bluuebunny/crossref_metadata_2025_split huggingface dataset:
An intracellular electrophysiological study of the ontogeny of functional synapses in the rabbit retina. II. Amacrine cells
Authors: Dacheux Ramon F. , Miller Robert F. 
Published: May 2005

AbstractIntracellular recordings in an isolated perfused retina‐eyecup preparation of the neonate rabbit were used to study the physiological development of amacrine cells. By responding with transient depolarizations at the onset and termination of illumination, mature mammalian on‐off amacrine cell recordings appeared similar to those described in lower vertebrates. However, immature amacrine cell recordings showed a predominantly on response, with off responses small and easily fatigued during repetitive stimulation. This underdeveloped off component of the amacrine cell response could also be abolished by decreasing the area of receptive field that was stimulated. The more slowly developing off component may reflect a different maturation rate of depolarizing (on) and hyperpolarizing (off) bipolar cells. In addition, properties of the maturing inner plexiform layer were examined with extracellular recordings of the proximal negative response (PNR). The PNR showed evidence of evidence of easy fatigability more evident in the off response. These observations are consistent with the idea that the initial phase of light sensitivity is associated with labile synaptic input from bipolar cells.
Immunohistochemical localization of substance‐P, somatostatin, and methionine‐enkephalin in the spinal cord and dorsal root ganglia of the north american opossum, Didelphis virginiana
Authors: Ditirro Frank J. , Ho Raymond H. , Martin George F. 
Published: May 2005

AbstractThe occurrence and distribution of substance‐P (SP), somatostatin (SOM), and enkephalin (ENK) were studied in the North American opossum, a generalized marsupial. Substance‐P immunoreactivity was present in the tract of Lissauer as well as within lamina I, the outer part of lamina II, the lateral portion of laminae III through VII, and lamina X at all spinal levels. Although present, it was very sparse in the ventral horn. Substance‐P was also localized within autonomic areas of the thoracolumbar cord. ENK immunoreactivity was present in laminae I‐III and laminae VII‐X, as well as within autonomic areas. There was more ENK immunoreactivity in the ventral horn than SP. The densest aggregates of ENK, however, were found within the outer part of lamina II. In contrast, SOM could not be localized within the spinal cord of the opossum. (See NOTE ADDEDIN PROOF).
Development of the brain stem in the rat. V. Thymidine‐radiographic study of the time of origin of neurons in the midbrain tegmentum
Authors: Altman Joseph , Bayer Shirley A. 
Published: May 2005

AbstractGroups of pregnant rats were injected with two successive daily doses of 3H‐thymidine from gestational day E12 and 13 (E12 + 13) until the day before parturition (E21 + 22) in order to label in their embryos the proliferating precursors of neurons. At 60 days of age the proportion of neurons generated (no longer labeled) on specific embryonic days was determined quantitatively in 18 regions of the midbrain tegmentum. The neurons of the oculomotor and trochlear nuclei are generated concurrently on days E12 and E13. There was a mirror image cytogenetic gradient in these nuclei and this was interpreted as the dispersal of neurons derived from a common neuroepithelial source to the medial longitudinal fasciculus. Neurons in three other components of the tegmental visual system are produced in rapid succession after the motor nuclei. In the nucleus of Darkschewitsch peak production time was on days E12 and E13, extending to day E15; in the Edinger‐Westphal nucleus the time span was the same but with a pronounced peak on day E13; finally, the neurons of the parabigeminal nucleus were produced between days E13 and E15 with a peak on day E14. The neurons of the periaqueductal gray were generated between days E13 and 17 with a pronounced ventral‐to‐lateral and lateral‐to‐dorsal gradient.In the red nucleus the neurons were produced on days E13 and E14 with a caudal‐to‐rostral gradient: the cells of the magnocellular division preceding slightly but significantly the cells of the parvocellular division. The neurons of the interpeduncular nucleus originated between days E13 and E15; the peak in its ventral portion was on day E13, in its dorsal portion on days E14 and E15. A ventral‐to‐dorsal gradient was seen also in both the dorsal and the median raphe nuclei in which neuron production occurred between days E13 and E15. The neurons of the pars compacta and pars reticulata of the substantia nigra were both produced between days E13 and E15 with a modified lateral‐to‐medial gradient. This gradient extended to the ventral tegmental area where neurons of the pars medialis were produced between days E14 and E16. With the exception of the central gray, neuron production was rapid and relatively early in the structures situated ventral to the midbrain tectum. A comparison of the cytogenetic gradients in the raphe nuclei of the lower and upper medulla, the pontine region, and the midbrain suggests that they originate from at least three separate neuroepithelial sources.
Transplantation of tectal tissue in rats. I. Organization of transplants and pattern of distribution of host afferents within them
Authors: Lund Raymond D. , Harvey Alan R. 
Published: May 2005

AbstractWe have examined the maturation of tectal tissue transplanted from fetal rats to the midbrain of newborns and have characterized the distribution of host retinal and cortical afferents within the transplants.The transplants develop characteristic internal order and connections which distinguish them from either embryonic cortex or retina placed in the same region. Host retinal afferents project to clearly circumscribed regions, where they synapase mainly on small dendrites or dendritic spines, and only rarely on vesicle‐containing profiles. The retinorecipient areas contain few stained axons in neurofibrillar preparations and are almost always located at the surface of the transplant. There is very little overlap in the input from the two eyes into a single transplant even though the projections from each eye may lie adjacent to one another. Cortical afferents spread more broadly in the transplants, but are largely absent from areas of optic termination and from other more deeply located regions with sparse fiber staining properties.The observations suggest that when placed close to its normal location, tectal tissue can develop a number of features characteristic of normal superior colliculus. Appreciation of the internal order of the transplants makes it possible to investigate the cortical and retinal afferent pathways using physiological techniques.
Trigeminal projections to the superior colliculus of the rat
Authors: Killackey Herbert P. , Erzurumlu Reha S. 
Published: May 2005

AbstractThe deep layers of the rodent superior colliculus contain a vibrissae‐related organization that is in “spatial register” with the overlying visuotopic organization (Dräger and Hubel, '76). The distribution of vibrissae‐related afferents and their cells of origin were determined with a number of anatomical techniques. The brainstem trigeminal complex afferents to the superior colliculus terminate in the lateral portions of the strata album intermediale and griseum profundum and, to a lesser degree, in deep portions of the stratum griseum intermediale. The cells giving rise to these afferents are located mainly in the ventral portions of the contralateral principal sensory nucleus, subnucleus oralis, and subnucleus interpolaris. The majority of tectal projection cells are found in subnucleus interpolaris, and the fewest in the principal sensory nucleus. Further, the density of projection cells in the three components of the brainstem trigeminal complex can be correlated with the density of their projections to the superior colliculus.The afferents from the somatosensory cortex terminate in a continuous band in the strata album intermediale and griseum intermediale. The cells of origin of this projection are located in layer Vb of the agranular zones of the ipsilateral somatosensory cortex.The present results suggest that the organization of trigeminal afferents to the deep portion of the superior colliculus is similar to that of the visual afferents to the superficial laminae. Further, the results suggest that observations on the nature of afferent termination patterns should be made with care, considering both the techniques employed and the idiosyncrasies of the local neuropil.
Evidence for a lack of distinct rubrospinal somatotopy in the North American opossum and for collateral innervation of the cervical and lumbar enlargements by single rubral neurons
Authors: Martin G. F. , Cabana T. , Humbertson A. O. 
Published: May 2005

AbstractStudies using axonal transport techniques on the North American opossum show that rubral neurons innervating the cervical cord are not distinctly separated from those which project to lumbar levels. This absence of clear rubrospinal somatotopy contrasts with that described for the placental mammals studied to date. Use of fluorescent markers in double‐labelling experiments shows that most rubral neurons in the opossum still innervate either the cervical or lumbar enlargement alone, but that some supply collaterals to both levels.
Postnatal increase of unmyelinated axon profiles in the feline ventral root L7
Authors: Risling Mårten , Hildebrand Claes , Aldskogius Håkan 
Published: May 2005

AbstractThe proportion of unmyelinated axon profiles and possible agerelated, degenerative and regenerative alterations were studied ultrastructurally in the L7 ventral root of 25 cats ranging from 3 weeks to 11 years of age. For comparison, the ventral root C6 was examined in 5 of these animals. The sections were taken from a level midway between the proximal and distal ends of the roots. The proportion of unmyelinated axon profiles in the L7 ventral root increased from about 14% to around 31% between 4 and 7 months after birth. Simultaneously, the average number of unmyelinated axon profiles per Schwann cell was doubled from 2–3 to 4–5. Thereafter, these figures remained largely unchanged for at least a decade. The total number of myelinated axons was similar in kittens and in cats. In the C6 root the proportion of unmyelinated axon profiles was about 20%, both in kittens and in young or old adult cats. At both segmental levels in the oldest cats, some unmyelinated axons showed degenerative changes and medium‐sized and large axons had features characteristic of demyelination and remyelination.
Projections from visual areas of the middle suprasylvian sulcus onto the lateral posterior complex and adjacent thalamic nuclei in cat
Authors: Updyke B. V. 
Published: May 2005

AbstractThe distribution of corticothalamic projections from lateral suprasylvian areas AMLS, PMLS, ALLS, and PLLS was investigated with the autoradiographic method. Areas AMLS and PMLS were both found to project retinotopically upon the medial interlaminar nucleus and the lateral and pulvinar zones of the lateral posterior complex, as well as to the ventral lateral geniculate nucleus, intralaminar nuclei, and thalamic reticular complex. Retinotopic projections to the dorsal lateral geniculate nucleus were demonstrated from PMLS but not AMLS, and projections to zona incerta were demonstrated from AMLS but not PMLS. Areas PLLS and ALLS were both found to project retinotopically upon the interjacent zone of the lateral posterior complex, as well as to the intermediate and suprageniculate divisions of the posterior nuclear group, the magnocellular division of the medial geniculate complex, the thalamic reticular complex, and central lateral nucleus. Area ALLS was also found to project onto the dorsal division of the medial geniculate complex and lateral division of the posterior nuclear group. Differences between the four cortical areas in the pattern and density of their thalamic projections supports the parcellation of these areas as proposed by Palmer et al. ('78).The projection patterns of areas PMLS, AMLS, PLLS, and ALLS were found to respect the boundaries of the zones of the lateral posterior complex, which had been identified and defined previously (Updyke, ′77), and the results thus support the hypothesis that these zones are the functional units of organization for visual traffic between the cat's extrastriate visual areas.
Observations on the organization of the visual cortex in the reeler mouse
Authors: Dräger Ursula C. 
Published: May 2005

AbstractThe developmental abnormality caused by the autosomal recessive mutation reeler leads to a systematic inversion in the depth distribution of morphologically defined cell classes in the cortex and to an abnormal course taken by thalamocortical projections (Caviness, '77). The course of the geniculocortical projections was visualized in reeler through transneuronal autoradiography. After traveling under the pial surface, the fibers terminate in a slightly patchy manner at intermediate levels of the primary visual cortex. As in the normal mouse, there is a weaker projection to the lateral part of area 17 ipsilateral to the injection. The retinal ganglion cells giving rise to the ipsilateral projection in reeler were labeled with horseradish peroxidase and were found to be located at normal positions in the retina.The functional competence of the primary visual cortex in reeler was studied by recording the response properties of single cells. In most respects the reeler cortex appeared remarkably normal: the cortical topography of the visual‐field representations was normal overall, all receptive field types seen in the normal mouse were present, and cells within the binocular region received normally convergent input from the two eyes. The reeler differed from normal in having a greater number of poorly responding cells and a lower fraction of cells with oriented receptive fields. The tendency for oriented cells to occur preferentially in upper cortical layers in the normal mouse was not present in reeler.These results imply that the cells in the reeler cortex are connected in a largely normal manner despite the gross malformation. Thus it appears that the specificity of intercellular connections, in reeler and in normal cortex, does not depend crucially upon the position of the cells in the cortex.
Evidence for cholinergic participation in the control of bird song: Acetylcholinesterase distribution and muscarinic receptor autoradiography in the zebra finch brain
Authors: Ryan Susan M. , Arnold Arthur P. 
Published: May 2005

AbstractBrain regions thought to be involved in the control of song in the zebra finch (Poephila guttata), were examined histochemically using the Karnovsky and Roots direct‐coloring method for the detection of acetylcholinesterase (AChE) and the autoradiographic method for the localization of muscarinic cholinergic receptors following injection of tritiated quinuclidinyl benzilate (3H QNB). All presently identified vocal control nuclei in both males and females contain AChE. These nuclei include Area X, magnocellular nucleus of the anterior neostriatum (MAN), nucleus interface (NIF), caudal nucleus of the hyperstriatum ventrale (HVc), intercollicular nucleus (ICo), nucleus uva, robust nucleus of the archistriatum (RA), and tracheosyringeal portion of the hypoglossal nerve nucleus (nXIIts). All nuclei except Area X contain mostly AChE‐synthesizing cell bodies. All of these nuclei contain some AChE in the neuropil, with particularly intense staining in Area X, the surrounding LPO, and the dorsomedial portion of ICo. In agreement with this description are very high concentrations of 3H QNB in both Area X and the dorsomedial ICo. HVc also appears specifically labeled. Evidence from these two histological techniques suggests that efferent projections of most vocal control areas may untilize acetylcholine, and that several of the vocal control nuclei may themselves receive muscarinic cholinergic projections. In Area X, there are sex differences in AChE neuropil staining. This evidence suggests that sexually dimorphic projections to or within Area X are cholinergic or cholinoceptive.
The retinal projection to the thalamus in the cat: A quantitative investigation and a comparison with the retinotectal pathway
Authors: Illing R.‐B. , Wässle H. 
Published: May 2005

AbstractThe projection of cat retinal ganglion cells to the thalamus was examined using the method of retrograde axonal transport of horseradish peroxidase (HRP). After the injection site was determined physiologically, HRP was applied by one of three methods: iontophoretic injection of minimal amounts, single pressure injections and multiple pressure injections.Iontophoretic injections into single laminae of the dorsal part of the lateral geniculate nucleus (LGNd) revealed that laminae A and A1 receive almost exclusively axon terminals from α and β cells. Single pressure injections elucidated the retinotopic organization of the LGNd. Multiple injections lead to HRP uptake in the whole LGNd including parts of adjacent thalamic nuclei and revealed that at least 77% of all retinal ganglion cells project to the thalamus. This pathway is made up of all α cells, all β cells and almost half of the γ cells. The thalamus receives its visual input predominantly from the ipsilateral temporal and the contralateral nasal retina; some α cells were also labeled in the contralateral temporal retina.The shape of the decussation line was analyzed and its width was found to be proportional to the average ganglion cell spacing along the dorsoventral axis of the retina. From a comparison of the retinothalamic and retinotectal pathways, an estimate of the number of cells with bifurcating axons could be given. The axons of all α cells, 10% of the β cells, and every second γ cell bifurcate; this amounts to 30% of the retinal ganglion cells.
Fibers in spinal nerves of tree frogs: Eleutherodactylus and Hyla
Authors: Sutherland Rodrique M. , Nunnemacher Rudolph F. 
Published: May 2005

AbstractThis is a study on numbers and sizes of nerve fibers as determined by electron microscope mapping of the spinal nerves of two species (in different families) of tree frogs. The study provides data for comparison of fiber populations in the grass frog, Rana pipiens. In both tree frogs the greatest number of fibers in the ten pairs of spinal nerves are in the second and ninth rami. The combined counts of myelinated and unmyelinated fibers in the rami on one side of the cord in Eleutherodactylus and Hyla are respectively: to the forelimb, 3,147 and 4,460 fibers; to the trunk, 334 and 1,234 fibers; and to the hindlimb, 4,335 and 6,213 fibers. With a few notable differences this distribution of fibers to regional body parts correlates closely with that found in Rana. The arboreal frogs have a relatively smaller number of medium and especially large size fibers in comparison with the aquatic‐terrestrial living grass frog. The importance is stressed of examining the spinal nerves of an entirely aquatic frog with different feeding habits, such as Xenopus, for further comparison.
Magnification functions and receptive field sequences for submodality‐specific bands in SI cortex of cats
Authors: Dykes Robert W. , Gabor Andrew 
Published: May 2005

AbstractElectrophysiological data were collected from the forelimb region of somatosensory cortex in barbiturate‐anesthetized cats using low‐impedance microelectrodes in long slanting trajectories. Subsequently, the brains were fixed and stained with thionin to locate the electrode trajectories and to correlate cytoarchitecture with neural activity. Confirming earlier experiments, regions of cortex, preferentially responsive to one submodality of afferent input, were observed to stretch in mediolateral bands across SI. Separate magnification functions were calculated for each band. In the forelimb region the magnification functions for the deep and cutaneous RA bands could be approximated by linear functions while the data for the cutaneous SA band was best described by a second‐order equation. At least in the forelimb region this magnification function applied only along the anteroposterior dimension of the band because the body representation is anisotropic; along the anteroposterior dimension of the band, receptive field loci may change only millimeters on the skin when the electrode moves through 1 mm of cortex, whereas when an electrode moves in a mediolateral direction they change centimeters on the forearm for an equivalent cortical distance.Each representation is separated from the others by a transition zone having a minimal width less than 200 m̈m. Within the transition zones, neurons often have receptive field loci which are a compromise between loci found in the adjacent representations. In these zones responses are often difficult to elicit. Electrode penetrations encountering these transition zones contain data which fulfill the receptive field and modality criteria for the boundary of a cortical column. However, within the mediolateral length of each submodality band we have found no unit with a dimension greater than 200 m̈m which has a boundary or transition zone. Evidence for units of smaller size cannot be obtained because of limitations in the data collection techniques. Thus, within each submodality‐specific band, large portions of the somatotopic map appear to be a mediolateral continuum while relatively abrupt changes occur in receptive field locus and in submodality when the electrode passes through a transition zone between adjacent bands.
Morphological study of noradrenaline innervation in the caudal raphe nuclei with special reference to fine structure
Authors: Takagi Hiroshi , Yamamoto Kazumi , Shiosaka Sadao , Senba Emiko , Takatsuki Kenichi , Inagaki Shinobu , Sakanaka Masahiro , Tohyama Masaya 
Published: May 2005

AbstractPrevious histofluorescence studies have demonstrated that the caudal raphe nuclei (CRa) of the rat, particularly the ventral portion (VCRa), contains a very high density of noradrenaline (NA) terminals and in the present study we attempted to elucidate the origins and free structure of the NA terminals in this region.The majority of NA terminals found in the VCRa originated from A1 and A3 NA neurons and disclosed that a small number of very strongly fluorescent fibers located along the blood vessels arise from the superior cervical ganglion (SGC). Electron microscopic analysis after potassium permanganate fixation demonstrated that the NA terminals originated from A1 and A3 NA neurons are connected with neuronal elements, while NA fibers from the SGC were identified among the vascular elements. Axodendritic contacts were found to be predominant among the synapselike contacts of NA terminals in this area.