bluuebunny/crossref_metadata_2025 huggingface dataset:
The cerebellofugal projections in the brachium conjunctivum of the rat. I. The contralateral ascending pathway,
Authors: Faull R. L. M. , Carman J. B.
Published: May 2005

The cerebellofugal projections in the contralateral ascending pathway of the brachium conjunctivum (B.C.) in the rat have been investigated in 23 animals using the Fink‐Heimer technique to demonstrate the axonal degeneration resulting from complete B.C. lesions (7), partial B.C. lesions (14) and control lesions dorsal to the B.C. (2). All of the degeneration resulting from the concomitant involvement of the structures surrounding the B.C. is accounted for in terms of known fiber pathways and from the results in the control experiments.

The contralateral ascending pathway ascends rostrally from the decussation of the B.C. through the ventromedial midbrain tegmentum to the diencephalon. In the midbrain, cerebellofugal fibers terminate heavily throughout the red nucleus including the nucleus minimus, while others pass dorsolaterally and dorsomedially from the ascending tract to terminate in adjacent midbrain nuclei. The dorsolaterally directed fibers terminate in the midbrain reticular formation, the stratum griseum profundum of the superior colliculus, the anterior pretectal nucleus and the nucleus of the posterior commissure; the dorsomedially directed fibers terminate in the principal oculomotor nucleus, the nucleus of Dark‐schewitsch, interstitial nucleus of Cajal and the central gray matter. A considerable number of the cerebellofugal fibers proceed more rostrally within the prerubral field and enter the thalamus by two routes. Most follow a direct subthalamic course within field H of Forel and after contributing fibers to the zona incerta, enter the caudal pole of the ventromedial nucleus (Vm) of the thalamus to terminate throughout Vm and the ventrolateral complex (Vl). Others enter via the internal medullary lamina and terminate throughout the parafascicular and central lateral nuclei. A small number of cerebellothalamic fibers form a commissural projection to Vl on the opposite side.

The finding that the cerebellothalamic projections to the ventral nucleus are distributed throughout Vm and Vl establishes the Vm‐Vl complex as the homologue in the rat of the ventral anterior and ventral lateral nuclei in the primate thalamus.
Rapid transneuronal degeneration and death of cortical neurons following removal of the olfactory bulb in adult rats
Authors: Heimer Lennart , Kalil Ronald
Published: May 2005

Following olfactory bulb removal in young and adult rats, many neurons in the primary olfactory cortex become markedly argyrophilic in silver impregnated preparations. Although argyrophilic neurons are found scattered throughout the pyramidal and multiform cell layers, the heaviest concentration is seen in the superficial part of the pyramidal layer.

Electron microscopic analysis reveals that argyrophilic neurons are undergoing rapid degeneration. The degenerative changes are similar in all affected cells, although some cells begin to disintegrate within 24 hours following bulbectomy, whereas others are just beginning to show pathological changes at three or four days. The first clear signs of cellular degeneration occur in the cytoplasm of the perikaryon and involve swelling of mitochondria and polysome disaggregation. An increase in the electron density of the cytoplasm follows and this is accompanied by the appearance of enlarged cisternae and disruption of the nuclear membrane. Degenerative changes in the nucleus usually are detected at a slightly later stage than in the cytoplasm. Nuclear changes are characterized by the proliferation of local aggregations of condensed chromatin, and the replacement of the nucleolus with large homogenous islands of electron dense material. In advanced stages of degeneration ribosomes are increased in density and become uniformly dispersed throughout the cytoplasm. Remnants of necrotic organelles are visible only at the cellular periphery, and phagocytosis of dying neurons by astrocytes and microglia follows quickly.

Evidence from HRP‐studies indicates that cells in the olfactory cortex, which project directly to the bulb do not correspond to those which show fulminant necrosis following olfactory bulb removal. The majority of those which degenerate are located superficially, whereas the cells of origin of the centrifugal projection lie more deeply. Based on this dissociation, it is proposed that rapid cell death in the olfactory cortex is not caused by retrograde factors involving axotomy, but is due instead to transneuronal deafferentation that results from a sudden massive loss of input from the olfactory bulb.
Autoradiographic evidence for pathways from the medial preoptic area to the midbrain involved in the drinking response to angiotensin II
Authors: Swanson L. W. , Kucharczyk J. , Mogenson G. J.
Published: May 2005

The 3H‐amino acid autoradiographic method was used to localize intracerebral sites from which angiotensin II (AII) elicits drinking and to identify their efferent neural pathways. Small injections (0.02‐0.1 μl) of AII and 3H‐amino acid mixtures were injected together or separately into widespread regions of the forebrain of adult rats in normal food and water balance. From an analysis of 39 positive and negative injection sites it was concluded that the caudal half of the medial preoptic area and the adjacent rostral part of the anterior hypothalamic area are sensitive to AII. Two anatomically defined pathways arising from neurons within this region were identified. One descends through the medial forebrain bundle and appears to terminate in the lateral hypothalamic area, the ventromedial nucleus, the mammillary body, and the ventral tegmental area. The other descends through the periventricular region and posterior hypothalamic area to end in the midbrain central gray. Additional widespread connections with the amygdala, septum, habenula, and pons appear to arise in the lateral preoptic area (Swanson, '76). Combined AII‐3H‐amino acid injections centered in the subfornical organ only elicited drinking in those cases in which injected label diffused through the third ventricle to the medial preoptic area. No efferent pathways were identified in experiments in which a small injection (0.02 μl) heavily labeled cells strictly confined to the subfornical organ and there was no ventricular spread of label.
Comparison of mauthner cell size in teleosts
Authors: Zottoli Steven J.
Published: May 2005

The Mauthner cells (M‐cells) are a pair of neurons found in the medulla oblongata of most fish and amphibians. This neuron is not the same size in all teleosts. Based on the hypothesis that differences in M‐cell size might be related to fish family and possibly fish habitat, M‐cell and nuclear size were compared between fish families. In order to minimize effects of fish length on cell or nuclear size, statistical treatment of the data was made for four separate length classes. The results indicate at least three groupings by cell or nuclear size. The cell is large in fish from the Salmonidae, Catostomidae and Cyprinidae, small in the Stichaeidae, Cottidae and Pleuronectidae and absent in Batrachoididae, Lophiidae, Ogcocephalidae and Cyclopteridae. In general a correlation exists between fish that lack or have small M‐cells and a demersal habitat. Since these fish may rely on camouflage for protection against predation, the M‐cells may have altered excitability or function as compared to more active fish in which the M‐cell is known to function in initiating the startle response (larval zebrafish and goldfish). Differences in input to M‐cells of different sizes in conjunction with known electrophysiological properties of the goldfish M‐cell are discussed in relation to the function of this neuron.
A documentation of an age related increase in neuronal and axonal numbers in the stingray, Dasyatis sabina, leseuer
Authors: Leonard Robert B. , Coggeshall Richard E. , Willis William D.
Published: May 2005

The present study documents that in the stingray Dasyatis sabina the numbers of (1) dorsal root ganglion cells, (2) dorsal root axons, (3) ventral root axons and (4) “motor” cells in the ventral horn increase steadily as the animals increase in size. This increase in axonal and neuronal numbers persists much further into adult life than is the case for other vertebrates that have been studied from this point of view. We hypothesize this steady increase in axonal numbers may be related to the ability of fish to regenerate parts of their central and/or peripheral nervous systems.
The organization of monoamine neurons within the brainstem of the north american opossum (didelphis virginiana)
Authors: Crutcher Keith A. , Humbertson Albert O.
Published: May 2005

The distribution of monoamine‐containing neurons within the brain of the opossum is described using the Falck‐Hillarp histofluorescence technique. Catecholamine‐containing neurons are organized into four groups. The medulla contains one group which is located dorsolateral to the lateral reticular nucleus and ventrolateral to the dorsal vagal nucleus. The second collection is found within the pons and includes both the locus coeruleus and a region continuous with it referred to as the nucleus coeruleus, pars α. The third aggregate includes the substantia nigra, the ventral tegmental area, and the mesencephalic reticular formation and a fourth group is located within the periventricular and dorsal paraventricular nuclei of the hypothalamus. The indoleamine‐containing cell bodies are distributed within the nuclei raphe obscurus, pallidus, magnus, dorsalis, and the nuclei linearis and superior centralis except at certain pontine levels where they appear laterally within the reticular formation. A number of small intensely fluorescent (SIF) cells are present within the connective tissue surrounding the brain and its blood vessels as well. Although certain differences are present, the didtribution of monoamine neurons in the American opossum conforms generally to that described for the placental mammals studied to date.
Ocular dominance columns and their development in layer IV of the cat's visual cortex: A quantitative study
Authors: Levay Simon , Stryker Michael P. , Shatz Carla J.
Published: May 2005

The distribution of geniculocortical afferents serving the left and right eyes was studied in abult cats and in kittens of various ages. Methods used were autoradiography of transneuronally transported 3H‐proline injected into one eye, and physiological recordings.

In the adult cat, patches of label in layer IV corresponding to ocular dominance columns were seen both ipsilateral and contralateral to the injected eye. Between the patches, however, grain density was substantially above background, especially on the contralateral side. Similarly, in the contralateral lateral geniculate nucleus (LGN) there was substantial labelling of neuronal cell bodies in lamina A1, which receives no innervation from the injected eye. Such spillover of radioactivity into the inappropriate laminae of the LGN was measured in autoradiographs of semithin sections, and its effect on the cortical labelling pattern calculated. Spillover appeared to account quantitatively for the labelling seen between patches in the cortex. It was concluded that the geniculocortical afferents for the ipsilateral and contralateral eyes are equally and almost completely segregated from each other at the centers of columns, although there is extensive overlap at the borders. This pattern is consistent with the physiological pattern of ocular dominance in layer IV.

In kittens studied at one to two weeks of age, radioactive label formed a continuous band in layer IV on both sides of the brain. On the ipsilateral side, this appearance could not be accounted for by spillover in the LGN, but reflected a continuous, non‐columnar distribution of afferents. Physiological recordings at this age showed most cells in layer IV to be nearly equally responsive to stimulation of either eye, in contrast to the adult pattern. Periodic variations in grain density were first noted at three weeks, and a pattern similar to that of the adult was reached by about six weeks of age. On the contralateral side the uniform labelling pattern seen in the 1‐ to 2‐week‐old kittens was uninterpretable, owing to the very great spillover of radioactivity in the contralateral LGN, but the physiology suggested that the contralateral afferents, too, were uniformly distributed in layer IV.

The results suggest that the earliest functional connections formed by geniculocortical afferents have a uniform, non‐columnar arrangement in layer IV, and that the formation of the adult pattern is likely to involve the breakage and reformation of synaptic connections. This process appears to be similar to that described for the monkey (Hubel et al., '77; Rakic, '76), except that the beginning of segregation is postponed until postnatal life.
The trigeminal system in the pigeon (Columba livia) I. Projections of the Gasserian ganglion
Authors: Dubbeldam Jacob L. , Karten Harvey J.
Published: May 2005

The central projection of the Gasserian ganglion were investigated in the pigeon, Columba livia. Lesions were placed in the ganglion either by direct surgical exposure or stereotaxically, and following survival times of one to four days, the brains stained with the Fink‐Heimer method. The main group of central axons bifurcate to from distinct ascending and descending branches, the tractus trigemini ascendens (TTA) and the tractus trigemini descendens (TTD). A smaller lateral tract also courses caudally (lTTD) separate of TTD proper to terminate in the nucleus cuneatus externus.

The TTA projects topographically upon the principal sensory nucleus of the trigeminus, ending in both the pars dorsalis and a smaller pars ventralis. The neurons at the point of bifurcation of the entering radix have been designated as the pars oralis of nTTD. The TTD distributes caudally to several distinct subnuclei at each level, and extends into the cervical spinal cord. Relatively discrete regions corresponding to the pars interpolaris and caudalis were recognized.

The projections to the cervical cord terminate in laminae I‐IV.

There was no evidence of projections to the cerebellum, or contralateral PrV or TTD. There was a small projection to the contralateral cervical spinal cord. No clear evidence of a projection to the nucleus solitarius was found.

The distribution of primary trigeminal axons is compared to that described in other vertebrates.
An autoradiographic study of the projection of visual cortical area 1 to the thalamus, pretectum and superior colliculus of the rabbit
Authors: Giolli R. A. , Towns L. C. , Takahashi T. T. , Karamanlidis A. N. , Williams D. D.
Published: May 2005

The projections of visual cortical area 1 (vl) to the thalamus, pretectum and superior colliculus of the rabbit have been studied by Giolli and Guthrie (1967, 1971) using the Nauta and Fink‐Heimer methods to determine the course and distribution of degenerating nerve fibers. The present study represents a reinvestigation of these same projections utilizing the tracing method of autoradiography.

An injection of 3H leucine was produced within a small region of vl in each of 18 adult albino rabbits, and the brains were subsequently processed for autoradiography by the method of Cowan et al. (1972). The results have confirmed the observations of Giolli and Guthrie (1967, 71) (1) By showing that vl of the rabbit projects to the thalamic reticular nucleus, the ventral lateral geniculate nucleus, the dorsal lateral geniculate nucleus; the pulvinar, the anterior and posterior pretectal nuclei and the superior colliculus and (2) by showing that a particular retinotopic organization is present in each of these projections. However, unlike Giolli and Guthrie (1967, 1971), the present autoradiographic study has further revealed (1) that both the ventrolateral and the posterior thalamic nuclei receive inputs from vl and (2) that the nucleus of the optic tract is not innervated by axons originating from vl.
The number and distribution of ganglion cells in the cat's retina
Authors: Stone Jonathan
Published: May 2005

The number of ganglion cells in the cat's retina, and the pattern of their distribution over the retina, have been reinvestigated. Criteria are presented for the identification of ganglion cells in Nissl‐stained whole mounts, most particularly for the distinction between small ganglion cells and neurological cells, by reference to retinas with no ganglion cells (obtained by nerve section) and to areas of retina containing a population of only small ganglion cells was counted in four retinas (mean total 116,250). The number of large or “giant” cells (presumably the somas of Y‐cells and of α‐cells ) varied from 4,200 to 7,100. Overall these cells comprised 4.0‐6.3% of the total ganglion cell population. Their distribution over the retina showed a concentration around the area centralis, with a localized minimum density at the area centralis, and a concentration in the visual streak. These concentrations of large cells were quantitatively less than the concentrations of smaller cells in the area centralis and visual streak, so that the relative frequency of large cells was minimal (mean 1.6%) at the area centralis and increased steadily up to 5.5‐6.9% in peripheral retina. Their relative frequency was distinctly lower along the visual streak that in peripheral retina above or below the streak.
The nasotemporal division of retina in the siamese cat
Authors: Stone Jonathan , Campion Joyce E. , Leicester Jonathan
Published: May 2005

By sectioning one optic tract in Siamese kittens and allowing sufficient time for the affected ganglion cells to degenerate and disappear, we have obtained maps of the distribution of ipsi‐ and contralaterally projecting ganglion cells in the Siamese cat. As previous work predicted, many ganglion cells in the Siamese cat retina project contralaterally which, in the normally pigmented cat, would project ipsilaterally. The transition from the pattern of projection typical of nasal retina (all contralateral) to that typical of temporal retina (most ipsilateral) is much more gradual in the Siamese cat than in the normally pigmented cat, and is centred 1.7‐3 mm temporal to the area centralis, instead of at the area centralis. In the Siamese cat only a few ganglion cells at the area centralis project ipsilaterally, as against nearly 50% level 1.7‐30 mm into temporal retina, and overall the zone of transition may be several millimetres wide, as against about 0.2‐0.5 mm in the normally pigmented cat. Evidence is presented that the degree of the abnormality of nasotemporal division varies between individual Siamese cats and that the abnormality is more severe among large or “giant” cells than among the population as a whole.
Intracortical connectivity of architectonic fields in the somatic sensory, motor and parietal cortex of monkeys
Authors: Jones E. G. , Coulter J. D. , Hendry S. H. C.
Published: May 2005

Anterograde and retrograde transport methods were used to study the corticocortical connectivity of areas 3a, 3b, 1, 2, 5, 4 and 6 of the monkey cerebral cortex. Fields were identified by cytoarchitectonic features and by thalamic connectivity in the same brains. Area 3a was identified by first recording a short latency group I afferent evoked potential. Attempts were made to analyze the data in terms of: (1) routes whereby somatic sensory input might influence the performance of motor cortex neurons; (2) possible multiple representations of the body surface in the component fields of the first somatic sensory area (SI).

Apart from vertical interlaminar connections, two types of intracortical connectivity are recognized. The first, regarded as “non‐specific,” consists of axons spreading out in layers I, III and V‐VI from all sides of an injection of isotope; these cross architectonic borders indiscrimininately. They are not unique to the regions studied. The second is formed by axons entering the white matter and re‐entering other fields. In these, they terminate in layers I‐IV in one or more mediolaterally oriented strips of fairly constant width (0.5–;1 mm) and separated by gaps of comparable size. Though there is a broadly systematic topography in these projections, the strips are probably best regarded as representing some feature other than receptive field position. Separate representations are nevertheless implied in area 3b, in areas 1 and 2 (together), in areas 3a and 4 (together) and in area 5; with, in each case, the representations of the digits pointed at the central sulcus.

Area 3b is not connected with areas 3a or 4, but projects to a combined areas 1 and 2. Area 1 is reciprocally connected with area 3a and area 2 reciprocally with area 4. The connectivity of area 3a, as conventionally identified, is such that it is probably best regarded not as an entity, but as a part of area 4. Areas identified by others as area 3a should probably be regraded as parts of area 3b. Parts of area 5 that should be more properly considered as area 2, and other parts that receive thalamic input not from the ventrobasal complex but from the lateral nuclear complex and anterior pulvinar, are also interconnected with area 4. More posterior parts of area 5 are connected with laterally placed parts of area 6. A more medial part of area 6, the supplementary motor area, occupies a pivotal position in the sensory‐motor cortex, for it receives fibers from areas 3a, 4, 1, 2 and 5 (all parts), and projects back to areas 3a, 4 and 5.
The islands of calleja: Organization and connections
Authors: Fallon James H. , Riley Joseph N. , Sipe Jack C. , Moore Robert Y.
Published: May 2005

The islands of Calleja (IC) in the rat are composed of seven small groups of granule cells in the polymorph layer of the olfactory tubercle and one large group, the insula magna, which lies along the border between septum, nucleus accumbens and nucleus of the diagonal band. The cytoarchitecture and neuronal morphology of the IC and surrounding cells, studied using Nisslstained and Golgi‐Kopsch material, are described. In addition, the afferent and efferent connections of the IC were analyzed using fluorescence histochemistry, the autoradiographic tracing method, and the anterograde and retrograde horseradish peroxidase methods. Topographically organized projections to the IC from the dopamine‐containing cells of the substantia nigra‐ventral tegmental area are demonstrated by the glyoxylic acid fluorescence histochemical method and the autoradiographic tracing technique. Anterograde and retrograde horseradish peroxidase studies provide evidence for reciprocal, topographically organized interconnections between the IC and the septum, nucleus accumbens, amygdala and piriform cortex. These observations indicate that the IC constitute a unique population of granule cells, located in the olfactory tubercle, innervated by dopamine neurons of the mesencephalon and interconnected with olfactory and non‐olfactory components of the basal forebrain.
Connections of striate cortex in the prosimian, galago senegalensis
Authors: Symonds Laura L. , Kaas Jon H.
Published: May 2005

Efferent and afferent connections of primary visual cortex, Area 17, were determined in a prosimian, Galago senegalensis, by autoradiographic methods after injections of 3H‐proline or 3H‐HRP. The cortical connections of Area 17 with Areas 18 and MT were homotopic and reciprocal. Projections from Area 17 terminated largely in layer IV and somewhat in layer III of both Areas 18 and MT. Most of the cells projecting to Area 17 were located in layer V of Area 18 and layer VI of MT. Subcortical projections included the reticular nucleus of the thalamus, where columns of label corresponding to injection sites were found in the caudal forth of the nucleus. Projections to the lateral geniculate nucleus were along lines of isorepresentation and were in register with the cells projecting back to the injection site. The parvocellular layers were less densely labeled than other layers by the transport of 3H‐proline, while concentrations of label were noted on the dorsal and ventral margins of the nucleus and in interlaminar regions between the internal parvocellular and magnocellular layers and between the two magnocellular layers. The pattern of terminations in the pulvinar complex suggested functional subdivisions. We have divided the inferior pulvinar into a large central nucleus, IPc, with topologically organized input from Area 17; a smaller medial nucleus, IPm, with a second pattern of input from Area 17; and a dorso‐posterior nucleus, IPp, without input from striate cortex. The superior pulvinar likewise appears to have several subdivisions. One of these, a “central” nucleus of the superior pulvinar, SPc, receives topologically organized projections from Area 17. SPc is about the same size as IPc and is organized as a mirror image of IPc. Thus, both IPc and SPc represent the lower visual quadrant medially and the upper visual quadrant laterally; central vision is represented along the common border for both nuclei, while peripheral vision is represented dorsorostrally in SPc and ventrocaudally in IPc. Finally, the superficial grey of the superior colliculus receives topologically organized input form Area 17.
Studies of the cat's medial interlaminar nucleus: A subdivision of the dorsal lateral geniculate nucleus
Authors: Kratz Kenneth E. , Webb Sarah V. , Murray Sherman S.
Published: May 2005

The medial interlaminar nucleus (MIN) of the cat lies medial to the laminated region of the dorsal lateral geniculate (lamLGN). This latter region includes the A and C laminae. As does lamLGN, MIN receives direct retinal input and projects to various visual cortical areas. We examined the MIN of 15 normal adult cats with electrophysiological and anatomical techniques.

Autoradiographs processed from cats that had one eye injected with tritiated fucose and proline indicate that MIN is composed of at least two laminae, one for each eye. The area which receives input from the ipsilateral eye is a small central region surrounded dorsally, medially, and ventrally by a larger crescent shaped region that receives input from the contralateral eye. This pattern was also evident from electrophysiological recording experiments.

Extracellular recordings from 102 single‐units in MIN indicate that these cells have properties essentially identical to lamLGN Y‐cells. That is, they had short latencies to orthodromic stimulation of the optic chiasm and antidromic stimulation of the visual cortices, responded in a phasic manner to the presentation of a standing contrast within the receptive field center, responded to rapidly moving visual stimuli, and showed non‐linear spatial summation properties typical of lamLGN Y‐cells. We discovered two difference between MIN cells and lamLGN Y‐cells. First the mean receptive field center size of MIN cells is considerably larger than that of lamLGN Y‐cells, and second, MIN cells do not have the non‐dominant eye inhibitory receptive fields found for many lamLGN Y‐cells.

Cell size measurements indicate that while the mean cell size in MIN is approximately 30% greater than in the A laminae of lamLGN, the distribution of MIN cell sizes extends over the full range of cell sizes in the A laminae. Since the A laminae are comprised mostly of X‐ and Y‐cells, this suggests that, although Y‐cells on average are larger than X‐cells, considerable overlap exists in their size distribution. No differences between the ipsilateral and contra lateral terminal zones were found on any measure.

Since MIN cells share most or all the fundamental features of lamLGN Y‐cells, we suggest that these cell groups should be considered subpopulations of a more general group of geniculate Y‐cells. Accordingly, we refer to these two subpopulations as lamLGN Y‐cells and MIN Y‐cells.
Chemical and morphological studies on garfish peripheral nerves
Authors: Hofteig John H. , Mendell Jerry R. , Yates Allan J.
Published: May 2005

Gangliosides were extracted, separated by thin layer chromatography, and quantitated in three cranial nerves of the garfish (Lepisosteus osseus): the completely unmyelinated olfactory nerve (OLF), and two nerves composed of both myelinated and unmyelinated fibers, viz., the main trunk of the maxillary nerve (MAX) and a branch of the maxillary nerve (BR‐MAX). Morphological studies on each of these nerves were done to verify that the OLF had been excised free of any contamination from the accompanying myelinated BR‐MAX, to aid in the interpretation of the biochemical findings, and to clarify the nature of the OLF supporting cell.

The chief chemical findings were (1) documentation of the presence of gangliosides in nerves previously thought not to contain them, (2) demonstration that gangliosides can be associated with unmyelinated nerves, (3) demonstration of a greater proportion of one simple ganglioside (G‐6) in the OLF but greater proportions of two complex gangliosides (G‐2 and G‐O) in the MAX and BR‐MAX, and (4) that either GM4 or a variant of the GM3 is present in OLF. The morphological findings with respect to the difficulty of ascribing only peripheral nervous system characteristics to the OLF supporting cell are discussed in relation to the ganglioside band chromatographing slightly ahead of GM4 in the OLF.
3H‐Thymidine autoradiographic analysis of telencephalic histogenesis in the chick embryo: I. Neuronal birthdates of telencephalic compartments in situ
Authors: Tsai Huei Mei , Garber Beatrice B. , Larramendi Luis M. H.
Published: May 2005

The birthdates of neuronal populations comprising the chick telencephalon were determined by 3H‐thymidine labeling and were mapped with respect to their terminal positions in the 16‐day embryo. Essentially all neurons were generated between four and nine days of embryonic development. Each telencephalic structure (based on terminology used by Karten and Hodos, '67) was characterized by a specific range of birthdates: some regions such as the core of the ectostriatum or the paleostriatum primitivum, were generated within a single day, while others, such as the hyperstriatum accessorium, required up to five days for generation of the complete population. Spatial‐temporal gradients of neuronal birthdates, lateromedial and ventrodorsal, were seen in the telencephalon as a whole and within individual subcompartments as well. An “outside‐in” pattern of histogenesis predominated throughout the entire telencephalon, including the dorsolateral cortex. However, notable exceptions pertaining to the paleostriatum augmentatum, hyperstriatum intercalatus and field “L” were observed. Glial cells, generated for the most part after day ten, were found to be distributed homogeneously throughout all areas of the telencephalon. These data provide the first birthdating data for an avian telencephalon and bring greater resolution to previous analyses of the histogenesis of this brain region. Further, the compartmentalization of the proliferative neuroepithelium is revealed by these data, and the possibility of a common time of origin in the neuroepithelium for neurons of related function is discussed.
The immunocytochemical localization of enkephalin in the central nervous system of the rat
Authors: Finley James C. W. , Maderdrut Jerome L. , Petrusz Peter
Published: May 2005

The immunocytochemical localization of enkephalin‐like immunoreactivity (ELI) throughout the rat central nervous system (CNS) was investigated. The detection of ELI‐containing structures was facilitated through the use of (1) brains from colchicine‐treated rats, (2) the proteolytic pretreatment of sections with pronase and (3) the “double‐bridge” staining technique. Our findings confirm the presence of ELI in perikarya, neuronal processes and terminals in many areas of the CNS. In addition, the localization of ELI‐containing perikarya is reported for the first time in the following areas: the olfactory bulb, the olfactory tubercle, the lateral preoptic nucleus, several nuclei within the amygdaloid nuclear complex, the hippocampus, the neocortex, the cingulate cortex, the posterior mammillary nucleus, the medial nucleus of the optic tract, the brachium of the inferior colliculus, the ventral tegmental nucleus, the locus ceruleus, the subceruleal region, the lateral trapezoid nucleus, the nucleus reticularis lateralis, and lamina VII of the cervical spinal cord. Our results demonstrate ELI in neurons which are heterogeneous in size, some probably functioning as interneurons and others as projection neurons in different areas of the CNS. The location of these neurons within the brain suggests that these pentapeptides serve diverse functions which include, in addition to nociception, the regulation of neuroendocrine, respiratory, auditory, vestibular, and olfactory functions.
An atlas of α‐bungarotoxin binding sites and structures containing acetylcholinesterase in the mouse central nervous system
Authors: Arimatsu Yasuyoshi , Seto Akiko , Amano Takehiko
Published: May 2005

Alpha‐bungarotoxin (α‐BGT) has been established as a specific ligand for peripheral nicotinic acetylcholine receptors (nAChRs). To demonstrate the distribution of possible nAChRs in the mouse central nervous system, detailed maps of α‐BGT binding sites were made by light microscopic autoradiography. Cryostat sections fixed with 4% paraformaldehyde were incubated with [125I]α‐BGT and were processed for autoradiographic visualization of bound radioactivity. Systematic observations of the autoradiographs revealed extensive but uneven distributions of α‐BGT binding sites throughout the brain and spinal cord. The highest level of toxin binding occurred in the nucleus (nuc.) dorsalis tegmenti (von Gudden) as well as in the nuc. subthalamicus, nuc. amygdaloideus medialis posterior, nuc. centrum medianum‐parafascicularis thalami, nuc. interpeduncularis pars lateralis, nuc. parabigeminalis, colliculus posterior, and nuc. dorsalis nervi vagi. The distribution patterns of acetylcholinesterase (AChE) activity were also mapped histochemically and were correlated to those of α‐BGT binding sites. Most of the regions with significant levels of α‐BGT binding also showed significant staining reaction of AChE.
Developmental alterations in binocular competitive interactions and visual acuity in visually deprived cats
Authors: Smith Douglas C.
Published: May 2005

The purpose of the present study was to determine the effects of developmental alterations in binocular competitive interactions between the eyes on visual acuity. Comparisons were made between animals which were monocularly deprived (MD) of patterned visual input, binocularly lid‐sutured cats (BD), and animals which had the lids of one eye sutured closed and the other eye removed prior to natural eye opening (MDE). Thus, each group differed in the degree of competitive imbalance between the eyes during postnatal development. Threshold visual acuity for high contrast, squarewave gratings was measured in a jumping stand. Mean visual acuities for each group using a single deprived eye were: group MD, 0.64 cycles/deg; group BD, 3.2 cycles/deg; group MDE, 3.72 cycyles/deg. These results indicate that the greater the competitive disadvantage an eye is placed at during development, the greater the acuity (sensory) deficits. Further, comparisons made between MD and MDE animals indicated that the acuity deficits using the deprived eye in MD cats are much more a result of competition than of the effects of deprivation per se.
Regional distribution of substance P‐like immunoreactivity in the frog brain and spinal cord: Immunohistochemical analysis
Authors: Inagaki Shinobu , Senba Emiko , Shiosaka Sadao , Takagi Hiroshi , Kawai Yuriko , Takatsuki Kenichi , Sakanaka Masahiro , Matsuzaki Takashi , Tohyama Masaya
Published: May 2005

With the indirect immunofluorescence technique of Coons, the overall distribution of the substance P (SP)‐positive neuron system in the frog brain and spinal cord was explored. SP‐positive cells were observed in more than ten areas, such as olfactory bulb, amygdaloid complex, septal area, bed nucleus of hippocampal commissure, hypothalamic periventricular zone, dorsal and ventral thalamus, infundibulum, torus semicircularis, optic tectum, the area dorsal to the interpeduncular nucleus, central gray matter of the mesorhombencephalon, and raphe region, etc. A dense network of SP‐positive fibers was also widely distributed in the frog brain and spinal cord. SP‐positive fibers were roughly divided into two types. One consisted of very fine SP‐positive fibers and gave the region a diffuse appearance. The area medial to n. Bellonci, interpeduncular nucleus, n. isthmi, and optic tectum contained this type of SP‐positive fibers. The other one consisted of clearly distinguishable varicose fibers. A number of SP‐positive fibers located in the amygdaloid complex, striatal complex, hypothalamus, central gray matter of the mesorhombencephalon, trigeminal spinal nucleus, and posterior horn of the spinal cord belonged to this category. The functional role of the SP‐positive neuron system in the central nervous system is also briefly discussed.
Expansion of the ipsilateral retinal projection in the frog brain during optic nerve regeneration: Sequence of reinnervation and retinotopic organization
Authors: Stelzner Dennis J. , Bohn Ronald C. , Strauss Judith A.
Published: May 2005

The sequential reinnervation and distribution of optics axons in diencephalic and mesencephalic targets was studied after crushing the optic nerve in 37 adult Rana pipiens. Following intravitreal injection of 3H‐proline at various times after nerve crush the distribution of regenerating optic axons was traced using autoradiographic methods. The maximal distribution of regenerating axons was reached between 6 and 8 weeks after optic nerve crush. On the contralateral side of the brain, the distribution of fibers was similar to the normal projection. Ipsilaterally, silver grain density was greater than normal in the optic tract and projections were expanded to all optic targets on this side of the brain. These abnormal projections were sustained for a least 6 months after nerve crush.

The sequence of reinnervation of targets on both sides of the brain differed from normal development. Unlike development, regenerating optic axons were found in the ipsilateral optic tract prior to the time they were found on the contralateral side of the brain. Also unlike development, regenerating axons did not begin to reinnervate targets in the anterior thalamus until several weeks after reinnervation of the posterior thalamus and tectum had begun. The expanded distribution of regenerating axons within optic targets on the ipsilateral side of the brain became evident at the time optic axons first invaded each area.

Most optic axons appeared to regenerate from the point of nerve crush. The retinal stump of the crushed nerve was filled with labeled axons in all six frogs given intravitreal 3H‐proline injections between 1 and 7 days after nerve crush. In addition, using a modified Fink‐Heimer method, few degenerating axons were found in the retinal stump of four frogs sacrificed between 2 and 8 days after optic nerve crush.

In ten frogs studied between 3 and 6 months after nerve crush, horseradish peroxidase (HRP) was placed on different portions of the tectum ipsilateral to the crush. In each case HRP was retrogradely transported to ganglion cells in both retinae. The cells labeled in the ipsilateral retina corresponded in position to the same region of the contralateral retina although many fewer cells were labeled ipsilaterally. Cutting the optic tract on the side opposite the HRP placement did not affect the results. No ganglion cells were labeled in the ipsilateral retina of two frogs not receiving optic nerve crush.

These results show that axons from all parts of the retina regenerate to the ipsilateral side of the brain during optic nerve regeneration and the distribution of these misrouted axons, at least to the tectum, overlaps the intact distribution from the other eye. Differences between development and regeneration in the patterns of growth of optic axons may be related to this anomaly.
Projections from the pontine nuclei proper and reticular tegmental nucleus onto the cerebellar cortex in the cat. An autoradiographic study
Authors: Kawamura Koki , Hashikawa Tsutomu
Published: May 2005

After injections of 0.5 μI of tritiated leucine and/or proline into various parts of the pontine nuclei proper or the pontine tegmental reticular nucleus (N.r.t.) of 34 cats, labeled terminals of pontocerebellar fibers were found in the cerebellar cortex.

Fibers from the pontine nuclei and N.r.t. terminate as mossy fibers in the granular layer of the cerebellum, and no evidence is obtained of labeled fibers in the molecular layer. The pontocerebellar projection is, in general, bilateral with a contralateral preponderance, and a complex organization has been shown to exist in the cat.

Clear evidence of divergence of this projection from a small pontine area has been demonstrated. Thus, the dorsolateral nucleus has a heavy projection to lobule VII, besides modest projections to lobules VI, VIII, and IX, crus I and II, paraflocculus, and paramedian lobule. On the other hand, a particular cerebellar region receives afferent fibers from several pontine regions, confirming previous HRP studies. For example, lobule VII receives heavy projections from parts of the dorsolateral, peduncular, and paramedian nuclei, less heavy projections from the lateral part of the lateral nucleus, and some from other parts of the pontine nuclei. This is a convergent feature of the pontocerebellar projections.

In addition, small adjoining areas within a pontine subdivision have different patterns of cerebellar projections, showing preferential sites of terminations. This suggests some degree of localization within the pontine nuclei. The cerebellar projection from the N.r.t. shows an essentially similar organization as the projection from the pontine nuclei proper, an apparent difference being only that the former is more extensive in the fields of termination than the latter.

Some evidence for a parasagittal termination of pontocerebellar projections to the paramedian lobule has been found in this study. However, this is not as clear‐cut as such patterns in the cerebellar projections from the spinal cord, cuneate nucleus, and lateral reticular nucleus shown recently in rat and cat.
The phrenic nucleus of the albino rat: A correlative HRP and Golgi study
Authors: Goshgarian Harry G. , Rafols José A.
Published: May 2005

The phrenic nucleus of the adult albino rat was studied by utilizing the O‐dianisidine method for the retrograde transport of horseradish peroxidase in conjunction with the zinc chromate modification of the Golgi technique. Application of HRP to the transected phrenic nerve in the neck labeled a column of phrenic motor neurons from C3 to C5 in the ipsilateral spinal cord. However, when HRP was applied to the phrenic nerve intrathoracically, labeled neurons were found from C3 to C6. The long axis of the column of phrenic neurons was oriented tangentially from rostral to caudal poles. There was a gradual shift of the column from posterior to anterior and from lateral to medial positions in the ventral horn. The peroxidase material was also used to localize impregnated phrenic motor neurons in the Golgi sections and to provide quantitative data on phrenic motor neurons. In Golgi‐impregnated material two types of phrenic neurons were distinguished on the basis of dendritic morphology and orientation. These neurons were designated (1) larger neurons with smooth, radially oriented dendrites, and (2) smaller neurons with varicose, tangentially oriented dendrites. Both types of neurons had a small number of spines and bulbous appendages issuing from the dendritic trunks and branches. The dendritic fields of adjacent phrenic neurons overlapped extensively with one another and with dendrites of more distally placed ventral horn motor neurons. In peroxidase‐labeled sagittal sections the dendrites of phrenic neurons were primarily oriented in the rostrocaudal plane. The mean total number of peroxidase‐labeled neurons in the phrenic nucleus was 415.75 ± 18.36 cells. In sagittal sections the mean long axis diameter of phrenic cell bodies was 34.5 μm. In frontal sections the mean long axis diameter of phrenic cell bodies was 22.5 μm. Thus, from direct measurement, the phrenic neurons were 34% longer in the sagittal plane than in the frontal plane. In the present study each phrenic nucleus contributed fibers only to the ipsilateral phrenic nerve, and no evidence for peripheral crossing of fibers was found.
Embryonic and postembryonic morphogenesis of a grasshopper interneuron
Authors: Bentley David , Toroian‐Raymond Alma
Published: May 2005

The object of this study was to describe the embryonic and postembryonic morphogenesis of a grasshopper interneuron in order to determine how, and when, this cell comes to assume its mature form. DCMD is an intensively investigated interneuron whose morphology, input and output physiology, and role in behavior are relatively well‐known in the adult. We examined the morphology of DCMD in the brain at each stage of its development with silver‐intesified cobalt‐fills. It arises at 40 ± 4% of embryogenesis and is probably one of the early progeny from its stem cell. In the ensuing 40% of development, its brain arborization grows quite directly into its mature form. Branches appear first and are always longest and densest in the brain region where the adult arborization is found. Thus, the adult form arises by initially directed growth and not by secondary selection of branches from a diffuse or overgrown arborization. Restricted secondary branch loss of lateral filopodia and probably of a few early branches does occur.

Embryonic and postembryonic development of the cell are distinctly different. Embryogenesis is the period of morphological differentiation as indicated by the growth and shaping of the brain and also thoracic (axonal) arborizations, the appearance of cytological specializations, and the logarithmic growth of the neurite and soma. The brain arborization has its mature form, although not size, by the completion of embryogenesis. Postembryonic development is a period of substantial, but primarily allometric, growth. The soma and neurite grow linearly (with time), and the arborization grows in proportion to brain size.
Ruffed cell: A new type of neuron with a distinctive initial unmyelinated portion of the axon in the olfactory bulb of the goldfish (Carassius auratus). III. Three‐dimensional structure of the ruffed cell dendrite
Authors: Kosaka Toshio , Hama Kiyoshi
Published: May 2005

The three‐dimensional structure of the ruffed cell dendrite in the olfactory bulb of the goldfish (Carassius auratus) was studied by means of light and high‐voltage electron microscopy of Golgi‐impregnated material, combined Golgi‐electron microscopy, and electron microscopy of serial thin sections.

Ruffed cell dendrites ramify in the glomerular area with tufted branching patterns. They give rise to many appendages of various shapes and sizes: sheetlike processes, fingerlike projections, or small tuftlike appendages. These appendages, singly or together, appear to entwine or cover other neuronal processes. In thin sections ruffed cell dendritic appendages frequently look like glial processes; that is, they appear to conform in shape to the contours of surrounding neuronal elements, such as mitral and granule cell dendrites.

Ruffed cell dendrites display intimate relationships with mitral cell dendrites. The former appear to coil around and cover the latter. Notwithstanding the intimate relationship between ruffed cell dendrites and mitral cell dendrites, there seem to be no synaptic connection between them. Ruffed cell dendrites bear a rather small number of presynaptic and postsynaptic sites, most of which are with granule cell dendrites. Ruffed cell dendrites seem to receive no synapses from olfactory nerve terminals.