Ventricular Arrhythmias in Dogs Undergoing Splenectomy: A Prospective Study

Fifty dogs undergoing splenectomy for splenic masses (n = 40), torsion of the splenic pedicle (n = 5), and immune-mediated disease (n = 5) were evaluated preoperatively and postoperatively for ventricular arrhythmias and the relationship between ventricular arrythmia and splenic disease. The ability of 1 -minute electrocardiograms recorded every 6 hours (ECGs/q6hr) to detect ventricular arrythmia was compared with continuous 48-hour Holter monitoring. Based on continuous Holter monitoring, splenectomized dogs had a high incidence (22 of 50) of rapid ventricular tachycardia. The incidence of rapid ventricular tachycardia was significantly higher in dogs with ruptured splenic masses (16 of 23) than without rupture (1 of 17) ( P < .001). When the results of ECG/q6hr were compared with the results of continuous Holter monitoring, ECG/q6hr was normal in 29% (4 of 14) of dogs with rapid ventricular tachycardia at > 3,000 ventricular extrasystoles (VE)/hr; 50% (4 of 8) of dogs with rapid ventricular tachycardia at 1,000 to 3,000 VE/hr and 100% (6 of 6) of dogs with 10 to 300 VE/hr without rapid ventricular tachycardia. Although dogs undergoing splenectomy had a high incidence of ventricular arrythmias, one-minute ECGs/q6h were unreliable for detection of ventricular arrythmias even when high-frequency extrasystoles occurred.     

Pharmacokinetic and tissue distribution study of oxytetracycline in rainbow trout following bolus intravenous administration

Oxytetracycline pharmacokinetics and tissue distribution were studied in rainbow trout following bolus i.v. administration at 5 mg/kg. The mean serum (log) drug concentration data were plotted against time (linear). The decay curve was described by a three-component exponential decay function and a three-compartment model. The t1/2 of rapid distribution was 0.9 h, the t1/2 of the slow distribution was 5.9 h and the t1/2 elimination was 81.5 h. Clearance was 25.4 ml/kg/h and Vd(area) 2988 ml/kg. Regression analysis of the serum levels for the three intervals, 0.5-2.0 h, 6.0-18.0 h, and 24-96 h, indicated that the rates of decay for each interval were 0.6151 h-1, 0.0564 h-1 and 0.0088 h-1 respectively. Rates of equilibration between tissues and serum were determined. Kidney equilibrated the fastest with t1/2 to equilibration of 1.1 h for H (anterior) kidney and 1.98 h for P (posterior) kidney. The highest drug levels were found in the liver and the lowest were in the brain.     

Remembrances of Jacques Jenny, DrMedVet 1917–1971

Editor's note : The holding of the 19th Annual Meeting of the American College of Veterinary Surgeons in Philadelphia in conjunction with the Centennial Celebration of the School of Veterinary Medicine of the University of Pennsylvania provides an opportunity for reflection. Dr. Jacques Jenny, Professor of Orthopedic Surgery at the School, was Chairman of the Organizing Committee that gave rise to the American College of Veterinary Surgeons on December 16,1965, and was elected as first President of the College. The solid foundation and high ideals that the Organizing Committee established are in large part responsible for the success of the College. Dr. Jenny died on November 20, 1971. Those of us fortunate to have known him personally realize the immense gap that his premature death left. For those that did not know him, I hope that this article permits some appreciation of the contributions of Dr. Jenny the comparative orthopedic surgeon, as well as of the very special human qualities of Jacques Jenny the man. The first author, Dr. Mark Allam, was Professor of Surgery and Dean of the School of Veterinary Medicine during most of Dr. Jenny's career at the University of Pennsylvania, and was the first Chairman of the Board of Regents of the American College of Veterinary Surgeons. The second author, Dr. David Nunamaker, is the first holder of the Jacques Jenny Professorship in Veterinary Orthopedics at the University of Pennsylvania.     

Resistance to DDT in the mosquito fish,Gambusia affinis

Mosquito fish from waters near cotton fields that have had a long history of treatment with chlorinated hydrocarbon pesticides exhibited a marked resistance to DDT compared with fish from areas which had had no past exposure to insecticides.     

THE VETMOUSETRAP™: A DEVICE FOR COMPUTED TOMOGRAPHIC IMAGING OF THE THORAX OF AWAKE CATS

The VetMousetrap^?, a novel device that allows computed tomography (CT) of awake cats and provides a clinically supportive environment, is described. Ten normal cats were used to test the device for ambient internal oxygen, carbon dioxide levels, and temperature. Twenty‐two awake normal cats were imaged using a 16‐multi‐slice helical CT unit to evaluate dose‐equivalent protocols. Two different X‐ray tube potentials (kV), 80 and 120, and two different helical pitches, 0.562 and 1.75, were evaluated. The signal intensity of the pulmonary parenchyma (SI_lung), signal intensity of background (SI_backgr), contrast, noise, signal‐to‐noise ratio (SNR), and contrast‐to‐noise ratio (CNR) were calculated. Three evaluators ranked the images for sharpness of liver margins, motion, helical, and windmill artifacts. CT was successfully completed in 20 of 22 cats. No artifacts directly related to the device were detected. Overall, 75 of 80 (94%) examinations were judged to have absent or minimal motion artifact. A statistically significant difference was found for SNR (P=0.001) and CNR (P=0.001) between all protocols. The higher pitch protocols had significantly lower noise and higher SNR and CNR, lower motion artifact but greater helical artifacts. A protocol using 80 kV, 130 mA, 0.5 s, and 0.562 pitch with 1.25 mm slice thickness, and 0.625 mm slice reconstruction interval is recommended. The VetMousetrap^? appears to provide the opportunity for diagnostic CT imaging of the thorax of awake cats.     

Biomechanical Analysis of Torsion and Shear Forces in Lumbar and Lumbosacral Spine Segments of Nonchondrodystrophic Dogs

Objective— To determine stiffness and load–displacement curves as a biomechanical response to applied torsion and shear forces in cadaveric canine lumbar and lumbosacral specimens.
Study Design— Biomechanical study.
Animals— Caudal lumbar and lumbosacral functional spine units (FSU) of nonchondrodystrophic large-breed dogs (n=31) with radiographically normal spines.
Methods— FSU from dogs without musculoskeletal disease were tested in torsion in a custom-built spine loading simulator with 6 degrees of freedom, which uses orthogonally mounted electric motors to apply pure axial rotation. For shear tests, specimens were mounted to a custom-made shear-testing device, driven by a servo hydraulic testing machine. Load–displacement curves were recorded for torsion and shear.
Results— Left and right torsion stiffness was not different within each FSU level; however, torsional stiffness of L7-S1 was significantly smaller compared with lumbar FSU (L4-5–L6-7).
Ventral/dorsal stiffness was significantly different from lateral stiffness within an individual FSU level for L5-6, L6-7, and L7-S1 but not for L4-5. When the data from 4 tested shear directions from the same specimen were pooled, level L5-6 was significantly stiffer than L7-S1.
Conclusions— Increased range of motion of the lumbosacral joint is reflected by an overall decreased shear and rotational stiffness at the lumbosacral FSU.
Clinical Relevance— Data from dogs with disc degeneration have to be collected, analyzed, and compared with results from our chondrodystrophic large-breed dogs with radiographically normal spines.     

Explaining patterns of species dominance in the shrub steppe systems of the Junggar Basin （China） and Great Basin （USA）

Natural scientists have long recognized that regions with similar climate tend to have similar vegetation.Preliminary observations suggest that shrub steppe communities of the western US and western China may be two such regions with similar annual precipitation,temperature,land use,and vegetation.These cold dry shrub steppes have traditionally been grazed.Despite these similarities,patterns of species dominance are different.Annual species that are rare in China become dominant when introduced to the United States.The objective of this study was to investigate how climate,land use and community structure may explain these patterns of species dominance.Community structure and grazing intensity were measured at 5 sites in each region.This information was combined with a broader review of the literature describing the history of grazing in both basins.Climate was analyzed based on a spatially-gridded,interpolated weather time series(monthly records) and climatological summary(1961-1990 mean conditions) data set from the Climate Research Unit.We found that differences in summer precipitation and winter minimum temperature,land use intensity,and shrub size may all contribute to the dominance of annual species in the Great Basin,particularly Bromus tectorum.In particular,previous work indicates that summer precipitation and winter temperature drive the distribution of Bromus tectorum in the Great Basin.As a result,sites with wet summers and cold springs,similar to the Chinese sites,would not be expected to be dominated by Bromus tectorum.A history of more intense grazing of the Chinese sites,as described in the literature,also is likely to decrease fire frequency,and decreases litter and shrub dominance,all of which have been demonstrated to be important in Bromus tectorum establishment and ultimate dominance.Further research is necessary to determine if other annuals that follow the same pattern of scarcity in the Junggar Basin and dominance in the Great Basin are responding to the same influences.     

Observation on the presence of spermatozoa in canine urine

Urine samples were collected from 32 male dogs and examined for the presence of spermatozoa. Twenty-eight dogs were found to have spermatozoa in their urine, indicating that spermatogenesis is occurring normally.     

Lameness Associated with Coxofemoral Soft Tissue Masses in Six Dogs

Six cases of mechanical lameness involving the coxofemoral joint are presented. All dogs had a history of chronic rear leg pain and lameness, and decreased range of motion of the hip. On physical examination, ventral subluxation of the coxofemoral joint during extension was present in three dogs. A radiographic diagnosis of subluxation was made in five dogs. In each dog, surgical exploration of the area caudal to the coxofemoral joint revealed a fibrous mass between the lesser or third trochanters and the ischium, diagnosed as a nonneoplastic fibrous reaction by microscopic examination. The clinical, radiographic, and histopathologic signs were similar to previously described cases of myositis ossificans. Five dogs returned to normal function after excision of the soft tissue mass, and one dog was normal when lost to follow-up 4 weeks postoperatively.