bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphology of primary axosomatic endings in the anteroventral cochlear nucleus of the cat: A study of the endbulbs of Held
Authors: Ryugo D. K. , Fekete D. M. 
Published: December 2004

AbstractThe central axons of Type I spiral ganglion neurons travel in the auditory nerve and terminate in the cochlear nucleus. The ascending branches of these axons innervate the anteroventral cochlear nucleus and give rise to large axosomatic endings, called the endbulbs of Held, and smaller boutons. This paper reports a study of the endbulbs of Held, stained by horseradish peroxidase and variants of the Golgi method in kittens 2, 5, 10, 20, and 45 days postnatal and adult cats. Endbulbs tend to fall into two extreme groups with some endbulbs having an intermediate appearance; consequently, we have defined three descriptive stages of endbulbs that are conceived of as representing a developmental sequence. One group of endbulbs is found mostly in kittens younger than 10 days postnatal and is similar to the classic description of endbulbs by Ramón y Cajal ('09). The other extreme group of endbulbs is found mostly in adult cats. In these cases, the parent axonal trunk divides into several thick, gnarled branches that in turn branch again, sometimes repeatedly. These branches display irregular varicosities and form a cup‐shaped arborization into which the postsynaptic cell body nestles. A chronology of postnatal endbulb development has been inferred from the relative proportions of the different endbulb stages at various ages. Maturation transforms the endbulb of Held from a large, spoon‐shaped swelling having many filipodia into an elaborate tree with broad trunks and many smaller branches. Some implications of the proposed developmental sequence are discussed.
Spontaneous regeneration of cut axons in adult rat brain
Authors: Foerster Anne P. 
Published: December 2004

AbstractLesions with precisely defined boundaries were made, in adult rat brains, with a new type of cutting device that remained implanted during various survival times. The subsequent events were followed histologically in silverstained (including Fink‐Heimer) horizontal sections, with myelin and nuclear counterstains. The devices, inserted vertically through the dorsal surface of the brain until they met the floor of the skull, consisted of a horizontal cutting wire (0.9–2.6 mm long) between two vertical support wires, all 90 μm diameter. Following fixation of the brain, the device was removed from its ventral surface; thus, the channels left by the support wires appeared as two holes in horizontal sections, clearly marking the limits of the cut. The extents of the tissue cut by, and that passively deflected around, such devices were charctrized from measurments of brains examined immediately after an incision was made and from degeneration studies after 3‐day implantations. After implantations of 18–230 days, the severed axons no longer abutted the line of such lesions, as seen initially; now axons were often observed to extend alongside the lesion, then to bend and course around the support wire. Such “detours” curved back into the injured tracts, seeming to reconnect them appropriately. Detours had begun by 3–8 days, and end‐swellings were frequently seen on their reoriented axons. Neither collateral sprouting of spared axons nor passive deformation of brain tissue was consistent with the findings. It is concluded that a massive and reconstructive regeneration of cut axons occurred around the ends of lesions made by the cutting devices.
Immunocytoehemical localization of substance P in the spinal trigeminal nucleus of the rat: A light and electron microscopic study
Authors: Priestley John V. , Somogyi Péter , Cuello A. Claudio 
Published: December 2004

AbstractThe neuropeptide substance P is a transmitter candidate for certain primary afferent fibers which terminate in the substantia gelatinosa. In this study the light and electron microscopic localization of substance P in the substantia gelatinosa of the spinal trigeminal nucleus of the rat has been studied using immunocytochemical procedures.Substance P immunoreactive fibers were observed mainly in lamina I and outer lamina II. Ultrastructural analysis revealed immunoreactivity in unmyelinated fibers and in axon terminals which contained agranular spherical vesicles and large dense‐cored vesicles and which made predominantly simple asymmetric axodendritic synaptic contacts. Immunoreactive terminals only rarely formed the central terminal of synaptic glomeruli and in only one example was a stained terminal possibly postsynaptic to an unstained terminal. The majority of synapses were onto small dendrites in outer lamina II and in some cases these dendrites were themselves presynaptic to other dendrites. Immunoreactive terminals also synapsed with the soma and proximal dendrites of large neurons on the border of laminae I and II.The results show that there are at least two distinct targets for substance P immunoreactive terminals in the substantia gelatinosa, namely the large lamina I neurons and lamina II probable intemeurons. Some of the former may be projection neurons while some of the latter may correspond to the inhibitory islet cells described by Gobel and colleagues in the cat. In addition the results indicate that few substance P immunoreactive terminals receive axoaxonic synapses and emphasize instead the role of postsynaptic interactions. In particular the results suggest several sites at which substance P might interact postsynaptically with the neuropeptide enkephalin.
A comparative histological and electrophysiological study of some neurotoxins in the rat hippocampus
Authors: Lancaster Barrie , Wheal Howard V. 
Published: December 2004

AbstractIt has been proposed that the neurotoxic action of kainic acid is a result of the seizure activity which it induces. In this study intraventricular injection of kainic acid, and three other putative neurotoxins, was used in an attempt to investigate the role of electrical seizure activity and neurotoxicity in the rat hippocampus, Two separate groups of experiments were performed. First, & histological study of the neurotoxic potency of the compounds under investigation was carried out, and second, an electrophysiological study of those compounds which displayed neurotoxicity. In these experiments, extracellular recordings were made in the hippocampus ipsilateral to infusion during and after administration of the neurotoxin.Kainic acid (5.0 μg) produced unilateral lesions of the CAB and C A4/ hilus cells of the hippocampus, but CA1 and granule cells remained intact. Electrical seizure activity could be recorded from both CS3 and CA1 regions after kainic acid infusion. Dihydrokainic acid displayed no neurotoxicity. α‐ketokainic acid (5.0 μg) only produced minor toxic effects such as small areas of pyknosis, but electrical seizure activity was produced in both CA3 and CA1 cell regions. Cis 1‐amino 1,3‐dicarboxycyclopentane (cis‐ADCP), (5.0 μg) produced unilateral lesions of the CA3 area without any extension into the CA4/hilus cell layer. There was no electrical seizure activity associated with the action of this compound.These results show that the presence of seizure activity in the hippocampus is not invariably followed by loss of pyramidal cells. As cis‐ADCP produces a discrete lesion in the absence of any seizure activity, this compound may prove to be a more useful neurotoxin for producing experimental models of disease states in the central nervous system.
Peripheral organization and central projections of the electrosensory nerves in gymnotiform fish
Authors: Carr Catherine E. , Maler Leonard , Sas Emilia 
Published: December 2004

AbstractThe electrosensory system of weakly electric gymnotiform fish is described from the receptor distribution on the body surface to the termination of the primary afferentsin the posterior lateral line lobe (PLLL). There are two types of electroreceptor(ampullary and tuberous) and a single type of lateral line mechanoreceptor (neuromast). Receptor counts in Apteronotus albifronsshow that (1) neuromasts are distributed as in other teleosts; (2) ampullary receptors number 151 on one side of the head and 208 on one side of the body; (3) tuberous receptors were estimated to number 3,000‐3,500 on one side of the head and 3,500‐5,000 on one side of the body. The distribution of each receptor type is described.Each receptor is innervated by a single primary afferent. Electro‐sensory afferents have myelinated cell bodies in the ganglion of the anterior lateral line nerve (ALLN). The distribution of these ganglion cell diameters is strongly bimodal in Apteronotus and Eigenmannia: The smaller‐diameter cells may be those which innervate ampullary electroreceptors, the larger‐diameter tuberous electroreceptors.Transganglionic HRP transport techniques were used to determine the first‐order connections of the anterior lateral line nerve in six species of gymnotiform fish. Small branches of the ALLN were labeled so as to determine the somatotopic organization in the PLLL. The PLLL is divided into four segments from medial to lateral, termed medial, centromedial, centrolateral, and lateral segments (Heiligenberg and Dye, '81). Representations of the head are found rostrally in each zone, and the trunk is mapped caudally in each zone. Thus there are four body maps in the PLLL. The medial segment receives ampullary input (Heiligenberg and Dye, '82) and maps the dorsoventral body axis mediolaterally, as does the tuberous centrolateral segment. The tuberous centromedial and lateral segments map the dorsoventral axis lateromedially. Thus the medial and centromedial segments meet belly to belly, the centromedial and centrolateral segments meet back to back, and the centrolateral and lateral segments meet belly to belly. Adjacent electrosensory maps within the PLLL are therefore always mirror images.
Representations of the body surface in cortical areas 3b and 1 of squirrel monkeys: Comparisons with other primates
Authors: Sur Mriganka , Nelson R. J. , Kaas J. H. 
Published: December 2004

AbstractMicroelectrode multiunit mapping techniques were used to determine the somatotopic organization of postceritral parietal cortex in the squirrel monkey Saimiri sciurus. Recordings were largely confined to architectonic areas 3b and 1. Results were compared to those from similar studies of owl (Merzenich et al., '78) and macaque (Nelson et al., '80) monkeys. As in these previous investigations, separate representations of the body surface were found in areas 3b and 1 of squirrel monkeys. These representations were organized in parallel, so that both proceeded from the tail on the medial wall of the cerebral hemisphere, to the lips and oral cavity on the lateral margin of these areas along the sylvian fissure. The representations were also roughly mirror images of each other so that whatever skin surface was represented rostrally in area 3b was represented caudally in area 1, and similar skin surfaces were represented along the common border. However, the representations were not identical. For example, the split representations of the leg differed so that the distal leg was represented in cortex lateral to that devoted to the foot in area 1 and medial to the foot in area 3b. Remarkably, the representations of some body parts were reversed in orientation in both area 3b and area 1 in squirrel monkeys as compared to owl and macaque monkeys. The face, arm, trunk, and leg representations were all reversed in squirrel monkeys, while the orientations of the hand and foot representations were the same. For example, the dorsal trunk is represented rostrally in area 3b and caudally in area 1 and the ventral trunk is represented at the 3b/l border in owl and macaque monkeys, while the ventral trunk is represented rostrally in area 3b and caudally in area 1 and the dorsal trunk is represented at the 3b/1 border in squirrel monkeys. These reversals of somatotopic organization in part but not all of the representations in areas 3b and 1 suggest that both fields are divided into sectors where the basic somatotopic orientation is independently determined, that the orientation of some of these sectors is subject to reversal in evolution, and that matching sectors in areas 3b and 1 are not independent in somatotopic organization.
The origin of lipid phagocytes in the central nervous system: I. The intrinsic microglia
Authors: Brierley J. B. , Brown A. W. 
Published: December 2004

AbstractThe potential for the transformation of the normal microglial cell to a lipid phagocyte was studied by light and electron microscopy in the brains of rodents and by light microscopy only in primates. All were subjected to some form of hypoxia‐ischemia and the microglial response was examined in regions of selective neuronal destruction (SND) so that infarction was deliberately excluded. In vivo perfusion‐fixation was employed in all animals and light microscopic examination was carried out on paraffin‐ and sometimes celloidin‐embedded material. Semithin plastic sections from several regions of the rodent brains were used for light microscopy but ultrastructural studies were confined to the hippocampus.In all animals the microglia were activated and transformed into rod cells exhibiting phagocytic properties but only a minority gave rise to lipid phagocytes. Blood vessels were normal in all animals and no hematogenous elements were identified in the parenchyma. As neuronal ghosts could be identified for up to 3 weeks it was concluded that the capacity of the microglia for phagocytic activity was limited.
Volume densities and specific surfaces of neuronal and glial tissue elements in the rat supraoptic nucleus
Authors: Pilgrim Ch. , Reisert I. , Grab D. 
Published: December 2004

AbstractThe present study was undertaken to provide an explanation for previous autoradiographic results suggesting a several times higher rate of synthesis of glycoconjugates per unit volume of hypothalamic glia than of neurons. Volume densities, specific surfaces (surface:volume ratios), and relative surfaces (contribution of the surface of a tissue element to the total surface of the tissue) were assessed.Neuronal elements occupy about 74% and glial elements about 8% of the total volume. The specific surface, i.e., the amount of plasma membrane per unit volume of structure, is more than 30 times higher in the neuropil than in the neuronal perikaryal fraction. The largest specific surface is found with (unmyelinated) axons and astroglial processes. The specific surface of the average astrocyte is about twice that of the average neuron. If the surface of the entire cell is considered in relation to the perikaryal volume only, this ratio is about seven times as large for glial cells as for neurons. It follows that an astrocyte perikaryon has to renew a several times larger plasma membrane than a neuron, which can account for the above differences in perikaryal synthesis rates of glycoconjugates.
Insula of the old world monkey. Architectonics in the insulo‐orbito‐temporal component of the paralimbic brain
Authors: Mesulam M.‐Marsel , Mufson Elliott J. 
Published: December 2004

AbstractThe insula of the rhesus monkey has a surface area of approximately 160 mm2 and can be divided into three architectonic sectors. The agranular sector is coextensive with prepiriform allocortex and is characterized by three agranular cellular strata, a zonal layer of myelinated fibers, and a high level of intracortical acetylcholinesterase (AChE). The dysgranular sector adjoins the agranular sector and shows first the emergence of a granular L4 and then a gradual differentiation of L2. Cortical myelin is low and mostly within deep layers; the AChE level is less than in the agranular sector. The third and granular sector covers the posterior aspect of the insula and contains granular L4 and L2, incipient sublamination of L3, increased cortical myelin with an emergent outer line of Baillarger, and a very low density of AChE. These observations indicate that AChE histochemistry can be used for the architectonic analysis of cortex.The lateral orbital cortex and the temporal pole can also be subdivided into agranular, dysgranular, and granular regions. In the insula as well as in lateral orbital and temporopolar areas, the agranular sector is directly contiguous with prepiriform cortex. When these three brain regions are considered jointly, they are seen to be organized in the form of increasingly more differentiated agranular, dysgranular, granular, and hypergranular sectors arranged concentrically around prepiriform allocortex.The term paralimbic is suggested as a generic term for all regions where such transitions occur from allocortex to granular isocortex. The insula, lateral orbital surface, and temporal pole are paralimbic areas with an olfactory allocortical focus. The parahippocampal, retrosplenial, cingulate, and subcallosal regions constitute a second group of paralimbic areas with a hippocampal‐induseal focus. In the most general sense, the functional specializations of paralimbic areas are predominantly for behaviors which require an integration between extrapersonal stimuli and the internal milieu.The human insula has a plan of organization virtually identical to that in the rhesus monkey. In the human, the insulo‐orbito‐temporopolar component of the paralimbic brain may become involved in conditions which range from epilepsy to psychosomatic disease.
The motor cortex of the rat: Cytoarchitecture and microstimulation mapping
Authors: Donoghue John P. , Wise Steven P. 
Published: December 2004

AbstractThe first motor (MI) cortex of the rat was identified as the region from which movements could be evoked by the lowest intensity of electrical stimulation. The location of this region was correlated with Cytoarchitecture in the frontal and parietal cortex. Two frontal areas can be discerned in Nissl‐stained sections: (1) the medial agranular field, marked by a pale‐staining layer III and a compact layer II, and (2) the lateral agranular field, which has more homogeneous superficial layers and a broad layer V containing large, densely staining cells. Both of these regions project to the spinal cord and can therefore be included in the somatic sensorimotor cortex. MI in the rat coincides with the lateral agranular field but also overlaps with part of the adjacent granular cortex of the first somatic sensory (SI) representation. We conclude that the rat MI cortex can be identified by microstimulation techniques and by cytoarchitecture in the rat.
The distribution of vasotocin and isotocin in the brain of the rainbow trout
Authors: van den Dungen H. M. , Buijs R. M. , Pool C. W. , Terlou M. 
Published: December 2004

AbstractThe distribution of vasotocin and isotocin in the brain of the rainbow trout Salmo gairdneri was investigated by the unlabeled antibody enzyme method, by using purified antisera against arginine vasotocin and isotocin. In the preoptic nucleus no clear differences were observed in the distribution of vasotocinand isotocin containing cells. Vasotocin and isotocin innervation was found in most brain regions, though in general isotocin fibers were much more abundant. The area dorsalis pars medialis of the telencephalon, the saccus dorsalis, and the basal part of the nucleus recessus posterioris were found to be innervated by vasotocin and scarcely by isotocin fibers. In the nucleus habenularis, the nucleus recessus lobus lateralis, the nucleus preglomerulosus pars medialis, and the tectum mesencephali isotocin fibers prevailed. These findings in the trout brain are compared with the vasopressin and oxytocin innervation of the rat brain.
Retinal degeneration in the pcd cerebellar mutant mouse. II. Electron microscopic analysis
Authors: Blanks Janet C. , Mullen Richard J. , Lavail Matthew M. 
Published: December 2004

AbstractThe cerebellar ataxia in Purkinje cell degeneration pcd mutant mice results from the rapid loss of Purkinje cells between 3 and 5 weeks after birth. The loss of photoreceptors in these mutants begins about the same time but proceeds slowly, with most photoreceptors being lost by 1 year of age. In this study the retinas of pcd/pcd mice and their littermate controls from the age of 10 postnatal days to 15 months were analyzed by electron microscopy. The first signs of photoreceptor cell degeneration are apparent in the region of photoreceptor inner segments as early as postnatal day 13, and more prominently at day 18. During this time, the degeneration is characterized by a large number of vesicles, ranging in diameter from 150 to 350 nm, which are located in the extracellular space adjacent to the photoreceptor inner segments. Analysis of serial sections shows that most of these membrane‐bound degeneration profiles are tubular in shape and some are continuous with the cell membrane of the inner segment. There‐lore, these [profiles] are thought to arise from tubular outpocketings of the inner segments which cleave off to form isolated membrane‐bound profiles. This represents a new and unusual form of photoreceptor degeneration. While the most obvious abnormality in the retina is degeneration of photoreceptor cells, Müller cells also appear to be affected, with swollen apical processes often seen coursing through the outer nuclear layer.
Cytoarchitecture, neuronal morphology, and some efferent connections of the interstitial nucleus of cajal (INC) in the cat
Authors: Zuk A. , Gwyn D. G. , Rutherford J. G. 
Published: December 2004

AbstractThis study describes the Cytoarchitecture and neuronal morphology of the interstitial nucleus of Cajal (INC) in the cat. In addition, the efferent projections of this nucleus to the spinal cord and inferior olive were studied by retrograde labelling with horseradish peroxidase (HRP).The INC was shown to extend rostrocaudally for slightly more than 2 mm. Caudally, the nucleus consists of a small number of loosely aggregated neurons lying lateral to the ventral periaqueductal gray matter at a rostrocaudal level corresponding to the rostral one‐fifth of the somatic cell columns of the oculomotor nucleus. Rostrally, the INC increases in size and reaches its maximum development in its rostral half, where it lies ventro‐lateral to the nucleus of Darkschewitsch (ND). Rostrally the INC is bounded by the dorsoventrally aligned fibres of the fasciculus retroflexus.Two groups of neurons could be distinguished within the INC in both normal and HRP‐injected material. One group consists of a relatively small number of large, oval, pyramidal, fusiform, or multipolar neurons with mean dimensions of 40 × 26 μm The second group consists of numerous small to medium‐sized neurons with mean dimensions of 20 × 14 μm. Large neurons and some cells of the second group contain substantial amounts of Nissl substance throughout their perikarya. Some medium‐sized to small neurons exhibit indentations in their nuclei, and glial cells are often apposed to their cell membranes. Golgi‐Kop sch preparations taken from kitten showed that INC neurons possess sparsely branched, radiating dendritic trees with few spinous processes. The majority of INC neurons retrogradely labelled with HRP exhibited similar dendritic patterns.Injections of HRP into lesions at cervical, thoracic, or lumbar levels of the spinal cord resulted in retrograde labelling of neurons of all sizes and shapes throughout the entire length of the INC. However, the greatest number of HRP‐labelled cells in INC were observed subsequent to injections of the enzyme into cervical levels of the cord. Following injections of HRP into the inferior olive only small to medium‐sized neurons were labelled in the nucleus, the majority of which are located in rostral levels of the INC. A substantial olivary projection was observed to originate in the nucleus of Darkschewitsch (ND) and the nucleus parafascicularis (NPF). The sizes of the projections from these two nuclei to the inferior olive appeared to be much larger than that from the INC. Smaller numbers of neurons were also observed in the rostral parvocellular red nucleus (RN) and mesencephalic reticular formation (MRF).