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Summary:

Retrospective review of CBC and serum chemical data from 124 horses admitted to the veterinary teaching hospital over a 9-month period (Feb 1, 1990 to Oct 31, 1990) indicated that 54 horses had echinocytosis (prevalence = 44%). In horses with echinocytosis, the most frequent diagnosis was colitis (23 horses; 43%). Odds ratios (measure of association) were calculated to determine the association of echinocytosis with specific hematologic and biochemical abnormalities. When evaluated in a multivariate model, low serum sodium concentration (< 136 mEq/L) was the only variable significantly associated with the incidence of echinocytosis. Within the group of 54 horses with echinocytosis, hyponatremia (35 horses; 65%), hypochloremia (35 horses; 65%), low total carbon dioxide concentration (35 horses; 65%), hypoosmolality (30 horses; 55%), and hypocalcemia (22 horses; 41%) were the most common biochemical abnormalities. It was concluded that hyponatremia was associated with increased incidence of echinocytosis. It was suggested that systemic electrolyte depletion might be involved in the induction of echinocyte formation.

Free access
in Journal of the American Veterinary Medical Association

Summary

The effects of furosemide and pentoxifylline on blood flow properties in horses were investigated. Hematologic and rheologic changes were examined in 4 horses before and 3 minutes after administration of epinephrine (1 mg, iv). The next day, hemorheologic changes were determined before and 3 hours after administration of furosemide (1 mg/kg of body weight, im), and after administration of epinephrine at the sampling at 3 hours. Hematologic and rheologic changes were evaluated weekly in 3 horses given pentoxifylline (8.5 mg/kg, q 12 h, po) for 28 days. In addition, hemorheologic responses to epinephrine were determined on days 0, 14, and 28 of pentoxifylline treatment. Neutrophil filtration studies were also performed 2 hours after iv administration of pentoxifylline (8.5 mg/kg).

Postepinephrine values for pcv, rbc and wbc counts, and blood viscosity were greater than preepinephrine values. Erythrocyte sedimentation rates decreased after epinephrine, whereas rbc filterability did not change. Treatment with furosemide was associated with increases in mean rbc hemoglobin concentration and blood viscosity. Filterability of rbc did not change. Treatment with pentoxifyllie resulted in an increase in rbc filterability and erythrocyte sedimentation rate and a decrease in pcv; however, mean values for hematocrit and rbc count did not change. Treatment with pentoxifylline did not result in a change in resting blood viscosity, but markedly reduced the postepinephrine increase in blood viscosity. Neither iv nor orally administered pentoxifylline had an effect on neutrophil filtration. It was concluded that pentoxifylline has beneficial effects on rbc filterability and postepinephrine changes in blood viscosity, which may contribute to improvements of microcirculatory blood flow. In addition, furosemide may exacerbate exercise-associated hyperviscosity in horses.

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the role of the nuclear factor-κB (NF-κB) in the response of bovine monocytes to exposure to Mycobacterium avium subsp paratuberculosis (MAP).

Sample Population—Monocytes from healthy adult Holstein cows that were known to be negative for MAP infection.

Procedures—Monocytes were incubated with MAP organisms with or without a specific inhibitor of the NF-κB pathway (pyrrolidine dithiocarbamate), and activation of the NF-κB pathway was detected by use of an electrophorectic mobility shift assay. The capacities of monocytes to express tumor necrosis factor (TNF)-α, interleukin (IL)-10, and IL-12; to acidify phagosomes; to phagocytize and kill MAP organisms; and to undergo apoptosis were evaluated.

Results—Addition of MAP organisms to monocytes activated the NF-κB pathway as indicated by increased NF-κB–DNA binding. Addition of pyrrolidine dithiocarbamate prevented nuclear translocation of NF-κB, decreased expression of TNF-α and IL-10, and increased IL-12 expression. Treatment of MAP-exposed monocytes with pyrrolidine dithiocarbamate increased the rate of apoptosis but failed to alter phagosome acidification, organism uptake, or organism killing by those cells.

Conclusions and Clinical Relevance—Results indicated that NF-κB rapidly translocated to the nucleus after exposure of bovine monocytes to MAP organisms. These data suggest that NF-κB is involved in initiation of inflammatory cytokine transcription and inhibition of apoptosis but that it is not directly involved in phagosome acidification or organism killing.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate activation of Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) pathway in bovine monocytes after incubation with Mycobacterium avium subsp paratuberculosis (Mptb) organisms.

Sample Population—Bovine monocytes obtained from 4 healthy adult Holstein dairy cows.

Procedures—Bovine monocytes were incubated with Mptb organisms with or without a specific inhibitor of the JNK/SAPK pathway (SP600125) for 2, 6, 24, or 72 hours. Expression of interleukin (IL)-1β, IL-10, IL-12, IL-18; transforming growth factor-β (TGF-β); and tumor necrosis factor-α (TNF-α) and the capacity of Mptb-infected monocytes to acidify phagosomes and kill Mptb organisms were evaluated. Phosphorylation status of JNK/SAPK was evaluated at 10, 30, and 60 minutes after Mptb incubation.

Results—Compared with uninfected control monocytes, Mptb-infected monocytes had increased expression of IL-10 at 2 and 6 hours after incubation and had increased expression of TNF-α, IL-1β, IL-18, and TGF-β at 2, 4, and 6 hours. Additionally, Mptb-infected monocytes had increased expression of IL-12 at 6 and 24 hours. Addition of SP600125 (specific chemical inhibitor of JNK/SAPK) resulted in a decrease in TNF-α expression at 2, 6, and 24 hours, compared with untreated Mptb-infected cells. Addition of SP600125 resulted in a decrease in TGF-β expression at 24 hours and an increase in IL-18 expression at 6 hours. Addition of SP600125 failed to alter phagosome acidification but did enhance the capacity of monocytes to kill Mptb organisms.

Conclusions and Clinical Relevance—Activation of JNK/SAPK may be an important mechanism used by Mptb to regulate cytokine expression in bovine monocytes for survival and to alter inflammatory and immune responses.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine cell membrane receptors involved in phagocytosis of Mycobacterium avium subsp paratuberculosis (MAP) organisms.

Sample Population—Monocytes were obtained from healthy adult Holstein dairy cows that were test negative for MAP infection on the basis of bacteriologic culture of feces and serologic test results.

Procedures—Monocytes or bovine macrophage cell line (BoMac) cells were incubated with MAP organisms for 30, 60, or 120 minutes with or without inhibitors of integrins, CD14, or mannose receptors. Phagocytosis was evaluated by light microscopy or by flow cytometry. CD11a/CD18, CD11b, and CD14 expression on monocytes and BoMac cells was evaluated by use of flow cytometry.

Results—Monocytes and BoMac cells rapidly phagocytized MAP organisms. However, compared with BoMac cells, monocytes had a greater total capacity to phagocytize MAP organisms. Addition of neutralizing anti-integrin antibodies (anti-CD11a/CD18 and anti-CD11b) substantially inhibited phagocytosis by monocytes during the first 60 minutes of incubation with MAP organisms, but were less effective at 120 minutes of incubation. Anti-CD11a/CD18 and anti-CD11b antibodies were less effective in inhibiting phagocytosis by BoMac cells. Addition of inhibitors of CD14 or mannose receptors also inhibited phagocytosis of MAP by monocytes. Addition of a combination of integrin and mannose inhibitors had an additive effect in reducing phagocytosis, but addition of integrin and CD14 inhibitors did not have an additive effect.

Conclusions and Clinical Relevance—Multiple receptors are involved in phagocytosis of MAP organisms. Although CD11/CD18 receptors appear to be the major receptors used by MAP at early time points, mannose receptors and CD14 also contribute substantially to phagocytosis.

Full access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate the role of the mitogen-activated protein kinase extracellular signal-regulated kinase (MAPKERK) pathway in the interaction between Mycobacterium avium subsp paratuberculosis (MAP) organisms and bovine monocytes.

Sample Population—Monocytes obtained from healthy adult Holstein dairy cows that were not infected with MAP organisms.

Procedures—Monocytes and MAP organisms were incubated together with or without a specific inhibitor of the MAPKERK pathway (PD98059), and the capacity of monocytes to express tumor necrosis factor alpha (TNF)-α and interleukin (IL)-10 and -12, produce nitric oxide, acidify phagosomes, kill MAP organisms, and undergo apoptosis was evaluated.

Results—The MAPKERK pathway was activated within 10 minutes after addition of MAP organisms to monocytes. Addition of PD98059 to monocyte-MAP mixtures decreased monocyte TNF-α and IL-12 mRNA expression but had no effect on IL-10 mRNA expression. Treatment with PD98059 failed to induce significant alterations in phagosome acidification, organism killing, nitric oxide production, or apoptosis of MAP-exposed monocytes.

Conclusions and Clinical Relevance—Results indicated that the MAPKERK pathway was activated during the interaction of MAP organisms with monocytes, which initiated TNF-α and IL-12 mRNA expression but failed to initiate antimicrobial activity. The MAPKERK pathway may be involved in initiating proinflammatory and proimmune responses in MAP infection in cattle.

Full access
in American Journal of Veterinary Research

Abstract

Objectives—To evaluate the role of interleukin (IL)-10 in the inability of monocyte-derived bovine macrophages to kill Mycobacterium avium subsp paratuberculosis organisms in vitro.

Sample Population—Monocytes were obtained from healthy adult Holstein dairy cows that had negative results when tested for infection with M avium subsp paratuberculosis.

Procedure—Monocyte-derived macrophages were incubated with M avium subsp paratuberculosisfor 2, 6, 24, 72, or 96 hours with or without addition of saturating concentrations of a goat anti-human IL-10 that has been documented to neutralize bovine IL-10 activity. Variables assessed included ingestion and killing of M avium subsp paratuberculosis; expression of tumor necrosis factor (TNF)-α, IL-12, IL-8, major histocompatability (MHC) class II, vacuolar H+ ATPase, and B cell CLL/lymphoma 2 (BCL-2); production of nitric oxide; acidification of phagosomes; and apoptosis of macrophages.

Results—Neutralization of IL-10 enabled macrophages to kill 57% of M avium subsp paratuberculosis organisms within 96 hours. It also resulted in an increase in expression of TNF-α, IL-12, IL-8, MHC class II, and vacuolar H+ ATPase; decrease in expression of BCL-2; increase in acidification of phagosomes; apoptosis of macrophages; and production of nitric oxide.

Conclusions and Clinical Relevance—The capacity of M avium subsp paratuberculosis to induce IL-10 expression may be a major determinant of virulence for this organism. (Am J Vet Res 2005;66:721–726)

Full access
in American Journal of Veterinary Research

Abstract

Objectives—To study the in vitro effects of cecal contents incubated with corn starch on colonic permeability in horses.

Animals—4 healthy adult ponies.

Procedure—Mucosal specimens were obtained from the right ventral colon and mounted in Ussing chambers. Changes in short circuit current, conductance, and large-molecule permeability in response to addition of cecal contents and cecal contents incubated with corn starch were evaluated for 120 minutes.

Results—Incubation of cecal contents with corn starch for 8 hours resulted in a decrease in cecal content pH and an increase in lactic acid concentration. These changes were similar to those reported in vivo for ponies given corn starch. Exposure of colonic mucosa to cecal contents incubated with corn starch resulted in an increase in tissue conductance and permeability of technetium Tc 99m pentetate, compared with mucosa exposed to cecal contents alone.

Conclusions and Clinical Relevance—In vitro exposure of colonic mucosa to cecal contents incubated with starch resulted in increased paracellular permeability. Fermentation of excessive amounts of carbohydrate in the intestinal lumen of horses may directly induce increased intestinal permeability associated with carbohydrate-induced laminitis. (Am J Vet Res 2000;61:858–861)

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