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In the retina of stalk-eye, five types of cells were distinguished with TEM. 1) The visual cell of type 1 had well-developed microvilli on its apical projection and photic vesicles in the cytoplasm. 2) The visual cell of type 2 had less numerous, shorter, microvilli on its concave apical surface and contained no photic vesicle. The distal portions of both visual cells contained abundant pigment granules highly variable in diameter as well as in electron density. 3) The ganglion cell was a large-sized, ovoid cell in the neural layer, and was particularly remarkable because of the electron-dense lamellar bodies in its perinuclear cytoplasm. A small tuft of microvilli was found deep in its cytoplasm. Both types of visual cells, and the ganglion cell as well, were provided with an axon to form the optic nerve. It is conceivable, therefore, the ganglion cell is also involved in photoreception. 4) The pigmented supportive cell was characterized by numerous, electron-dense pigment granules of uniform size. Its distal cytoplasm ensheathed neighboring visual cells completely at the level of the pigment layer. 5) The non-pigmented supportive cell was located deeper in the somatic and neural layers. Its attenuated processes, which contained intermediate filaments but no pigment granules, surrounded ganglion cells and nerve fiber bundles. The stalk-eye is considered, therefore, to be most specialized for visual function in terms of structure, and consequently to be the dominant visual organ of the Onchidium multiple photoreceptive system. [ABSTRACT FROM PUBLISHER]

Axons of the dermal photoreceptor (DP) cell in the papilla of the dorsal mantle of were examined with a high-voltage electron microscope through 700 serial sections of an osmicated specimen. A single axon extending from the boundary area between the distal and proximal parts of the DP cell was confirmed in 14 out of 19 DP cells in a group. The course of the axon varied from cell to cell, and the diameter and fine structure also varied from region to region of the same axon. The axon traveled along the apical surface of the cell in the initial part, subsequently took a meandering course through the intercellular connective tissue, and frequently ran in close association with muscle fibers along its course. It finally joined a small papillar nerve (SPN) bundle which consisted of several axons derived from other DP cells in the group. No synaptic structure was found on the DP cell body or on the axon. Supporting cells covered the surface of the DP cell, including the initial part of the axon. Sheath cells which were located separately in the connective tissue between the DP cells continuously ensheathed the SPN bundle and the axon of the DP cell. The present study suggests that photic information is conducted from the DP cell to the central nervous system via the axon. [ABSTRACT FROM PUBLISHER]

Infection of a hepatitis C virus (HCV) is confirmed by the presence of HCV antibody or HCV-RNA. Recently, a highly sensitive method to examine HCV-core antigen has been developed. In this study, to evaluate the clinical significance of HCV-core antigen determination, we examined serum HCV infection markers, HCV-core antigen, HCV-RNA (AMPLICOR) and HCV-antibody (third generation) concentrations. We determined 225 serum samples, and three patients receiving the treatment with interferon. In 102 HCV-RNA positive samples, significant correlation was observed between HCV-RNA and HCV-core antigen (r=0.734, p<0.0001). However, three out of 102 (2.9%) cases were included within the negative range of HCV-core antigen (20 fmol/l). The HCV-core antigen value in three patients receiving the treatment with interferon paralleled with the amount of HCV-RNA. The determination of HCV-core antigen by CLEIA is a useful and time-saving method, but an attention should be paid to the presence of false-negative cases.