Progressive myelin degradation in the cerebral WM of TgPAC-Notch3
mice. (A-B) Representative sections of corpus callosum sections from a control (A) and a TgPAC-Notch3R169C
(B) immunolabeled with SMI94, which stains normal and degraded myelin; the TgPAC-Notch3R169C displays numerous hyperintense foci (white arrows). (C) Image processing used to automatically identify the hyperintense foci. (Left panel) Shown is a 8-bit image of a TgPAC-Notch3R169C corpus callosum section immunostained with SMI94. (Middle panel) Shown is the corresponding 3D image intensity profile with a LUT scale displaying the non-uniform background of the image that impedes accurate detection of hyperintense foci using simple thresholding. (Right panel) The local maxima in the image are determined to overcome this limitation: maxima are ignored if they do not stand out from the surroundings by more than a noise tolerance value (this value is set initially, from a batch of randomly selected images, to allow best discrimination of foci from background). (D-E) Diagrams of the myelin debris density in the corpus callosum, expressed as a total number of debris over a given area (number/mm2), in control and mutant mice at 12 months of age (D) (n = 4 TgPAC-Notch3R169C and 4 control mice) and 20 months of age (E) (n = 5 TgPAC-Notch3R169C and 8 control mice). Notice that the scale is different between E and D. Scale bar represents 50 μm (A-B).