Effect of oxidized fish oil, vitamin E and ethoxyquin on the histopathology and haematology of rainbow trout, Salmo gairdneri Richardson

Abstract. Rainbow trout were fed for 24 weeks on practical diets containing varying concentrations of oxidized fish oil, with or without supplementation of vitamin E and ethoxyquin. Serum biochemistry, haematology and histopathology were investigated to measure the relative protection offered by vitamin E (DL–α–toco–pherol acetate) and/or a synthetic substitute (ethoxyquin), against highly or extremely oxidized oil with peroxide values of 120 or 314mEq/kg oil respectively. Groups fed highly or extremely oxidized oils without DL–α–tocopherol acetate supplementation, and with or without supplemental ethoxyquin, exhibited lower red blood cell numbers, haemoglobin content, haematocrit, and increased haemolysis. In addition, fish from these groups had increased, abnormally developing polychromatocytes, splenic haemosiderosis and hepatic ceroidosis. The results indicate that vitamin E protects better and at lower concentrations than does ethoxyquin, and that supplementation with 33 mg of DL–α–tocopherol acetate/kg is adequate to prevent vitamin E deficiency signs when feeding practical diets containing 7.5 % of a highly oxidized oil. Supplementation with ethoxyquin alone to diets containing highly oxidized oil appeared to exert partial protection, but did not increase the level of protection when added simultaneously with DL–α–tocopherol acetate. The data support the theory of a general antioxidant function for vitamin E, and suggest that mortalities ensuing from vitamin E deficiency are due to the cumulative effects of liver dysfunction and anaemia.     

Pathology of bacterial gill disease: sequential development of lesions during natural outbreaks of disease

Abstract. This study examines the sequential pattern of bacterial colonization and the sequential development of branchial lesions during typical outbreaks of bacterial gill disease (BGD) among four groups of commercially reared rainbow trout fingerlings, Oncorhynchus mykiss (Richardson). During a 5-month monitoring regime, prior to the onset of natural outbreaks of BGD, gill morphology of examined fish remained unaltered. Bacterial colonization of the gills was immediately preceded by several gill changes which were widely present in fish from all groups under study. These changes, which were detectable at the ultrastructural level only, included cytoplasmic blistering and degeneration of the microridges of the superficial filament epithelium, in addition to slight topographical irregularity of the filament tips suggestive of mild hyperplasia. Bacterial colonization began at these altered filament tips before spreading to more proximal regions of the filament and adjacent lamellar surfaces. Explosive increases in proportional morbidity and mortality coincided with the development of the following gill lesions: extensive bacterial colonization of lamellar surfaces, lamellar epithelial hydropic degeneration and necrosis, and lamellar oedema. In contrast, gill lesions such as lamellar fusion, epithelial hyperplasia and various metaplastic responses were detected later either as subacute (3–5 days) or chronic (7–14 days) changes. The role of epithelial necrosis as an important event during BGD is discussed as a possible mechanism leading to the development of sub-acute and chronic gill lesions.     

Proliferative kidney disease: first reported outbreak in North America

Abstract. Proliferative kidney disease (PKD) was diagnosed in rainbow trout, Salmo gairdneri Richardson, at the Hagerman, Idaho, State Fish Hatchery. Wild fish from Riley Creek, one of the hatchery water supplies, were infected with PKD organisms. Clinical signs, gross pathology and histopathology of affected fish were typical of those reported for PKD in salmonids from European hatcheries. In addition to lesions normally seen, we observed a severe vasculitis and occlusion of renal and hepatic vessels. Ultrastructure of the PKD organism and possible inclusion body production sites are described. The disease outbreak was complicated by the presence of other infectious diseases. This is the first recorded outbreak of PKD in North America.     

Histopathology and prevalence of epidermal papillomas epidemic in brown bullhead, Ictalurus nebulosus (Lesueur), and white sucker, Catostomus commersoni (Lacépède), populations from Ontario, Canada

Abstract. White sucker, Catostomus commersoni (Lacépède), and brown bullhead, Ictalurus nebulosus (Lesueur), populations throughout the Great Lakes examined for evidence of pollution associated neoplasia exhibited a variety of morphologically distinct skin lesions. Three types of skin lesions affected white suckers: (a) focal on the lips, (b) discrete on the body, or (c) raised mucoid focal lesions on the skin and fins. Histologically, all three types featured a continuum between mild epidermal hyperplasia and benign papillomata. Brown bullheads exhibited a single variably shaped raised lesion on all body surfaces and within the oral cavity in addition to focal lip lesions. All bullhead lesions exhibited a continuum between mild epithelial hyperplasia and papillomata. Some skin lesions in both species were invasive but most abnormalities represented some stage in the development of epidermal papillomas. These papillomas superficially resemble papillomas common in many fish species and which are associated with viruses, but sucker and bullhead papillomas exhibit a unique range of histopathological and gross morphological appearances. The high prevalence of these papillomas, affecting up to 60% of some populations in polluted areas, supports the possibility that carcinogenic chemicals in the sediments are influencing papilloma development.     

Single-dose pharmacokinetics of cefazolin in bovine synovial fluid after intravenous regional injection

Gagnon, H., Ferguson, J.G., Papich, M.G., Bailey, J.V. Single-dose pharmacokinetics of cefazolin in bovine synovial fluid after intravenous regional injection. J. vet. Pharmacol. Therap. 17, 31–37.
The pharmacokinetic properties of cefazolin in the synovial fluid of the tibiotarsal joint were determined in 10 healthy mature cattle after intravenous regional injection of 2 50 mg cefazolin. A pneumatic tourniquet was positioned proximal to the tibiotarsal joint and the intravenous injection was performed distal to the tourniquet. Synovial fluid concentrations of cefazolin increased in the first 30 mm and fluctuated between 54.7 ± 11.0 g/ml (mean ± SEM) and 73.2 ± 13.2 g/ml in the following 90 min while the tourniquet remained inflated. After tourniquet removal, synovial fluid concentration-time curves followed first-order one-compartment model decay in most of the animals with an elimination half-life of 0.82 h (harmonic mean). Therapeutic concentrations of cefazolin in the synovial fluid of normal joints were reached and this injection technique could be used as an alternative to systemic administration of antibiotics to provide adequate concentrations in a localized area.     

Surface Deformation and Lower Crustal Flow in Eastern Tibet

Field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern Tibetan plateau since about 4 million years ago. Instead, central eastern Tibet has been nearly stationary relative to southeastern China, southeastern Tibet has rotated clockwise without major crustal shortening, and the crust along portions of the eastern plateau margin has been extended. Modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle. This model also predicts east-west extension on the high plateau without convective removal of Tibetan lithosphere and without eastward movement of the crust east of the plateau.     

Estimating the mass of asteroid 253 mathilde from tracking data during the NEAR flyby

The terminal navigation of the Near Earth Asteroid Rendezvous (NEAR) spacecraft during its close flyby of asteroid 253 Mathilde involved coordinated efforts to determine the heliocentric orbits of the spacecraft and Mathilde and then to determine the relative trajectory of the spacecraft with respect to Mathilde. The gravitational perturbation of Mathilde on the passing spacecraft was apparent in the spacecraft tracking data. As a result of the accurate targeting achieved, these data could be used to determine Mathilde's mass as 1.033 (+/- 0.044) x 10(20) grams. Coupled with a volume estimate provided by the NEAR imaging team, this mass suggests a low bulk density for Mathilde of 1.3 grams per cubic centimeter.