High Resolution Helium Ion Scanning Microscopy of the Rat Kidney
(A) Lower magnification showing GA-fixed proximal tubule (dehydrated using the extended methanol freeze-substitution protocol) and its extensive brush border (BB). Bar = 5 µm. (B) shows a lateral section of modified PLP-fixed proximal tubule dehydrated as in (A), demonstrating the apical brush border (BB) and the extensive basolateral plasma membrane infoldings and invaginations (arrows) that are characteristic of the S1 segment of the proximal tubule. Bar = 1 µm. (C) shows the tightly packed, slender brush border microvilli in greater detail (GA fixation, extended methanol freeze-substitution dehydration protocol). Bar = 0.5 µm. (D) Brush border microvilli at high magnification showing that their surface membrane has numerous micropits of unknown significance (arrows). Bar = 100 nm. Similar regions from the same kidney were also imaged by conventional SEM after coating using the in-lens detector and are shown at lower (E, bar = 0.5 µm) and higher magnification (F, bar = 100 nm). The conventional images have considerable less clarity and surface detail than the HIM-imaged brush border region.