bluuebunny/crossref_metadata_2025_split huggingface dataset:
A fine structural and E‐PTA study of photoreceptor synaptogenesis in the chick retina
Authors: McLaughlin Barbara J. 
Published: December 2004

AbstractPhotoreceptor synaptogenesis in the embryonic and hatchling chick retina was studied with conventional EM techniques and ethanolic phosphotungstic acid (E‐PTA). The photoreceptors line up between 11 and 13 embryonic days with their undifferentiated synaptic bases facing the outer plexiform layer (OPL). E‐PTA staining at 11 embryonic days does not reveal any paramembranous specializations of the receptors but numerous stained punctae adhaerentes are observed in the OPL. At 13 embryonic days neurites of presumed bipolar and horizontal neurons are aligned parallel to the bases of the receptors and cytoplasmic protrusions of the receptors project between some of these neurites to form dyad appositions. An osmiophilic undercoating, which is not E‐PTA positive at this time, is present on the cytoplasmic face of the receptor membrane in these apposition regions. Between 13 and 15 embryonic days the filopodial protrusions of the receptors continue to elongate further and become aligned with neurites in dyad and triad appositions. The osmiophilic undercoating now extends along the entire inner surface of the receptor pedicle protrusions and becomes E‐PTA positive. Between 15 and 17 embryonic days focal aggregations of osmiophilic and E‐PTA stained material appear along the membranes of the protrusions and there is some E‐PTA staining of the postsynaptic densities and intervening cleft material. Between 17 and 21 embryonic days mature ribbon synapses are observed on the surfaces of the conical‐shaped, receptor pedicles where the ribbons and their synaptic vesicles are associated with the dense aggregations (arciform densities), seen earlier as isolated focal aggregations, and the receptor undercoating is restricted to non‐synaptic regions. E‐PTA staining shows that ribbons are positively stained around their borders only and that they are contiguous with the intensely stained arciform densities. The cleft material and postsynaptic densities of some synapses first stain as V‐shaped junctions and later as Y‐shaped junctions. These observations suggest that ribbon synaptic junction formation begins with an alignment of pre‐ and postsynaptic membranes and the presence of the receptor presynaptic membrane undercoating, followed by the appearance of the presynaptic arciform densities and some staining of the cleft material and postsynaptic densities. These events are followed by the appearance of synaptic ribbons which are associated with the presynaptic arciform densities and by a further differentiation of the cleft material and postsynaptic densities.
Interhemispheric neocortical connections of the corpus callosum in the reeler mutant mouse: A study based on anterograde and retrograde methods
Authors: Caviness V. S. , Yorke C. H. 
Published: December 2004

AbstractThe tangential organization of the callosal system of interhemispheric connections, as judged by the distribution of axon terminals as well as by the distribution of cells of origin of callosal axons, is normal in the reeler mutant mouse. As in the normal animal connections between the two cerebral hemispheres are homotopic. In the reeler, as in the normal animal, medium‐sized pyramidal cells are, numerically speaking, the principal cells of origin of the callosal system. These lie superficially in the cortex of the normal animal but deep within the cortex of reeler. Callosal terminals are most densely concentrated at the cortical level of the small and medium‐sized pyramids in both reeler and normal animals. It is probable, therefore, that the same classes of neurons are interconnected by the callosal system in the normal and reeler mouse despite malposition of neurons in reeler. The pattern of intracortical distribution of terminals of callosal axons is evidently governed by the positions of their target cells.
Electron microscopic observations of nodes of ranvier in the external cuneate nucleus
Authors: Rosenstein Jeffrey M. , Leure‐duPree Alphonse E. 
Published: December 2004

AbstractDuring the course of an investigation of the synaptic organization of the external cuneate nucleus (ECN) in the Sprague‐Dawley albino rat, the ultrastructural morphology of nodes of Ranvier in the neuropil has been studied.The majority of nodes observed have the basic morphological features of conventional central nodes but there is individual variation with regard to length, surface area and cytoplasmic organelles. In addition, nodes with multiple myelinated branches are observed.Some nodes of Ranvier were observed to form specialized synaptic boutons. Two types of nodal synaptic boutons were present; a simple type and a complex type. Simple nodal boutons were observed more frequently. These nodes usually synapse upon a single dendritic element; the portion of the node opposite the presynaptic area has a morphology similar to conventional nodes. Complex nodal boutons are of greater dimension than simple nodal boutons and are usually in contact with several neuronal elements. They may be presynaptic to dendritic shafts or spines and are occasionally observed to be postsynaptic to small axonic profiles, a synaptic relationship which, until this report, has not been demonstrated in the central nervous system (CNS).The possible functional significance of these observations is discussed.
Effects of low‐level X‐irradiation on cat cerebella at different postnatal intervals. III. Changes in the morphology of interneurons in the molecular layer
Authors: Anderson William J. , Stromberg Melvin W. 
Published: December 2004

AbstractThe whole head of infant kittens was irradiated with fractionated doses of 150 R and 200 R at different postnatal intervals. Experimental age conditions consisted of a newborn, 1‐week, 2‐week, 3‐week, and a 4‐week age condition while the age of sacrifice remained constant at 70 days. Golgi analysis revealed that the interneurons found in the molecular layer of the newborn, 1‐week and 2‐week condition were basket cells. Stellate cells were found in increasing numbers in the 3‐week and 4‐week conditions. Basket cells were found to occupy the entire molecular layer in the newborn and 1‐week conditions resulting in an abnormal axonal plexus. The position of the basket cell soma was found to be in the same plane as its axonal projection. The branching point of the primary dendrite of Purkinje cells was found to correlate with the amount of molecular layer occupied by the abnormal basket cell plexus. Interneurons in the molecular layer were found to show different dendritic growth patterns dependent upon where their soma was located. Interneurons in the deep molecular layer showed only a decreased dendritic field, whereas interneurons in the middle and superficial molecular layer had an abnormal growth of dendrites into the deep molecular layer. A hypothesis is presented to account for the decreased dendritic arborization and the increased length of the primary dendrite before branching, the ectopic basket cell and their abnormally directed dendritic growth, and the difference in behavioral deficits between the newborn and the 1‐week conditions.
A quantitative study of retrograde neuronal changes in Clarke's column
Authors: Loewy Arthur D. , Schader Randolph E. 
Published: December 2004

AbstractA quantitative study has been made of the retrograde neuronal changes that occur in the large neurons of Clarke's column in the L3 spinal segment, 100 days after dorsolateral column lesions at the medullary, C5, T1, T8, and L1 levels in a series of 10‐week‐old kittens. Cell counts, and nuclear and perikaryal areal measurements, have been made in thionin stained material. The results indicate that following L1 level lesions, there is about a 30% loss of Clarke neurons and the remaining neurons are reduced in size to about 75% of their normal cross‐sectional perikaryal area (as judged from the cells on the opposite side) and about 65% of their normal nuclear area. Lesions at the T8 and T1 level both cause about a 20% Clarke cell loss; but after the T8 lesions, there is about a 65% decrease in perikaryal area and a 55% decrease in nuclear area while the T1 lesions cause about a 55% decrease in perikaryal area and a 45% reduction in nuclear area. Lesions at the C5 level result in about a 15% cell loss, a 50% decrease in perikaryal area, and a 40% decrease in nuclear area. Medullary lesions produce about a 5% cell loss, a 50% decrease in perikaryal area, and a 40% decrease in nuclear area. In unoperated control preparations, the left‐right differences in the number of cells are less than 2% and the areal measurements are within 5% of each other.The results of this study suggest that the severity of the retrograde neuronal reaction in Clarke's column is related to the proximity of the lesion to the cell body, but that this relationship is non‐linear. Several possible interpretations of these results are discussed.
Organization of auditory cortex in the owl monkey (Aotus trivirgatus)
Authors: Imig T. J. , Ruggero M. A. , Kitzes L. M. , Javel E. , Brugge J. F. 
Published: December 2004

AbstractThe region of cerebral cortex in the owl monkey that is responsive to acoustic stimulation is located on the dorsal and lateral surfaces of the rostral half of the superior temporal gyrus. Systematic microelectrode mapping of this area has revealed multiple frequency representations. The boundaries of these fields determined electrophysiologically correlate with the architectural bound aries apparent in Nissl stained material. On the basis of combined cytoarchitectonic and electrophysiological maps we have divided auditory cortex into five fields. Two of them, the primary field (AI) and the field rostral to it (R) are somewhat similar architectonically and constitute the central core of auditory cortex. Each of these two fields has a complete and orderly representation of the audible frequency spectrum within it. Surrounding these fields is a belt of cortex in which units are generally less responsive to acoustic stimulation and the frequency organization is more complex than in AI or R. Electrophysiological and cytoarchitectonic evidence suggest that this belt is composed of at least three and possibly four separate auditory fields.
Receptive field characteristics of neurons in a visual area of the rabbit temporal cortex
Authors: Chow Kao Liang , Douville Arthur , Mascetti Gian , Grobstein Paul 
Published: December 2004

AbstractIn a program of surveying the characteristics of visual receptive fields of neurons in rabbit brain, we have explored cortical sectors beyond the striate and occipital cortices and found cells in a part of the temporal lobe that were responsive to visual stimulation. Using evoked potential and unit‐cluster methods, this temporal visual areas was mapped to be roughly oval‐shaped, 3 mm × 2mm in size, and at about the level posterior to the apex region of auditory area 1. It is located ventral to and continuous with visual area 11, at about the caudal half of M. Rose's temporal cortices 1 and 2 (T1 and T2).Only about two‐thirds of 96 units studied responded to some sort of moving light stimulation. These motion‐sensitive cells were divided into four groups. Cells in the first group (22) responded best to a large light spot or shadow sweeping quickly across the field. Cells in the second group (29) responded to slow moving, jerking spot. Nine cells responded to a narrow, dark bar thrusting into a lighted field. Four cells are “direction‐selective,” responding to light stimulus moving in one direction and showing either no response or decreased background discharges in the oppsite direction. In addition, three cells required unusual stimulus features. Of the 38 cells tested, nine of them were found to be binocularly driven. These receptive field characteristics are quite different from those described for other visual centers of the rabbit. The significance of these results together with data on the anatomical connections of this cortical area as reported in the following paper were discussed.
Neuroanatomical aspects of the gerbil inner ear: Light microscope observations
Authors: Chamberlain Steven C. 
Published: December 2004

AbstractA specialization of the Mongolian gerbil inner ear allows easy access for electrophysiological recording from the auditory nerve and other structures of the internal auditory meatus. The round‐window membrane is recessed, creating a cavity connecting the bulla and the external wall of the modiolus. This cavity has been named the round‐window antrum. A small opening made in the dorsomedial wall of the round‐window antrum gives access directly to the modiolus and internal auditory meatus, with no other openings in the cranium required. This surgery is less drastic than that needed for similar access in most other mammals. The anatomy of the specialized region is presented from studied with the light microscope. Emphasis is placed on the relationship between external features of the wall of the round‐window antrum and the internal anatomy of the modiolus and internal auditory meatus. In addition, these studies reveal that cell bodies of the acoustic‐nerve nucleus are located in the auditory nerve, central to the glial dome. About 22 ± 8 cells are found in an auditory nerve. Their appearance with a Nissl stain is similar to cells found in rat, mouse, and man. The cell dendrites are preferentially oriented perpendicular to the longitudinal course of the auditorynerve fibers. The anatomy of the gerbil auditory system should allow direct electrophysiological recording from these cells.
Aging of the rat olfactory bulb: Growth and atrophy of constituent layers and changes in size and number of mitral cells
Authors: Hinds James W. , McNelly Nancy A. 
Published: December 2004

AbstractA quantitative study of the rat olfactory bulb during aging was carried out by directly measuring or calculating the following parameters at 3, 12, 24, 27, and 30 months: the volume of the glomerular, external plexiform, and internal granular layers, a relative measure of the size of the olfactory nerve layer, the mean volume of mitral cell nuclei and perikarya, a relative measure of the mean volume of the mitral cell dendritic tree as well as the total length and mean crosssectional area of its constituent dendrites, and number of mitral cells. In addition, measurements of the size and number of mitral cells in the accessory olfactory bulb were performed. Data were analyzed with analysis of variance, multiple range tests for differences between means at the various ages, and simple, partial, and multiple product‐moment correlations.From 3 to 24 months a linear increase of approximately 50% occurs in all layers of the olfactory bulb. During this time the mean perikaryal volume and dendritic volume of mitral cells increases, also in a linear fashion, approximately 100%. No significant change occurs in the number of mitral cells. From 24 to 30 months a significant decrease occurs in the volume of the layers. Although the total volume of mitral cell dendritic trees decreases slightly from 24 to 27 months, the volume of individual mitral cell dendritic treess, as well as perikaryal and nuclear size, increases sharply during this period, apparently in compensation for a sharp decrease in the number of mitral cells which occurs at this time. From 27 to 30 months no further decrease in mitral cell number occurs, but the size of mitral cell perikarya, and especially dendritic trees, decreases sharply.The coordinated increase in olfactory bulb size from 3 to 24 months appears to be a continuation into adult life of earlier postnatal increases. The atrophy from 24 to 30 months appears not to be associated with peripheral rhinitis, since the glomerular and olfactory nerve layers do not show greater atrophy than the other layers, and atrophy also occurs in the accessory olfactory bulb, which is supplied by nerves from the vomeronasal organ, a structure not normally subject to rhinitis.
The central projections in the retina in Necturus maculosus
Authors: Caldwell John H. , Berman Nancy 
Published: December 2004

AbstractThe projections of the retina in Necturus maculosus were studied by injecting radioactive proline into one eye. Labeling was seen in both the contralateral and ipsilateral diencephalon and tectum. The contralateral fibers are divided into three major tracts: the marginal, axial, and basal. The ipsilateral fibers separate into a marginal and an axial optic tract.The contralateral and ipsilateral axial optic tracts have a similar distribution. The contralateral and ipsilateral marginal optic tracts projecting to the diencephalon also have a similar distribution. However, in the tectum the ipsilateral marginal optic tract ends in the anterior third while the contralateral extends almost the entire length of the tectum. The retinotectal ipsilateral projection ends in clumps as has been described in other vertebrates. A direct ipsilateral retinotectal projection has not been described in any other amphibian.
Freeze‐fracture studies on the synapses in the organ of corti
Authors: Gulley R. L. , Reese T. S. 
Published: December 2004

AbstractReceptoneural junctions and synapses in the organ of Corti of the chinchilla have been examined with the freeze‐fracture technique. The presynaptic membranes at the receptoneural junctions of inner and outer hair cells have many structural features in common with membranes found at chemical synapses outside the organ of Corti. However, the membranes of the postsynaptic afferent terminals are quite different depending on whether they are part of an inner or outer hair cell synapse. These differences in the distribution of intramembrane particles suggest that the transmitters, or transmitter actions, may be different at these two synapses. The distribution of particles in the postsynaptic membrane at efferent synapses with outer hair cell differs from that in the postsynaptic membrane at efferent synapses with afferent terminals or fibers, suggesting that transmitter actions at these locations could also differ.
Unmyelinated axons in thoracic ventral roots of the cat
Authors: Emery Dennis G. , Ito Haruhide , Coggeshall Richard E. 
Published: December 2004

AbstractABSTRACT This study shows that approximately 30% of the axons in the Tll and T12 ventral roots of the cat are unmyelinated. The unmyelinated axons fall into two categories. Slightly less than half are efferents from the spinal cord and slightly more than half arise from dorsal root ganglion cells. The efferent fibers are regarded as unmyelinated preganglionic sympathetics, the fibers of dorsal root ganglion origin are regarded as sensory. This organization of the T11‐T12 ventral roots, which are part of the sympathetic outflow, is similar to that of cat ventral roots S3 and Cal, which are part of the parasympathetic outflow, but different from cat ventral roots L7 and Sl, which are between the visceral outflows.
Bilateral ganglion cell branches in the normal rat: A demonstration with electrophysiological collision and cobalt tracing methods
Authors: Cunningham Timothy J. , Freeman John A. 
Published: December 2004

AbstractThe application of microelectrode recording and anatomical tracing methods to the subcortical optic projections of the normal rat shows that the uncrossed pathway from the retina of this mammal is substantially composed of branches of crossed axons. In the recording experiments, paired stimuli to the optic tracts produces an attenuated antidromic response in the optic nerve which is best explained by the collision of impulses which travel in branches of the same parent axon. Cobalt injection of one optic tract results in retrograde filling of axons in the entire contralateral optic nerve and filling of axons in restricted regions of the ipsilateral optic nerve. This procedure also results in the filling of axons in the opposite optic tract. The locations of the filled axons in the opposite tract correspond to the positions of crossed and uncrossed projections from the temporal retinae: ventrolateral and dorsomedial, respectively. The position of the temporal retinal projections in both optic tracts was determined by applying silver degeneration methods after small lesions of the retina.
The effect of superior colliculus lesions upon the visual fields of cats with cortical ablations
Authors: Sherman S. Murray 
Published: December 2004

AbstractThe visual fields of 18 cats were measured before and after various lesions. Preoperatively, all cats had identical fields. With both eyes open, they saw from 90° left to 90° right; with one eye, from 90° ipsilateral to 45° contralateral. Thus the field for nasal retina extends from 90° ipsilateral through to the midline; for temporal retina, from the midline through to 45° contralateralIn summary, postoperative testing led to two major conclusions. (1) Large occipito‐temporal cortical lesions produce a stable field blindness, but the blindness is alleviated by a transection of the commissure of th superior colliculus (or a unilateral collicular ablation). This transaction yields the same result whether it occurs in an operation before, during, or after the cortical lesion. These data confirm and extend the Sprague effect. (2) Cats made dependent upon retinotectal pathways due to cortical ablations responded much better to stimulatian of nasal retina than to stimulation of temporal retina. This presumably is related to the preponderance of nasal retina as a source of the retinotectal pathway. Since even smaller cortical lesions limited to areas 17, 18, and 19 produce this nasal/temporal retinal difference, it is concluded that integrity of the geniculocorticl pathways is necessary for good temporal retinal vision as determined by these methods.
The vestibular complex of the american opossum, Didelphis virginiana. I. Conformation, cytoarchitectur and primary vestibular input
Authors: Henkel C. K. , Martin G. F. 
Published: December 2004

AbstractDegeneration experiments reveal that the vestibular nerve of the adult opossum distributes to an extensive and diverse area of the brainstem and, as in placental mammals, the traditionally named nuclei do not receive a uniform distribution of primary afferent fibers. Nevertheless, such nuclei as well as other nearby cell groups have been considered as vestibular since they share other mutual connections. Except for subgroups. “1”, “g” and the nucleus suprvestibularis all of the vestibular subdivisions generally recognized in more specialized placentals (e.g., the cat) have been identified in the marsupial opossum.Each of the vestibular nuclei and “extra‐nuclear” cell stations are described as to their boundaries, cytoarchitecture and dendritic domain. Whenever possible we have employed a terminology consistent with that used for the cat. In several instances we have used results from experimental degeneration material to identify nuclear boundaries and divisions which are not apparnt in routine Nissl, Golgi or silver preparations.