bluuebunny/crossref_metadata_2025_split huggingface dataset:
The pontocerebellar system in the rat: An HRP study. I. Posterior vermis
Authors: Azizi S. A. , Mihailoff G. A. , Burne R. A. , Woodward D. J. 
Published: January 2005

AbstractThis study was undertaken to determine the origin of projections from the basilar pontine nuclei (BPN) and nucleus reticularis tegmentis pontis (NRTP) to the posterior vermal lobules VI‐IX of the rat cerebellum. We describe the topographical organization of this component of the pontocerebellar projection, and the congruence of the cells of origin in the basilar pons with some of the major pontine afferent systems including the corticopontine and tectopontine projections. Horseradish peroxidase (HRP) was injected into the midline cerebellar vermal zones of Long‐Evans hooded rats. The more sensitive chromogens, tetramethyl benzidine and benzidine dihydrochloride, were used to reveal the location of labeled neurons.With injections located near the midline, groups of labeled cells were observed bilaterally within the BPN. The basic trend of the projections noted was: lobule VIa receives a nonfocal projection from nearly all subdivisions of the BPN throughout its rostrocaudal extent, as well as a substantial input from NRTP. Lobules VIb‐c receive input from NRTP, the rostral pons, and from the ventral, lateral, and medial groups of the middle BPN. A combination of lateral, medial, and dorsolateral groups of cells in the middle BPN project to lobule VII, in addition to projections from limited groups of cells in the rostral BPN. Lobule VIII receives afferents from the caudal aspect of the pontine gray. Lobules IXa‐b receive afferents from the medial and peduncular groups in the middle BPN, whereas lobule IXc receives inputs from a medial group and a small lateral cluster of cells in the caudal aspect of the BPN.Pontine neurons projecting to the posterior vermis originate from areas which appear to receive descending inputs from visual, auditory, and somatosensory regions of the cerebral cortex. However, a large number of pontine and NRTP neurons projecting to lobules VI and VII are located within the terminal fields of tectal neurons, perhaps indicating a stronger input from the tectum rather than visual and auditory cerebral cortical regions.
Regeneration of axons and nerve cell bodies in the CNS of annelids
Authors: Hulsebosch C. E. , Bittner G. D. 
Published: January 2005

AbstractThe neuron addition hypothesis predicts that species that add CNS neurons during a particular ontogenetic stage should regenerate ablated somata better than species that add few, if any, neurons to the CNS during that same stage. We report that CNS nerve cells do not regenerate in three species of adult (reproductively competent) leeches (Hirudo medicinalis, Haemopus grande, and Macrobdella decora), which do not increase the number of neurons in any portion of the CNS. Nereis virens, a polychaete that adds CNS neurons to newly forming ganglia in the adult stage, also does not regenerate CNS neurons. Conversely, CNS neurons, including a pair of uniquely identifiable somata, do regenerate in Clymenella torquata, a polychaete that has a constant number of neurons in the adult stage. Hence, the results of our study suggest that several versions of the neuron addition hypothesis cannot predict CNS regenerative abilities in adult annelids. Finally, we report that severed stumps of CNS axons do not degenerate rapidly in Nereis or Clymenella, and that both species can regenerate severed CNS axons presumably by morphologic fusion or physiologic activation of surviving stumps.
Morphogenesis and synaptogenesis of the zebrafish mauthner neuron
Authors: Kimmel Charles B. , Sessions Stanley K. , Kimmel Reida J. 
Published: January 2005

AbstractThe shape of the Mauthner neuron (M‐neuron) and the distribution of its afferent synapses were studied between days 2 and 6 after fertilization in the zebrafish Brachydanio rerio. This interval is just after the outgrowth of M‐dendrites begins, and during this time the M‐cell acquires its definitive shape. The M‐cell has two large invariant dendrites: The lateral dendrite terminates in the sensory neuropil of the acoustico‐lateral area, and the ventral dendrite terminates in the neuropil of the motor tegmentum. Fine dendrites are present, and mostly arise from three regions; from the terminus of each major dendrite and from the ventral surface of the perikaryon. The number and position of fine dendrites within each of these sets is variable, even among animals from a single isogenic clone. M‐cells with improper numbers or positions of large dendrites were never encountered, even early in development. This suggests that their outgrowth is a highly directed process.Large numbers of afferent synapses are formed on the M‐cell during the time of dendrite outgrowth. By day 6 there is a mosaic pattern of morphologically distinctive terminals that is similar to the pattern of the adult goldfish M‐cell. Identified categories of terminals include (1) myelinated club endings, on the distal part of the lateral dendrite, (2) boutons, on the dendrites and perikaryon, (3) unmyelinated club endings, on the dorsomedial portion of the perikaryon adjacent to the axon cap, and (4) spiral fiber terminals within the axon cap. The nonrandom nature of the input may be ascertained by observing the distribution of electrotonic or gap junctions on the cell surface. These are frequently encountered on the initial segment of the axon (spiral fiber terminals), ventral dendrite and ventral perikaryon (boutons), and distal lateral dendrite (myelinated club endings). Gap junctions are only rarely observed on the dorsal surface of the cell, although this region, like others of the cell, receives large numbers of chemical synaptic contacts. This pattern is similar at all stages studied, which suggests that no large rearrangements in synaptic contacts occur during this developmental period. We discuss these observations in relation to the hypothesis that patterned dendritic growth of the M‐cell is directed by synaptic interactions with the afferents.
Sensory control of dauer larva formation in Caenorhabditis elegans
Authors: Albert Patrice S. , Brown Susan J. , Riddle Donald L. 
Published: January 2005

AbstractAs a sensory response to starvation or overcrowding, Caenorhabditis elegans second‐stage larvae may molt into a developmentally arrested state called the dauer larva. When environmental conditions become favorable for growth, dauer larvae molt and resume development. Some mutants unable to form dauer larvae are simultaneously affected in a number of sensory functions, including chemotaxis and mating. The behavior and sensory neuroanatomy of three such mutants, representing three distinct genetic loci, have been determined and compared with wild‐type strain. Morphological abnormalities in afferent nerve endings were detected in each mutant. Both amphid and outer labial sensilla are affected in the mutant CB1377 (daf‐6)X, while another mutant, CB1387 (daf‐10)IV, is abnormal in amphidial cells and in the tips of the cephalic neurons. The most pleiotropic mutant, CB1379 (che‐3)I, exhibits gross abnormalities in the tips of virtually all anterior and posterior sensory neurons. The primary structural defect in CB1377 appears to be in the nonneuronal amphidial sheath cells. The disruption of neural organization in CB1377 is much greater in the adult than in the L2 stage. Of all the anterior sense organs examined, only the amphids are morphologically affected in all three mutants. Thus, one or more of the amphidial neurons may mediate the sensory signals for entry into the dauer larva stage in normal animals. Using temperature‐sensitive mutants we determined that the same defects which block entry into the dauer stage also prevent recovery of dauer larvae.
First somatosensory cortical columns and associated neuronal clusters of nucleus ventralis posterolateralis of the cat: An anatomical demonstration
Authors: Kosar Eva , Hand P. J. 
Published: January 2005

AbstractMicrolesions (30–275 microns in diameter) were placed in VLPm of the cat and the terminal axonal degeneration in SI cortex was stained using the Fink‐Heimer I technique. Following each of these microlesions, small, localized patches or subcolumns of degeneration, relativly light in density, were observed within laminae IIIb and IV of SI when viewed in the coronal plane. In addition, a few degenerating fibers ascended to lamina I. These multiple subcolumns had distinct radial boundaries and were narrow in the mediolateral plane (80–120 microns in width) but elongated rostro‐caudally (2500–3000 microns in length). Localized patches of degeneration were separated at their widest points by a distance of 500 microns medio–laterally, but at various rostro–caudal levels of SI were observed to merge into larger columns of degeneration (250–400 microns) and then separate again into smaller multiple patches (i.e., a “zebra‐like” pattern).Small injections of HRP into the forelimb region of area 3b or rostral area 1–2 of SI resulted in the labeling of small, discrete clusters of neurons in the ventral regions of VPLm. The clusters examined ranged in size from 140–350 microns in medio–lateral diameter and were elongated rostro–caudally (up to 500 microns in extent); virtually all cells within a cluster appeared labeled, but not equally so.A pattern of HRP labeling different from that observed following area 3b and rostral area 1–2 injections was observed following injections into more caudal regions of area 1–2 and into SII cortex. The labeling that resulted from these injections was not in the form of neuronal clusters but instead labeled cells tended to be scattered in more dorsal regions of VPLm. This scattering did not appear to be random since the labeled neurons were grouped within the same general area of VPLm. Labeling was distributed throughout a number of cell clusters, comprising only a small proportion of cells within each cluster. The pattern of labeling seen after caudal area 1–2 and SII injections differed only in its rostro–caudal extent within VPLm. SII injections generally resulted in labeling along the full rostro–caudal dimension of VPLm.A differential organization of the anatomy of thalamocortical projections to the various subdivisions of SI and to SII was noted in this study. It is postulated that the multiple, discrete patches of degeneration in laminae IIIb and IV of SI represent a portion of the somatosensory cortical columns and that the HRP‐labeled clusters seen in VPLm following area 3b and rostral area 1–2 injections are the subcortical equivalents of these subcolumns.
Retinal recipient nuclei in the painted turtle, Chrysemys picta: An autoradiographic and HRP study
Authors: Bass Andrew H. , Northcutt R. Glenn 
Published: January 2005

AbstractRetinofugal pathways in the painted turtle were examined with autoradiographic and HRP methods. The majority of the retinal fibers decussate at the optic chiasm and course caudally to terminate in 12 regions of the diencephalon and mesencephalon. The pars dorsalis of the lateral geniculate nucleus is the densest target in the thalamus. Two nuclei dorsal to pars dorsalis—the dorsal optic and dorsal central nuclei—receive optic input. Three nuclei ventral to pars dorsalis are retinal targets—the ventral geniculate nucleus, nucleus ventrolateralis pars dorsalis, and nucleus ventrolateralis pars ventralis. Contralateral fibers course through the pretectum where they terminate in nucleus geniculatis pretectalis, nucleus lentiformis mesencephali, nucleus posterodorsalis, and the external pretectal nucleus. Retinal fibers also terminate within the superficial zone of the optic tectum. HRP material demonstrates three optic fiber layers—laminae 9, 12, and 14. Optic fibers leave the main optic tract as a distinct accessory tegmental optic pathway and terminate in the basal optic nucleus. Ipsilateral retinal terminals occur in a pars dorsalis and a pars ventralis of the lateral geniculate nucleus, the dorsal optic nucleus, nucleus posterodorsalis, the basal optic nucleus, and in laminae 9 and 12 of the optic tectum. Rostrally, the ipsilateral tectal fibers occupy two zones along the medial and lateral tectal roof; these zones converge caudally and are continuous along the caudal wall of the tectum.
A golgi‐electron microscopic study of goldfish optic tectum. II. Quantitative aspects of synaptic organization
Authors: Meek J. 
Published: January 2005

AbstractThe size, density, and number of the synaptic contacts of three types of interneurons (types I, III, and XIV of Meek and Schellart, 1978) and three types of efferent neurons (types VI, XII, and XIII) of the goldfish optic tectum were quantified by means of a quantitative stereological study of Golgi‐EM serial sections. Furthermore, an estimation was made of the percentage of optic terminals on these six cell types and of the ratio between terminals with pleomorphic and terminals with round vesicles.The mean density of contacts per receptive component (i.e. the cell body and the different parts of the dendritic tree) varies from 0 to 100 per 100/μm2 surface, corresponding to 0‐8% receptive surface. Each cell type has a characteristic average density as well as a characteristic density distribution along the distinct components. This suggests that the receptive components of the tectal cell types investigated have a predetermined density and that a morphological classification of tectal cells has functional relevance.The mean length of the contact zones in the ultrathin sections varies from 213 to 332 nm for identified postsynaptic elements and from 188 to 293 nm for identified presynaptic elements. The size of the contacts on the distinct receptive components appears to be primarily related to the tectal lamination pattern. Distinct types of axons, however, have characteristic mean sizes of contacts. This might suggest that the size of the contacts, contrary to their density, is primarily determined by the presynaptic elements.The mean number of synaptic contacts calculated per cell type is as follows: type XIV, 200; type III, 450; type VI, 1,400; type I, 2,100; type XII, 4,200; and type XIII1, 5,400. Multiplication of these numbers with the number of cells per tectal half shows that the population of type XIV cells has by far the most synaptic contacts, since their low number of synaptic contacts is clearly overruled by their high frequency of occurrence.Optic terminals, identified by their characteristic mitochondria and large round vesicles, appear to contribute to about 10–20% of the contacts on identified postsynaptic elements in layer 5. The ratio between presynaptic elements with pleomorphic vesicles and those with round vesicles shows a slight tendency to increase when the distance to the origin of the axon decreases.It is concluded that a combination of the Golgi‐EM technique with quantitative stereological methods appears well suited to the study of the synaptic organization of brain centers, and that combination of quantitative Golgi‐EM with neuronal tracing methods (degeneration, HRP, autoradiography) offers good prospects for detailed investigations of neuronal connectivity.
The middle temporal visual area in the macaque: Myeloarchitecture, connections, functional properties and topographic organization
Authors: Van Essen D. C. , Maunsell J. H. R. , Bixby J. L. 
Published: January 2005

AbstractThe location, topographic organization, and function of the middle temporal visual area (MT) in the macaque monkey was studied using anatomical and physiological techniques. MT is a small, elliptically shaped area on the posterior bank of the superior temporal sulcus which can be identified by its direct inputs from striate cortex and by its distinctive pattern of heavy myelination. Its average surface area is 33 mm2, which is less than 3% of the size of striate cortex. It contains a complete, topographically organized representation of the contralateral visual hemifield. There are substantial irregularities in the detailed pattern of topographic organization, however, and the representation is significantly more complex than that found for MT in other primates. Much of MT is devoted to the representation of central visual fields, with the emphasis on central vision being similar to that found in striate cortex.Electrophysiological recordings have confirmed previous reports of a high incidence of direction selective cells in MT. The transition in functional properties, from cells lacking direction selectivity outside MT to direction selective cells within, occurs over a distance of 0.1–0.2 mm or less along the lateral border of MT. Such a transition does not occur along the medial border, however, as the cortex medial to MT contains many cells with strong direction selectivity. Nevertheless, this region differs from MT in its myeloarchitecture, its lack of inputs from striate cortex, and the large size of its receptive fields. These results demonstrate the existence of three distinct visual areas on the posterior bank of the superior temporal sulcus which can be distinguished on the basis of both physiological and anatomical criteria.
Freeze‐fracture study of the crayfish stretch receptor
Authors: Tao‐Cheng Jung‐Hwa , Hirosawa Kazushige , Nakajima Yasuko , Peng H. Benjamin 
Published: January 2005

AbstractThe crayfish slow‐adapting stretch receptor was fixed under relaxed or stretched conditions (twice the relaxed length) and then processed for freeze‐fracture study. The sensory neuron membrane had evenly distributed intramembrane particles mostly on its P face. The density of these particles was higher in the cell body than in the dendritic tips, which are the terminal portions of the dendrites. The dendritic tips were cylindrical under the relaxed condition and showed deformations with stretch stimuli. When they were fixed under the stretched condition with 1.6% glutaraldehyde in 0.12 M phosphate buffer (the total osmolarity of this fixative is isosmotic with the physiological solution), the dendritic tips showed regional swelling and shrinkage. The intramembrane particle density of the swollen parts decreased and there were particle‐free patches of membrane, whereas the particle density of the shrunken parts increased. On the other hand, when the receptor was fixed with 1.6% glutaraldehyde in 0.2 M phosphate buffer (the total osmolarity is hyperosmotic but buffer osmolarity is isosmotic), the diameter of the dendritic tips became smaller, and their membrane particle densities were almost the same as that under the relaxed condition. The sheath cells covering the sensory neuron were characterized by their sheet‐like profiles, gap junctions, and crater‐like protrusions. The receptor muscle membrane had longitudinal foldings, occasional invaginations, peripheral couplings, stringshaped particle aggregates, and band‐shaped particle aggregates.
Comparative scanning electron microscopic investigations of the sensory epithelia in the teleost sacculus and lagena
Authors: Popper Arthur N. 
Published: January 2005

AbstractScanning electron microscopic studies were conducted on the sensory epithelia of the auditory portions of the ears in teleost species representing wide taxonomic diversity. A number of the features of the ears investigated resem‐ bled features found in other teleost species, although some major exceptions to earlier patterns were found, particularly in the saccular sensory epithelium. The saccular maculae of all but one species contained basically similar ciliary bundles on the sensory hair cells while there was some significant variation on the lagenar maculae. Hair cell orientation patterns on the sacculus contained four orientation groups in all of the species, other than the mormyrid, Gnathonemus, which only had two groups. Lagenar maculae had two orientation groups, and the orientation patterns were similar to one another. The most divergent form of lagenar macula was found in Gnathonemus. These data, combined with data from earlier investigations, provide a broad overview of the surface features of the ear in teleost fishes. Most significantly, it now appears that there are at least five different saccular hair cell orientation patterns among teleost fishes, and all of these patterns are found spread through many major teleost taxa. While there is some similarity in ear structures among some groups of closely related species, such as the Elopomorpha and the Gadiformes, it is becoming more apparent that there is extensive convergence in a number of features of the teleost ear that most likely reflect similar selective pressures during the evolution of the ear. The nature of these selective pressures, however, are not well understood.
Physiological demonstration of multiple representation in the forelimb region of the cat motor cortex
Authors: Pappas C. L. , Strick P. L. 
Published: January 2005

AbstractEarlier studies in primates have demonstrated a double representation of the distal forelimb in area 4. In this study intracortical stimulation was used to map the representation of the forelimb in area 4 of the cat. Maps of individual animals revealed two spatially separate representations for the distal forelimb in area 4. Two “digit zones.” regions in which threshold stimulation evoked contractions limited to digit musculature, were seen in all animals. Although the absolute location of the two digit zones varied among animals, the zones were always separated by a field in which more proximal musculature was represented. In some experiments EMG activity was monitored from selected forelimb muscles in order to determine the muscles represented in the two zones. Activity of the same digit muscle could be evoked by stimulation in each digit zone. This analysis demonstrated that some digit muscles were represented in both the digit zones. Thus, this study demonstrates that multiple representation of the distal forelimb in area 4 is not an isolated species‐specific phenomenon, but is likely to be a generalized pattern of motor cortex organization.