bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accessory oculomotor nuclei in the monkey: Projections and effects of discrete lesions
Authors: Carpenter Malcolm B. , Harbison John W. , Peter Philip 
Published: December 2004

AbstractA study in the monkey was made of the degeneration and effects of lesions in the accessory oculomotor nuclei. Lesions destroyed: (1) the interstitial nucleus (INC), (2) regions lateral and dorsal to the INC, (3) the posterior commissure (PC), and (4) the central gray. Degeneration was studied in Nauta‐Gygax stained sections.Efferent fibers from the INC project: (1) contralaterally, to specific subdivisions of the oculomotor complex (OMC), (2) bilaterally, to the trochlear nuclei (TN), and (3) ipsilaterally, to the medial vestibular nucleus, to certain perihypoglossal nuclei and to the spinal cord. Projections of the INC to the oculomotor complex cross in ventral parts of the PC and project differentially to the dorsal, medial and intermediate cell columns via the contralateral INC and MLF. No fibers from the INC project to the ventral somatic cell columns, the visceral nuclei or the caudal central nucleus of the OMC. Discrete lesions in the INC produce transient head tilt to the opposite side.Unilateral and bilateral lesions of the PC interrupt crossing interstitio‐oculomotor fibers and produce: (1) symmetrical differential degeneration in the OMC and TN similar to that resulting from discrete lesions of the INC, (2) bilateral eyelid retraction, and (3) impairment of vertical gaze, particularly upward gaze. Horizontal gaze and pupillary reflexes were normal.Evidence suggests that relationships between interstitio‐oculomotor fibers and the nuclei of the posterior commissure may underlie neural mechanisms that regulate vertical eye movements.
Axonal bifurcation in the dorsal root ganglion of the cat: A light and electron microscopic study
Authors: Ha Hongchien 
Published: December 2004

AbstractBifurcation of the axon of unipolar neurons in the dorsal root ganglion of the cat has been studied by light and electron microscopy.Osmic acid, Golgi and silver preparations have revealed two types of bifurcation: (1) of myelinated fibers characterized by constriction at the nodal region with peripheral and central branches of equal diameter; (2) of small fibers characterized by a broad triangular expansion at the junctional region with a much thicker peripheral as compared to the central branch. These differences in bifurcation of unmyelinated and myelinated axons can be related to the velocity of conduction in the peripheral nerve and dorsal roots.The ultrastructure of the nodal region at the bifurcation resembles the node of Ranvier of a peripheral nerve fiber. The node of Ranvier at the bifurcation consists of three cells of Schwann and adjacent cells are closely apposed and interdigitated.Neurofilaments and microtubules are prominent structures within the axoplasm at the nodal regions. They group into two streams as the unipolar process bifurcates, entering the peripheral and central branch respectively. At the junctional region within the axoplasm, numerous mitochondria and scattered multivesicular bodies are always observed.
Anatomy of cultured mouse cerebellum. II. Organotypic migration of granule cells demonstrated by silver impregnation of normal and mutant cultures
Authors: Wolf Merrill K. 
Published: December 2004

AbstractThe architecture of presumptive cortex in whole mount Holmes impregnations of cerebellar cortex was reassessed in order to accomplish accurate identification of the granule cell neurons now known to be present there and to seek evidence concerning possible granule cell migration in vitro. The granule cells, although their processes failed to stain by Holmes' method, were recognized as a layer of naked nuclei of characteristic size, shape, and close packing. The gross foliar and sulcal architecture of cortex remained very immature, as it was when explanted. However, a substantial minority of cultures developed microscopic organotypic lamination characteristic of mature cortex, with molecular, granular, and Purkinje cell layers. All organotypically laminated areas showed anomalous twinning of the granular layer. In the reeler mutation of the mouse, the granule cell migration fails, producing an abnormal laminar pattern in adult cerebellum. Cultures of reeler cerebellum, although well developed in other respects, never showed any trace of cortical lamination, proving that the lamination seen in normal cultures must be produced by the migration which fails in reeler but succeeds in normal mice. This is reinforced by the twinning of the granular layer: any reasonable explanation requires organotypic migration of some of all granule cells. The preferred explanation involves specific geometrical deformation of the developing explant by angular rotation of presumptive cortex.
The organization of mechanoreceptive projections in the ventrobasal thalamus of sheep
Authors: Cabral R. J. , Johnson J. I. 
Published: December 2004

AbstractTo determine the arrangement of projections in the somatic sensory nuclear region in the thalamus of sheep, microelectrodes were used to locate and map neural units and groups of units responding to mechanical stimulation of peripheral receptive fields in nine animals anesthetized with Dialurethane. Most of the sensory nuclear region (70–80%) contains projections from ipsilateral oral and perioral fields, Of this volume 16–25% (10–20% of the total) was responsive to stimulation of tissues inside the mouth. The ipsilateral projections are organized differently than are the meager projections from contralateral fields. The contralateral projections are ordered in the same general pattern seen in other mammalian thalami, with caudal fields represented laterally in the nucleus, rostral fields medially, axial fields and maxillary‐nasal fields dorsally, and limbs and mandibular fields ventrally. In the ipsilateral projections, however, mandibular external fields are represented dorsally, and maxillary and nasal fields more ventrally. Still more ventral are projections from the teeth and palate, and most ventral is the representation of the tongue. In all of the ipsilateral projections, the more ipsilateral fields (fathest from the rostral midline) are represented more medially in the thalamus. The exaggerated relative volume of thalamus responding to stimulation of oral and perioral surfaces may reflect the behavioral specialization of a grazing animal.
The in vitro effect of the nerve growth factor on chick embryo spinal ganglia: An electron microscopic evaluation
Authors: Weis Peddrick 
Published: December 2004

AbstractChick embryo spinal ganglia, cultured with and without he nerve growth factor (NGF), were compared by means of electron microscopy with ganglia maintained in vivo for an equal period of time. The results confirm an earlier report that NGF maintains and stimulates only the later‐differentiating mesiodorsal neuroblasts. However, although these cells are stimulated to grow neurites four days prematurely, cytoplasmic maturation does not accompany the outgrowth.The more‐differentiated ventrolateral neuroblasts all show some signs of degeneration after culturing with or without NGF. Those cells which appear normal in the light microscope failed to continue development like their in vivo counterparts and are seen to have myelin figures, marked indentation of the nuclear membrane, and chromatin clumping. Crystalloid structures originally observed by Crain et al. ('64) are demonstrated to be ribosomal crystals and are found only in hyperchromatic degenerated neuroblasts.The satellite cells do not continue to develop in vitro. The process of encapsulatin neuroblasts ceases in both the mesiodorsal and ventrolateral areas of the ganglia. The interrelationship of satellite cell and neuroblast develoment is discussed.
An autoradiographic study of cellular proliferation in degenerating rat optic nerve
Authors: Skoff Robert P. , Vaughn James E. 
Published: December 2004

AbstractYoung adult rats were injected with tritiated thymidine, either before or after removal of one eye, to investigate: (1) the possibility of a leukocytic infiltration into degenerating optic nerve during the first six days following the operation, (2) the origin of the increased number of cells seen in degenerating tissue during the first few weeks after operation, and (3) the possibility of a change in the generation pattern of neuroglial cells in degenerating tissue. In order to investigate the possibility of a leukocytic invasion, rats were injected three times before enucleation to label a high percentage of circulating leukocytes while only labeling a few neuroglial cells. On the operated side of these animals, a small increase in the number of labeled cells above control values occurs only on the third day following enucleation. Another experiment shows that this increase can be explained by a change in the genratiion pattern of the neuroglial cells from two to four days postoperative (2–4 d.p.o.). In degenerating optic nerves, the number of labeled neuroglial cells increase almost tenfold in a 28 hour period from 2–3 d.p.o. While a week is required for a similar increase in normal optic nerve. From 1–3 d.p.o., astrocytes and astrocyte‐like cells constitute 30–50% of the labeled cells observed in a pulse label while the remainder of the labeled cells (unclassifiable neuroglia) cannot be categorized as either astrocytes or oligodendrocytes in light micrographs. Our autoradiographic and morphologic studies indicate neuroglial proliferation during the first two weeks of degeneration can account for the numerical increase of cells in optic nerves undergoing Wallerian degeneration. There is no evidence for an important infiltration of leukocytes and/or pericytes into the optic nerve.
Origin and distribution of the amygdalofugal pathways in the rat: An experimental neuronatomical study
Authors: Leonard Christiana M. , Scott John W. 
Published: December 2004

AbstractThe fields of origin of the amygdalofugal pathways in the albino rat were studied by using the Fink‐Heimer technique to stain degenerating fibers and terminals in brains of animals sacrificed four and seven days after small unilateral lesions of the amygdale. A surprisingly restricted field of origin was found for the supracommissural stria terminalis — the component projecting to the ventromedial nucleus of the hypothalamus Only a lesion in the most posterior part of the cortical nucleus produced degeneration in this pathway. The postcommissural stria terminalis which apparently distributes to the bed nucleus of the stria terminalis and preoptic area originates in a more widespread area including parts of both the basolateral and corticomedial complexes. Although intense terminal degeneration could be seen within the amygdala following all lesions, long fibers projecting into the anterior amygdaloid area, lateral preoptic area and lateral hypothalamus were found only after lesions in which fibers of passage from periamygdaloid cortex could have been interrupted. Convincing evidence, therefore, of a long axon ventral amygdalofugal pathway of the rat was not found in this study.
The olfactory connections of the lateral hypothalamus in the rat, mouse and hamster
Authors: Scott John W. , Leonard Christiana M. 
Published: December 2004

AbstractThe afferent olfactory connections of the lateral hypothalamus of the rat were studied by producing lesions of olfactory cortex and staining for degeneration by the method of Fink and Heimer ('67) and by electropysiological recording of responses to olfactory bulb shock and odor stimulation. Direct connections from olfactory areas were found only in a ventrolateral part of the medial forebrain bundle. In the posterior hypothalamus the olfactory fibers turned dorsally and terminated in a more medial area. The region from which strong olfactory responses could be recorded coincided with the path of degenerating axons. Lesions of the olfactory tuercle of hamsters and mice produced a similar restricted pattern of degeneration.
A mid‐aqueductal ependymal organ in the brain of the hyrax (Procavia capensis)
Authors: Quay W. B. 
Published: December 2004

AbstractSerial sections of the brains of four adult male hyraxes revealed a hitherto undescribed ependymal organ near the middle of the midbrain aqueduct. This structural modification of the dorsal wall of the aqueduct is separate and different from both the subcommissural organ and the posterior collicular recess. It is characterized by: (1) an elaborate system of ridges and crypts, (2) numerous, crowded and distinctive ependymocytes, (3) tissue zonation, and (4) numerous vessels with sleeves of primarily longitudinally arranged glial processes. Comparisons with other ventricular organs and possible functional relations are discussed.
Corticobulbar projections of the marsupial phalanger (Trichosurus vulpecula). I. Projections to the pons and medulla oblongata
Authors: Martin George F. , Megirian David , Roebuck A. 
Published: December 2004

AbstractA total of 27 adult phalangers was employed to investigate the pattern of neocortical projections to the pontine and medullary portions of the brain stem. Lesions restricted to neocortical areas rostral to the orbital sulcus resulted in fiber degeneration which distributed mainly to midline and medial areas of the pontine and medullary reticular formation. The greatest amount of fiber degeneration was located within the superior central nucleus, the nucleus of the pontine raphe, the nucleus pontis centralis oralis and the nucleus pontis centralis caudalis. However, a few degenerating fibers were present within the nucleus gigantocellularis and the magnocellular portion of the medullary raphe. In contrast, lesions which were located just caudal to the orbital sulcus resulted in fiber degeneration chiefly within the more lateral parvocellular reticular formation and within the subnucleus dorsalis of the nucleus medullae oblongatae centralis. In such cases, additional degenerating fibers were present within the dorsal column nuclei and within more medial areas of the reticular formation. In those brains with ventral parietal ablations, degenerating fibers were present within the chief sensory and spinal nuclei of the trigeminal complex and the closely adjacent reticular formation. All of the above neocortical lesions resulted in fiber degeneration within the basilar pontine gray. In those specimens subjected to caudal (striate and peristriate) or ventrocaudal (temporal) lesions, degenerating fibers were present within the basilar pontine gray, but not within other areas of the pons or the medulla oblongata.
Impulse conduction in the shrimp medullated giant fiber with special reference to the structure of functionally excitable areas
Authors: Kusano Kiyoshi , Lavail Matthew M. 
Published: December 2004

AbstractThe external potential field along the functionally isolated medullated giant fiber of the shrimp (Penaeus setiferus) was recorded during impulse conduction using 1 M NaCl‐filled glass capillary electrodes. The giant fiber displays no nodes of Ranvier, yet shows a conduction velocity greater than 90m/second at 20°C. Recordings from most parts of the myelin‐covered giant fiber surface showed only small monophasic positive potentials. However, at the areas of giant fiber‐motor giant fiber synapses and where giant fiber axons branch into abdominal ganglia, a small positivity was followed by a negativity (sink of the action current). The local application of action potential depressants to these areas abolished the negativity and converted it into positivity, and consequently impulse conduction was blocked. Application of the action potential depressants to other areas of the giant fiber did not block impulse conduction. The sink of the action current was not found from the axolemma in the myelin cylinder; this part of the axolemma together with the low resistance gap fluid simply serves as a passive current conductor. Light and electron microscopic studies of the two functionally excitable areas revealed the absence of a myelin sheath in some small areas of both regions. Thus, impulse conduction appears to be saltatory, and these excitable areas function as nodes of Ranvier.
The effects of chronic denervation on spindle discharge patterns and morphology in isolated costocutaneous muscles of garter snakes
Authors: Fukami Y. , Ridge R. M. A. P. 
Published: December 2004

AbstractExperiments on spindles in normal and chronically denervated lateral costocutaneous muscles of snakes are described. The discharge patterns in response to stretch of tonic and phasic spindles are compared between normal spindles and those denervated for various periods of time. The main findings are that spindle function is lost after denervation periods of about 150 hours (the animal being kept at 30°C during the denervation period), and that prior to this (130–140 hours) both tonic and phasic spindles lose their ability to discharges; i.e., they become totally adapting.Electronmicrographs, prepared mainly from material used in the physiological experiments, reveal certain structural changes occurring in parallel with the physiological changes. These consist of increase of neurofilaments, swelling and increasing electron density of mitochondria and appearance of electron‐dense bodies in the sensory ending; these changes occur at times when the spindles are still functioning, though in a modified way. Later the gap between nerve ending and underlying intrafusal fiber is invaded by satellite cell processes. Eventually the nerve endings totally disappear.
Synaptic development in long‐term organized cultures of murine hypothalamus
Authors: Masurovsky Edmund B. , Benitez Helena H. , Murray Margaret R. 
Published: December 2004

AbstractSynapse formation and development were studied in organized cultures of mouse hypothalamic tissues from perinatal stages through a high degree of maturation during several months in vitro. Original explants from fetal and newborn animals were found to contain few definitive primordial synapses (ca. 4 per 10 grid‐squares); newly‐formed synaptic configurations began to appear with regularity in explanted tissues after the third day in vitro. These “immature” synapses contain small clusters of ∼ 300–600 Å agranular vesicles adjoining the presynaptic membrane, are usually devoid of mitochondria, and display diminutive junctional areas as yet little specialized. They are principally axodendritic, and may occur in the company of short, symmetrical, avesicular membrane‐junctions which link neuritic extensions.By about one month in vitro a substantial increase in number of synapses (up to 25/grid square) as well as advances in degree of maturity are evident in the outgrown neuropil; axosomatic synapses are relatively less numerous, as in vivo. Synaptic junction complexes henceforth appear well developed, and the presynaptic portions of boutons terminaux and boutons en passant now contain mitochondria and numerous agranular vesicles (sometimes packed in crystalloid arrays). Glomerulus‐like profiles, synaptic spines displaying typical spine apparatuses, and multifarious synaptic complexes containing a variety of ∼ 500–1,400 Å granular vesicles are also in evidence. The impressive amount of synapse formation and degree of specialization observed here suggests the utility of such cultures as a model system for further hypothalamic investigations.
Topography and numerical distribution of neurons of the thoraco‐lumbar intermediolateral nucleus in the cat
Authors: Henry James L. , Calaresu Franco R. 
Published: December 2004

AbstractSerial transverse sections of the spinal cord of eight adult cats were stained with thionin and examined to determine the topography of the thoraco‐lumbar intermediolateral nucleus (ILN) and the numerical segmental distribution of its neurons. The ILN was found to extend from C8—T1 to L4 and to be located within the lateral horn of the grey matter except in segments C8—T1 and L1—L2 where neurons were observed scattered throughout finger‐like projections of the grey matter. The total number of neurons ranged from 32,790 to 53,340. The mean counts of neurons on the left and right sides were not significantly different. A statistically significant (p < 0.02) difference, however, was demonstrated between the mean counts in four female cats (35,543 ± 1,411) and those in four males (45,765 ± 2,556). The number of ILN neurons was found to vary considerably from segment to segment, with the highest counts occurring in segments T1—T2 and L3—L4. Quantitative estimates of cell sizes were also obtained from one male cat. The modal cross‐sectional area was found to be 290 μ2. The data reported provide a useful map for neurophysiological studies of this nucleus. In addition, the demonstration of a sex difference in the number of ILN neurons suggests that the number of neurons in the mammalian central nervous system may be different in the two sexes.
Control of myelin formation by axon caliber. (With a model of the control mechanism)
Authors: Friede Reinhard L. 
Published: December 2004

AbstractThe relation between the growth of axons and the development of their myelin sheaths was determined in rats for normal, myelinating sciatic nerves, and for an experimental model allowing to retard or accelerate axon growth. Axon caliber was measured, and sheath development was determined from measurements of thickness (light microscopy), from counts of the number of turns of myelin lamellae (electron micrographs), and from the rate of the incorporation of acetate‐H3 into ether‐ethanol extractable lipids. An excellent correlation between changes in sheath thickness and acetate‐H3 incorporation was obtained for all experiments. For the myelinating nerves the changes in the rate of acetate‐H3 incorporation were related specifically to the rate with which new length of myelin leaflet was added to the existing turns of sheath.The rate of axonal growth was manipulated by applying a snug ligature around the nerve by the fourteenth day, allowing the nerve to compress itself by its own growth. Most axons passed the constriction without interruption, but they were markedly hypoplastic distal to the constriction. After removal of the ligature these axons regrew to their normal caliber ranges. Examination of myelin sheath development in this model showed that retardation of axon growth retarded sheath growth, while acceleration of axon growth accelerated sheath growth. Thus, the rate of axon growth appeared to be the factor controlling the rate of myelin formation by the sheath cells.An appendix describes a model consisting of two interrelated feedback mechanisms by which expansion of the axon may directly control the number of turns of myelin lamellae formed by the sheath cell. The model correspons on all points to established features in the fine structure of fibers.