Fixation of rat parotid with an unbuffered osmium tetroxide solution containing nearly saturated potassium (pyro)antimonate resulted in abundant deposition of cation-antimonate precipatates in acinar cells. Altering the antimonate concentration, including buffers or chelators in the solution or changing the primary fixative resulted in an altered intensity and distribution of the precipitates formed in the tissue, apparently reflecting a degree of selectivity in ion localization. Decreasing the concentration of pyroantimonate to about half-saturation preserved predominantly the less soluble antimonate salts (e.g., Na+, Ca++) and resulted in preferential retention of deposits along the plasmalemma and in mitochondrial "dense bodies," with loss of most cytoplasmic and nuclear precipitates. A similar pattern was seen if fixation with the high concentration antimonate-osmium procedure was followed by a prolonged rinse. Adding phosphate or collidine buffers markedly decreased precipitates in the nuclei and on granular reticulum as well. Phosphate buffer or ehtyleneglycoltetraacetate inhibited in vitro precipitation of calcium and sodium and decreased or abolished plasmalemmal deposits. Glutaraldehyde fixation, either in the presence of antimonate or prior to antimonate-containing osmium tetroxide, abolished heterochromatin deposits. Mitochondrial dense bodies were of two types, one containing precipitate and the other inherently osmiophilic. The latter were also observed in pyrophosphate-osmium controls. Results from in vitro titrations of cations with the various antimonate methods and from neutron activation analyses of fixed tissues supported conclusions drawn from fine structural distribution patterns and were interpreted as follows. In rat parotid acinar cells, deposits in heterochromatin and on granular reticulum probably arose from precipitation in sites of high K+ and H+ as well as--NH3+-rich histones. Plasmalemmal antimonate deposits demonstrated sites of sodium and/or calcium accumulation. Some mitochondrial dense bodies contained Ca++ whereas others were inherently osmiophilic. Large, extracellular deposits were probably predominantly sodium precipitates.

Ammonia↗

PubMed1975

Mast cell phagocytosis of red blood cells.

The prevalence of mast cells infiltrating bone marrow of different rats varied widely, as did the staining properties and size of their cytoplasmic granules. Bone marrow mast cells from several rats revealed large membrane-limited inclusions which stained metachromatically or orthochromatically and resembled inclusions in some macrophages. Ultrastructurally, mast cells varied widely in content of uniform dense granules or enlarged granules with less dense, fine grained content. Some of the large inclusions observed ultrastructurally in mast cells were heterophagic vacuoles which contained erythrocytes or reticulocytes, or remnants from other phagocytized cells, possibly neutrophils or unidentified homogeneous material. Smaller bodies, interpreted as fragments of erythrocytes, lay extracellularly near mast cells and occupied small, membrane-limited, heterophagic vacuoles in some mast cells. In other mast cells, communal vacuoles enclosed several specific cytoplasmic granules in various stages of disruption. The communal vacuoles occasionally opened to the extracellular space. A few large indeterminate vacuoles in mast cells contained amorphous flocculent matter which apparently derived either from coalescence of cytoplasmic granules through fusion of granule membranes or from endocytosis.

Animals↗

PubMed1974