Sepsis is defined as systemic inflammatory response syndrome that occurs during infection. Although it is a major cause of mortality in fish, no shortage of literature on the pathophysiology of sepsis in teleosts. Thus, this study aims to assess and characterize the pathophysiological and histological changes of sepsis, identifying and quantifying gene expression of tumor necrosis factor ± and interleukin 1 in sepsis induced by Aeromonas hydrophila in pacu, and acute inflammation in the bladder under the influence of sepsis. For this, 260 will be used pacu, Piaractus mesopotamicus, with average weight of 150.71 ± 26.73 g and mean total length of 15.27 ± 1.60 cm. Initially it will be done to standardize the inoculum by determination of bacterial concentration lethal to 50.0% of the fish (LC50). Sepsis is induced by administration of the inoculum intracelomática corresponding to LC50 of A. hydrophila. The animals will be divided into two groups, one will receive 0.5 ml of NaCl solution (control group) and another group received the same volume containing the inoculum (challenge group) in a completely randomized design. Previously, half, one and two hours after inoculation the blood profile will be characterized, biochemical and coagulation of the host. For the characterization of histopathological changes, fragments of liver, spleen, kidney, heart and gills will be collected at the end of the age six, 12, 24 and 48 hours after induction of sepsis. The determination of gene expression of tumor necrosis factor (TNF-±) and interleukin 1 (IL-1) will occur 24 hours after induction of sepsis, the method reverse transcription-polymerase chain reaction (PCR) in real time. Immediately after induction of sepsis will be injected into the bladder with the inflammatory stimulus thioglycolate to 6% in saline 0.65% and after six, 12, 24 and 48 hours after stimulation, the exudate will be collected for the total count and differential cells accumulated in the bladder. Bacteria will be quantified in the blood in the exudate. Throughout the experiment the animals will be evaluated for clinical changes and the mortality rate will be assessed during the infection period for a maximum period of 10 days of observation. The results will be compared using analysis of variance (ANOVA) at 5% probability and the difference between the averages will be compared by Tukey test.
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