L-lactic acid and D,L-lactic acid infusion in ponies resulted in metabolic acidosis with high anion gap (AG). Increased AG was explained entirely by increased blood L- and D-lactate concentrations. Hydrochloric acid infusion caused metabolic acidosis with decreased AG. Saline (NaCl) infusion caused mild metabolic acidosis, with no significant change in AG. Plasma K+ concentration was decreased by all types of infusions, with a maximum of 0.50, 0.25, 0.40, 0.50 mmol/L below baseline at the end of infusion in the L-lactic acid-, D,L-lactic acid-, HCl-, and NaCl-infused ponies, respectively. Only hydrochloric acid had a tendency to increase plasma K+ concentration. Hypophosphatemia developed in NaCl- and HCl-infused ponies, but not in the D,L-lactic acid-infused ponies. Serum inorganic phosphate concentration in L-lactic acid-infused ponies increased initially, but was significantly (P < 0.05) lower than values in the other ponies at 4 hours after onset of infusion. In ponies, the effect of acidemia on plasma K+ and serum inorganic phosphate concentrations was similar to that reported for other species. Changes were small in magnitude and depended on the nature of the acid anion. Results indicate that large changes in plasma K+ and serum inorganic phosphate concentrations during acidosis are probably not a direct result of acidemia.

We defined methods for use of luminol-dependent chemiluminescence (LDCL) and superoxide anion (O2-) production as parameters of the oxidative metabolism of neutrophils isolated from 1.5- to 5-week-old neonatal calves. We determined how variations in blood sample handling, agonist preparation, individual variability, and age of calves influenced the LDCL and O2- responses to certain agonists, and defined concentrations of soluble and particulate agonists that maximally stimulated the oxidative metabolism of bovine neutrophils. Oxidative responses, particularly LDCL, were characterized by marked dayto-day variability, differed greatly within and between calves, were partially age-dependent, and were partially dependent on the individual agonist. Superoxide anion production had substantially less variability. We compared the in vitro oxidative (LDCL and O2-) responses of neutrophils isolated from neonatal calves stimulated by defined concentrations of the agonists-latex, phorbol myristate acetate, calcium ionophore, and opsonized zymosan-with responses to formylated oligopeptides and zymosan-activated serum, and to live, dead, live opsonized, and dead opsonized Pasteurella haemolytica organisms. Opsonization of particulates, pathogenic or nonpathogenic, enhanced the LDCL and O2- responses of stimulated neutrophils although P haemolytica was a less potent stimulant of oxidative functions than were nonbiological agonists. We conclude that the generation of reactive oxygen species by bovine neutrophils in response to P haemolytica is highly dependent on the presence of opsonins and is greatly enhanced in live vs killed bacteria. Futhermore, the in vitro generation of reactive oxygen species, including O2- by stimulated neutrophils, may be of biologic importance if similar events occur in vivo, and could have a major role in the pathogenesis of the acute lung injury associated with pneumonic pasteurellosis.

Opsonized Rhodococcus equi activated the respiratory burst of resident alveolar macrophages (AM) from adult horses in a logarithmic-linear, mass-related manner. The effect of R equi was not significantly different from that of equal masses of opsonized zymosan A. Therefore, R equi does not appear to attenuate the respiratory burst of equine AM. The stimulatory effect of R equi was not reflected by increased production of superoxide anion (O2-), but increased activity of the hexose monophosphate shunt was observed. These results suggest a similarity between the respiratory burst of Am from horses and that of AM from rabbits. We concluded that resident AM from adult horses do not produce O2- concurrently with an increase in activity of the hexose monophosphate shunt when stimulated with either opsonized zymosan A or opsonized R equi. This suggests that O2- is not an important component of the antibacterial defenses of equine AM. Whether equine AM are incapable of producing O2- or require different stimuli to produce it was not determined.

L-lactic acid and D,L-lactic acid infusion in ponies resulted in metabolic acidosis with high anion gap (AG). Increased AG was explained entirely by increased blood L- and D-lactate concentrations. Hydrochloric acid infusion caused metabolic acidosis with decreased AG. Saline (NaCl) infusion caused mild metabolic acidosis, with no significant change in AG. Plasma K+ concentration was decreased by all types of infusions, with a maximum of 0.50, 0.25, 0.40, 0.50 mmol/L below baseline at the end of infusion in the L-lactic acid-, D,L-lactic acid-, HCl-, and NaCl-infused ponies, respectively. Only hydrochloric acid had a tendency to increase plasma K+ concentration. Hypophosphatemia developed in NaCl- and HCl-infused ponies, but not in the D,L-lactic acid-infused ponies. Serum inorganic phosphate concentration in L-lactic acid-infused ponies increased initially, but was significantly (P < 0.05) lower than values in the other ponies at 4 hours after onset of infusion. In ponies, the effect of acidemia on plasma K+ and serum inorganic phosphate concentrations was similar to that reported for other species. Changes were small in magnitude and depended on the nature of the acid anion. Results indicate that large changes in plasma K+ and serum inorganic phosphate concentrations during acidosis are probably not a direct result of acidemia.

Previous studies demonstrated that the polyanion dextran sulfate (DS) protects rat coronary and porcine aortic endothelium (PAE) from oxygen-derived free radical (OFR) injury due to hydrogen peroxide (H2O2) or xanthine/xanthine oxidase (X/XO). To determine if DS has a similar protective effect in bovine aortic endothelium (BAE) and bovine brain microvascular endothelium (BBME), H2O2 or X/XO was added to confluent cultures. Cell injury was assessed 1 d later by measuring the percentage of viable cells (by trypan blue exclusion) and the release of lactate dehydrogenase (LDH) into the medium. After H2O2 doses of 6.0 mM for BAE and BBME and 0.8 mM for PAE, and after X doses of 10 μM and XO doses of 0.3 U/mL for all cell types, approximately 50% of cells were viable. Cultures were pretreated with DS (0.001 to 500 μg/mL) 24 to 26 h prior to H2O2 or X/XO exposure. Pretreatment at concentrations of 0.5, 5, and 50 μg/mL significantly increased the percentage of viable cells and reduced LDH release in cultures of PAE, but not BAE or BBME, treated with H2O2. Similarly, pretreatment with DS concentrations of 5 and 50 μg/mL significantly increased the percentage of viable cells and reduced LDH release in cultures of PAE, but not BAE or BBME, treated with X/XO. Thus, DS protected porcine but not bovine endothelium. Catalase (10 U/mL) increased the percentage of viable cells and reduced LDH release in H2O2-treated BAE and BBME, suggesting that DS likely acts by a different mechanism and does not neutralize H2O2. These results suggest that the protective effect of DS on OFR-injured endothelium is species-dependent.

Arterial blood samples were collected from 19 anesthetized pigs before and after hemorrhage was induced. Blood gas tensions and concentrations of sodium, potassium, chloride, lactate, and total protein were measured. Results indicated that hydrogen ion (H+) concentration calculated from a specific formula was a biased and imprecise estimate of measured H+ concentration. The bias was 5.45 nEq/L, with limits of agreement from -7.92 to 18.83 nEq/L. Because albumin is the fraction of plasma protein most important in acid-base balance, the agreement between predicted and measured H+ concentration was reevaluated, using an albumin charge estimate and a reference swine albumin-to-globulin ratio. This improved the ability of the formula to predict H+ concentration; the bias decreased to 1.33 nEq/L with limits of agreement from -12.16 to 9.49 nEq/L. The formula and a simplified approach for clinical application were biased and unacceptably imprecise estimators of lactate (L-) concentration. The formula approach underestimated L- concentration by 2.8 (-12.4, 6.7) mEq/L, whereas the simplified method overestimated L- concentration by 5.0 (-3.8, 13.9) mEq/L.

Acidemia stimulates renal ammonia production and excretion. This adaptive response allows increased H+ secretion and generation of new bicarbonate. To determine whether a relationship existed between urine ammonium (NH4+) concentration and excretion and urine anion gap (Na+ + K+ - Cl-), ammonium chloride (NH4Cl) was administered per OS for 5 days to induce systemic acidemia in 12 healthy Beagles. During NH4Cl administration, a strong, statistically significant (P < 0.0001) relationship was apparent between urine NH4+ concentration measured in millimoles per liter and urine anion gap. Regression equation: urine [NH4+] = 8.2 - 0.416 X urine anion gap; r = -0.897. A statistically significant (P = 0.0001) relationship existed between urine NH4+ excretion measured in millimoles per kilogram of body weight per day and urine anion gap. Regression equation: urine NH4+ excretion = 0.74 - 0.38 X urine anion gap; r = -0.768. As urine NH4+ concentration or excretion increased, urine anion gap became more negative. Before NH4Cl administration (no systemic acidemia), a weak, but statistically significant (P = 0.015) relationship was observed between urine NH4+ concentration and urine anion gap. Regression equation: urine [NH4+] = 65.2 - 0.141 X urine anion gap; r = -0.41. However, a relationship was not evident between urine NH4+ excretion and urine anion gap before NH4Cl administration. Hence, urine anion gap is a reliable index of urine NH4+ concentration and excretion only in dogs with metabolic acidosis. In human beings with distal renal tubular acidosis, NH4+ excretion is inappropriately low and results in a positive urine anion gap. Therefore, as a reliable index of NH4+ excretion, urine anion gap may represent an easy and rapid method to aid in the diagnosis of distal renal tubular acidosis in dogs.

Oxidative respiratory burst activity was examined in lavage-procured bovine pulmonary alveolar macrophages. Nonstimulated alveolar macrophages released a minimal quantity of superoxide anion and had small amounts of glucose flux through the pathways of energy metabolism. Nonstimulated cells metabolized substantial amounts of glucose through the hexose monophosphate shunt. Stimulation with opsonized zymosan particles induced a tonfold increase in the release of superoxide anion and a twofold increase in the flux of glucose through the hexose monophosphate shunt and the pathways of energy metabolism. Preliminary observations also indicated that the magnitude of the burst varied between sets of bronchoalveolar cells obtained from the same calf over time.

In our previous study, it was demonstrated that the administration of anion salts, which slightly lower the dietary cation-anion difference (DCAD), in the prepartum period is safe and effective for preventing milk fever in multiparous cows. In the present study, several clinico-pathological constituents in serum and urine, which might be related to milk fever, were analyzed using stored samples from the previous study to identify clinico-pathological parameters for easily evaluating the efficacy of lowering DCAD and to further investigate the mechanism by which lowering DCAD prevents milk fever. Among the parameters analyzed in the present study, inorganic phosphorus (iP) was involved in milk fever because the serum concentration and urinary excretion of iP were significantly higher in the group of primiparous cows (heifer group), which did not develop hypocalcemia, than those in other groups of multiparous cows. Serum chloride concentrations in the heifer group and the group of multiparous cows fed anion salts (anion group) tended to remain higher than those in other control groups of multiparous cows suggesting that serum chloride concentration may be utilized for evaluating the status of metabolic acidosis and the efficacy of lowerng DCAD in dairy cows fed anion salts. In addition, plasma estradiol-17beta concentration in the heifer group tended to be lower at parturition compared with that in other multiparous groups suggesting that estrogen known as a potent inhibitor of bone resorption may be involved in developing milk fever.

An R664X nonsense mutant AE1 is responsible for dominant hereditary spherocytosis in cattle and is degraded by the proteasomal endoplasmic reticulum-associated degradation. The present study demonstrated that R664X AE1 translated in vitro had the trypsin-sensitve site identical to that of the wild-type AE1. The P661S/R664X mutant containing a possible N-glycosylation site at Asnsup(660) showed an increase in size by 3 kDa both in the cell-free translation system and in transfected HEK293 cells. Moreover, steady state levels of R664X and P661S/R664X in HEK293 cells were markedly increased in the presence of a proteasome inhibitior. These findings indicate that the truncated C-terminal region of R664X AE1 has lumenal localization in the endoplasmic reticulum and is not accessible to proteasomal machineries in the cytosol.