Mikio Yasuda

Electron microscopic study on the innervation of the pancreas of the domestic fowl

SummaryThe innervation of the pancreas of the domestic fowl was studied electron microscopically. The extrapancreatic nerve is composed mostly of unmyelinated nerve fibers with a smaller component of myelinated nerve fibers. The latter are not found in the parenchyma. The pancreas contains ganglion cells in the interlobular connective tissue. The unmyelinated nerve fibers branch off along blood vessels. Their synaptic terminals contact with the exocrine and endocrine tissues. The synaptic terminals can be divided into four types based on a combination of three kinds of synaptic vesicles. Type I synaptic terminals contain only small clear vesicles about 600 Å in diameter. Type II terminals are characterized by small clear and large dense core vesicles 1,000 Å in diameter. Type III terminals contain small clear vesicles and small dense core vesicles 500 Å in diameter. Type IV terminals are characterized by small and large dense core vesicles. The exocrine tissue receives a richer nervous supply than the endocrine tissue. Type II and IV terminals are distributed in the acinus, and they contact A and D cells of the islets. B cells and pancreatic ducts are supplied mainly by Type II terminals, the blood vessels by Type IV terminals.

The cardiac conducting system of the fowl.

Twenty‐four hearts of Brown Leghorn ranging in age from newly hatched to adult were investigated histologically to elucidate the topographical disposition of the entire cardiac conducting system. Through this study, the birds heart was found to have the same specialized conducting system as that of mammals. Moreover, in addition to this system, the nodus truncobulbaris and the fasciculus truncobulbaris were reported in detail, and the anulus atrio‐ventricularis dexter was confirmed. These peculiar nodes and bundles of the birds heart are discussed in comparison with the mammalian cardiac conducting system.

Intramitochondrial bodies in bovine adrenocortical cells

SummaryElectron dense, homogeneous, mostly round intramitochondrial bodies were found in bovine adrenal glands, predominantly in the zona glomerulosa. The histochemical results obtained suggest that these bodies might contain a considerable amount of protein, although the possibility that substances other than proteins are contained in these bodies cannot be completely ruled out. The physiological significance of the intramitochondrial bodies remains unclear.

Light and electron microscopic studies of intramitochondrial bodies in bovine adrenocortical cells by proteolytic digestion

SummaryThe nature of the intramitochondrial bodies in bovine adrenocortical cells was investigated both light and electron microscopically, by applying enzymatic digestion on paraffin and epon sections. The result that these bodies were extracted completely either by pepsin or by trypsin strengthened the validity of the previous conclusion that their nature is proteinaceous.

Development of the Cardiac Conducting System in the Chick Embryo

Chick embryos at 3 to 15 days of incubation were examined for the developmet and differentiation of the “four rings” of the heart. It was clarified that nodes and bundles of the impulse conducting system in the adult chicken were derived from these rings. This finding was very important for understanding the cardiac conducting system in birds and mammals.

Fine structure of the ependymal cells in the area postrema of the domestic fowl.

SummaryThe ultrastructure of the ependymal cells in the area postrema of the domestic fowl was studied by scanning and transmission electron microscopy. The ependymal surface of the area postrema is covered with many furrows and ridges. These ridges consist of ependymal cells aggregated in a fan-like shape. The ependymal cell lacks clustered cilia, microvilli are few, and a long basal process extends through the parenchymal layer of the area postrema. Within the cytoplasm as well as in the basal process, a spherical body with a diameter ranging from 1.5 to 2 gmm is occasionally observed.

Isolation of intramitochondrial bodies in bovine adrenocortical cells by density gradient centrifugation.

SummaryTwo methods for isolating the intramitochondrial bodies from bovine adrenocortical cells are proposed. Electron microscopic examination shows that discontinuous sucrose density gradient centrifugation can separate the fraction rich in intramitochondrial bodies, but some indistinguishable fragments remain among them. Continuous sucrose density gradient centrifugation is probably superior to the former method in obtaining a highly purified fraction of the bodies. The amido black positive granules, presumed to be intramitochondrial bodies, are collected in the fractions of the sucrose density of around 1.27 (1.23–1.30), which lack cytochrome c oxidase activity.

Scanning electron microscopic analysis of the linings of the fourth ventricle in the domestic fowl.

SummarySurface features of the ependymal linings of the fourth ventricle in the fowl were analyzed employing the scanning electron microscope (SEM). On the floor of the median sulcus, each ependymal cell has a solitary cilium, whereas on both sides of the sulcus, cilia are so densely distributed that the details of the underlying cell surface are usually obscured. On the roof of the fourth ventricle, except for the surface of the ciliated groove where numerous cilia are present, the ependymal cells are polygonal in shape, and the center of each cell possesses an aggregate of ten to twenty cilia. Cell surfaces of the choroid tela are entirely covered with delicate microvilli and possess clumped cilia. The ependymal cell surfaces of the area postrema are dome-like in shape. Each ependymal cell has a solitary cilium and shows a smooth surface free of microvilli.

Unusual mitochondrial ultrastructure in the pig adrenal cortex

SummaryUnusually large mitochondria with few cristae were observed in the cells of the boundary layer between the zonae fasciculata and reticularis of the pig adrenal. These mitochondria occasionally contained parallel arrays of beaded filaments which appeared to be composed of repetitive electron opaque particles, measuring 10 to 11 nm in diameter. The possibility that these filaments are arranged in closely packed arrays of tubular structures with a central filament is discussed.

Scanning electron microscopy of the ventricular surface of the paraventricular organ in the domestic fowl

SummaryThe ventricular surface of the paraventricular organ in the domestic fowl is covered with supraependymal fiber elements. These fibers form a dense network having a web-like appearance and a coarse network of fibers running over the ventricular surface. The dense, web-like networks are mainly distributed throughout the caudal region of this organ, whereas the coarse networks are observed in the rostral region. In addition to these structures, spherical bodies with diameters approximately 2.5 to 6 μm are also encountered.