bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neurotropic influence of mesenchymal limb target tissue on spinal cord neurite growth in vitro
Authors: Pollack Emanuel D. , Muhlach William L. , Liebig Veronica 
Published: January 2005

AbstractPeripheral nerve fiber outgrowth from developing spinal cord is proposed to be under the influence of the limb bud target which, at the time of nerve fiber invasion, is in an essentially premuscular, mesenchymal condition. Thus, the true target for elongating spinal nerve fibers in early development is mesenchyme rather than differentiated skeletal muscle. Spinal cord explants derived from stage V larval Rana pipiens were cultured in a defined medium in the presence or absence of mesenchymal limb tissue or limbconditioned medium (LCM). Analysis of quantified neuritic outgrowth under these conditions demonstrated a dependency on the target tissue for enhanced nerve fiber density and oriented growth. The characteristics of neuritic growth in the presence of limb mesenchyme or LCM changed from the relatively sparse and straight outgrowth of control cords to dense, wavy arborizations. Areas of the cord explants nearest the limb tissue exhibited the greatest increases in nerve fiber density and morphologic complexity. Additionally, an inverse relationship existed between growth enhancement and the cord‐to‐target distance. Regulation of directed nerve growth in vitro is suggested to result from a diffusible, target‐originated growth factor that binds to the attachment substratum as a concentration gradient guidance pathway with implications for mechanisms of in vivo nerve growth.
Development of the pyramidal tract in the hamster. II. An electron microscopic study
Authors: Reh Thomas , Kalil Katherine 
Published: January 2005

AbstractWe undertook a qualitative and quantitative electron microscopic study of the growth and development of the pyramidal tract in the hamster to investigate the mode of growth of the axons, the possibility of fiber degeneration during development, and the process of myelination. By calculating the total fiber number as the product of axon density and tract area for several postnatal ages, we found that the pyramidal tract grows through the medulla as a compact bundle containing nearly twice the number of fibers as the mature tract. During the second postnatal week there is a substantial loss of axons followed in the third and fourth weeks by a more gradual loss such that by 34 days after birth the total number of axons reaches the adult value.Myelination in the hamster pyramidal tract begins at 7 days and continues at a very slow rate until the third postnatal week, when a dramatic increase in myelin formation occurs. By 34 days after birth the number of myelinated axons is approximately 80% that of the adult. As has been reported for other CNS tracts, there does not seem to be a “critical diameter” of an axon that absolutely determines the presence or absence of myelin on a fiber. However, all axons above 0.5 μm in diameter are myelinated at approximately the same rate, while those under this diameter are myelinated much more slowly and even in the adult make up only a small percentage of the total myelinated fibers.
Neurotensin immunoreactivity in the superficial laminae of the dorsal horn of the rat: I. Light microscopic studies of cell bodies and proximal dendrites
Authors: Seybold Virginia S. , Elde Robert P. 
Published: January 2005

AbstractAlthough neurotensin perikarya have been identified in the superficial laminae of the dorsal horn, little is known regarding the cytoarchitecture of these neurotensin‐containing neurons. Immunohistochemical staining of 75‐μm sections in several planes through colchicine‐treated rat spinal cords revealed morphologic features of neurotensinlike immunoreactive (NLI) perikarya and proximal dendrites.Populations of NLI neurons were identified in the outer one‐third of lamina II, the inner one‐third of lamina II, and outer lamina III. The NLI neurons in lamina II had elongated perikarya and the dendrites emerged from the rostral and caudal poles of the cell body. The proximal dendrites of NLI cells in inner laminae II were shorter and contained more spines than outer lamina II NLI cells. The NLI cells in outer lamina III did not exhibit polarity and the proximal dendrites were generally shorter than those of NLI cells in lamina II. The lamina II cells appear similar to islet cells (Gobel, 1975), while the lamina III cells have many of the characteristics of the II/III border cell described by Gobel (1978). Interestingly, the inner lamina II NLI cells occurred in clusters with NLI cells in outer lamina III. The periodicity of these clusters suggests a neurochemical dimension for the organization of the superficial laminae of the dorsal horn.
Brain neurons which project to the spinal cord in young larvae of the zebrafish
Authors: Kimmel Charles B. , Powell Susan L. , Metcalfe Walter K. 
Published: January 2005

AbstractA small number of brain neurons project to caudal levels of the spinal cord in the larva of the teleost Brachydanio rerio. These cells were identified in animals 6 days after fertilization by backfilling with horseradish peroxidase following transection of the cord at the level of the cloaca. In preparations with the most labeled cells a total of 30–40 were present on each side of the midline. They were located within three regions of the brainstem: the midbrain nucleus of origin of the medial longitudinal fascicle (mlf), the hindbrain reticular formation, and the hindbrain vestibular nucleus. A total of 15 classes of cells could be distinguished by soma positions, dendritic fields, and axonal pathways. For some of these classes only one or two cells were usually present on each side of the brain. Most of the labeled cells contributed axons to the mlf ipsilateral to the soma; however, the Mauthner cells and three new types of hindbrain reticulospinal cells have decussating axons that enter the contralateral mlf.The observed distribution of labeled reticulospinal cells is similar to that previously described for large reticular cells in adult teleosts and to the system of identified Mauthner and Müller cells in the lamprey.
Lesion‐induced synaptogenesis in the dentate gyrus of aged rats: II. Demonstration of an impaired degeneration clearing response
Authors: Hoff Steven F. , Scheff Stephen W. , Cotman Carl W. 
Published: January 2005

AbstractPreviously we reported that a delayed onset in the reinnervation of the outer two‐thirds of the dentate molecular layer occurred in aged rats after an entorhinal lesion. Several factors associated with formation of new synaptic contacts and removal of degenerative debris may affect the reinnervation process. In this study the appearance and removal of degeneration was analyzed and evaluated with respect to the delayed reinnervation process in aged rats. After a complete lesion of the entorhinal cortex, 85–90% of the input to the outer two‐thirds of the ipsilateral molecular layer is lost. Electron‐dense and electron‐lucent degeneration are present throughout the outer two‐thirds of the denervated molecular layer. In both aged and young adult rats, the electron‐lucent degeneration disappears by 10 days postlesion. The predominant electron dense degeneration, however, is removed at a different rate by young adult and aged rats. Young adults demonstrate a biphasic degeneration removal process, with almost half of this degeneration rapidly lost by 10 days postlesion, and nearly all by 60 days post‐lesion. Aged animals in contrast, have lost only 16% of the dense degeneration at 10 days postlesion, with about 30% of the degeneration remaining at 60 days postlesion. The impaired removal of the degeneration from the denervated zone appears to be reciprocally related to the reinnervation response in both age groups and may be related to the normal astrocyte hypertrophy and elevated corticosteroid levels in aged rats.
The ultrastructure of identified locust motor neurones and their synaptic relationships
Authors: Watson A. H. D. , Burrows M. 
Published: January 2005

AbstractMotor neurones in the thoracic ganglia of the locust were impaled with microelectrodes and identified according to the muscle they innervated and their other physiological properties. They were then labeled by intracellular injection of horseradish peroxidase and processed for electron microscopy. The nature and distribution of synapses on each motor neurone was examined and, by the use of reconstructions from serial sections, their spatial relationships revealed. The metathoracic fast extensor tibiae and mesothoracic tergosternal flight motor neurones have both output and input synapses on their neuropilar branches. These synapses are involved in serial, reciprocal, and recurrent relationships showing that the structural equivalent of a physiological synapse may be complex. The metathoracic slow extensor tibiae and anterior fast flexor tibiae motor neurones apparently have only input synapses within the neuropile.
Amygdalopetal projections in the cat. I. Cortical afferent connections. A study with retrograde and anterograde tracing techniques
Authors: Russchen Fokje T. 
Published: January 2005

AbstractThe cortical afferent connections of the amygdaloid complex of the cat have been studied by means of retrograde tracing of horseradish peroxidase and the fluorescent substances bisbenzimid and nuclear yellow. Subsequently, anterograde tracing experiments were carried out in order to define more precisely the termination areas of the corticoamygdaloid fibers.The results of the present study indicate that the main and accessory olfactory bulbs, the anterior olfactory nucleus, the prepiriform cortex and discrete regions of the medial frontal lobe, the insular and temporal cortices, as well as the perirhinal and entorhinal cortices and the ventral subiculum project to the amygdaloid complex. The main termination sites of these projections are the central, basolateral, and lateral amygdaloid nuclei. Neocortical regions project to the lateral nucleus and the lateral division of the lateral central nucleus. The mesocortical regions project predominantly to the basolateral nucleus and a medial division of the lateral central nucleus. In addition, area 35 distributes fibers to the lateral nucleus and the entorhinal cortex projects to the cortical nuclei of the amygdaloid complex. Fibers from the infralimbic area only reach the region of the medial central nucleus. Of the allocortical regions the prepiriform cortex distributes its fibers to the lateral, basolateral, and cortical nuclei, whereas the ventral subiculum projects to the medial division of the lateral central nucleus and the cortical nuclei.In the neocortical and most of the mesocortical regions the cells which project to the lateral and basolateral amygdaloid nuclei lie in layer III, whereas the cells which project to the central nucleus are located in layer V.
Retinotopic and temporal organization of the optic nerve and tracts in the adult goldfish
Authors: Bunt Stuart M. 
Published: January 2005

AbstractIn order to investigate the role of the different factors controlling the pathways and termination sites of growing axons, selected optic fibers were traced from the eye to the tectum in adult goldfish either by filling them with HRP, or by severing a group of fibers and tracing their degeneration in 2μm plastic sections stained with toluidine blue. Some fish received more than one lesion and others received both lesions and HRP applications. Two major rearrangements of the optic fibers were identified, one at the exit from the eye, the other within the optic tracts.Near the eye the optic fibers appear to be guided by the conformation of the underlying tissue planes that they encounter. The most recently added fibers, from the peripheral retina, grow over the vitread surface of the older fibers toward the blood vessel in the center of the optic nerve head. Behind the eye the fibers follow this blood vessel until it leaves the side of the optic nerve, and the fibers from peripheral retina are left as a single group on the ventral edge of the optic nerve cross section. As a consequence of this pattern of fiber growth the fibers form an orderly temporal sequence in the optic nerve, with the oldest fibers from the central retina on one side of the nerve and the youngest from peripheral retina on the other. In addition, the fibers are ordered topographically at right angles to this central‐to‐peripheral axis, with fibers from ventral retina on each edge of the nerve, dorsal fibers in the center, and nasal and temporal fibers in between. This arrangement of the optic fibers continues with only a little loss of precision up to the optic tracts. A more radical fiber rearrangement, seemingly incompatibe with the fibers simply following tissue planes occurs within the optic tracts.Each newly arriving set of fibers grows over the surface of the optic tracts so that the older fibers come to lie deepest in the tracts. This segregation of fibers of different ages ensures that the rearrangement is limited to each layer of fibers. The abrupt reorganization of the fibers occurs as the tracts split around the nucleus rotundus to form the brachia of the optic tracts. The fibers are then arranged with temporal fibers nearest the nucleus rotundus and nasal fibers on the opposite edges of the brachia. From this point the fibers grow out over the tectal surface to their termination sites with only minimal rearrangements. Therefore the optic fiber rearrangements show evidence of several different sorts of constraints acting on the fibers at separate points in the optic pathway, each contributing to the final orderly arrangement of the fibers on the optic tectum.
Nomenclature and location of avian hypothalamic nuclei and associated circumventricular organs
Authors: Kuenzel Wayne J. , van Tienhoven Ari 
Published: January 2005

AbstractNineteen nuclei and two areas within the avian hypothalamus were identified and located on specific cross‐sectional planes of a stereotaxic atlas of the fowl. Latin terms applied to the nuclei and associated fiber tracts were compared among several authors and a suggested standardized nomenclature presented for hypothalamic structures. Nine circumventricular organs (CVOs) were also located throughout the prosencephalon, mesencephalon, and rhombencephalon of the chicken. A majority of the CVOs were found near nuclei.
Regulation in the number of fly photoreceptor synapses: The effects of alterations in the number of presynaptic cells
Authors: Nicol D. , Meinertzhagen I. A. 
Published: January 2005

AbstractAt the equator of the fly's eye, between dorsal and ventral eye halves, a systematic, natural addition of photoreceptor terminal input occurs at each of the fixed populations of uniquely identifiable postsynaptic interneurons in each cartridge of the first optic neuropile, or lamina. The equatorial cartridges are identical in composition except in having seven and eight receptor terminals (7R and 8R, respectively), compared with six elsewhere (6R cartridges). The effects of this augmented presynaptic input upon the frequency of the chief afferent class of photoreceptor tetrad synapse were studied compared with control data for 6R cartridges (Nicol and Meinertzhagen, ′82). The synapse population size and distribution within five depth levels of the lamina is, on average, approximately constant for all receptor terminals whether from 6R, 7R, or 8R cartridges. The overall determinant ofsynapse frequency is therefore presynaptic. Small (5–6%) average decreases in synapse frequency per receptor in 7R and 8R cartridges compared with 6R co‐vary with similar decreases in membrane area, each synapse occupying a patch of membrane of similar area in all cases. The tetradic postsynaptic composition of synapses was also similar in all cases. Because of the augmented synaptic input to the postsynaptic neurons, a morphometric analysis was undertaken of two (L1 and L2) which receive input as a pair from every synapse. There is the same dendrite number (about 180) in 8R L1/L2 as in 6R L1/L2 but they have different branching patterns, conforming to the different number and configuration of receptor terminals. Thus in an 8R cartridge each terminal is serviced by a comb of fewer dendrites, but each dendrite is longer, fatter, and services more synapses. The area of L1/L2 dendritic membrane exposed is increased, compared with 6R cartridges, in proportion with the number of synapses it participates at postsynaptically, so that all dendrites (6R and 8R) allocate the same mean area (about 0.55 μm2) of postsynaptic membrane per synapse.
On the distribution and origins of substance P in the papillae of the rat tongue: An experimental and immunohistochemical study
Authors: Nishimoto Tatsuya , Akai Michio , Inagaki Shinobu , Shiosaka Sadao , Shimizu Yoshiki , Yamamoto Kazumi , Senba Emiko , Sakanaka Masahiro , Takatsuki Kenichi , Hara Yoshinobu , Takagi Hiroshi , Matsuzaki Takashi , Kawai Yuriko , Tohyama Masaya 
Published: January 2005

AbstractThe distribution and the orgins of substance P (SP)‐positive fibers in the papillae of the rat tongue were investigated by means of the indirect immunofluorescent method.Three types of papilla contain SP‐positive fibers, though the number ofthese fibers varies from papilla to papilla. The circumvallate papilla contains the greatest number of SP‐positive fibers, followed by the foliate papillae and the fungiform papillae; the filiform papillae lack SP‐positive fibers. The papillar SP‐positive fibers form dense bands in the lamina propria just beneath the epithelium. Some of the fibers enter the epithelium and the taste buds. It should be stressed that not every taste bud is provided with SP‐positive fibers: Only 95% of the taste buds in the foliate papillae, 70% of the taste buds in the fungiform papillae, and 40% of the taste buds in the circumvallate papillae contain detectable SP‐positive fibers. Unilateral section of the glossopharyngeal nerve resulted in a complete disappearance of SP‐positive fibers in the foliate papillae on the operated side, and a slight decrease in the circumvallate papillae on both sides. Bilateral section of the glossopharyngeal nerve resulted in a complete disappearance of SP‐positive fibers in the foliate and circumvallate papillae. Following unilateral section of the chorda tympani, SP‐positive fibers in the tastebuds of the fungiform papillae disappeared completely. In addition, unilateral neurotomy of the mandibular nerve resulted in a complete disappearance of SP‐positive fibers in the epithelium of the fungiform papillae. These facts strongly indicate that SP in the foliate and circumvallate papillae is supplied by the glossopharyngeal nerve, SP in the taste buds of the fungiform papillae by the chorda tympani, and SP in the epithelium of the fungiform papillae by the third division of the trigeminal nerve.
Androgen‐Concentrating cells in the periventricular brain of the female rhesus monkey
Authors: Sheridan Peter J. , Hagino Nobuyoshi , Weaker Frank J. 
Published: January 2005

AbstractAlthough androgens act on the primate central nervous system to modulate both endocrine functions and a number of limbic‐related behaviors, little is known about the anatomical location of the neurons which sequester these steroids in primates. To determine the prime location of these androgen‐concentrating neurons in the forebrain of the primate, we injected three castrated female rhesus monkeys in the femoral vein with 1 μg of 5α‐dihydro (1, 2, 4, 5, 6, 7‐3H) testosterone (3H‐DHT, 107 Ci/mmole) per kg of body weight. One of these animals also received an IV injection of 100 μg/kg body weight of unlabeled dihydrotestosterone (DHT) to serve as a control. One hour after the injection of 3H‐DHT we rapidly exsanguinated each animal. The forebrain was sliced and blocks containing the amygdala, diencephalon, frontal pole, and hippocampus were frozen and stored in liquid nitrogen until processing. The tissue was then processed for autoradiography. A specific topographic pattern of nuclear concentration of DHT or one of its metabolites was obtained in neurons of the basal hypothalamus, preoptic region, amygdala, and hippocampus. This pattern was similar to that found in rodent species.
The motor nuclei and primary projections of the facial nerve in the monitor lizard Varanus exanthematicus
Authors: Barbas‐Henry Heleen A. 
Published: January 2005

AbstractThe location of the motor nuclei and the projection of the primary afferent fibers of the facial nerve of the reptile Varanus exanthematicus were studied by means of the HRP method and the anterograde degeneration technique. The motor nuclei are located ventrolaterally in the rhombencephalon and are constituted by a medial cell group consisting of large, polygonal cells and a lateral cell group consisting of medium‐sized, spindleshaped, and multipolar cells. From HRP applications to the various branches of the facial nerve it could be concluded that the medial cell group represents the branchiomotor nucleus and the lateral cell group the superior salivatory nucleus. The efferent axons from the motor nuclei course dorsomedially toward the fourth ventricle, where they form a genu, and exit from the brainstem in the ventral fiber bundle of the facial nerve.The primary afferent fibers enter the brainstem in the dorsal bundle ofthe facial nerve. This bundle courses medially, enters the solitary tract, and diverges into rostrally and caudally running fibers. Part of the caudally directed fibers leave the solitary tract and course laterally toward the descending trigeminal tract. Some fibers enter the nucleus of this tract. There was no noticeable terminal degeneration in the solitary tract or in the descending trigeminal tract or its nucleus.