The organization of spinal cord motor columns innervating 18 selected macaque forelimb muscles was studied with the technique of retrograde transport of horseradish peroxidase. The reliability of the method was evaluated in the cat hindlimb.Motor columns innervating forearm muscles with similar actions on the hand appear to overlap in the anterior horn. Extensor motoneurons are generally positioned ventral and/or lateral to flexor motoneurons. Motoneurons controlling hand movement are located primarily in segments C8 and Tl.Motoneurons that innervate individual muscles are arranged in rostrocaudal columns in the anterior horn of the spinal cord. The segmental localization of motor columns innervating primate forelimb muscles was originally described by Sherrington (1898) in studies involving stimulation of individual ventral nerve roots. Although the somatotopic organization of motor columns in the anterior horn has been reported for the cat lumbosacral cord (Romanes, 1951;Burke et al., 1977;Sato et al., 1978), the only topographical data available for the monkey cervical cord relate to the distribution of motoneurons that contribute to individual ventral roots (Sprague, 1948) and major peripheral nerves (Reed, 1940).In the present study we sought to determine both the segmental and topographical organization of individual motor columns involved in controlling hand movement in the monkey. The retrograde transport of horseradish peroxidase (HRP) from selected muscles to motoneurons was used (Burke et al., 1977;Sato et al., 1978;Richmond et al., 1978; Matusda et al., 1978;Landmesser, 1978). Materials and MethodsThe studies were carried out in 10 Macaca mulatta and 4 M. fuscicularis monkeys of both sexes (2.9 to 4.2 kg). The reliability of the method was first evaluated in the cat.Injection barbiturate anesthesia the desired muscle was exposed and, with the use of an operating microscope, was carefully dissected from surrounding muscles. Care was taken to preserve the neurovascular pedicle. Muscles were identified by anatomic position, tendinous insertion, and when necessary, by electrical stimulation of the muscle (Hartman and Straus, 1933). The muscles were injected from a 27 gauge needle over 15 min at multiple sites with a saline solution of HRP (25,000 units/ml, Sigma HRP type VI, St. Louis, MO). Sufficient HRP was injected to render each muscle a dark brown color. To prevent the spread of HRP to adjacent muscles, Silastic and cotton barriers were positioned between the muscle to be injected and the surrounding muscle groups. The tissues surrounding the injected muscle were irrigated frequently with normal saline after the injection. By 3 hr, the injected muscle had returned to a more normal appearance and visible HRP leakage had stopped. Less frequent irrigation was continued for approximately 12 hr postinjection and the Silastic and cotton barriers remained in place for the duration of the experiment. Study of the spinal cord. After 48 hr under anesthesia, each animal was heparinized and perfused th...
Early climbing fiber metamorphosis has been studied in 250 Golgi preparations of 5-12 day postnatal rat cerebellum, and in less numerous 12-18 day ones. EM controls were provided for the early phase covering maturation of Purkinje cytoplasm, status of axonal neuropil, and synapses between the evanescent nid structure and Purkinje soma membrane.Ramon y Cajal (1890, 'll), Athias (1897) and others have contributed extensively to climbing fiber histogenesis. Our results are confirmatory but support more varied developmental detail including that of axonal collateralization within the granular layer, all of which may not persist to maturity. Distinguishing characteristics of climbing fibers are recognized early in histogenesis, including varicosities, redundancies in course, and a manner of branching called cross-over. The curvaceous path a climbing fiber pursues across the granular layer can be corrected at the ganglionic level by a horizontal segment having length equivalent to the offset. These and other redundancies may straighten out with areal expansion of cortical surface as compared to the restricted white matter base.While supporting multiple innervation of nids by local collateralizations proceeding from stem axons in white matter, the study does not preclude a one to one relationship between adult climbing fiber and Purkinje cell as basic design. Unknown factors are the relative amounts of local collateralization proceeding from several versus a single axon stem, and the extent to which branches are issued from a single fiber to different folia.
Cerebellar cortex was studied in 100 rats and other animals, 15-30 days old, using Golgi, intravitam methylene blue, and ultrastructural methods. Marchi and Nauta provided certain controls. Degeneration of afferent terminals was sought following lesions of pons and olive.In normal material, emphasis was upon the chanqing field relations between folial summit, side wall, and sulcus. Many previous findings of Fox, Ramon y Cajal and Snider were confirmed, and the effort made to reconcile departures from characteristic axonal and dendritic configuration with cytoarchitectonic pattern. Mossy and climbing terminals were examined in normal and degenerated states, using Golgi and ultrastructural material. Climbing fibers in Golgi are described in detail, including variations in course and sites of branchings. Mossy degeneration was found 3-5 days after lesions of both pons and olive. The clearest evidence thereof was provided in ultrastructural material. Minor evidences of degeneration were also found in climbing fiber strands in both materials, but no gross degeneration was encountered. Corresponding Golgi material was used for visualizing intact fibers in the face of adequate lesions.Ultrastructure also provided evidence concerning the axon cap surround, the initial segment of the Purkinje axon, comparison with these segmests in other cell types, and cross-identification of synapses between axon types and the different cell profiles of Golgi material.
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