In the hepatic parenchyme of the crucian, Carassius carassius no interhepatocytic bile canaliculi are detected, but each hepatocyte possesses a single intracellular bile canalicule filled with microvilli protruded from the hepatocyte. The intrahepatocytic bile canalicule originates at the neighborhood of the nucleus to extend to the cell surface where it empties into the intraparenchymal biliary passage running in the interhepatocytic space. The pericanalicular cytoplasm contains many small vacuoles which have possibly been elaborated in Golgi complexes and may be discharged by emiocytotic mechanism into the canaliculus, suggesting bile secretion in the crucian liver. The intercellular biliary passage consists of the terminal bile ductule composed of two elongated flat epithelial cells enclosing a narrow and twisted lumen in between; the secondary or middlesized ductule is surrounded by three cuboidal epithelial cells, and the large bile duct by five or more cuboidal cells and a smooth muscle layer. The basal lamina is detected only in the middle-sized ductule and in the large duct. The intracellular bile canalicules attached to the proximal bile ductule by means of the junctional complex are classified into the “terminai” and “side bile canalicules”; they are attached to the proximal end and the lateral wall of the terminal bile ductule, respectively. The ectoplasmic layer bordering the intracellular bile canalicule is rich in microfilaments which partially enter microvilli, and the epithelial cells of the intercellular biliary duct system are also characterized by abundance of microfilaments. These probably contractile cytoplasmic filaments may control or accelerate bile flow through intrahepatic biliary passages. The periductular or periductal cells closely apposed to intercellular bile passages are thought to be mesenchymal cells such as fibroblasts among which histiocytoid elements are intermingled.

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Four types of chief cells can be discerned in the cat carotid body. These cells are referred to as types 1 to 4. They are characterized-in the given order-by decreasing amounts of noradrenaline (argentafin reaction) and acidic protein(s) (HCl hydrolysis/basic dye methods). The concentrations of acidic protein roughly parallel that of noradrenaline, being highest in type 1 cells and lowest in type 4 cells.
It is suggested that acidic protein and monoamines together are stored in specific granules and secreted by ekcytosis. The various cell types reflect functional conditions. Histochemical methods to identify acidic protein are less sensitive than methods for monoamines. Thus, only catecholamines have been detected in chief cells of those animals, which contain only a few and small specific granules. Cat carotid body chief cells, by contrast, serve as a suitable model to demonstrate the parallelism in storage and secretion of monoamines and acidic protein.

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Quinacrine (Atebrin), an antimalarial drug that binds to adenine nucleotides, was used to label paraneurons. The drug was dissolved in physiological saline and intraperitoneally injected (rats, mice, guinea pigs) in concentrations of 120 or 200mg/kg body weight. The animals were killed three days later and paraneurons were studied in the fluorescence microscope after freeze drying. Bright fluorescence is observed in adrenomedullary cells, SIF cells, carotid body chief cells, pancreatic islet cells, anterior pituitary cells, pinealocytes, and mast cells. Weak fluorescence occurs in thyroid parafollicular cells, Merkel cells, and a few entero-endocrine cells. It is suggested that quinacrine binds to ATP or related adenine nucleotides which are stored in secretory granules of paraneurons. Varying fluorescence intensity seems to depend on different concentrations of adenine nucleotides within the storage granules, as well as on the different size and number of these granules in various paraneurons. Besides formaldehyde-induced fluorescence of biogenic amines, HCl-basic dye staining methods and electron microscopy, the method is useful to identify and define paraneurons.

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Ultrastructural localizations of phosphatases were observed in the rat parathyroid gland. Activities of alkaline phosphatase and adenosine triphosphatase were found on the caveolae or pinocytotic vesicles of the capillary endothelia. In the parenchymal cells, they were demonstrated to be stronger both at the plasma membranes facing the pericapillary space and at their transitional portions to the lateral plasma membranes than at the remaining lateral plasma membranes including microvilli. Activities of thiamine pyrophosphatase and inosine diphosphatase were detected on one or two layers of lamellae at the inner face of the Golgi apparatus, and the localization of the latter enzyme was more restricted than that of the former. Additionally, they were sometimes observed also on the blood capillary wall. Contrasted to these enzymes, acid phosphatase activity was demonstrated on the entire Golgi lamellae besides lysosomes, but not on multivesicular bodies, vacuolar bodies and storage granules.

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Gastrin cells in the pigeon, quail, gull and kite were identified at ultrastructural level by immunocytochemistry, using the consecutive semithin/ultrathin section technique. In contrast to the gastrin granules known in mammals, the avian gastrin granules generally contained a consistent dense core accompanied by a clear halo between the core and limiting membrane. The mean diameters of gastrin granules in the pigeon, quail, gull and kite were 211±37, 247±45, 331±61 and 353±73nm respectively. The carnivorous birds seemed to possess larger gastrin granules than the grain-eating birds. The species differences in the size and fine structure of the gastrin granules were discussed.

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The pit membrane in the pit organ of a crotaline snake is about 15μm thick. Myelinated nerve fibers from the trigeminal nerve enter the pit membrane and swell into palmate structures on demyelination. Demyelinated fibers repeat branchings and their terminals contain many mitochondria. The terminal portion is not surrounded with Schwann cell processes. There are many small vesicles (30-60nm in diameter) in the extracellular space in close association with the nerve terminal membranes. The spreading of branches from each palm seemed to have a definite territory which would correspond to the unit area detected with electrophysiological methods. But no“unit structure”was revealed by electron microscopy.
Intraepithelial free nerve endings exist in the outer epithelial layer. The nerve bundles from the trigeminal branches contain some unmyelinated fibers which come in close contact with vascular elements in the pit membrane.

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Basal-granulated cells form a large aggregation on the top of villi in the duodenum and upper jejunum of the human fetus. This peculiar structure was discovered and precisely described by SEGI (1935) but long neglected by later researchers. This paper proposes to call it“Segi's cap”and preliminarily reports some new findings of our own.

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