The effects of whole-body potassium depletion induced by food deprivation on plasma, erythrocyte, and middle gluteal muscle K concentrations was quantified in 16 healthy, adult horses before, during, and at the end of a 7-day period of food deprivation during which water and sodium chloride were available ad libitum. Potassium concentrations were determined by atomic absorption spectroscopy. Plasma K concentration remained constant (3.49 +/- 0.09 mM K/L of plasma; mean +/- SEM) throughout the study. Erythrocyte potassium concentration decreased from 93.10 +/- 1.94 mM K/L of erythrocytes on day 0 to 88.63 +/- 2.39 mM K/L of erythrocytes on day 2 (decrease of 4.8%; P < 0.05) and thereafter did not change. The K concentration of the middle gluteal muscle decreased from 91.06 +/- 2.96 micromole K/g of muscle (wet weight) to 79.61 +/- 2.09 micromole K/g of muscle (decrease of 12.6%; P < 0.05) on day 4 and decreased further on day 7 to 73.62 +/- 1.85 micromole K/g of muscle (decrease of 19.2%; P < 0.05). There was no correlation between the plasma and erythrocyte K concentrations (r = -0.066), the erythrocyte and middle gluteal muscle K concentrations (r = 0.167), or the plasma and middle gluteal muscle potassium concentrations (r = -0.018). The water content of the middle gluteal muscle remained constant (73.23 +/- 0.36%) throughout the study. Erythrocyte membrane potential did not change (-99.26 +/- 0.87 mV) during the study, whereas the magnitude of the membrane potential of the middle gluteal muscle decreased from -105.84 t 1.67 mV on day 0 to -100.93 +/- 2.10 mV on day 7 (P < 0.05).

Canine erythrocytes were loaded with the antineoplastic drug doxorubicin and then treated with 0.16% glutaraldehyde. This procedure has been previously shown to slow down the efflux of doxorubicin from erythrocytes and to result in the selective targeting of the carrier erythrocytes to liver. Three dogs were treated each with 2 different schedules of IV bolus administration of doxorubicin (0.4 mg/kg of body weight): free drug and doxorubicin encapsulated in glutaraldehyde-treated erythrocytes. The 2 treatments yielded consistent differences in the plasma pharmacokinetic properties of doxorubicin and of its only metabolite, doxorubicinol. A triphasic exponential decay of doxorubicin plasma concentrations was observed on injection of the free drug. Conversely, in the case of erythrocyte-encapsulated doxorubicin, 4 phases of plasma concentrations of doxorubicin were found. The plasma concentrations of doxorubicinol, after a steady increase during the first hour, followed patterns of decay comparable to those of the parent drug. On the basis of the kinetic variables calculated with the 2 administration schedules, area under curve concentrations of plasma doxorubicin were 136 microgram.h/L (free infusion) and 734 microgram.h/L erythrocyte-encapsulated drug). Significant alterations of hematologic and hematochemical factors were not observed in the 3 dogs during and after the 2 treatments. On the basis of our findings, doxorubicin-loaded and glutaraldehyde-treated erythrocytes may potentially be used in the treatment of systemic and hepatic tumors in dogs.

Central venous pressure (CVP), portal pressure (PP), and heart rate (HR) were monitored in 6 female, sexually intact, middle-age Beagles during temporary portal vein obstruction, anesthetic recovery, abdominal bandaging, and propranolol administration. Intraoperative baseline PP was 7.3 mm of Hg (+/- 1.7 SD). Portal pressure was significantly increased throughout portal vein occlusion, but returned to baseline values 2 minutes after release of the ligature. Central venous pressure was significantly decreased throughout portal vein occlusion, but did not differ significantly from baseline values 3 minutes after release of the portal vein ligature. Portal pressure increased significantly (8 +/- 3.3 mm of Hg) over baseline values after application of an abdominal bandage; however, CVP did not change significantly. During postoperative monitoring, CVP and PP did not change significantly from respective 18-hour mean postoperative values in resting dogs. At 60 and 75 minutes after surgery, heart rate was significantly increased over the 18-hour mean. Portal pressure and CVP, respectively, were significantly increased over intraoperative baseline values in the first hour and the first 8 hours after surgery. Postoperative CVP and HR were significantly correlated. Individual measurements of PP in dogs that were abdominal pressing during barking or defecation were significantly increased (9 +/- 3 mm of Hg) above measurements taken after cessation of abdominal press. Portal pressure measurements in standing dogs decreased 7.5 +/- 2 mm of Hg, compared with measurements of the same dog in lateral recumbency. Central venous pressure was inaccurate in dogs performing abdominal press. Portal pressure did not decrease significantly from baseline after injection of propranolol (2 mg/kg, IV). Central venous pressure was significantly decreased at 2.5 and 3.0 hours after propranolol injection, and HR was significantly decreased from 1 to 3.5 hours after injection. Heart rate quickly returned to normal values if the dogs became excited. After propranolol administration, significant correlations were found between PP and HR, and between CVP and HR.

Furazolidone cardiotoxicosis was induced in 2 groups (FZ and FZ-CR groups) of newly hatched male Pekin ducklings (100/group) by feeding a ration containing 650 mg of furazolidone/kg of feed (ppm) for 28 days. A third group (control ration, CR group; n = 100) was fed the same ration without furazolidone. On day 28, the control ration was initiated for the FZ-CR group initially given the furazolidone-containing ration, to allow recovery from the effects of the drug, whereas ducklings of the FZ group continued to consume the furazolidone-containing ration. Biweekly, beginning with week 4, ducklings were euthanatized to assess severity of gross lesions and to obtain sections of myocardium for histologic and ultrastructural examination. Clinical evidence (increased weight gain, increased feed consumption, decreased mortality, reduced prevalence of palpable ascites) of regression of cardiotoxicosis of ducklings of the FZ-CR group was nearly complete by day 56 (28 days after cessation of furazolidone intake). Likewise, regression of gross lesions, as measured by overall prevalence of gross lesions, left ventricular volume, and ascites prevalence and severity, were also essentially complete by day 56. Myofibrillar lysis was not seen in sections from the heart (examined ultrastructurally) obtained from ducklings of the CR group that were euthanatized on day 28, 56, or 98. Myofibrillar lysis was detected in all ducklings (4/4) fed furazolidone (FZ and FZ-CR groups) and euthanatized on day 28. Myofibrillar lysis was not seen in the heart of ducklings of the FZ-CR group that were euthanatized on day 56 or 98. Myofibrillar lysis was detected in the heart from all ducklings of the FZ group that were euthanatized on day 56. Leptomeres were observed in cardiac myocytes of ducklings that had been fed furazolidone, but not in those fed only the control ration. Our clinical, gross pathologic, and ultrastructural findings indicate that regression of the cardiac lesions of furazolidone toxicosis may be essentially complete by 28 days after cessation of furazolidone intake. Our ultrastructural findings indicate that furazolidone consumption may result in cardiac dilatation by altering myofibrillar/cytoskeletal attachments of myocytes.

To evaluate the use of technetium pertechnetate (99mTcO4) as a means of estimating gastric mucosal integrity, nuclear images of the empty stomach were obtained from 6 dogs at 20, 40, 60, 120, 180, and 240 minutes after IV administration of the radiopharmaceutical. Blood and gastric secretion samples were collected during the same time intervals. The left lateral-view image of the stomach was used to calculate the relative fraction of the dose in the stomach and the count density ratio. Between 20 and 40 minutes and 40 and 60 minutes, significant differences (P < 0.001) were apparent in the amount of 99mTcO4 in the stomach. Blood concentration of 99mTcO4 decreased significantly (P < 0.001), whereas gastric secretion concentration increased significantly (P < 0.001) over time. Qualitative assessment of the gastric nuclear scans and the statistical analytic results indicated that the optimal time for imaging the canine stomach was between 40 and 60 minutes after radiopharmaceutical administration. In a second study, the same dogs were pretreated with the H2-receptor antagonist cimetidine and the cholinergic antagonist glycopyrrolate to block gastric secretions. Over time, changes in the relative dose fraction in the stomach and the density ratio were the same as values obtained during the experiment performed without use of cimetidine and glycopyrrolate. Results of the study indicate that nuclear imaging with 99mTcO4 outlines normal canine gastric mucosa and that pretreatment with cimetidine and glycopyrrolate has no effect on the quality of the gastric image.

Previous work had indicated that the 2 canine hookworms, Ancylostoma caninum and Uncinaria stenocephala, may differ in their susceptibility to treatment with milbemycin oxime. Thus, the study reported here was to examine the effects of this drug on concomitant infections in experimentally infected dogs. Twenty specific-pathogen-free Beagles were inoculated orally with 500 infective-stage larvae from a mixture of larval A caninum and U stenocephala. Quantitative fecal examinations were performed weekly, beginning the day of infection. The dogs were assigned to 2 equal groups, 1 group that received the compound and 1 that received a placebo. The dogs were treated on postinoculation days 30, 60, and 90. For A caninum, egg counts dropped precipitously after the first treatment, and no eggs of this species were found in the feces of any of the treated dogs after the second treatment. The treatments had no significant effect on the mean egg counts made on U stenocephala, although 2 dogs stopped passing eggs entirely after the second treatment. At necropsy, no A caninum were found in any of the treated dogs; the mean number recovered from the control-group dogs was 56.1. Significant difference was not found in the mean number of adult U stenocephala recovered from the treated and control groups (27.0 and 21.7, respectively).

The effect of humidity on the histologic lesions induced by high-frequency jet ventilation was investigated in 12 healthy cats. After 16 hours of ventilation, the appearance of the tracheal epithelium ranged from normal to necrotic. The damage was considerably more severe in the trachea of cats of the group ventilated without added humidity. Increasing the relative humidity to 63% at 24 C had a protective effect, but further increasing the relative humidity to 92% at 35 degrees C did not appear to provide significantly more protection. The bronchi and distal airways had minimal, if any, damage in all groups.

Aqueous outflow from cannulated canine eyes was determined, using a constant-pressure perfusion technique. The effect of topically applied flurbiprofen, a cyclo-oxygenase inhibitor, on outflow in eyes with or without neodymium:yttrium aluminum garnet laser-induced inflammation was measured. Flurbiprofen caused decrease in aqueous outflow that was more marked in the inflamed eyes.

Two diets similar in caloric density and mineral content, but markedly different in protein content, were used to study the effects of dietary protein on renal function and morphologic and histopathologic changes in dogs that had functional renal tissue reduced by seven-eighths nephrectomy. The effects of moderate protein intake (MPrI = 15% protein; dry-matter basis) and high-protein intake (HPrI = 31% protein; dry-matter basis) were studied for the initial 7 months (period 1 [P1]) after renal mass reduction. Diets were then switched between groups during the following 7 months (period 2 [P2]) to evaluate the effects of increased or decreased protein intake. The HPrI caused significantly (P < 0.05) greater glomerular filtration rate (GFR) and renal growth than did MPrI during P1. Dogs that maintained HPrI during P1 and MPrI during P2 (group 1) had significant (P < 0.05) reduction in GFR during P2. Dogs that maintained MPrI during P1 and HPrI during P2 (group 2) had significant (P < 0.05) improvement in GFR and renal growth during P2. At the end of the study, renal reserve was evaluated in both groups of dogs before and after group 1 was returned to HPrI for 2 weeks. During this 2-week feeding trial, group-1 dogs had marked improvement in renal reserve, relative to group 2, and GFR increased to the terminal P1 values. Results indicate a possible residual benefit from HPrI during the early phase of compensatory renal growth in the form of functional compensatory memory to HPrI. The severity of renal lesions was indistinguishable between dogs of dietary groups during both study phases. Plasma electrolyte concentrations rapidly returned to normal range after renal ablation, but mild azotemia and proteinuria persisted throughout most of the study. High protein intake was not associated with increased degree or progression of proteinuria.

Twenty-four healthy cats underwent bronchoscopy and bronchoalveolar lavage to determine the normal cytologic environment of the lower respiratory tract of cats. Initial screening to ensure the health of the study population included complete histories, physical examinations, thoracic radiography, CBC, serologic tests for feline leukemia virus, feline immunodeficiency virus, and occult heart-worm, and sugar and Baermann fecal flotation. In 18 cats, protected catheter brush samples of airway secretions from the lavaged lung segment were taken for culture of aerobic and anaerobic bacteria and mycoplasma. Bronchial lavage fluid (5 sequential 10-ml aliquots of normal saline solution) was pooled and filtered with cotton gauze. The unspun sample was used for determination of a total nucleated cell count. Lavage fluid was cytocentrifuged and 500 cells/slide were scored for determination of the cellular differential. Activity of lactate dehydrogenase and concentrations of total protein and IgG within the supernatant were measured, and assays were performed to detect the presence of IgA and IgM. Complete histologic evaluation of the lavaged lung of each of 6 random-source cats was performed after differential cell counting revealed 18% eosinophils within bronchoalveolar lavage fluid recovered from this group. Alveolar macrophages were the predominant cells encountered; however, a quarter of all cells recovered were eosinophils. A significant relationship was not found between the abundance of eosinophils in the lavage fluid, and either isolation of aerobic bacteria, high total nucleated cell counts, total protein concentrations, or activity of lactate dehydrogenase. Histologic evaluation of the lungs of 5 of 6 random-source cats revealed normal lungs in 2 cats, and minimal abnormal change in 3 others. Evaluation of the lungs from 1 random source cat revealed acute, mild eosinophilic bronchiolitis. We conclude that large numbers of eosinophils may be retrieved from the bronchoalveolar lavage fluid of healthy cats.