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  • Author or Editor: José Fagliari x
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Abstract

Objective—To determine the capacity of inflammatory mediators tumor necrosis factor-α (TNF-α), interleukin- 8 (IL-8), platelet-activating factor (PAF), lipopolysaccharide (LPS), and leukotoxin to prime, activate, or alter deformability of adult bovine neutrophils.

Sample Population—Blood collected from 5 healthy adult Holstein cows.

Procedure—Isolated neutrophils or whole blood was incubated with TNF-α, IL-8, PAF, LPS, or leukotoxin, and neutrophil chemiluminescence, degranulation, deformability, shape change, CD11b expression, and size distribution was measured.

Results—Incubation with TNF-α, IL-8, PAF, and LPS primed neutrophils for oxygen radical release but caused minimal oxygen radical release by themselves. None of the inflammatory mediators induced degranulation. Incubation with TNF-α and PAF resulted in a decrease in neutrophil deformability and induced shape change in neutrophils. Incubation with PAF consistently resulted in an increase in neutrophil size as measured by use of flow cytometry. Only IL-8 caused an increase in expression of CD11b by neutrophils.

Conclusions and Clinical Relevance—Inflammatory mediators tested had minimal effects on neutrophil oxygen radical production or degranulation but did prime neutrophils for oxygen radical production. Incubation with PAF and TNF-α caused a decrease in neutrophil deformability and altered neutrophil shape and size. Results of our study indicate that PAF- and TNF-α-induced changes in neutrophil deformability and size may cause integrin- and selectin-independent trapping of neutrophils in the lungs of cattle with pneumonic pasteurellosis. ( Am J Vet Res 2000;61: 492–498)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether platelet-activating factor (PAF) is involved in acute lung microvascular injury associated with pneumonic pasteurellosis in calves.

Animals—15 healthy 2- to 4-week-old male Holstein calves.

Procedure—Calves were anesthetized and inoculated intrabronchially with saline (0.9% NaCl) solution (n = 5) or 1 × 109 Pasteurella haemolytica organisms (n = 10). Of the 10 calves inoculated with P haemolytica, 5 also were treated with WEB 2086, a potent inhibitor of PAF, and 5 were treated with vehicle. Blood and bronchoalveolar lavage samples were collected before and 1, 2, 4, and 6 hours after inoculation of P haemolytica. Blood samples were analyzed to evaluate total number and differential counts of leukocytes, dilute whole-blood leukocyte deformability, size of neutrophils, and neutrophil CD11b expression. Bronchoalveolar lavage samples were analyzed for total number and differential counts of nucleated cells, total protein concentration, and hemoglobin concentration. Size and gross and histologic appearance of lung lesions also was determined.

Results—Treatment of calves with WEB 2086 reduced size of lung lesions, attenuated the increase in microvascular permeability, and reduced neutrophil infiltration in the first 4 hours after inoculation. Treatment with WEB 2086 also attenuated a decrease in leukocyte deformability, increase in size of neutrophils, and CD11b expression by circulating neutrophils.

Conclusions and Clinical Relevance—It appears that PAF is a major mediator for altered lung microvascular permeability and activation of circulating neutrophils in the first 4 hours after onset of pneumonic pasteurellosis in calves. (Am J Vet Res 2000;61: 248–254)

Full access
in American Journal of Veterinary Research

Abstract

Objectives

To determine the structural and functional alterations in circulating neutrophils that may lead to sequestration in lung microvasculature and endothelial injury in calves with experimentally induced pneumonic pasteurellosis.

Animals

10 healthy, 2- to 4-week-old male Holstein calves.

Procedures

Holstein calves were anesthetized and inoculated intrabronchially with Dulbecco phosphate buffered saline (0.9% NaCl) solution (DPBSS; 5 control calves) or 1 × 109 Pasteurella haemolytica organisms (5 infected calves). Blood samples were collected before and 1, 2, 4, and 6 hours after inoculation. Total and differential WBC count, dilute whole blood leukocyte deformability, neutrophil size distribution, and neutrophil surface CD11b expression were measured in blood samples.

Results

A progressive decrease in leukocyte deformability and increase in neutrophil size was detected 1, 2, 4, and 6 hours after inoculation of P haemolytica. Neutrophil surface CD11b expression was greater than baseline values at 6 hours after inoculation of P haemolytica. Two populations of neutrophils with an increase in size were detected in P haemolytica-infected calves. Both subpopulations had increased CD11b expression, compared with neutrophils that were typical in size.

Conclusions and Clinical Relevance

Neutrophils circulate in an activated and nondeformable state in calves with experimentally induced pneumonic pasteurellosis. A decrease in neutrophil deformability and neutrophil aggregation may contribute to neutrophil trapping in the lung microvasculature during pneumonic pasteurellosis in calves. (Am J Vet Res 1999;60:1307–1311)

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To determine whether platelets become activated and form platelet-neutrophil aggregates during near-maximal treadmill exercise in horses.

Animals

4 Thoroughbreds.

Procedure

Horses were subjected to 4 standardized exercise tests on a treadmill, and blood samples were collected before exercise, at treadmill speed of 12 m/s, and 5 minutes after exercise. Flow cytometric techniques were used to identify activated platelets, and flow cytometric and microscopic techniques were used to identify platelet-neutrophil aggregates.

Results

Platelet-neutrophil aggregates increased from 2.8 ± 0.4% at rest to 17.2 ± 1.1% and 14.7 ± 1.6% during and after exercise, respectively. Platelet activation was not detected during or after exercise.

Conclusions

Platelet-neutrophil aggregates consistently form during strenuous exercise in horses. (Am J Vet Res 1998;59:393–396)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine whether plasma protein concentrations were altered in ponies with alimentary laminitis.

Animals

12 adult ponies.

Procedure

Acute laminitis was induced in 6 ponies by oral administration of carbohydrate (85% corn starch, 15% wood flour); the other 6 ponies were used as controls. A physical examination was performed and blood samples were collected immediately before and 4, 8, 12, 24, and 28 hours after administration of carbohydrate. Plasma protein concentrations were determined by means of sodium dodecyl sulphate-polyacrylamide gel electrophoresis.

Results

19 plasma proteins ranging from a molecular weight of 24,000 to a molecular weight of 350,000 were identified in all 12 ponies. Plasma concentrations of proteins with molecular weights of 350,000 (fibrinogen), 130,000 (ceruloplasmin), 118,000 (c-reactive protein), 67,000 (α1-antitrypsin I), 65,000 (α1-antitrypsin II), 50,000 (haptoglobulin), and 45,000 (acid glycoprotein) were significantly increased in ponies with laminitis, compared with concentrations in control ponies.

Conclusion

Changes in plasma protein concentrations are detectable within 4 hours after the onset of alimentary laminitis in ponies.

Clinical Relevance

Measurement of plasma protein concentrations may be useful in monitoring the progression of laminitis in ponies. (Am J Vet Res 1998;59:1234–1237)

Free access
in American Journal of Veterinary Research

Abstract

Objectives

To determine whether platelets become activated and form platelet-platelet or platelet-neutrophil aggregates, or both, when subjected to shear.

Sample Population

Blood obtained from 3 Thoroughbreds.

Procedures

Blood, with PCV adjusted to 32 (low hematocrit) or 60 (high hematocrit)%, was subjected to shear rates of 11.25, 22.5, 45, 90, 225, and 750/s for 3 minutes by use of a cone-plate viscometer. Flow cytometric techniques were used to identify activated platelets, platelet-platelet aggregates, and platelet-neutrophil aggregates.

Results

Shear resulted in decreased platelet count, increased mean platelet volume, platelet activation, and formation of platelet-platelet and platelet-neutrophil aggregates. These changes occurred at lower shear rates in blood with high hematocrit. Platelet-neutrophil aggregate formation was inhibited by blocking P-selectin, but not CD11/CD18 receptors.

Conclusions

Shear-induced platelet activation and aggregate formation occur at physiologic shear rates.

Clinical Relevance

Shear-induced platelet activation may explain the exercise-associated platelet-neutrophil aggregates observed in Thoroughbreds undergoing treadmill exercise. (Am J Vet Res 1998;59:1243-1246)

Free access
in American Journal of Veterinary Research

SUMMARY

Objectives

To determine whether platelets are hyperaggregable or form platelet-neutrophil aggregates during the prodromal stages of acute laminitis of ponies.

Animals

Healthy adult ponies: 8 experimental and 6 control.

Procedures

Acute laminitis was induced by oral administration of corn starch and wood flour to 8 ponies, and indices of platelet activation were evaluated. Blood samples were collected before and at 4, 8, 12, 24, 28, and 32 hours after carbohydrate administration, and PCV, total plasma protein concentration, platelet count, activated clotting time, whole blood recalcification time, spontaneous platelet aggregation, ex vivo platelet aggregation responses, and platelet-neutrophil aggregates were determined. When lameness was first detected, ponies were euthanatized and arteriography and histologic examination of hooves were performed.

Results

Carbohydrate overload was associated with hyperaggregability of platelets throughout the prodromal stages of laminitis and increased numbers of platelet-neutrophil aggregates. Reduction of blood supply to affected hooves was variable, and blood clots were found in 6 of 11 laminitis-affected hooves.

Conclusions

Platelets were hyperaggregable throughout the prodromal stages of carbohydrate-induced laminitis and formed platelet-neutrophil aggregates. Platelet-neutrophil aggregates may initiate or contribute to development of acute laminitis.

Clinical Relevance

Anti-platelet therapy may be useful for treatment of acute alimentary laminitis in horses. (Am J Vet Res 1997;58:1376–1380)

Free access
in American Journal of Veterinary Research

SUMMARY

Objectives

To determining whether inhibition of platelet aggregation prevents development of carbohydrate overload-induced alimentary laminitis.

Animals

22 healthy adult ponies.

Procedures

Acute laminitis was induced by oral administration of corn starch/wood flour to 16 ponies, 8 of which were treated with a synthetic analogue of the platelet fibrinogen receptor antagonist peptide (RPR) RGDS (arginine-glycine-aspartic acid-serine) 110885; 6 ponies served as negative controls. Blood was collected before and at 4, 8, 12, 24, 28, and 32 hours after administration of carbohydrate overload, and PCV, total plasma protein concentration, platelet count, activated clotting time, whole blood recalcification time, spontaneous platelet aggregation, ex vivo platelet aggregation responses, in vivo platelet activation, and platelet-neutrophil aggregates were evaluated.

Results

Of 16 ponies given carbohydrate, 6 of 8 untreated ponies developed laminitis and 0 of 8 ponies treated with RPR 110885 developed laminitis. The RPR 110885 treatment attenuated the increase in platelet-neutrophil aggregates observed in untreated ponies.

Conclusions

Platelets are involved in the pathogenesis of equine alimentary laminitis.

Clinical Relevance

Platelet aggregation inhibitors may be useful for prevention or treatment of laminitis, or both. (Am J Vet Res 1998;59:814–817)

Free access
in American Journal of Veterinary Research