bluuebunny/crossref_metadata_2025_split huggingface dataset:
Telodendrites of cone photoreceptors: Structure and probable function
Authors: Kraft Timothy W. , Burkhardt Dwight A. 
Published: January 2005

AbstractIntracellular dye injection and compartmental modeling were used to analyze the structure and function of telodendrites of cones in the retina of the walleye. After identifying the spectral type of an impaled cone on the basis of its response to red and green light, horseradish peroxidase and/or Lucifer Yellow were injected for 1 to 25 minutes. In 38 of 58 recovered cells, dye spread into the telodendrites; so in many cases, the detailed pattern of the telodendritic arbor could be reconstructed from serial sections. Typically, five telodendritic processes, about 1 μm in diameter and 18 gm in length, radiated from the cone pedicle. A majority of the processes terminated at pedicles of neighboring cones. Some of the Lucifer Yellow injections provided evidence for electrical coupling between cones via telodendrites. Calculations from a compartmental model, based on the measured dimensions of cones and telodendrites, indicate that the signal arising in the inner segment spreads with little loss to the end of a telodendrite, whereas about half of the signal is lost in transmission from telodendrite to inner segment. Assuming that each contact point within the telodendritic network is an electrical synapse of 2,500 MΩ, the model shows spatial interaction over a field of some 80 μm, which is comparable to that measured experimentally. Although our anatomical data indicate that orange‐ and green‐sensitive cones may be interconnected via telodendrites, model calculations indicate that such connections do not appreciably distort the intrinsic spectral sensitivity of walleye cones. This outcome agrees with previous experimental results.
The distribution and morphology of parasympathetic preganglionic neurons in the cat sacral spinal cord as revealed by horseradish peroxidase applied to the sacral ventral roots
Authors: Nadelhaft Irving , de Groat William C. , Morgan Charles 
Published: January 2005

AbstractParasympathetic preganglionic neurons in the sacral parasympathetic nucleus (SPN) of the cat were studied by applying horseradish peroxidase (HRP) to the sacral ventral roots. The results were compared to data from earlier experiments in which these same neurons were labelled by HRP applied to the pelvic nerve at a point much further from the spinal cord. The present experiments have shown (1) The total number of neurons in the SPN determined by ventral root labelling is equal to the number obtained by pelvic nerve labelling. This indicates that virtually all SPN neurons send their axons into the pelvic nerve. (2) More extensive dendritic projections from SPN neurons were revealed than in the pelvic nerve experiments. In particular, a strong dendritic projection extended within the lateral marginal zone of the dorsal horn close to Lissauer's tract and horizontal dendrites projected well into the contralateral gray matter, some reaching the contralateral sacral parasympathetic nucleus. (3) The neurons labelled via any one ventral root were all contained within a region equal in length to one spinal segment but shifted rostrally by a small amount. Thus, no evidence was obtained for a long intraspinal pathway in which axons of spinal cord neurons entered ventral roots many segments away from their somata.
Neuromuscular relationships in a muscle having segregated motor endplate zones. II. The response to partial denervation
Authors: Wines Melvin M. , Hall‐Craggs E. C. B. 
Published: January 2005

AbstractThe cranial belly of the anterior gracilis muscle of the rat has two discrete motor endplate zones. A promixal zone is innervated by short branches of the obturator nerve, and a distal zone is innervated by (usually) two longer branches. Each muscle fiber is innervated at a single motor endplate although a substantial number lie within both endplate zones. In addition, motor units are divided between the two zones. In order to dissociate the role of the denervated endplate from that of the denervated muscle fiber in the promotion of motoneuron sprouting, the distal endplate zone in this model was denervated and the response at the proximal zone was studied. Comparisons were made with partial denervation of the muscle by division of the L4 ventral ramus and with partial denervation of the distal endplate zone. Denervation of the distal endplate zone produced profuse terminal sprouting at the proximal zone whereas division of L4 predominantly produced nodal sprouting at both zones. Partial denervation of the distal zone resulted in nodal sprouts in that zone and again mainly terminal sprouts at the proximal zone. The repeated association of terminal sprouting with division of the motor axons supplying the distal zone together with the knowledge that motor units are distributed between the two zones led to the conclusion that the terminal sprouting was stimulated by the reduction in size of motor units rather than by the presence of denervated muscle fibers in the vicinity of the endplates.
Microtubules and calibers in normal and regenerating axons of the sural nerve of the rat
Authors: Espejo Francisco , Alvarez Jaime 
Published: January 2005

AbstractThe calibers and microtubular content of axons were studied in normal and regenerating fibers of the sural nerve from 17 to 122 days after a lesion of the sciatic nerve of young adult rats. During this period (70–175 days of age), the cross‐sectional area of control myelinated axons almost doubled but that of nonmedullated axons did not change. In regenerating nerves, after 122 days of recovery, the cross‐sectional area of myelinated fibers was still 38% below that of the normal side. In contrast, the regenerating nonmedullated population was richer in fine (< 0.2 μm2) and in coarse (> 0.9 μm2) fibers than on the control side; the cross‐sectional area averages were 0.50 and 0.54–0.70 μm2 for the normal and regenerating populations, respectively.The microtubular density of normal 3‐μm myelinated fibers averaged 24.0 microtubules/μm2. In regenerating fibers of the same size the density varied between 19.2 and 23.2 microtubules/μm2. Microtubular density values of normal and regenerating fibers were not statistically different. In nonmedullated fibers, the microtubular content (expressed as microtubular density or number of microtubules per axon) correlated with the caliber of the fiber. In these correlations, only minor differences were observed between regenerating and uninjured fibers.Our results indicate that nonmedullated fibers terminate their radial growth well before myelinated fibers do, and that axonal microtubular content correlates with the local size of the fiber and is largely insensitive to regeneration.
Microtubules and calibers in developing axons
Authors: Faundez Victor , Alvarez Jaime 
Published: January 2005

AbstractThe caliber and microtubular content of growing axons were assessed with the electron microscope in the sural nerve of the rat from birth until the age of 63 days (young adult). The caliber of both nonmedullated and myelinated fibers increased throughout the period of observation. At birth, nonmedullated fibers smaller than 0.2 μm2 represented 69% of the population; at day 63 less than 7% were that small. Irrespective of the age of the rat, the number of microtubule profiles of nonmedullated fibers increased with the cross‐sectional area of the axon although their packing decreased. In myelinated fibers of a given caliber, the packing of microtubules increased with time, and by day 63 the density had reached its final value. In nonmedullated fibers of a given caliber, a similar trend was observed after day 31; i.e., fibers showed a small but consistent increase in density. However, before that, and in contrast to myelinated fibers, nonmedullated fibers of defined calibers exhibited a transient increase in the microl ubular density. Notwithstanding, during the history of an individual fiber the packing of its microtubules may decrease continuously until stabilizing, because the developing fiber is increasing its caliber and hence decreasing its microtubular density. In the 5‐day‐old rats, the caliber spectra of myelinated and nonmedullated axons overlapped in the 0.49–0.83 μm2 range and their microtubular densities were similar.We conclude that the microtubular content of developing axons correlates with caliber, an architectural feature, and is largely independent of growth and of its myelinated condition. We propose that the cytoskeletal rather than the transport function commands the organization of axonal microtubules.
Ultrastructural characterization of choline acetyltransferase‐containing neurons in the basal forebrain of rat: Evidence for a cholinergic innervation of intracerebral blood vessels
Authors: Armstrong David M. 
Published: January 2005

AbstractThe ultrastructural morphology and vascular associations of cholinergic neurons in the horizontal limb of the nucleus of the diagonal band of Broca (nDBBh1) and amygdala of rat were determined by the immunocytochemical localization of choline acetyltransferase (ChAT), the acetylcholine biosynthetic enzyme. Within the nDBBh1 peroxidase reaction product was distributed throughout the cytoplasm of selectively labeled neuronal perikarya and dendrites. Labeled perikarya were characterized by an oval cell body (7–10, μm × 17–26 μm in diameter) in which was located a large nucleus and often a prominent nucleolus. Dendrites were by far the most numerous immunolabeled profiles in the nDBBh1. The labeled dendrites had a cross‐sectional diameter of 0.4–4.6 μm and contained numerous mitochondria and microtubules. Approximately 10% of all immunolabeled dendrites received synaptic contacts from unlabeled presynaptic boutons. In contrast to the relatively large number of ChAT‐labeled dendrites within the nDBBh1, ChAT‐positive axons were less frequently observed and immunolabeled axon terminals were never detected. The labeled axons had an outside diameter of 0.4–1.4 μm and were myelinated. The absence or relative paucity of immunolabeled terminals in the nDBBh1 indicates that most if not all of the cholinergic perikarya within this nucleus are efferent projection neurons. The nDBB is known to have widespread projections to many areas of the neocortex, hippocampus, and amygdala. In the present study we examined the amygdala and observed many ChAT‐labeled axon boutons. The immunolabeled varicosities contained numerous agranular vesicles and although ChAT‐positive termirs als were in direct contact with unlabeled neuronal elements within the amygdala, few if any synaptic densities were detected in a single plane of section. With respect to the vasculature, immunolabeled perikarya and dendrites within the nDBBh1 and axon terminals in the amygdala were often in direct apposition to blood vessels. In many instances the labeled profile was observed lying directly on the basal lamina of a capillary endothelial cell. In no instance, however, were membrane densities observed. The presence of cholinergic neuronal elements contacting the vessel wall provides morphologic evidence suggesting that the neurogenic control of cerebral vasculature is in part, mediated via a cholinergic mechanism.
Anatomical organization of the visual system of the mink, Mustela vison
Authors: McConnell Susan K. , LeVay Simon 
Published: January 2005

AbstractThe organization of the retinogeniculocortical visual system of the mink was studied by anterograde and retrograde tracer techniques, by physiological mapping, and by direct recordings from axonal terminals after injection of kainic acid.In the lateral geniculate nucleus, retinogeniculate afferents are segregated according to eye of origin between the two principal layers, A and Al. Within each of these layers there is a further parcellation according to functional type: on‐center afferents terminate in the anterior leaflets of A and Al, and off‐center afferents in the posterior leaflets. This separation is preserved in area 17: geniculocortical afferents terminate in ocular dominance patches in layer IV, and these patches coexist with an alternating, partially overlapping set of patches for on‐center and off‐center inputs that we have demonstrated previously (McConnell and LeVay: Proc. Natl. Acad. Sci. USA 81:1590–1593. '84). In both the lateral geniculate nucleus and in area 17, the contralateral eye predominates to a much greater extent than in the cat.Visual cortical areas corresponding to the cat's areas 17, 18, and 19 can be identified in the mink, but they are shifted posterolaterally in the hemisphere, and they show less emphasis on the representation of central retina. Mapping studies also revealed the existence of a fourth visual area in the splenial sulcus (area SV) adjacent to the representation of the far periphery in area 17. This area differs from the corresponding region in the cat in that it receives direct projections from the lateral geniculate nucleus and from areas 17 and 18.The lateral geniculate nucleus projects to each of the four cortical areas that were mapped. The bulk of the projection to area 17 is derived from the principal layers, A and Al, while most cells projecting to areas 18 and SV are found in the C‐layer complex. The recurrent projection from area 17 to the lateral geniculate nucleus arises from pyramidal neurons in layer VI, and terminates through all layers of the lateral geniculate nucleus, but most densely in the interlaminar zones. Areas 18 and SV projectt predominantly to the C layers.Areas 17, 18, and SV are reciprocally connected with tiie claustrum and the LP‐pulvinar complex, and project to the superior colliculus: All four visual cortical areas are mutually interconnected; these associational projections arise from both the supragranular and infragranular layers.
Electron microscopic study of synaptic contacts between photoreceptors and HRP‐filled horizontal cells in the turtle retina
Authors: Ohtsuka Teruya , Kouyama Nobuo 
Published: January 2005

AbstractThe synaptic contacts between photoreceptors and horizontal cells in the retina of the turtle (Geoclemys) were studied. Horizontal cells were classified into three types according to their intracellularly recorded spectral responses: Luminosity, biphasic chromaticity, and triphasic chromaticity horizontal cells (LHC, BHC, and THC). These cells were then iontophoretically filled with horseradish peroxidase (HRP). The various types of photoreceptors located within the dendritic field of the HRP‐filled horizontal cells were identified either as rods or as one of the three chromatic types of cones; the latter were identified by the presence and colors of their oil droplets in the inner segments. The synaptic contacts between photoreceptors and labeled horizontal cells were then investigated by light and election microscopy of serial sections on three LHCs, two BHCs, and one THC. LHCs made synaptic contacts with about 100 photoreceptors, including rods and three chromatic types of cones; two‐thirds of these photoreceptors contacted the cell body and the remaining its axon terminal. BHCs contacted about 30 cones; red‐, green‐, and blue‐sensitive cones in the ratio of 3:4:1. THC contacted 20 cones; red‐ and blue‐sensitive cones in the ratio of 2:1. The dendritic processes of HRP‐filled horizontal cells were found as the lateral element of the ribbon synaptic complexes. The present finding suggests that the responses of BHC and THC to red flashes are fed directly from red‐sensitive cones in addition to the feedback pathway of cone‐horizontal cell connections in the previous studies.
Topography of corticopontine remodelling after cortical lesions in newborn rats
Authors: Kartje‐Tillotson Gwendolyn , Neafsey E. J. , Castro Anthony J. 
Published: January 2005

AbstractAutoradiographic and axonal degeneration staining techniques were combined in individual animals to study the distribution of corticopontine fibers. In normal animals, forelimb and hindlimb motor cortical projections terminated somatotopically within the ipsilateral pontine nuclei. Sparse crossed projections also displayed a somatotopic pattern. After unilateral sensorimotor cortical lesions in newborn rats, an increase in the crossed corticopontine fibers arising from the opposite unablated motor cortex was observed at maturity. These fibers distributed in a topographic pattern similar to the normal ipsilateral corticopontine pattern; forelimb motor cortical projections terminated rostral to hindlimb motor cortical fibers. The specific distribution of the anomalous fibers suggests that they constitute a functional pathway.
Pathway of acetylcholinesterase containing nerves to the major cerebral arteries in rats
Authors: Hara Hideaki , Weir Bryce 
Published: January 2005

AbstractThe pathway of nerves containing acetylcholinesterase (AChE) to the major cerebral arteries was investigated in the rat. In this species, the internal ethmoidal artery (IEA) arises from the anterior cerebral artery (ACA) and anastomoses with the external ethmoidal artery (EEA), forming the ethmoidal rete on the cribriform plate. The ethmoidal nerve (EN) and EEA enter the cranial cavity through the ethmoidal foramen. Densely distributed adventitial nerve plexi were present around the IEA, ethmoidal rete, and EEA. Many thick nerve bundles were found in the periadventitial layers in association with these vessels. Around the EN, just before it enters the ethmoid foramen, intensely staining nerve bundles were present that entered the cranial cavity with the EN.After unilateral. section of the EN and EEA, a marked decrease of the nerve fibers was observed around the arteries of the anterior part of the circle of Willis on the operated side, whereas the basilar artery (BA) showed a moderate decrease in the AChE activity. After bilateral section of the EN and EEA, nerves disappeared from around all the major cerebral vessels including the BA. Section of the EEA alone did not produce any visible change of the cerebral perivascular innervation.The present study suggests that (1) AChE‐containing nerves on the cerebral arteries arise from the AChE‐positive nerve bundles, which enter the cranial cavity with the EN through the ethmoid foramen; (2) The anterior part of the circle of Willis is innervated unilaterally by the AChE‐positive nerve bundles from the ethmoidal foramen, whereas the BA receives bilateral innervation.
Neurofilament proteins in fish: A study with monoclonal antibodies reacting with mammalian NF 150K and NF 200K
Authors: Dahl D. , Crosby C. J. , Bignami A. 
Published: January 2005

AbstractMonoclonal antibodies were obtained upon immunization of mice with chicken brain antigen and with the two high molecular weight neurofilament proteins (NF 150K and NF 200K) isolated from bovine spinal cord by anion exchange chromatography. By the immunoblotting procedure, the antibodies selected for this study reacted with bovine NF 150K and NF 200K. By the same procedure the antibodies reacted with sea raven, goldfish, sea bass, shark, and trout spinal cord extracts. In goldfish and sea raven the antibodies stained a single band at approximately 150 kDa and 200 kDa, respectively. Two bands were stained in the shark, sea bass, and trout. In the shark and sea bass these bands were in the molecular weight range of mammalian NF 150K and NF 200K. In the trout the upper band was approximately 150 kDa and the lower band 130 kDa. Our findings suggest an early origin of NF 150K and NF 200K in vertebrate phylogeny as well as considerable divergence in several species.
Synaptic reorganization in the motor trigeminal nucleus of the rat following neonatal 6‐hydroxydopamine, treatment
Authors: Hemmendinger Lisa M. , Moore Robert Y. 
Published: January 2005

AbstractThe synaptic organization of the motor trigeminal nucleus in adult rats treated neonatally with 6‐hydroxydopamine (6‐OHDA) was investigated quantitatively and compared with control nuclei. No statistically significant change was detected in the distribution of axon terminals in the neuropil, and the total number of axosomatic contacts per unit length of membrane was identical in the control and 6‐OHDA‐treated groups. However, 6‐OHDA treatment causes a significant redistribution of the four morphologically distinct bouton populations forming axosomatic contacts with trigeminal motoneurons. Terminals containing lucent axoplasm and spherical synaptic vesicles have been identified as norepinephrine neuron terminals (Card et al.: J. Comp. Neurol. 250:469‐484, '86). These and terminals with lucent axoplasm and pleomorphic vesicles are increased in number whereas terminals with dense axoplasm and either spherical or pleomorphic synaptic vesicles are decreased in number in the 6‐OHDA‐treated brains compared to controls.These results confirm that the norepinephrine hyperinnervation observed in histofluorescence preparations following neonatal 6‐OHDA treatment reflects an increase in absolute numbers of norepinephrine terminals. The finding that the total number of axosomatic contacts per unit length of membrane remains constant while the proportions of individual afferent classes vary may indicate that the trigeminal motoneuron plays a major role in determining the overall density but not necessarily the individual specificity of its axosomatic innervation.The motor trigeminal nucleus is a useful model system in which to investigate both the response of norepinephrine fibers to neonatal 6‐OHDA treatment and the respective roles of a target neuron and its afferents in the regulation of appropriate quantitative innervation patterns in the central nervous system.
Thalamic inputs to visual areas 1 and 2 in the rabbit
Authors: Weyand Theodore G. , Swadlow Harvey A. 
Published: January 2005

AbstractThalamic projections to two cortical representations of the visual field, visual areas 1 and 2 (V1, V2), in the rabbit were studied by using the retrograde transport of horseradish peroxidase (HRP). Physiological guidance was employed to inject small amounts of HRP into topographically defined regions of V1 or V2. Injections restricted to V1 revealed a dense projection from the dorsal lateral geniculate nucleus as well as projections from the pulvinar, the posterior thalamic nucleus, and the ventral lateral nucleus. Injections restricted to V2 revealed projections from the pulvinar, the ventral lateral nucleus, and the posterior thalamic nucleus, but only a slight projection from the dorsal lateral geniculate nucleus. V2, but not V1, receives an input from neurons within the fiber plexus between the dorsal lateral geniculate nucleus and the pulvinar. Finally, the neurons in the lateral geniculate nucleus that project to V2 have larger somata on average than those that project to V1 (x + 18.25 μm vs. 14.04 μm, P <.001).