Plasma concentration of immunoreactive atrial natriuretic peptide (ir-ANP) was investigated in 83 Cavalier King Charles Spaniels with variable severity of mitral regurgitation caused by chronic valvular disease (CVD). Severity of mitral incompetence was assessed by echocardiography. Significant differences in plasma concentrations of ir-ANP were not found between clinically normal dogs (New York Heart Association functional class O), dogs with only cardiac murmur (class I), and dogs with echocardiographic evidence of slight to moderate left atrial and ventricular dilatation (class II). Dogs with severe left atrial and ventricular dilatation and clinical signs of congestion (classes III and IV) were found to have significantly (P < 0.001) increased plasma concentration of ir-ANP. Overall, moderate degree of association was found between plasma concentration of ir-ANP and left atrial and left ventricular diameters (Pearson's r = 0.65, 0.60, respectively, P < 0.001), as well as heart rate (r = 0.47, P < 0.01). However, left atrial enlargement as found to have the predominant effect on plasma ir-ANP concentration. It is concluded that the plasma concentration of ir-ANP did not become markedly increased before decompensation of chronic mitral regurgitation associated with severe enlargement of the left atrium and ventricle in Cavalier King Charles Spaniels.

Schirmer tear test (STT), intraocular pressure (IOP) measurement, slit-lamp biomicroscopy, and indirect ophthalmoscopy were performed on 8 dogs with (13)l-induced hypothyroidism and 4 euthyroid control dogs at weeks 0, 9, 13, 17, immediately prior to treatment with levothyroxine, after 5 weeks of levothyroxine administration (0.022 mg/kg of body weight, PO, q 12 h), and at euthanasia 7 weeks after discontinuation of replacement therapy. Although the control group had higher baseline STT values than the hypothyroid group after randomization of dogs into the 2 groups (P < 0.01), STT values remained unchanged from their respective baseline values at all time intervals for both groups. Hypothyroid and control dogs had significant (P < 0.05) reduction in IOP from baseline values at all subsequent time points, but differences were not observed when hypothroid dogs were compared with controls. Goblet cell indices determined from biopsy samples of the inferior-nasal conjunctival fornix obtained before induction of hypothyroidism (baseline), immediately prior to and at conclusion of levothyroxine therapy, and at euthanasia were not significantly different when values for hypothyroid dogs were compared with their own baseline values or with values for control dogs. Histologic examination of the globes and adnexa at euthanasia also failed to indicate consistent qualitative differences between hypothyroid and control dogs. Marked reduction in serum thyroid hormone concentrations had little effect on the eye and ocular adnexa over the course of the study.

We evaluated the feasibility of using miniosmotic pumps as a way to continuously treat cattle with a singular ergot alkaloid (ergonovine) of known content, thus mimicking the natural fescue toxicosis disease state, but allowing study of specific alkaloid effects. Dosing animals with increasing amounts of ergonovine via miniosmotic pumps, followed by daily acquisition of plasma samples for high-performance liquid chromatographic determination of the alkaloid, resulted in stepwise increases in plasma ergonovine concentration. However, despite the detectable blood concentration of ergonovine, calves did not have typical clinical signs of ergot alkaloid toxicosis. Similarly, serum prolactin concentration was unaffected by ergonovine in these cattle, implicating some other alkaloid of endophyte-infested fescue as causative of the usual prolactin-suppressive response. The results confirm use of this animal dosing method to study biological effects of singular purified alkaloids of known amount, without bioavailability concerns. Thus, this dosing method will facilitate studies to determine the harmful effects of individual alkaloids found in toxic tall fescue, and ultimately, to alleviate their costly effects in cattle, horses, and other species.

Three methods of determining glomerular filtration rate (GFR) were performed in adult ferrets, 9 months to 7 years old. Endogenous creatinine clearance was determined, using serum and urine creatinine values obtained during 24- and 48-hour collection periods from 27 ferrets housed in metabolic cages. Creatinine and radiolabeled inulin were administered to 12 female ferrets by constant IV infusion during isoflurane-induced anesthesia. Serial 20-minute urine collections, together with serum samples obtained at the midpoint of urine collection, provided measures for clearance calculations of these substances. Mean +/- SD endogenous creatinine clearance in ferrets for metabolic cage collections was 2.50 +/- 0.93 ml/min/ kg of body weight. There were no significant differences between the 24- and 48-hour clearance rates. Mean inulin clearance was 3.02 +/- 1.78, and mean exogenous creatinine clearance was 3.32 +/- 2.16 ml/ min/kg. Analysis of variance, using least-squared means adjustment, did not yield any significant differences between inulin and exogenous creatinine clearance rates. Exogenous creatinine clearance-to-inulin clearance ratio was 0.99 +/- 0.46, and there was significant correlation between the 2 methods (r = 0.82, P = 0.0001). Significant body temperature effects on inulin or exogenous creatinine clearance were not found. Infused inulin clearance, the generally preferred method for GFR calculation in mammalian species, was significantly (P = 0.0069) higher in younger (3.65 ml/min/kg) vs older ferrets (2.29 ml/min/kg). Results of this study indicate that inulin clearance is an adequate measure of GFR in ferrets as it is in other species. Compared with inulin clearance, exogenous creatinine clearance also provides a reliable estimate of GFR in ferrets.

A crude, whole-body extract of female heartworms was administered IV to 10 dogs with and 13 dogs without heartworm (HW) infection. Shock developed in 8 of 10 infected dogs and 11 of 13 non-infected dogs, and blood coagulopathy was observed in 12 of 19 dogs with shock. Prevalence and severity of blood coagulopathy were proportionate to prevalence and severity of shock. Platelet count decreased in all dogs with shock with or without blood coagulopathy; thus, the decrease in platelet count might be related to shock. In 4 dogs, activated partial thromboplastin time (APTT) was prolonged--192.0 seconds at 30 minutes after HW injection--and prothrombin time (PT) was increased--13.8 seconds at initial collapse. In 8 dogs, APTT was increased--200 seconds for 2 hours after HW injection--and PT was increased--200 seconds at 30 minutes after the injection. The APTT prolongation might have been caused mainly by decreases in activities of factors VIII, IX, XI, and XII of the intrinsic blood coagulation pathway. In dogs with severely prolonged PT, plasma fibrinogen concentration and factor II activity decreased slightly. Prolonged PT was corrected in vitro by addition of normal plasma at high concentration (> 80%), but prolonged APTT could not be corrected in vitro by addition of 80% normal plasma. Serum fibrin degradation products concentration was < 10 microgram/ml, and soluble fibrin monomer complex was negative in all dogs. Thrombi were not found in blood vessels of any organ at necropsy and after histologic study. Therefore, it was suggested that blood coagulopathy resulting from inhibition of coagulation factor activities might develop in shock induced by HW extract.

Staphylococcal antigens and immune complexes (IC) prepared from antigen and hyperimmune canine serum were tested for their effects on certain functions of mononuclear (MN) and polymorphonuclear (PMN) leukocytes (cells) obtained from healthy dogs. The effect on MN cells was studied by determining the ability of antigen or IC to augment or inhibit mitogenesis induced by phytohemagglutinin (PHA). The effect of antigen or IC on PHA cells was studied by measurement of H2O2 production as an indicator of respiratory burst. Neither the antigen nor the IC, when cultured with MN cells, was mitogenic. Coincubation of antigen or IC with MN cells and PHA resulted in a concentration-dependent decrease in mitogenesis. The decreased mitogenesis could not be overcome by addition of excess PHA, and may in part have been related to toxic effects of the antigen or IC on MN cells. When MN cells were instead preincubated with antigen or IC, then washed and stimulated with PHA, there was still a concentration-dependent inhibition of mitogenesis, although toxicity to the cells was not observed. Low concentrations of staphylococcal antigen or IC stimulated slight H2O2 production by PHA cells. When PHA cells were coincubated with IC and another stimulus (opsonized zymosan or phorbol myristate acetate), IC appeared to augment phorbol myristate acetate-, but not zymosan-induced stimulation. These results suggest that staphylococcal antigens, either alone or complexed with antibody, have the ability to stimulate PMN cells and inhibit MN cell function. Such actions may have a role in the pathogenesis of recurrent staphylococcal infection in canine patients.

Force plate gait analysis was used to study the effects of subject stance time and velocity on ground reaction forces in 6 adult Greyhounds at the trot. Data for 210 valid trials were obtained. Stance time negatively correlated with velocity (r = -0.85 for the forelimbs, r = -0.61 for the hind limbs), decreasing as velocity increased. Stance time in the forelimbs and hind limbs correlated more closely with changes in vertical peak force and impulse than did velocity. The trials were divided into 3 distinct velocity ranges (V1 = 1.5 to 1.8 m/s, V2 = 2.1 to 2.4 m/s, and V3 = 2.7 to 3.0 m/s), 3 distinct forelimb stance time ranges (FST1 = 0.144 to 0.176 second, FST2 = 0.185 to 0.217 second, and FST3 = 0.225 to 0.258 second), and 3 distinct hind limb stance time ranges (HST1 = 0.105 to 0.132 second, HST2 = 0.139 to 0.165 second, and HST3 = 0.172 to 0.198 second). Peak forces increased as velocity increased and decreased as stance time increased. Vertical impulse decreased as velocity increased and increased as stance time increased. The relation between stance time, subject velocity, and ground reaction forces was documented for clinically normal Greyhounds at the trot. Changes in stance time accurately reflected changes in subject velocity and ground reaction forces in clinically normal dogs and could be used to normalize trial data within a sampling period.

Alterations in the size and functions of porcine alveolar macrophages exposed to sublytic amounts of heat-labile, hemolytic cytotoxin produced by Actinobacillus pleuropneumoniae (App) serotype 1, strain HS54 into the culture medium were studied in vitro. Alveolar macrophages were sensitive to the cytotoxin; treatment of the macrophages with low concentrations of cytotoxin (0.016 hemolytic unit) resulted in severe, irreversible cell swelling. However, high doses of cytotoxin (2.0 hemolytic units) were required to cause substantial cell death, as indicated by the influx of propidium iodide into and release of lactate dehydrogenase from cells. Macrophages exposed to low, sublytic doses of cytotoxin failed to migrate toward chemoattractant, were unable to attach to glass, and failed to phagocytize optimally opsonized erythrocytes. Macrophages already attached to glass surfaces detached when exposed to sublytic doses of cytotoxin. The swelling and impairment of functions of alveolar macrophages observed in this study could not be attributed to endotoxic effects, because heat treatment of the cytotoxin preparation for 60 minutes at 60 C resulted in complete loss of cytotoxicity. We conclude that sublytic doses of heat-labile, hemolytic cytotoxic substances produced by App depress alveolar macrophage function at concentrations likely to develop in association with acute pulmonary infection with App. The Apx (A pleuropneumoniae Rtx toxins) exotoxins secreted by the bacteria into culture medium were considered responsible for the toxic activity of the cytotoxin preparation. The Apx of the App field strain used in this study were likely to be similar to those of serotype-1 reference strain (S4707). Analysis by use of DNA-DNA hybridization indicated that genomic DNA of the field strain contained sequences similar to those encoding structural protein of ApxI (apxIA) and ApxII (apxIIA) of the serotype-1 reference strain. Therefore, Apx produced by the field strain of App used in this study are likely to be of similar pathogenic importance worldwide.

Bronchoalveolar lavage was performed through an endotracheal tube in 34 specific-pathogen-free cats to determine expected values for bronchoalveolar lavage fluid cytologic analysis, using this method of collection. Saline solution for lavage was instilled in 3 separate aliquots at a volume of 5 ml/kg of body weight each. Analysis of sequential aliquots was performed to investigate the differences in cell counts among the 3 fractions. The effect of combining aliquots, including or omitting the first fraction, was evaluated to determine whether all aliquots could be combined for analysis without substantially affecting results. The total number of nucleated cells retrieved from each cat ranged from 0.9 to 31.1 X 10(6). Most of these cells were macrophages (78 +/- 15%, mean +/- SD) and eosinophils (16 +/- 14%). The first aliquot had the greatest number of epithelial cells, and the lowest total nucleated cell count and relative and absolute eosinophil counts. Differences among aliquots also were identified for relative and absolute macrophage counts, relative and absolute neutrophil counts, and absolute lymphocyte count. Statistically significant differences were found for many of the cell counts when values from the combination of the second and third aliquots were compared with values from the combination of all 3 aliquots. Magnitude of the differences was small, and these differences were not believed to be of practical consequence.

Hepatobiliary scintigraphy provides a noninvasive assessment of hepatobiliary structure and function, and has been used extensively in people. Hepatocellular measurements determined in the cats of this study include cardiac washout (less than or equal to 2 minutes) and time of maximal hepatic activity (less than or equal to 5 minutes) and hepatic washout (less than or equal to 30 minutes). The gallbladder response to synthetic cholecystokinin was determined to be less than or equal to 3 minutes. Additional measurements also were identified. Potential use of hepatobiliary scintigraphy in feline medicine is discussed.