Epidemiological aspects of proliferative kidney disease amongst rainbow trout Salmo gairdneri Richardson in Northern Ireland

Abstract. The epidemiology of PKD is described as it relates to one affected farm in Northern Ireland. From 1972–1976 stocking and management practices led to mortality of 10–15% amongst the 0+fish. 1+or older fish were never affected. In 1977 and 1978, however, delaying the stocking of the farm until July eliminated deaths in the 0+fish, and mortality in these 1977-moved fish the subsequent year remained at an absolute minimum. Preliminary observations suggest that a means of controlling the disease has been found.
Experimental work demonstrates that the resistance of 1 +or older fish is due to previous exposure and is not an age-related immunity. Experimental work also suggests the presence of an incubation period of 6–7 weeks and that the peak time of infectivity is probably around May. None of the evidence detracts from the possibility that an infectious agent is involved although an attempt to transmit the disease failed.     

Effect of Distal Femoral Growth Plate Fusion on Femoral-Tibial Length

Unilateral distal femoral epiphysiodesis in seven 10 week old crossbred Doberman Pinscher littermates resulted in a significant (p less than or equal to 0.0001) femoral length deficit of 23.5% without clinically detectable alterations in gait up to 42 weeks after surgery. In addition to compensatory hyperextension of the stifle joint, the ipsilateral tibia showed significant (p less than or equal to 0.0001) acceleration in longitudinal growth. The combined femoral-tibial length at necropsy was still significantly shorter (p less than or equal to 0.0001) in the treated leg than in the control leg despite the increased tibial growth. Unlike other species, neither of the other two femoral growth plates produced any significant compensatory increase in length after fusion of the distal growth plate. The femoral condyles of the treated legs rotated caudally and degenerative joint disease developed in all stifle joints of the treated legs. No contralateral limb abnormalities were evident radiographically.     

Some observations on the dilution, cooling and freezing of canine semen

Canine semen was obtained by digital manipulation from two donor dogs and twelve stud dogs. The sperm-rich fraction was diluted with either of two different diluents and the survival of spermatozoa before and after freezing was determined. It appeared that there was no difference in the post-thaw survival rate in either of the diluents used.     

Histological effects of the inert suspended clay kaolin on the gills of juvenile rainbow trout, Salmo gairdneri Richardson

Abstract. Juvenile rainbow trout were exposed to 36, 171, 1017 and 4887 mg/1 of suspended kaolin clay for 64 days. Gills were analysed qualitatively and quantitatively using histology. Branchial pathology was absent at all sample times in fish exposed to 36, 171 and 1017 mg/1 kaolin, although intracellular kaolin was visible within filament and lamellar epithelium in gills exposed to 171, 1017 and 4887 mg/1 kaolin at 4, 8, 16, 32 and 64 days. Lesions were found in gills exposed to 4887 mg/1 kaolin at 16 and 32 days but the marked lamellar proliferation was associated with moderate to large numbers of protozoa identified as Ichthyobodo necator . Gills regained normal architecture by 64 days despite continued exposure to kaolin. It is suggested that while the gill lesions were probably a direct result of protozoan infection, kaolin was indirectly responsible for creating a favourable environment for protozoan colonization. The recovery of normal architecture and reduction of protozoan numbers between 32 and 64 days was probably a function of increased mucus secretion, immune response and turnover of branchial epithelium. The authors conclude that exposure to prevailing levels of this inert clay particle, even for periods as long as 64 days, probably has little direct effect on gill structure at the light microscope level. The action of non-inert and organic particles remains to be investigated.     

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.     

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.     

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.