bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differentiation of photoreceptors and horizontal cells in the embryonic mouse retina: An electron microscopic, serial section analysis
Authors: Hinds James W. , Hinds Patricia L. 
Published: January 2005

AbstractThe early differentiation of photoreceptors and horizontal cells in the mouse retina has been studied with serial thin sections and reconstructions in embryos on the fifteenth and seventeenth days of gestation (E15 and E17). The following developmental sequences have been inferred. At E15 photoreceptors develop from ventricular cells when a long vitreal process fails to develop following mitosis, and the end of the ventricular process forms a bulbous enlargement (the future inner segment) which contains a pair of centrioles and a cilium and extends into the optic ventricle. This future inner segment is considerably larger at E17, but otherwise the photoreceptors resemble those seen at E15. At E15 horizontal cells develop from ventricular cells when a long vitreal process fails to develop following mitosis, and the end of the ventricular process detaches from the junctional complex at the ventricular surface. By E17 future horizontal cells are located in the middle of the ventricular layer (neuroblastic layer) and have developed from bipolar shaped cells into cells with multiple branching processes, predominantly radially arranged but rarely with a more tangential orientation. These relatively advanced cells at E17 resemble closely the earliest stage of horizontal cell formation described previously in silver studies by Cajal.A scheme is proposed which explains the initial differentiation of several of the major cell types in the retina in terms of two key features: whether or not the cell remains attached to the junctional complex and whether or not a vitreal process grows into the ganglion cell layer. By independent variations in these two features, four classes of cells are produced that, by virtue of their differing environments, differentiate into four cell types: ganglion (and amacrine) cells, horizontal cells, photoreceptors, and Müller cells.
Efferent connections of the brainstem trigeminal complex with the facial nucleus of the rat
Authors: Erzurumlu Reha S. , Killackey Herbert P. 
Published: January 2005

AbstractThe sensory surface of the face of the rat is topographically represented in the brainstem trigeminal complex (Nord, '67), and in parallel with this the underlying facial musculature is also represented in a topographic fashion in the facial nucleus (Papez, '27; Martin and Lodge, '77; Watson and Sakai, '78). It has been recently reported that in the young rat three distinct representations of the vibrissae are present in the sensory portion of the brainstem trigeminal complex (Belford and Killackey, '79). Within this perspective, the specific connectivity between the brainstem trigeminal complex and the facial nucleus was investigated in adult rats by the Fink‐Heimer technique.The two major sensory nuclei of the brainstem trigeminal complex, the spinal trigeminal nucleus and the principal sensory nucleus, differ in their projection patterns to the facial nucleus. While the principal sensory nucleus sends sparse projections to the ipsilateral lateral and dorsal subdivisions of the facial nucleus, the spinal trigeminal nucleus sends differential projections to various subdivisions of the facial nucleus depending on their origin with respect to three cytoarchitectonically different subnuclei that compose the spinal trigeminal nucleus. It is concluded that the magnocellular portion of subnucleus caudalis projects rather heavily to the ipsilateral lateral subdivision of the facial nucleus, while the projections from the subnucleus interpolaris are sparser and distributed more widely to parts of the lateral, dorsal and intermediate subdivisions of the facial nucleus ipsilaterally. In contrast to ipsilateral facial projections from the rest of the brainstem trigeminal complex, the projections from the subnucleus oralis of the spinal trigeminal nucleus are bilateral and confined to the intermediate subdivision of the facial nucleus. However, ipsilateral projections of the subnucleus oralis are denser than the very sparse contralateral projections.In addition to the facial projections from the brainstem trigeminal complex, projections from the upper portions of the cervical cord to the medial subdivision of the facial nucleus were observed. These projections are bilateral, and those fibers destined for the contralateral medial subdivision cross over below the level of the pyramidal decussation.
Cells of origin of long descending propriospinal fibers connecting the spinal enlargements in cat and monkey determined by horseradish peroxidase and electrophysiological techniques
Authors: Skinner Robert D. , Coulter Joe Dan , Adams Robert J. , Remmel Ronald S. 
Published: January 2005

AbstractThe cells of origin of the long descending propriospinal tract (LDPT) in the cervical enlargement were studied in cat and monkey by using the retrograde transport of horseradish peroxidase (HRP). Their distribution was confirmed electrophysiologically in cat by recording their antidromic action potentials.In cats and monkeys unilateral injections of HRP were made into the gray matter of the lumbosacral enlargement, but there was some spread to the contralateral side. In cats labeled somas were found in greatest numbers in lamina VIII and medial lamina VII, bilaterally. Labeled cells also were found bilaterally in laminae I, IV–VI, and X, but few were in IV and VI. Those in lamina V were usually in the lateral part of the lamina near the reticulated region. The cross‐sectional areas of 20 neurons from each of laminae I and V–VIII were measured. Cells in lamina I were smallest and the largest were in VII and VIII.In cats with the spinal cord hemisected between the injection site and the cervical enlargement containing the somas, the bilaterality of the LDPT neurons in laminae VII and VIII was confirmed anatomically and physiologically. Contralaterally projecting neurons in laminae VIII and medial VII constituted a majority of LDPT cells in those laminae. The LDPT neurons in the dorsal horn appeared to project mainly ipsilaterally, but the number of labeled dorsal horn cells in these preparations was small.The distribution of antidromically localized cells of the LDPT was found to be in good agreement with the anatomical results. Their conduction velocity was 59 ± 22 m/s (mean ± s. d., n = 245). Histograms of the conduction velocity by laminae are given.In monkey the distribution of labeled somas was similar to that in the cat, except that the concentration of labeled somas in the ventral horn was more medially and dorsally located. Labeled somas were found bilaterally in laminae I, IV – VIII, and X, but more appeared to be ipsilateral to the side of the injection, especially in the dorsal horn. The bilaterality of the LDPT in the monkey was not tested with hemisections of the spinal cord.Neurons of the LDPT are ideally situated for conveying sensory information from the forelimb for eliciting reflexes in the hindlimb, as has been observed after stimulating afferents in the forelimb, and for coordinating, in general, motor functions between the two pairs of limbs.
A technique for estimating total spine numbers on golgi‐impregnated dendrites
Authors: Feldman Martin L. , Peters Alan 
Published: January 2005

AbstractThe functional significance of dendritic spines and their morphological sensitivity to a wide spectrum of experimental manipulations and pathological states have led to a number of studies in which counts of dendritic spine number have been carried out. These studies have, for the most part, involved the enumeration of only those spines which protrude from the opaque shafts of Golgi‐impregnated dendrites into the clear zones flanking the dendrite. Such counts, limited to only those spines which are visible, underrepresent the true total number of spines borne by the dendrites. The magnitude of underrepresentation correlates positively with dendritic shaft diameter and negatively with spine length. This seriously restricts the usefulness of comparisons of spine density between dendrites, or even between segments of the same dendrite.In the present report, a geometrically based method is presented whereby total dendritic spine numbers can be estimated with reasonable accuracy, taking into account factors such as dendrite diameter and spine length. The technique entails the following principal steps: a determination, for a given length of dendrite over which spines are to be enumerated, of the volume of the flanking zones in which spines are visible and can be counted; a determination of the volume of the entire zone which encircles the dendritic shaft and which contains all spines, both visible and not visible; and a proportional extrapolation from the number of visible spines to obtain an estimate of the true total spine number. Tests of the predictive accuracy of the technique using dendrites of known total spine number suggest that estimates which deviate from true total spine numbers by less than 10% can be achieved.
Nuclei in which functionally identified spinothalamic tract neurons terminate
Authors: Applebaum A. E. , Leonard R. B. , Kenshalo D. R. , Martin R. F. , Willis W. D. 
Published: January 2005

AbstractThe approximate level of termination of the axons of individual, functionally characterized spinothalamic tract neurons within the monkey thalamus was mapped by antidromic activation using a monopolar electrode which was moved in a systematic grid of tracks through the thalamus. The course of individual axons could be followed through several thalamic levels, and in a few cases branches to both the VPL nucleus and to the intralaminar nuclei were demonstrated. Most of the axons studied, however, projected just to the VPLc or VPLo nuclei. The spinothalamic tract cells that projected to the VPLc nucleus included representatives of all known functional categories: low threshold, wide dynamic range, high threshold and “deep”. It is speculated that these different classes of spinothalamic projections could make contributions to such sensory modalities as touch, proprioception and pain.
Anatomy and ultrastructure of the axons and terminals of neurons R3‐R14 in Aplysia
Authors: Price Christopher H. , McAdoo David J. 
Published: January 2005

AbstractUsing light and electron microscopy and autoradiography, we have traced the axons of neurons R3‐R14 in the parietovisceral ganglion (PVG) of Aplysia to terminal fields associated with vascular tissue. The axons are identified by their large size (15‐30 μm diameter), extensive glial infolding, characteristic dense core vesicles (DCV; ∼180 nm diameter), and specific, rapid uptake of 3H‐glycine. Each neuron in this homogeneous group sends an axon via the branchial nerve to the pericardial region surrounding the junction of the efferent gill vein and the heart. R14 also sends axons to major arteries near the PVG. The R3‐R14 axons branch extensively; we estimate that there are at least several hundred per cell. Branches along axons in the branchial nerve exit the nerve, subdivide, and end blindly in the sheath which is bathed by hemolymph. Similar blind endings from R3‐R14 occur in the sheath of the PVG (Coggeshall, '67). Axonal branches in the pericardial region and the special R14 axons in the arterial walls from both varicose endings near and terminals in contact with vascular smooth muscle. All R3‐R14 endings are free of glia, packed with DCV, show occasional omega‐shaped profiles and rapidly take up 3H‐glycine. R3‐R14 manufacture specific low molecular weight peptides (Gainer and Wollberg, '74), and both the cell bodies (Iliffe et al., '77) and the terminals contain unusually high concentrations of glycine. The presence of peptides as putative neurohormones and sheath endings (neurohormonal release areas) are consistent with R3‐R14 being neurosecretory (Coggeshall et al., '66). While glycine could not be a circulating hormone due to its high circulating levels (Iliffe et al., '77), glycine could act as a local chemical messenger between R3‐R14 and smooth muscle. The terminal morphology of R3‐R14 is consistent with these neurons having both synaptic‐type and neurosecretory‐type functions.
Early development and migration of the trigeminal motor nucleus in the chick embryo
Authors: Heaton Marieta B. , Moody Sally A. 
Published: January 2005

AbstractThe development of the trigeminal motor nucleus in the chick embryo was studied using autoradiographic, cell staining, fiber staining, and axonal transport techniques. It was found that this nucleus arises very early in neurogenesis, with the first cells produced at 48 hours of incubation (stage 12), peak cell production at 50–56 hours (stage 15), and neuroblast proliferation completed by 72 hours (stage 18). As has been described in mammalian embryos, the primordial trigeminal cells move from the ventricular layer to accumulate as part of the common medial column, and later migrate in a ventrolateral direction to form the definitive lateral motor nucleus. The first identifiable component of the trigeminal system is the semilunar ganglion, which flanks the neural tube at stage 12, and sends afferents into the metencephalon by stage 13. By stage 12–13, the medial column cells are first apparent, and at stage 14, a few of these medial column cells have moved to begin formation of a lateral nucleus. At this time, a thin motor root can be seen exiting the brainstem. During subsequent stages, migratory traffic from medial to lateral regions increases, with cells frequently moving in association with fiber processes in the marginal zone. These fibers are presumed to emanate from secondary sensory, reticular, and medial column neuroblasts. By day 5, the medial column is greatly depleted and by day 6–7, the definitive lateral motor nucleus is formed. Beginning at 5 days, the dorsal motor nucleus can be detected, with cells from the lateral nucleus appearing to stream in a dorsomedial direction for its formation. Injections of horseradish peroxidase (HRP) into the mandibular process of the first visceral arch resulted in retrograde labeling of lateral nucleus cells as early as 3.5 days of incubation. In addition, migrating cells, intermediate between medial column and lateral nucleus, were similarly labeled. These observations indicate that processes of the lateral nucleus cells and those of migrating cells are well into their peripheral field at this age, but we cannot conclude that neuromuscular affiliations have been established, due to the possibility of HRP diffusion and growth cone uptake.
Neuronal transport of acid hydrolases and peroxidase within the lysosomal system of organelles: Involvement of agranular reticulum‐like cisterns
Authors: Broadwell Richard D. , Oliver Constance , Brightman Milton W. 
Published: January 2005

AbstractNeurosecretory neurons of the hyperosmotically stressed hypothalamo‐neurohypophysial system have been a useful model with which to demonstrate interrelationships among perikaryal lysosomes, agranular reticulum‐like cisterns, endocytotic vacuoles, and the axoplasmic transport of acid hydrolases and horseradish peroxidase. Supraoptic neurons from normal mice and mice given 2% salt water to drink for 5–8 days have been studied using enzyme cytochemical techniques for peroxidase and lysosomal acid hydrolases. Peroxidase‐labeling of these neurons was accomplished by intravenous injection or cerebral ventriculocisternal perfusion of the protein as previously reported (Broadwell and Brightman, '79).Compared to normal controls, supraoptic cell bodies from hyperosmotically stimulated mice contained elevated concentrations of peroxidase‐labeled dense bodies demonstrated to be secondary lysosomes and acid hydrolase‐positive and peroxidase‐positive cisterns either attached or unattached to secondary lysosomes. These cisterns were smooth‐surfaced and 400–1,000 A wide. Their morphology was similar to that of the agranular reticulum. Some of the cisterns contained both peroxidase and acid hydrolase activities. The cisterns probably represent an elongated form of lysosome and, therefore, are not elements of the agranular reticulum per se. By virtue of their direct connections with perikaryal secondary lysosomes, these cisterns may provide the route by which acid hydrolases and exogenous macromolecules can leave perikaryal secondary lysosomes for anterograde flow down the axon. Very few smooth‐surfaced cisterns were involved in the retrograde transport of peroxidase within pituitary stalk axons from normal and salt‐treated mice injected intravenously with peroxidase. Peroxidase undergoing retrograde transport was predominantly in endocytotic structures such as vacuoles and cupshaped organelles, which deliver this exogenous macromolecule directly to secondary lysosomes for degradation in the cell body.These observations extend our previously reported findings in the axon to the cell body and suggest that agranular reticulum‐like cisterns in the perikaryon, like those in the axon, may be part of the lysosomal system rather than associated with the agranular reticulum. A diagram summarizing the lysosomal system of organelles and proposed transport of acid hydrolases and peroxidase in neurosecretory neurons specifically and in neurons in general is provided.
Cytoarchitectonic organization of the human auditory cortex
Authors: Galaburda Albert , Sanides Friedrich 
Published: January 2005

AbstractA new cytoarchitectonic study of the human auditory cortex was undertaken in the light of recent knowledge concerning the architecture, fiber connectivity, and physiology of this region in the monkey. The survey of three normative human brains (six hemispheres) processed in whole‐brain serial sections disclosed a cytoarchitectonic organization of the cortical auditory region similar to that in the macaque. Unlike the monkey, auditory‐related cortex was found in parietal operculum and inferior parietal lobule. Similarities in cortical architectonics between human and monkey brains may provide a rationale for the application of knowledge concerning animal physiology and connectivity to man.
Cytoarchitecture of the optic tectum of the squirrelfish, Holocentrus
Authors: Schroeder Dolores M. , Vanegas Horacio , Ebbesson Sven O. E. 
Published: January 2005

AbstractThe Holocentrus has large eyes and a well‐developed optic tectum. Nissl and fibers stains and various Golgi techniques show that the optic tectum of Holocentrus has six strata which can be subdivided into 14 alternative cell and fiber layers, some of which have additional organization. The stratum marginale (SM) is especially impressive in this fish and contains dendrites of pyramidal neurons, marginal fibers from torus longitudinalis, and axon‐like processes (the SM ascending axons) from cell located in the stratum griseum centrale (SGC). Stratum opticum (SO) and stratum fibrosum et griseum superficiale (SFGS) have many small neurons with limited dendritic fields. The large, so‐called pyramidal cell of SFGS has an extensive dendritic tree in SM and descending dendrites and axon to SGC. The latter has a variety of neurons with large dendritic fields in various layers of the tectum; the most distinctive, however, is the large fusiform neuron with its shepherd's crook axon. This stratum also has a dense layer of neuropil, the internal plexiform layer. Stratum album centrale (SAC) is primarily a fibrous layer, and stratum periventriculare (SPV) is a dense cellular area with the upper portion containing neuronal types also found in SGC and different from the typical neurons found in SPV. The latter have a major ascending branch with various dendritic patterns, and often do not have an identifiable axon; however, some of these cells have extensive branches throughout SFGS with an axon‐like appearace. Some general conclusions were made about the functional significance of the various tectal layers and cell types.
Origins of crossed and uncrossed retinal projections in pigmented and albino mice
Authors: Dräger Ursula C. , Olsen John F. 
Published: January 2005

AbstractThe extent of the binocular cortical field in albino mice, as revealed by recording from single cells, was almost normal; although the input from the ipsilateral eye was weaker than normal, most cells were driven from both eyes. By backfilling retinal ganglion cells from one optic tract with horseradish peroxidase we examined the origins of the retinofugal projections. Filled cells ipsilateral to the injected tract were concentrated in a crescent‐shaped area bordering the inferior temporal retina. In black mice this area constituted 20% of the total retinal area, in albinos 17%. In black mice we counted nearly 1,000 labeled cell in the ipsilateral retina, or 2.6% of all cells filled in both eyes. Albinos had about one‐third fewer filled cells ipsilaterally than black mice. Four percent of all ipsilaterally filled cells in black mice and 8% in albinnos were scattered outside of the crescent region. The density of ipsilaterally projecting cells was uniform throughout the crescent region in black mice, but decreased toward the central retina in albinos.In retinas contralateral to the injection up to 39,000 cells were filled—about two‐thirds of the cells in the ganglion‐cell layer whose cytoplasm contained conspicuous Nissl substance. Depending on classification of unfilled cells as ganglion cells or interneurons, we estimated a total 48,000 to 65,000 ganglion cells to exist in the retina.The size distribution of ipsilateraly projecting ganglion cells was similar in albinos and normals. Ipsilaterally projecting ganglion cells were on average 1.8–3 times larger in volume than contralaterally projecting ones in both types of mice.Displaced ganglion cells were relatively more common in ipsilateral retinofugal projections: 21% of all ipsilateral ganglion cells were displaced versus less than 1% of all the contralateral ganglion cells in black mice. In albinos only 13% of the ganglion cells in the ipsilateral retina were displaced. The overall reduction in ipsilaterally projecting cells in albinos was reflected twice as much in displaced ganglion cells as in normally placed ones.