Effect Of The Main Mucosal Immunity Organization And Cell In Largemouth Bass Under Acute Hypoxic Exposure

In this study with routine paraffin section and HE,AB-PAS,toluidine blue and immunohistochemical staining,the histological structure of main mucosal immune system were observedin largemouth bsas(Micropterus Samoides).We hope our study can provide a valuable basis for further elucidation of fish immunology.The results showed that the digestive tract were composed of oral-pharyngeal cavity,esophagus,stomach,pyloric caeca and intestine.The wall of digestive tract can be divided into mucosal layer,submucosal layer,muscular layer and outer membrane.The characteristics of mucous epithelium,mucous cells and index of digestive tract had differences in different positions.From the front to the rear section,the diameter of pyloric caeca and intestine and number of duplicatures in pyloric caeca decrease significantly(P<0.05).The gills were composed of gill arch,gill raker and gill filament.Every part of gill was composed of epithelial cells,cartilage and connective tissue,and taste buds were abundant in gill arch and gill raker’s epithelial.The skin were composed of epidermis and dermis.Thickness of dermis in different parts showed different.Side skin was thicker than tail skin,and goblet cells were distributed in lateral skin.Four types mucous cells were distributed in digestive tract,gill and skin.Main type and numbers in different parts showed different.Type Ⅲ mucous cells were the most in the esophagus and foregut;type Ⅳ mucous cells were the most in the oral-pharyngeal cavity,midgut,hindgut,gill filament and and gill raker;type Ⅱ mucous cells were the most in the gill arch,lateral skin and tail skin;only type Ⅰ mucous cells in stomach specially.The maximum total density of mucous cells were an average of 145.72 cell/mm2 in or-opharyngeal cavity and esophagus of digestive tract.The density of mucous cells in gill arch and gill raker were larger than 3.85 times than those in gill filament.The density of mucous cells in the tail skin was significantly higher than those in the lateral skin.Mast cells,trypsin,5-HT,Gas and Glu were distributed in each segment of the intestine(except hindgut.).Besides,5-HT and Gas were distributed in gill filament,and related to the other endocrine cells above were not distributed in the skin and gills.No Som immunohistochemistry reaction were negative in the whole intestine,gill and skin.The largest density section of mast cells was midgut(520.00cell/nm2),andthe largest density section of Glu was foregut(11.90 cell/mm2).From foregut to hindgut,the density of Try and Gas immuopositive cells significantly decrease(P<0.05),5-HT immuopositive cells gradually incresased(P<0.05)..Hypoxic at different time(0h、6h、12h、24h)had different effects on the histological structure of intestinal tract,gill and skin after the low oxygen.The result showed that the numbers of duplicatures in midgut and the height of duplicatures in midgut and hindgut were increased at first and then decreased afterhypoxic.The numbers and height of duplicatures reached a maximum value andhad significantly increase after 12h in low oxygen(P<0.05).Hypoxia can causea large number of blood cells brimmingin middle part of gill filament(12h).The epithelial cells of gill lamellaehad a disorderedarrangement,and distinctionsof the pillar cells and blood cellsbecame pretty muddied after 24h under low oxygen.No damage of skin had been found after hypoxia.After low oxygen treatment,the types of mucous cell in intestinal tract,gill and skin had no difference,the density of mucous cells appeared a degree of difference.After low oxygen 12h,type Ⅰ mucous cells of foregut and midgut,type Ⅲ mucous cells of gill raker all significantly decreased(P<0.05).It was found that the density of type Ⅰ mucous cells in gill filament and typeⅢ mucous cells in tail skin significantly increased after 24 h hypoxic exposure(P<0.05).The density of mast cells,5-HT,Gass,Glus and tryptase were changed with time and there were different regularity in foregut,midgut,hindgut and gill.After 24 h hypoxic exposure,the density were increased of 5-HT in midgut and gill filament,Gas in forgut and gill filament,and Glu in hindgut(P<0.05).Compared with each group the density of 5-HT significantly increased in other time points(P<0.05).Although the density of Glu decreased significantly(P<0.05)after 24 h hypoxic exposure.Total density of mast cells in midgut and hindgutdecreased firstly and increased subsequently conpared tothe contrast after 24 h hypoxic exposure.After 6 h in low oxygen,the content of tryptase only in the midgut significantly decreased,compared with each groups(P<0.05),however,the content of tryptase of the midgut in other time points showed no difference.