Immunohistochemistry of vacuoles occurring in rat hepatocytes after retinol administration

Polymerization of a vitelline envelope (VE)-like structure produced by using fractionated VE extracts from carp eggs

Fractionation of vitelline envelope (VE) extracts from carp eggs made possible the efficient polymerization of a VE-like structure. The structure corresponded to the fourth layer of the VE or fertilization envelope (FE), and its organization was achieved by reassembly in vitro after solubilization of the sheets composed of filamentous substances or network-like aggregates which were induced by a cortical alveolus sialoglycoprotein or thrombin. The sialoglycoprotein was a serine proteinase and immunolocalized only in the structure at the periphery of cortical alveoli, not in the VE and yolk granules. Ultrastructural features of the VE-like structure suggested that reassembly in vitro occurred via several intermediates in the process of polymerization. A polyclonal antibody produced against one of the assembled VE components, a 64 kDa protein, more intensely immunostained the outer periphery of the VEs than other areas, and immunoelectron microscopy showed that immunogold particles specifically labeled reassembled VE-like structures and major skeletons of the networks or network-like sheets. The protein with a molecular weight of 64 kDa was found to be a DNase. Thus, these results suggest a new approach to investigating not only the FE assembly process in vitro but also the organizing relationship between the major skeleton of the VE or FE and other additional constituents.

Detection of retinyl palmitate and retinol in the liver of mice injected with excessive amounts of retinyl acetate

The transport of subcutaneously injected retinyl acetate (RA, 100,000 IU/mouse, 105,470 nM) was investigated in male ICR mice (10-week-old) at 0, 3, 6, 12, 18, 24 and 72 hr after a single injection. The retinol and retinyl palmitate levels of liver homogenates, bile in the gallbladder and serum from peripheral blood were measured by high performance liquid chromatography (HPLC) method. Retinyl palmitate in the lipid droplets of hepatocytes and Ito cells was localized by a modified gold chloride staining method. Accumulation of retinyl palmitate peaked at 12 hr post-injection and decreased thereafter until 24 hr post-injection. Fluorescence microscopy revealed many fluorescent vitamin A-containing lipid droplets in hepatocytes around central veins at 12 hr post-injection, but such droplets were not observed in the vehicle control mice or at in the RA-injected mice after 18 hr of injection. Electron microscopic observation also indicated that many retinyl esters-containing lipid droplets were observed in hepatocytes around the central veins at 12 hr post-injection, but no droplets were seen in the controls or 18 hr post-injection. The retinyl palmitate levels in liver homogenates assessed by HPLC decreased from 12 to 24 hr post-injection and increased significantly in bile, while retinol in liver homogenates and serum markedly increased. One of the morphological alterations was intense vacuolization in hepatocyte cell cords from the portal toward the central vein observed at 24 hr post-injection. Transitional lipid droplets between vacuoles and lipid droplets were identified in those hepatocytes. These results of HPLC analysis of retinol and retinyl palmitate in liver homogenates, serum, and bile, together with the results of gold chloride staining suggested that subcutaneously injected RA was first incorporated in hepatocytes at 12 hr and then partially metabolized through vacuoles, transferred into the blood and secreted into the bile over a 24 hr period. Many retinyl esters-containing lipid droplets were visualized in Ito cells at 72 hr post-injection. Most of vitamin A in the liver homogenates measured by HPLC was retinyl palmitate. Therefore, the contents in those lipid droplets might be retinyl palmitate.

Binding of bacterial toxins to glycoproteins in the envelopes of rainbow trout eggs

The ability of the vitelline and fertilization envelopes of rainbow trout eggs to trap toxins was investigated using cholera enterotoxin B and staphylococcal enterotoxin B in cytochemical or immunocytochemical experiments. Extracts from both envelopes were investigated by immunoblot analysis to identify toxin-binding proteins after SDS-PAGE. Binding studies of cholera enterotoxin B to vitelline envelopes and fertilization envelopes revealed a greater reactive intensity in the former. Treatment with neuraminidase enhanced the reactive intensity (or deposit) in the vitelline envelope and fertilization envelope outermost layers, with more conspicuous reactivity in the former. Cytochemical experiments showed that exogenous ganglioside GM1 considerably enhanced cholera enterotoxin B binding to vitelline and fertilization envelopes. This enhancement was shown by an intense reactivity following the occurrence of new binding sites on the vitelline envelope inner surface and the inner wall of the zona radiata, a simultaneous extreme reduction in the reactivity of the vitelline envelope outermost layer, and a striking increase in reactive products in the fertilization envelope outermost layer. The surface region of the vitelline or fertilization envelope outermost layer was the binding site for staphylococcal enterotoxin B, and neuraminidase treatment caused a considerable reduction of reactive products in these areas. Immunoblot analysis of cholera enterotoxin B- or staphylococcal enterotoxin B-binding substances in extracts from the vitelline envelopes or fertilization envelopes demonstrated that the great majority of the binding substances are glycoproteins. The present results suggest that glycoproteins constituting the vitelline envelope or fertilization envelope may contribute to the protection of the egg itself or the embryo by trapping noxious toxins.

Differentiation of Clara cells and pneumocytes of the rat by means of enzyme- and immunohistochemistry

Localization of non-specific esterases, Cu-Zn superoxide dismutase and dehydropeptidase-I, in rat lung was investigated enzyme-cytochemically or immunohistochemically. Esterase was demonstrated in Clara cells, type II pneumocytes, and septal cells (or vitamin A-storing lung cells), to a somewhat lesser extent in type I pneumocytes and ciliated epithelial cells of the bronchioles, and to a minor extent in interstitial fibroblasts of the alveolar septum. Large amounts of esterase reaction product were deposited in the rough endoplasmic reticulum and the nuclear envelope in Clara cells, type II pneumocytes, and septal cells, in addition to smaller amounts in other organelles. No reaction product was found in macrophages (histiocytes) in alveolar septi and alveolar macrophages, except for the primary lysosomes or phagolysosomes and trace amounts in the Golgi vesicles, and none in endothelial cells of alveolar blood capillaries, except for primary lysosomes. Immunolocalization of Cu-Zn superoxide dismutase was generally limited to a particular area of Clara cells. A constriction occurred in the apical cytoplasm of Clara cells between an immunoreactive dome-like protrusion and the non-immunoreactive cytoplasm of the supranuclear area, and the dome-like protrusion appeared to be pinched off in a ball-like or oval form. Immunolocalization of dehydropeptidase-I was demonstrated in a dome-like protrusion or supranuclear area of Clara cells or throughout the cytoplasm and in the surface plasma membrane of mesothelial cells. The presence of these enzymes in Clara cells suggests a contribution to the detoxification system of the lung, together with cytochrome p-450-dependent monooxygenase systems.