bluuebunny/crossref_metadata_2025_split huggingface dataset:
Afferent influences on brain stem auditory nuclei of the chicken: Time course and specificity of dendritic atrophy following deafferentation
Authors: Deitch Jeffrey S. , Rubel Edwin W 
Published: January 2005

AbstractThe time course and specificity of the changes in dendritic morphology following deafferentation were examined in nucleus laminaris of young chickens. The dendrites of nucleus laminaris neurons are segregated into dorsal and ventral domains, which are innervated separately from the ipsilateral and contralateral nucleus magnocellularis, respectively. Transection of the crossed dorsal cochlear tract deafferents the ventral dendrites of nucleus laminaris bilaterally without interrupting the matching input to the dorsal dendrites.In 10‐day‐old chicks, atrophy of the ventral dendrites began immediately after transecting the tract; the ventral dendrites were 10% shorter by 1 hour and 16% shorter by 2 hours after deafferentation. The length of the ventral dendrites progressively decreased over the next 2 weeks, resulting in at least a 60% loss of ventral dendrite 16 days after surgery. The dorsal dendrites of the same cells, whose afferents remained intact, did not change in length during the time course of this study. However, 16 days after the lesion, spines appeared on the normally smooth dorsal and ventral dendrites. The time course of dendritic atrophy and its restriction to the deafferented postsynaptic surface are related to possible mechanisms by which afferents regulate and maintain their target neurons.
Central organization of eighth nerve and mechanosensory lateral line systems in the brainstem of ictalurid catfish
Authors: Finger Thomas E. , Tong Shang‐Liang 
Published: January 2005

AbstractThe octavolateral sensory systems in teleost fish comprise at least four distinct hair‐cell sensory modalities which are processed separately within the CNS. Two of these modalities, the mechanosensory lateral line system and the eighth nerve auditory system, have been implicated in the animal's ability to detect and localize underwater vibrations. Distinct mechanosensory lateral line and auditory nuclei are present within the torus semicircularis, the midbrain homologue of the inferior colliculus. The present study utilized horseradish peroxidase tracing techniques to delineate those areas of the lower brainstem which are involved in auditory as opposed to mechanosensory lateral line processes.The primary mechanosensory nucleus of the medulla, n. medialis, projects directly to the optic tectum and to the mechanosensory nucleus of the torus semicircularis. Nucleus medialis receives input from primary lateral line nerve fibers as well as from a number of sites within the CNS: n. praeeminentialis pars ventralis, and the eminentia granularis and lobus caudalis of the cerebellum. The n. praeeminentialis itself receives a descending input from the mechanosensory nucleus of the torus semicircularis. These mechanosensory lateral line pathways are parallel to, but distinct from, those of the electrosensory lateral line system.Auditory signals reach the midbrain via an entirely separate route. The octaval nerve terminates in a column of five medullary nuclei. Of these, only the anterior and descending octaval nuclei maintain a direct but sparse projection to the auditory nucleus of the midbrain. The bulk of the auditory input to the midbrain involves a newly described medullary nucleus, the medial auditory nucleus of the medulla. This nucleus receives input from the descending octaval nucleus and projects bilaterally to the auditory nucleus of the torus semicircularis. It is suggested that the medial auditory nucleus of the medulla is homologous to portions of the superior olivary complex of other vertebrates.
Reduced effects of monocular deprivation on a population of A‐laminae neurons in the cat's dorsal lateral geniculate nucleus
Authors: Peduzzi Jean D. , Hickey T. L. 
Published: January 2005

AbstractThe generation of nerve cells for the cat's dorsal lateral geniculate nucleus takes place between embryonic day (E) 22 and E32. Neurons generated before E28 exhibit a full range of soma sizes and morphological features, whereas neurons generated after E28 have only smaller somata and a more limited array of morphological features. We measured the effects of monocular deprivation on neurons in the cat's dorsal lateral geniculate nucleus that were generated at different times, with birthdates defined by injections of 3H‐thymidine. Whereas populations of nerve cells generated before E28 exhibit changes in cell size that are, on average, typical of those seen in monocularly deprived cats, populations of nerve cells generated after E28 are, on average, less affected by visual deprivation.
Thalamic projections of nucleus reticularis thalami of cat: A study using retrograde transport of horseradish peroxidase and fluorescent tracers
Authors: Steriade M. , Parent A. , Hada J. 
Published: January 2005

AbstractThe retrograde transport of horseradish peroxidase (HRP) and fluorescent tracers after injections in various thalamic nuclei was used to investigate the relative density of retrogradely labeled cells in different districts of reticularis thalami (RE) nuclear complex of cat. The RE nucleus was left virtually free of labeling only after injections localized into the anterior nuclear group; in those experiments, heavy retrograde labeling was obtained in mammillary nuclei. The major targets of RE cells proved to be centralis lateralis‐paracentralis (CL‐PC) and centrum medianum‐parafascicularis (CM‐PF) intralaminar nuclei. The projections to various intralaminar nuclei mainly arise in the rostral pole and rostrolateral part of RE nucleus and are reciprocal to intralaminar‐RE pathways disclosed by Jones ('75). The RE territories labeled following injections in relay and associational nuclei are more restricted and are located contiguously and slightly anteriorly to a given nucleus. There was a very small proportion of doubly labeled RE cells after injections with fluorescent tracers in different nuclei. This was not due to a technical failure since many double‐labeled neurons were found in the same material in medial globus pallidum after thalamic and midbrain injections (see companion paper by Parent and Steriade, '84). We conclude that most individual RE axons arborize in only one thalamic nucleus or nuclear group. An additional finding was the existence of intralaminar‐to‐relay (CL‐PC to VA‐VL) projections.
Efferent projections of the neonatal cat superior colliculus: Facial and cerebellum‐related brainstem structures
Authors: Stein Barry E. , Spencer Robert F. , Edwards Stephen B. 
Published: January 2005

AbstractThe superior colliculus develops its influence over eye and pinna movements gradually during postnatal maturation. Because superior colliculus cells respond earlier in postnatal life to nonvisual than to visual cues, it seemed likely that efferents involved in pinna movements would develop earlier than those involved in eye movements. In the present study, we examined the projections of the superior colliculus to structures related to the cerebellum and facial nucleus believed to be involved in eye‐head coordination and pinna movements. We did this by using the autoradiographic and horseradish peroxidase tracing techniques in 11 kittens, ranging in age from several hours to 14 days postnatal, and in seven adult cats.Even in the youngest animals studied, a dense projection was observed from the superior colliculus to each of the target structures examined. These included the (1) parabigeminal nucleus, (2) paralemniscal zone, (3) dorsolateral pons, and (4) inferior olive. Surprisingly, the only projection observed to undergo any postnatal maturational changes was the one to the paralemniscal zone (involved in the pinna‐movement circuit of the superior colliculus), and the changes appeared as a reorganization of the terminal field rather than an increase in the density of transported label. Thus, no evidence was obtained to support our expectation that the superior colliculus efferents involved in orientation of the pinnae would develop earlier than those involved in visual orientation. Instead, each of the efferent projections of the superior colliculus examined in this study appears to be laid down prenatally and becomes adultlike long before functional maturity is reached. Presumably, then, the formation and elaboration of synaptic connections are the protracted postnatal processes that limit the functional properties of these neonatal efferent pathways.
The morphology of optic tract axons arborizing in the superior colliculus of the hamster
Authors: Sachs George M. , Schneider Gerald E. 
Published: January 2005

AbstractSingle axons innervating the superficial layers of the hamster's superior colliculus (SC) were visualized using an HRP‐filling technique. Five types of axons were distinguished. Experiments involving the removal of retinal and/or cortical input showed that three of these axon types originated in the contralateral retina with the fourth type most likely originating in the visual cortex. The origin of the fifth type, a widely branched varicose axon, is apparently subcortical.The two major types of presumed retinotectal axons (types U and L1) project to the stratum griseum superficiale (SGS) in a bilaminar pattern. Type U axons take relatively direct paths from the layer of optic fibers to form dense terminal arbors in the upper half of the SGS. Terminal fields for type U fibers showed fairly consistent dimensions. Their rostrocaudal extent ranged from 90 μm to 190 μm, averaging about 120 μm.Type L1 axons were thicker than type U axons and terminated in deeper regions of the SGS and in the stratum opticum (SO). Single axons of this type often gave rise to multiple branches which took separate, circuitous paths to a common terminal field. Terminal fields for type L1 axons varied more in extent than did type U fields, but 58% of them had fields 90–150 μm in extent.Each of the axon types found can be related to previous studies of populations of tectal afferents. The two major types of retinofugal axons fit a scheme of parallel ascending pathways. The findings also have interesting implications for the study of axonal development.
Diameters and terminal patterns of retinofugal axons in their target areas: An HRP study in two teleosts (Sebastiscus and Navodon)
Authors: Ito Hironobu , Vanegas Horacio , Murakami Takeshi , Morita Yasuhiro 
Published: January 2005

AbstractStudies in various vertebrate classes, particularly amphibians and mammals, have revealed that retinal ganglion cells with different functional properties project by means of axons of correspondingly different diameters onto specific target regions. Whether a similar pattern exists in teleosts is partly investigated in the present study. HRP was injected into the optic nerve of Sebastiscus and Navodon. The calibers of intraretinal HRP‐labeled axons were classed as fine (ca. 0.8 μm), medium (ca. 1.3 μm), and coarse (ca.2.5 μm). The calibers of HRP‐labeled retinofugal axons were then determined in their target areas, and these can be summarized as follows: Optic hypothalamus: fine, medium. Lateral geniculate nucleus: fine. Dorsolateral thalamic nucleus: fine, medium. Area pretectalis: fine. Nucleus of the posterior commissure: fine, medium. Area ventralis lateralis, contralateral: fine, medium, coarse; ipsilateral: coarse. Optic tectum, stratum opticum: fine, medium; stratum fibrosum et griseum superficiale: fine, medium, coarse, segregated in sublayers; stratum album contrale: fine, medium, coarse. Therefore, fine fibers were found to reach all target areas except the ipsilateral area ventralis lateralis, and these were the only fibers found in the lateral geniculate nucleus, area pretectalis, and stratum griseum centrale of the optic tectum. Coarse fibers, on the other hand, were found only in the area ventralis lateralis and the optic tectum (stratum fibrosum et griseum superficiale and stratum album centrale). Terminal patterns of these fibers were also studied. Most fine fibers take tortuous courses giving off a few branches and terminate with many varicosities, and medium and coarse fibers give off several finer branches and terminate with bulbous swellings. The physiological significance of these findings is discussed.In addition, retrogradely labeled (retinopetal) cells were found in the olfactory bulb and the area ventralis pars ventralis of the telencephalon, as well as in the preoptic area and the dorsolateral thalamic nucleus.
Effects of strabismus and monocular deprivation on the eye preference of neurons in the visual claustrum of the cat
Authors: Perkel David J. , LeVay Simon 
Published: January 2005

AbstractVisual response properties of neurons in the dorsocaudal claustrum were studied in two cats reared with convergent strabismus and three cats reared with monocular lid‐suture. In the normal claustrum, most cells respond about equally well to stimulation of either eye (Sherk and LeVay, '81). In the strabismic animals, there was a partial breakdown of binocularity: most cells remained binocular but were influenced more strongly by one eye (usually the contralateral eye) than the other. The loss of binocularity was less extreme in the claustrum than in area 17 of the same animals. In the monocularly deprived cats, claustral cells responded exclusively to the experienced eye. We interpret the changes observed in the claustrum as reflecting changes in the ocular dominance of cortical inputs to the claustrum, rather than as evidence for plasticity within the claustrum itself.Autoradiography was used to study the return projection from claustrum to cortex in monocular deprivation. The cortical labeling pattern resembled that seen in normal cats. To examine whether this return projection might be involved in reducing cortical responsiveness to the deprived eye, recordings were made from area 17 of a monocularly deprived cat before and after ablation of the ipsilateral claustrum by injection of kainic acid. Following ablation, there was no unmasking of cortical responses to the deprived eye. Thus the cortico‐claustral loop does not appear to suppress cortical responses to the deprived eye.
FMRFamide immunoreactivity in the nervous system of the medusa Polyorchis penicillatus
Authors: Grimmelikhuijzen C. J. P. , Spencer A. N. 
Published: January 2005

AbstractThree different antisera to the molluscan neuropeptide Phe‐Met‐Arg‐Phe‐amide (FMRFamide) and two different antisera to the fragment RFamide were used to stain sections or whole mounts of the hydrozoan medusa Polyorchis penicillatus. All antisera stained the same neuronal structures. Strong immunoreactivity was found in neurons of the ectodermal nerve nets of the manubrium and tentacles, in neurons of the sensory epithelium, and in neurons at the periphery of the sphincter muscle, Strong immunoreactivity was also present in processes and perikarya of the whole outer nerve ring, in the ocellar nerves, and in nerve cells lying at the periphery of the ocellus. The inner nerve ring contained a moderate number of immunoreactive processes and perikarya, which were distinct from the swimming motor neurons.In contrast to the situation in the hydrozoan polyp Hydra attenuata, no immunoreactivity was found with several antisera to oxytocin/vasopressin and bombesin/gastrin‐releasing peptide.The morphology and location of most FMRFamide‐immunoreactive neurons in Polyorchis coincides with two identified neuronal systems, which have been recently discovered from neurophysiological studies.
The axon reaction of the goldfish mauthner cell and factors that influence its morphological variability
Authors: Zottoli Steven J. , Hangen Donald H. , Faber Donald S. 
Published: January 2005

AbstractThe axon reaction of the goldfish Mauthner cell, elicited by spinal cord transection, included somatic swelling, nuclear eccentricity, chromatolysis, nuclear infolding, and a perinuclear buildup of basophilic material. The latter three changes were found most consistently and showed gradations which were ranked quantitatively.The time of onset of chromatolysis and nucleus‐associated changes depended upon the distance of the wound from the Mauthner cell soma. Specifically, for Mauthner axons cut at 5, 10.5, and 20 mm distal to their somata, the approximate postoperative times of onset were 10, 20, and 40 days, respectively. Mauthner cells axotomized 42 mm distally did not display a consistent axon reaction. Cell atrophy and death were not found in cells axotomized 10.5, 20, or 42 mm from their somata up to 285 postoperative days, but were observed at the longer postoperative intervals (421 days) in neurons cut 5 mm distally and were consistently found in neurons axotomized less than 1.6 mm from their somata.The axon reactions of Mauthner cells within a pair were frequently different. This variability cannot be explained by the influence of cut site or postoperative interval and is hypothesized to result from different metabolic conditions of the individual cells.
Immunoreactive pro‐enkephalin and pro‐dynorphin products are differentially distributed within the nucleus of the solitary tract of the rat
Authors: Lee Hyun Sook , Basbaum Allan I. 
Published: January 2005

AbstractIn this study we examined the distribution of two different endogenous opioid peptides in the nucleus of the solitary tract of the rat medulla. As a marker for immunoreactive enkephalin, we used an antiserum directed against one of the proenkephalin products, methionine enkephalin‐arg‐glyleu (m‐Enk). To identify immunoreactive dynorphin we used an antiserum directed against the prodynorphin product, dynorphin B (Dyn B). The PAP method was used on both colchicine and normal animals.Caudal to the obex, within the commissural nucleus, there is extensive overlap of both immunoreactive m‐Enk and Dyn B terminals and cells. While the cells are morphologically similar, the immunoreactive dynorphin cells are somewhat larger. Rostral to the obex, there is a marked difference in the distribution of the two compounds. Immunoreactive m‐Enk terminals are concentrated medial to the solitary tract; there is minimal staining laterally. In contrast, immunoreactive Dyn B terminals are concentrated lateral to the solitary tract. The rostral cellular distribution of the two opioid peptides follows a similar pattern. The morphology of the medially located m‐Enk and laterally located Dyn B cells is also readily distinguished. The former are small, round cells with minimal dendritic labelling; the latter are larger, pyramidal neurons with prominent apical and basal dendrites. Since the medial and lateral nuclei of the solitary tract have been associated with cardiovascular and respiratory control, respectively, these data suggest that different endorphin families have different functional actions within the nucleus of the solitary tract.
An empirical assessment of stereological formulae applied to the counting of synaptic disks in the cerebral cortex
Authors: Colonnier Marc , Beaulieu Clermont 
Published: January 2005

AbstractKnown quantities of test objects approximating the parameters of cortical synapses were embedded in known volumes of a transparent embedding medium. The material was cut in slabs of appropriate thickness. The mean trace length (d) of the profiles of the test objects was measured and the number of profiles per unit area (NA) was calculated. Various stereological formulae were applied to these data to determine the number of test objects per unit volume (NV). For large numbers of those test objects most closely approximating the parameters of cortical synapses, the formula NV = NA/d and the DeHoff and Rhines formula ('61) for polydispersed circular disks NV = 8NAZ/π2 (where Z is the mean of the reciprocals of the trace lengths) gave accurate results (error ≤ 5%). Other popular formulae and procedures were not as accurate and underestimated their number by as much as 32%.
Synaptic organization of substance P‐like immunoreactive amacrine cells in goldfish retina
Authors: Yazulla Stephen , Studholme Keith M. , Zucker Charles L. 
Published: January 2005

AbstractA class of amacrine cells in the goldfish retina displays substance P‐like immunoreactivity (SPIR). We studied the synaptic organization of SPIR amacrine cells by electron microscopical immunocytochemistry. Amacrine cells showing SPIR have processes which ramify in a very narrow band in layer 3 of the inner plexiform layer. SPIR is restricted to large dense‐cored vesicles (DCVs) which are distributed throughout the dendrites. Processes labeled with SPIR contain a mixture of DCVs and numerous small agranular vesicles. of 88 synaptic contracts analyzed, SPIR processes occurred as the presynaptic element 57 times and as the postsynaptic element 31 times. SPIR processes made synapses upon amacrine and ganglion cell dendrites with equal frequency and received synaptic input from both amacrine and bipolar cells. The stratification of SPIR amacrine cells in proximal sublamina α suggests that their synaptic interactions are restricted to “off” and “on‐off” neurons. However, this is in contrast to published electrophysiological data. Possible explanations for this discrepancy are discussed in detail.
Effects of age on meissner corpuscles: A study of silver‐impregnated neurites in mouse digital pads
Authors: Mathewson R. C. , Nava P. B. 
Published: January 2005

AbstractInvestigation focused on finding qualitative and quantitative evidence of age‐changes in the quantity of neural surface within Meissner corpuscles. These mechanoreceptors were studied in 53 mice (nine age‐groups) ranging from 1.7 to 24 months old. Forepaw digital pads were formalin‐fixed and frozen‐sectioned parallel to each digit and perpendicular to the skin. Serial sections were then silver‐impregnated to allow light microscopic examination of the neurites (axons) in corpuscles.From young (1.7–7 months) to middle age (9–15 months), neurites became more coarse, tortuous, ramified, varicose, and thus more complex. At old age (18–24 months), neurites seemed attenuated and showed more of an irregular winding, twisted, or tangled pattern with less parallel orientation to the skin surface than the regular spiraled, looped, or arched pattern typical at young and middle ages. Corpuscle size appeared greatest at middle age, smallest at young age. Dermal papillae not occupied by corpuscular neurites were most abundant at old age.The number of corpuscles per area and neurites per corpuscle decreased significantly with age, whereas the number of neurite bifurcations per corpuscle increased significantly. Morphometric analysis of neurites projected by a camera lucida onto a planimeter showed that the length of neurites meandering through a fixed interval of tissue increased significantly until age 12 months–evidence of increased tortuosity; the area of neurites measured within the same fixed interval, and the area of neurite terminals changed significantly as inverse parabolic functions of age–evidence of increased volume until middle age, which decreased thereafter.The general trend of these changes implied growth at young age and atrophy at old age. Morphologic changes occurring mostly until middle age increased the surface area of each neurite, presumably to compensate for loss of neural surface caused by decreased number of corpuscles and neurites. However, this proposed compensatory response was lost after middle age as indicated by the morphologic changes thereafter.