Ouabain, a cardiac glycoside, binds to the Na+-K+i-adenosine triphosphatase (Na+ pump) and prevents active transport of Na+ and K+ across cell membranes. We used [3H]ouabain to quantify the number and affinity of Na+ pumps in skeletal muscle from Quarter Horses with the muscular disorder hyperkalemic periodic paralysis (HYPP). [3H]Ouabain-binding properties of gluteal muscle from clinically normal and affected horses were used to determine whether altered Na+ pump number or affinity could contribute to the pathologic features of muscle in affected horses. Foals and adult horses with HYPP were compared with age-matched clinically normal horses. The number of [3H]ouabain-binding sites in adult gluteal muscle was not different between the 2 types of horses (85.7 +/- 8.9 pmol of [3H]ouabain-binding sites/g [wet muscle weight] in horses with HYPP vs 100.2 +/- 8.8 pmol/g in clinically normal adult horses). Gluteal muscles in HYPP-affected and clinically normal foals also contained a similar number of [3H]ouabain-binding sites (222.3 +/- 21.0 pmol/g vs 225.3 +/- 24.2 pmol/g, respectively). The affinity of these binding sites for ouabain was not different, between adults or foals, in clinically normal or affected horses. Our results indicate that membrane events underlying the periodic episodes of paralysis in horses with HYPP are not attributable to quantitative changes in Na+ pump number or affinity. Our data cannot exclude the possibility that the specific activity of the Na+ pump is altered in muscle from HYPP-affected horses.

Right dorsal colon fistulas, 2.5 cm in diameter, were created in 2 healthy ponies, using a 2-stage surgical procedure. The first stage consisted of resection of portions of the 16th and 17th ribs on the right side, followed by surgical creation of a 6- to 8-cm-diameter adhesion between the right dorsal colon and the body wall. Fistulas were created approximately 2 weeks after the first surgery by sharp dissection through the adhesion into the lumen of the colon. The fistulas have been satisfactorily maintained for > 2 years by de Pezzer catheters (45 F). Ponies with fistulas have been used for gastrointestinal experiments.

Characteristic alterations in the serum and urine biochemical profiles of Doberman Pinschers with congestive heart failure (CHF) resulting from idiopathic dilated cardiomyopathy were determined. We compared these alterations with those observed in 2 other models of CHF: rate overload induced by rapid ventricular pacing in dogs, and biventricular hypertrophy and dilatation induced in turkey poults by furazolidone toxicosis. Serum and urine biochemical changes in both models of CHF in dogs were mild to moderate in degree, and were moderately consistent, They could be attributed to secondary neurohumoral, hepatic, and renal effects of heart failure. The most marked and consistent changes observed were mildly decreased anion gap that developed, in part, because of decreased serum sodium concentration, moderately increased catecholamine concentrations, moderate lactaciduria, hyposthenuria, and mildly increased urea concentrations and liver enzyme activities. In birds with furazolidone cardiomyopathy, we observed mild increases in serum urate concentration, liver and muscle enzyme activities, but moderately increased sodium concentration with decreased chloride concentration. In the pacing and furazolidone models, in which CHF was rapidly induced, moderate to marked hypoproteinemia was attributable to decreases in albumin and globulin concentrations. Using the avian model we found that the hypoproteinemia could be largely attributed to blood volume expansion, and to a lesser extent, inanition. Development of hypoalbuminemia during rapid ventricular pacing and furazolidone treatment may contribute to the effects of rate overload or drug toxicity in the pathogenesis of CHF, because hypoalbuminemia may contribute to altered hemodynamics and neuroendocrine system activation. Our data indicate that clinical biochemical analysis of serum and urine may be useful for assessing progression of CHF.

Plasma cortisol and corticosterone responses of 8 clinically normal adult ferrets to synthetic ACTH (cosyntropin) were evaluated. Cosyntropin was administered iv at 4 dosages (0.5, 1.0, 5.0, and 10 micrograms/kg of body weight) at 2- to 4-week intervals, with blood samples collected 60 and 120 minutes after injection. After completion of the studies, an additional ACTH stimulation test was performed by administering cosyntropin (1.0 micrograms/kg) IM. The baseline plasma cortisol concentrations from all studies ranged from 25.9 to 235 nmol/L (mean +/- SEM = 73.8 +/- 7.0 nmol/L), and plasma corticosterone values ranged from 1.7 to 47 nmol/L (mean +/- SEM = 8.3 +/- 1.1 nmol/L). After iv administration of cosyntropin, plasma concentrations of cortisol and corticosterone increased significantly (P < 0.05) and reached peak values at 60 minutes; however, there were no significant differences between plasma cortisol or corticosterone responses to the 4 dosages of cosyntropin. Intramuscular administration of 1.0 Kg of cosyntropin/kg induced increases in plasma cortisol and corticosterone concentrations that were similar to the responses induced by iv administration of cosyntropin. The mean molar ratio of cortisol to corticosterone, calculated from the resting plasma concentrations, was approximately 9:1, whereas the ACTH-stimulated cortisol to corticosterone ratio was approximately 4:1. Results of this study indicated that administration of cosyntropin to clinically normal ferrets, at dosages ranging from 0.5 to 10 micrograms/kg, increased plasma concentrations of cortisol and corticosterone. Although cosyntropin stimulates the adrenocortical secretion of cortisol and corticosterone, cortisol appears to be the predominate circulating glucocorticoid in ferrets.

Undifferentiated distal respiratory tract disease (nasal discharge, cough, pneumonia) in foals (1 to 8 months old) is a burdensome economic problem on breeding farms yet, the infective agents associated with these episodes have not been well described. Possible causes of these episodes of illness were investigated by culturing specimens of proximal and distal airways of clinically diseased foals (n = 101), prior to any treatment, for aerobic and anaerobic bacteria and viruses (rhinoviruses, equine arteritis virus, equine herpesvirus subtype 1 [EHV-1], influenza virus, and adenovirus). Pairs of sera (n = 47) were examined for antibodies to influenza A virus, equine subtypes 1 and 2, EHV-1, and adenovirus antigens, and sera obtained from foals during acute infection were examined for antibodies (by agar gel immunodiffusion [AGID]) to equi factor antigens of Rhodococcus equi. Viruses were not isolated from the proximal (swab) or distal (bronchial lavage) airway specimens in foals, and only 2 of 47 randomly selected foals seroconverted to EHV-1. Serotiters to the other viruses were low and frequently decreasing between samples, which was compatible with maternally derived antibody. Streptococcus zooepidemicus was the predominant isolate from bronchial lavage specimens (88/101 cases), accompanied by alpha-hemolytic streptococci (8 cases), Bordetella bronchiseptica (13 cases), Staphylococcus epidermidis (9 cases), and other organisms in lesser frequency. Only Str zooepidemicus was recovered significantly (P < 0.05) more often in cases than in controls. The AGID test was found useful to detect 1/26 with presumed exposure to R equi, but positive tests results did not correspond well with bacterial culture results; positive AGID results were recorded in 34% of culture-negative foals. However, foals from which R equi was isolated were distinctive from the other foals on the basis of fever (> 39 C), lack of nasal discharge, blood neutrophilia and decreased percentage of neutrophils in bronchial lavage fluid samples. Isolation of Str zooepidemicus was significantly (P < 0.01) associated with increasing neutrophil percentage in bronchial lavage fluid. In conclusion, the pathogenic roles of Str zooepidemicus and R equi were established in this group of foals with distal respiratory tract infections by use of clinical, endoscopic, hematologic, and cytologic methods. There was no evidence of a viral cause for these infections, indicating that manifestations of distal respiratory tract infection are attributable to bacterial infection causing inflammation of the airways. Further studies are warranted to pursue more-sensitive methods for detection of viral antigen or antibody in undifferentiated distal respiratory tract disease episodes in foals.

The 1-host tick Boophilus annulatus was found to transmit anaplasmosis in cattle transstadially. Anaplasma marginale was invariably transmitted when ticks that had been pulled off Anaplasma-infected calves either after 7 days (as fully engorged larvae) or after 14 to 15 days (as fully engorged nymphs) were transferred within 4 days to susceptible calves. Three morphologically different A marginale isolates, 1 round (tailless) and 2 with different types of appendages (tailed) were transmitted by the ticks. These findings might explain the overlap of the geographic distribution of the disease and that of Boophilus spp in some areas of the world.

Transcutaneous oxygen monitoring is commonly used in human beings to assess skin viability. Little attention has been directed toward the use of transcutaneous carbon dioxide (P(CO2.TC)) monitoring for the same purpose. The application of P(CO2.TC) monitoring for evaluating skin viability in dogs was investigated. The changes in P(CO2.TC) and local power reference (LPR) values were measured from 16 skin flaps created along the lateral hemithoraces of 4 dogs. Transcutaneous P(CO2) and LPR values were serially recorded from the base and apex of each flap for 12 hours. A single measurement was obtained from each flap base and apex 24 hours after surgery. Arterial blood gas analyses were obtained to compare central P(CO2) values with peripheral skin P(CO2) values. The flaps were observed for 4 days and then harvested for histologic examination. Full-thickness skin biopsy specimens were obtained 24 hours after surgery and when the flaps were harvested to evaluate the viability of the apex and base of the flaps. A subjective grade was assigned to all skin biopsy specimens during histologic examination. For all measurements, a significant difference was found between the P(CO2.TC) values for apices and bases of the flaps. The mean P(CO2.TC) for all bases was 52.66 mm of Hg +/- 2.24 (SEM), and the mean P(CO2.TC) for all apices was 106.4 mm of Hg +/- 2.44. The regional carbon dioxide index (apex P(CO2.TC)/base P(CO2.TC) was 2.02. A significant difference was not found between the LPR values for bases and apices. The mean LPR for all bases was 253.23 mW +/- 4.06, and the mean LPR for all apices was 243.53 mW +/- 4.49. A significant difference was found between the histologic grades assigned to the collective bases and apices 4 days after creation of the flaps. A difference was not found between the collective bases and apices 24 hours after flap creation. On the basis of our findings, transcutaneous carbon dioxide monitoring is a useful method of evaluating skin viability in dogs.

Development of the rickettsia, Anaplasma marginale, salivary glands of male Dermacentor andersoni exposed as nymphs or adult ticks, was studied indirectly by inoculation of susceptible calves with homogenates and directly by examination, using light microscopy and a DNA probe; some unfed ticks were incubated before tissues were collected. Salivary gland homogenates made from ticks in every treatment group caused anaplasmosis when injected into susceptible calves; prepatent periods decreased as the time that ticks had fed increased. Colonies of A marginale were seen only in salivary glands of ticks exposed as adults and not in those exposed as nymphs; the percentage of salivary gland acini infected in these ticks increased linearly with feeding time. However, the probe detected A marginale DNA in salivary glands of ticks from both groups; the amount of DNA detected increased as feeding time was extended. The amount of A marginale DNA appeared to remain constant in gut tissues, but to increase in salivary glands. Salivary glands of adult-infected male ticks that were incubated, but did not feed a second time, became infected with A marginale, and the pattern of infection of acini varied with incubation temperature. Development of A marginale in salivary glands appears to be coordinated with the tick feeding cycle; highest infection rate was observed in ticks exposed as adults.

An agar gel immunodiffusion (AGID) test was used over a 3-year period to examine 1,871 serum samples from sheep representing 5 Mycobacterium paratuberculosis infected flocks and 4 flocks presumed to be uninfected. Of 1,032 sheep, 31 had positive AGID test results (scoring 1 to 5), and 23 of these 31 were ecropsied. Infection with M paratuberculosis was confirmed by 1 or more of the following findings: observation of typical lesions on histologic examination of sections of ileum or ileocecal lymph nodes, observation of clumps of acid-fast bacteria in mucosal smears of ileum, and isolation of the organism from feces or tissue. False-positive results on AGID testing were not found in sheep from flocks known to have exposure to Cotynebacterium pseudotuberculosis. Diarrhea in infected sheep was observed infrequency; chronic, severe weight loss was the most common sign observed. On histologic examination of tissues from 20 infected sheep, 16 (80%) had diffuse lesions of the ileum and 13 (65%) had acid-fast bacteria in areas of ileal inflammation; 4 had discrete granulomas and peripheral lymphocytic infiltrates in the ileum. Sheep with diffuse lesions tended to have higher mean scores on AGID testing and examination for acid-fast bacteria, compared with those from sheep with more discrete lesions. Bacteriologic culture yielded M paratuberculosis from only 3 sheep with paratuberculosis. On the basis of results of this study, we suggest that the nature of the response to infection with M paratuberculosis may influence the results of diagnostic tests for paratuberculosis, and that AGID testing may be useful to identify M paratuberculosis infection in sheep with chronic weight loss and in flock-screening programs.

The prevalence of mycoplasmal and ureaplasmal recovery from tracheobronchial lavage specimens and the prevalence of mycoplasmal recovery from pharyngeal swab specimens from dogs with (n = 38) or without (n = 26) pulmonary disease were determined. Similar mycoplasmal recovery rates were found for tracheobronchial lavage specimens from dogs > 1 year old with (21%) or without (25%) pulmonary disease. Prevalence of mycoplasmal recovery from tracheobronchial lavages was significantly associated with pulmonary disease among dogs < 1 year old (P = 0.04), and with dogs that had concurrent Bordetella (P = 0.006) and Streptococcus (P = 0.05) isolations. Among dogs with pulmonary disease, mycoplasmas were significantly (P = 0.02) more prevalent in dogs with septic inflammation than in dogs with nonseptic inflammation of the tracheobronchial tree. Ureaplasmas were only isolated from a tracheobronchial lavage specimen of 1 dog with pulmonary disease and from none of the dogs without pulmonary disease. Most dogs with (84%) and all dogs without pulmonary disease had mycoplasmas isolated from the pharynx. Seemingly, mycoplasmas are part of the normal pharyngeal flora of most dogs and normal inhabitants of the lower airway in about a fifth to a fourth of the canine population greater than or equal to 1 year old. Dogs < 1 year old with pulmonary disease and dogs with concurrent Bordetella or tracheobronchial streptococcal isolations may be more susceptible to mycoplasmal colonization of the lower airways. Seemingly, ureaplasmas are rarely associated with pulmonary disease, and are not normal inhabitants of the trachea and bronchi of dogs.