Effect of aging on SIF cells of the rat.

The effect of aging on the SIF cells was studied with the formaldehyde-induced fluorescence (FIF) method and electron microscopy (EM). For EM the specimens were fixed with glutaraldehyde-OsO4 and KMnO4. The emission spectra were recorded microspectrofluorimetrically. Under fluorescence microscopy in newborn and young adult rats, only one type of SIF cell emitting greenish-yellow FIF could be found, whereas in aged rats another type of SIF cell emitting yellowish-brown, granular FIF was also found. The emission spectra of the greenish-yellow FIF of the newborn and young adults and the aged rats differed from that recorded from the yellowish-brown granular SIF cells. According to the size of the dense-cored vesicles, two kinds of SGC cell could be distinguished in the hypogastric ganglion of the newborn and the young adult rats after glutaraldehyde fixation. The first type contained 50- to 150-nm vesicles, and the second type contained 50- to 250-nm vesicles. In aged rats a third type of SGC cell containing elongated 50 X 250 nm dense-cored vesicles was found. After KMnO4 fixation the classification was the same as after glutaraldehyde in newborn and young adult animals. In aged rats three types of SGC cell could be distinguished, according to the size, shape, and core of the storage granules; the first with 100- to 300-nm empty vesicles, the second with 100- to 300-nm vesicles with small cores, and the third with 100- to 500-nm irregular vesicles filled with electron-opaque material with a denser core.