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Biomedical subjects

A D Sedgwick

Publications and source records attributed to A D Sedgwick.

At least 37 records · Page 2Linked to original sources
PubMed1987

Cellular aspects of inflammation. The Ciba-Geigy Prize for Research in Animal Health.

The migration of leucocytes to sites of acute and chronic inflammation is an event of central importance to the maintenance of inflammatory processes; extravascular leucocytes are responsible for generating chemical mediators of inflammation and the phagocytosis of particulate matter. They may also be involved in the conversion of acute to chronic inflammatory lesions. Leucocytes are attracted to sites of tissue injury by a range of chemoattractants. This paper describes the development of a method for separating on Percoll gradients purified populations of equine polymorphonuclear and mononuclear leucocytes and use of the isolated cells in vitro studies. Two independent assay methods, the agarose microdroplet and the Boyden chamber microfilter techniques, were used. The assays were utilised in three ways: (a) to investigate the sensitivity of polymorphonuclear and mononuclear leucocytes to two standard chemoattractants, zymosan activated plasma and n-formyl-methionyl-leucyl phenylalanine; (b) to study the chemoattractant properties of leukotriene B4 and prostaglandin E2 for equine leucocytes; and (c) to investigate the inhibitory actions of several nonsteroidal anti-inflammatory drugs (NSAIDs) on equine leucocyte movement.

Acute Disease↗
PubMed1987

Modulation of lymphocyte activating factor activity (interleukin 1 like activity) and acute phase proteins in pertussis-induced air pouch inflammation by muramyl dipeptide.

We have studied the effect of the macrophage activator, muramyl dipeptide (MDP) on immune inflammation induced in the rat six day subcutaneous air pouch. Treated animals received either 100 micrograms or 200 micrograms MDP at the time of challenge and twenty four hours before exudate harvest. Using the thymocyte co-mitogenic assay for lymphocyte activating factor (LAF), 100 micrograms MDP enhanced LAF activity whereas 200 micrograms caused inhibition. Increased dilution of 200 micrograms exudate in this assay removed this inhibition. Similarly, at the lower dose, MDP caused enhanced production of the acute phase protein alpha 1 glycoprotein, whereas the higher dose had no effect. The present study suggests that macrophage activity can be manipulated in vivo to produce LAF and naturally occurring inhibitors of LAF. These studies indicate that the stimulation of LAF inhibitors by MDP may be a potential therapeutic action.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1987

Actions of BW540C in an equine model of acute inflammation: a preliminary study.

An equine model of acute non-immune inflammation has been developed to facilitate studies of the inflammatory process and the actions of novel anti-inflammatory drugs. Five polyester sponge strips soaked in sterile 2% carrageenin solution were placed in subcutaneous pouches prepared under local anaesthesia in the necks of conscious ponies. Serial removal of the strips and harvesting of the exudate enabled studies to be made of the cellular, biochemical and mediator aspects of the localised, acute inflammation, and the heat generated by the lesion was monitored by infra-red thermometry. Maximal concentrations of the eicosanoids 6-keto-prostaglandin F1 alpha, thromboxane B2 and leukotriene B4 occurred at 9 h, whereas leukocyte numbers, lactate dehydrogenase (LDH) and total protein concentrations were greatest at 24 h. Lesional skin temperature was increased by approximately 4 degrees C throughout the 24 h period. The novel anti-inflammatory agent BW540C, administered orally at a dose-rate of 20 mg/kg, did not affect leukocyte infiltration or the concentrations of protein, LDH and eicosanoids in exudate but serum thromboxane B2 levels were reduced. Skin temperature rises were greater in drug-treated animals. It is concluded that higher doses of BW540C will be required for a clinically useful anti-inflammatory action in horses.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Actions of non-steroidal anti-inflammatory drugs on equine leucocyte movement in vitro.

The direct effects of four non-steroidal anti-inflammatory drugs (NSAIDs) on equine polymorphonuclear (PMN) and mononuclear (MN) leucocyte movement were investigated using two in vitro assay systems. The Boyden chamber microfilter technique measures both chemokinetic and chemotactic locomotion, and the agarose microdroplet assay measures solely chemokinesis. Zymosan-activated plasma (ZAP) and the synthetic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) were used as standard chemoattractants for PMN and MN leucocytes, respectively. The actions of six concentrations of each NSAID, indomethacin (50 microM-10 mM), phenylbutazone (10 microM-1 mM), oxyphenbutazone (2.5 microM-500 microM) and flunixin (0.1 microM-50 microM), in suppressing cell movement induced by ZAP and FMLP were investigated. All four drugs exerted inhibitory effects on induced movement of both cell types in the Boyden chamber assay, usually in a concentration-dependent manner, although oxyphenbutazone action on PMN cells occurred only at the highest concentration tested. Significant inhibition of PMN and MN cell locomotion was produced by indomethacin, flunixin and oxyphenbutazone, and inhibition of PMN movement by phenylbutazone occurred in the agarose microdroplet assay. Flunixin was the most potent of the four drugs investigated in both assay systems. The findings may be of importance to the use of phenylbutazone and flunixin as NSAIDs in equine medicine, since the concentrations used were similar to concentrations of both drugs and the phenylbutazone metabolite oxyphenbutazone previously reported to occur in equine plasma and inflammatory exudate.

Animals↗
PubMed1987

Use of a novel non-steroidal anti-inflammatory drug in the horse.

In a two-part cross-over experiment in six ponies, an acute inflammatory reaction was generated by injecting carrageenin solution into subcutaneously-implanted tissue-cages lined with fibrovascular granulation tissue. In each part of the cross-over, half of the ponies received a novel phenylpyrazoline anti-inflammatory agent (BW540C) orally and half received a placebo treatment. BW540C inhibited platelet cyclo-oxygenase for 24 h but the reductions in exudate eicosanoid concentrations were less pronounced. A significant suppression in the rise of surface skin temperature in BW540C-treated ponies paralleled drug-induced inhibition of thromboxane B2 bicyclic prostaglandin (PG) E2 concentrations at the inflamed site. The drug had no significant effect on 6-keto-PGF1 alpha, migrating leucocytes, lactate dehydrogenase or total protein in exudates. Maximum plasma concentrations of both compounds occurred 2 to 4 h after dosing and maximum exudate levels of drug and metabolite occurred at 12 h. Both compounds penetrated approximately three times less readily into exudate than into plasma.

Animals↗
PubMed1987

The activation of carrageenan air pouch inflammation by silica and its effects on cartilage degradation.

We have examined the effects of carrageenan inflammation activated by silica particles on implanted femoral-head cartilage. The injection of silica particles modifies the inflammatory response, inducing a prolonged polymorphonuclear leucocyte infiltration and low exudate volume. This modification in the inflammatory response resulted in an accelerated loss of proteoglycan by the implanted femoral heads. Examination of exudate interleukin 1 (IL-1) concentrations directly by a lymphocyte-activating assay and indirectly by measuring the acute-phase response indicated that the increased loss was not due to increased levels of IL-1. High levels of lactate dehydrogenase would suggest that the increase cartilage breakdown is due to dying polymorphonuclear leucocytes releasing their intracellular enzymes. It is concluded that injection of silica together with carrageenan produces a pathological environment similar to that seen in human septic arthritis.

Animals↗
PubMed1987

Influence of chemotactic agents on the locomotion of equine polymorphonuclear and mononuclear leucocytes.

Subpopulations of equine leucocytes, polymorphonuclear and mononuclear cells, were separated from whole blood on a discontinuous Percoll gradient and used in studies of chemokinesis and chemotaxis. Polymorphonuclear cells responded to the chemo-attractant properties of zymosan-activated plasma in Boyden chamber and agarose microdroplet assays but they responded only slightly (Boyden chamber) or not at all (agarose microdroplet) to the peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP). Equine mononuclear cell movement was increased by FMLP in both assay systems and these cells also responded to zymosan activated plasma in the Boyden chamber assay but not in the agarose microdroplet. It is concluded that factors controlling equine polymorphonuclear and mononuclear cell movements into inflammatory exudates may differ.

Animals↗
PubMed1986

Studies of eicosanoid production in the air pouch model of synovial inflammation.

The time course of the inflammatory reaction in the rat air pouch model of synovial inflammation has been investigated at different stages of development of the lining structure using immune (pertussis vaccine) and non-immune (carrageenan) irritants. Exudate volumes and leucocyte numbers were greater with carrageenan than with pertussis vaccine but with both irritants much greater reactions were obtained when the irritant was injected at a time when the air pouch architecture most closely resembled synovium (i.e. 6 days). The time course of fluid accumulation following carrageenan in 6 day pouches was not interrupted when exudate was aspirated from the pouch six days after carrageenan injection. In the 6 day old air pouch PGE2 and 6-oxo-PGF1 alpha concentration peaked at 6 hours and 24 hours respectively. With carrageenan and pertussis vaccine stimulation, LTB4 concentrations were maximal at 3-6 hours with both irritants and low concentrations were still present at 13 days. The presence of a lining structure was found to influence concentrations of PGE2 in the air pouch. Pre-treatment with colchicine or 5-fluorouracil to reduce cell accumulation was not found to effect the modified PGE2 response. Our findings suggest that the presence of a synovial like lining structure may induce changes in composition in respect to cellular content and in putative mediator concentrations. We conclude that it is important in elucidating the mechanisms involved in arthritic inflammation to study injury in a cavity lined by macrophages and fibroblasts.

6-Ketoprostaglandin F1 alpha↗
PubMed1986

A comparison of air pouch, sponge and pleurisy models of acute carrageenan inflammation in the rat.

A comparative assessment of the time course of changes in three models of acute carrageenan-induced inflammation, the six-day air pouch, polyester sponge and pleurisy models, was obtained by measuring exudate volume, leucocyte numbers, PGE2 concentrations and lactate dehydrogenase activity at 2, 6 and 24 h. The greatest increases in exudate volume, leucocyte numbers and PGE2 concentration and the smallest rise in protein occurred in the air pouch model. Increases in lactate dehydrogenase were greatest in the sponge and least in the pleural exudate, indicating that the least cell damage occurred in the pleurisy model. PGE2 was not detectable in most pleural exudate samples. The actions of two steroids, betamethasone and dexamethasome, at two dose levels, 80 and 160 micrograms/kg, were assessed in each model. Overall, the six-day air pouch was found to be most satisfactory and most sensitive for assessing the actions of the steroids. The sponge model was either less sensitive or gave inconsistent responses, for the variables measured, than the cavity models of inflammation. Since the six-day air pouch has previously been shown to resemble synovium, our findings indicate that it is likely to be superior to the other two models as a model of joint inflammation.

Acute Disease↗
PubMed1986

Single step purification procedure for the rapid separation of equine leucocytes.

Percoll gradients have been used to separate relatively pure populations of viable equine polymorphonuclear (PMN) and mononuclear (MN) cells. In preliminary studies, a continuous density gradient of 70% Percoll solution was used to separate two distinct leucocyte-rich bands. After measurement of the density of each band on the continuous gradient, discontinuous Percoll gradients, using 60% and 75% Percoll solutions, were used to provide a rapid means of separating PMN and MN cells. The yield of viable cells per ml of blood was 3.0 X 10(6) and 3.2 X 10(6) for MN and PMN cells, respectively. Corresponding values for recovery were 45% and 72%. The purity was 94% for PMNs and 99% for MNs.

Animals↗
PubMed1986

Mast cells in newly formed lining tissue during acute inflammation: a six day air pouch model in the mouse.

Connective tissue mast cells were topographically and quantitatively studied in the newly formed lining tissue of six day old air pouches induced in the dorsal surface of mice. The results showed that the number of mast cells in the cavities innermost lining increased after injection of carrageenan into the cavity. Degranulation of mast cells was also observed. Variations in mast cell numbers in the lining seemed to correlate with the histamine content. These findings suggest that mast cells not only participate in the initiation of the early phase of acute inflammation but also appear to play an important part in regulating and prolonging more chronic inflammatory reactions.

Acute Disease↗
PubMed1986

Susceptibility of cartilage to damage by immunological inflammation.

Injection of ovalbumin into subcutaneous air pouches prepared on the backs of rats previously sensitised to the antigen resulted in the induction of a small and transient accumulation of inflammatory fluid with a predominantly polymorph cell infiltrate. Challenge of pouches of appropriately sensitised rats with Bordetella pertussis vaccine, on the other hand, resulted in a larger and more prolonged accumulation of fluid and cells with a predominantly mononuclear presence. When intact homologous femoral head cartilage was implanted in these inflamed pouches proteoglycan loss was found to be not different from similar implants in non-inflamed pouches. Coating the cartilage with human heat-aggregated immunoglobulin G prior to implantation in air pouches was also found to be without effect on subsequent proteoglycan loss.

Animals↗
PubMed1986

The effect of anti-inflammatory and rheumatoid disease modifying drugs on prolonged immune and non-immune inflammation in the six-day air pouch of rats.

The six-day air pouch model of synovitis in rats was used to study the effects of non-steroidal and anti-rheumatic drugs on cell accumulation and exudate formation. Inflammation was induced in the six-day air pouch either with the non-immune irritant carrageenan or the immune irritant Bordetella pertussis. Indomethacin reduced cell accumulation and exudate formation in both models. In contrast levamisole and D-penicillamine were unable to reduce either parameter, D-penicillamine actually producing at certain times a pro-inflammatory effect. The steroid dexamethasone caused the total inhibition of inflammatory exudate formation and cell accumulation. The six-day air pouch of rats may therefore be useful for the detection of agents which inhibit chronic inflammation.

Animals↗
PubMed1986

The use of the air pouch to study experimental synovitis and cartilage breakdown.

This mini-review outlines the development and application of the air pouch model during the past five years. It shows the importance of using the appropriate aged pouch to establish long-lasting chronic inflammation following immune and non-immune stimuli. Subsequently, the effects of different inflammatory environments were studied on implanted cartilage. It has been found that the inflammation used to date did not lead to an appreciable increase in the rate of cartilage degradation. This is discussed with the implications for new trends in therapeutic research applied to rheumatology.

Air↗
PubMed1986

Degradation of cartilage in contact with soft tissue.

Observations have been made on histological changes in femoral-head articular cartilage transplanted into soft tissue in rats under a variety of conditions. Articular cartilage was implanted either whole or minced. Implants were made into deflated subcutaneous air pouches with or without an inflammatory irritant and into normal subcutaneous tissue. Cartilage-matrix loss occurred in four patterns: marginal zone encroachment, loss of metachromatic staining without loss of tissue mass, surface invasion and lacunar enlargement and coalescence. The presence of an inflammatory reaction had no discernible effect on loss of cartilage matrix. Changes at the marginal zone preceded changes at the centre. Loss of metachromatic staining without loss of tissue mass occurred in areas of chondrocyte death. Surface invasion was not affected by the viability of the underlying chondrocytes. Surface invasion occurred earliest in cartilage transplanted into subcutaneous tissue, and latest in cartilage implanted into air pouches inflamed with carrageenan. The onset of surface invasion appeared to be dependent on soft-tissue adhesion to the cartilage surface. Mincing of cartilage was associated with an increase in surface invasion in the deeper cartilage zone with large lacunae but not in the superficial zone with small lacunae. Occasional cut surfaces showed outgrowth of new cartilage matrix. These observations on artefactual modes of cartilage degradation may assist in analysing the critical steps in cartilage degradation in arthritic joints.

Air↗
PubMed1986

Studies on the effects of non-steroidal and disease modifying agents on cartilage soft tissue interaction in vivo.

The present study reports the effects of certain non-steroidal anti-inflammatory (NSAID) and rheumatoid-disease-modifying drugs on a novel animal model of cartilage degradation in vivo. Air pouches were induced on the dorsal surface of rats, and femoral-head cartilage was implanted. The proteoglycan content of the implanted cartilage was then used to assess cartilage degradation. Indomethacin, D-penicillamine, levamisole and dexamethasone all have some cartilage-protective activity. These observations are discussed.

Animals↗