bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gracilo‐diencephalic relay cells: A quantitative study in the cat using retrograde transport of horseradish peroxidase
Authors: Blomqvist Anders 
Published: January 2005

AbstractIn a quantitative study in the cat, gracilo‐diencephalic relay cells were labeled by the use of retrograde axonal transport of horseradish peroxidase injected into the ventroposterolateral nucleus of the thalamus. An initial series comprising 22 animals with survival periods varying between 2 h and 4 days showed maximal labeling in the gracile nucleus after 24–48 h. The earliest appearing peroxidase‐positive neurons were found after only 6 h, implying a transport rate in the medial lemniscus of at least 100 mm/day. In a second series of five cats, which were killed 24 h after injection, serial sections from the gracile nucleus were embedded in Epon following peroxidase processing, and cut at 2 μm. By stratified random sampling, about 2,000 cells were selected for light microscopic examination.The total number of nerve cells in a single gracile nucleus was calculated to be about 50,000, out of which about 15,000 were retrogradely labeled. In agreement with previous reports, rostrocaudal differences were observed. Thus, less than a third of the neurons in the rostral part of the nucleus were peroxidase‐positive, whereas about half of those in the middle and caudal regions were retrogradely labeled. The total number of labeled neurons was, however, about the same in the rostral as in the middle‐caudal part of the nucleus. The size of the nerve cell bodies, measured as the cross‐sectional area in the nucleolar plane, differed significantly between labeled and unlabeled neurons. The estimated average diameter of the former was 22 μm and of the latter 17 μm. There was a considerable overlap between the two groups, however, and labeled cells as small as 12 μm in diameter were found. Mainly because of the uneven distribution of labeled neurons, cells in the rostral region were, on the average, significantly smaller than those in the middle and caudal regions; these mean diameters were calculated to be 18, 23, and 21 μm, respectively.The results of this study support the idea of a heterogeneous organization of the gracile nucleus. However, a much larger proportion of the gracilo‐diencephalic relay cells is situated in the rostral part of the gracile nucleus than has previously been thought. The concept that only medium‐sized neurons project to the diencephalon also seems to need revision. It is concluded that although gracilo‐diencephalic relay cells are, on the average, larger than the nonlabeled neurons, single nerve cells cannot be identified on the basis of size alone. The function of the unlabeled neurons is discussed. Although many of these might relay to various extra‐diencephalic sites, it is suggested that a large number are internuncial neurons.
Representation of the body surface in somatosensory area I of tree shrews, Tupaia glis
Authors: Sur Mriganka , Weller Rosalyn E. , Kaas Jon H. 
Published: January 2005

AbstractMicroelectrode mapping methods were used to determine the organization of the first somatosensory area, S‐I, of tree shrews. Tree shrews were chosen for study because of their generalized body form, phylogenetic relationship to primates, and smooth, easily mapped cortex. A systematic representation of the contralateral body surface was found in an architectonically distinct zone identified as somatic koniocortex. Overall features of somatotopic organization were similar to S‐I of other mammals, S‐I of prosimian primates, and the Area 3b “S‐I proper” representation of monkeys. Like Area 3b in monkeys and the somatic koniocortex in galagos, S‐I in tree shrews is bordered caudally by cortex also responsive to somatosensory stimuli. Several aspects of S‐I organization in tree shrews appear to be primitive and generalized. These include the representation of the trunk with the ventrum at the caudal margin of S‐I, the restriction of the glabrous digits of the hand and foot to the rostral half of the representation and pointed rostralward, the representation of an anterior strip of the forelimb lateral to the hand, and a posterior strip of hindlimb medial to the foot representation. As in a number of other mammals, a large portion of S‐I in tree shrews is devoted to the head. However, the proportion of S‐I activated from the glabrous nose is greater in tree shrews than in any previously studied mammal. We conclude that S‐I of tree shrews has both specialized and generalized features, and that the generalized features importantly relate to an understanding of the evolution of the primate somatosensory system.
Visuo‐oculomotor properties of cells in the superior colliculus of the alert cat
Authors: Peck Carol K. , Schlag‐Rey M. , Schlag J. 
Published: January 2005

AbstractVisual responses and eye movement (EM) ‐related activities were studied in single units of the superior colliculus (SC) of alert cats. Spontaneous EMs were encouraged by training. Throughout the SC (i.e., in intermediate and deep layers as well as in superficial layers), units were found to respond well to visual stimuli. Strong and consistent responses could be elicited by very dim, low‐contrast stationary stimuli. Visual responses varied from phasic to tonic; some units responded tonically to stationary stimuli in the center of the receptive field, and phasically to peripheral stimuli. Many cells responded more vigorously to moving than to stationary stimuli, but very few responded exclusively to stimulus movement. The vast majority of cells were directionally selective.A small number of units were sensitive to the absolute, as well as the retinal, position of visual stimuli. These cells were activated by visual stimuli which fell in the receptive field only if the cat's gaze was fixated on one half of the screen. It seems that these cells must receive information about both eye position and the retinal (receptive field) position of the stimulus. It is possible that they reflect coding of target location within a head (or body) frame of reference.EM‐related units were of two types: (1) about 20% of the sample responded prior to spontaneous or visually‐triggered EMs, and (2) another 10% (or more) responded with, but not before, EMs. Some cells in the second group discharge almost synchronously with EMs and, thus, cannot plausibly be said to respond to the movement of images across the retina. All cells in the first group were directionally selective. The percentage of EM‐related cells in the deep layers of SC is lower in cat than in monkey. Possible reasons for such differences are discussed.
Temporal and spatial patterns of Purkinje cell formation in the mouse cerebellum
Authors: Inouye Minoru , Murakami Ujihiro 
Published: January 2005

AbstractIn an attempt to determine the time of origin and the final localization of Purkinje cells in the cerebellum, pregnant mice were injected with tritiated thymidine successively, four to six times daily, beginning on either day 10, 11, 12, 12.5, 13, or 14 of gestation, considering 6 a. m. on the day when vaginal plugs were found as day 0. Offspring were killed at 30 days of age, and serial sagittal sections of the cerebellum were prepared for autoradiography. Labeled and unlabeled Purkinje cells in the various regions of the cerebellum were counted, and unlabeled ones were considered to be formed earlier than the initiation of the injections. In the medial level of the vermis, the majority of the Purkinje cell population was formed on day 12 of gestation and a few on day 13, whereas the cells in the paravermian and hemispheric portions were formed on days 11 and 12. Thus, a slight lateromedial gradient of the time of Purkinje cell origin was demonstrated. Purkinje cells that were formed after day 12.5 were distributed more in the vermis than in the hemisphere, more in the ventral region of the vermis (lingula, ventral lobule of lobulus centralis, and nodulus) than in the dorsal region (culmen, declive, tuber, pyramis, and uvula), and deep in the vermian fissures, rather than on the surface of the lobules. These findings suggest that postnatally, early maturing regions of the cerebellum may have received many of the later formed Purkinje cells.
Distribution of acetylcholinesterase in the geniculo striate system of Galago senegalensis and Aotus trivirgatus: Evidence for the origin of the reaction product in the lateral geniculate body
Authors: Fitzpatrick David , Diamond Irving T. 
Published: January 2005

AbstractThis inquiry began with the discovery that just tow layers of the lateral geniculate nucleus (GL) of Galago contain large amounts of acetyl‐cholinesterase (AChE). These two layers (layers 3 and 6) are similar in cell size and Nissl‐staining characteristics and project to the same layer in the striate cortex.To find out whether the pattern of staining is unique in the Galago, We examined the distribution in AChE in the lateral geniculate nucleus of the owl monkey, Aotus trivirgatus. In this species we found that the parvocellular layers (3 and 4) stained darkly for AChE while the magnocellular layers (1 and 2) were only slightly stained. The interlaminar zones as well as the “S” layers were also distinguished by a high level of AChE staining.In order to determine the source of the cholinesterase staining in layers 3 and 6 of Galago, we studies, in separate experiments, the effects of kainic acid injections into GL, of eye enucleations, and of lesions of the striate cortex. Injections of kainic acid, followed by survival time of 2 and 11 days, produced severe cellular destruction in GL, yet the AChE staining of layers 3 and 6 was undiminished. Eye enucleations had no effect upon the AChE staining of GL even after a survival period of 3 years. In contrast, a small lesion of the striate cortex, followed by a 9‐day survival period, produced conspicuous gaps in the AChE staining of layers 3 and 6. These results indicate that the AChE in layers 3 and 6 is not attributable to the cells within the layers, or to retinal fibers, but is dependent upon descending projections form the striate cortex.Because of the dependence of AChE reaction product in layers 3 and 6 of GL upon and intact striate cortex, we turned our attention to the distribution of AChE in the striate cortex. In Galago, cholinesterase‐positive cells were found in layer VI of the striate cortex; and in both Galago and Aotus, the striate cortex was distinguished from other cortical areas by a prominent band of cholinesterase activity within layer IV. This band ended abruptly at the 17‐‐18 border. The precise origin of this cholinesterase staining within layer IV of the striate cortex remains to be determined.
Retinofugal pathways in two chondrichthyans, the shark scyliorhinus canicula and the ray Raja clavata
Authors: Smeets Wilhelmus J. A. J. 
Published: January 2005

AbstractRetinofugal pathways in the spotted dogfish Scyliorhinus canicula and the thornback ray Raja clavata were studied with reduced silver techniques following unilateral eye enucleations. Optic nerve axons decussate in the chiasma opticum, except for a small ipsilateral projection to the area preoptica. After crossing, retinal projections distribute to the area preoptica, the thalamus dorsalis pars lateralis, the thalamus ventralis pars lateralis, the corpus geniculatum laterale, the nucleus pretectalis, and the superficial layers of the tectum mesencephali. In Scyliorhinus most primary optic fibers terminate in the stratum medullare externum of the mesencephalic tectum, while in Raja the zona externa of the stratum cellulare externum receives the bulk of the retinal input. A basal optic tract could be identified in Raja, but not in Scyliorhinus.The retinofugal pathways of the two species studied are compared with those of other cartilaginous fishes and other anamniotes. It is concluded that the primary visual system in chondrichthyans resembles that of actinopterygians and amphibians. However, there is a striking difference in the way in which the primary optic fibers reach the tectal target areas. In elasmobranch fish the optic nerve fibers enter the tectum through the zona interna of the stratum cellulare externum and send their axons into the more superficial tectal layers, while in actinopterygians and amphibians the majority of the optic fibers enter the tectum through the superficial layer and distribute their axons to deeper tectal layers.
Efferent tectal pathways in two chondrichthyans, the shark Scyliorhinus canicula and the ray Raja clavata
Authors: Smeets Wilhelmus J. A. J. 
Published: January 2005

AbstractThe efferent connections of the tectum mesencephali in the shark Scyliorhinus canicula and the ray Raja clavata have been studied by using the silver impregnation methods of Nauta‐Gygax ('54) and Fink‐Heimer ('67). After a unilateral lesion made through all six tectal layers, three distinct pathways could be observed: (1) an ascending projection both ipsi‐ and contralateral to the pretectal area, the dorsomedial region of the thalamus, and the lateral geniculate body, (2) a commissural projection to the contralateral tectum and intercollicular nucleus, and (3) a descending projection to the rhombencephalic reticular formation. The last mentioned tract can be subdivided into (a) the ipsilateral tractus tectobulbaris ventralis and intermedius, giving off fibers to the intercollicular nucleus, the nucleus reticularis isthmi, and the medial and median reticular formation of the rhombencephalon and (b) the contralateral tractus tectobulbaris dorsalis, which connects the tectum with the contralateral medial reticular formation. Contrary to what has been found in other vertebrates there is no distinct segregation with respect to laterality of tectoreticular connections. Neither an ipsilateral projection to the nucleus isthmi nor a direct tectospinal pathway could be demonstrated with the techniques used.
Polysaccharide and cytoplasmic changes in motoneurons during “chromatolysis” in the opossum spinal cord
Authors: Magalhaẽs‐Castro Heloisa H. , Kruger Lawrence 
Published: January 2005

AbstractFollowing axotomy, motoneurons of the opossum spinal cord display an early “axon reaction” or “chromatolysis” characterized by a redistribution of ribosomes accounting for a widespread basophilia and an apparent reduction in the size of two distinct varieties of Nissl bodies. This alteration is accompanied by zones of increased extracellular glycocalyx demonstrable in light and electron microscopy. In addition, large intracellular periodic acid‐Schiff‐positive vacuolated zones in the neuron periphery possess numerous free ribosomes, glycogen, lipids, and huge vacuolated sacs containing a flocculent matrix material similar to that found within the sacs of granular endoplasmic reticulum. “Artifacts” in the neuronal periphery associated with chromatolysis seen in light microscopy are probably related to polysaccharide alterations and redistribution of granular endoplasmic reticulum.
Immunohistochemical localization of leucine‐enkephalin in the spinal cord of the cat: Enkephalin‐containing marginal neurons and pain modulation
Authors: Glazer E. J. , Basbaum A. I. 
Published: January 2005

AbstractThis study examined the spinal cord distribution of the endogenous opioid peptide leucine‐enkephalin in the cat using immunohistochemical techniques. The distribution of nerve processes was studied in untreated cats; colchicine was administered to study the distribution and morphology of spinal enkephalin‐containing perikarya.Enkephalin immunoreactive processes were greatest in laminae I and II (marginal layer and substantia gelatinosa) of the superficial dorsal horn. In many sections, the outer substantia gelatinosa (SG), lamina IIa, was discernibly less immunoreactive than I or IIb. Laminae III and IV were relatively devoid of staining. Laminae V and VII had moderate enkephalin‐immunoreactivity, lamina VI somewhat less. Enkephalin immunoreactivity in lamina X, around the central canal, was very dense. Enkephalin‐containing beaded varicosities coursed throughout the ventral horn.Although previous studies in the rat emphasized the enkephalin‐somata of the SG, we found that in the cat the majority of superficial dorsal horn enkephalinsomata are in the marginal layer. These enkephalin‐containing marginal cells were morphologically similar to a population of marginal neurons which project to the brainstem and/or the thalamus. Some light staining small SG neurons were also identified; many were located at the lamina I‐II border. Considerably more cells were found ventral to the SG, in lamina III, and at the IV‐V border. These latter cells had dendrites coursing dorsally, toward the SG. Numerous immunoreactive cells were found in lamina VII, in a band across the intermediate gray. These cells fused medially with cells of lamina X. Enkephalin cells were also found in the sacral autonomic nucleus and encircling the central cervical nucleus, Clarke's column, and Stilling's nucleus. Although surrounded by labeled cells, the latter regions were devoid of enkephalin‐immunoreactive processes.Many of these spinal enkephalin neurons are morphologically similar to and distributed in regions known to contain projection neurons. Thus it is suggested that many spinal enkephalin neurons, generally thought to be local circuit neurons, project rostrally, to other spinal levels and perhaps to brainstem and/or thalamus.
Further evidence for an early critical period in the development of the cat's dorsal lateral geniculate nucleus
Authors: Sherman S. Murray , Wilson James R. 
Published: January 2005

AbstractThe concept of an early postnatal critical period of development for the lateral geniculate nucleus was assessed by determining in adult cats whether previously established properties of geniculate neurons could be altered by varying the cats' visual experience. The analysis was limited to lamina A1 and the binocular segment of lamina A, and the properties studied were the percentage of physiologically recorded Y‐cells and cell soma size. Eleven experimental cats in four groups were studied, and three cats reared normally plus three cats reared with continuous monocular lid suture served as controls. Two cats raised first with monocular suture followed by a prolonged period in adulthood with both eyes open had cell size distributions and Y‐cell proportions that were indistinguishable from cats raised with continuous monocular suture. Four cats raised first with one eye sutured underwent a reverse suture procedure in adulthood (i.e., the originally sutured eye opened and the other closed) and were maintained in this fashion for a prolonged period. These cats also had geniculate cell size distributions and Y‐cell proportions that were indistinguishable from cats raised with continuous monocular suture. Two cats were raised first with binocular suture followed by a prolonged period in adulthood with one eye opened. Their geniculate cell size distributions and Y‐cell proportions showed no effect of the adult monocular deprivation and were indistinguishable from previously published data concerning cats raised with continuous binocular suture. Finally, three normally raised cats underwent a prolonged period of monocular suture in adulthood. Their geniculate cell size distributions and Y‐cell proportions showed no effects of the adult monocular deprivation. From these data, we conclude that an early critical period of development occurs for geniculate cell sizes and Y‐cell proportions. Adult visual environments, whether normal or abnormal, had no detectable effect on geniculate neurons for these previously developed properties, whether normal or abnormal.
Medial rectus subgroups of the oculomotor nucleus and their abducens internuclear input in the monkey
Authors: Büttner‐Ennever J. A. , Akert K. 
Published: January 2005

AbstractPhysiological experiments show that the abducens internuclear pathway is involved in the activation of only the medial rectus (MR) eye muscle. Previous anatomical experiments have shown that this pathway terminates in multiple foci within the oculomotor nucleus (OMN) of the monkey, and not only over the classical motoneuron subgroup. In this study the location of MR motoneurons in the monkey OMN is reinvestigated, and compared with the detailed pattern of terminations of the abducens internuclear pathway. The motoneurons were labelled by injections of retrograde tracer substances, HRP and [125I] wheat germ agglutinin (WGA), into extraocular muscles. Labelled MR motoneurons were found in three main divisions, called subgroup A, B, and C. Subgroup A corresponds mainly to the classical ventral MR subgroup. Subgroup B lies dorsal and caudal in OMN, occupying an area classically reserved for inferior rectus (IR). However, the representation of IR is shown to be further rostral in the dorsal OMN. Subgroup C is on the dorsomedial border of OMN. Its cells are significantly smaller than those of group A and B. In addition C could be labelled independently of the other subgroups by small injections into the outer (orbital) layer of MR muscle. This indicates a functional difference between the subgroups. It is suggested that subgroup C may be important for the tonic component of MR activity, possibly convergence. The location of abducens internuclear terminals, labelled by the injection of tritiated amino acids into the abudens nucleus, corresponds exactly to the position of MR motoneurons. These experiments provide a new picture of the internal OMN organization, and support the physiological findings that the abducens internuclear pathway activates only MR motoneurons.
Golgi‐impregnated amacrine cells and GABAergic retinal neurons: A comparison of dendritic, immunocytochemical, and histochemical stratification in the inner plexiform layer of rat retina
Authors: Famiglietti Edward V. , Vaughn James E. 
Published: January 2005

AbstractThis paper concerns the banding pattern produced in the inner plexiform layer of rat retina by glutamic acid decarboxylase (GAD) immunocytochemistry. It presents a comparison of this pattern with the dendritic stratification of neurons that are reasonable candidates for GABAergic amacrine cells in Golgi preparations, and also with the banding patterns produced by other histochemical techniques. First, the spacing of five dense GAD‐positive bands and four intervening less dense bands in central retina is quantitatively described. Second, examples of a particular, morphologically homogenous group of Golgi‐impregnated amacrine cells are examined in the details of their structure, espeically with regard to their dendritic stratification. Computer reconstructions of the dendritic trees of some of these narrow‐field, multistratified amacrines are compared with the GAD‐positive banding pattern. This group of amacrines is judged to represent many of the GABAergic neurons in rat retina, accounting for the form and distribution of GAD‐positive synaptic terminals by their dendritic morphology and stratification. Third, a general schema for the laminar subdivision (stratification) of the inner plexiform layer in rat retina is derived from a comparison of the results of several histochemical procedures. Finally, similarities and differences in the distribution of GAD‐positive amacrine cell dendrites are noted among mammals and the functional implications of their broad distribution are discussed. A conspicuous difference is cited between mammals and certain nonmammalian vertebrates in which GAD‐positive dendrites are restricted to sublamina b (ON‐center cells) of the inner plexiform layer.