glycogen and Enterobacteriaceae-Infections

Dietary compromises, especially food restrictions, possess species-specific effects on the health status and infection control in several organisms, including fish. To understand the starvation-mediated physiological responses in Edwardsiella tarda infected red sea bream, especially in the liver, we performed a 20-day starvation experiment using 4 treatment (2 fed and 2 starved) groups, namely, fed-placebo, starved-placebo, fed-infected, and starved-infected, wherein bacterial exposure was done on the 11th day. In the present study, the starved groups showed reduced hepatosomatic index and drastic depletion in glycogen storage and vacuole formation. The fed-infected fish showed significant (P<0.05) increase in catalase and superoxide dismutase activity in relation to its starved equivalent. Significant (P<0.05) alteration in glucose and energy metabolism, as evident from hexokinase and glucose-6-phosphate dehydrogenase activity, was recorded in the starved groups. Interestingly, coinciding with the liver histology, PPAR (peroxisome proliferator activated receptors) α transcription followed a time-dependent activation in starved groups while PPARγ exhibited an opposite pattern. The transcription of hepcidin 1 and transferrin, initially increased in 0dai (days after infection) starved fish but reduced significantly (P<0.05) at later stages. Two-color immunohistochemistry and subsequent cell counting showed significant increase in P63-positive cells at 0dai and 5dai but later reduced slightly at 10dai. Similar results were also obtained in the lysosomal (cathepsin D) and non-lysosomal (ubiquitin) gene transcription level. All together, our data suggest that starvation exerts multidirectional responses, which allows for better physiological adaptations during any infectious period, in red sea bream.

Topics: Animals; Catalase; Edwardsiella tarda; Energy Metabolism; Enterobacteriaceae Infections; Fish Diseases; Fish Proteins; Food; Gene Expression; Glucose; Glycogen; Host-Pathogen Interactions; Liver; PPAR alpha; PPAR gamma; Reverse Transcriptase Polymerase Chain Reaction; Sea Bream; Starvation; Superoxide Dismutase; Vacuoles

To study the direct cause of liver enlargement in the Japanese flounder Paralichthys olivaceus infected with Edwardsiella tarda, the fish were challenged with E. tarda and reared without feeding. The liver of fish exposed to the bacteria was markedly enlarged compared to that of the controls while no severe histopathological change appeared in the organ during the experiments. No notable difference was observed in the crude fat, glycogen, and water content of the liver between challenged and control fish. The size of liver cells and nuclei of the challenged fish was apparently larger than that of the controls. Analysis of crude DNA in the liver suggested that the number of liver cells of starved control fish significantly decreased during the experiment while that of the challenged fish was maintained at a level of the initial control. RNA/DNA ratio of the liver of challenged fish clearly increased while it decreased in the control fish during the experiment. These observations suggest that liver enlargement of flounder infected with E. tarda, at least in the early stage of infection, is not a result of any readily observable histopathological changes and that E. tarda infection causes hypertrophy of the cells, as well as preventing decrease in liver cell number.

Topics: Animals; Blood Glucose; DNA, Bacterial; Edwardsiella tarda; Electrophoresis, Polyacrylamide Gel; Enterobacteriaceae Infections; Fish Diseases; Flatfishes; Glycogen; Hypertrophy; Image Processing, Computer-Assisted; Kidney; Liver; Organ Size; RNA, Bacterial; Seawater; Water