-methyl-L-arginine. The effect of L-NAME could be reversed by excess L-arginine, but not D-arginine. The effect of endotoxin was abolished by dexamethasone pretreatment. Methylene blue also reversed the effects of endotoxin but had toxic effects on myocytes. Agents that either prevent synthesis or the effects of NO reverse the depression of myocyte contraction seen following endotoxin treatment.

Animals↗
PubMed1992

Pituitary adenylate cyclase activating polypeptide is a potent vasodilator in humans.

The vasodilator effect of the novel peptide pituitary adenylate cyclase activating polypeptide (PACAP) was investigated in humans. Forearm blood flow was measured in six healthy men by venous occlusion plethysmography. Infusion of PACAP into the brachial artery at 0.01, 0.1, 1, 3, and 10 pmol/min produced a dose-related increase in forearm blood flow in the cannulated arm from 2.8 +/- 0.6 to 8.6 +/- 2.4 ml/100 ml/min at the highest dose (mean +/- SEM, p less than 0.05). In a subsequent experiment, where the highest dose of PACAP was repeated after a 36 min interval, there was no tachyphylaxis of the forearm blood flow response, with the forearm blood flow increasing by 129 +/- 9% during the first infusion and 128 +/- 31% during the second infusion (N.S.). In further experiments, microvascular blood flow was measured by a laser-Doppler flow probe to compare the effects of intradermally injected PACAP, vasoactive intestinal polypeptide (VIP), and calcitonin gene-related peptide (CGRP). When injected into the skin of normal volunteers at 10(-12) to 10(-11) mol/site, each peptide caused a rapid flare lasting 2-3 min, which became erythematous after 5 min. At 10(-12) mol/site, intradermally injected PACAP and VIP caused a maximum increase in skin blood flow at 15 min of 379 +/- 96 and 307 +/- 121% (% increase above basal +/- SEM), respectively, and these responses were not significantly affected by oral aspirin (600 mg) taken 1.5 h beforehand. The vasodilation induced by PACAP at 10(-12) mol/site lasted approximately 6 h, whereas the effect of the same dose of CGRP and VIP lasted less than 2 h. These data suggest that PACAP is a potent and long-lasting vasodilator in humans.

Adult↗
PubMed1991

Anaphylaxis.

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Anaphylaxis↗
PubMed1991

Glucocorticoids induce endothelin release from vascular smooth muscle cells but not endothelial cells.

Vascular smooth muscle cells in culture are capable of secreting endothelin which is a vasoconstrictor and mitogenic peptide. The effect of glucocorticoids on endothelin release from vascular smooth muscle cells of the rat and rabbit aortas was investigated. Micromolar concentrations of dexamethasone and cortisol caused a 2 to 5-fold increase in endothelin release from the two smooth muscle cell types but no such response was observed in endothelial cells of the bovine aorta. Glucocorticoids appear to selectively induce endothelin release from vascular smooth muscle cells and this may be relevant to glucocorticoid-induced hypertension.

Animals↗
PubMed1991

Pituitary adenylate cyclase-activating polypeptide: a novel, long-lasting, endothelium-independent vasorelaxant.

The vasoactivity of the 27- and 38-amino acid forms of the novel peptide pituitary adenylate cyclase-activating polypeptide (PACAP) was tested in vitro. Both forms of PACAP caused endothelium-independent vasodilation (assayed by their vasodilator action on rabbit aorta). When superfused for 1 min the relaxation EC50 of PACAP27 was 23 +/- 8 nM and of PACAP38 was 152 +/- 66 nM. PACAP was 100-fold more potent than vasoactive intestinal polypeptide (VIP) (PACAP27 shows 68% amino acid sequence homology with VIP), and had a prolonged duration of action, a 1 min exposure to 1 microM PACAP27 lasting 135 +/- 7 min and to 1 microM PACAP38 108 +/- 3 min. Adenylate cyclase activity in homogenates of rabbit aortic smooth muscle cells was increased by PACAP27 and PACAP38 with EC50s of 4.4 and 0.73 nM, respectively. PACAP27 and PACAP38 are potent, long-lasting, endothelium-independent vasodilators.

Adenylyl Cyclases↗
PubMed1991

Cytokine stimulated endothelin release from endothelial cells.

Endothelin release from bovine endothelial cells of the aorta, pulmonary artery, and retinal microvessels was measured in response to various cytokines. Transforming growth factor beta (0.05-5 ng/ml) was found to be a potent stimulator (3-4 fold increase) of endothelin secretion in all three cell types. Tumour necrosis factor alpha (0.1-10 ng/ml) and interferon gamma (8-800 U/ml) had a small (1.5-2 fold increase) but significant effect on endothelin secretion from endothelial cells of large vessels but not the retinal microvessels. Interleukin-1 beta, Interleukin-6 and interleukin-8 at various doses did not affect endothelin secretion. These effects were observed at various time points from 6-24 hrs and indicate that of the cytokines tested, only transforming growth factor beta has a potent effect on endothelin release from endothelial cells of different organs.

Aorta↗
PubMed1991

Biological calcium absorption edge imaging using monochromatic synchrotron radiation.

Soft X-ray contact absorption edge images of unfixed, unstained biological specimens were made using monochromatic synchrotron radiation. X-ray contact replicas of unfixed, hydrated biological specimens at the nitrogen absorption edge and above and below the CaLIII absorption edge were compared to comparative conventional morphological and elemental high-resolution imaging methods (scanning and transmission electron microscopy, TEM-histochemistry and TEM-X-ray microanalysis). Soft X-ray absorption edge images made above the calcium absorption edge clearly revealed morphological detail and identified regions ladened with calcium as verified by TEM histochemistry of identical spores. Similarly, nitrogen absorption edge images identified residual nitrogenous material in the spore resuspension medium, and non-viable spores with nitrogen loss due to protoplast disaggregation.

Bacillus subtilis↗
PubMed1991

Assessment of MK-467, a peripheral alpha 2-adrenergic receptor antagonist, with intravenous clonidine.

The activity of MK-467, a new peripherally acting alpha 2-antagonist, was assessed in volunteers by a randomized, double-blind, crossover design. One hour after administration of either 15 mg or 30 mg MK-467 or placebo, 200 micrograms clonidine was given intravenously and observations were made for a further 8 hours. Clonidine reduced plasma norepinephrine levels to 79% +/- 7% of that of control 1 hour after infusion, an effect that was antagonized by low-dose MK-467 (p less than 0.05). Mean systolic blood pressure increased by 4 mm Hg in the first hour after the 30 mg dose of MK-467 (p less than 0.01), although there was no significant difference between the 3 study days in the maximal clonidine-induced decrease in systolic pressure, diastolic pressure, or heart rate. Clonidine induced a peak increase in mean blood glucose of 13%, which was antagonized by both doses of MK-467 (p less than 0.05). Plasma insulin was suppressed by clonidine from 72 +/- 14 to 47 +/- 7 IU.L-1, an effect antagonised by both doses of MK-467 (p less than 0.05 in each case). MK-467 had no effect on clonidine-induced increased drowsiness, xerostomia, or increase in growth hormone secretion, which is consistent with it being a peripherally acting specific alpha 2-antagonist. The small effect of MK-467 on clonidine-induced changes in plasma glucose and insulin suggests that peripheral alpha 2-adrenergic receptors play only a minor role in normal glucose homeostasis.

Administration, Oral↗