Loline and ergot alkaloids found in endophyte-infected (Acremonium coenophialum) tall fescue (EITF) cause vasoconstriction of equine vessels in vitro. An aggregate risk study was used to evaluate the association between horses exposed to EITF and development of laminitis. Veterinary teaching hospitals participating in the Veterinary Medical Data Base were grouped by whether equine accessions were likely to have been at high, moderate, or low risk for exposure to EITF. From 1980-1990, there were 185,781 accessions, of which 5,536 had diagnosis of laminitis. Proportion of equine accessions with laminitis reported by veterinary teaching hospitals for high, moderate, and low risks, were 3.41, 3.04, and 2.00 cases/100 accessions, respectively (P < 0.0001). Comparison of the proportion of accessions with laminitis in the high- and moderate-risk groups with that in the low-risk group revealed significant differences between risk groups over all months (P = 0.063) and differences from month to month within risk groups (P = 0.0001). If the difference among risk groups is attributed entirely to exposure to EITF, the population-attributable risk is 7 cases/1,000 admissions, or 15% of all admissions for laminitis at veterinary teaching hospitals in our data base. Preliminary data support an association between hoses exposed to EITF and increased risk of laminitis; however, studies at the individual animal level are indicated to confirm this hypothesis.

We evaluated the single-cycle structural properties for axial compression, torsion, and 4-point bending with a central load applied to the caudal or lateral surface of a diaphyseal segment from the normal adult equine humerus, radius, third metacarpal bone, femur, tibia, and third metatarsal bone. Stiffness values were determined from load-deformation curves for each bone and test mode. Compressive stiffness ranged from a low of 2,690 N/mm for the humerus to a high of 5,670 N/mm for the femur. Torsional stiffness ranged from 558 N.m/rad for the third metacarpal bone to 2,080 N.m/rad for the femur. Nondestructive 4-point bending stiffness ranged from 3,540 N.m/rad for the radius to 11,500 N.m/rad for the third metatarsal bone. For the humerus, radius, and tibia, there was no significant difference in stiffness between having the central load applied to the caudal or lateral surface. For the third metacarpal and metatarsal bones, stiffness was significantly (P < 0.05) greater with the central load applied to the lateral surface than the palmar or plantar surface. For the femur, bones were significantly (P < 0.05) stiffer with the central load applied to the caudal surface than the lateral surface. Four-point bending to failure load-deformation curves had a bilinear pattern in some instances, consisting of a linear region at lower bending moments that corresponded to stiffness values from the nondestructive tests and a second linear region at higher bending moments that had greater stiffness values. Stiffness values from the second linear region ranged from 4,420 N.m/rad for the humerus to 13,000 N.m/rad for the third metatarsal bone. Differences in stiffness between nondestructive tests and the second linear region of destructive tests were significant (P < 0.05) for the radius, third metacarpal bone, and third metatarsal bone. Difference between stiffness values of paired left and right bones was not detected for any test. Four-point bending ultimate failure bending moments ranged from 260 N.m for the femur to 940 N.m for the third metatarsal bone. There was no difference in failure bending moment between the directions of applied central load for a given bone.

In 33 healthy dogs, 66 bronchoalveolar lavage samples from the right and left caudal lung lobes were analyzed for volume of return, cellularity, differential cellularity, and immunophenotypic lymphocyte subpopulations. Lavage return was 64.8% (mean) following 3 sequential 25-ml lavages, for a total lavage volume of 75 ml. With this technique, 21.1 X 10(6) cells/sample (mean) were obtained. The cellular components of bronchoalveolar lavage samples, in decreasing order of frequency, were alveolar macrophages (79.4%), lymphocytes (13.5%), eosinophils (3.6%), mast cells (2.1%), epithelial cells (0.8%), and neutrophils (0.6%). Mean alveolar lymphocyte subpopulation frequencies, determined in 18 samples, for pan T, CD4, and CD8 cells were 52, 21.9, and 17.8%, respectively, with a CD4/CD8 ratio of 1.3. Variables analyzed did not vary between right and left caudal lung lobes, nor were they affected by body weight.

Ultrasonographic cross-sectional area (CSA) measurements of equine superficial digital flexor (SDF) tendon were obtained to determine the feasibility of ultrasonography for CSA measurement of tendon in vivo and in vitro. Ultrasonographic measurements were compared with a more traditional CSA measurement method, ink-blot analysis. In addition, values for ultrasonographic SDF tendon mean echogenicity were obtained in vivo and in vitro. The left forelimb SDF tendons of 23 horses were evaluated ultrasonographically. Cross-sectional images were acquired at 4-cm intervals distal to the base of the accessory carpal bone (DACB) to the level of the proximal sesamoid bones while horses were standing squarely. After euthanasia, the left forelimbs were mounted in a materials testing system (MTS) and loaded under tension to standing load. Ultrasonographic images were again acquired at the same locations. The ultrasonographic images were digitized, and values for ultrasonographic CSA and mean echogenicity were obtained for each level. Immediately after mechanical testing, a 1-cm-thick transverse section of SDF tendon at 12 cm DACB was removed. Three ink blots were prepared from each end of the removed tendon section and digitized. The 6 CSA values were averaged to generate a value for morphologic CSA for each SDF tendon at 12 cm DACB. Standing ultrasonographic tendon CSA at 12 cm DACB was consistently smallest (mean +/- SD CSA = 86 +/- 11 mm2), followed by MTS ultrasonographic CSA (mean, 95 +/- 12 mm2), with ink-blot morphologic CSA being largest (mean, 99 +/- 15 mm2). Comparison of standing and MTS ultrasonographic values at 12 cm DACB revealed a strong positive linear correlation between methods (R2 = 0.74, P = 0.001). Comparison of ink-blot CSA at 12 cm DACB with standing and MTS ultrasonographic CSA revealed strong positive linear correlations (R2 = 0.64, P = 0.001 and R2 = 0.72, P = 0.001, respectively). For ultrasonographic mean echogenicity, standing values insignificantly exceeded MTS values at each level. The authors conclude that ultrasonography is a useful technique for the noninvasive assessment of SDF tendon CSA that can be applied in vivo and in vitro.

Starling forces and hemodynamics in the digits of 5 horses were studied during early laminitis induced by oral administration of an aqueous extract of black walnut (Juglans nigra). The black walnut extract was prepared from heartwood shavings and was administered by nasogastric tube. Heart and respiratory rates, rectal temperature, central venous and arterial pressures, digital pulses, and signs of lameness were monitored. Blood samples were collected for determination of WBC count, hemoglobin concentration, and PCV and for endotoxin and tumor necrosis factor assays. Total WBC count and central venous pressure were monitored until they decreased by 30 or 20%, respectively. These decreases in WBC count and central venous pressure were observed 2 to 3 hours after dosing with black walnut extract. Respiratory and heart rates, body temperature, systolic and diastolic blood pressures, PCV, and hemoglobin concentration did not change significantly. Anesthesia was induced, heparin (500 IU/kg of body weight) was administered IV, and a pump-perfused extracorporeal digital preparation was established. Digital arterial and venous pressures were maintained at 100 and 30 mm of Hg, respectively. Blood flow, capillary pressure, lymph and plasma protein concentrations, and weight of the isolated digit during rapid increase in venous pressure were measured. Isogravimetric capillary filtration coefficient, vascular compliance, vascular and tissue oncotic pressures, tissue pressure, osmotic reflection coefficient, and precapillary and postcapillary resistances were calculated. Mean digital blood flow was 14 ml/min/100 g, capillary pressure was 52 mm of Hg, and vascular compliance was 0.06 ml/mm of Hg. The vascular and tissue oncotic pressures were 21.49 and 4.93 mm of Hg, respectively. The osmotic reflection coefficient was 0.71, and tissue pressure was 41 mm of Hg. The precapillary and postcapillary resistances were 7 and 2 mm of Hg/ml, respectively. Capillary permeability to proteins was not significantly different from that previously measured in healthy horses, suggesting that the increased capillary filtration coefficient reflected increased capillary hydrostatic pressure and perfusion of previously nonperfused capillaries. Neither endotoxin nor serum tumor necrosis factor activity was detected in any samples. The hemodynamic and Starling forces observed in this study were similar to those observed after laminitis was induced by administration of a carbohydrate gruel. Significant differences between the 2 models were detected for total vascular resistance, postcapillary resistance, and capillary filtration coefficient. It is likely that these differences were identified because the horses administered the black walnut extract were at an earlier stage in the disease process. The findings of this study suggest that the increase in capillary pressure causes transvascular fluid movement, resulting in increased tissue pressure and edema. We hypothesize that further increases in tissue pressure may collapse capillary beds and lead to tissue ischemia.

Objective--To study whether end products of 2 pathways of anaerobic energy metabolism, lactate and purines, that accumulate in the blood after intense exercise indicate any relation to exercise performance. Design--Venous blood samples were taken within 1 and 15 minutes after a trotting race of 2,100 m. Animals--16 Clinically healthy Standardbred trotters. Procedure--Blood and plasma lactate concentrations were measured by enzymatic analyzer, and purines, uric acid and allantoin, were determined by high-performance liquid chromatography. The concentrations of metabolites were then correlated to racing time and individual performance indexes that are annually calculated from the percentage of winnings, placings, and starts rejected, average earnings per start, and the racing record. Results--Blood lactate concentration immediately and calculated cell lactate concentration immediately and 15 minutes after the race correlated positively (P < 0.05 to P < 0.01) with the individual performance indexes. Plasma lactate concentration was not correlated to the individual performance indexes. Uric acid concentration, immediately and 15 minutes after the race, was negatively correlated (P < 0.05) to the individual performance indexes, and a positive relation (P < 0.05) was found between the highest concentration of uric acid and the racing time. Concentration of allantoin immediately or 15 minutes after the race did not have any significant correlation to the individual performance indexes. Conclusions--Accumulation of lactate in the blood, which was greater in the superior performing horses, may prove to be an useful predictor of anaerobic capacity. The results also indicate that the loss of purine nucleotides was less in the superior performing horses, although further studies are needed to confirm this.

We performed a study to determine a reference range for serum alpha 1-antitrypsin (alpha 1 AT) in dogs by specific immunoassay; to evaluate whether serum alpha 1 AT concentration varied with age, sex, or reproductive status in healthy dogs; and to investigate whether the serum alpha 1 AT concentration in hospitalized dogs differed from that of healthy, nonhospitalized dogs. Serum alpha 1 AT was quantitated by radial gel immunodiffusion for 60 healthy dogs and 311 hospitalized dogs. In healthy dogs, serum alpha 1 AT concentration was 2.33 +/- 0.41 mg/ml (mean +/- SD), yielding a reference range (mean +/- 2 SD) of 1.51 to 3.15 mg/ml. A correlation was not found between serum alpha 1 AT concentration and age in healthy dogs. The serum alpha 1 AT concentration (mean +/- SEM mg/ml) was significantly higher in healthy, sexually intact females (2.64 +/- 0.1) than in healthy, spayed females (2.22 +/- 0.12; P < 0.004); healthy, sexually intact males (2.14 +/- 0.1; P < 0.0006); and healthy, castrated males (2.25 +/- 0.14; P < 0.02). Hospitalized, sexually intact females had a lower serum alpha 1 AT concentration (1.93 +/- 0.07) than healthy, sexually intact females (2.64 +/- 0.1; P < 0.0002). Likewise, the serum alpha 1 AT concentration in hospitalized, sexually intact males (1.92 +/- 0.04) was less than in healthy, sexually intact males (2.14 +/- 0.1; P < 0.04). A difference in alpha 1 AT concentration was not found between healthy and hospitalized, neutered dogs.

Fifty serum samples from dogs with clinical signs of hypothyroidism and autoantibodies (AA) to thyroglobulin (Tg), thyroxine, or triiodothyronine were screened for AA to thyroid peroxidase (TPO). Thyroid peroxidase is the antigen against which microsomal AA are formed in human beings with lymphocytic thyroiditis. The TPO was isolated from canine thyroid tissue, using a modification of the procedure for purifying porcine TPO. The enzyme was solubilized from the membrane, using a deoxycholate-trypsin solution, followed by ammonium sulfate precipitation and diethylaminoethyl Sephadex chromatography. Activity of TPO was determined, using an iodide oxidation assay and a guaiacol assay. A monoclonal antibody to canine Tg, coupled to an immunoaffinity column, was used to eliminate the contaminating Tg from the TPO preparation. Using the TPO preparation as an antigen, an ELISA was performed on 10 serum samples and immunoblot assays were performed on 50 canine sera. Autoantibodies to TPO were not found in any of the sera. Assays also were performed, using purified porcine and human TPO and evidence of cross-reactivity with canine TPO was not identified. The absence of AA to TPO in dogs suggests a different pathogenesis for autoimmune thyroid disease in dogs than that hypothesized for lymphocytic thyroiditis in human beings.

The percentage of limb contact time spent in braking and propulsion was determined for the forelimbs and hind limbs of Greyhounds at 2 walk speeds and 3 trot speeds. Limb contact times decreased significantly (P < 0.05) as velocity increased between each velocity range. At a slow walk (0.92 to 1.03 m/s), braking and propulsion were 56.1 and 43.6% of contact time in the forelimbs and 41.6 and 58.1% of contact time in the hind limbs, respectively. At a fast walk (1.06 to 1.17 m/s), braking and propulsion were 56.7 and 43.5% of contact time in the forelimbs and 41.5 and 58.4% of contact time in the hind limbs, respectively. There was no significant difference in the percentage of contact time that the forelimbs and hind limbs spent in braking and propulsion between the 2 walk velocities. At the slow trot (1.5 to 1.8 m/s), braking and propulsion were 56.8 and 43% of contact time in the forelimbs and 30.1 and 67.6% of contact time in the hind limbs, respectively. At the medium trot (2.1 to 2.4 m/s), braking and propulsion were 55.9 and 43.5% of contact time in the forelimbs and 33.8 and 63.2% of contact time in the hind limbs, respectively. At the fast trot (2.7 to 3.0 m/s), braking and propulsion were 57.2 and 43% of contact time in the forelimbs and 37.5 and 61.1% of contact time in the hind limbs, respectively. Braking percentage increased and propulsive percentage decreased significantly (P < 0.05) in the hind limbs between the slow and fast trot speeds. There was no significant difference in the percentage of forelimb contact time spent in braking and propulsion between the walk and the trot gaits or among the 3 trot velocities.

Plasma and milk concentrations of parathyroid hormone-related protein (PTHrP) at various stages of pregnancy and lactation were determined in thirty-nine 3- to 16-vear-old Brown Swiss and Red Holstein X Simmental dairy cows originating from 4 herds. Eighteen of the cows were separated into 2 groups: low-parity (LP, n = 8) cows if they were in their first or second pregnancy and high-parity (HP, n = 10) cows if they were in their third or greater pregnancy. Blood samples were collected from each cow on 1 occasion, 15 to 5 days before calving, and blood and milk samples were collected daily during 6 days after calving. Serum total and ionized calcium (Catot and Ca2+, respectively) and milk Catot concentrations were also quantified. A transient postpartum decrease of serum Catot and Ca2+ concentrations was observed, whereas milk Catot concentration was constant. Plasma concentration of PTHrP was detected in 11 of 21 cows by use of an immunoradiometric assay (range, 0.45 to 1.82 pmol/L). Daily mean (+/- SD) colostrum and milk PTHrP concentrations ranged from 3.25 (+/- 3.23) to 4.69 (+/- 1.36) nmol/L in LP cows and 2.74 (+/- 0.5) to 5.95 (+/- 0.33) nmol/L in HP cows. In all cows of the HP group and most cows of the LP group, milk PTHrP concentration was highest in the day-1 sample. Milk PTHrP concentration correlated positively with milk Catot concentration in HP cows (r = 0.5959, P < 0.0001). In contrast, there was a negative relation between milk PTHrP and milk Catot concentrations in LP cows (r = -0.3285, P < 0.02). Milk PTHrP concentration was not correlated with serum Ca2+ concentration at postpartum days 5 and 6, when serum Catot and Ca2+ concentrations had returned to prepartum values. Because correlation of the corresponding day, milk PTHrP concentration most likely is not a major determinant of Ca transport into milk and the PTHrP released into the blood stream is most likely not a major determinant of the endocrine regulation of serum Catot and Ca2+. Thus, although it is involved, PTHrP is not a major factor in the integrative endocrine, paracrine, and autocrine regulation of Ca homeostasis in lactating cows. It is hypothesized that Ca may be actively transported from blood into milk with a process modulated by PTHrP. These data suggest that PTHrP produced by the mammary gland is most likely not involved in the pathogenesis of parturient paresis (milk fever) in dairy cows.