The effects of gill abrasion and experimental infection with Tenacibaculum maritimum were assessed in Atlantic salmon Salmo salar with underlying amoebic gill disease. The respiratory and acid-base parameters arterial oxygen tension (P a O 2 ), arterial whole blood oxygen content (C a O 2 ), arterial pH (pH a ), haematocrit and haemoglobin concentrations were measured at intervals over a 48 h recovery period following surgical cannulation of the dorsal aorta. Mortality rates over the recovery period were variable, with gill abrasion and inoculation with T. maritimum causing the highest initial mortality rate and unabraded, uninoculated controls showing the lowest overall mortality rate. Fish with abraded gills tended to show reduced P a O 2 and lower C a O 2 compared with unabraded fish. Infection with T. maritimum had no effect on P a O 2 or C a O 2 . All fish showed an initial alkalosis at 24 h post-surgery/inoculation which was more pronounced in fish inoculated with T. maritimum. There were no significant effects of gill abrasion or infection upon the ratio of oxygen specifically bound to haemoglobin or mean cellular haemoglobin concentration. Histologically, 48 h following surgery, abraded gills showed multifocal hyperplastic lesions with pronounced branchial congestion and telangiectasis, and those inoculated with T. maritimum exhibited focal areas of branchial necrosis and erosion associated with filamentous bacterial mats. All fish examined showed signs of amoebic gill disease with multifocal hyperplastic and spongious lesions with parasome-containing amoeba associated with the gill epithelium. The results suggest that respiratory compromise occurred as a consequence of gill abrasion rather than infection with T. maritimum.
The effect of diabetes mellitus vs the effect of the Ren2 gene on the glomerular pathology of (mREN-2)27 heterozygous male rats is controversial. As discrete diabetes-induced glomerular lesions may have been overlooked, we performed a detailed morphometric analysis of glomeruli in diabetic and non-diabetic heterozygous male (mREN-2)27 rats and their normotensive (non-diabetic and diabetic Sprague-Dawley) controls. Glomeruli were scored by light microscopy for nine discrete histological parameters, some of which were graded for extent and/or severity. Mesangiolysis, segmental hypocellularity, and severe tuft-to-capsule adhesions were specific to diabetes; severe mesangial matrix expansion, glomerulosclerosis, thickening of Bowman's capsule, and dilatation of the urinary space were specific to the Ren2 gene. Hyalinosis and hypercellularity were associated with both diabetes and the Ren2 gene: the effect was additive for hyalinosis and synergistic for hypercellularity. The histological parameters were then combined with two physiological indices (systolic blood pressure and proteinuria) and principle components analysis (PCA) was used to detect correlations between the variables. Four discrete patterns of pathology were identified; three were statistically associated with diabetes and/or the Ren2 gene. These findings suggest that both diabetes and the Ren2 gene make significant, albeit different, contributions to the glomerular pathology of diabetic heterozygous male (mREN-2)27 rats. Despite defining the contribution of diabetes, our work does not support the (mREN-2)27 rat as a model of diabetic nephropathy (DN). Rather, it suggests that these animals remain useful for investigating a particular and limited constellation of DN features. There are numerous rodent models of human diabetic nephropathy (DN), attesting to the uncertainty associated with many of them. 1,2 Streptozotocin (STZ), which induces hyperglycemia by selectively damaging pancreatic b cells, has been administered to genetically modified rodents to create a variety of DN models. [3][4][5][6] The validity of one of these models, the diabetic (mREN-2)27 rat, has been questioned because of the apparent overwhelming impact of its genetically mediated hypertension on renal pathology. 7 One group of investigators reported that STZ-induced diabetes in female heterozygous (mREN-2)27 rats recapitulates the proteinuria, nodular glomerulosclerosis, and progressive loss of renal function that are cardinal features of DN in human beings. 6 However, other investigators suggest that the survival and kidney pathology of male heterozygotes is determined more by hypertension than by diabetes, as the presence of diabetes in these animals seemed to exert little phenotypic effect. 7 A sexual dimorphism in hypertension is apparent from the lower blood pressure of female vs male (mREN-2)27 rats. 8 This dimorphism has been proposed to underlie the apparent gender-dependent variation in experimental outcome because the effects of diabetes might only be observed in kidneys ...
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