Human erythrocytes coated with ferritin-conjugated anti-A antibody were recognized to adhere to neutrophil leukocytes showing electron-dense plaques in the contact sites of the cells.
This binding phenomenon with the plaques is specific for antibody sensitized cells.
The ultrastructure of the plaque was characterized by an electron dense cytoplasmic layer immediately beneath the plasma membrane of the neutrophil. The red cell cytoplasm showed none of this cytoplasmic specialization. The cell membranes in the plaque region are separated by an intercellular space about 250Å wide.
Deformation and fragmentation occurred in the red cells attached to neutrophils with the plaques. This seems to imply a possible rôle of the plaques in the destruction of erythrocytes.
Although ferritin particles were attached to the red cell surface, they were not recognized in the intercellular space of the plaques. It was thus discussed whether the plaque region was, as postulated by Lo BUGLIO et al., a specific binding site or a receptor for antibodies.

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1. The carotid body of Urolocha domestica was studied by light and electron microscopy.
2. The ultrastructure of the chief cell essentially corresponded to that of the mammalian carotid body.
3. Many nerve terminals occurred around a chief cell, some of which made synaptic contacts with the latter. The synaptic vesicles were on the neural side as in the mammalian carotid body, and it was considered that these nerve terminals were of efferent nature.
4. Synaptic contacts were described between nerve terminals themselves around the chief cell. The synaptic vesicles occurred frequenty on both sides of this axo-axonic synapse. In this type of synapse accumulations of synaptic vesicles may not necessarily indicate a presynaptic nature.
5. Synapse between a chief cell and a nerve terminal having further synaptic contracts with other terminals was illustrated and discussed. This type of synapse was similar to the so-called serial synapse regarded by some authors as a possible morphological basis for presynaptic inhibition.

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A few drops of human blood were fixed in a relatively large volume of glutaraldehyde of various concentrations. After dehydration in acetone the blood cells were dried on glass slides in a warm breeze, coated with carbon and gold and observed under the scanning electron microscope.
1. The deformations of erythrocytes caused by the osmotic effect of the fixative were examined. Large differences in osmotic resistance were shown among individual cells especially in hypotonic fixation. Glutaraldehyde concentration of 1% (in a 0.1M phosphate buffer) was found to be optimal for the preservation of the natural shape of normal erythrocytes.
2. After this fixation the normal erythrocytes were represented by smooth-surfaced biconcave disks occasionally mingled with uniconcave ones. Some erythrocytes showed one or several wart-like elevations in their cell surface. These are believed to correspond to the segresome-like appendage seen in the transmission electron microscopy of sectioned erythrocytes (MIYOSHI and MATSUKURA, 1969).
3. As pathological materials, the erythrocytes in elliptocytosis, hereditary spherocytosis and aplastic anemia were observed and their morphological abnormalities were described. Small conic pits were found on the surface of the erythrocytes in spherocytosis.

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The surface structure of human blood platelets and their alterations by thrombin were studied by scanning electron microscopy.
The majority of the native platelets were discoid or lentiform as already reported by previous authors using the transmission electron microscope. The surface was relatively smooth, but some platelets had a few slight elevations and conic depressions which may correspond to the openings of the endoplasmic reticulum. A few platelets possessed at the margin one or two spiny short projections.
The platelets collected by careful centrifugation partly showed a few long pseudopods which were issued from the margin of the platelet and supposed to be the elongation of the spiny projections described above. About 78% of the collected platelets were discoid in form, 12.5% spheroidal, 5.5% spherical and 4% irregular.
The addition of thrombin to the citrated, platelet rich plasma caused the following changes. At first small protrusions appeared on the entire surface of the platelets except for their margin. The discoid platelets then transformed into spheres covered by the grown and rounded protrusions and aggregated, while the formation of pseudopods proceeded. Fibrin strands about 0.1μ in thickness appeared to form networks into which the aggregated platelets were arrested more and more firmly.

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Transmission electron microscopy of thin sections of human (adult and newborn) and mouse erythrocytes revealed the occasional occurrence of a small round appendage (about 0.5μ in diameter) projecting, with a thin pedicle, from the surface mainly of the peripheral thick portion of erythrocyte. The appendage contained an accumulation of vesicles which was suggested to be derived from the membranes of cell organelles and segregated from the cell. This appendage probably corresponds to the “wart” of erythrocyte found under the scanning electron microscope (TOKUNAGA, FUJITA and HATTORI, 1969).

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In the taste buds of rat circumvallate papillae the taste bud cells are easily distinguished into two cell types, a light cell and a dark cell, according to their cellular arrangement and morphological characteristics.
1. The cytoplasm of the light cell, which is less dense than that of the dark cell, is characterized by the presence of a few lysosomes and many empty vesicles. The apical portion of the light cell ends in short microvilli which do not reach the outer surface of the taste pore.
2. The dark cell contains well-developed rough-surfaced endoplasmic reticulum and numerous dense granules in the cytoplasm. In its apical portion the dark cell projects a rod-shaped process extending from the inner part of a taste pore to the external environment. The dark cell partly envelops the light cell in a manner similar to the relationship between nerve and Schwann cell.
3. In the nerve fibers ramifying within the taste bud there are two forms comprising club-like endings and beaded endings. Synaptic contacts take place between the nerve and the light cell at the lower half of the bud. Synaptic vesicles of about 400-600Å in diameter are found in the cytoplasm of the light cells. Occasionally, the axoplasm contain both empty and granular vesicles.

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In einer Untersuchung der Langerhansschen Inseln des Karpfens, die sich hauptsächlich auf die gleichzeitige licht- und elektronenmikroskopische Betrachtung derselben Zellen auf benachbarten Dick- und Dünnschnitten stützt, werden folgende Zelltypen abgegrenzt:
1. B-Zelle mit sehr vielgestaltigen Granula und typischer lichtmikroskopischer Anfärbung (Gomori +, negativ bei Versilberung und Tryptophannachweis).
2. Typ-II-Zelle mit sehr wenig elektronendichten Granula, negativ bei allen lichtmiktroskopischen Färbungen, die versucht wurden. Anhand dieser Zellen wird das Problem der agranulären Zellen erwähnt und auf Fixierungsartefakte (Osmium-, Acroleinfixierung) hingewiesen.
3. Typ-III-Zelle mit rundlichen Granula der größten relativen Elektronendichte und positiver Reaktion beim Tryptophannachweis nach ADAMS.
4. Typ-IV-Zelle mit sehr kleinen Granula; Anschnitte solcher Zellen gleichen gelegentlich marklosen Nervenfasern.
5. Typ-V-Zellen, die mit ihren Granula den exokrinen Pankreaszellen ähneln und durch die Silbermethode nach WINCKLER geschwärzt werden.

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