Abstract:
The morphology of Kupffer cells was
examined in the liver of the juvenile Nile crocodile
using light microscopy and transmission electron
microscopy. Pleomorphic Kupffer cells were located in
the sinusoids, in the space of Disse, in the hepatic
parenchyma and often connected adjacent sinusoids.
The cell surfaces were irregular due to the presence of
filopodia and lamelliapodia with phagocytosis of white
blood cells, red blood cells and thrombocytes being evident.
The cells were in close contact with endothelial
cells and pit cells in the sinusoidal lumen and with
stellate cells in the space of Disse. The cytoplasm contained
large phagosomes comprising a combination of
ceroid pigment, melanosomes and siderosomes. The
nuclei were often indented and eccentrically placed due
to the presence of the phagosomes. Conspicuous clusters
of membrane-bound tubular organelles with a filamentous
or crystalline interior were observed in the
cytoplasm. The clusters were sometimes separated into
smaller groups around phagosomes. A clear zone
existed between the limiting membrane and the interior
of these tubular organelles with the electron-dense
interior profiles being, respectively, circular, angular or
divided. The tubular organelles have not previously
been described in Kupffer cells and possibly represent
lysosomes with specialized functions. Mitochondria,
microtubules, Golgi profiles, granular and smooth endoplasmic
reticulum, and a few cytoplasmic lipid droplets
were also present. The presence of the tubular organelles
and the occurrence of the Kupffer cells in different
locations in the liver of the juvenile Nile crocodile are
indicative of particularly active and mobile cells.
