bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of myelination in optic tract of the cat
Authors: Moore Claire L. , Kalil Ronald , Richards Whitman 
Published: May 2005

AbstractThe postnatal development of myelin in the optic nerve and tract of normal and dark reared cats has been studied quantitatively with light and electron microscopy. In the newborn cat few myelinated fibers (3% of the population) are seen in the optic tract. Until the end of the second postnatal week, the total number of myelinated axons in the tract remains low (23%). At this time, however, there is an explosive increase in the rate of myelination and by the end of the fourth postnatal week 80% of the optic tract axons have acquired a myelin sheath. Thereafter, the number of myelinated axons increases gradually, reaching adult levels (100%) at 12 weeks. During the initial period of myelination, the average axon diameter is 0.6 μ for unmyelinated fibers and 1.2 μ for myelinated fibers. Both of these means remain substantially unchanged until myelination is completed, suggesting that initial myelination of an axon is not a continuous process but rather proceeds in a step‐wise manner. Dark rearing appears to have no effect on the initiation of myelination.
Telencephalic projections in two teleost species
Authors: Vanegas Horacio , Ebbesson Sven O. E. 
Published: May 2005

AbstractThe efferent pathways of the telencephalon were investigated in the percomorph Eugerres and the berycomorph Holocentrus. One telencephalic hemisphere was resected by suction and the animals were perfused 7–35 days thereafter. The brains were processed according to a modification (Method 7 in Ebbesson, '70) of the Fink‐Heimer ('67) technique for selective silver impregnation of degenerating axons and terminals.Some fibers emerging from the lesioned telencephalic hemisphere terminate upon the contralateral hemisphere. The large bulk of efferent fibers, however, descends into the ipsilateral diencephalon and gives off the so‐called strio‐tectal bundle (STB) as well as the medial forebrain bundle (MFB). The remaining contingent eventually splits into the so‐called strio‐lobar bundle (SLB) and the lateral forebrain bundle (LFB), but, previous to splitting, it contributes most of the telencephalic projection to the optic tectum in Eugerres, and gives abundant terminals to the ipsilateral nucleus rotundus or prethalamicus in both Eugerres and Holocentrus. The STB conveys all telencephalo‐tectal fibers in Holocentrus, and some of them in Eugerres. Telencephalic efferents terminate ipsilaterally in the middle level of the tectum's stratum griseum centrale; in Holocentrus there is also a small projection to the stratum opticum.The MFB terminates at the caudal hypothalamus and gives terminals all along its course. The LFB also gives terminals all along its course and terminates upon a nucleus located between the midline and the corpus glomerulosum. The SLB spreads out and terminates in the inferior lobe of the hypothalamus.
Prenatal development of central optic pathways in albino rats
Authors: Lund R. D. , Bunt Ann H. 
Published: May 2005

AbstractThe development of the central optic projections in albino rat fetuses has been studied using light and electron microscopic degeneration techniques and the horseradish peroxidase method for demonstrating axonal projections of neurons. The first optic axons to reach the region of the optic chiasm arrive at day 15. By day 16, a substantial optic chiasm is seen and the optic tract can be traced into the epithalamus, having first passed through the ventral lateral geniculate nucleus and a thin lamina of cells which is thought to correspond to part of the future dorsal lateral geniculate nucleus. A growth rate of 80–100 μm per hour is estimated for the fastest growing axons. By day 16‐1/3 the first axons have entered the anterior border of the superior colliculus and in the next day have grown across the entire rostrocaudal extent with the exception of the medial and lateral edges. The optic axons are recognized at day 17 as bundles lying just below the surface, but in older animals they come to lie deeper, as the whole layer of optic innervation broadens. The first synapses to be formed in the superior colliculus (some of them of optic origin) appear on day 17. Subsequently, there is a gradual increase in the number of contacts, the great majority being formed by optic axons.Compared with previous studies on Xenopus and chick, one of the most striking features of the development of the central visual connections in the rat is the relatively long time before the first optic axons reach the brain and the speed with which they innervate the central structures once they have arrived.
Hormone concentrating cells in vocal control and other areas of the brain of the zebra finch (Poephila guttata)
Authors: Arnold Arthur P. , Nottebohm Fernando , Pfaff Donald W. 
Published: May 2005

AbstractUsing the autoradiographic method in the zebra finch (Poephila guttata), areas of the brain were identified which contain cells which accumulate testosterone or its metabolites after intramuscular injection of tritiated testosterone. Among these areas are the caudal nucleus of the hyperstriatum ventrale, nucleus intercollicularis of the midbrain, and the tracheosyringeal portion of the hypoglossal nucleus of the medulla (nXIIts). These three are known to control or influence androgen dependent song and other vocalizations of passeriform birds, and nXIIts is composed of the motoneurons innervating the vocal (syringeal) muscles. Other areas containing hormone‐concentrating cells are the medial preoptic area, nucleus periventricularis magnocellularis of the hypothalamus, dorsal infundibular layers, dorsomedial thalamus, lateral septum, magnocellular nucleus of the anterior neostriatum, periventricular medial neostriatum, nucleus taeniae of the archistriatum, and ventral paleostriatum augmentatum. Accumulation by cells in the preoptic area, hypothalamus, and limbic forebrain is consistent with a general vertebrate pattern of distribution of brain cells which accumulate sex steroids. Some of these same areas may be involved in the control of androgen dependent events such as courtship, copulation, aggression, and feedback regulation of the hypophysis.
Observations on the projections and intrinsic organization of the pigeon optic tectum: An autoradiographic study based on anterograde and retrograde, axonal and dendritic flow
Authors: Hunt S. P. , Künzle H. 
Published: May 2005

AbstractThree aspects of the labelling pattern seen after the injection of 13 different radioactive amino acids into the pigeon optic tectum have been described: The efferent projections of the optic tectum; the specific labelling of two pathways; and the dendritic organisation of tectal layer III neurons based on the retrograde and anterograde movement of label within these dendrites.Discrete injections of tritiated amino acid that involved all or only the superficial tectal layers suggested that layer III gave rise to the massive non‐topographically organised and bilateral projections (fibers crossing within the decussatio supraoptica ventralis) upon the nuclei rotundus, subpraetectalis and interstitio‐praetecto‐subpraetectalis and to the ipsilaterally directed pathways terminating within the nuclei praetectalis, triangularis, subrotundus, dorsolateralis anterior thalami, posteroventralis and ventrolateralis thalami. Layer III neurons may also be the source of efferents to the posterior dorsolateral thalamus (the layer III pathway), the pontine grey and, bilaterally to the reticular formation and of the layer IV or tectal commissural pathway terminating within the contralateral tectal cortex. In contrast projections originating from layer II were generally topographically organised and terminated either within certain of the isthmic nuclei (n. isthmi pars parvocellularis, n. isthmo‐opticus and n. semilunaris) or ran within layer I (layer I pathway) to end in the pretectum (griseum tectale) and ventral thalamus (n. ventrolateralis thalami, n. geniculatus, pars ventralis). A small projection from layer II upon the ipsilateral nucleus rotundus may also be present.Tritiated serine and tyrosine were found to be particularly effective in labelling perikarya as well as axons and terminals. The layer I pathway could be selectively labelled after tectal injections of 3H‐GABA while the cell bodies of Ipc neurons were labelled in a retrograde fashion after tectal injections of 3H‐glycine, serine or alanine.Intrinsic tectal labelling was found by correlation with Golgi material to reflect both anterograde and retrograde transport of label within dendrites of layer III cells. Anterograde movement of label indicated that the terminal portions of layer III cell dendrites ended in an orderly radial arrangement within sublayers IIb and IId, while the retrograde movement of label resulted in the labelling of layer III perikarya outside the injection field.
Organization and morphologies of acetylcholinesterase‐containing neurons in the thalamus and hypothalamus of the rat
Authors: Parent André , Butcher Larry L. 
Published: May 2005

AbstractThe distribution and morphologies of neurons containing acetylcholinesterase (AChE, EC 3.1.1.7) in the thalamus and hypothalamus of the rat were studied by means of a pharmaco‐histochemical technique involving staining for AChE (Karnovsky‐Roots' procedure) at various times after administration of bis‐(l‐methylethyl)phosphorofluoridate. This method enables visualization of individual AChE‐containing neuronal somata and their processes to a degree not possible with other protocols for the enzyme.The strongest AChE activity occurring at the level of the thalamus is found within the small, round to oval, somata of nucleus anterior dorsalis. Most of the intralaminar nuclei, as well as nucleus reticularis, are composed of mediumsized multipolar neurons displaying moderate to strong AChE activity. Moderately stained AChE neurons are also found in pars ventralis of nucleus geniculatus lateralis and in pars lateralis of nucleus habenularis. Most of the neurons of the lateral and posterior thalamic territories, however, are nearly devoid of AChE.At the level of the hypothalamus, the neurons of nuclei supraopticus and paraventricularis show strong AChE activity. The AChE neurons of nucleus supraopticus are surrounded by numerous AChE‐containing processes of some large lateral preoptic area neurons that stain intensely for the enzyme. Numerous intensely stained AChE perikarya occur in the lateral, dorsal, and supramammillary hypothalamic areas. These neurons often possess several AChE‐containing processes. Nuclei arcuatus and ventromedialis consist mainly of neurons displaying a weak to moderate intensity of AChE staining. At the level of the mammillary bodies most neurons show moderate AChE activity except the neuronal somata of nucleus mammillaris lateralis which stain very strongly for the enzyme.
The cerebellofugal projections in the brachium conjunctivum of the rat. II. The ipsilateral and contralateral descending pathways
Authors: Faull R. L. M. 
Published: May 2005

AbstractThe cerebellofugal projections in the ipsilateral and contralateral descending pathways of the brachium conjunctivum (B.C.) in the rat have been investigated in 22 animals using the Fink‐Heimer technique to demonstrate the axonal degeneration resulting from complete B.C. lesions (6), partial B.C. lesions (14) and control lesions dorsal to the B.C. (2). The incidental degeneration resulting from the concomitant involvement of the structures surrounding the B.C. is accounted for in terms of known fiber pathways and from the results in the control experiments.This study confirms Ramón y Cajal's ('03) original observation that cerebellofugal fibers in the B.C. project caudally throughout the length of the hindbrain via both ipsilateral and contralateral descending pathways. The fibers forming the ipsilateral descending pathway proceed ventrally from the B.C. at the level of the trigeminal motor nucleus, turn caudally and terminate within nucleus reticularis parvocellularis (Rpa). In particular, fibers within this pathway terminate densely in two cytoarchitecturally distinct Rpa subnuclei – nucleus “k” (Meessen and Olszewski, '49) and a caudal linear subnucleus – which project to the cerebellum (Faull, '77). The contralateral descending pathway (B.C.de) proceeds caudally from the decussation of the B.C. within the ventromedial region of the magnocellular nuclei of the reticular formation of the pons and medulla. Cerebellofugal fibers of the B.C.de terminate in a distinctive pattern within precerebellar brainstem nuclei: densely throughout the middle third of nucleus reticularis tegmenti pontis; in a longitudinal zone of each of the three pontine gray subnuclei; in the principal and dorsal accessory nuclei of the inferior olive; and sparsely within nucleus reticularis paramedianus. Fibers in the B.C.de also terminate within the magnocellular nuclei of the reticular formation, principally the nuclei reticularis pontis oralis and caudalis.
A morphological study of the axons and recurrent axon collaterals of cat sciatic α‐motoneurons after intracellular staining with horseradish peroxidase
Authors: Cullheim S. , Kellerth J.‐O. 
Published: May 2005

AbstractUtilizing the centrifugal neuronal transport of intracellularly injected horseradish peroxidase (HRP), we have performed a light microscopic (LM) investigation of the intramedullary parts of the axons and axon collaterals of sciatic α‐motoneurons in the adult cat.The intramedullary parts of the α‐motor axons had comparatively short internodes (down to 75 μm) and were thinner than reported in earlier studies on the ventral root. Positive correlations were obtained when relating nodal diameters (2.8–7.8 μm) or the mean diameters of the motor axons in the white matter (4.4–9.0 μm) to the diameters of the initial axonal segments (2.3–4.9 μm).Eighty percent of the motor axons gave off one to five collaterals. There was no correlation between the numbers of collaterals and the lengths of the parent motor axons in the gray matter. The branching patterns of the axon collaterals showed considerable variation and the number of end branches from a single collateral ranged between 1 and 39. The rostro‐caudal distribution of the collateral end branches was arranged symmetrically within a narrow space (± 300 μm) around the origins of the first order collaterals.Outbulgings of the motor axon collaterals, interpreted as synaptic terminals, were found along (59%) or at the ends (41%) of the collateral branches, and were located 200–700 μm away from the origin of the first order collateral. No characteristic LM feature of the outbulgings was distinguished.
Projections of the superior cerebellar peduncle in rats and the development of new connections in response to neonatal hemicerebellectomy
Authors: Castro Anthony J. 
Published: May 2005

AbstractThe normal distribution pattern of cerebellar efferents was determined using the Fink‐Heimer technique in adult rats that sustained stereotaxic transection of the superior cerebellar peduncle. This pattern was found to be essentially similar to earlier studies and corroborated more recent reports of projections to the pontine gray and inferior olivary nuclei.Comparisons were made to a second group of animals that underwent neonatal hemicerebellectomy in addition to adult transection of the contralateral superior cerebellar peduncle. Abnormal projections to the ipsilateral red nucleus and ventral thalamus were observed in addition to evidence suggestive of axonal sprouting within the oculomotor complex. These animals also demonstrated an absence of cells in the pontine gray and inferior olive on the side contralateral to the hemicerebellectomy and in the lateral reticular and lateral cuneate nuclei on the ipsilateral side.
The cochlear nerve in the cat: Topography, cochleotopy, and fiber spectrum
Authors: Arnesen Atle Rønning , Osen Kirsten Kjelsberg 
Published: May 2005

AbstractThe topographical and cytological features of the cochlear nerve in normal adult cats were studied by microdissection, light microscopy, transmission and scanning electron microscopy. The 2‐mm long cochlear nerve trunk is situated within the internal acoustic meatus. The nerve is wrapped like a roll with the more basal fibers situated peripheral to the more apical ones. The fibers are fasciculated according to their target in the cochlea and follow a helical course with the sharpest spiralling in the distal portion of the fiber. Apical and basal coil fibers are of approximately the same length measured from the spiral lamina to the rostral border of the anteroventral cochlear nucleus. The nerve contains about 90% thick, myelinated fibers, about 10% unmyelinated axons, and a few thin, but heavily myelinated axons. The first group shows a unimodal distribution of axonal diameters, with a gradual increase in average diameter from basal to apical coil fibers. The number of axonal microtubules and neurofilaments have a high linear correlation to axonal circumference without principal cochleotopic differences. The myelin sheaths are thicker and the internodal segments shorter than expected from similarly sized peripheral fibers in rodents. The possible nature and origin of the three fiber categories are discussed.
Association and commissural fiber systems of the olfactory cortex of the rat. I. Systems originating in the piriform cortex and adjacent areas
Authors: Haberly Lewis B. , Price Joseph L. 
Published: May 2005

AbstractThe association and commissural fiber systems arising in the olfactory cortical areas caudal to the olfactory peduncle (the piriform cortex, nucleus of the lateral olfactory tract, anterior cortical nucleus of the amygdala, periamygdaloid cortex and entorhinal cortex) have been studied utilizing horseradish peroxidase as both an anterograde and a retrograde axonal tracer.In the piriform cortex two sublaminae within layer II (IIa and IIb) and layer III have been found to give rise to distinctly different projections. Retrograde cell labeling experiments indicate that the association fiber projection from layer IIb is predominantly caudally directed, while the projection from layer III is predominantly rostrally directed. Cells in layer IIa project heavily to areas both caudal and rostral to the piriform cortex. The commissural fibers from the piriform cortex are largely restricted in their origin to layer IIb of the anterior part of the piriform cortex and in their termination on the contralateral side to the posterior part of the piriform cortex and adjacent olfactory cortical areas. A projection to the olfactory bulb has also been found to arise from cells in layers IIb and III of the ipsilateral piriform cortex, but not in layer IIa.In addition to those from the piriform cortex, association projections have also been found from other olfactory cortical areas. The nucleus of the lateral olfactory tract has a heavy bilateral projection to the medial part of the anterior piriform cortex and the lateral part of the olfactory tubercle (as well as a lighter projection to the olfactory bulb); both the anterior cortical nucleus of the amygdala and the periamygdaloid cortex project ipsilaterally to several olfactory cortical areas. The entorhinal cortex has been found to project to the medial parts of the olfactory tubercle and the olfactory peduncle. The olfactory tubercle is the only olfactory cortical area from which no association fiber systems (instrinsic or extrinsic) have been found to originate.A broad topographic organization exists in the distribution of the fibers from several of the olfactory areas. This is most obvious in the anterior part of the olfactory cortex, in which fibers from the more rostral areas (the anterior olfactory nucleus and the anterior piriform cortex) terminate in regions near the lateral olfactory tract, while those from more caudal areas (the posterior piriform cortex and the entorhinal cortex) terminate in areas further removed, both laterally and medially, from the tract.Projections to olfactory areas from the hypothalamus, thalamus, diagonal band, and biogenic amine cell groups have been briefly described.
Quantitative analysis of the opossum's optic nerve: An electron microscope study
Authors: Hokoç J. N. , Oswaldo‐Cruz Ė. 
Published: May 2005

AbstractAn electron microscope examination of the optic nerve of the opossum, Didelphis marsupialis aurita, indicates a total count of 74,700 fibers of which approximately 20% are unmyelinated. The diameters of myelinated fibers ranged from 0.5–7.0 μm (mode at 1.25 μm) and those of the unmyelinated fibers ranged from 0.25–2.25 μm (mode at 0.75 μm). Myelinated and unmyelinated fibers are uniformly distributed throughout the nerve. Myelin sheath structure is similar to that described in other species and are formed by 2 to 17 myelin rings (mode at 6). There is a good correlation (r = 0.92) between axon and myelin areas. The relation between myelin thickness and axons diameter shows a wide distribution with a peak at 0.77.
Prenatal development of the cerebellar system in the rat. II. Cytogenesis and histogenesis of the inferior olive, pontine gray, and the precerebellar reticular nuclei
Authors: Altman Joseph , Bayer Shirley A. 
Published: May 2005

AbstractAspects of the prenatal development of the inferior olive, lateral reticular nucleus, nucleus reticularis tegmenti pontis, and of the pontine gray were investigated in the rat. The material used was the same as in the preceding study of cerebellar development, including histological preparations from normal and x‐irradiated embryos at daily intervals (days E13 to E22), and autoradiograms from adult rats injected with two successive doses of 3H‐thymidine on overlapping days from days E13 + 14 on.Neurons of the inferior olive form on days E13 and 14: those settling rostrally in the principal nucleus somewhat ahead of those settling in the medial accessory nucleus caudally. The olivary neurons are generated in the neuroepithelium of the lateral recess of the fourth ventricle, migrate ventrally by way of the olivary migratory stream, split into two branches and provide cells to the olivary complex from its lateral and medial aspect. The migrating cells are differentiated, radioresistant elements. It was postulated that since the olivary migratory path and the course of olivary fibers (the inferior cerebellar peduncle) are on the same trajectory, climbing fibers could reach the surface of the cerebellum before the arrival of the radially migrating Purkinje cells.Neurons of the lateral reticular nucleus form predominantly on days E13 and 14, of the nucleus reticularis tegmenti pontis on days E15–17, and of the pontine gray on days E17–19. The pontine neurons originate several days after but at the same site as the olivary neurons. The cells migrating in the pontine migratory stream are undifferentiated elements and follow a course different to that of their prospective axons in the middle cerebellar peduncle. The earliest forming pontine neurons settle near the pyramidal tract, the later arriving cells form cap‐like shells around this core. Axonogenesis of pontine cells begins after the settling of the perikarya on day E19. The middle cerebellar peduncle appeared to approach the cerebellum on day E22, suggesting that pontine mossy fibers do not establish contact with cerebellar elements before the perinatal period, by which time the external germinal layer and the Purkinje cells have formed a cortical mantle over the entire cerebellum.In an attempt to correlate the chronology of cytogenesis in some of the precerebellar nuclei with cell production and maturation in the cerebellum, it was hypothesized that mossy fibers of reticular origin exert influence on Purkinje cell dendrites in the lower parts of the molecular layer, whereas mossy fibers of pontine origin influence the upper parts of Purkinje cell dendrites. Reference is made to behavioral results indicating the mediation of dissociable functions by elements of the lower and upper molecular layer.