bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atlas of estrogen‐concentrating cells in the central nervous system of the squirrel monkey
Authors: Keefer Donald A. , Stumpf Walter E. 
Published: January 2005

AbstractEstrogen is concentrated within cellular nuclei in discrete regions of the monkey brain 30 and 60 minutes following intravenous injection of [3] estradiol. Chromatographic data is provided to suggest that most of the localized estrogen is in the form of estradiol with lesser amounts of estrone and estriol. Three “major” areas of estrogen accumulation include: (1) preopticostrial accumulation: n. preopticus medialis — n. interstitialis striae terminalis, (2) basal hypothalamic accumulation: n. infundibularis — n. ventromedialis — n. premammillaris ventralis, and (3) the amygdaloid accumulation. Several “minor” areas of estrogen accumulation include the tuberculum olfactorium, insulae Calleja, n. triangularis septi, a. hypothalamica anterior, n. anterior hypothalami, n. paraventricularis, n. supraopticus, n. periventricularis and the substantia grisea centralis. The neocortex, rhombencephalon and spinal cord are essentially unlabeled. The major areas of accumulation are similar in several other mammalian and avian species while these, and some minor areas of accumulation, have been shown in neuroanatomical studies to be interconnected by several pathways, especially the stria terminalis. Lesion, implant, stimulation, recording and morphometric studies, in several species, support the concept that this arrangement provides a neuroanatomical substrate which would allow the integration of the various facets of the neuroendocrine reproductive response.
Neural intersegmental connection in the spinal root and ganglion region of the rat
Authors: Jacob M. , Weddell G. 
Published: January 2005

AbstractA study has been made of the macroscopic, microscopic and electron‐microscopical appearance of intersegmental neural connections in the rat. Macroscopically, spinal roots and ganglia of adjacent segments were frequently observed to be linked by discrete, slender strands, mainly in the lumbosacral region where the roots are long. When examined under the light microscope, even the smallest was found to contain as many as 72 myelinated fibres with a range of diameters between 1.5–14 μm. They were commonly accompanied by blood vessels. Connections, when present, contributed to as much as 6–28% of the total number of myelinated axons in dorsal roots.Under the electron microscope, links between dorsal roots, or between dorsal roots and adjacent ganglia, contained unmyelinated fibres comparable in numbers to those found in the dorsal roots themselves. In links between ventral roots and ganglia the numbers of unmyelinated fibres proportionally exceeded those found in ventral roots.The presence of these connections may account for the reported finding of undamaged nerve fibres in the dorsal roots after dorsal root sectioning or ganglionectomy and in the ventral roots after ventral root sectioning.
The distribution of the olfactory tracts in the bullhead catfish, Lctalurus nebulosus
Authors: Finger Thomas E. 
Published: January 2005

AbstractUsing degeneration staining methods, central projections of the olfactory tracts in the bullhead catfish, Ictalurus nebulosus were studied. Separate lesions were made of the lateral and medial olfactory tracts in an attempt to separate their zones of projection. Three major terminal fields were found: lateral, medial and central‐posterior complex. Two additional minor projections were seen: interbulbar and hypothalamic.The lateral division of the olfactory tract terminates in lateral, central and hypothalamic terminal fields. The medial tract projects to lateral, medial, posterior and hypothalamic fields. All terminal fields were found bilaterally; the lateral tract partly crossing in both the anterior and habenular commissures and the medial tract in only the anterior commissure. A small interbulbar commissure was also found to contain medial tract fibers.Evidence is given to show that the anterior olfactory nucleus, if present in catfish, may be located within the olfactory bulb itself. Similarities between mammalian and teleost olfactory systems are also discussed.
Visual projections to the optic tecta in Xenopus after partial extirpation of the embryonic eye
Authors: Berman Nancy , Hunt R. K. 
Published: January 2005

AbstractThe temporal, nasal or dorsal half (40–60%) of the eye primordium was excised in Xenopus frog embryos stage 25/26 (optic vesicle), 31/32 (optic cup) or 38 ± 1 (early larval eye). The residual nasal (NF) or temporal (TF) or ventral (VF) fragment gradually rounded‐up to form a grossly normal eye of normal or reduced size. Electrophysiologic analysis of the visuotectal projection after metamorphosis showed that (independent of stage of surgery and final eye size) most eyes of each type generated normal retinotectal maps (orderly and continuous retinotopic projection across the entire tectum). A minority of NF eyes generated double‐nasal compound maps, in which nasal and temporal halves of the adult retina projected as mirror images (of the nasal pattern) over the whole tectum. A minority of TF eyes generated double‐temporal compound maps, while a minority of VF eyes generated double‐ventral compound maps. Respectively, these compound maps simulated those generated by NN, TT or VV “compound‐eyes” prepared by fusing two nasal half eyes, or two temporal half eyes, or two ventral half eyes. The incidence of double‐maps was lowest in TF eyes at all stages, and after stage 25/26 surgery in all eye types. Lure tests and post‐synaptic recording confirmed that these eyes formed functional retinotectal synapses, and that the (presynaptic) map accurately mirrored the connectivity pattern. The results are considered in terms of (1) the patterning of locus specificities in the retinal ganglion cell population, (2) embryonic “regulation” and “reduplication” in non‐neural systems, and (3) alternative mechanisms by which partial extirpation might modify the deployment or expression of ganglion cell locus specificities to produce the retinotectal connectivity patterns we observed.
The visual connections of the adult flatfish, Achirus lineatus
Authors: Gulley R. L. , Cochran M. , Ebbesson S. O. E. 
Published: January 2005

AbstractMetamorphosis in the flatfish is characterized by the migration of one eye around the dorsal surface of the head to a position adjacent to the other eye on the new top side of the animal. The visual connections of the adult flatfish, Achirus lineatus, were examined. Either the migrating or non‐migrating eye was removed and the animal allowed to survive for one to three weeks. Alternate sections of the brain were stained by a modification of the Fink‐Heimer technique, or with cresyl violet. The diencephalc visual connections of the flatfish were similar to those of other teleosts with contralateral projections to the nuclei corticalis, dorsomedialis thalmi, pretectalis, and the corpus geniculatum laterale. The distribution of the retinal efferents to the optic tectum is unique in the flatfish. In the medial one‐third of the tectum, terminal degeneration was found in three bands in the stratum opticum (SO) and the stratum griseum et fibrosum superficiale (sgfs). In the middle part of the tectum, two bands of degeneration remained over the sgfs. The lateral part of the tectum has only a very small amount of degeneration distributed randomly in scattered clusters over the deep SO and superficial sgfs. The Nissl preparations also reflected the differences between the medial and lateral parts of the tectum. Distinct layer was lacking in the medial tectum with a conspicuously absent large cell layer in the stratum griseum centrale (sgc), In contrast, the lateral tectum had a typical tectal stratification. Most notable were the large neurons of the sgc.
Developmental changes in olfactory bulb projections revealed by degeneration argyrophilia
Authors: Leonard Christiana M. 
Published: January 2005

AbstractThe maturation of the main and accessory olfactory bulb projections to the ventral forebrain of the golden hamster has been traced by using the Fink‐Heimer silver technique to stain degenerating axons and terminal arborizations after bulbectomy at different ages between birth and 33 days. In the youngest pups, long‐lasting degeneration argyrophilia (LLDA) is found in two regions of prepiriform cortex: at the level of the rostral tubercle and rostral amygdala. By five days of age the caudal region exhibiting a long‐lasting degeneration reaction extends from the middle of the olfactory tubercle, to the middle of the amygdala. The olfactory tubercle, medial and cortical amygdala and entorhinal cortex subsequently develop substantial LLDA at ages varying between 9 and 13 days.In a previous study (Leonard, '74b) the onset of LLDA in optic tract terminals in the superior colliculus was found to coincide with the age of eye opening and the onset of a stage of rapid synapse formation. Since different olfactory responses appear at different times during the golden hamster pup's first two weeks of postnatal life, it seems possible that the onset of LLDA in different regions of the olfactory projection at different ages may be related to the onset of different specific olfactory functions.
The projections of cells in different layers of the cat's visual cortex
Authors: Gilbert C. D. , Kelly J. P. 
Published: January 2005

AbstractThe projection of cells in different layers of several cortical visual areas in the cat were studied using the method of retrograde transport of horseradish peroxidase. Injections of the enzyme were made through a recording micropipette, making it possible to localize the injection site by physiological criteria. We found that layer VI cells projected to the lateral geniculate nucleus, while a distinct population of cells in layer V projected to the superior colliculus. Cells in layers II and III were the major sources of ipsilateral cortico‐cortical connections. This pattern of projection was consistent from one visual area to another. Pyramidal cells appeared to be the source of cortico‐geniculate, cortico‐collicular and cortico‐cortical projections. The proportion of cells within a layer that terminated in a given site varied from layer to layer: apparently all of the large pyramids in layer V had terminals in the superior colliculus, about half of the pyramids in layer VI had terminals in the lateral geniculate nucleus, while only a small proportion of the pyramids in layers II and III had terminals in any single cortical area. The results indicated a remarkable specificity in the projections of the cortical layers.The cortical connections of the different cell types in layers A and A1 of the lateral geniculate nucleus were also examined: the cells that projected to area 17 were much more numerous and were on the average smaller than those that projected to area 18. Projections to the cortex were also found from the pulvinar, the medial interlaminar nucleus and the posterior nucleus. Direct connections were observed to the lateral geniculate nucleus from several midbrain reticular nuclei. Finally, projections were found to the superior colliculus from the zona incerta, the reticular nucleus of the thalamus and the ventral lateral geniculate nucleus.
Axonal projections and connections of the principal sensory trigeminal nucleus in the monkey
Authors: Smith Ronald L. 
Published: January 2005

AbstractTo date, anatomical studies of ascending principal sensory trigeminal nuclear (PrV) axons in the monkey have been restricted to few incomplete investigations utilizing the Marchi method. In the present study total or partial unilateral stereotaxic lesions of PrV were made in cebus and rhesus monkeys and analyzed with the aid of a variety of Nauta silver impregnation techniques applied to frozen sections.Analysis of the fiber degeneration emanating from PrV lesions indicates that PrV fibers from an ascending system composed of two distinct components. Most PrV axons project ventromedially from PrV through the ventral pontine tegmentum and gradually decussate across the midline in the mesencephalic tegmentum up to the level of the caudal pole of nucleus interpeduncularis. These decussated fibers form the trigeminal lemniscus, which courses dorsomedial to the medial lemniscus during its ascent into the diencephalon. A few whorls of preterminal fiber degeneration separating from the trigeminal lemniscus first appear in the magnocellular area of the thalamus medial to the medial geniculate body. The lemniscal PrV axons terminate densely throughout most, but not all, of the magnocellular part of nucleus ventralis posteromedialis (VPM) contralateral to the side of their origin. Some collateral‐like fibers from the trigeminal lemniscus also were observed ending in the ventral segment of the zona incerta. Other axons, arising chiefly from the dorsal one‐third of PrV, form a smaller ipsilateral trigeminothalamic projection. These fibers all remain on the side of their origin and terminate consistently in a discrete dorsomedial paralaminar portion of VPM that does not receive lemniscal PrV connections.A commissural fiber system at the pontine level connects parvicellular reticular cells with their counterparts and the motor trigeminal nucleus of the opposite side. These interconnections appear to provide an anatomical link for the integration of bilateral trigeminal sensory information and motor function.
Functional role of efferents to the avian retina. II. Effects of reversible cooling of the isthmo‐optic nucleus
Authors: Pearlman Alan L. , Hughes Charles P. 
Published: January 2005

AbstractEfferents to the retina in the bird arise in the isthmo‐optic nucleus of the caudal midbrain, and terminate on amacrine cells in the retina. The functional role of these efferents was studied by determining the receptive field properties of 107 optic tract fibers in the lightly anesthetized adult pigeon, and quantitating their responses to specific moving stimuli. While the recording from these fibers continued, the isthmo‐optic nucleus was cooled by a thermoelectric cooling probe, and the response properties of the cells redetermined. Recording was maintained in half of the units long enough to observe recovery from cooling, and in several units the entire procedure was repeated. In 77 of the 107 units, responsiveness to all stimuli was decreased by removing efferent influences, whereas specific receptive field properties such as motion sensitivity or directionality were not altered. All of the major receptive field types were affected in a similar fashion, irrespective of their position in the visual field. Responses to stimuli that did not involve the antagonistic surround were similarly affected by removal of the efferents, as were units with both weak and strong antagonistic surrounds.Efferents exert their influence on retinal ganglion cells by way of the amacrine cells on which they terminate. Data available on amacrines in Necturus indicates that they are inhibitory to ganglion cells. If amacrines have a similar role in the pigeon, then it may be stated that decreased activity in the centrifugal fibers leads to enhanced inhibition throughout the receptive fields of ganglion cells, and increased activity in the efferents produces disinhibition.
Increases in collateral axonal growth rostral to a thoracic hemisection in neonatal and weanling rat
Authors: Prendergast Jocelyn , Stelzner Dennis J. 
Published: January 2005

AbstractThe spinal cords of newborn and weanling rats were hemisected at the mid‐thoracic level. Control studies revealed that Fink‐Heimer positive debris was absent in the gray matter at three months postoperative. The remaining animals were given a second lesion, a high cervical spinal hemisection, at five to seven months after the original thoracic hemisection. The pattern of degeneration rostral to the thoracic lesion was compared with similar regions of the spinal cord from animals receiving only a cervical hemisection at the adult stage.In neither experimental group of doubly hemisected rats was there any degeneration observed below the thoracic lesion site, even though no glial or connective tissue scar had formed in animals originally operated at birth. Thus no regeneration had occurred. At least one segment above the initial hemisection: 1. the majority of degenerating axons were localized toward the lateral edge of the spinal cord, especially in the doubly lesioned neonatal group; 2. the area of ipsilateral white matter was reduced more in the neonatal than the weanling operates; 3. there was an upward shift in axonal diameter of ipsilateral fibers in both the region of the rubrospinal tract and the ventrolateral portion of the lateral funiculus of the doubly hemisected rats when compared with the cervically lesioned controls; 4. a significantly greater amount of degeneration was present in lamina VII of Rexed in both the neonatal and weanling experimental operates (p < 0.05 weanling; p < 0.001 neonate); 5. no mean difference in area was seen between the ipsilateral and contralateral gray matter in any group for the segments of the spinal cord in which the judgements and measurements were taken.These data suggest that there has been sprouting of axons from descending nerve tracts rostral to the thoracic lesion in both the neonatal and weanling experimental groups. The question remains whether the sprouting of descending nerve tracts is from collaterals of axons which normally project rostral to the thoracic hemisection and are not cut by the thoracic lesion (collateral sprouting) or from collaterals of lesioned axons (regenerative sprouting). Present evidence favors collateral sprouting, especially in the neonatal operate where much retrograde cell death appears to have taken place.
Postnatal maturation of rat Purkinje cells cultivated in the absence of two afferent systems: An ultrastructural study
Authors: Privat A. , Drian M. J. 
Published: January 2005

AbstractOrganized cultures of newborn rat cerebellum were established in Maximow chambers in order to study the maturation of Purkinje cells in absence of afferent systems. In the first model, standard cultures were devoid of extracerebellar afferents mossy and climbing fibers. Despite this absence, somatic spines appeared upon Purkinje cells during the first week in vitro and maturation proceeded normally except for the almost absence of spiny branchlets. Large dendritic trunks were studded with numerous spines, some of which were naked, a few bearing isolated post‐synaptic densities and others occupied by boutons of parallel fibers. Stellate and basket axons made synapses upon the smooth portions of dendrites and soma.In a second model, the cultures were fed the antimitotic drug methylazoxymethanol (MAM) to prevent multiplication of granule cell precursors. Despite the absence of climbing and parallel fibers, the elongation of Purkinje dendrites was not prevented, but again the dendritic arbor consisted of large trunks studded with spines; somatic as well as dendritic spines were contacted by large boutons identified as Purkinje recurrent collaterals (PRC). It is concluded that the Purkinje cell possesses a large autonomy from afferent systems as to the growth of soma and dendrites.Conversely, the geometry of the dendrite and especially the spiny branchlets depend on the presence of both climbing and parallel fibers. One may conclude from the above experiments that specificity of synaptic contacts is maintained as long as postsynaptic sites are not devoid of their normal afferents. Heterologous synapses are formed when postsynaptic sites are present, their normal afferents absent and aberrant ones increasing by collateral sprouting. Such is probably the case in the second model of this study.
Glial changes in the progress of a chemical lesion. An electron microscopic study
Authors: Lemkey‐Johnston N. , Butler V. , Reynolds W. A. 
Published: January 2005

AbstractThe response of non‐neuronal cells in the brain to monosodium glutamate (MSG) was studied in the neonatal mouse brain. Neurons rapidly degenerate in this chemically‐induced lesion, and the glia reflect and respond to their early pyknosis and death. Astrocytic glia exhibit the most profound responses in the form of degenerative nuclear and cytoplasmic changes within 15 to 20 minutes after ingestion of MSG. After 6 to 12 hours, a large glial cell population, containing neuronal and synaptic debris, can be seen. Recovery of severely damaged astrocytes is unlikely. Further, evidence of multiplication of uninjured cells to supply this observed repopulation was found.Microglia start to engulf debris at 6 to 12 hours and continue this process through at least 48 hours. From 3 to 48 hours, a third cell type, tentatively identified as a Gitter cell, is prominently involved in phagocytosis of neuronal elements. Nuclei of these cells enlarge and their perikarya become vastly expanded in a fashion typical of Gitter cells. These cells appear to represent the transformed microglia.Phagocytosis following a chemical lesion induced by glutamic acid, a neurotransmitter substance, is exceedingly rapid in comparison to that elicited by other types of lesions. Further, endogenous glial cells cope with the cellular debris; no participation in this process by hematogenous cells was observed.
The basilar pontine gray in the adult monkey (Macaca mulatta): A Golgi Study
Authors: Cooper Margaret H. , Fox Clement A. 
Published: January 2005

AbstractIn Golgi preparations of the adult monkey(Macaca mulatta) two types of neurons are distinguished in the pontine gray: (1) larger neurons which impregnate most frequently and(2) smaller neurons which impregnate rarely. The former are judged to be projection neurons with myelinated axons because only the initial segments of their axons impregnate, while the latter are judged to be intrinsic neurons since they appear to participate only in the local circuitry of the pontine gray.The projection neurons show a variety of sizes and shapes and are the equivalent of the large, medium and small neurons that Ramón y Cajal ('09) illustrated in the pons of the 5‐day‐old infant. Their cell bodies are rounded, polygonal, triangular, egg‐, pear‐, and spindle‐shaped. Some have somatic spines. Usually four to seven dendrites issue from the cell body and as they branch they attenuate. The dendrites have knobby, nodular protuberances which give them a gnarled appearance. Also the dendrites have a few scattered spines. In most instances the dendrites have a wavy recurring pattern. Neurons pressed against the corticospinal, corticopontine fiber bundles frequently have elongated cell bodies and the dendrites sprouting from them form tight, brush‐like arrays.The intrinsic neurons have small ellipsoid or pear‐shaped cell bodies and two to three long dendrites, which do not taper. In some impregnations short axons issuing from the cell body were found and in other impregnations several widely separated, short axon‐like processes were found on dendrites. A striking feature of the intrinsic neurons is the presence of stalked dendritic appendages bearing one or more bulbous bodies, 1 to 3 microns in diameter. The intrinsic neurons in no way resemble the hairy or mossy cells with short axis cylinders that Ramón y Cajal ('09) described in the pons of the 5‐day‐old infant. The latter were not found in the present material.