Cryosections of the tissues were cut in a cryo-microtome (Leica CM1900-UV) at a thickness of 10 μm and transferred onto conductive indium-tin-oxide-coated glass slides (Bruker Daltonik, Bremen, Germany). The sections were vacuum-dried in a desiccator for approximately 15 min then washed two times in 70% ethanol and once in 96% ethanol for 1 min each. The sections were then dried and stored under vacuum until the matrix was applied.
The sections were coated with matrix using an ImagePrep (Bruker Daltonik) according to the manufacturer's standard protocols. The brain and testis samples were coated with α-cyano-4-hydroxy-cinnamic acid (Bruker Daltonik), while the pancreas sample was coated with sinapinic acid (Bruker Daltonik).
All mass spectra were acquired in linear mode on autoflex or ultraflex instruments equipped with smartbeam (pancreas) or smartbeam II lasers (all other samples; Bruker Daltonik). For each pixel, 200 laser shots were accumulated at constant laser energy.
The sections were coated with matrix using an ImagePrep (Bruker Daltonik) according to the manufacturer's standard protocols. The brain and testis samples were coated with α-cyano-4-hydroxy-cinnamic acid (Bruker Daltonik), while the pancreas sample was coated with sinapinic acid (Bruker Daltonik).
All mass spectra were acquired in linear mode on autoflex or ultraflex instruments equipped with smartbeam (pancreas) or smartbeam II lasers (all other samples; Bruker Daltonik). For each pixel, 200 laser shots were accumulated at constant laser energy.
