bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural features of the terminal loop region of frog retinal rod outer segment disk membranes: III. Implications of the terminal loop complex for disk morphogenesis, membrane fusion, and cell surface interactions
Authors: Corless Joseph M. , Fetter Richard D. 
Published: January 2005

AbstractThe perimeter of rod outer segment (ROS) disks displays a two‐dimensional lattice of components referred to as the terminal loop complex (Corless, Fetter, Zampighi, Costello, and Wall‐Buford: J. Comp. Neurol 257: 9–23, '87b). We take the view that this pattern of structural organization reflects the mechanism(s) whereby the disk perimeter is defined and constructed. Herein we develop and partially evaluate a generalized template mechanism of disk perimeter development, to account for the structure and the axial alignment of both marginal and incisural domains. Components of the terminal loop complex are conceived as the morphogens that determine the location and guide the differentiation of the disk perimeter. Briefly, we postulate that transmembranous components of the terminal loop complex are present within the reflection of plasmalemma that forms the base of the rod outer segment. These components interact with the cytoplasmic template provided by the perimeter lattice present along the lower surface of the most basal disk, thereby propagating the lattice and creating an extracellular template. The latter is then available to interact with corresponding elements distributed, within the apical surface of the adjacent disk precursor evagination. The progressive interaction and alignment of these extracellular domains form the scaffolding that guides the restructuring of the plasmalemma, to form the mature disk margin topology. Successive repetitions of this process are seen to produce an axial stacking of disks whose perimeters are aligned and ensheathed by a two‐dimensional net.Several predictions of the model are developed and evaluated.
Distribution of neuropetide Y‐like immunoreactivity in the hypothalamus of the adult golden hamster
Authors: Sabatino Frank D. , Murnane Joan M. , Hoffman Roger A. , McDonald John K. 
Published: January 2005

AbstractThe distribution of neuropeptide Y (NPY)‐like immunoreactivity within the hypothalamus of the adult golden hamster was investigated with conventional immunohistochemical techniques. Neuropeptide Y immunoreactive cell bodies were found in greatest numbers in the arcuate nucleus while a few stained perikarya were seen in the internal and subependymal zones of the median eminence. Isolated perikarya were observed in the anterior commissure and supracommissural portion of the interstitial nucleus of the stria terminalis. Immunoreactive axons were located throughout the hypothalamus with the highest concentrations in the subependymal and internal zones of the median eminence, the interstitial nucleus of the stria terminalis, the medial preoptic area, and in the following nuclei: periventricular, suprachiasmatic, paraventricular, perifornical, median preoptic, and arcuate. Moderate to dense plexuses of immunoreactive fibers were observed in the anterior, lateral, and posterior hypothalamic areas and in the infundibular stalk. The supraoptic nucleus and lateral preoptic area displayed a small number of labeled axons whereas the ventromedial nucleus contained only a few fibers. NPY immunoreactive fibers were present in the optic tract and in the dorsomedial aspect of the optic chiasm. Labeled fibers penetrated the ependymal lining of the third ventricle throughout the ventral aspect of the periventricular zone. Additional fibers were observed in the pia lining the ventral aspect of the hypothalamus. This systematic analysis of hypothalamic NPY immunoreactivity in the adult golden hamster suggests that a portion of the labeled fibers display a distribution that is similar to previously described noradrenergic fibers in the hypothalamus.
Distrubution and size of thalamic neurons projecting to layer I of the auditory cortical fields of the cat compared to those projecting to layer IV
Authors: Mitani Akira , Itoh Kazuo , Mizuno Noboru 
Published: January 2005

AbstractThe distribution of thalamocortical neurons projecting to layer I of the cat auditory cortical fields was examined by the horseradish peroxidase (HRP) method. After HRP injection into layer I of the primary auditory cortex (AI), HRP‐labeled neuronal cell bodies were distributed mainly in the medial, dorsal, and ventrolateral divisions of the medial geniculate nucleus CMGN and suprageniculate nucleus (Sg), and additionally in the lateral and medial divisions of the posterior group of the thalamus (Pol and Pom), lateroposterior thalamic nucleus (Lp), and nucleus of the brachium of the inferior colliculus (BIN). After HRP injection into layer I of the second auditory cortex (AII), labeled neurons were seen mainly in the medial, dorsal, and ventrolateral divisions of the MGN and Sg and additionally in the Pom, Lp, and BIN. After HRP injection into layer I of the anterior auditory field (AAF), labeled neurons were located mainly in the medial and dorsal divisions of the MGN, Sg, Pol, and BIN, and additionally in the ventrolateral divisions of the MGN, Pom, and Lp. After HRP injection into layer I of the dorsal part of the posterior ectosylvian gyrus (Epv), labeled neurons were observed chiefly in the medial and dorsal divisions of the MGN, Sg, and Lp and additionally in the ventrolateral division of the MGN, Pom, and BIN. After HRP injection into layer I of the ventral part of the posterior ectosylvian gyrus (Epv), labeled neurons were distributed chiefly in the medial and dorsal divisions of the MGN and Pol and additionally in the ventrolateral division of the MGN, Sg, and BIN. Thus no labeled neurons were found in the ventral division of the MGN after HRP injection into layer I of all auditory cortical fields examined in the present study. The average soma diameters of neurons that were labeled after HRP injection into layer I were statistically smaller than those of neurons that were labeled after HRP injection into layer IV.
Visual system of the channel catfish (Ictalurus punctatus): II. The morphology associated with the multiple optic papillae and retinal ganglion cell distribution
Authors: Dunn‐meynell A. A. , Sharma S. C. 
Published: January 2005

AbstractThe retinal organization associated with the multiple optic papillae of the catfish Ictalurus punctatus was examined. In each retina from ten to 17 papillae form an oval ring (which is wider dorsoventrally than mediolaterally). The dorsalmost papilla in this ring lies at the center of the retina. In addition, up to seven small papillae lie within the ring. Bundles of fibers leave the neural retina via the papillae. These bundles remain separate as they pass through the distal portions of the neural retina and then merge before passing through the choroid. Bundles running through dorsal papillae receive fibers from a roughly wedge‐shaped retinal area; bundles running through ventral papillae receive fibers from a small area of central retina and a disproportionately large area of peripheral retina. A band of high ganglion cell density was observed extending between the nasal and temporal poles of the retina. No correlation was found between the retinal areas contributing fibers to the bundles of axons emerging from individual papillae and the areas of high cell density. Furthermore, no correlation was found between the average area of the retinal ganglion cells and the ganglion cell density. From HRP preparations and axon counts we estimate that each retina of 95‐mm catfish contains about 50,000 ganglion cells.
Choline acetyltransferase immunoreactivity in the rat thalamus
Authors: Levey Allan I. , Hallanger Ann E. , Wainer Bruce H. 
Published: January 2005

AbstractThe distribution of choline acetyltransferase immunoreactivity in the rat thalamus was investigated by using a specific monoclonal antibody and was compared with the pattern of acetylcholinesterase staining. The only choline acetyltransferase‐immunoreactive cell bodies in the thalamus were in the medial habenula. A wide range of densities of immunoreactive fibers and varicosities was found. The highest densities of stained varicosities were in the anteroventral, reticular, lateral mediodorsal, and intralaminar nuclei. At the other extreme, the anterodorsal, ventroposteromedial, and paraventricular nuclei were almost devoid of immunoreactive varicosities. A light density of fibers was observed in several medial nuclei, including parataenial, reuniens, and gelatinosus. Most other nuclei contained moderately dense regions of varicose fibers that were often heterogeneous or patchy. The pattern of choline acetyltransferase immunoreactivity in the thalamus was in general similar to that of acetylcholinesterase. A marked discrepancy, however, was found in the anterodorsal nucleus, which was intensely stained for acetylcholinesterase but contained no apparent choline acetyltransferase immunoreactivity. Numerous physiologic studies have demonstrated striking effects of acetylcholine on thalamic activity. The present study provides a description of choline acetyltransferase‐immunoreactive structures in the thalamic nuclei, providing a first step toward elucidating the anatomical basis for the physiologic and functional importance of cholinergic transmission in the thalamus.
Quantitative analysis of the choline acetyltransferase‐immunoreactive axonal network in the cat primary visual cortex: I. Adult cats
Authors: Stichel C. C. , Singer W. 
Published: January 2005

AbstractThe laminar distribution of cholinergic axons was analyzed quantitatively in the visual cortex of adult cats by using immunocytochemistry with a monoclonal antibody against choline acetyltransferase (ChAT). ChAT (+) fibers and varicosities were counted at different locations within area 17 and the distribution patterns in various animals were compared. Choline acetyl‐transferase‐immunoreactivity was localized in fine, varicose fibers, which were present in all layers of the visual cortex. The density of labeled fibers was highest in layer I, which contained 14% of all fibers and 19.5% of all varicosities, and decreased toward deeper layers. The number of varicosities decreased more markedly toward deeper layers than the frequency of fibers. These distribution patterns were very consistent, showing only slight intra‐ and interindividual variability.
Quantitative analysis of the choline acetyltransferase‐immunoreactive axonal network in the cat primary visual cortex: II. Pre‐ and postnatal development
Authors: Stichel C. C. , Singer W. 
Published: January 2005

AbstractThe pre‐ and postnatal development of cholinergic projections was investigated in the cat striate cortex by applying immunohistochemical methods based on a monoclonal antibody against choline acetyltransferase (ChAT).The earliest age investigated was gestational day 54. At this stage a sparse network of ChAT(+) fibers was distributed throughout the striate cortex. Subsequent postnatal maturation of ChAT(+) fibers was characterized by an increase in fiber density that started in layer VI and gradually progressed toward more superficial layers. By 4 weeks of age the density of ChAT(+) fibers and varicosities had reached adult levels in layers V and VI but was still subnormal in layers I–IV. The mature pattern of cholinergic innervation was established by 13 weeks of age. There was no evidence for developmental gradients in the anteroposterior and mediolateral directions within area 17. These results indicate that the cholinergic projection to striate cortex develops continuously in an inside‐out sequence as is characteristic for most cortical maturation processes. There was no indication that striate cortex receives an especially dense cholinergic input during the critical period.
Interhemispheric connections of the somatosensory cortex in the rabbit
Authors: Ledoux M. S. , Whitworth R. H. , Gould H. J. 
Published: January 2005

AbstractCorpus callosal connections of somatosensory cortex were studied in rabbits by combining anatomical tracing and electrophysiological mapping in the same animals. The results show that callosal connections are unevenly distributed in SI and SII. In SI, the representations of all body surfaces caudal to the neck and midline structures of the head have dense callosal connections. Conversely, connections are sparse to absent within representations of laterally positioned surfaces of the head, such as the sinus hairs, vibrissae, and nonmidline portions of the lips. Almost all of SII has dense callosal connections; only the representations of the vibrissae and sinus hairs have moderate callosal connections.The laminar distribution of callosal connections in rabbit SI and SII is similar to that observed in other mammals. Callosal terminations extend from the inner portion of layer I to the outer portion of layer VI, are moderately denser in the supragranular layers, and are sparse in layer IV. Callosally projecting cells are found predominantly in layers II, III, and V and are sparse in layers IV and VI.These data further emphasize the direct correspondence between the pattern of callosal connections in SI and the functional importance of particular body surfaces. Hence, representations of body surfaces important in the exploration of the environment are relatively free of callosal connections, whereas representations of midline and more lateral surfaces, less significant in tactile exploration, receive dense callosal connections.Callosal connections in rabbits are distributed extensively throughout responsive koniocortical regions rather than being relegated to distinct, specialized regions of “unresponsive” dysgranular cortex as in rodents.
Effect of tetraploidy on dendritic branching in neurons and glial cells of the frog, Xenopus laevis
Authors: Szaro Ben G. , Tompkins Robert , Szaro Ben G. 
Published: January 2005

AbstractMorphological aspects of four different groups of Golgi impregnated brain cells from a tetraploid strain of Xenopus laevis frogs were compared to analogous cells in comparably sized diploid frogs. The cells examined included neurons from the telencephalon, caudal hypothalamus, and optic tectum, and radial glial cells from the optic tectum. The brains of tetraploid frogs appeared grossly normal and were the same size and contained similar cell types as diploid brains. As observed in previous studies on polyploid amphibia, somal diameters increased significantly in tetraploid cells for each of the four groups of cells examined. Also, the total length of the dendritic arbors in tetraploid brain cells increased significantly by factors ranging from 1.4 to 2.4 times the total length of the analogous processes in diploid cells. Tetraploid neurons in the telencephalon and hypothalamus increased their arbor lengths predominantly by increasing the number of dendritic branches, while maintaining the average distance between branch points in the dendritic segments. In contrast, the tetraploid large pear‐shaped neurons in the optic tectum had significantly longer terminal dendritic segments than the analogous diploid neurons, although these tetraploid neurons maintained their average number of dendritic segments per cell. Tetraploid tectal radial glial cells appeared to increase both their number of branches and the lengths of their terminal segments. Thus, the mode by which tetraploid brain cells achieved longer dendritic arbors varied from cell type to cell type. These results suggest a hypothetical basis for possible effects of genomic size on vertebrate brain structure and evolution at the cellular level.
Patterns of angiogenesis in neural transplant models: I. Autonomic tissue transplants
Authors: Krum Janette M. , Rosenstein Jeffrey M. 
Published: January 2005

AbstractFunctional vascular connections must form rapidly to prevent ischemic damage to grafted neural tissues. The temporal sequence by which transplant circulation is re‐established provides information about the angiogenic capacity of either intact or damaged CNS blood vessels. This study compares the time course and mechanism of vascular reperfusion in allografts of superior cervical ganglia or adrenal medulla inserted either into the fourth ventricle or directly into the parietal cortex of perinatal rats. Tritiated thymidine was administered lo recipients to determine angiogenic patterns at various postoperative time periods. After processing for light microscopic autoradiography, host and graft endothelial labelling indices were determined in order to establish the temporal sequence and location of vascular proliferation, Correlative electron microscopy depicted the morphological changes in transplant vasculature. Some recipients were prelabelled with 3H thymidine prior to transplantation to determine if host vessels invaded the grafts.Intraventricular graft vessels initially collapsed but sustained minimal ischemic damage and were completely reperfused by 24 hours postoperative. Adjacent intact host vessels attained peak 3H thymidine incorporation at 20 hours. Intrinsic graft vessels were radioactively labelled only after 48 hours. Intraparenchymal transplants surrounded by minimal trauma exhibited a similar temporal sequence of reperfusion and host endothelial proliferation. Intrinsic graft vessels in intraparenchymal grafts sustained more severe damage. With increased trauma, a concomitant delay in graft reperfusion time was observed. Grafts within prelabelled hosts rarely contained any labelled endothelium, indicating that anastomotic connections were made between original, intrinsic graft vessels and nearby host vascular sprouts.This study demonstrates that mature autonomic tissue stimulates the growth of adjacent host vessels when transplanted to undamaged brain surfaces. The anastomosis of nascent host vessels with pre‐existing graft vessels is responsible for the rapid re‐establishment of circulation within the transplants. A similar mechanism occurs within intraparenchymal grafts, although the rapidity of reperfusion appears to be predicated on the amount of trauma present at the graft site.
Neuronal maturation in the normal and hypothyroid rat cerebellar cortex studied with monoclonal antibody MIT‐23
Authors: Gravel Claude , Hawkes Richard 
Published: January 2005

AbstractBy immunocytochemistry we have studied the expression of the mitochondria‐associated polypeptide MIT‐23 during the postnatal development of the normal and hypothyroid rat cerebellar cortex, in afferent fibers, and also in neurons of the cerebellar nuclei. The glial cells are never immunoreactive. In all neurons of the cerebellar cortex, MIT‐23 expression always occurs after the final mitosis and migration are complete, and persists throughout adult life. Almost all MIT‐23 expression begins postnatally. A few Purkinje cells are already immunoreactive at birth and the rest begin expression during the following two days. Immunoreactive Golgi and granule cells are found from postnatal day 4 (P4), basket cells from P10, and stellate cells from P16. Purkinje cells from different anteroposterior regions of the vermis express different levels of MIT‐23 with higher staining intensities in lobules I to IV. These differences appear early in development and are retained in the adult. MIT‐23 expression in the hypothyroid cerebellar cortex differs from that in control animals only in minor ways. However, sections immunoperoxidase‐stained with anti‐MIT‐23 antibody reveal that, in addition to previously reported alterations in cerebellar development due to a shortage of thyroid hormones, Purkinje cell axonal development is slowed down in the hypothyroid condition, and occasional Purkinje cells in normal and especially in hypothyroid animals have their somata and or dendrites in ectopic locations. Analysis of these cells reveals a preferential direction of dendritic trunk growth in the direction of the molecular layer. Furthermore, secondary branching of ectopic dendrites is confined exclusively to the developing molecular layer, as in normal Purkinje cells, thus suggesting that neither the mature nor immature granule cell environment is sufficient to sustain normal dendritic development.
Functional morphology of frog retinal ganglion cells and their central projections: The dimming detectors
Authors: Stirling R. V. , Merrill E. G. 
Published: January 2005

AbstractIntracellular recordings were made from frog retinal ganglion cell axons in the optic nerve. Following electrophysiological characterisation of receptive field properties, HRP was injected into the axon, and the brain and retina were subsequently stained. The morphologies of retinal ganglion cells, their dendritic domains, and their central projections were determined with light microscopy, and the optic nerve portion of the ganglion cell axon was examined with electron microscopy. This paper describes the structural and functional features of one ganglion cell class, the off units (class IV or dimming detectors) whose characteristic response is a preferential sensitivity to decreasing light intensity within the receptive field. Typical receptive field diameter of these units was about 16° with a range of 3° to more than 30°. Examination of the spatial characteristics of their receptive field centers and surrounds showed that the class IV cells could be divided into two broad categories. Linear class IV cells did not respond to phase‐reversal of a fine grating pattern. These linear cells also tended to have clear surround suppression: illumination of the surround diminished their response to light off at the center. The second group responded briskly to each reversal of the fine grating pattern, whatever its position within the receptor field center. These nonlinear class IV cells did not show surround suppression, but rather they had surround antagonism and they responded to light on in the surround. Nonlinear units were much more frequently recorded in frogs maintained in summer conditions (12‐hour days, constant 20°C temperature).In spite of this functional heterogeneity, all cells had similar morphology consisting of (1) a large ganglion cell with a large dendritic arbor (400–1,000 μm) confined to a single stratum in the outer third of the inner plexiform layer, (2) a medium‐sized axon (2.4‐μm diameter), (3) a smallish pretectal arbor, and (4) a large tectal arbor (300–700 μm) at layer 8.