bluuebunny/crossref_metadata_2025 huggingface dataset:
Central projections from cat suboccipital muscles: A study using transganglionic transport of horseradish peroxidase
Authors: Bakker D. A. , Richmond F. J. R. , Abrahams V. C.
Published: January 2005

Central projections of suboccipital muscle nerves were examined following exposure of cut peripheral nerves to the tracer horseradish peroxidase. Labelled fibers entered the Cl and C2 dorsal roots and accumulated in the dorsolateral part of the dorsal funiculus. Many labelled fibers entered the grey matter of Cl to C3 in ventrally directed bundles which passed medially to the base of the dorsal horn. No terminal labelling was apparent in superficial layers of the dorsal horn. However, labelled fibers ramified extensively throughout, medial parts of the intermediate laminae, in and around the central cervical nucleus. Labelled fibers also projected toward the ventral horn. In cats subjected to ventral root section at the time of peripheral nerve exposure, a modest distribution of reaction product was observed deep in the ventral horn. In cats which did not undergo ventral root section, anterograde projections in the ventral horn were obscured by the simultaneous retrograde filling of motoneurons both in the ventromedial nucleus and on the medial and lateral borders of the gray matter. Labelled axons also coursed rostrally into the medulla where they formed a circumscribed bundle between the main cuneate nucleus and the spinal nucleus of V. Three consistent regions of HRP deposition could be identified at medullary levels. Dense accumulations of reaction product were present in circumscribed regions of the external cuneate nucleus (ECN) throughout its rostrocaudal extent. A second zone of dense labelling occurred in the intermediate nucleus of Cajal, where it appeared to form a continuing column rostral to the central cervical nucleus in C1–C3. Sparse labelling was restricted to a third zone in the ventrolateral part of the main cuaeate nucleus.
2‐deoxyglucose labelling of the infrared sensory system in the rattlesnake, Crotalus viridis
Authors: Gruberg Edward R. , Newman Eric A. , Hartline Peter H.
Published: January 2005

Infrared (IR) responsive nuclei in the rattlesnake Crotalus viridis were identified by using 14C‐2‐deoxyglucose (2DG) and autoradiography. Following 2DG intracardial injection, the IR‐sensitive pit organ was stimulated periodically with an IR stimulus for 5 hours. The nucleus of the lateral descending trigeminal tract (LTTD, the primary IR sensory nucleus) was labelled heavily with 2DG. Labelling was bilateral, but somewhat heavier ipsilateral to the stimulated pit organ. The nucleus reticularis caloris (RC, the secondary nucleus of the IR system) was lightly labelled ipsilaterally. The middle laminae of the contralateral optic tectum (which contain IR‐responsive units) were distinctly labelled; the corresponding layers of the ipsilateral tectum were lightly labelled. A subcerebellar nucleus not known to be part of the IR system was heavily labelled bilaterally. No consistent labelling was found in the diencephalon or telencephalon.

Since units in the LTTD do not respond to stimulation of the contralateral pit yet the LTTD is labelled with 2DG when there is contralateral pit stimulation, several controls were carried out. Unilateral injection of 3H‐proline into LTTD revealed no projection to the contralateral LTTD. In a monocularly, visually stimulated animal with both pits occluded, the LTTD still showed heavy but equal 2DG labelling bilaterally. In addition, the outer layers of the contralateral optic tectum were heavily labelled. No 2DG labelling of the LTTD was obtained when branches of the trigeminal nerve innervating the LTTD were previously cut.

These results suggest that much of the 2DG labelling in the LTTD is due to spontaneous ongoing activity from the pit organ rather than from IR evoked activity. Using single‐unit recording, almost all LTTD units were found to have high spontaneous firing rates. IR stimulation increases the firing rate above spontaneous levels. When the afferent trigeminal nerves were cut, LTTD cell activity was almost totally silenced.
Projection patterns of lateral‐line afferents in anurans: A comparative HRP study
Authors: Fritzsch Bernd , Nikundiwe Alfeo M. , Will Udo
Published: January 2005

Primary projections of the anterior and posterior lateral‐line nerves were traced by means of transganglionic transport of horseradish peroxidase in species belonging to five of the six anuran superfamilies. Both anterior and posterior lateral‐line nerve afferents each enter the brain via a single root which divides into two or more bundles. These bundles carry fibers from neuromasts only. No separate dorsal fascicle and no ampullary organs as in urodeles and gymnophions have been found. All bundles join in the neuropil of the nucleus intermedius to form ascending and descending fascicles. Two distinct fascicles are found in species showing little collateralization. No fasciculation is found in species with an elaborate telodendritic arborization. Afferents of the anterior lateral‐line nerve run ventromedially and those of the posterior lateral‐line nerve dorsolaterally within the ipsilateral nucleus intermedius neuropil. Rostrally they terminate in the vicinity of the eminentia granularis and caudally in the vicinity of the calamus scriptorius.

The metamorphic changes in the alar plate do not support the hypothesis of Larsell ('34) as to a change in function of second‐order lateral‐line neurons into second‐order auditory neurons. The rostral part of the nucleus intermedius shows numerous degenerating neurons at metamorphic climax whereas the caudal part becomes part of the nucleus caudalis of adult anurans. Besides the members of the Pipoidea, there is at least the genus Bombina which retains parts of the lateral‐line system.

The term “dorsal island”, its relevance for any part of the anuran brain, and the possible relation between absence of electroreception and the development of the nucleus dorsolateralis are discussed.
The mormyrid mesencephalon. III. Retinal projections in a weakly electric fish, Gnathonemus petersii
Authors: Lázár G. , Libouban S. , Szabo T.
Published: January 2005

The optic nerve and the retinal projections were studied in a mormyrid fish, Gnathonemus petersii, by using Fink‐Heimer, HRP, cobalt labeling, and autoradiographic tracing techniques. The retinal fibers terminate bilaterally in the following places: suprachiasmatic nucleus, dorsolateral optic nucleus, optic nucleus of the posterior commissure, cortical nucleus, ventral pretectal area, optic tectum, and the accessory optic terminal field. The number of uncrossed fibers is relatively high in the suprachiasmatic nucleus, but negligibly small in the other retinal terminal fields. In the lateral geniculate nucleus and pretectal nucleus only crossed retinal fibers could be detected.

The visual system of Gnathonemus is compared to that of other fishes, amphibians, and reptiles and the possible homologies are proposed. The comparison points to the conclusion that the visual system is less developed in Gnathonemus. This nocturnal species lives in turbid waters and has a special electric sense which may permit compensation for the reduced visual capacity.
The central projection of muscle afferent fibres to the lower medulla and upper spinal cord: An anatomical study in the cat with the transganglionic transport method
Authors: Nyberg Gunnar , Blomqvist Anders
Published: January 2005

The projection of muscle afferent fibres to the medulla oblongata and upper spinal cord was studied in the cat by using transganglionic transport of wheat germ agglutinin‐horseradish peroxidase conjugate. The results demonstrate a precise, musculotopic termination pattern in the external cuneate nucleus; thus, fibres from the intrinsic muscles of the paw terminate medially; those from forearm, arm, and shoulder muscles terminate progressively more laterally; and those from neck and thoracic muscles terminate in the ventrolateral and dorsolateral parts, respectively. Muscle afferent fibres to the main cuneate nucleus terminate in the ventral “reticular” region of the nucleus, with a sparse projection also to the ventral part of the rostral and caudal regions, including the base of the dorsal horn. Fibres from the neck muscles terminate slightly more laterally in the ventral region than do those from the limb muscles, but otherwise, and thus contrary to the case in the external cuneate nucleus, no topographic organization was detected. In the spinal cord, projection was found to laminae I and V, and from the musculature of the back of the neck to the central cervical nucleus.
Callosal connections of the posterior neocortex in normal‐eyed, congenitally anophthalmic, and neonatally enucleated mice
Authors: Olavarria Jaime , Van Sluyters Richard C.
Published: January 2005

Following multiple injections of horseradish peroxidase into the posterior neocortex of one hemisphere, we examined the distribution of retrogradely labeled cells and anterogradely labeled terminations in tangential and coronal sections through contralateral areas 17 and 18 in throe groups of adult mice: normal‐eyed (ZRDCT‐n and C57Bl/6J strains), congenitally anophthalmic (ZRDCT‐an strain), and neonatally enucleated (ZRDCT‐n strain). In agreement with previous studies, we observed that the pattern of callosal connections in areas 17 and 18 of normal‐eyed mice contains the following features: (1) a dense band of callosal cells and terminations separating the interiors of areas 17 and 18, which have relatively few callosal connections, (2) a ring‐like configuration anterolateral to area 17, (3) a region of dense labeling lateral to area 18, (4) a narrow band of labeling bridging the posterior portion of area 18, and (5) a region of labeling anteromedial to area 17.

We find that all these features of the normal callosal pattern are recognizable in congenitally anophthalmic mice. Their presence in mice that never had eyes supports the hypothesis that central visual pathways can develop many aspects of their connectivity in the absence of input from the periphery. However, we also find that the details of certain features of the callosal pattern in congenitally eyeless mice often differ from those of the same features in normal‐eyed mice, and that the between‐animal variability in the appearance of these features is higher in eyeless mice. These latter findings indicate that the eyes are needed during normal development to fine‐tune the pattern of callosal connections.

Our results also reveal that the callosal pattern in neonatally enucleated mice does not differ significantly from that in congenitally anophthalmic mice, indicating that the period in which the eyes guide callosal development extends into postnatal life. While the present data do not delineate the time course of this period, the finding of similarly abnormal callosal patterns in congentially anophthalmic and neonatally enucleated mice suggests that the eyes exert little if any influence prenatally. Finally, examination of coronal sections indicates that the laminar distribution of callosal connections develops normally in both groups of eyeless mice.
Modification of fibrin matrix formation in situ enhances nerve regeneration in silicone chambers
Authors: Williams Lawrence R. , Varon Silvio
Published: January 2005

The spatial‐temporal progress of nerve regeneration was examined in silicone chambers of three different volume capacities: 11, 25, and 75 μl. In all chambers, the stumps of a transected rat sciatic nerve were sutured into the ends of the chamber leaving a 10 mm gap between the stumps. Chambers were implanted empty (E chambers) or prefilled with saline (PF chambers). A coaxial and continuous fibrin matrix had formed in all chambers by 1 week. In E chambers, the matrices had a proximal‐distal taper that was more pronounced in E25 and E75 chambers due to significantly larger matrix diameters in the proximal region. At 3 weeks, vascular and Schwann cell migration and axonal regeneration were less advanced in the E25 and E75 than in the control E11 chambers. The retardation correlated with the presence of an avascular organization of circumferential cells. Saline prefill‐ing affected the caliber and density of fibrin fibers in the 1 week matrices of PF25 and PF75 chambers. The matrices did not have a prominent taper and diameters were progressively larger with increasing chamber volume. Saline prefilling did not affect regeneration progress in 3 week PF11 chambers but did enhance regeneration in the PF25 chambers; a 1.5‐fold larger diameter nerve formed at 3 weeks that contained 2,6‐fold more axons. Progress in the PF75 chamber was retarded. We conclude that the volume, timing, and nature of the fluid filling a silicone chamber have significant influence on the formation of fibrin matrices. Alterations in matrix formation correlate with substantial changes in the subsequent progress of intrachamber regeneration events.
Identification of stapedius muscle motoneurons in squirrel monkey and bush baby
Authors: Thompson Glenn C. , Igarashi Makoto , Stach Brad A.
Published: January 2005

The location of brainstem neurons which mediate the stapedius reflex was identified by injecting horseradish peroxidase into the stapedius muscle of squirrel monkeys and bush babies. Retrogradely labeled neurons, arranged in a one‐ to three‐cell column, were found medial to the main facial motor nucleus in squirrel monkeys and ventral to it in bush babies. Nissl, protargol, and acetylcholinesterase stains were subsequently used to identify and describe this unique column of cells. It was found that staining characteristics, as well as shape, size, and location, distinguish stapedius muscle motoneurons from closely associated cell groups. Furthermore, stapedius muscle motoneurons are morphologically similar to periolivary cells and morphologically dissimilar to cells within the facial motor nucleus.
Vibrissae tactile stimulation: (14C) 2‐deoxyglucose uptake in rat brainstem, thalamus, and cortex
Authors: Gonzalez Manuel F. , Sharp Frank R.
Published: January 2005

The right mystacial vibrissae of awake, adult rats were stroked at 4–6 times/second and brain regions which increased (14C) 2‐deoxyglucose (2DG) uptake were mapped autoradiographically. The ventral parts of the ipsilateral spinal trigeminal nuclei pars caudalis (Sp5c), pars interpolaris (Sp5i), pars oralis (Sp5o), and the principal trigeminal sensory (Pr5) nuclei were activated. The lateral part of the ipsilateral facial (VII) nucleus (the region which innervates the vibrissae muscles) was also activated possibly via excitatory, trigeminal (Sp5c, Sp5i, Sp5o, Pr5) sensory afferents.

A number of regions were activated contralateral to the sensory stimulus. Discrete patches of (14C) 2DG uptake occurred in deep layers of the superior colliculus (SCsgp). Dorsolateral and dorsomedial parts of the ventrobasal nucleus (VB), and posterior, dorsolateral parts of the reticular nucleus (R) of thalamus were activated, along with broad portions of the primary somatosensory cortex (SI) and second somatosensory cortex (SII). Though all layers of SI and SII cortex increased 2DG uptake, VB thalamic afferents to layers IV and Vc‐Vla presumably accounted for the greater activation of these cortical layers during repetitive sensory stimulation of the vibrissae (RSSV).

Activation of the above structures fits well with known anatomical data. However, the pattern of activation during RSSV was very different from that previously described during vibrissae motor cortex stimulation (VMIS). RSSV and VMIS both produced similar repetitive movements of all the mystacial vibrissae. However, only a few overlapping brain regions were activated during both RSSV and VMIS. These RSSV‐VMIS overlap zones included Sp5o; rostral Sp5i; lateral VII; SCsgp; ventrobasal‐posteromedial and ventrobasal‐ventrolateral zones in thalamus; and a rostral region of SI probably anterior to the Woolsey vibrissae barrelfield in the dysgranular somatosensory (SI) cortex. Since RSSV and VMIS would both be expected to activate vibrissae proprioceptors, we have hypothesized that vibrissae proprioceptive input was processed in part in the RSSV‐VMIS overlap zones. Convergence of motor‐sensory inputs and other types of processing could have also occurred in these overlap zones.
Development of early brainstem projections to the tail spinal cord of xenopus
Authors: Nordlander Ruth H. , Baden Sally T. , Ryba Timothy M. J.
Published: January 2005

Horseradish peroxidase (HRP) was used to determine the sequence in which axons from different brain neurons reach the tail spinal cord during embryonic and early larval development of Xenopus laevis. Brainstem cells of several classes project to the tail at these stages: mesencephalic reticulospinal neurons of the nucleus of the medial longitudinal fasciculus, a variety of other reticulospinal neurons, vestibulospinal neurons, and a group of median basal cells which may be raphe neurons. Among the reticulospinal neurons the paired Mauthner cells are the most prominent. They and caudally situated reticular neurons are the first to label with HRP applied to the tail spinal cord (stage 37). Vestibulospinal and other reticular neurons begin to label next (stage 39), followed by mesencephalic and then median basal neurons (stage 41). Except for the Mauthner cells, the number of labeled cells belonging to each neuron class increases gradually as development proceeds.
Topology of the central nucleus of the mustache bat's inferior colliculus: Correlation of single unit properties and neuronal architecture
Authors: Zook J. M. , Winer J. A. , Pollak G. D. , Bodenhamer R. D.
Published: January 2005

The central nucleus of the mustache bat's inferior colliculus was studied in Golgi, Nissl, and fiber stained preparations; the neuronal organization and cytoarchitecture were correlated with the tonotopic maps revealed by single cell recordings.

Three divisions of the central nucleus were defined by anatomical and physiological criteria: the anterolateral, medial, and dorsoposterior divisions. In horizontal sections, the anterolateral division has pronounced, semicircular fibrodendritic laminae. The dendritic fields of adjacent neurons form rostro‐caudally‐oriented laminae related to the tonotopic sequence. The neurons in the medial division are similar in size and arrangement, but here the laminar orientation follows the lateral‐to‐medial axis, with less curvature. The dorsoposterior division has many small disc‐shaped and stellate neurons and a different, somewhat less fully expressed, laminar orientation.

Each division has a unique frequency representation and tonotopic organization which conform to the pattern of dendritic orientation. In the anterolateral division, frequencies from about 10 kHz to about 59 kHz are represented, whereas the frequency representation in the medial division ranges from about 65 kHz to 110 kHz, and higher.

The dorsoposterior division has an isofrequency organization in which the best frequency is characteristic for each bat, ranging from 60 to 64 kHz and varying by only ± 300 Hz. This frequency corresponds to the dominant echo frequency of the bat's echolocation signals.

We suggest that the dorsoposterior division is a hypertrophied isofrequency lamina, with many neurocytological features comparable to the isofrequency laminae in the central nucleus of other mammals.
A qualitative and quantitative light microscopic study of the inferior olivary complex of normal, reeler, and weaver mutant mice
Authors: Blatt Gene J. , Eisenman Leonard M.
Published: January 2005

In the normal mouse (+/+; +/rl) cerebellar Purkinje cells (PCs) are aligned in a monolayer and provide the main targets for incoming olivocerebellar climbing fibers (CF). In the neurological mutants, homozygous reeler (rl/rl), homozygous weaver (wv/wv) and heterozygous weaver (wv/+), cerebellar abnormalities exist in which many PCs are either missing or displaced. Therefore, it is of interest to determine if the inferior olivary complex (IO) in these mutants is also abnormal.

This report concerns results obtained from a light microscopic study of the inferior olivary complex. Counts of IO cells revealed apparent differences in the IO in homozygous reeler when compared to normal littermates. Whereas in the normal mouse there are approximately 37,000 IO cells and clearly defined olivary subdivisions, the IO of the homozygous reeler has a 22.6% reduction in IO cells (mean = 28,770) and indistinct borders between the major olivary subdivisions. With regard to the heterozygous and homozygous weaver, surprisingly the IO morphology and cell numbers are similar to that of the wildtype mouse even though the animals have only 86% (wv/+, mean = 158,155) and 72% (wv/wv, mean = 131,882), respectively, of the normal numbers of PCs (+/+, mean = 183,857). Purkinje cell counts revealed that the midline vermal region is the most affected area in the cerebellum in wv/+ and wv/wv whereas counts in the lateral hemisphere are near normal. The PC/IO ratio in the homozygous weaver is approximately 3:1 as compared to 5:1 in the wildtype mouse. Recent electrophysiological findings in wv/wv indicate that PCs are multiply innervated by CFs. Since a transient phase of multiple innervation is normal in the immature rat, the situation in the adult homozygous weaver may represent a retention of this immature state. A factor which may play a role in this is the loss of parallel fiber (PF)‐PC synapses resulting from massive postnatal granule cell death.

An hypothesis suggesting an intrinsic PC time‐dependent mutant gene effect is presented to account for the differences in the loss of Purkinje cells between wv/wv and wv/+ and between different regions of the cerebellum.
Selective retinal reinnervation of a surgically created tectal island in goldfish. I. Light microscopic analysis
Authors: Edwards M. A. , Sharma S. C. , Murray M.
Published: January 2005

Through anatomical and physiological studies of the regenerating retinotectal projection of goldfish, we sought to determine whether the establishment of a topographic projection is attained through a refinement of an initially less precise pattern of innervation. A 1‐mm‐wide mediolateral strip of caudal tectum was removed so that a small island of tectal tissue was spared at the caudal pole, and the contralateral nerve was either crushed (TIX) or left intact (TI). The presence of regenerated axons in the ablated zone and the reinnervation of the caudal island were assessed with anterograde and retrograde labeling methods in the following postoperative intervals: early, 20–50 days; middle, 50–110 days; and late, more than 170 days. The anterograde radioautographic method revealed that the appropriate layers of the tectal island became reinnervated by optic axons during the early period. During the middle and late periods, one to several large, discrete bundles bridging the lesion zone along the surface of exposed sub‐tectal structures were readily identified both by radioautography and by anterograde or retrograde labeling following application of horseradish peroxidase to the transected optic nerve or tectal island, respectively. In contrast, the anterograde horseradish peroxidase method did not reveal axon bundles extending caudal to the half‐tectum in the absence of a tectal island. Among TIX cases, retrograde horseradish peroxidase labeling of the contralateral nasal retina was more widespread in the middle period than in the late period, a result we interpret as reflecting an improvement in topographical precision with time. The area of retinal labeling among TIX cases in the late period was similar to that following caudal tectal injection in cases with simple nerve crush, although it was still elevated above normal control values. Physiological maps indicated a focal representation of the nasal retina in the tectal island in both periods and did not reveal a transient extreme convergence of retinal input. These findings are discussed in relation to Sperry's chemoaffinity theory.
The pretectal complex of the monkey: A reinvestigation of the morphology and retinal terminations
Authors: Hutchins Bob , Weber Joseph T.
Published: January 2005

The cytoarchitecture of the pretectal complex of the squirrel monkey was examined in Nissl‐ and myelin‐stained sections in the coronal, horizontal, and sagittal plane. Five different pretectal subdivisions can be identified on the basis of their nuclear morphology. The general location and cytoarchitecture of these pretectal nuclei are similar to those described for non‐primate mammals. Thus, the nomenclature used to designate the pretectal nuclei in other species can now be applied to the squirrel monkey. According to this standard terminology, the pretectal complex of the squirrel monkey consists of the nucleus of the optic tract; the pretectal olivary nucleus; and the medial, anterior, and posterior pretectal nuclei. The pattern of retinal innervation to the pretectum was also determined by placing intraocular injections of 3H‐proline into one eye and processing the tissue according to standard autoradiographic techniques. The pattern of transported label is more dense over the contralateral nuclei than over the ipsilateral nuclei. In particular, dense transported label is observed bilaterally over the pretectal olivary nucleus and the nucleus of the optic tract with sparse label over the posterior and medial pretectal nuclei.
Callosal and prefrontal associational projecting cell populations in area 7A of the macaque monkey: A study using retrogradely transported fluorescent dyes
Authors: Andersen R. A. , Asanuma C. , Cowan W. M.
Published: January 2005

The spatial interrelationship of neurons in area 7a in the inferior parietal lobule that project through the corpus callosum to the corresponding field in the contralateral hemisphere or to the ipsilateral prefrontal cortex has been analyzed in macaque monkeys by using double‐labeling procedures with retrogradely transported fluorescent dyes. The populations of callosal and associational projecting neurons have similar laminar distributions and are topographically intermingled. Less than 1% of the neurons were double‐labeled, thus suggesting that the two populations are largely separate. Two‐dimensional reconstructions of the distribution of labeled cells made on flattened reconstructions of the inferior parietal lobule revealed that the areal distribution of the two cortico‐cortical output arrays is complex. Although each pattern of labeling showed some discontinuities in density, there was no obvious periodicity within or between the spatial distributions of the two projecting populations. It was consistently observed that the cortex of the lateral wall of the intraparietal sulcus, adjacent to area 7a, projects more heavily to the prefrontal cortex than does area 7a itself.
Corticomotoneuronal synapses in the monkey: Light microscopic localization upon motoneurons of intrinsic muscles of the hand
Authors: Lawrence D. G. , Porter R. , Redman S. J.
Published: January 2005

Some corticospinal neurons give rise to axons which terminate directly upon motoneurons, thereby establishing corticomotoneuronal connections. The location of corticomotoneuronal synapses upon motoneurons innervating intrinsic muscles of the hand in the monkey was demonstrated by the use of intra‐axonal and intracellular horseradish peroxidase (HRP). After a number of corticospinal axons originating from the “hand” area of the precentral gyrus had been injected with HRP in the lateral funiculus at C7‐C8, a number of nearby identified intrinsic hand muscle motoneurons were also injected. Connections between corticomotoneuronal fibres and motoneurons were reconstructed from longitudinal parasagittal sections treated by the cobalt‐enhanced diaminobenzidine method.

Corticospinal axons in the lateral funiculus gave rise to main collaterals which provided an extensive arborization in lamina IX, where it was predominantly longitudinal, and in the adjacent intermediate zone. En passant and single or clustered groups of terminal boutons arose from preterminal branches of these arbors. Seven light‐microscopically identified corticomotoneuronal synapses were found. They were located upon the dendrites of recipient motoneurons at 40 μm to 750 μm from the soma and ranged in size from 0.6 × 3.0 μm to 2.4 × 3.6 μm.

The results suggest that each main collateral of a corticomotoneuronal axon establishes very few synaptic contacts, and possibly only one, with the dendrites of recipient motoneurons. This small number of contacts per motoneuron is consistent with the small amplitudes of minimal and unitary corticomotoneuronal EPSPs recorded from forelimb and hand motoneurons.
Computer reconstruction of all the neurons in the optic ganglion of Daphnia magna
Authors: Sims Stephen J. , Macagno Eduardo R.
Published: January 2005

The cellular architecture of the Daphnia compound eye visual system was studied by using computer‐aided techniques. All the neurons in one half of the bilaterally symmetric optic ganglion (OG) were reconstructed in three dimensions from serial electron micrographs. The techniques employed were those developed by Levinthal and collaborators (Macagno, Levinthal, and Sobel, Ann. Rev. Biophys. Bioeng. 8:323–351, 1979). The approximately 200 neurons reconstructed were classified according to where they branch in the OG (the lamina and/or the medulla) and whether they send processes to the supraesophageal ganglion and/or across the midplane. Within each class, neurons were further characterized according to cell body location and size and location of their branching fields. Centrifugal processes from neurons with cell bodies not in the OG were also identified. These results provide the bases for a detailed examination of the synaptic connectivity of the identified neurons and for hypotheses concerning their functional roles in visually evoked behaviors.
Interhemispheric pathways of the hippocampal formation, presubiculum, and entorhinal and posterior parahippocampal cortices in the rhesus monkey: The structure and organization of the hippocampal commissures
Authors: Demeter Steven , Rosene Douglas L. , van Hoesen Gary W.
Published: January 2005

The interhemispheric pathways originating in the hippocampal formation, presubiculum, and entorhinal and posterior parahippocampal cortices and coursing through the fornix system were investigated by autoradiographic tracing in 29 rhesus monkeys (Macaca mulatta). The results revealed that crossing fibers are segregated into three contiguous systems. Aventral hippocampal commissurelies at the transition between the body and anterior columns of the fornix in the vicinity of the subfornical organ and the interventricular foramina of Monro; it is formed by axons arising in the most anterior (uncal and genual) subdivisions of the hippocampal formation. Adorsal hippocampal commissurelies inferior to the posterior end of the body of the corpus callosum; it is formed by axons arising in the presubiculum and entorhinal cortex of the anterior parahippocampal gyrus and the proisocortical and neocortical subdivisions of the posterior parahippocampal gyrus but not in the hippocampal formation. Ahippocampal decussationlies between the ventral hippocampal commissure and dorsal hippocampal commissure; it is formed by axons arising in the body of the hippocampal formation. In contrast to the fibers of the ventral hippocampal commissure and dorsal hippocampal commissure, which terminate in contralateral cortical areas, thesedecussatingfibers terminate in the contralateral septum. Thus, the ventral hippocampal commissure and dorsal hippocampal commissure of the rhesus monkey appear to be homologous to similarly designated structures in other mammals. To the extent that these observations also apply to the interhemispheric fibers of the human hippocampal formation and parahippocampal areas, their possible preservation must be considered when interpreting the effect of callosal transection on seizures and the results of “split‐brain” studies, since callosal transection may fail to sever the hippocampal commissures in their entirety.
Tectoreticular pathways in the turtle, Pseudemys scripta. I. Morphology of tectoreticular axons
Authors: Sereno Martin I.
Published: January 2005

Tectoreticular projections in turtles were examined by reconstructing from serial sections axons that were anterogradely filled with horseradish peroxidase after tectal injections. Three tectoreticular pathways each contain extensively collateralized axons. The crossed dorsal pathway (TBd) contains large and small caliber axons. After leaving the tectum, TBd axons emit collaterals into the ipsilateral profundus mesencephali rostralis and then give off a main rostral branch that bears secondary collaterals in the ipsilateral interstitial nucleus, of the medial longitudinal fasciculus and the suprapeduncular nucleus. The main trunks cross the midline and descend in the predorsal bundle, generating collaterals at regular intervals. These terminate mostly in the medial half of the reticular core from the midbrain to the caudal medulla. Axons in the uncrossed intermediate pathway also emit collaterals into a midbrain reticular nucleus (profundus mesencephali caudalis) and often have a thick rostral branch. The main caudal trunks, however, remain ipsilateral and travel in a diffuse, laterally placed tract, where each emits a long series of collaterals into the lateral half of the reticular core. The uncrossed ventral pathway (TBv) contains medium and small caliber axons. TBv axons often have collaterals within the tectum and apparently lack main rostral branches. Their caudal trunks run in the tegmental neuropile below the TBi where they collateralize less exuberantly than do TBd and TBi axons.

The morphology of axons in all three pathways suggests that projections from disjunct tectal loci converge at many rostrocaudal levels within the reticular formation. This point was examined explicitly in experiments in which two disjunct injections were placed in one tectal lobe. Intermediate pathway axons traced from the two loci initially formed two distinct bundles but then intermingled in the reticular formation.
Tectoreticular pathways in the turtle, Pseudemys scripta. II. Morphology of tectoreticular cells
Authors: Sereno Martin I. , Ulinski Philip S.
Published: January 2005

The morphology of tectoreticular neurons in turtles was examined with serial section reconstructions of neurons retrogradely filled with HRP. Six classes of tectal neurons project into the three tectobulbar pathways characterized in the preceding paper (Sereno, '85). (1) Large multipolar neurons with somata in the central gray layers, and with moderately branched dendrites sometimes spanning over a millimeter, project into the dorsal tectobulbar pathway, TBd. Their dendrites are covered with fine spicules and tend to arborize in the lower third of the superficial gray layers. (2) Medium‐sized neurons with multiple radial dendrites and somata in the central white and upper periventricular layers probably project into the ipsilateral intermediate tectobulbar pathway, TBi. Their dendrites also bear fine spicules and usually reach the tectal surface. (3) Small radial cells in the periventricular layers, and (4) small bitufted radial cells in the superficial gray project into the small caliber component of the ipsilateral ventral tectobulbar pathway, TBv(sm). (5) Medium‐sized central gray neurons with stratified dendrites, and (6) medium‐sized central gray neurons with horizontal dendrites probably project into the medium caliber component of the ventral tectobulbar pathway, TBv(med). In contrast to TBd and TBi neurons, these last four classes emit a spray of long, filamentous dendritic appendages in the central gray and have dendritic arbors near the top of the superficial gray.

The morphology of the neurons described in this and the preceding paper is briefly discussed in light of current ideas about tectally mediated sensorimotor transformations.
Rat medulla oblongata. IV. Topographical distribution of catecholaminergic neurons with quantitative three‐dimensional computer reconstruction
Authors: Kalia Madhu , Woodward Donald J. , Smith Wade K. , Fuxe Kjell
Published: January 2005

We examined serial 40 μm vibratome, immunoperoxidase‐stained sections of the medulla with tyrosine hydroxylase (TH), dopamine‐beta‐hydroxylase (DBH), and phenylethanolamine N‐methyltransferase (CPNMT) antisera followed by Nissl staining to locate catecholaminergic neurons in cytoarchitectonic regions followed by a three‐dimensional (3D) computer reconstruction of these cell groups to determine their spatial organization. Overlay drawings of low and high power photomicrographs showing cell bodies and nuclear boundaries were entered into a digital computer storage system. Every section in the series was plotted to yield an accurate representation of regional densities of cells and location of nuclei, as revealed by two‐dimensional plots of individual sections as well as three‐dimensional plots of groups of sections. Data files were scanned in a number of ways to obtain total cell counts of TH‐, DBH‐, and PNMT‐immunoreactive cells within a designated area or cell counts of only one type of immunoreactive cell. This combination of data manipulation produced the following results: (1) A1 group is a homogeneous population of noradrenergic neurons at levels caudal to the obex, and at the obex it is mixed with adrenergic cells. The dimensions of the A1 cell group are 1.3 × 2.7 mm, extending from −2.5 to +0.2. Part of this cell group lies in the lateral reticular nucleus. (2) A2 group is not purely noradrenergic as previously suspected. It is a very mixed cell group containing mainly dopaminergic neurons in the area postrema (periventricular region) and the dorsal motor nucleus of the vagus, mainly noradrenergic neurons in the medial subnucleus of the nucleus of the tractus solitarius (nTS), mainly adrenergic neurons in the dorsal strip and dorsal subnucleus of the nucleus of the tractus solitarius, and a mixture of all three catecholaminergic neurons in the other subnuclei of the nTS. The dimensions of this group are 0.4 × 3 mm extending from −2.7 to +0.3. (3) C1 group is a homogeneous population of adrenaline cells extending from +1 to +2.5 with dimensions of 1.5 × 1.5 mm and consisting of scattered neurons some of which occupy the gigantocellular reticular nucleus. (4) C2 group is a homogeneous population of adrenaline neurons extending from +1 to +3 with dimensions of 2.5 × 3 mm. Accurate visual imaging and quantitation of the spatial organization of medullary catecholaminergic neurons within the classical anatomical framework of cytoarchitecture provides an enhanced comprehension of the organization of this region of the central nervous system.
Immunocytochemical localization of choline acetyltransferase in rat cerebral cortex: A study of cholinergic neurons and synapses
Authors: Houser C. R. , Crawford G. D. , Salvaterra P. M. , Vaughn J. E.
Published: January 2005

Choline acetyltransferase (ChAT), the acetylcholine‐synthesizing enzyme and a definitive marker for cholinergic neurons, was localized immunocytochemically in the motor and somatic sensory regions of rat cerebral cortex with monoclonal antibodies. ChAT‐positive (ChAT+) varicose fibers and terminal‐like structures were distributed in a loose network throughout the cortex. Some immunoreactive cortical fibers were continuous with those in the white matter underlying the cortex, and many of these fibers presumably originated from subcortical cholinergic neurons. ChAT+ fibers appeared to be rather evenly distributed throughout all layers of the motor cortex, but a subtle laminar pattern was evident in the somatic sensory cortex, where lower concentrations of fibers in layer IV contrasted with higher concentrations in layer V. Electron microscopy demonstrated that immunoreaction product was concentrated in synaptic vesicle‐filled profiles and that many of these structures formed synaptic contacts. ChAT+ synapses were present in all cortical layers, and the majority were of the symmetric type, although a few asymmetric ones were also observed. The most common postsynaptic elements were small to medium‐sized dendritic shafts of unidentified origin. In addition, ChAT + terminals formed synaptic contacts with apical and, probably, basilar dendrites of pyramidal neurons, as well as with the somata of ChAT‐negative nonpyramidal neurons.

ChAT+ cell bodies were present throughout cortical layers II–VI, but were most concentrated in layers II–III. The somata were small in size, and the majority of ChAT + neurons were bipolar in form, displaying vertically oriented dendrites that often extended across several cortical layers. Electron microscopy confirmed the presence of immunoreaction product within the cytoplasm of small neurons and revealed that they received both symmetric and asymmetric synapses on their somata and proximal dendrites. These observations support an identification of ChAT + cells as nonpyramidal intrinsic neurons and thus indicate that there is an intrinsic source of cholinergic innervation of the rat cerebral cortex, as well as the previously described extrinsic sources.
Numbers of myelinated and unmyelinated axons in the dorsal, lateral, and ventral funiculi of the white matter of the S2 segment of cat spinal cord
Authors: Chung Kyungsoon , Sharma Jivesh , Coggeshall Richard E.
Published: January 2005

The present work determines the numbers of myelinated and unmyelinated axons in the dorsal, lateral, and ventral funiculi of the S2 segment of the cat spinal cord. The major finding is that unmyelinated axons are almost as numerous as myelinated axons in these pathways. The myelinated axons tend to be distributed uniformly, although there is a slight concentration of these fibers in the dorsal part of the lateral funiculus. By contrast, the unmyelinated fibers, although found in significant numbers in all parts of these funiculi, concentrate in the dorsal part of the lateral funiculus and in the dorsal funiculus. Of particular note are the unmyelinated fibers in the dorsal funiculus, because it is highly likely that some of these are sensory. The findings in this study will serve as a basis for experimental studies to determine the numbers, locations, and types of unmyelinated fibers in the white matter of the mammalian cord.
Possible target neurons of 5‐hydroxytryptamine fibers in the lamprey spinal cord: Immunohistochemistry combined with intracellular staining with lucifer yellow
Authors: Van Dongen Paul A. M. , Hökfelt Tomas , Grillner Sten , Verhofstad Albert A. J. , Steinbusch Harry W. M.
Published: January 2005

Intracellular recordings were made from 76 neurons belonging to various cell types in the lamprey spinal cord, and these neurons were subsequently stained with Lucifer yellow. Sections were made of spinal cords containing Lucifer‐yellow‐filled neurons, and in the same sections 5‐hydroxytrytamine (5‐HT)‐containing neurons and fibers were made visible with immunohistochemical methods. Motoneurons and lateral cells appeared to send part of their dendrites into a dense ventromedial 5‐HT plexus, and these dendrites were adjacent to 5‐HT varicosities. No or few 5‐HT varicosities have been found adjacent to cell bodies or dendrites of sensory dorsal cells, giant interneurons, and edge cells. The combined application of intracellular staining and immunohistochemistry appeared, to be suited to screen for possible transmitter‐identified contacts on morphologically identified neurons.
GABA neurons in the superficial layers of the rat dorsal cochlear nucleus: Light and electron microscopic immunocytochemistry
Authors: Mugnaini Enrico
Published: January 2005

This article is an application of light and electron microscopic immunocytochemistry to the study of the neuronal circuit of the superficial layers in the rat dorsal cochlear nucleus (DCN). An antiserum against the intrinsic marker glutamate decarboxylase (GAD) is used to identify and map axon terminals and neurons that use gamma aminobutyric acid (GABA) as a neurotransmitter. It is demonstrated that layers 1 and 2 of the DCN contain a very high density of GABAergic boutons, matched only by the granule cell domains of the ventral cochlear nucleus, especially the superficial granule cell domain. These two layers also contain much higher concentrations of GABAergic cell bodies than all other magnocellular regions of the cochlear nuclear complex. Cartwheel and stellate neurons, and probably also Golgi cells, previously characterized in Golgi and electron microscopic investigations, appear immunostained and, therefore, are presumably inhibitory. The synaptic relations between parallel fibers, the axons of granule cells, and cartwheel and stellate neurons are confirmed. The present study also supports the conclusion that stellate cells are coupled to one another by gap junctions. Also scattered in layer 1 are large, GABAergic neurons that occur with irregular frequency and presumably represent displaced Purkinje cells, previously identified with a Purkinje‐cell‐specific marker. Granule neurons and pyramidal neurons remain unstained, even after topical injection of colchicine, which enhances immunostaining of the other glutamate‐decarboxylase‐positive cells, and therefore must use transmitters different from GABA.

The possible analogies between the spiny cartwheel and the aspiny stellate cells of the DCN and the cerebellar Purkinje and stellate/basket cells are discussed in the light of data from Golgi, electon microscopy, and transmitter imunocytochemistry.