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Ninomiya, Taihei (3)
Takada, Masahiko (3)
Hiraoka, Mari (1)
Inoue, Ken-ichi (1)
Inoue, Kenichi (1)
Nakagawa, Hiroshi (1)
Sawamura, Hiromasa (1)
Yamashita, Toshihide (1)
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Reorganization of corticospinal tract fibers after spinal cord injury in adult macaques
Previous studies have shown that sprouting of corticospinal tract (CST) fibers after spinal cord injury (SCI) contributes to recovery of motor functions. However, the neuroanatomical mechanism underlying the functional recovery through sprouting CST fibers remains unclear. Here we investigated the pattern of reorganization of CST fibers below the lesion site after SCI in adult macaques. Unilateral lesions were made at the level between the C7 and the C8 segment. The extent of spontaneous recovery of manual dexterity was assessed with a reaching/grasping task. The impaired dexterous manual movements were gradually recovered after SCI. When anterograde tract tracing with biotinylated dextran amine was performed to identify the intraspinal reinnervation of sprouting CST fibers, it was found that the laminar distribution of CST fibers was changed. The sprouting CST fibers extended preferentially into lamia IX where the spinal motor neuron pool was located, to innervate the motor neurons directly. Instead, few, if any, CST fibers were distributed in the dorsal laminae. The present results indicate that CST fibers below the lesion site after SCI in macaques are reorganized in conjunction with the recovery of dexterous manual movements.
Multisynaptic Inputs from the Medial Temporal Lobe to V4 in Macaques
Retrograde transsynaptic transport of rabies virus was employed to undertake the top-down projections from the medial temporal lobe (MTL) to visual area V4 of the occipitotemporal visual pathway in Japanese monkeys (Macaca fuscata). On day 3 after rabies injections into V4, neuronal labeling was observed prominently in the temporal lobe areas that have direct connections with V4, including area TF of the parahippocampal cortex. Furthermore, conspicuous neuron labeling appeared disynaptically in area TH of the parahippocampal cortex, and areas 35 and 36 of the perirhinal cortex. The labeled neurons were located predominantly in deep layers. On day 4 after the rabies injections, labeled neurons were found in the hippocampal formation, along with massive labeling in the parahippocampal and perirhinal cortices. In the hippocampal formation, the densest neuron labeling was seen in layer 5 of the entorhinal cortex, and a small but certain number of neurons were labeled in other regions, such as the subicular complex and CA1 and CA3 of the hippocampus proper. The present results indicate that V4 receives major input from the hippocampus proper via the entorhinal cortex, as well as “short-cut” pathways that bypass the entorhinal cortex. These multisynaptic pathways may define an anatomical basis for hippocampal-cortical interactions involving lower visual areas. The multisynaptic input from the MTL to V4 is likely to provide mnemonic information about object recognition that is accomplished through the occipitotemporal pathway.
Ischaemia in the Zinn–Haller circle and glaucomatous optic neuropathy in macaque monkeys
The British Journal of Ophthalmology
To elucidate the morphological features of optic neuropathy in an ischaemic model of glaucoma in macaque monkeys.
The regional degenerative process was investigated by experimentally occluding the paraoptic branches of the lateral short posterior ciliary artery, that is, the circle of Haller and Zinn, in 11 eyes. Morphological changes in nerve fibres in the lamina cribrosa were evaluated by histopathology, immunocytochemistry and angiography, and the findings were compared with those observed in an aged macaque with spontaneous glaucomatous optic neuropathy.
Retinal ganglion cell axons were grouped in bundles and traversed through pores in columns of the lamina cribrosa. The processes of astrocytes extended to the bundles, and capillaries branched in surrounding connective tissue from the circular arterioles. Experimental ischaemia induced time-dependent anoxic deterioration of phosphorylated fibres in the temporal arcuate zone, accompanied by glial proliferation. A monkey with spontaneous visual impairment had nerve fibre loss and gliosis with collagenous proliferation in the temporal hemisphere, suggesting glaucomatous neuropathy.
Circulatory interference in the circle of Haller and Zinn caused time-dependent deterioration in the area where anoxic segmental degeneration is associated with pathogenesis of open-angle glaucoma.
Experimental glaucoma; circle of Haller and Zinn; ischaemic optic neuropathy; macaque glaucoma; glaucoma
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