Kazuhiko Shoumura

An attempt to relate the origin and distribution of commissural fibers to the presence of large and medium pyramids in layer III in the cat's visual cortex

Summary An attempt was made to relate the topical changes in the distribution of commissural connections to those in the cytoarchitecture of the cats visual cortex. It was suggested that commissural fibers arise mostly from layer III. In accordance with this, there was some correlation between the distribution of commissural connections and that of large and medium pyramidal cells of layer III. The 17/18 border region is especially abundant in commissural connections, giving a large amount of fibers to the 17/18 border region, the most lateral part of area 19 and the most medial part of the Clare-Bishop area on the opposite side, and cytoarchitectonically exhibits numerous large pyramidal cells of layer III. The medial part of area 18 and the lateral part of area 19 show dense to moderate commissural connections, sending a considerable amount of fibers to the adjoining parts of areas 17 and 18, the lateral part of area 19 and the medial part of the Clare-Bishop area on the opposite side, and contain many medium pyramidal cells with several large pyramids of layer III. The 18/19 border region has sparse commissural connections sending a few fibers to the corresponding part of the cortex and the lateral part of the Clare-Bishop area on the opposite side, and contains a small number of medium pyramidal cells of layer III. By contrast, most of area 17 except the most lateral part is completely lacking in commissural connections and exhibits a narrow layer III filled mostly with small pyramidal cells.

Structural organization of ‘callosal’ OBg in human corpus callosum agenesis

The structural organization of the callosal OBg was studied in Nissl and Weil stained sections of two human brains completely lacking in the corpus callosum. OBg of the normal brain contains a set of distinctive large pyramidal cells in layer III. By contrast, in the brains with absence of the corpus callosum, layer III of OBg contained a slightly reduced number of smaller pyramidal cells than normal, and the characteristic large pyramidal cells were scarsely detectable. Other layers of OBg were not definitely changed. Furthermore, acallosal striate cortex revealed no specific changes. From these observations, it was suggested that the large layer III pyramids of OBg might be closely related to callosal connections.

Evidence for penetration of intraperitoneal horseradish peroxidase into vagal preganglionic neural elements.

Intraperitoneal horseradish peroxidase was found to penetrate directly into the vagal preganglionic neural elements. After intraperitoneal administration of horseradish peroxidase, the bilateral dorsal nucleus of vagus nerve was labelled retrogradely with the enzyme. Other regions of medulla oblongata and sacral spinal cord were free from labelling. The significance of these findings was considered in relation to studies of autonomic nerve supply of abdominal viscera using retrograde transport of horseradish peroxidase.

Origin of Autonomic Nerve Fibers Innervating the Parathyroid Gland in the Rabbit

The cells of origin of nerve fibers innervating the parathyroid gland were studied in the rabbit using the HRP-retrograde transport method. Numerous labeled neurons were observed in the caudal half of the ipsilateral superior cervical ganglion following HRP injection into the parathyroid gland. Furthermore, in the medulla oblongata, labeled neurons were found in the dorsal nucleus of the vagus and many of them were distributed caudal to the level of the obex.

Ultrastructure of acetylcholinesterase containing striato-nigral neurons transporting HRP retrogradely

The fine structure of striato-nigral efferent neurons, retrogradely labeled with HRP, was studied. The neuron showed a medium sized ovoid or tri-angular perikaryon. Short or medium lengthened granular endoplasmic reticula, having a tendency to wind and pile up in stacks were observed. This neurons corresponds to a type III neuron according to our classification [4,5]. The neuron showed reaction products, indicating AChE activity, in the granular endoplasmic reticula and plasma membrane.

Pathway from dorsal lateral geniculate nucleus to visual cortex (visual radiation) in cats.

Abstract The cats visual radiation was studied by placing lesions stereotaxically in various parts of the dorsal lateral geniculate nucleus and tracing degenerated fibers in serial sections stained by the method of Nauta and Gygax. 1. (1) The visual radiation is initially oriented rostrally. It proceeds rostralward about 2–3 mm along the dorsal border of the dorsal lateral geniculate nucleus before turning caudalward. 2. (2) The visual radiation is entirely included in the external sagittal stratum. 3. (3) The visual radiation can be divided into 3 parts, pars anterodorsalis, intermedia and posteroventralis, according to their origin, course and termination. 4. (4) The ‘temporal knee’ or ‘temporal loop’ also exists in cats. It is formed by fibers arising from the pars posterior and dorsalis of the dorsal lateral geniculate nucleus. 5. (5) A second recurrent detour of the visual radiation (monocular visual pathway) was found. It is formed by fibers from the lateral tip (monocular segment) of the dorsal lateral geniculate nucleus. 6. (6) No evidence of the crossed geniculo-cortical pathway was observed.