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Abstract

Objective—To evaluate platelet surface-associated P-selectin, mean platelet component concentration (MPC), mean platelet component distribution width (MPCDW), mean platelet volume (MPV), and platelet distribution width (PDW) for detection of activated platelets in dogs with septic and nonseptic inflammatory disease.

Animals—20 healthy dogs and 20 dogs with septic and nonseptic inflammatory disease.

Procedures—Platelet surface-associated P-selectin (expressed as the median fluorescence intensity [MFI] of the platelet population), MPC, MPCDW, MPV, and PDW were determined in 20 healthy adult dogs, and reference ranges were calculated. These parameters were also determined in 11 dogs with nonseptic and 9 dogs with septic inflammatory disease and evaluated to determine which parameters were useful for detection of activated platelets.

Results—12 dogs with inflammatory disease had Pselectin greater than the upper limit of the reference range, whereas 16 dogs with inflammatory disease had MPC lower than the lower limit of the reference range. All dogs in which P-selectin was greater than the upper limit of the reference range had MPC lower than the lower limit of the reference range. The correlation coefficient for P-selectin and MPC was 0.62. Differences in the MPCDW, MPV, and PDW in most dogs with inflammatory disease (compared with healthy dogs) were found; however, the correlation coefficients for P-selectin and MPCDW, MPV, and PDW were low.

Conclusions and Clinical Relevance—Platelet surface- associated P-selectin and MPC appeared to be useful to detect activated platelets in most dogs with septic and nonseptic inflammatory disease. (Am J Vet Res 2005;66:325–329)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To investigate rheologic properties of bovine neutrophils that may result in adhesion molecule- independent sequestration of neutrophils in inflamed lungs of cattle.

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

Procedures—Neutrophil deformability, filamentous actin (F-actin) content, and CD11b expression was determined for unstimulated bovine neutrophils and bovine neutrophils incubated with the inflammatory mediators tumor necrosis factor-α (TNF), platelet-activating factor (PAF), interleukin-8 (IL-8), zymosan-activated plasma (ZAP), Pasteurella haemolytica-derived lipopolysaccharide (LPS), and P haemolytica leukotoxin. Neutrophils were separated into 3 subpopulations on the basis of size. The F-actin content and CD11b expression were evaluated by use of flow cytometry. Leukocyte deformability was evaluated by filtration of dilute whole blood.

Results—The subpopulation of the smallest-sized neutrophils (> 90% of neutrophils) contained little F-actin. A subpopulation of slightly larger neutrophils had a profound increase in F-actin content and CD11b expression. The subpopulation of the largest neutrophils had increased F-actin content and CD11b expression, compared with those for both subpopulations of smaller neutrophils. Incubation of neutrophils with PAF and ZAP, but not TNF, IL-8, LPS, or leukotoxin, resulted in decreased neutrophil deformability and increased F-actin content. Incubation with PAF and TNF induced an increase in size of neutrophils.

Conclusions and Clinical Relevance—Size can be used to identify subpopulations of large and rigid neutrophils in blood samples from healthy calves. Platelet-activating factor and activated complement fragments are potent inducers of F-actin formation and neutrophil rigidity. Physical changes in neutrophils may impede their transit through lung microvasculature and result in leukocyte trapping independent of adhesion molecule interactions with endothelial cells. (Am J Vet Res 2000;61:380–386)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether functional alterations in neutrophils and mononuclear leukocytes are a consistent finding in dogs with inflammatory disease.

Animals—40 healthy dogs, 30 dogs with nonseptic inflammatory diseases, 25 dogs with septic inflammation, and 8 dogs with multiple organ dysfunction syndrome (MODS) secondary to sepsis.

Procedure—Neutrophil size and granularity; expression of cell surface molecules including CD18, CD11b, and mature neutrophil antigen on neutrophils; and major histocompatability antigen class II (MHC class II) expression on monocytes and lymphocytes were evaluated by use of flow cytometry. Neutrophil size and granularity were evaluated by use of forwardangle versus side-angle light scatterplots. Leukocytes were labeled with monoclonal antibodies to quantify surface expression of leukocyte antigens.

Results—Dogs with septic and nonseptic inflammatory diseases and MODS had an increase in percentage of neutrophils with increased size; dogs with septic inflammation and MODS had a greater percentage of neutrophils with decreased granularity. Dogs with septic and nonseptic inflammation and MODS had a low expression of CD18 and mature neutrophil antigen. Dogs with septic and nonseptic inflammation had an increase in CD11b expression. Monocytes from dogs with septic and nonseptic inflammation and MODS had a low expression of CD18. Monocytes and lymphocytes from dogs with septic and nonseptic inflammation and MODS had a low expression of MHC class II.

Conclusions and Clinical Relevance—Neutrophils from dogs with septic and nonseptic inflammation circulate in an activated state, and some dogs have decreased MHC class II expression. Many dogs with MODS have a compensatory anti-inflammatory response that may compromise their responses to antimicrobials. ( Am J Vet Res 2004;65:59–63)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether platelets and neutrophils become activated in dogs during short-distance sled-pulling activity.

Animals—18 physically fit adult Siberian Huskies.

Procedure—Dogs were allocated into 2 teams (9 dogs/team). Each team ran a course of approximately 6.4 km while pulling a sled that contained 2 people. Blood samples were collected immediately before and within 10 minutes after completion of sled-pulling activity. Blood was aspirated into sterile syringes and immediately transferred to evacuated tubes containing EDTA solution. Platelet activation status was evaluated by determining cell-surface P-selection expression, number of platelet aggregates and platelet microparticles, mean platelet-component (MPC) concentration, and mean platelet-component distribution width (MPCDW) concentration. Neutrophil activation status was evaluated by determining cell-surface CD11/CD18 expression, neutrophil size, and neutrophil granularity.

Results—Short-duration strenuous sled-pulling activity was associated with lower MPC concentration, higher MPCDW concentration, and higher cell-surface P-selectin expression after activation with phorbol myristate acetate. An increase in neutrophil CD11/CD18 expression and a decrease in neutrophil granularity were also observed after exercise.

Conclusions and Clinical Relevance—Results of this study provide evidence of priming and activation of platelets and activation of neutrophils after strenuous short-duration sled-pulling activity. Additional studies will be needed to determine whether these changes have adverse effects on animal performance or induce tissue injury. (Am J Vet Res 2003;64:855–859)

Full 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