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Biomedical subjects

F M Cunningham

Publications and source records attributed to F M Cunningham.

At least 37 records · Page 2Linked to original sources
PubMed2000

Cloning of equine chemokines eotaxin, monocyte chemoattractant protein (MCP)-1, MCP-2 and MCP-4, mRNA expression in tissues and induction by IL-4 in dermal fibroblasts.

We report the cloning of four equine CC chemokines, eotaxin, monocyte chemoattractant protein (MCP)-1, MCP-2 and MCP-4, which show high levels of identity with their respective homologous sequences in other species. Using a multiplex RT-PCR, we have studied the constitutive mRNA expression of these four CC chemokines in skin, lung, liver, spleen, jejunum, colon and kidney of normal adult horses and compared this data with the eosinophil counts in the same samples. We demonstrate that eotaxin mRNA is only expressed in jejunum and colon, where there are large numbers of eosinophils suggesting that eotaxin might be recruiting eosinophils in the normal digestive tract of the horse. MCP-1 and MCP-4 are expressed in all tissues whereas MCP-2 is only found in some samples of lung, spleen, liver and kidney. We also report the early induction (2h) of equine eotaxin and MCP-4, and the up-regulation of MCP-1 by interleukin-4 in dermal fibroblasts, suggesting these chemokines might be involved in equine skin allergic diseases.

Amino Acid Sequence↗
PubMed2000

Retrospective study of the relationships between age, inflammation and the isolation of bacteria from the lower respiratory tract of thoroughbred horses.

A total of 1235 tracheal aspirates taken from 724 thoroughbreds in race training, aged from two to 10 years, were examined cytologically and bacteriologically. An inflammation scoring system on a scale of 0 to 9 was devised to allow the severity of lower airway disease to be assessed from the cytological results. The inflammation scores were closely related to the isolation of bacteria (P<0.001), and the most common bacterial isolates were Streptococcus zooepidemicus, Streptococcus pneumoniae and Pasteurella/Actinobacillus-like species. Lower airway disease was less common in older horses (P = 0.031), and the groups at highest risk were the two- and four-year-olds. Lower airway inflammation was more common in the four-year-olds at National Hunt yards than in the four-year-olds at flat racing yards (P = 0.040, odds ratio = 3.80).

Actinobacillus↗
PubMed2000

Differential activation of platelets from normal and allergic ponies by PAF and ADP.

OBJECTIVE AND DESIGN: Altered platelet responsiveness has been demonstrated in human atopic dermatitis. This study has compared the in vitro function of platelets from normal ponies and those with the allergic skin disease, sweet itch. SUBJECTS: Ponies with a clinical history of sweet itch and normal ponies were used as blood donors. METHODS: PAF and ADP-induced platelet aggregation was measured and TxB2 production quantitated at the time of maximal aggregation; 12-HETE was additionally measured in some samples. Agonist-induced release of 3[H]5-HT was also studied. RESULTS: Although both PAF and ADP caused equine platelet aggregation, only PAF stimulated eicosanoid and 5-HT release. There were no differences between the responses of platelets from allergic and normal ponies to PAF or ADP (analysis of variance). CONCLUSIONS: There is no evidence of altered platelet responsiveness in ponies with sweet itch. The profile of responses to PAF and ADP suggest differential activation of intracellular signalling pathways in equine platelets.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed2000

Endotoxin and dietary amines may increase plasma 5-hydroxytryptamine in the horse.

Uptake of 5-hydroxytryptamine (5-HT) into platelets is an important mechanism by which low plasma concentrations are maintained, and platelet activation may therefore result in significant release of this vasoconstrictor. The present study examined the kinetics of active uptake of radiolabelled [3H]5-HT by washed equine platelets in vitro, and investigated the effects on this process of 4 other naturally occurring monoamines which may be released from the caecum in conditions of carbohydrate overload. The release of [3H]5-HT by platelets was also studied, since platelet accumulation and activation has been associated with acute laminitis. Release of [3H]5-HT was measured in response to platelet activating factor (PAF), unlabelled 5-HT and the indirect activation of platelets by endotoxin in the presence of blood leucocytes. Km value for the uptake of 5-HT by equine platelets was 2.4 +/- 0.6 micromol/l and the Vmax was 8.3 +/- 0.6 pmol [3H]5-HT/10(7) platelets/min. The rate of uptake of 5 micromol/l [3H]5-HT was significantly decreased by the uptake inhibitors fluvoxamine and clomipramine. The 4 other monoamines examined all inhibited the uptake of [3H]5-HT in a noncompetitive manner, decreasing Vmax by between 17 and 82%. Incubation of platelets with LPS (0.1 mg/ml) in the absence of leucocytes did not result in significant release of [3H]5-HT; however, in the presence of leucocytes 3.8 +/- 1.7 pmol [3H]5-HT/10(7) platelets (mean +/- s.e.) were released. This release was significantly inhibited by parthenolide and WEB2086, but not by aspirin. This suggests that PAF from activated leucocytes was responsible for the 5-HT release. These data show that 5-HT uptake by equine platelets is a saturable process operating most efficiently at substrate concentrations in the low micromolar range. The noncompetitive inhibition of 5-HT uptake by other naturally occurring monoamines may result in increased plasma concentrations of 5-HT, as would its release by endotoxin. Such a rise in plasma 5-HT concentrations may contribute to selective vasoconstriction in the equine digital circulation.

Amines↗
PubMed2000

Differential localization of protein kinase C isotypes in equine eosinophils and neutrophils.

Phorbol esters, which activate protein kinase C (PKC), stimulate equine eosinophil superoxide production and adherence. After showing that superoxide production could be inhibited by the nonselective PKC inhibitors, staurosporine and bisindolymaleimide I, the PKC isotypes in equine eosinophils were characterized, because evidence suggests that individual isotypes may play distinct roles in regulating eosinophil function. Western blots demonstrated that equine eosinophils expressed PKC alpha, beta, delta, epsilon, iota, and zeta. However, unlike the equine neutrophil, the majority of the PKC was detected in the particulate fraction of the cell. Despite this unusual location, the PKC in equine eosinophils was activatable, suggesting that it is functionally competent. The regulatory role of PKC in equine eosinophils may reflect the association of activity with the particulate fraction and the profile of isotype expression.

Animals↗
PubMed1999

Agonist-induced adherence of equine neutrophils to fibronectin- and serum-coated plastic is CD18 dependent.

Adherence to vascular endothelium and extracellular matrix proteins is a pre-requisite for neutrophil accumulation at sites of inflammation. In this study, equine neutrophil adherence to fibronectin and autologous serum-coated plastic in response to PAF, hrIL-8, hrC5a and PMA has been measured. In addition, the mechanisms involved have been investigated using monoclonal antibodies (MoAbs) against the beta2 integrin CD18. PAF and hrC5a caused similar, concentration dependent, increases in adherence to fibronectin- and serum-coated plastic (maximum responses 19 +/- 4% and 19 +/- 3% for PAF and 15 +/- 4% and 16 +/- 2% for hrC5a on fibronectin- and serum-coated plastic, respectively). Adherence in response to PMA, although not reaching a maximum over the time course studied, was of a similar magnitude on the two surfaces (41 +/- 1% and 38 +/- 2% with 10(-7) M PMA on fibronectin- and serum-coated plastic, respectively). In contrast, the maximum adherence caused by hrIL-8 was significantly lower on fibronectin- than on serum-coated plastic (9 +/- 3% vs. 17 +/- 2%; 10(8) x M hrIL-8). Pre-incubation with MoAbs against CD18 (H20A and 6.5E) caused concentration related inhibition of stimulus-induced adherence to both fibronectin- and serum-coated plastic. Equine neutrophil adherence in response to PAF, hrIL-8, hrC5a and PMA therefore appears to be mediated by a CD18 dependent mechanism.

Animals↗
PubMed1999

Characterisation of lymphocyte subpopulations in the skin and circulation of horses with sweet itch (Culicoides hypersensitivity).

Circulating lymphocyte numbers are elevated in horses with the allergic skin disease sweet itch and skin lesions are typified by an infiltrate of eosinophils and mononuclear cells, the latter of which have not been fully characterised. The aim of the present study was to characterise the lymphocyte subpopulations in the circulation and skin of ponies with sweet itch by flow cytometry and a newly developed modified alkaline phosphatase immunohistochemical technique. Sweet itch ponies were found to have significantly greater numbers of circulating CD5+ and CD4+ T-lymphocytes than normal animals. Increased numbers of CD3+ T-lymphocytes, most of which were CD4+, and eosinophils were present in the skin of these animals following intradermal injection of a Culicoides antigen extract (97 +/- 21 vs. 449 +/- 49 CD3+ T-lymphocytes/mm2 in deep dermis of vehicle vs. antigen injected sites; 83 +/- 8% CD4+ T-lymphocytes at antigen injected site). T-lymphocytes, which are thought to be important in the pathogenesis of human allergic skin disease, may therefore contribute to the development of sweet itch lesions via the release of cytokines which can cause eosinophil accumulation and activation. An understanding of the pathology of this disease may lead to a more rational approach to therapy.

Alkaline Phosphatase↗
PubMed1998

Inhibition of antigen-induced cutaneous responses of ponies with insect hypersensitivity by the histamine-1 receptor antagonist chlorpheniramine.

A whole-body extract of Culicoides impunctatus induced a biphasic increase in oedema formation in ponies with insect hypersensitivity, with maxima after one and eight hours. The Culicoides antigen did not induce similar responses in ponies with no previous history of the disease. In insect-hypersensitive ponies the local administration of chlorpheniramine (12 micrograms) completely inhibited oedema formation in response to histamine (0.04 microgram) and to Culicoides antigen (0.5 microgram) at one hour, and the response to Culicoides antigen at eight hours was inhibited by 63 per cent. Chlorpheniramine also partially inhibited the accumulation of eosinophils and neutrophils induced by Culicoides antigen after two hours.

Animals↗
PubMed1998

Effect of the 5-lipoxygenase inhibitor, fenleuton, on antigen-induced neutrophil accumulation and lung function changes in horses with chronic obstructive pulmonary disease.

The leukotrienes (LT) LTD4 and LTB4 have been shown to cause bronchoconstriction and neutrophil accumulation, respectively, in horse lungs. Such changes are characteristic of the equine allergic respiratory disease, chronic obstructive pulmonary disease (COPD). To further investigate the role of these putative mediators in the pathogenesis of equine COPD the effect of a 5-lipoxygenase inhibitor, fenleuton, on antigen-induced changes in horses with this condition has been examined. Six horses with COPD underwent a series of four antigen challenges, one month apart, with placebo pre-treatment on three occasions and fenleuton (4 days oral dosing 5 mg/kg) pre-treatment on one occasion. Three horses received fenleuton prior to the second challenge and three horses received the drug prior to the fourth antigen challenge. Changes in radiolabelled neutrophil distribution, lung function and peripheral leucocyte counts were monitored on each occasion for 7 h following the start of antigen challenge. Antigen challenge caused an increase in radioactive counts over the lungs and a decrease in peripheral leucocyte count. Neither response was affected by fenleuton pre-treatment. Mean maximal changes in pleural pressure (delta Pplmax) and respiratory rate were also unaffected by fenleuton pre-treatment. However, in the two horses which responded to antigen-challenge with a particularly marked increase in delta Pplmax (> 15 cm H2O), prior administration of fenleuton reduced the response by 64 and 63%. These results suggest that 5-lipoxygenase inhibitors warrant further investigation as bronchodilators in equine COPD.

Animals↗
PubMed1998

Histamine-induced adherence and migration of equine eosinophils.

OBJECTIVES: To examine effects of histamine on equine eosinophil adherence in vitro and to determine the histamine receptor subtype(s) and cell surface adhesion molecules that mediate this response. In addition, to determine the receptor subtypes involved in histamine-induced eosinophil migration. ANIMALS: 8 healthy ponies. PROCEDURE: Effects of histamine on equine eosinophil adherence to serum- or fibronectin-coated plastic, and migration in a microchemotaxis assay were examined. In some experiments, eosinophils were pretreated with histamine receptor antagonists or monoclonal antibodies raised against cell adhesion molecules. For comparison, the effect of histamine on equine neutrophil adherence and migration was studied. RESULTS: Histamine induced adherence of equine eosinophils, but not neutrophils, to serum- and fibronectin-coated plastic (P < 0.01). Histamine also caused migration of equine eosinophils, but not neutrophils (P < 0.01). Histamine-induced adherence and migration of equine eosinophils were inhibited by histamine, (H,)-receptor antagonists chlorpheniramine and mepyramine (P < 0.01), but not H2- or H3-receptor antagonists cimetidine and thioperamide. Monoclonal antibodies raised against CD18, but not very late antigen 4, reduced histamine-induced equine eosinophil adherence to serum- and fibronectin-coated plastic (P < 0.01). CONCLUSIONS: When released from mast cells or basophils, histamine could stimulate adherence and migration of equine eosinophils via H, receptor activation and induce adherence of equine eosinophils to opsonized surfaces or dermal connective tissue matrix proteins via CD18 activation. CLINICAL RELEVANCE: Histamine may have a part in regulating equine eosinophil function during parasitic killing or antigen-induced responses in horses with insect hypersensitivity.

Animals↗
PubMed1997

Agonist-induced adherence of equine eosinophils to fibronectin.

Eosinophils are believed to play an important part in the pathogenesis of equine diseases such as helminth infestation and the allergic skin disease, sweet itch. It has been shown that adherence of human eosinophils to the connective tissue matrix protein fibronectin enhances cell activation and survival time. If adherence causes similar changes in the properties of equine eosinophils, cell-induced tissue damage at a site of parasitic infestation or allergic response would be exacerbated. However, investigation of this hypothesis requires identification of mediators that cause equine eosinophil adherence. Since the equivalent recombinant equine proteins were not available, the present study reports the effects of recombinant human (rh) C5a and IL-5 on the adherence of equine peripheral blood eosinophils (EPBEs) to fibronectin in vitro. The effects of LTB4 and PAF on EPBE adherence to fibronectin were also examined and phorbol myristate acetate (PMA) was used as a positive control. PMA caused a dose-related increase in EPBE adherence to fibronectin-coated plastic. In comparison, rh C5a produced a much smaller response which was only evident at the highest dose tested. On the other hand, rhIL-5 induced a small, but significant dose-related increase in EPBE adherence. Moreover, this response was in part dependent on the beta 1 integrin Very Late Antigen-4 (VLA4). Since adherence to serum-coated plastic was also increased by IL-5, beta 2 integrins may be activated and/or up-regulated on EPBEs by the cytokine. Neither LTB4 nor PAF caused EPBE adherence to fibronectin but prior incubation with these mediators increased the response of cells to IL-5. There were no differences between the responses of EPBEs isolated from horses with clinical signs of sweet itch and normal animals. Thus, whilst up-regulation of IL-5-induced adherence may occur locally in tissues in vivo, it does not appear to take place in the circulation. Finally, C5a, PAF and LTB4, but not IL-5, caused equine neutrophil adherence to fibronectin demonstrating the different responses of granulocytes to these mediators. The results obtained in the present study have shown that mediators which may be released at sites of inflammatory or allergic reactions can induce or enhance eosinophil adherence to tissue matrix protein. Thus, these mediators can now be used in future studies to determine if cell adherence may alter eosinophil activation or survival time.

Animals↗
PubMed1997

Differential superoxide anion generation by equine eosinophils and neutrophils.

Equine eosinophils and neutrophils are believed to play an important part in the protection of horses against parasitic and bacterial invasion. Eosinophils may also play a key role in the pathogenesis of equine inflammatory conditions such as the allergic skin disease, insect hypersensitivity. The factors which stimulate the respiratory burst of equine eosinophils and neutrophils are poorly understood. The first aim of the present study was to determine the effects of the phorbol ester, phorbol myristate acetate (PMA), which is believed to activate intracellular protein kinase C, and opsonised particles of serum-treated zymosan (STZ), on the production of superoxide anions by equine eosinophils and neutrophils. Since histamine has been detected after antigen challenge in the skin of horses with insect hypersensitivity, the second aim was to establish the effects of this mediator on superoxide anion production by equine eosinophils and the receptor sub-type(s) that mediate histamine-induced responses. For comparison, responses of neutrophils from the same horses were also examined. PMA and STZ induced significant increases in superoxide anion generation by equine eosinophils and neutrophils. The estimated maximum (EMAX) superoxide anion production by eosinophils in the presence of PMA was significantly greater than that of neutrophils; the estimated concentration of PMA inducing 50% of the maximum response (EC50) by eosinophils was significantly less. The EMAX values for superoxide anion production by neutrophils in the presence of STZ were significantly greater than those for eosinophils. Histamine induced superoxide anion generation by equine eosinophils which was inhibited by the histamine-1 receptor antagonists chlorpheniramine and mepyramine, but not the histamine-2 and histamine-3 receptor antagonists, cimetidine and thioperamide, respectively. Histamine did not cause superoxide anion production by equine neutrophils. These studies demonstrate that equine granulocytes vary in their ability to produce a respiratory burst in the presence of different stimuli, with eosinophils being more responsive to protein kinase C activators and neutrophils to opsonised particles. They also show that histamine selectively induced the generation of superoxide anions by equine eosinophils via histamine-1 receptor activation. Thus, in horses with insect hypersensitivity, histamine released from cutaneous mast cells after antigen challenge could activate eosinophils which have migrated into the dermis.

Animals↗
PubMed1997

Pharmacology of the 5-lipoxygenase inhibitors BAY Y 1015 and BAY X 1005 in the horse.

Calcium ionophore A23187 induced time and concentration dependent production of immunoreactive leukotriene (LT) B4 by equine heparinized whole blood in vitro. Time dependent production of immunoreactive LTB4 by equine neutrophils and immunoreactive LTC4 by equine eosinophils in vitro was also demonstrated. The 5-lipoxygenase activating protein (FLAP) inhibitors, BAY X 1005 and BAY Y 1015, produced concentration dependent inhibition of ionophore-induced LTB4 synthesis by equine whole blood (mean +/- SEM IC50s n = 5; 6.14 +/- 0.28 microM vs. 12.30 +/- 0.75 microM for BAY Y 1015 and BAY X 1005, respectively) and neutrophils (mean +/- SEM IC50s n = 5; 0.003 +/- 0.001 microM vs. 0.045 +/- 0.021 microM for BAY Y 1015 and BAY X 1005, respectively) and LTC4 synthesis by equine eosinophils (mean +/- SEM IC50s n = 5; 0.0036 +/- 0.0002 microM and 0.108 +/- 0.023 microM for BAY Y 1015 and BAY X 1005, respectively) in vitro. In all three assays, BAY Y 1015 was more potent than BAY X 1005, and for both compounds much higher concentrations were required to inhibit LT synthesis by whole blood compared to isolated neutrophils and eosinophils. Plasma concentration-time relationships and pharmacokinetic parameters for BAY Y 1015 administered intravenously and orally to six horses at a dosage of 10 mg/kg in a two period cross-over study were established. The study also evaluated the anti-inflammatory properties of BAY Y 1015 and its ability to inhibit ex vivo whole blood LTB4 synthesis and in vivo LTB4 synthesis in a tissue cage model of acute inflammation. At this dosage, BAY Y 1015 failed to significantly inhibit immunoreactive LTB4 synthesis or the oedema produced by intradermal injection of the mild irritant, carrageenan.

Administration, Oral↗
PubMed1997

Influence of antigen challenge on platelet responsiveness in horses with chronic obstructive pulmonary disease.

A role for platelets in allergic airways disease has been postulated and changes in the responsiveness of circulating platelets have been demonstrated following antigen challenge of asthmatic human subjects. In this study agonist-induced aggregation of equine platelets in vitro has been compared before and after exposure of horses to a controlled hay and stray challenge. Prior to challenge the response of platelets, from horses with chronic obstructive pulmonary disease (COPD) and normal animals, to adenosine diphosphate (ADP) and platelet activating factor (PAF) did not differ. Five hours after initiation of the challenge, there was a modest but significant decrease in the response of platelets from the COPD horses to PAF, but not to ADP. Platelets from normal horses were not less sensitive to either agonist at this time. Twenty four hours after challenge the responses of platelets from COPD horses to both agonists were the same as pre-challenge values. These results demonstrate that antigen challenge alters the responsiveness of platelets from allergic horses to PAF and this change is suggestive of PAF release accompanying allergen exposure in the horse.

Adenosine Diphosphate↗
PubMed1996

Effects of platelet activating factor on the distribution of radiolabelled leucocytes and platelets in normal horses and asymptomatic horses with chronic obstructive pulmonary disease.

Antigen challenge is known to cause the recruitment of neutrophils to the lungs of horses with chronic obstructive pulmonary disease (COPD). To evaluate a possible role of platelet activating factor (PAF) in this process, the effects of PAF on the distribution of radiolabelled neutrophils were compared in normal horses and asymptomatic horses with COPD. Changes in lung function, heart rate and the distribution of platelets and eosinophils were also measured. PAF (5 ng kg-1 intravenously) caused immediate but transient increases in the number of radiolabelled neutrophils in the lungs and a concomitant decrease in the peripheral neutrophil count. The total numbers of circulating leucocytes and neutrophils were also significantly decreased by PAF. Rapid and reversible increases in heart rate, respiratory rate and pleural pressure were also observed. In separate experiments, the numbers of radiolabelled eosinophils and platelets in the lungs increased transiently after the administration of PAF. The responses to PAF were qualitatively and quantitatively similar in normal horses and asymptomatic COPD horses. The PAF receptor antagonist WEB2086 (3 mg kg-1 intravenously) inhibited the effects of PAF. These results suggest that PAF, if released in the lungs of horses with COPD during an antigen challenge, might contribute to the recruitment of leucocytes and the respiratory changes.

Analysis of Variance↗
PubMed1996

Pharmacokinetics and pharmacodynamics of tolfenamic acid in calves.

Pharmacokinetic/pharmacodynamic modelling was applied to a study in which tolfenamic acid was administered intravenously to calves at a dose rate of 2 mg kg-1. The drug had a shorter mean (SEM) elimination half-life (T1/2 beta) of 2.5 (0.95) hours and a larger volume of distribution (Vdarea) of 0.98 (0.28) litre kg-1 than other non-steroidal anti-inflammatory drugs. Its body clearance was high with a mean value of 0.30 (0.06) litre kg-1 h-1. It had inhibitory effects on inflammatory exudate PGE2 and beta-glucuronidase, serum TxB2 and bradykinin-induced swelling but it did not affect exudate LTB4 concentrations. Its mean EC50 values were lower for exudate PGE2, beta-glucuronidase and bradykinin-induced swelling inhibition (0.077 [0.018]; 0.040 [0.017] and 0.030 [0.020] microgram ml-1, respectively) than for serum TxB2 inhibition (0.137 (0.079) microgram ml-1). There were also differences in its equilibration halflife, which was short for the inhibition of serum TxB2, intermediate for exudate PGE2 and beta-glucuronidase and longer for bradykinin-induced swelling. These differences may be explained by the existence of three distribution compartments relating to the different sites of action of the drug.

Animals↗
PubMed1996

A study of the effect of a platelet activating factor (PAF) receptor antagonist on antigen challenge of horses with chronic obstructive pulmonary disease.

Antigen challenge involving exposure to straw and mouldy hay for 7 h produced lung function changes and neutrophil recruitment to the lungs in horses with chronic obstructive pulmonary disease (COPD). During the challenge, an increase in radiolabelled neutrophils in the lungs occurred, together with increased respiratory rate and pleural pressure. The role of platelet activating factor (PAF) in antigen-induced neutrophil accumulation, and increased pleural pressure and respiratory rate was investigated by administering the PAF receptor antagonist WEB 2086 to asymptomatic COPD horses prior to antigen challenge. WEB 2086 (3 mg/kg i.v.) did not affect antigen-induced changes in either neutrophil accumulation or respiratory function. These results suggest that PAF may not be an important mediator of the response to antigen in equine COPD.

Analysis of Variance↗