Ototoxic potential of gentamicin in ponies.

Ototoxicosis was evaluated in 6 healthy ponies given 5 mg of gentamicin/kg of body weight, q 8 h, IM. Ponies 1, 2, and 3 were dosed for 7 days and ponies 4, 5, and 6 were dosed for 14 days. Serum peak and trough concentrations of gentamicin were measured by radioimmunoassay at regular intervals. Brain stem auditory-evoked responses were recorded every 5 days up to 60 days after the first dose to monitor auditory function. Although serum gentamicin concentrations were within or above the accepted clinical therapeutic range, loss of auditory function was not observed at the frequency range (1 to 4 kHz) tested. Serum chemical values remained within the accepted clinical range and no evidence of nephrotoxicosis was observed. Seemingly, gentamicin given IM to healthy ponies was safe and had minimal risk of side effects.

A comparison of interactive videodisc instruction with live animal laboratories.

This study compared interactive videodisc-simulated laboratories with two types of traditional labs: a traditional general cardiovascular physiology participation lab and a traditional fibrillation/positive pressure ventilation demonstration lab. The two laboratory sections (a total of 85 first-year veterinary medical students) were divided into 12 lab groups of 3-4 students per lab section. These groups were randomly assigned to either a traditional live animal laboratory or an interactive videodisc-simulated laboratory to compare the effectiveness and efficiency of these methods in teaching physiology. A 22-item, multiple-choice/short answer test was given to all students after the laboratories. In both the participation and the demonstration laboratories, there were no significant differences between group test scores of the interactive videodisc groups and the live animal laboratory groups, but there were differences in time spent by both students and instructors. It was concluded that the interactive videodisc-simulated lab was as effective as the traditional live-animal labs and was more time efficient than the traditional participation lab.

De subitaneis mortibus. XV. Hereditary stenosis of the His bundle in Pug dogs.

Syncope and sudden death occurs in certain purebred Pug dogs which have been found to have intermittent sinus pauses and paroxysmal second degree heart block on electrocardiographic (ECG) study. We have established a colony of such dogs to study this problem and here report the results of histological examination of the cardiac conduction system in twenty-one of them. These include a dam which may be considered the proband, three of her offspring (two littermates) and three fetal pups in an unborn litter of one of these; three of the four adult dogs died suddenly and unexpectedly. Two groups of puppies descendants of these lines were also studied after they all died within three days of birth. The first group of puppies (8) did not have suitable ECG studies but the second group (6) did and showed ECG changes similar to those in the adult dogs. In all 21 dogs the sinus node was anatomically normal, but in every one there was significant stenosis of the midportion of the His bundle. There was no abnormality of the atrioventricular (A-V) node or of the bundle branches, and the cardiac valves and coronary arteries were normal. Two pups had ventricular septal defects and one of these had an atrial defect as well. All the dogs were of the normal fawn color, had a normal physical appearance and no visible evidence of associated extracardiac abnormalities. The adult dogs were able to hear normally but the puppies died too early to test their hearing. The paroxysmal heart block may in part be attributable to the abnormality in the His bundle, but other factors possibly leading to heart block and long sinus pauses are discussed. Stenosis of the midportion of the His bundle appears to be a heritable trait in these purebred Pug dogs.

Frequency of second-degree atrioventricular heart blocks in dogs.

Clinically normal adult dogs and pups 8 to 24 weeks of age were monitored for 2nd-degree atrioventricular (AV) heart block. Radiotelemetry was used to obtain the electrocardiogram (ECG) of resting, unanesthetized, unrestrained dogs. Second-degree AV heart block was detected in 64% of 11 adult dogs and 100% of 12 pups between 8 and 11 weeks of age. The dropped beats, prolonged P-R intervals, and prolonged P-P intervals appeared to be associated with the respiratory cycle. Atropine quickly reduced the frequence of dropped beats. It was concluded that occasional dropped ventricular beats due to 2nd-degree AV heart block may be normal in dogs, especially young dogs.