bluuebunny/crossref_metadata_2025_split huggingface dataset:
The development of axonal connections in the central olfactory system of rats
Authors: Schwob James E. , Price Joseph L. 
Published: May 2005

AbstractThe development of the cytoarchitecture and axonal connections of the central olfactory system were studied in fetal and neonatal rats from E16. In contrast to neocortical development, the olfactory cortex lacks a distinct cortical plate. In the piriform cortex and the olfactory tubercle the cellular laminae emerge simultaneously, while in the anterior olfactory nucleus, there are morphogenetic gradients from superficial to deep as well as from caudal to rostral which parallel the known cytogenetic gradients. Parallel morphogenetic and cytogenetic gradients are also present in the lateral to medial axis of the olfactory tubercle.The projection from the olfactory bulb and the associational projections from the piriform cortex begin to develop well before birth. At E17 fibers from the bulb are limited to the lateral olfactory tract (LOT) and the molecular layer just deep to it, and then spread out caudally, laterally, and medially away from the LOT. This sequence of innervation parallels and predicts the density of innervation in the adult: those areas which are innervated first (such as the piriform cortex deep to the LOT) ultimately receive the heaviest innervation; conversely, those areas which are innervated very late (such as the medial olfactory tubercle) receive the lightest projection.The intracortical projections from the anterior and posterior piriform cortex extend into layer I ipsilaterally by E20 and obtain their adult distribution by the middle of the first postnatal week. On the other hand, fibers from the anterior olfactory nucleus and the entorhinal area do not reach their full adult extent until the second postnatal week. Similarly, the crossed projection of the anterior piriform cortex to the contralateral posterior piriform cortex does not grow into layer I until this later time. The timing of fiber ingrowth showed no relation to the trajectory or eventual areal or laminar termination of fibers. As with the olfactory bulb projection, the timing may influence the density of termination.Centrifugal fibers to the bulb are demonstrable around the time of birth both by the retrograde transport of horseradish peroxidase (HRP) and by the anterograde transport of 3H‐leucine. The arrival of additional fibers during the remainder of the first postnatal week parallels the known cytogenetic and morphogenetic gradients in the areas in which they arise.The projections of the olfactory cortex to the lateral hypothalamic area and the mediodorsal thalamic nucleus are evident before birth. This correlates with the early generation of the cells which give rise to these projections.
The development of lamination of afferent fibers to the olfactory cortex in rats, with additional observations in the adult
Authors: Schwob James E. , Price Joseph L. 
Published: May 2005

AbstractThe complementary distribution of the fibers from the olfactory bulb and the intracortical associational fibers to layers Ia and Ib, respectively, of the olfactory cortex has been examined in both adult and neonatal rats, using horseradish peroxidase (HRP) and 3H‐leucine as double tracers in the same animal. The observations presented here confirm and extend the previous demonstration (Price, '73) that in the adult the two projections are essentially nonoverlapping throughout the olfactory cortex. Indeed, when the distribution of axons from the olfactory bulb (labeled by HRP inserted into a cut in the LOT) is compared on the same section with that of associational fibers (labeled by 3H‐leucine injected into the cortex), the overlap between the two projections is limited to a zone only 5–10 μm in width in both the piriform cortex and olfactory tubercle.In contrast, at P1 the two projections overlap throughout layer I, although the bulbar and associational fibers are slightly concentrated superficially and deeply in layer I, respectively. This overlap is especially prominent in the part of the anterior piriform cortex deep to the LOT. During the remainder of the first postnatal week, this overlap resolves and by P7 the segregation of the two sets of afferent fibers is nearly equivalent to that seen in the adult.However, there are several instances in adults where the segregation of these afferents does not develop. First, a relatively small population of aberrant axons derived from the LOT may be traced from layer Ia into layer Ib and then back to layer Ia. Most of these axons are large in diameter and lack the boutonlike varicosities found on smaller axons in layer Ia. They are most prominent in areas where the cortex is highly curved. Second, in layer I of the nucleus of the lateral olfactory tract, bulbar and associational fibers are extensively intermingled. In this case also, the bulbar fibers are large in diameter with only a few boutonlike varicosities.The developmental emergence of afferent segregation and its breakdown in cases where the fibers from the olfactory bulb do not form boutons suggest that an interaction between the two distinct sets of fibers and the dendritic field is responsible for the normal development of this segregation and that this interaction depends on the process of synaptogenesis.
The development of physiological responses of the piriform cortex in rats to stimulation of the lateral olfactory tract
Authors: Schwob James E. , Haberly Lewis B. , Price Joseph L. 
Published: May 2005

AbstractExtracellular recording techniques in rats were used to follow the postnatal development of the evoked response of the piriform cortex to electrical stimulation of the lateral olfactory tract (LOT) from birth to adulthood. As in other species, LOT shock in adult rats produces short‐latency activation of units in piriform cortex and an extracellular field potential consisting of three components: a surface‐negative component, the A1 wave (corresponding to the cortical monosynaptic EPSP evoked by the LOT fibers); a second surface‐negative component, the B1 wave (corresponding to reactivation of layer I dendrites by intracortical fibers); and a late surface‐positive component, the period 2 wave. A conditioning shock 20–150 msec before the test shock profoundly inhibits both evoked unit activity and the B1 wave, while it facilitates the A1.At birth, units can be orthodromically activated by LOT stimulation in association with the A1 wave. There is also a surface‐positive spikelike wave, the S wave, which represents the summation of cortical unit activity. The B1 wave is apparent early in the first postnatal week. However, in contrast to the prominent inhibition in the adults, for the first few days after birth, single‐unit responses, multiple‐unit activity, and the S wave are all facilitated by a preceding conditioning shock with intervals of 200 msec or less, in association with the facilitation of the A1 wave. A shift to inhibition is apparent with longer intershock intervals of 300–700 msec, which exceed the period during which paired shocks facilitate the A1 wave. During the remainder of the first two postnatal weeks, partial suppression of evoked activity with intervals of less than 200 msec appears and progressively increases in strength, but inhibition at very long intershock intervals remains greater in magnitude. During this time, the duration of the inhibitory period also decreases to near the adult value of 200–300 msec. In the third postnatal week the pattern was similar to that in the adult, but the inhibition was still clearly weaker than in adults. These results suggest a delayed maturation of the cortical inhibitory circuitry; this conclusion has also been suggested by previously published observations in the developing neocortex and hippocampus.In addition, the acceleration with age of the conduction velocity of axons in the LOT was analyzed. The adult value of 9.6 m/sec was not achieved until some time after postnatal day 15, which parallels the myelinization of the tract as observed with the light microscope.
Golgi‐like immunoperoxidase staining of dopamine neurons in the reticular formation of the rat brainstem using antibody to tyrosine‐hydroxylase
Authors: Köhler Christer , Goldstein Menek 
Published: May 2005

AbstractThe distribution and morphology of presumed dopaminergic neurons within the reticular formation (RF) and the ventrolateral tegmental area (VLT) were studied by using a specific antibody to the enzyme that converts tyrosine to dihydroxyphenylalanine, tyrosine‐hydroxylase (TH), in combination with a sensitive immunoperoxidase method (Hsu et al., '81). Incubation of thick (70–120 μm) sections for 3–5 days in high dilutions of antibody resulted in staining of TH‐immunoreactive neurons in a Golgi‐like fashion. Analysis of serial sections cut in the coronal, horizontal, and parasagittal planes revealed an extensive system of TH‐positive neurons in the RF and VLT extending from the Edinger‐Westphal nucleus caudally to the level of the decussations of the superior cerebellar peduncle. Within this region, the TH‐positive cells belong to two subgroups: (1) a relatively well‐defined population of cells aggregated in the reticular formation (corresponding to cell group A8 of Dahlström and Fuxe, '64), and (2) a more loosely defined group of cells that appears to be continuous with the cells of the nucleus raphe linearis. This latter cell group extends laterally from the midline to the nucleus parapeduncularis.An analysis of the individual TH‐immunoreactive cells revealed large differences in their morphology. Thus, the somata of TH‐positive cells in the RF and the VLT are fusiform, ovoid, or triangular. A majority of the TH neurons are of medium (long axis: 15–35 μm) to large (long axis: 35–40 μm) size. While the cells in the A8 area appeared relatively homogeneous, the TH‐positive cells of the VLT showed great variations in dendritic branching pattern and orientation. Taken together, the present study has shown that within the RF and the VLT, the TH‐immunoreactive neurons are more numerous than hitherto recognized, and that this cell group consists of a morphologically heterogeneous population of dopamine‐synthesizing neurons.
The thalamostriatal projection in the cat
Authors: Beckstead Robert M. 
Published: May 2005

AbstractThe organization of the projections from the intralaminar and other thalamic nuclei to the caudate nucleus (CD), putamen (PU), nucleus accumbens (Acc), and olfactory tubercle (TO) were examined in the cat by autoradiography after deposits of 3H‐amino acids in individual thalamic nuclei and by retrograde cell labeling after intrastriatal deposits of wheat‐germ‐conjugated horseradish peroxidase.All of the rostral intralaminar nuclei, here considered to include the central lateral (CL), paracentral (PC), central medial (CeM), and rhomboid nuclei (Rh), project to the striatum. Projections closely associated with those of the rostral intralaminar group arise from cells of the paraventricular nucleus (PV) and a region lateral to the stria medullaris. These nuclei, which roughly form a ring around the mediodorsal nucleus, project in a highly particular, but loosely arranged topographic pattern to all parts of the striatum. The medially located cells in Rh, PV, and those alongside the stria medullaris project mainly to medial parts of Acc and CD; the dorsolaterally located cells of CL project mainly to the dorsolateral parts of CD and PU; cells in PC and CeM project to progressively more ventral and medial parts of CD and PU, and the lateral part of Acc.Superimposed on this projection from the rostral intralaminar region is the projection from the caudal intralaminar group including the centromedian (CM), parafascicular (PF), and subparafascicular nuclei (subPF). Together these nuclei project in a loosely but specifically organized topography to the entire striatum. The lateral and dorsal parts of CD and PU receive fibers mainly from CM. Ventral and medial parts of CD and PU and Acc receive fibers mainly from PF; TO receives fibers from subPF and the ventral part of PF.Several nuclei in the lateral nuclear mass of the thalamus also project to particular parts of the striatum. Thus, cells in the rostromedial part of the ventral anterior nucleus project to the head of CD and some cells in the rostral part of the ventromedial nucleus project to the head of CD and to PU. Several cells scattered in the lateral posterior complex project to lateral parts of the head of CD, and cells in the rostral extension of the medial subdivision of the posterior nuclear complex project to lateral parts of the head and body of CD. Finally, several cells of the paratenial nucleus project selectively to Acc.These data provide a detailed map of the total thalamostriatal projection in the cat and, hence, form a basis for more specific functional questions about this poorly understood system.
Appearance and distribution of neurofilament immunoreactivity in iris nerves
Authors: Seiger Åke , Dahl Doris , Ayer‐LeLievre Christiane , Björklund Håkan 
Published: May 2005

AbstractWe have used antiserum raised against neurofilament (NF) protein and indirect immunofluorescence techniques to visualize neuronal structures in rodent, cat, and cow irides. In the adult rat iris a large population of nerve fibers with a nonautonomic distribution show NF‐like immunoreactivity. In whole mounts, smooth fluorescent fibers were seen in a fine‐meshed plexus from the sphincter margin to the ciliary processes. Superimposed, a sparse pattern of thick meandering axon bundles were seen. Electroblotting and peroxidase immunochemical staining techniques unequivocally showed the presence of all three NF polypeptides in the adult rat iris.Adult mouse irides showed a somewhat sparser pattern of NF‐positive nerves than that of the rat. Adult guinea pig irides contained irregular NF‐positive fibers and few axon bundles. In cryostat‐sectioned cat iris numerous irregularly distributed individual fibers were found, whereas in similarly sectioned cow iris thick NF‐positive axon bundles were more numerous. By embryonic day 18 numerous sparse NF‐positive axons were seen, and the subsequent gradual increase in both axons in bundles and fine‐meshed plexuses of individual fibers produced an appearance similar to that in the adult by 6 days of postnatal age. One week after grafting of irides to the anterior eye chamber, most NF‐positive nerves had disappeared from the iris grafts. Sympathetic and parasympathetic denervation of the irides did not influence the distribution of the NF‐positive iris nerves. Five days after electrothermal lesion of the trigeminal nerve just distal to its ganglion a large proportion of the NF‐positive nerves had disappeared from the iris. All perikarya in the parasympathetic ciliary and most perikarya in the superior cervical sympathetic and in the trigeminal sensory ganglion showed NF immunoreactivity.The present report shows a way to visualize nonautonomic nerve populations in stretch‐prepared as well as sectioned irides by immunofluorescence techniques using an antiserum to neurofilament protein.
The ratio of dorsal root ganglion cells to dorsal root axons in sacral segments of the cat
Authors: Chung Kyungsoon , Coggeshall Richard E. 
Published: May 2005

AbstractProcesses of dorsal root ganglion cells are depicted as being unbranched until they reach the spinal cord or periphery. This is an important concept because, for example, branching of these processes might be a basis for referred pain. Recently several studies indicate that axons of rat dorsal root ganglion cells branch in or near the ganglion. The present study extends this work by showing that there are approximately 1.4 dorsal root axons for each dorsal root ganglion cell in sacral segments of the adult cat, and these data are interpreted as indicating that many dorsal root axons in this animal also branch. Thus this study provides further evidence to indicate that a revision of our ideas about the organization of primary sensory cells is desirable.In addition, this study provides data to indicate that the numbers of both dorsal root ganglion cells and dorsal root axons differ on the right as compared to the left side of the same segment.
Auditory brainstem anomalies in albino cats: II. Neuronal atrophy in the superior olive
Authors: Conlee John W. , Parks Thomas N. , Romero Cardy , Creel Donnell J. 
Published: May 2005

AbstractIn a previous paper (Brain Res., 260:1–9, 1983) we reported that albino cats show abnormal auditory brainstem evoked responses that appear to arise from structural defects in or near the superior olivary complex. In the present study, neuronal cross‐sectional area in brainstem nuclei was compared in albino and normally pigmented adult cats. The albinos were true tyrosinase‐negative (cc) and should not be confused with the deaf white cat (W); the albinos are not deaf. Neurons in the medial superior olivary nucleus (MSO) of albinos were, on average, 41% smaller than in pigmented animals; there was no overlap in the neuronal size distributions for the two groups of animals. Cell size in the lateral superior olive, medial nucleus of the trapezoid body, ventral nucleus of the lateral lemniscus, anteroventral cochlear nucleus, dorsal cochlear nucleus, and facial nucleus was also smaller (by 9–21%) in albinos than in pigmented animals but none of these differences was statistically reliable. In the abducens nucleus, neurons were 12% larger in albinos than in pigmented animals, demonstrating that neuronal size in the albinos is not uniformly smaller. Several lines of evidence suggest that the auditory system defects in albinos are related to abnormal pigmentation rather than to other gene effects. It is possible that a subtle pigment‐related disruption of inner ear development in albinos results in a central cascade of atrophic changes along the auditory pathway.
Quantitative analysis of the dendrites of cat phrenic motoneurons stained intracellularly with horseradish peroxidase
Authors: Cameron William E. , Averill David B. , Berger Albert J. 
Published: May 2005

AbstractAll the dendrites (N = 37) generated by four phrenic motoneurons were analyzed following intracellular injection of horseradish peroxidase. The dendritic arbors produced from each of these stem dendrites were studied in detail. The mean number of stem dendrites produced by a phrenic motoneuron was 9.7, their mean diameter was 6.0 μm, and their mean combined diameter was 58.3 μm. The length at which a phrenic motoneuronal dendrite terminated was 1.236 μm, with several end terminals extending more than 2 mm from the cell body. The mean value for the combined lengths of all segments originating from a single stem dendrite was 5.3 mm. A full spectrum of dendritic branching patterns was observed from simple (five unbranched) to complex, the latter producing up to ninth‐order branches. Most terminal and nonterminal dendritic segments tapered, producing a mean diameter reduction of 34%, or approximately 9% per 100‐μm length. All phrenic motoneurons exhibited a steady decrease in the combined dendritic parameter (Σd3/2) with distance from the soma as a result of tapering and end‐branch termination. The mean surface area and volume of a phrenic motoneuronal dendrite were 35.3 × 103 μm2 and 25.9 × 103 μm3, respectively. The dendrites constituted greater than 97% of the total phrenic motoneuronal surface area, with 75% of this area lying outside of a 300‐μm radius from the cell body.The diameter of a stem dendrite was positively correlated with its combined dendritic length, number of terminal branches, dendritic surface area, and volume. Despite this strong correlation, the value of total dendritic surface area calculated using the power equation derived from the dendritic surface area versus stem dendritic diameter plot was not a consistent estimator of the total dendritic surface area directly measured for these four phrenic motoneurons. It is suggested that this inconsistency may be the result of a heterogeneity in the phrenic motoneuronal population and/or in the dendrites projecting to the different terminal fields.
Cortical and brain stem afferents to the ventral thalamic nuclei of the cat demonstrated by retrograde axonal transport of horseradish peroxidase
Authors: Nakano Katsuma , Kohno Masako , Hasegawa Yasuo , Tokushige Akinori 
Published: May 2005

AbstractAfter horseradish peroxidase (HRP) injections into various parts of the ventral thalamic nuclear group and its adjacent areas, the distribution of labeled neurons was compared in the cerebral cortex, basal ganglia, and the brain stem. The major differences in distribution patterns were as follows: Injections of HRP into the lateral or ventrolateral portions of the ventroanterior and ventrolateral nuclear complex of the thalamus (VA‐VL) produced retrogradely labeled neurons consistently in area 4γ (lateral part of the anterior and posterior sigmoid gyri, lateral sigmoid gyrus and the lateral fundus of the cruciate sulcus), the medial division of posterior thalamic group (POm), suprageniculate nucleus (SG) and anterior pretectal nucleus ipsilaterally, and in the nucleus Z of the vestibular nuclear complex bilaterally.Injections into the medial or dorsomedial portion of the VA‐VL resulted in labeled neurons within the areas 6aβ (medial part of the anterior sigmoid gyrus), 6aδ (anterior part of ventral bank of buried cruciate sulcus), 6 if. fu (posterior part of the bank), fundus of the presylvian sulcus (area 6aβ), medial part of the nucleus lateralis posterior of thalamus and nucleus centralis dorsalis ipsilaterally, and in the entopeduncular nucleus (EPN) and medial pretectal nucleus bilaterally. Only a few neurons were present in the contralateral area 6aδ.After HRP injections into the ventral medial nucleus (VM), major labeled neurons were observed in the gyrus proreus, area 6aβ (mainly in the medial bank of the presylvian sulcus), and EPN ipsilaterally, and in the medial pretectal nucleus and substantia nigra bilaterally.Following HRP injections into the centre médian nucleus (CM), major labeled neurons were found in the areas 4γ, 6aβ, and the orbital gyrus ipsilaterally, and in the EPN, rostral and rostrolateral parts of the thalamic reticular nucleus, locus ceruleus, nucleus reticularis pontis oralis et caudalis and nucleus prepositus hypoglossi bilaterally. The contralateral intercalatus nucleus also possessed labeled neurons. With HRP injections into the paracentral and centrolateral nuclei, labeled neurons were observed in the gyrus proreus and the cortical areas between the caudal presylvian sulcus and anterior rhinal sulcus ipsilaterally, and in the nuclei interstitialis and Darkschewitsch bilaterally. Minor differences in the distribution pattern were observed in the superior colliculus, periaqueductal gray, mesencephalic and medullary reticular formations, and vestibular nuclei in all cases of injections.