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doi: 10.1002/cne.901490102pmid: 4700512
The neuronal population of the PAG consists of relatively small cells, ranging from approximately 8 μ to 30 μ in diameter. These neurons are of three different types and are classified as I, II, and III for the sake of convenience. Each class aggregates in certain areas of the central gray to form subdivisions distinguishable by differing neuronal distributions as well as by cellular characteristics. Class I neurons are small, spindle shaped cells that stain darkly with cresyl violet. They aggregate loosely around the cerebral aqueduct, thus forming the comparatively acellular inner ring of the PAG, the nucleus medialis. The class II cells are also small and darkly staining, but they are fusiform to spherical in shape. These cells cluster more closely and are surrounded by many glial cells. They congregate in the area dorsal to the cerebral aqueduct to form the nucleus dorsalis. The largest cells of the PAG, the class III neurons are spherical or tringular in shape and stain lightly due to their sparse Nissl substance. Frequently glial cells abut the perikaryon of these neurons. They aggregate very closely to form the dense cellular outer portion of the PAG. This mantle of cells is called the nucleus lateralis.
doi: 10.1002/cne.901490103pmid: 4633682
Retrograde degeneration in thalamus was studied in eight Macaque monkeys following resection of basomedial temporal cortex. In addition to its known projection to the posterior cingulate region, nucleus lateralis dorsalis (LD) projects, perhaps via the fornix, to the parahippocampal gyrus. Convexal temporal neocortex receives fibers from the medial pulvinar (PM). Nucleus lateralis posterior (LP) may project to cortex intervening between the projection fields for LD and PM. A stereotactic lesion in fornix of one animal demonstrates corticothalamic projection to LD, LP and to a lesser extent to PM, AV, AM, and AD.
Ling, E. A.; Paterson, Jean A.; Privat, A.; Mori, S.; Leblond, C. P.
doi: 10.1002/cne.901490104pmid: 4121705
The staining of half‐micron thick Epon sections with toluidine blue provides a reliable method for the identification of glial cells. The diagnostic features of these cells observed in the corpus callosum of one‐month‐old rats are as follows: (1) Astrocytes have a very pale nucleus and cytoplasm; the nuclear envelope is sharply outlined by a thin chromatin lining with occasional chromatin beads; (2) Microglia have a small nucleus in which large, dark chromatin masses contrast with the nucleoplasm; the nucleus is round or elongated, and may be somewhat angular. The pericytes, which have a similar but usually crescentic nucleus, may be related to microglia. (3) Oligodendrocytes vary from pale to very dense and may be arbitrarily classified into three subgroups: The light oligodendrocytes are large pale cells with round to ovoid nucleus containing a prominent nucleolus and little or no condensed chromatin; the cytoplasm is extensive and appears pale, although less so than the nucleus. The medium shade oligodendrocytes are smaller cells that have an ovoid nucleus carrying small chromatin clumps and appearing moderately basophilic throughout; the cytoplasm is less extensive and somewhat darker than in the “light” subgroup. The dark oligodendrocytes are usually smaller than medium shade cells and often have an indented or angular nucleus with large chromatin masses; both nucleoplasm and cytoplasm are densely stained; the cytoplasm is often scanty and accumulated on one side of the nucleus.
doi: 10.1002/cne.901490105pmid: 4121706
Semithin Epon sections stained with toluidine blue were used to enumerate astrocytes, microglia, the three subtypes of oligodendrocytes, and cells referred to as free subependymal cells, in the corpus callosum and cerebral cortex of male Sherman rats of various ages. The period covered extended from a few days before weaning (3/4 month of age) until the time when growth became negligible (5 months of age).
Paterson, Jean A.; Privat, A.; Ling, E. A.; Leblond, C. P.
doi: 10.1002/cne.901490106pmid: 4573360
Strong labeling of the cells in the subependymal layer was produced by stereotaxic injection of 5 μCi of 3H‐thymidine into the left lateral ventricle of the brain of one and a quarter month old rats weighing about 100 gm. These animals were sacrificed by glutaraldehyde perfusion from two hours to 21 days later. Blocks of corpus callosum with adjacent subependymal and ependymal layers were excised from the injected and non‐injected sides, and embedded in Epon; 0.5 μ thick sections were radioautographed and stained with toluidine blue.
doi: 10.1002/cne.901490107pmid: 4700511
The topographic organization of spinal afferents to the lateral reticular nucleus (LRN) has been reexamined in 34 adult cats. Two modifications of the Nauta technique were used to show secondary terminal degeneration resulting from circumscribed lesions at various levels of the spinal cord. The results demonstrate that the “inner segment” of LRN corresponding roughly to Brodal's magnocellular portion, receives fibers from spinal segments C1–D3, while the “outer segment” corresponding approximately to Brodal's parvocellular protion receives fibers from spinal levels below L3. The “middle segment” — a transitional zone between the two former portions — represents the spinal segments D4–L3. The ascending fibers terminate predominantly on the ipsilateral side; only few degenerated elements are noted within the contralateral nucleus. The subtrigeminal portion does not seem to receive afferent fibers from the spinal cord. This finding raises the question of nomenclature, which is briefly discussed in the light of the classical “nucleus funiculi lateralis” concept. Finally, the present data are consistent with electrophysiological data of Oscarsson, Rosén and collaborators according to which LRN represents spinal levels of convergent inputs from large as well as bilateral receptive fields rather than somatotopically arranged projections from peripheral sense organs.
Ödkvist, L. M.; Rubin, A. M.; Schwarz, D. W. F.; Fredrickson, J. M.
doi: 10.1002/cne.901490108pmid: 4633681
The neocortical surface of the rabbit's brain was explored by macroelectrodes with isolated electrical stimulation of the vestibular nerve. Surface positive evoked potentials were recorded within the first somatosensory (SI) forelimb field. Negative field potentials in middle cortical layers were only found in a small area within the rostral part of this field. The rabbit's vestibular field is compared with those of rodents, carnivores and primates.
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