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Biomedical subjects

A R Dillon

Publications and source records attributed to A R Dillon.

30 records · Page 2Linked to original sources

Effects of dexamethasone and surgical hypotension on the stomach of dogs: clinical, endoscopic, and pathologic evaluations.

Effects of dexamethasone and surgical hypotension on the gastric mucosa of 15 dogs was evaluated by clinical, endoscopic, and pathologic studies. Dexamethasone produced acute reddening of the gastric mucosa with frank hemorrhage, digested blood, and possible gastric erosions, whereas dogs treated by surgical hypotension did not have marked changes in the gastric mucosa. Gastrointestinal disease observed in dogs with spontaneous spinal cord injury that were given dexamethasone and decompressive spinal surgery was not produced. The role of corticosteroids and surgical hypotension in the pathogenesis of gastric lesions and the potential for spinal cord injury to produce gastrointestinal disease is discussed.

Animals↗

Effects of dexamethasone and surgical hypotension on hepatic morphologic features and enzymes of dogs.

Effects of corticosteroids and surgical stress on hepatic morphologic features and enzymes were studied in 18 mature dogs of mixed breeding: group 1, control (n = 3); group 2, dexamethasone (n = 5); group 3, dexamethasone and surgery (n = 5); and group 4, surgery (n = 5). Dexamethasone (2.2 mg/kg of body weight twice a day subcutaneously) was administered for 8 days in groups 2 and 3 dogs. All dogs were anesthetized with thiopental for 10 minutes on days 0, 2, and 4. On day 2, dogs in groups 3 and 4 were intubated and maintained on methoxyflurane and oxygen, and a liver biopsy, hemilaminectomy (T13-L1), and 15 minutes of hypotension (75/45 mm of Hg) induced by methoxyflurane were done. Serum alkaline phosphatase (ALP) activity, ALP isoenzymes, and alanine aminotransferase (ALT) activity were determined on days 0, 2, 3, 5, and 8. All dogs were euthanatized and necropsied on day 8. Serum hepatic enzyme activity and hepatic morphologic characteristics were normal for group 1 control dogs. The mean ALP and ALT were significantly (P less than 0.05) increased in dogs in groups 2, 3, and 4. In group 2, the mean ALP (days 5 to 8) and ALT (day 8) were significantly (P less than 0.05) increased. In group 3, the mean ALP and ALT activities were significantly increased on days 2 to 8. In group 4, the mean ALP was significantly increased on days 2 to 8 and the mean ALT was significantly increased on days 3 and 5. All other values were normal. A single isoenzyme band (Rf = 0.399 +/- 0.023, mean +/- SD) was identified in all dogs. Hepatic morphologic changes attributed to dexamethasone were mild-to-moderate vacuolation in a diffuse distribution on day 2 (group 3) and aggregates of moderate-to-severe vacuolation in mainly a periportal distribution on day 8 (groups 2 and 3).(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine Transaminase↗

Distal polyneuropathy after canine heartworm disease therapy complicated by disseminated intravascular coagulation.

A 3-year-old male Setter-type dog had a progressive distal sensorimotor polyneuropathy characterized by weakness, bilateral atrophy of distal appendicular musculature, and reduced response to tactile stimuli. The diagnosis of a distal axonopathy was supported by electromyographic findings of fibrillation potentials, positive sharp waves in distal limb muscles, and absence of evoked action potentials, myopathic changes of atrophic angular fibers, and myelinated nerve fiber depletion in distal parts of peripheral nerves. The neuropathy appeared 5 weeks after 38 days of heparin therapy for disseminated intravascular coagulation. The disseminated intravascular coagulation, a complication of thiacetarsamide therapy for heartworm disease, had resolved 40 days after the end of heparin therapy. The cause of the neuropathy was not determined.

Animals↗

Hypothyroid myopathy in two dogs.

Biopsy specimens of skeletal muscle and peripheral nerve from two dogs with primary hypothyroidism but without clinical neuromuscular disease were studied with histological, histochemical and morphometric techniques. The most prominent change in skeletal muscle was variation in fiber size associated with a pronounced reduction in mean diameter of type II fibers. Type II fiber loss was apparent in the specimen from one dog. No histological or morphometric differences were noted in nerves from either dog compared with an age-matched control. The myopathic findings suggest a preferential metabolic defect in type II muscle fibers.

Animals↗

Subclinical myopathy associated with hyperadrenocorticism in the dog.

One of seven dogs with clinical signs of hyperadrenocorticism had clinical evidence of neuromuscular disorder. Clinical diagnosis of hyperadrenocorticism was confirmed by plasma cortisol concentrations before and after adrenocorticotrophin hormone and dexamethasone administration. Electromyographic studies showed bizarre, high frequency discharges in all dogs. Examination of muscle biopsies taken from the biceps femoris muscle from each dog revealed mild degenerative changes of fiber size variation, focal necrosis and fiber splitting. Ragged red fibers were prominent and appeared to be related to mitochondrial aggregates. Significant (P less than 0.05) type 1 and 2 fiber atrophy was found in all dogs. Fiber grouping was present in four dogs. Studies of fascicular biopsies of the peroneal nerve showed thinly myelinated fibers, onion-bulb formation, segmental demyelination and short intercalated internodes. These findings suggested a glucocorticoid-related myopathy in hyperadrenocorticism that also may have a neurogenic component.

Adrenal Cortex Diseases↗

Experimental hemorrhage in splenectomized and nonsplenectomized dogs.

Ten splenectomized and ten nonsplenectomized conscious dogs were subjected to hemorrhage of 41% of their blood volume over a 15-minute period. Hemodynamic and metabolic variables were monitored for 4 hours after hemorrhage. Mortality (100%) occurred in the splenectomized group. Significant (P < 0.001) hemodynamic responses after hemorrhage included hypotension, tachycardia, low central venous pressure, and decreased ECG voltage of the R wave. Tachypnea was noted in the absence of hypoxia, hypercapnia, and acidosis inthe nonsplenectomized dogs. Significant (P < 0.001) hypocapnia and mean PCO2 values of 13.9 MM of Hg and 23.5 mm of Hg in splenectomized and nonssplenectomized dogs, respectively, was noted. Mean hemoglobin levels were significantly (P < 0.001) decreased after hemorrhage in the splenectomized dogs. The absence of a change in hemoglobin in thenonsplenectomized dogs was attributed to the translocationof extracellular fluid into the vascular space which diluted the high concentration of RBC from splenic contraction. Other changes noted after hemorrhage were hyperglycemia, increased blood cortisol, and increased pyruvate and lacte levels. Changes were not noted in pyruvate-to-lactate ratios.

Animals↗

Identification of an intrinsic platelet function defect in Spitz dogs.

A recently identified intrinsic platelet function defect in 2 Spitz dogs is described. Both affected dogs had a history of chronic intermittent bleeding primarily from the nasal, oral, and gastrointestinal mucosa. Platelet aggregation in response to adenosine diphosphate (ADP), collagen, and platelet activating factor (PAF) was absent; however, platelet shape change did occur. Platelets aggregated in response to gamma thrombin, although a delayed onset and a reduced velocity of aggregation were present. Platelet 14C-serotonin release was diminished in response to collagen and PAF. Glycoprotein IIIa was detected on the surface of platelets by flow cytometry. Platelets were morphologically normal under light and electron microscopy. Two male Spitz dogs, related to one of the affected dogs, did not have a bleeding diathesis. Collagen-induced platelet aggregation, however, was diminished in these 2 dogs. This platelet defect most closely resembles the defect described in Basset hounds.

Animals↗

Obstructive tracheal mass due to an inflammatory polyp in a cat.

A 13-year-old, male domestic shorthair was presented for a 1.5-year history of progressive dyspnea. Multiple intratracheal masses were seen on thoracic radiographs and during bronchoscopy. A diagnosis of an inflammatory polyp infiltrated with lymphocytes and plasma cells was made on histopathological examination of the largest mass following excisional biopsy.

Animals↗

Left ventricular outflow tract to left atrial fistula associated with endocarditis in a dog.

A one-year-old, intact male, 28-kg, mixed-breed dog developed neurological episodes consistent with emboli. An acquired III/VI holosystolic heart murmur was ausculted in the mitral area, and valvular endocarditis with pulmonic and aortic insufficiency were noted at echocardiographic examination. An abnormal communication (i.e., fistula) between the left ventricular outflow tract (LVOT) and the left atrium adjacent to the mitral valve annulus was noted with Doppler imaging and confirmed with angiography. Infective valvular endocarditis was confirmed based on two of three blood cultures being positive for Staphylococcus intermedius. In humans, a sequela to infective endocarditis of the aortic or mitral valve, or both, is rupture of the mitral-aortic intervalvular fibrosa, resulting in a communication between the LVOT and the left atrium. This is the first report of this sequela in the dog.

Angiocardiography↗