bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anatomical and physiological characteristics of vestibular neurons mediating the horizontal vestibulo‐ocular reflex of the squirrel monkey
Authors: McCrea R. A. , Strassman A. , May E. , Highstein S. M. 
Published: January 2005

AbstractThe anatomical characteristics of vestibular neurons, which are involved in controlling the horizontal vestibulo‐ocular reflex, were studied by injecting horseradish peroxidase (HRP) into neurons whose response during spontaneous eye movements had been characterized in alert squirrel monkeys. Most of the vestibular neurons injected with HRP that had axons projecting to the abducens nucleus or the medial rectus subdivision of the oculomotor nucleus had discharge rates related to eye position and eye velocity.Three morphological types of cells were injected whose firing rates were related to horizontal eye movements. Two of the cell types were located in the ventral lateral vestibular nucleus and the ventral part of the medial vestibular nucleus (MV). These vestibular neurons could be activated at monosynaptic latencies following electrical stimulation of the vestibular nerve; increased their firing rate when the eye moved in the direction contralateral to the soma; had tonic firing rates that increased when the eye was held in contralateral positions; and had a pause in their firing rate during saccadic eye movements in the ipsilateral or vertical directions. Eleven of the above cells had axons that arborized exclusively on the contralateral side of the brainstem, terminating in the contralateral abducens nucleus, the dorsal paramedian pontine reticular formation, the prepositus nucleus, medial vestibular nucleus, dorsal medullary reticular formation, caudal interstitial nucleus of the medial longitudinal fasciculus, and raphé obscurus. Eight of the cells had axons that projected rostrally in the ascending tract of Deiters and arborized exclusively on the ipsilateral side of the brainstem, terminating in the ipsilateral medial rectus subdivision of the oculomotor nucleus and, in some cases, the dorsal paramedian pontine reticular formation or the caudal interstitial nucleus of the medial longitudinal fasciculus.Two MV neurons were injected that had discharge rates related to ipsilateral eye position, generated bursts of spikes during saccades in the ipsilateral direction, and paused during saccades in the contralateral direction. The axons of those cells arborized ipsilaterally, and terminated in the ipsilateral abducens nucleus, MV, prepositus nucleus, and the dorsal medullary reticular formation. The morphology of vestibular neurons that projected to the abducens nucleus whose discharge rate was not related to eye movements, or was related primarily to vertical eye movements, is also briefly presented.
Development of the preoptic area: Time and site of origin, migratory routes, and settling patterns of its neurons
Authors: Bayer Shirley A. , Altman Joseph 
Published: January 2005

AbstractNeurogenesis and morphogenesis in the rat preoptic area were examined with [3H] thymidine autoradiography. For neurogenesis, the experimental animals were the offspring of pregnant females given an injection of [3H]thymidine on two consecutive gestational days. Nine groups were exposed to [3H]thymidine on embryonic days E13–E14, E14–E15, E21–E22, respectively. On postnatal day P5, the percentage of labeled cells and the proportion of cells originating during 24‐hr periods were quantified at four anteroposterior levels in the preoptic area. Throughout most of the preoptic area there is a lateral to medial neurogenetic gradient. Neurons originate between E12–E15 in the lateral preoptic area, between E13–E16 in the medial preoptic area, between E14–E17 in the medial preoptic nucleus, and between E15–E18 in the periventricular nucleus. These structures also have intrinsic dorsal to ventral neurogenetic gradients. There are two atypical structures: (1) the sexually dimorphic nucleus originates exceptionally late (E15–E19) and is located more lateral to the ventricle than older neurons; (2) in the median preoptic nucleus, where older neurons (E13–E14) are located closer to the third ventricle than younger neurons (E14–E17).For an autoradiographic study of morphogenesis, pregnant females were given a single injection of [3H] thymidine during gestation, and their embryos were removed either two hrs later (short survival) or in successive 24‐hr periods (sequential survival). Short‐survival autoradiography was used to locate the putative neuroepithelial sources of preoptic nuclei, and sequential survival autoradiography was used to trace the migratory waves of young neurons and their final settling locations. The preoptic neuroepithelium is located anterior to and in the front wall of the optic recess. The neuroepithelium lining the third ventricle is postulated to contain a mosaic of spatiotemporally defined neuroepithelial zones, each containing precursor cells for a specific structure. The neuroepithelial zones and the migratory waves originating from them are illustrated. Throughout most of the preoptic area, neurons migrate predominantly laterally. The older neurons in the lateral preoptic area migrate earlier and settle adjacent to the telencephalon. Younger neurons migrate in successively later waves and accumulate medially. The sexually dimorphic neurons are exceptional since they migrate past older cells to settle in the core of the medial preoptic nucleus. The median preoptic nucleus originates from a midline neuroepithelial zone that is continuous with the neuroepithelium in the midline basal telencephalon, and is, therefore, considered to represent a transitional area between the telencephalon and the diencephalon.
Dual control by targets and afferents of developmental neuronal death in the mammalian central nervous system: A study in the parabigeminal nucleus of the rat
Authors: Linden Rafael , Piñon Luzia G. P. 
Published: January 2005

AbstractNatural and induced cell degeneration were studied in the mesencephalic parabigeminal nucleus of postnatally developing rats. Natural cell death in the normal parabigeminal nucleus had already started at birth, was maximal at 3 days, and proceeded with a declining rate until postnatal days 8–10 in the dorsal, middle, and ventral divisions that compose the nucleus. The number of neurons declined by approximately one‐third between birth and postnatal day 15. A unilateral lesion of the superior colliculus made at birth modified this pattern. In the deafferented ipsilateral middle division, the rate of cell death was above normal from day 1 to day 10, and the number of neurons at day 15 was 60% less than in unoperated controls. In the contralateral middle division, in which at least some of the neurons were axotomized by the lesion, the rate of cell death increased at days 1–2 and decreased below normal at days 3–5. Induced changes in the number of neurons were consistent with this pattern, and at day 15 the number was similar to the control value. In the ipsilateral dorsal and ventral divisions, which suffered simultaneous axotmy and deafferentation, the rate of cell death increased in 2 peaks at days 1–2 and 4–6, and the numbers of neurons dropped to negligible values at day 15. The frequency curves of degenerating cells were poor predictors of the absolute changes in neuron numbers, and evidence was found of continued postnatal migration of neurons into the developing parabigeminal nucleus. This study indicated that retrograde and anterograde degeneration cotemporal with natural cell death in the developing parabigeminal nucleus proceed with distinct time courses and interact when induced simultaneously. The nucleus regulates through a reduction in the rate of cell death after an early depletion of neurons caused by axotomy, as long as the tectal input remains intact. The results support the hypothesis that the afferent supply, as well as the integrity of axons, have major roles in the control of neuronal survival in the developing brain.
Retinal ganglion cell morphology in the frog, Rana pipiens
Authors: Frank Bennett D. , Hollyfield Joe G. 
Published: January 2005

AbstractThe morphology of retinal ganglion cells in the frog, Rana pipiens, has been examined in retinal flatmounts following backfilling of axons with horseradish peroxidase (HRP). Size and shape of the cell body and of the dendritic arbor, the dendritic branching pattern, and the depth of dendritic arborization within the inner plexiform layer (IPL) were all used to classify these cells. All of the ganglion cells so visualized can be grouped into one of 7 distinct cell classes. Class 1 contains the largest ganglion cells, with a soma size of 323 ± 5.3 μm2 and dendritic fields of 86,819 ± 11,817 μm2; the dendrites branch within strata 1 and 2 of the IPL. The second largest cells are class 2, with somas of 245 ± 19.7 μm2 and dendritic fields of 55,983 ± 7,392 μm2; the dendrites also branch within strata 1 and 2 of the IPL. Class 3 cells are the next largest class with somas of 211 ± 11.8 μm2 and dendritic fields of 18,186 ± 1,394 μm2; there are three varieties of class 3 cells based on the depth of branching of the dendrites: some cells are bistratified, others are tristratified, while still other cells arborize diffusely within the IPL. Class 4 cells are intermediate in size, with somas of 113 ± 7.4 μm2 and dendrites of 4800 ± 759 μm2; the dendrites arborize within strata 4 and 5 of the IPL. Class 5 cells have not been quantititively analyzed because they are heterogeneous in soma and dendritic size. However, class 5 cells all have cell bodies displaced in location into the inner nuclear layer and all have a unique dendritic specialization: they send from 1 to 3 processes into the outer plexiform layer. Class 6 cells are the second smallest cell class with somas of 68.1 ± 5.13 μm2 and dendritic fields of 888 ± 182 μm2; the dendrites arborize within strata 3, 4, and 5 of the IP. Class 7 contains the smallest ganglion cells with somas of 62.1 ± 2.86 μm2; and dendritic fields of 831 ± 74.2 μm2; the dendrites arborize within strata 3, 4, and 5 of the IPL. The frequency of each cell class is inversely proportional to the size of the dendritic field. Thus, class 7 cells are the most frequent; class 1 cells are the least frequent. Furthermore, each of these 7 classes of ganglion cells has representative cells located in the inner nuclear layer. The majority of these displaced ganglion cells are located in the central retina, within a horizontal streak just dorsal to the optic nerve head. The various morphological types of ganglion cells we observe may provide the structural basis for the diversity of frog ganglion cell receptive field types.
Trajectories of regenerating retinal axons in the goldfish tectum: II. Exploratory branches and growth cones on axons at early regeneration stages
Authors: Stuermer Claudia A. O. 
Published: January 2005

AbstractHRP was applied to small sites in the dorsotemporal or dorsonasal retina in fish at 10–36 days after optic nerve section. The anterogradely labeled axons were visualized in tectal whole mounts.Axons traveled through all regions of the tectum in various abnormal routes. Misrouted axons were also seen to alter their orientation and to direct their course toward their target. At all regeneration stages the majority of dorsotemporal axons coursed and achieved target‐related orientations preferentially within the rostral tectal half whereas dorsonasal axons proceeded into the caudal tectum.The growing axons exhibited various morphologies. All axons in the superficial fascicle layer stratum opticum (SO) and some in the synaptic layer stratum fibrosum et griseum superficiale (SFGS) were unbranched and tipped with a leading growth cone. Other axons in the synaptic layer carried one to several growth cones at their ends and often filopodia proximal to the growth cone, or they had sprouted numerous side branches with growth cones and filopodia on the shaft and on branches. Some axons at retinotopic or ectopic sites gave rise to several long branches of several hundred microns in length, with growth cones and filopodia. From 32 days onward axons ending in terminal arbors at retinotopic sites became apparent. Thus, numerous axons at early regeneration stages go through a phase of exploratory growth on their way toward their target sites.
The process of reinnervation in the dentate gyrus of adult rats: An ultrastructural study of changes in presynaptic terminals as a result of sprouting
Authors: Steward Oswald , Vinsant Sharon L. , Davis Lauren 
Published: January 2005

AbstractThe present study was undertaken to define the ultrastructure of synapses of the crossed temporodentate pathway after they had sprouted to reinnervate the dentate gyrus following the destruction of the normal ipsilateral temporodentate pathway. The synapses of the sprouted crossed temporodentate pathway were identified at the EM level by using autoradiographic techniques and by evaluating the degeneration of the pathway following secondary lesions. Both EM autoradiography and EM degeneration revealed that the terminals of the sprouted crossed temporodentate pathway formed asymmetric synapses on spines; individual terminals appeared to make more synaptic contacts per terminal (multiple synapses) than in the case of the normal crossed pathway. In the two lesioned animals exhibiting the best labeling, labeled terminals made an average of 3.0 ± 2.2 and 2.0 ± 1.3 contacts per terminal. In contrast, labeled terminals in normal animals exhibited only one contact per terminal. The terminals of the sprouted pathway were also larger than those of the normal crossed pathway. The synapses of the crossed temporodentate pathway that degenerated after a secondary lesion of the entorhinal cortex exhibited both electron‐lucent and electron‐dense forms of degeneration at 2 days postlesion. In two animals that were quantitatively analyzed, the density of degenerating synaptic terminals was 281 and 218/10,000 μm2 in the terminal field of the sprouted crossed pathway. These values are much higher than in normal animals, where the density of degenerating synaptic terminals was only 2.12/10,000 μm2 at 2 days postlesion. Because degenerating terminals were evident at 2 days postlesion, the sprouted crossed pathway does not appear to exhibit the very rapid degeneration that is characteristic of the normal crossed pathway. We conclude that sprouting in this pathway involves terminal proliferation (an increase in the number of presynaptic elements), and terminal hypertrophy (an increase in the size of presynaptic terminals, together with an increase in the number of synaptic contacts formed by individual terminals).
Morphology of physiologically identified mitral cells in the carp olfactory bulb: A light microscopic study after intracellular staining with horseradish peroxidase
Authors: Fujita Ichiro , Satou Masahiko , Ueda Kazuo 
Published: January 2005

AbstractPhysiologically identified mitral cells in the carp olfactory bulb were stained by intracellular injection of horseradish peroxidase in order to study the morphology in detail.The somata were fusiform, elongated, oval, triangular, or irregular. The mean diameters of the somata were 30 μm × 14 μm. Two to five thick dendrites arose from the somata and frequently gave off branches to form glomerular tufts. The dendrites extended less than 400 μm; the dendritic field of single mitral cells in the medial or lateral part of the olfactory bulb was confined within the respective part of the bulb. The axons arose from either the somata or the dendrites and had a conical initial portion, usually with a smooth contour. Some cells had poorly developed intrabulbar axon collaterals. No difference between the mitral cells in the medial part of the olfactory bulb and those in the lateral part was found in the soma diameter, the dendritic diameter at the base, or the number of first‐order dendrites. However, there was a difference in the site of the origin of the axon between them: most of the axons of the mitral cells in the medial part arose from the dendrites, while most of the axons of the mitral cells in the lateral part arose from the somata.The morphology of physiologically identified mitral cells is basically consistent with that reported in the Golgi studies of teleosts. The limited dendritic fields of mitral cells may underlie the previously reported functional separation of the olfactory bulb into medial and lateral parts. The results also indicate that the two parts of the teleost olfactory bulb are differentiated not only functionally but also morphologically.
Identification of synaptic terminals of thalamic or cortical origin in contact with distinct medium‐size spiny neurons in the rat neostriatum
Authors: Dubé Lorraine , Smith A. David , Bolam J. Paul 
Published: January 2005

AbstractIn order to determine what types of neurons in the striatum receive direct synaptic input from corticostriatal and thalamostriatal fibres and whether these afferents converge on individual striatal neurons, double anterograde labelling of axon terminals was combined with Golgi impregnation at both the light and electron microscopic levels.The area of the central neostriatum that receives input from both the parafascicular nucleus of the thalamus and the somatosensory cortex was identified by retrograde transport of a conjugate of horseradish peroxidase and wheat germ agglutinin (HRP‐WGA). The same region of the neostriatum was studied in rats that had received multiple electrolytic lesions in the somatosensory cortex and also an injection of HRP‐WGA in different parts of the parafascicular nucleus. Sections of this part of the neostriatum were impregnated by the single‐section Golgi procedure after revealing anterogradely transported HRP‐WGA. Twelve Golgi‐impregnated spiny neurons were recovered and examined in the light and electron microscope after gold‐toning. Ten of these neurons were typical very densely spiny medium‐size neurons and they were all found to receive asymmetric synaptic input on dendritic spines from degenerating corticostriatal boutons. However, even though numerous boutons labelled anterogradely by HRP‐WGA from the parafascicular nucleus were found within the dendritic fields of neurons that received cortical input, none of the terminals from the thalamus made synaptic contact with these neurons. Instead, all 96 thalamostriatal boutons studied were found in asymmetric synaptic contact with dendritic shafts of other neurons. Two such neurons that received input from the parafascicular nucleus were Golgi‐impregnated and appeared to be medium‐size spiny neurons, but they had a lower density of spines than the typical very densely spiny neurons. An independent confirmation that the targets of thalamostriatal neurons originating in the parafascicular nucleus are dendritic shafts was provided by studying the boutons labelled following electrolytic lesioning or injection of the lectin Phaseolus vulgaris‐leucoagglutinin (PHA‐L) into this nucleus: these boutons were also found to form asymmetric synaptic contacts with dendritic shafts within the neostriatum.It is concluded that although afferents from the somatosensory cortex and from the parafascicular nucleus converge upon the same part of the neostriatum, they probably do not converge upon the same spiny neurons. The afferents from the neocortex form synapses on the spines of densely spiny medium‐size neurons, whereas terminals originating from neurons in the parafascicular nucleus are in synaptic contact with the dendritic shafts of what appears to be a morphologically distinct type of medium‐size spiny neuron. The integration of the inputs from these two areas probably involves the local axon collaterals of these two types of spiny neuron.
Cell death in the inner and outer nuclear layers of the developing cat retina
Authors: Robinson Stephen R. 
Published: January 2005

AbstractThe occurrence and distribution of pyknotic profiles (dying cells) in the inner (INL) and outer nuclear layers (ONL) were mapped from radial sections through 13 kitten retinae aged from the 30th postconceptional day (30PCD) to the 81PCD (17th postnatal day). Cell death in the INL occurs in two consecutive waves, each beginning at the area centralis and proceeding toward the retinal edge. The first wave involves cells located in the inner part of the INL, adjacent to the inner plexiform layer. It begins on the 50PCD and lasts until the 66PCD, with a peak of 72,000 profiles on the 58PCD. This wave of cell death seems to be associated with the formation of the inner plexiform layer and may be due to the elimination of amacrine cells which have failed to establish sustaining connections with their appropriate target cells. The second wave involves cells located in the outer part of the INL, adjacent to the outer plexiform layer. It begins on the 60PCD and lasts until after the 81PCD, with a peak of 65,000 on the 71PCD. This wave appears to be due to the elimination of ectopic photoreceptor cells displaced by the formation of the OPL and presumably prevented from establishing sustaining connections with their appropriate target cells. A phase of cell death in the ONL begins on about the 42PCD and lasts until after the 81PCD, with a peak of 10,300 pyknotic profiles on the 60PCD. Pyknotic profiles in the ONL were always distributed fairly uniformly across the retina, and did not reflect the centropheripheral maturation of the outer plexiform layer, suggesting that cell death in this layer is not target‐related. The findings of the present study indicate that naturally occurring cell death can be as extensive in populations of intrinsic neurons as it is in populations of extrinsic neurons.
GABA‐like immunoreactivity in the pedal ganglia of Mytilus galloprovincialis: Light and electron microscopic study
Authors: Vitellaro‐Zuccarello L. , De Biasi S. 
Published: January 2005

AbstractThe distribution of gamma‐aminobutyric acid (GABA)‐like immunoreactivity was investigated in the pedal ganglia (PG) of Mytilus galloprovincialis (Mollusca, Bivalvia) with the aid of an antiserum raised against GABA coupled to bovine serum albumin. Examination of whole‐mount preparations and serial vibratome and semithin sections showed the presence of different types of immunoreactive neurons. Small unipolar neurons were the most numerous, and were located mainly in the lateral ganglion cortex. A few bipolar and small multipolar neurons were scattered in the cortex, and, more rarely, in the neuropile. Furthermore, two large symmetrical multipolar neurons, the processes of which extended over large fields in the ipsilateral and contralateral neuropile, were consistently observed in each ganglion.Immunoreactive fibers formed networks in the neuropile and ran parallel in the commissure and in all nerves and connectives.The morphology and distribution of neurons and fibers immunostained by the anti‐GABA serum were similar to these of GAD‐like immunoreactive elements, which indicates that the neurotransmitter and its biosynthetic enzyme are present in the same neurons.Moreover, comparison of serial semithin sections alternatively incubated in postembedding with anti‐GABA and antiserotonin sera revealed that immunoreactivity for these two substances was present in different neuronal populations. However, close association between serotoninlike and GABA‐like immunoreactive elements was observed in a few PG areas.GABA‐like immunoreactivity was demonstrated on ultrathin sections by using secondary antiserum coupled to colloidal gold particles. Labeling was found over somata, fibers, and varicosities containing a distinct type of small (63 nm), pleomorphic, dense‐cored vesicle.