Fig. 4

Histoarchitecture of the hypothalamus. Visualized at low magnification stained by hematoxylin and eosin and at high magnification immunostained for CD11b and CD45 in PCV-PEEP2, PSV-PEEP2, PCV-PEEP5, and PSV-PEEP5. PCV-PEEP2 and PCV-PEEP5 exhibiting necrosis (*) and hemorrhage (#) in the hippocampus distorting the curved histoarchitecture (a, lateral) of the pyramidal cells band encircling the dentate gyrus (b, lateral) and obstructing the choroid plexus. At high magnification, numerous CD11b + mononuclear phagocytes visualized in microglia (thin arrows) adjacent to the dentate gyrus (DG) of hippocampus parenchyma, and numerous CD45 + cells in the choroid plexus (CP, thick arrows), representing mainly myeloid-derived macrophages that reside at the interfaces of the brain and periphery. Compared with the PCV-PEEP5 group, the number of microglia and CD11b + myeloid cells, as well as choroid plexus CD45 +, was more abundant in the PCV-PEEP2 group in the three brain compartments of the hippocampus parenchyma including the DG, pyramidal neurons, and CP (arrows). Note the intense edema of the neuropils (NP) in the PCV group. PSV-PEEP2 and PSV-PEEP5 showing preserved hippocampus histoarchitecture as a multiply curved structure (a, middle, bottom) with pyramidal cells forming a band that circles the denser line of small cells comprising the DG (b, top) and CP (c, center). At high magnification, CD11b + cells comprised mononuclear phagocytes, which were divided further into two populations: CD11b + cells characterized by microglia (thin arrows) that reside in the DG of hippocampus parenchyma, and CD45 + cells that reside in the CP (thick arrows). They represented mainly myeloid-derived macrophages that reside at the interfaces of the brain and periphery. Compared with the PSV-PEEP5 group, the numbers of microglia and CD11b + myeloid cells, as well as Cp CD45 +, were more prominent in the PCV-P2 group in the three brain compartments of the hippocampus parenchyma, including the DG, pyramidal neurons and CP. PCV, pressure-controlled ventilation; PEEP, positive end-expiratory pressure; PSV, pressure-support ventilation