Patrick W. Bankston

A survey of the binding of polycationic ferritin in several fenestrated capillary beds: indication of heterogeneity in the luminal glycocalyx of fenestral diaphragms.

Polycationic ferritin (PCF) was injected into umbilical veins of 17- and 21-day-gestation rats and saphenous veins of young, male, adult Sprague-Dawley rats and allowed to circulate for 1 min or less followed by excision of tissues and immersion fixation. Fetal liver, intestine, and kidney, as well as adult liver, intestine, pancreas, kidney, adrenal cortex, bone marrow, and pituitary were examined. Nearly all fenestral diaphragms, but no subendothelial structures, were labeled with a tuft of particles in fetal intestine, adult intestine, pancreas, pituitary, and renal peritubular capillaries. A fraction of the diaphragms covering fenestrae in the thyroid, adrenal cortex, and fetal kidney glomerulus, but none in the bone marrow and fetal liver, had associated PCF. In these tissues some diaphragms appeared to be permeable to PCF, because tufts were observed immediately beneath unlabeled fenestral diaphragms either in the basal lamina (fetal kidney, adult thyroid, and adrenal cortex) or on other subendothelial structures (fetal liver, adult bone marrow). Also periodic concentrations of PCF were observed in the lamina rara interna of the adult glomerular basement membrane. PCF binding to the fenestral diaphragms and the basal lamina in the adult intestine and the renal glomerulus, respectively, have been reported by Simionescu et al. ((1981a) J. Cell. Biol. 90, 605-613) and Kanwar and Farquhar ((1979) J. Cell. Biol. 81, 137-153) as indicating accumulations of anionic material. In this study we have demonstrated not only high-specificity binding of PCF to fenestral diaphragms in capillaries of organs other than intestine and pancreas, but also considerable variation of PCF stainability of fenestral diaphragms in other organs.

The development of the sinusoids of fetal rat liver: Localization of endogenous peroxidase in fetal Kupffer cells

Endogenous peroxidase is the cytochemical marker used to identify Kupffer cells in the adult liver. In this study, we show by ultrastructural cytochemistry that Kupffer cells of the fetal rat liver are endogenous peroxidase positive. The reaction product is localized in the endoplasmic reticulum including the perinuclear cisternae and in a few lysosome-like dense bodies. Serial sections of Golgi regions suggest that GERL and not the Golgi stacks, is peroxidase positive. As in the adult liver, peroxidase is not localized in endothelial cells. Kupffer cells do not appear to transform from endothelial or extravascular developing monocytic cells and are present prior to bone marrow formation. The relevance of these observations with respect to the possible origin of the Kupffer cell is discussed.

Ultrastructural observations on tissues processed by a quick-freezing, rapid-drying method: Comparison with conventional specimen preparation

Abstract A quick-freeze, rapid-dry method for processing unfixed tissue for electron microscopy has been developed. The technique employs freezing on a cryogenchilled metal surface and drying in a cryosorption vacuum apparatus that allows osmium-vapor fixation and epoxy-resin embedment under high vacuum. Liver, kidney, bone marrow, and monolayer cultures of ventricular myocytes were selected as tissue specimens representing a wide range of physical properties, to demonstrate the practical aspects of achieving good ultrastructural morphology by freeze drying. A comparison was made between freeze drying and conventional processing using aldehyde fixation and alcohol dehydration. The preservation of cellular ultrastructure achieved by freeze drying allowed the identification of specific cell types within each specimen. Membranous organelles were well preserved, surrounded by cytoplasmic ground substance devoid of ice crystal damage. Electron-dense material was observed within the rough endoplasmic reticulum and Golgi cisternae and vesicles of frozen-dried, but not conventionally processed cells. This suggests the preservation by freeze drying of cytoplasmic components otherwise extracted from the cell by solvent exposure.

Phagosome-lysosome interactions related to erythrophagocytosis in Kupffer cells of fetal rat liver

SummaryKupffer cells of fetal rat liver were examined by ultrastructural cytochemical methods to reveal acid phosphatase (AcPase) activity in lysosomes. Elongated cisternae, 940–1150 Å in width containing AcPase reaction product, were identified in these cells. These cisternae were sometimes in continuity with phagosomes containing engulfed erythrocytes. Observations suggest that such cisternae may partly encircle these phagosomes. The relationships of these cisternae to GERL (Golgi Endoplasmic Reticulum Lysosomes) is discussed.