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In 1960s, histological study on developing CNS led us to a novel finding that the periventricular layer (“Matrix” of W. His) of fetal neocortex is composed solely of the matrix cells. Application of 3H-thymidine autoradiography revealed “elevator movement” of the matrix cells. Following the stage of pure matrix cell proliferation (Stage I), stage of neuron production (Stage II) ensues, and when Stage II is over, stage of gliogenesis (Stage III) follows immediately; first, glioblasts, then astrocytes, oligodendrocytes and microglia differentiate, in sequence.As for the mechanism of the switching, recent progress in molecular research on dynamism of the chromatin and transcription-factors revealed the irreversible epigenetic changes controlling the switch. In Stage I of cytogenesis, axial ectodermal cells escape from irreversible differentiation into epidermis, and change into matrix cells composing the neural plate. In Stage II, some matrix cells, in which proneural genes are activated, exit cell cycle to become neurons. When Stage II ends, the neural-repressor REST/NRSBF is up regulated and occupies RE-1 silencer region to irreversibly inactivate neuron-specific genes including the type II Na+ channel, thereby matrix cells can now only produce non-excitable cells, i.e., glial cells. This is the Stage III of cytogenesis of the CNS.

We started to use virtual slide (VS) and virtual microscopy (VM) systems for quick frozen intra-operative telepathology diagnosis in Kyoto, Japan. In the system we used a digital slide scanner, VASSALO by CLARO Inc., and a broadband optic fibre provided by NTT West Japan Inc. with the best effort capacity of 100 Mbps. The client is the pathology laboratory of Yamashiro Public hospital, one of the local centre hospitals located in the south of Kyoto Prefecture, where a fulltime pathologist is not present. The client is connected by VPN to the telepathology centre of our institute located in central Kyoto. As a result of the recent 15 test cases of VS telepathology diagnosis, including cases judging negative or positive surgical margins, we could estimate the usefulness of VS in intra-operative remote diagnosis. The time required for the frozen section VS file making was found to be around 10 min when we use ×10 objective and if the maximal dimension of the frozen sample is less than 20 mm. Good correct focus of VS images was attained in all cases and all the fields of each tissue specimen. Up to now the capacity of best effort B-band appears to be sufficient to attain diagnosis on time in intra-operation. Telepathology diagnosis was achieved within 5 minutes in most cases using VS viewer provided by CLARO Inc. The VS telepathology system was found to be superior to the conventional still image telepathology system using a robotic microscope since in the former we can observe much greater image information than in the latter in a certain limited time of intra-operation and in the much more efficient ways. In the near future VS telepathology will replace conventional still image telepathology with a robotic microscope even in quick frozen intra-operative diagnosis.