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Biomedical subjects

G M Walsh

Publications and source records attributed to G M Walsh.

At least 73 records · Page 4Linked to original sources
PubMed1989

Flow-cytometric analysis of increased IgE uptake by normal eosinophils following activation with PAF-acether and other inflammatory mediators.

Using flow-cytometric analysis and a fluorescein-conjugated anti-IgE antibody, we have investigated whether normal-density human eosinophils will bind greater amounts of native IgE following activation with platelet-activating factor (PAF), leukotriene B4 (LTB4) and histamine. Incubation with PAF resulted in a large dose- and time-dependent increase in IgE binding, optimal at 10(-7) M and 30 min, respectively. LTB4 and histamine gave lower but significant increases in IgE binding. Enhanced binding of IgE by activated normal-density eosinophils is probably a consequence of enhanced Fc epsilon RII receptor expression, suggesting a functional role for this receptor in allergic inflammation.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1989

The activated eosinophil in allergy and asthma.

Our studies indicate that human eosinophils can be activated in terms of up-regulation of surface receptors, increased membrane lipid generation, and enhanced cytotoxicity by a variety of pharmacological mediators, through IgE-, IgG-, and complement-dependent pathways. PAF is an impressive activator of eosinophil function and is the most potent chemotactic mediator for eosinophils so far described. It is not selective in that neutrophils are also attracted by PAF. In our hands, IL-1, IL-2, granulocyte/macrophage-colony stimulating factor, tumor necrosis factor, interferon-gamma, and IL-5 tested over a wide concentration range gave very weak chemotaxis for eosinophils in vitro. Nevertheless, in vivo infiltration of eosinophils into the site of allergic tissue reactions is closely associated with the local accumulation of activated (CD4+, IL-2 rec+) T cells. We suggest, therefore, that the selective eosinophil infiltration seen in allergic inflammation may result from the initial recruitment and activation of granulocytes by lipid mediators and the subsequent selective activation of eosinophils by cytokines.

Asthma↗
PubMed1988

Role of chemical mediators after antigen and exercise challenge in children with asthma.

Changes in chemical mediators after antigen challenge and exercise challenge tests were studied in children with asthma. Chemical mediators studied after antigen challenge and exercise challenge included histamine, leukotrienes (LTB4, LTC4, and LTD4), and neutrophil chemotactic factor of anaphylaxis (NCA). The pharmacologic modification of immediate and late-phase reactions was evaluated for procaterol (beta 2-agonist), cromolyn sodium, and prednisolone. Histamine levels were noted to rise in patients who had a dual response of a mild to moderate nature, but did not change in patients who had severe asthma. During exercise challenge cromolyn sodium inhibited both immediate and late-phase reactions but also inhibited plasma generation of NCA. Prednisolone, on the other hand, did not affect immediate reactions, but blocked late-phase reactions to exercise and also decreased NCA generation. Procaterol inhibited the generation of LTD4 and also inhibited NCA when compared with placebo. Exercise challenge did not alter levels of plasma histamine or of LTB4 or LTC4.

Adolescent↗
PubMed1988

Leukotriene C4 generation from human eosinophils stimulated with IgG-Aspergillus fumigatus antigen immune complexes.

Sepharose beads coated with IgG stimulate eosinophils to produce leukotriene C4 (LTC4). This observation has been extended with specific immobilized IgG/antigen immune complexes to elicit mediator generation. An extract of Aspergillus fumigatus was covalently coupled to Sepharose beads and incubated with the IgG fraction of immune serum from patients with allergic bronchopulmonary aspergillosis. These beads elicited generation of 7.72 +/- 1.7 pmol of LTC4 immunoreactive material (n = 5) from 1 X 10(6) normal eosinophils of greater than 86% purity, and significantly less LTC4 (0.73 +/- 0.19 pmol per 10(6) cells; n = 3) was produced by eosinophils after incubation with beads treated with IgG from normal nonimmune serum. The maximum antibody-dependent release achieved represented approximately 20% of that induced by the calcium ionophore (A23187). LTC4 was measured by radioimmunoassay and validated by reverse-phase high-performance liquid chromatography. The amount of LTC4 generated was dependent on the concentration of A. fumigatus-specific IgG, and mediator release was completely abolished by prior adsorption of the IgG fraction onto Sepharose-protein A (Staphylococcus aureus). Grass pollen-specific IgG antibody/antigen complexes, in combination with Sepharose beads, also triggered generation of LTC4 immunoreactive material. There was no evidence to suggest that IgE/A. fumigatus immune complexes triggered LTC4 generation, although IgE myeloma protein, in association with Sepharose beads, was a weak stimulus. The efficacy of the IgG immune complex-dependent stimulation of eosinophils suggests a possible physiologic mechanism whereby these cells could participate in the inflammatory changes associated with allergic bronchopulmonary aspergillosis and similar allergic disorders.

Antigen-Antibody Complex↗
PubMed1988

Simultaneous determination of ventricular function and systemic hemodynamics in the conscious rat.

This study describes a method that utilizes a combination of the Millar transducer and Columbus thermistor in the conscious, spontaneously hypertensive rat and that permits simultaneous evaluation of the effects of cardiovascular agents on ventricular performance and systemic hemodynamics. Left ventricular end diastolic pressure (LVEDP, mmHg) and LV dp/dt (mmHg/sec) were measured with a Millar transducer inserted into the left ventricle of spontaneously hypertensive rats under ether anesthesia. Cardiac output (CO, ml/min) was measured by thermodilution (Columbus Instruments) with a thermocouple in the thoracic aorta via the femoral artery. Mean arterial pressure (MAP, mmHg) was measured via a catheter in the other femoral artery. All cardiovascular parameters measured were shown to attain a steady state within 3 hr after cessation of ether administration. Infusion of the beta adrenergic receptor agonist isoproterenol increased LV max dP/dt, heart rate (HR), and CO, and decreased arterial blood pressure and peripheral resistance. Administration of propranolol resulted in decreased HR, LV dP/dt and CO. The results show that this model was stable over an extended period of time and was responsive to standard inotropic agents. Thus, the combined use of the Millar transducer and the Columbus thermistor appears suitable for the assessment of acute pharmacological interventions on cardiovascular function in the conscious rat.

Animals↗
PubMed1988

Effects of verapamil and nifedipine on systemic hemodynamics in spontaneously hypertensive rats.

Verapamil (1 mg/kg, i.v.) and nifedipine (0.3 mg/kg, i.v.) were tested at equi-antihypertensive doses for systemic hemodynamic responses in conscious spontaneously hypertensive rats (SHR) using the Fick method. Systemic hemodynamic effects of these agents were also evaluated in areflexic, spinal cord-transected and vagotomized SHR using the electromagnetic flowmetry technique. Both verapamil and nifedipine lowered mean arterial pressure (MAP:verapamil = -24%; nifedipine = -28%) in conscious SHR by decreasing total peripheral resistance (TPR:verapamil = -48%; nifedipine = -59%) with a concomitant rise in cardiac output (CO: verapamil = 48%; nifedipine = 86%) and stroke volume (SV:verapamil = 54%; nifedipine = 65%), but verapamil prevented tachycardia, whereas nifedipine increased heart rate (HR:13%). Verapamil and nifedipine also altered systemic hemodynamics in the areflexic SHR; verapamil reduced MAP (-31%) by reducing CO (-18%) with associated bradycardia (-25% HR), whereas nifedipine also lowered MAP (-21%) by decreasing TPR (-18%) without changes in CO and HR. It is concluded that, firstly, the antihypertensive action of verapamil and nifedipine in conscious SHR is due to systemic vasodilation that is associated with reflexly increased CO; secondly, that verapamil has a direct negative chronotropic effect, but nifedipine appears to be devoid of such an effect, and finally that the ability of verapamil to decrease TPR may depend upon resting sympathetic tone.

Animals↗
PubMed1988

Effects of nedocromil sodium (Tilade) on the activation of human eosinophils and neutrophils and the release of histamine from mast cells.

The ability of nedocromil sodium, a new anti-inflammatory agent for the treatment of asthma, to inhibit activation of human eosinophils and neutrophils in vitro, has been studied using an adherence reaction (the "rosette" technique) as well as a cytotoxicity assay. We have also investigated the capacity of nedocromil sodium to inhibit IgE-dependent histamine release from human lung mast cells. The drug was a potent inhibitor (IC50 approx 5 x 10(-9)M) of fMLP-induced enhancement of eosinophil and neutrophil complement (C3b) and IgG (Fc) rosettes. There was also a comparable inhibition of enhancement, by fMLP, of eosinophil and neutrophil cytotoxicity (for complement-coated schistosomula of Schistosoma mansoni). Although nedocromil sodium also inhibited histamine release from human lung mast cells in a dose-dependent fashion its activity was relatively weak (IC30 5 x 10(-6)M) compared to its effect on granulocytes. These experiments support the view that the principal mode of action of nedocromil sodium is its capacity to inhibit the activation of inflammatory cells.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1987

Enhanced potency dipeptide glycol renin inhibitors: studies in vitro and in the conscious rhesus.

We prepared a series of novel dipeptide amides of the formula Boc-Phe-Leu-X, where X is a 3-amino-3-alkyl-1,2-propanediol with lower alkyl substitutions at C-1, in order to probe accessory binding sites in the enzyme renin. This approach was successful in generating potent inhibitors of human and hog renin in vitro. Moreover, these inhibitors were able to effect in vivo reduction of plasma renin activity (PRA) in the conscious salt-depleted rhesus monkey (i.v. route); this effect was related to the size of the C-1 alkyl group.

Animals↗
PubMed1987

Cardiovascular effects of chronic high-dose atriopeptin III infusion in normotensive rats.

Seventy-eight Sprague-Dawley rats received continuous intravenous infusions of either atriopeptin III (APIII), 60 micrograms/kg/hr, or distilled water vehicle for a period of 7 days by means of osmotic minipumps. On Day 7 approximately one-half of the animals (20 vehicle-treated rats and 21 APIII-treated rats) were instrumented for evaluation of cardiac function and terminated for measurement of heart weight. The minipumps remained in place during the evaluation of cardiac function. Also on Day 7, the osmotic pumps were removed from the remaining animals and an additional 7 days were allowed to elapse before heart weight and cardiac function were evaluated. Mean arterial blood pressure (MAP) of rats receiving APIII for 7 days was significantly lower (-9%, p less than 0.05) than that of rats receiving vehicle for 7 days. In addition, reductions (p less than 0.05) of total ventricular weightdry (-7%), left ventricular weightdry (-8%), and right ventricular weightdry (-9%) were observed in the APIII-treated rats (all ventricular weights are normalized for body weight). Hematocrit (HCT) was significantly higher (13%, p less than 0.05) in the APIII-treated group. Chronic APIII infusion did not influence ventricular performance nor did it affect regional vascular resistances. Seven days after termination of the APIII infusion the differences in MAP and HCT between vehicle-treated and APIII-treated animals were no longer evident. Partial recovery of the effect on heart weights was apparent, with total ventricular weightdry and left ventricular weightdry remaining slightly reduced (-4 and -5%, respectively; p less than 0.05). No differences were found between the two recovery groups for any index of cardiac function. In separate experiments, it was demonstrated that APIII, 60 micrograms/kg/hr iv, caused a significant increase in urine volume (p less than 0.05 relative to vehicle) during the initial 24 hr of infusion. The results indicate that chronic infusion of a large diuretic dose of APIII exerts relatively little influence on overall cardiovascular function in normotensive rats.

Animals↗
PubMed1987

Disodium cromoglycate inhibits activation of human inflammatory cells in vitro.

Recent clinical studies indicate that disodium cromoglycate (DSCG) may have a direct effect on inflammatory cells because the drug reversed various changes in leukocyte function, such as increased membrane-receptor expression and enhanced cytotoxic capacity observed in peripheral white blood cells from subjects with asthma undergoing allergen-inhalation challenge. In the present study, we have demonstrated that DSCG, at low concentrations (a concentration of drug required to produce 50% inhibition, approximately 10(-8) mol/L) and in a time-dependent fashion, directly inhibited the activation in vitro of human neutrophils, eosinophils, and monocytes. Peripheral blood leukocytes were incubated with the synthetic chemoattractant, formyl-methionyl-leucyl-phenylalanine (at an optimal concentration of 10(-8) mol/L), and activation was assessed by measuring increases in the percentages of complement and IgG (Fc) rosettes as well as the enhanced capacity of these cells to kill target organisms (schistosomula of Schistosoma mansoni). DSCG at a concentration of 10(-7) mol/L totally inhibited both the formyl-methionyl-leucyl-phenylalanine-induced enhancement of complement and IgG rosettes, as well as increased schistosomular killing. These observations indicate that DSCG directly inhibits the secretory properties of inflammatory cells and that in turn might have important implications in modulating mechanisms contributing to the inflammatory component of asthma and allergic disease. It may also help to explain why compounds with considerably greater mast cell stabilizing properties than DSCG have been so disappointing when they are evaluated clinically.

Cromolyn Sodium↗
PubMed1987

Leukotriene B4 generation by human neutrophils following IgG-dependent stimulation.

It has previously been shown that human neutrophils generate substantial quantities of LTB4 when stimulated with the calcium ionophore, A23187, or with unopsonized zymosan. We now report that normal human neutrophils produced substantial quantities of LTB4 (measured by radioimmunoassay and validated by RP-HPLC) when incubated with large non-phagocytosable IgG-coated beads (Sepharose 4B). LTB4 was identified in both the extra and intracellular compartments. The production of LTB4 was dependent upon the number of IgG-coated particles and the concentration of IgG bound to the beads. Release was maximal after a 15-30 min incubation time and was enhanced by prior activation of the neutrophils with the synthetic bacterial product f-met-leu-phe. Comparable LTB4 production was also observed when neutrophils were incubated with antigen (Aspergillus fumigatus)-coated beads sensitized with purified IgG obtained from the sera of patients with allergic bronchopulmonary aspergillosis. These results suggest a further mechanism by which neutrophils may be activated to produce inflammatory mediators in the tissues.

Antigens, Fungal↗
PubMed1987

Chemotactic factor-induced low density neutrophils express enhanced complement (CR1 and CR3) receptors and increased complement-dependent cytotoxicity.

We have studied chemotactic factor-induced 'complement receptor enhancement' to determine whether changes in receptor expression and complement-dependent cytotoxicity were associated with alterations in cell density. Ficoll-Paque separated normal human neutrophils (greater than 90%), when further fractionated on discontinuous metrizamide (MTZ) gradients (18, 19, 20, 21, 22, 23% MTZ), consistently gave two major bands at the 20/21% and 21/22% interfaces. Incubation with the synthetic chemotactic peptide, N-formyl-methionyl-leucyl-phenylalanine (fMLP (10(-8) M)), converted virtually all neutrophils to low density cells sedimenting on MTZ at the 18/19% and 19/20% interfaces. There was a time-dependent change of density after fMLP-stimulation which was maximal at 30 min, with cells reverting towards normal density by 60 min. Control unstimulated cells did not alter their density at any of the time points examined. Activated, low density neutrophils had increased expression of CR1 and CR3 (as shown by flow cytometry and the uptake of 125I-F(ab')2 monoclonal anti-CR1 antibody (E11)). These cells also showed enhanced cytotoxic capacity in vitro for helminthic targets (schistosomula of Schistosoma mansoni) opsonized with autologous complement. There were highly significant correlations between cell density and anti-CR1 uptake (P less than 0.001), and between schistosomular killing and change in density (P less than 0.001). Increased CR1 expression also correlated with enhanced helminthicidal capacity of neutrophils (P less than 0.001). Complement dependent cytotoxicity was partially reduced after treatment of cells with anti-human CR1 and/or CR3 antibodies, but only in the presence of a second antibody. These findings indicate that chemotactic factor-induced complement receptor enhancement of human neutrophils is associated with a decrease in cell density and increased complement-dependent cytotoxicity (CTX).

Animals↗
PubMed1986

Effect of disodium cromoglycate on activation of human eosinophils and neutrophils following reversed (anti-IgE) anaphylaxis.

Immunological release of histamine and lipid mediators is known to occur when basophils, contained in whole blood human leucocytes, are incubated with anti-IgE (reversed anaphylaxis). In the present study we show that IgE-dependent stimulation of basophils was associated with activation of bystander eosinophils and neutrophils, as assessed by enhanced complement (C3b) and IgG (Fc) rosettes, and increased cytotoxicity for complement-coated schistosomula of Schistosoma mansoni. These changes in eosinophil and neutrophil function were totally inhibited in a dose-dependent fashion by prior incubation with disodium cromoglycate (DSCG). In all in vitro systems examined, complete inhibition of enhancement was observed with concentrations as low as 10(-7) moles/l. In contrast, DSCG had no effect on histamine release, or the percentage of rosettes or cytotoxicity prior to anti-IgE stimulation. These results suggest that DSCG inhibits activation of inflammatory cells consequent to an IgE-dependent stimulus.

Anaphylaxis↗
PubMed1986

The requirements for transferrin-dependent adherence of human granulocytes to pollen grains.

Human granulocyte/pollen binding protein (GPBP), previously identified as serum transferrin, promoted prolonged firm adherence of neutrophils to Timothy grass pollen. Some characteristics of this adherence reaction are reported. GPBP-induced binding was time-, temperature- and concentration-dependent. Maximal adherence was observed by 2 h and was only slightly decreased at 18 h. The optimal temperature for adherence was 37 degrees C. Concentrations of GPBP as low as 1.25 microgram/ml gave significantly greater binding than the albumin or lactoferrin control. Eosinophils, monocytes and lymphocytes did not appear to participate in GPBP-induced pollen binding reactions at concentrations up to 300 micrograms/ml. In the presence of GPBP, neutrophils adhered to a range of grass, weed and tree pollens. These included timothy, meadow, false oat, rye, giant and short ragweed, plantain, silver birch and ash. GPBP did not facilitate the adherence of granulocytes to inert particles of similar size such as Sephadex beads and agarose. The adherence was Mg++- but not Ca++-dependent and was not inhibited by a monoclonal antibody to the transferrin receptor (OKT9). Transferrin/GPBP did not bind to either neutrophils or pollen grains. A purified commercial transferrin reacted in all respects like GPBP in these pollen binding studies. These observations indicate that GPBP/transferrin-induced adherence of granulocytes to pollen grains is a hitherto unrecognized property of transferrin which appears unrelated to iron transport or the conventional transferrin receptor.

Antibodies, Monoclonal↗
PubMed1986

Selective vasodilation produced by renal denervation in adult spontaneously hypertensive rats.

The kidneys of adult male spontaneously hypertensive rats (SHR) were denervated, and systemic and regional blood flows were measured 3 to 5 hours or 5 days after denervation. Arterial pressure was reduced 20 to 27% in denervated SHR during both periods compared with that in sham-operated SHR (iliolumbar blood vessels painted with phenol). This hypotensive response was produced by a 32 to 35% reduction in total peripheral resistance. At 3 to 5 hours and at 5 days, a major decrease in total peripheral resistance was produced by vasodilation in the kidneys and splanchnic organs. Acute urine output, sodium excretion, and plasma renin activity in response to a saline load were not different between sham-operated and denervated SHR. The decreased total peripheral resistance in denervated SHR may have been secondary to a decreased central sympathetic nerve activity revealed by a decreased maximum response to ganglionic blockade. The results suggest that a pathophysiological link may exist between the kidneys and splanchnic organs in genetic hypertension and that specific efferent antiadrenergic or antiafferent nerve therapy, or both, in the kidney may lead to substantial specific decreases not only in renal vascular resistance but also in splanchnic vascular resistance and total peripheral resistance.

Animals↗
PubMed1986

Enhancement of leukocyte cytotoxicity after exercise-induced asthma.

We have previously shown that there were elevations of neutrophil chemotactic activity (NCA) and increases in the percentages of neutrophil and monocyte complement rosettes after exercise-induced asthma (EIA). These observations suggested that leukocyte activation may occur after EIA, possibly as a result of the release of mast-cell-associated mediators. In the present study, we have attempted to establish whether neutrophils and monocytes are functionally altered after EIA as assessed by changes in their cytotoxic capacity. Cytotoxicity was assessed by a direct visual killing assay using opsonized (complement-coated) schistosomula of Schistosoma mansoni as target organisms. Neutrophils and mononuclear cells obtained from 8 patients after exercise-induced asthma (EIA+ve) had increased cytotoxicity for opsonized schistosomula for as long as 60 min after exercise. These changes were preceded by elevations in the concentrations of serum high molecular weight NCA (which were maximal at 10 min after exercise). In asthmatic patients who did not develop exercise-induced asthma (EIA-ve), no significant increases in neutrophil or mononuclear cell killing of schistosomula, or serum NCA concentrations, were observed. There was a highly significant correlation (p less than 0.001) between the reduction in FEV1 and the increases in neutrophil cytotoxicity. In 5 EIA+ve patients, administration of disodium cromoglycate (cromolyn) prior to the exercise task inhibited both the enhancement in neutrophil and mononuclear cell cytotoxicity, as well as the elevations in circulating NCA and the reductions in FEV1.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗