bluuebunny/crossref_metadata_2025_split huggingface dataset:
An ultrastructural analysis of the photoreceptors of the squid and their synaptic connections. II. Intraretinal synapses and plexus
Authors: Cohen Adolph I. 
Published: January 2005

AbstractThe plexus level of the retina of the common squid, Loligo pealei was studied by electron microscopy and was found to be layered in the sclerad direction by imprecise zones respectively characterized by receptor collaterals, synaptic profiles, horizontal fibers, and receptor axons and other neurites ensheathed in glia. Receptor axons characteristically contained microtubules and dense mitochondria, passed vertically through the layer of horizontal fibers and then turned horizontally as they became collectively ensheathed. Receptor collaterals emerged at the level of the most proximal receptor nuclei and at intermittent regions across the retina entered into gap junctions with similar appearing processes. Horizontal fibers may represent efferents which originate in similar fibers sheathed in retinal glia and also seen in the optic nerve and lobe. They occasionally formed en passant synapses on receptors which were characterized by clusters of small clear vesicles and increased membrane density. They also gave rise to branches whose terminals have not been directly traced. Some of these branches showed both clear and dense‐cored vesicles. Synapses on receptors had a cluster of small clear vesicles and one to three large dense‐cored vesicles which were not involved in the cluster. Increased density of the synaptic membrane was best seen after primary osmium fixation. Aldehydeosmium and direct osmium fixed material are presented for comparison. Fibers somewhat similar in appearance to horizontal fibers but which were smaller and more dense had regions filled with smaller dense‐cored vesicles which never showed clustering on a membrane or a consistent relationship with a putative post‐synaptic cell. The possible origins of the neurites of the retinal plexus are discussed.
Retinal structure in the smooth dogfish, Mustelus canis: General description and light microscopy of giant ganglion cells
Authors: Stell William K. , Witkovsky Paul 
Published: January 2005

AbstractGiant ganglion cells (GGC) were demonstrated in retinas of adult dogfish by Golgi impregnation, reduced silver and vital methylene blue staining. All GGC have large, flattened perikarya, and dendrites which radiate in a single horizontal plane of the inner synaptic (plexiform) layer. They are identifiable as ganglion cells by their axons, which after a tortuous initial course enter the nerve fiber layer. We divide the GGC into three varieties: (1) ordinary, with perikarya in the layer of ganglion cells and nerve fibers, and with dendrites radiating in the inner (proximal) one‐fourth of the inner synaptic layer; (2) displaced or Dogiel's cells, with perikarya in the amacrine cell layer and dendrites radiating in the outer (distal) one‐fourth of the inner synaptic layer; and (3) intermediate, with both perikarya and dendritic trees at intermediate levels in the inner synaptic layer.Only the ordinary and displaced GGC in the ventral portion of retinas stained with methylene blue were studied in detail. Cells of both types are arranged in irregular patterns with perikarya about 0.8–1.0 mm apart. Dendrites of the ordinary GGC spread within an elliptical field having a major axis of about 1.7 mm (2.0 mm max) and a minor axis of about 1.5 mm (1.7 mm max). The major axis is vertical in the eye. Dendrites of the displaced GGC spread within a circular field having a diameter of about 1.9–2.0 mm (2.2 mm max). Quantitative comparison of the dendritic trees of ordinary and displaced GGC shows that they differ also in details of dendritic morphology, the dendrites of the ordinary GGC being on the average more numerous and highly branched but shorter than those of the displaced GGC. Ordinary and displaced GGC, therefore, comprise distinct populations which must be presumed to differ functionally.For both ordinary and displaced GGC, the dendritic density and, therefore, the total available postsynaptic surface per unit retinal area decline exponentially with distance from the center to the edge of the dendritic tree. In contrast, the sensitivity to light is constant throughout the receptive field centers of comparable diameter which have been analysed in parallel electrophysiological studies. While the diameters of the largest ganglion cell dendritic fields and receptive field centers are similar, therefore, more detailed correlations of structure and function cannot be made at present.
The organization and projections of the paleostriatal complex in the pigeon (columba livia)
Authors: Karten Harvey J. , Dubbeldam Jacob L. 
Published: January 2005

AbstractThe paleostriatal complex (PC) of the pigeon lies in the basolateral wall of telencephalon, and consists of three major subdivisions: the paleostriatum augmentatum (PA), paleostriatum primitivum (PP), and nucleus intrapeduncularis (INP). The lobus parolfactorius (LPO) lies on the medial aspect of PA and has often been considered to be part of PA. The present study of afferent and efferent connections of the paleostriatal complex supports earlier previous suggestions that the PC is directly comparable to the basal ganglia of mammalia. High concentrations of acetylcholinesterase were found in the PA, LPO and INP. Intense yellowish green fluorescence, probably dopamine, was confined to the PA and LPO.Stereotaxic lesions were placed in either the dorsal ventricular ridge structures above the PC (neo‐ and hyperstriatum), PA, LPO or PP‐INP, and animals sacrificed from one to six days postoperatively. The brains were stained with the Fink‐Heimer methods for the demonstration of degenerating axons and terminals. The region of the neo‐ and hyperstriatum was found to project upon the PA, in a seemingly topographic manner. PA was found to project topographically upon the PP and INP. In contrast, the LPO contributed to the medial forebrain bundle, terminating in the rostral lateral hypothalamus. LPO does not appear to project to the PP or INP.Lesions of PP‐INP resulted in massive degeneration of a descending tract, the ansa lenticularis. Terminal degeneration was found in the anterior and posterior nuclei of the ansa lenticularis of the ventral diencephalon, nucleus dorsalis intermedius posterior and nucleus spiriformis lateralis of the dorsal thalamus, and the nucleus tegmenti pedunculopontinus pars compacta et disseminata of the isthmic tegmentum. In these several features of histochemical and hodological organization the PC alone appears similar to the caudate‐putamen and globus pallidus complex of mammalian brains.More specifically, the PA resembles the caudate‐putamen, whereas PP and INP resemble the external and internal divisions of the globus pallidus, respectively. Similarities and differences between avian and mammalian brains, and the relationship of the present study of the PC and previous studies of the dorsal ventricular ridge structures are discussed (Karten, '69; Nauta and Karten, '70).
The horizontal cells of the rhesus monkey retina
Authors: Boycott B. B. , Kolb H. 
Published: January 2005

AbstractThe large peripheral horizontal cells of the retina of the rhesus monkey are compared with the smaller horizontal cells of the central area. There is most probably only one morphological type of horizontal cell in the rhesus monkey retina. Its dendrites go into cones and it has a single axon. From the fovea to the periphery of the retina there is a gradation in the number of cones an individual horizontal cell contacts. In the fovea a horizontal cell contacts six to nine cones; this ratio increases towards the periphery to between 30 and 40 cones to one horizontal cell.
Proliferation and turnover of glial cells in the forebrain of young adult mice as studied by repeated injections of 3H‐thymidine over a prolonged period of time
Authors: Kraus‐Ruppert R. , Laissue J. , Bürki H. , Odartchenko N. 
Published: January 2005

AbstractThe magnitude of glial cell renewal was studied on young adult mice using repeated intraperitoneal injections of 3H‐thymidine every eight hours over a period of 30 days. Mean labeling indices one hour after the last injection were as follows: Glial cells of the subependymal layer of the lateral ventricle, 61.5%; oligodendrocytes (various sites), 24 to 36.2%; astrocytes (various sites), 14.3 to 30.8%, and satellites in the cerebral cortex, 32.7%. Since DNA synthesis time of the proliferating, immature glial cells is unknown and may be shorter than the time interval of eight hours chosen for repeated injections of 3H‐thymidine, these results are interpreted as representing minimum values for turnover, during 30 days, of the various cell types in different areas of the forebrain. The significance of a marked proliferative activity of the glial cells as related to differentiation and possible migration of subependymal cells, is discussed.
The conformation, cytology and synaptology of the opossum inferior olivary nucleus
Authors: Bowman Michael H. , King James S. 
Published: January 2005

AbstractThis investigation was undertaken to determine the detailed structure and ultrastructure of the inferior olivary nucleus of the opossum (Didelphis marsupialis virginiana). Serial sections of the medulla oblongata were cut in either the frontal, parasagittal or horizontal plane and stained by routine Nissl procedures to determine the cytoarchitecture of the inferior olivary nuclear mass. Because of the apparent lack of distinct principal and accessory olivary subnuclei, a polyethylene plastic scaled reconstruction was made to determine the morphological features of the opossum olivary complex. A descriptive nomenclature was adopted rather than a terminology that would imply analogy with other species.Both light microscopic (Nissl and Golgi) and electron microscopic analyses disclosed a single type of neuron throughout the inferior olivary nucleus. These small to medium (10–30 μ), pleomorphic nerve cells contain a round, eccentric nucleus and a modest amount of cytoplasm. Additional features of olivary somata include diffuse Nissl substance, abundant subsurface cisternae and spines.The moderately branched and entangled dendritic arbor of the olivary neuron bears simple thorns on its proximal, intermediate and distal portions. Multiple spine clusters and unique excrescences termed spine crowned appendages are located on intermediate and distal dendrites.Complex synaptic islands (glomeruli) are found throughout the nucleus and contain a central core of profiles identifiable as spine crowned appendages and small dendrites and/or spines. These core elements are surrounded by numerous boutons which synaptically contact them, and by a small intermediate dendrite. A mantle of astroglial lamellae appears to isolate the glomerulus from the surrounding neuropil.The majority of the synaptic profiles that contact the soma and proximal, intermediate and distal dendrites contain either round vesicles (type 1) or pleomorphic vesicles (type 2). An estimation of the distribution of these terminals indicates that a predominance of type 2 terminals end upon the somata and proximal dendrites, whereas more distal dendritic ramifications receive an approximately equal proportion of the two types of endings. In addition to these endings ( types 1 and 2 ), large efflorescent terminals contact distal dendrites located throughout the nucleus. Furthermore, in different areas of the nuclear realm, small boutons containing only flattened vesicles and fibrous profiles containing pleomorphic vesicles contact intermediate and distal dendrites, respectively.A few large marginal reticular neurons are present around the permiter of the inferior olivary nucleus. These cells send one or more dendrites into the nuclear domain. Such intraolivary dendrites may be synaptically contacted by the same types of terminals that end upon olivary neurons.
Development of left‐right asymmetry in the habenular nuclei of rana temporaria
Authors: Morgan M. J. , O'Donnell J. M. , Oliver R. F. 
Published: January 2005

AbstractAn investigation of the habenular nuclei in tadpoles, young frogs, and fully matured Rana temporaria, revealed several consistent left‐right asymmetries. In tadpoles and young frogs, the left nucleus is partially divided by a vertical septum; lacks cells adjoining the third ventricle along part of its length; and contains fewer free cell bodies in its lumen than the nucleus on the right. In addition, the beginnings of a second nucleus on the left can be seen, lateral to the much larger main left nucleus. The fully grown adult has two distinct left habenular nuclei and only one on the right.
The neuronal organization of the inferior colliculus of the adult cat. II. The pericentral nucleus
Authors: Rockel A. J. , Jones E. G. 
Published: January 2005

AbstractThe intrinsic organization and the connections of the pericentral nucleus of the inferior colliculus have been studied with the Golgi and Nauta techniques. The pericentral nucleus is a thin sheet of densely packed cells extending over the dorsal and posterior surfaces of the inferior colliculus.The pericentral nucleus is composed of spiny and non‐spiny cells. There are large and small spiny neurons, all of which have numerous dendritic spines. The large cells are the most spiny and frequently have spines on their somata. The small spiny cells in most cases have spines on the initial segments of their axons as well as on their somata. The small cell type has a locally ramifying axon and should probably be regarded as an interneuron. The non‐spiny cell‐types are large, and multipolar or fusiform. The dendrites of the multipolar cells extend through the thickness of the pericentral nucleus and the parent cell probably gives rise to the efferents of the nucleus.Although the pericentral nucleus has previously been described as having a layered “cortical” structure, there is little evidence to justify this, since no clearly defined axonal or cellular layers are present. The pericentral nucleus receives a heavy descending projection of fibers from the auditory cortex, and an ascending projection from the upper brainstem (probably only from the dorsal nucleus of the lateral lemniscus). The ascending system of fibers may also contribute branches to the central nucleus of the inferior colliculus. The ascending and descending afferents run parallel to the surface of the pericentral nucleus but at right‐angles to each other, thus forming a rectangular grid. The possible functional significance of this grid‐like arrangement is discussed.No evidence was found for a projection from the central nucleus to the pericentral nucleus, but axons were seen to pass in the opposite direction, from the pericentral nucleus to the central nucleus, running parallel to the cellular laminae in the latter nucleus.
A three dimensional study of layer I of the rat parietal cortex
Authors: Vaughan Deborah W. , Peters Alan 
Published: January 2005

AbstractSerial thin sections have been used to reconstruct neuronal processes in the outer portions of layer I of adult rat somatosensory cortex. The reconstructions show that two distinct forms of dendrites exist in this area: one that is smooth and varicose and another that bears spines along a shaft of relatively constant diameter. These two dendritic types, which originate from nonpyramidal and pyramidal neurons respectively, have differences in the distribution of organelles. Cortical dendrites terminate with no apparent morphological modification which would permit their identification in isolated thin sections. A pyramidal dendritic ending is blunt, about 0.5 μ in diameter, with microtubules and smooth endoplasmic reticulum in the terminal cytoplasm. Very long mitochondria which are invariably present within pyramidal dendrites, penetrate into an ending. A smooth dendrite terminates in an expansion containing microtubules and smooth endoplasmic reticulum, but no long mitochondrion. One or two asymmetrical synapses occur at the end of each terminating dendrite but do not encompass the tip. The principal axonal elements in layer I are small unmyelinated axons with en passant boutons. Serial examination reveals that various combinations of synaptic contacts are possible between axons and dendrites of both types.
Cerebellopontine projections in the american opossum. A study of their origin, distribution and overlap with fibers from the cerebral cortex
Authors: Yuen Hugo , Dom Richard M. , Martin George F. 
Published: January 2005

AbstractThe origin, course and distribution of cerebellopontine fibers was studied in the opossum by employing the Nauta‐Gygax and Fink‐Heimer techniques. Our results substantiate and extnd those of Brodal, Destombes, Lacerda and Angaut ('72) concerning the existence of cerebellopontine projections and provide evidence for a hitherto unreported fastigial projection to the basilar pons. Destruction of the caudal, medial division of the fastigial nucleus elicits bilateral degeneration in a restricted area of the medial pontine nucleus. This small terminal field is located in the angle between the medial lemniscus and the pyramidal tract and is found throughout the caudal three‐fifths of the pons. The degenerating fibers do not course within the descending brachium conjunctivum, but reach the pons by filtering through the reticular formation from the uncinate fasciculus. Lesions that involve either the interpositus anterior or the dentate nucleus produce degeneration within the contralateral descending brachium conjunctivum and basilar pons. Terminal fields are located within the median, medial (paramedian nucleus of cat), peduncular, ventral and lateral nuclei. The heaviest degeneration is in the medial nucleus.Although cerebellar and cortical projections have different targets in the basilar pons, there is some overlap. Fastigial and preorbital fibers have partial overlap in the dorsal part of the medial nucleus, whereas the peduncular and lateral nuclei are the areas of overlap between the interpositus anterior and dentate projections with those from forelimb (and probably face) cortical areas. This overlap is particularly obvious in the caudal part of the lateral nucleus and occurs between fibers from limb motor‐sensory cortex and those arising mainly within the anterior interpositus nucleus. There is no pontine overlap between cerebellar and visual or auditory cortical projections.
Morphological organization of monoamine‐containing neurons in the hypothalamus of the painted turtle (Chrysemys picta)
Authors: Parent A. , Poitras D. 
Published: January 2005

AbstractThe distribution and morphological aspect of monoamine‐containing neurons in the hypothalamus of the turtle (Chrysemys picta) were studied by means of light and fluorescence (Falck‐Hillarp method) microscopy. In this reptilian brain, numerous neurons of the catecholamine type are unevenly distributed within the hypothalamic periventricular gray. They are present in large number along the ependymal wall of the sulcus intrahypothalamicus (paraventricular organ) and of the infundibular recess, but are less numerous along the preoptic recess. Most of these neurons appear as small bipolar cells with a short club‐like ventricular process contacting the cerebrospinal fluid of the third ventricle, and a more tenuous varicose process either penetrating the underlying hypothalamic tissue or reaching the external layer of the median eminence. Thin “collaterals” may be seen to arise from a few intraventricular processes of neurons of the paraventricular organ in material prepared by the Golgi‐Cox method. Another small group (10 to 15 perikarya) of larger catecholamine‐containing neurons apparently without any ventricular process are also present in the basomedial area of the caudal hypothalamus. In the present study no intrinsic neurons of the serotonin (5‐hydroxytryptamine) type were found within the hypothalamus of (Chrysemys picta). However, numerous fine nerve terminals and varicose fibers of the serotonin type, most probably of extrahypothalamic origin, were observed along the chiasmatic ridge and within the lateral hypothalamus, respectively.
Fiber composition of the posterior lateral‐line nerve of goldfish, investigated by electrophysiological and microscopical techniques
Authors: Fukuda Jun 
Published: January 2005

AbstractThe trunk of the posterior lateral‐line nerve of goldfish was stimulated electrically, and the evoked compound spike potential was recorded from the proximal cut end of the nerve. The spike potential consisted of four components which were distinguished from each other by differences of excitability, refractory period and conduction velocity. They were named F‐1, F‐2, F‐3 and S, in the order of decreasing conduction velocity. All of these components could generally be elicited by stimulation of the small nerve branches innervating canal organs.By means of light‐ and electron‐microscopical examination, the fiber diameter spectrum of the posterior lateral‐line nerve was obtained. The observed compound spike potentials were reconstructed successfully from this fiber spectrum. It is concluded that the three subgroups, F‐1, F‐2 and F‐3 components are thick myelinated fibers and the S component is thin myelinated fibers.
Measurement of nerve fiber diameters in the region of the dorsal spinocerebellar and spinocervical tracts in the cat
Authors: Loewy Arthur D. 
Published: January 2005

AbstractNerve fibers in the region of the dorsal spinocerebellar tract (DSCT) and the spinocervical tract (SCT) in the adult cat were measured at various spinal levels. Fiber measurements were made from photographs of transverse sections of Epon embedded material that had been fixed by vascular perfusion with a paraformaldehyde solution, post‐fixed in osmium tetroxide, and stained with Azur II‐methylene blue.The fiber diameter histograms from the region of the DSCT exhibited a bimodal distribution and between 50 to 75% of the fibers had a diameter of less than 5 μ. The presence of a subpopulation of large sized nerve fibers was identified between the 10 to 15 μ diameter intervals and this subpopulation appeared to decrease in size at the rostral spinal segments. This observation agrees with the electrophysiological studies of Lundberg and Oscarsson ('60) who found that the conduction velocity of the DSCT decreases at rostral levels.The fiber diameter measurements from the region of the SCT appeared to exhibit a unimodal distribution and between 40 to 75% of the fibers in this region had a diameter of less than 5 μ. By omission of fibers less than 5 μ, it could be shown that the mean values of the SCT decreased at successively rostral spinal levels. However, when the cumulative frequency distributions of the SCT data from different spinal levels were compared, a definite trend of statistically significant differences at the 0.05 level could not be established.The average fiber density (number of fibers/mm2) of the DSCT was 16,617 and the average fiber density of the SCT was 15,927.The heterogeneous organization of the dorsolateral fasciculus is discussed.