Ambulatory Dogs Research Articles

Magnetic motor evoked potentials for assessing spinal cord integrity in dogs with intervertebral disc disease.

Magnetically elicited transcranial motor evoked potentials (MEPs) were studied in 37 dogs with type 1 intervertebral disc (IVD) disease. The waveforms were recorded from both cranial tibial muscles before and after surgery. The latencies and amplitudes obtained were compared to those of a control population (n = 14). MEPs were recordable in all dogs with mild or no neurologic deficits, but they were recordable in only 50% of ambulatory dogs that were severely ataxic. MEPs could not be elicited from nonambulatory dogs. There was a significant attenuation of the amplitudes in all clinical cases, even if the dogs demonstrated back pain alone. Significantly prolonged latencies were associated with neurologic deficits. MEPs were not good predictors of neurologic recovery. The responses obtained from the side where the disc material was found were not different from those recorded from the opposite side. MEPs were very sensitive to lesions of the spinal cord, as indicated by the significant changes in the waves in patients with mild or no neurologic deficits and in the loss of response in dogs that still demonstrated purposeful movement. Neurologic exams provided more accurate diagnoses and prognoses than did MEPs in dogs with IVD disease.

The effect of dietary supplementation of fish oil on experimental myocardial infarction

The effect of altering the abundance of precursors and inhibitors of prostaglandin formation by dietary supplements of fish oil was investigated in dogs with experimentally induced myocardial infarction. Prior to induction, 10 male mongrel dogs were fed standard dog chow supplemented with 25% of the total calories as menhaden oil for 36 to 45 days. The fatty acid composition of the lipids in plasma and platelets changed to reflect the increased intake of polyunsaturated fatty acids of the n-3 type. Thrombosis and subsequent infarction was induced by electrical stimulation of the left circumflex coronary artery of ambulatory dogs that were monitored by telemetry. Upon stimulation of control animals, the frequency of ectopic beats rose from less than 10% at the beginning to about 80% after 19 hours. In contrast, the oil-fed dogs maintained a more normal ECG pattern, showing less than 30% ectopic beats after 19 hours. In these animals, the size of infarction (measured by formazan formation) was 3% of the left ventricle compared to 25% in the control animals. The results suggest that dietary supplementation with fish oil may be beneficial in reducing myocardial damage associated with coronary artery thrombosis.

Effects of isoproterenol infusion on myocardial structure and composition

Six ambulatory dogs had continuous infusion of isoproterenol, 1.5 μg per kilogram per hour for six days. The animals were put to death and the hearts excised and subdivided into five segments corresponding to the chambers and the interventricular septum. The myocardium was studied by light and electron microscopy and analyzed for one enzyme of the hexosemonophosphate shunt, seven enzymes of the glycolytic pathway, three enzymes of the Krebs cycle, total lipid, phospholipid, unesterified fatty acids, glycogen, total carbohydrate, catecholamines, sodium, and potassium. Twelve normal dogs served as controls. Myocardial structure and ultrastructure were unaltered except for depletion of glycogen granules. Compositional alterations were limited to glycogen depletion (control, 3.5, and treated, 0.2 mg. per gram) and increased activity of phosphoenolpyruvate kinase (control, 54.0, and treated, 73.9 μmoles per minute per gram of protein). Prolonged infusion of a small dose of isoproterenol is not associated with the myocardial necrosis and profound compositional alterations occurring after large doses of this amine.

Left ventricular function in ambulatory dogs during experimental Adams-Stokes seizures

Left ventricular pressure and diameter and aortic blood flow were recorded during asystole in ambulatory dogs with chronic complete heart block. Asystole occurred spontaneously, or was induced by acetylstrophanthidin or pacemaker withdrawal, and was frequently accompanied by convulsions (Adams-Stokes seizures). Left ventricular diameter reached maximal size within one second of asystole and did not increase further even though asystole lasted up to 30 seconds. The end-diastolic diameter following such prolonged asystole was thus practically identical to that recorded at idioventricular rates. In some instances in which asystole exceeded 10 seconds, forward blood flow pulses recorded by the aortic flowmeter were in synchrony with atrial contraction.

In vivo Pharmacodynamic Evaluation of Oral Dosage Forms by Whole Body Liquid Scintillometry

A large volume liquid scintillation detector was used to determine rates of excretion, absorption, and intercompartmental clearance in ambulatory dogs. A γ-emitting test substance was administered intravenously, orally in aqueous solution, and orally in sustained and delayed-release dosage forms. Unanesthetized female dogs were partially restricted, catheterized, and fasted prior to dosing. Where applicable, plots of log per cent whole body retention as a function of time were resolved into linear components following apparent first-order kinetics. The rate constants of these components were calculated and compared. Sustained-release forms were prepared which exhibited zero-order release characteristics in vitro and in vivo , and the characteristics of an enteric coated dosage form were compared after in vitro and in vivo testing. The procedure provided such parameters as absorption, excretion, release, and the effect of formulation techniques and formula variation on the biological availability of the test substance employed without the necessity of excreta and blood sampling and analysis.