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recognized that the OA disease process typically starts with disease of the synovial membrane itself and is driven primarily by macrophages. 2 These synovial tissue macrophages appear to exist in a hybrid state of activation that overall displays regulatory

Open access
in Journal of the American Veterinary Medical Association

Chicken macrophages are the most potent antigen-presenting cells capable of resistance to exogenous pathogenic microorganisms. 1–6 Macrophages differentiate via classic or alternative pathways into 2 functional types: M1 or M2. 7 Activated

Full access
in American Journal of Veterinary Research

developing effective therapies for enhanced intrasynovial tendon healing. Circulating monocytes and macrophages that become localized within the tendon after following injury persist throughout the inflammatory, proliferative, and remodeling stages of

Open access
in American Journal of Veterinary Research

document the inflammatory potential of the microbiome of obese horses, compared with nonobese horses. Our hypothesis was that murine macrophages exposed to fecal extract from obese horses would exhibit increased inflammatory capacity in vitro, compared with

Full access
in American Journal of Veterinary Research

Summary

The type of plasminogen activator (pa) produced by bovine milk macrophages has been determined. Macrophages produce a pa protein with molecular weight of 28,000 and isoelectric point of 8.5, and with enzymatic activity independent of fibrin. These characteristics are identical to those reported for bovine urokinase-pa. Although blood monocytes and milk macrophages produce pa after stimulation with lipopolysaccharide, mammary macrophages are clearly limited in their ability to release pa. At maximal stimulation, 78% of the pa produced by milk macrophages remained cell-associated. In marked contrast, blood monocytes released 76% of the pa produced into the culture medium. Macrophages isolated from mastitic quarters produced higher (2.5 times) amounts of pa, compared with those produced by macrophages isolated from healthy quarters. However, in both cases, macrophages were unable to secrete the protein already produced. The limited pa secretion by milk macrophages might be a residual function of a differentiated macrophage population.

Free access
in American Journal of Veterinary Research

Summary

Seven horses (4 anesthetized and 3 awake) and 2 ponies (anesthetized) were studied to evaluate the high sensitivity of the pulmonary circulation of the horse to various blood-borne particles, and to establish the presence of intravascular macrophages in the lung. Pulmonary and systemic pressures and cardiac output before and during particle injection were measured in some animals. An anesthetized foal had a large increase in pulmonary arterial pressure (32 and 34 mm of Hg) within 1 minute of IV administration of small test doses of radioactively labeled liposomes (2.5 μmol/kg of body weight) or a 1% suspension of blue pigment (0.3 ml/kg), respectively. Quantitative real-time gamma camera imaging of the foal revealed high retention of the labeled liposomes during the first pass through the lungs; retention persisted throughout the experiment. Postmortem analysis revealed 55 and 47% lung retention of liposomes and blue pigment, respectively. The 2 anesthetized ponies had increased pulmonary artery pressure of 34 ± 7 mm of Hg, decreased cardiac output, and 42% lung retention after administration of 1% blue pigment (0.2 ml/kg), whereas 3 awake horses had increased pressure of 28 ± 9 mm of Hg after 1.8 × 108 (1.8-μm-diameter) latex microspheres/kg. None of the injected particles caused vascular obstruction, and they do not cause pulmonary vascular reactivity in species that lack pulmonary intravascular macrophages. Finally, 3 horses (1 anesthetized and 2 awake) were infused Iv with small doses of the blue pigment, and their lungs were perfusion-fixed to identify specific labeling of the pulmonary intravascular macrophages. These cells were fully differentiated macrophages, contained blue pigment in phagocytes, and were tightly adherent to the pulmonary capillary endothelium. At this time, horses (order Perissodactyla) are the only species outside the mammalian order Artiodactyla (sheep, pig, cattle) documented to have reactive intravascular macrophages. Compared with other species, low doses of particles induced marked hemodynamic responses; horses appear to be more sensitive to IV administered particles than are other species studied.

Free access
in American Journal of Veterinary Research

SUMMARY

The relative sensitivity of bovine blood monocytes and macrophages isolated from milk to lipopolysaccharide, with respect to interleukin 1 (il-1) production, was evaluated. Addition of lipopolysaccharide (0 to 30 μg/ml) to the culture medium resulted in increases in secreted and intracellular il-1 activity for monocytes and milk macrophages, with maximal stimulation achieved at 30 μg of lipopolysaccharide/ ml of medium. At this concentration of lipopolysaccharide, monocytes released 76% of the total il-1, whereas milk macrophages released only 26% of the total il-1 produced within the cell. Secretion of a small quantity of il-1 was a common property of macrophages isolated from healthy and mastitic quarters. We concluded that limited secretion of il-1 may render the milk macrophages less efficient in promoting lymphocyte activation.

Free access
in American Journal of Veterinary Research

SUMMARY

In a search of viral agents in pulmonary macrophages of horses with chronic pulmonary disease, equine herpesvirus 2 was found to be unique. In 8 of 9 horses with chronic pulmonary disease, antigens of equine herpesvirus 2 were detected by indirect immunofluorescence staining of scattered foamy macrophages immediately after harvesting by bronchoalveolar lavage and fractionation on metrizamide gradients. In a healthy horse, antigens were not found. After 1 week of cultivation of bronchoalveolar lavage cells from a second group of 9 horses with chronic pulmonary disease, viral antigens were detected in 90% of the adherent pulmonary macrophages. In 2 of 3 healthy horses, viral antigens also were found in 90% of the adherent pulmonary macrophages. Antigens of equine herpesvirus 1, equine herpesvirus 4, parainfluenza virus 3, or adenovirus were not detected. Antigens of the 5 investigated viruses also were not detected in lung tissue slices from a third group of 14 horses: 4 healthy; 7 with varying degrees of bronchiolitis, 2 of which also had chronic intestitial pneumonia; 2 with eosinophilic bronchitis; and 1 with pulmonary hemorrhage.

The exclusive presence of equine herpesvirus 2 in pulmonary macrophages was confirmed qualitatively by isolation of infective virus by cocultivation. In a fourth group of 12 horses with chronic pulmonary disease, infective virus could be isolated from pulmonary macrophages of 3 horses and from mixed- blood leukocytes of 5 horses. Virus isolations from 2 healthy horses were not successful from pulmonary macrophages, whereas 1 isolation was obtained from mixed-blood leukocytes. Other viruses were not detected by cocultivation.

Free access
in American Journal of Veterinary Research

SUMMARY

Avian peritoneal exudate macrophages, when exposed to phagocytic stimuli, produced an appreciable oxidative burst as measured by production of chemiluminescence, superoxide anion, and hydrogen peroxide. Metabolic inhibitors of the oxidative burst and scavengers of oxygen radicals clearly inhibited macrophage chemiluminescence, but had no significant effect on macrophage bactericidal activity against Escherichia coli or fungistatic activity against Candida tropicalis. Therefore, avian macrophages were capable ofox ygen-independent bactericidal and fungistatic activities.

Free access
in American Journal of Veterinary Research

SUMMARY

The chemotactic activity of turkey peritoneal macrophages in response to an atherosclerotic plaque extract from a hypertensive strain of turkeys was determined. Atherosclerotic plaque extract stimulated macrophage chemotaxis, whereas normal aortic extract did not stimulate macrophage chemotaxis. However, differences were not revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of extracts of atherosclerotic plaque and normal aorta. Chemotactic activity was diminished with pronase treatment, suggesting the chemoattractant is a protein. Seemingly, atherosclerotic plaque of turkeys contains a macrophage chemotaxin.

Free access
in American Journal of Veterinary Research