bluuebunny/crossref_metadata_2025 huggingface dataset:
The cerebellum of the bullfrog tadpole (Rana catesbeiana)
Authors: Uray Nandor J. , Gona Amos G.
Published: January 2005

The cerebellum of the premetamorphic bullfrog tadpole differs from the cerebellum of other frog species in its morphology and maturational state. The cell mass beneath the floor of the lateral recess and bordering its lateral wall that has been reported to form the auricular lobe in other species is absent, the auricular lobe abutting the medial wall of the lateral recess instead and is continuous with the corpus cerebelli. The corpus cerebelli, although immature and yet to acquire an external granular layer, is already massive and displays an incipient molecular, Purkinje cell and granular layers.

Cytodifferentiation in the auricular lobe and corpus cerebelli is similar, their constituent cells being in various stages of development. Fully mature cells are absent, but a small population of Purkinje cells and glia in the auricular lobe and along the marginal zone of the corpus cerebelli show advanced development. The orientation of these Purkinje cells is parallel to the pia and appears to approximate the course of the vestibulo‐lateral commissural fibers. In the ventral part of the corpus cerebelli, developing climbing fibers are present but Purkinje cells are poorly developed.
The role of superior colliculus in vision: Visual form discrimination in cats with superior colliculus ablations
Authors: Tunkl J. E. , Berkley M. A.
Published: January 2005

The rate of acquisition of visual form discriminations in cats with superior colliculus damage was measured in a testing apparatus requiring a minimal amount of stimulus localization in space. In animals with bilateral superior colliculus ablations, acquisition was impaired relative to acquisition in normal animals. In these animals, the extent of the lesion was related to the severity of the deficit. In split‐brain preparations with unilateral superior colliculus ablations, acquisition with the eye ipsilateral to the lesion was impaired relative to acquisition with eye contralateral to the lesion. The deficits observed did not depend upon damage to pretectum. The results support the conclusion that the superior colliculus participates in certain aspects of form vision.
Abnormal development of the suprachiasmatic nuclei of the hypothalamus in a strain of genetically anophthalmic mice
Authors: Silver Jerry
Published: January 2005

In the anophthalmic mutant of the mouse the optic primordia are “genetically enucleated” well before the usual emergence of retinal ganglion cell axons (Silver and Hughes, '74). In eyeless animals, a portion of the mediobasal hypothalamus and one of its constituent nuclear pairs, nucleus suprachiasmaticus (SCN), were markedly abnormal in the embryo and adult. It has been reported that the ventral portion of the SCN receives a substantial, direct retinal innervation (Moore and Lenn, '72) and that these nuclei may mediate several light‐induced hormonal and behavioral circadian rhythms (Stetson and Whitmyre, '76). During day 13 of mutant embryogenesis, just prior to the time of optic chiasm formation in normal animals, a large portion of ependyma and adjacent brain tissue herniated into the lumen of the would‐be suprachiasmatic region of the third ventricle. In 70% of the animals examined histologically during the latter phase of development and as adults, regulation occurred and the brains were largely comparable with those of controls. However, in the remaining mutant mice, the overall size of either, or sometimes both, SCN was much reduced. The basal (but not the apical) dendrited of SCN neurons failed to develop fully. Some basal dendrites normally invade the optic chiasm below. In several mutant animals one or the other SCN had greatly increased numbers of cells, while the contralateral one had diminished numbers. These observations suggest that regular formation of the suprachiasmatic region of the hypothalamus and especially the suprachiasmatic nuclei, may depend during development upon the presence of the eye or the subjacent optic axons.
Autoradiographic maps of regional brain glucose consumption in resting, awake rats using [14c] 2‐deoxyglucose
Authors: Schwartz William J. , Sharp Frank R.
Published: January 2005

The 2‐deoxy‐D‐[14C]‐glucose (2‐DG) autoradiographic method for determining regional brain glucose consumption has been applied successfully by a number of workers for mapping the alterations of brain glucose consumption which occur in association with experimental alterations of brain functional activity. This paper provides a framework for the interpretation of these and further studies by presenting: (1) the pattern of regional brain glucose consumption in the normal, resting, awake rat; (2) the anatomical identities of brain structures which on autoradiographs appear only as regional variations of optical density. For this purpose, a series of 2‐DG autoradiographs of coronal brain sections from an injected animal is compared with adjacent labeled Nissl sections.
Postnatal formation of non‐neuronal cells in the rat occipital cerebrum: An autoradiographic study of the time and space pattern of cell division
Authors: Mareš Vladislav , Brückner Gert
Published: January 2005

Rats of the BD III strain were injected with3H‐thymidine (5 μCi per g b. wt.) at postnatal day (PD) 1,3,7,12,16 and 21 and were killed at PD 22‐27 and 27 respectively. The number of cells synthesizing DNA in the visual cortex (areas 17, 18 and 18a) was detected by light microscope autoradiography. It was found that proliferation of non‐Neuronal cells of bothecto‐ (i.e., astrocytes and oligodendrocytes) andmeso‐dermalorigin (endothelial cells, microglia, pericytes, etc.) increases postnatally, reaching a peak at PD 3‐7. After a transient fall of the proliferation rate towards PD 12, another peak in the number of labeled cells was found at PD 16. In ectodermally derived glial cells the latter was evident in the deep cortical layers and the subcortical white matter; in mesodermally derived groups of cells the second peak was clearly evident in all gray matter layers as well as in the adjacent white matter.

Another group of animals aged 1,3,7,12,16 and 21 days was injected with3H‐thymidine (5 μCi per g b. wt.) and the animals were killed two hours after the injection. It was shown that towards PD 3‐7 proliferation, of non‐neuronal cells increased in all layers of the hemispheric wall, including leptomeninges. At PD 16 the increase in cell division involved only germinative cells of the periventricular layer. Factors responsible for the cyclic course of proliferation of nonneuronal cells and its relationship to the process of tissue differentiation are not clear. Increased rate of formation ofectodermallyderived glial cells can be related to the (a) intensified growth of surface of nerve cells and vessels – since both must be encased in glial cells – and (b) to the formation of myelin. Changes in the production of non‐neuronal cells ofmesodermalorigin reflect most probably changes in the rate of vasculogenesis because of the high prevalence of endothelial cells in this cell group.
The projection of the opossum's visual field on the cerebral cortex
Authors: Sousa Aglai P. B. , Gattass R. , Oswaldo‐Cruz E.
Published: January 2005

The visual cortex of the opossum was studied by means of evoked potential and multi‐unit recordings, and a map of the visual field in VI was constructed: Evoked responses were observed in regions extending beyond the boundaries of striate cortex. Different patterns of response were obtained depending on the cortical region undergoing exploration: in a posteromedial region, coincident with striate area, complex waveforms were obtained, contrasting with the simpler forms observed in a region localized anterolaterally. VI, which corresponds to cytoarchitectonic area 17, has a topography of projections similar to that found in other mammals: the upper visual field represented posteriorly, the temporal field represented medially, the lower field represented anteriorly and the nasal part laterally. A large proportion of VI is devoted to the region of binocular representation, which covers approximately100° at the level of the horizontal meridian. The cortical representation of the vertical meridian extends to approximately 60°above and below the center of gaze, suggesting that the cortical representation of the visual field is more restricted than the visual field available to the contralateral hemiretina. Our results suggest that the extreme periphery of the field is not represented in VI. In its lateral border the projection does not end at the vertical meridian, it extends 5° into the ipsilateral hemififield of vision, so that approximately 10° of visual field is represented in both hemispheres. There is a reversal of representation along the lateral border of VI, in a region which coincides with the cytoarchitectonic boundaries of striate and peristriate areas, suggesting the existence of at least a second representation of the visual field in the neocortex of the opossum, corresponding to VII of other animals.

The magnification factor in VI varied from 7°/mm observed at the cortical representation of the center of gaze, to 30°/mm at the extreme periphery of the field, along the horizontal meridian. A comparable decrease was also observed along the vertical meridian, towards the upper and lower limits of the visual field.
Spinal projection to the dorsolateral nucleus of the caudal basilar pons in the cat
Authors: Rüegg D. G. , Eldred E. , Wiesendanger M.
Published: January 2005

In the cat, a spinal projection to a restricted area of the basilar pontine grey has been revealed with use of an anterograde degeneration technique (Fink‐Heimer). The area was ipsilateral to the spinal lesion, restricted to the far caudal limit of the pons, and included the dorsal and the dorsolateral subdivisions of the pontine nuclei (PN). Comparisons following high cervical, midthoracic and upper lumbar spinal lesions did not reveal any somatotopic organization. Only a few spinopontine fibers had origins below segmental level L4. Lesions of various quadrants of the cord indicated that the spinopontine fibers ascendede through the dorsolateral funiculus, and not through either the dorsal or the verntal funiculi. Comparison with the degeneration effects of cerebral cortical lesions showed that the spinal projection from the first sensorimotor and second somatosensory cortices. In the rat no comparable spinopontine projection was found.

It is suggested that the spinopontine pathway migh forward information to the cerebellum from visceral sensory receptors or perhaps from pools of spinal interneurons.
The retinal origins of the optic nerve conduction latency groups in the brush‐tailed possum, Trichosurus vulpecula
Authors: Freeman Brian
Published: January 2005

The antidromic compound action potential recorded near the centre of the possum optic disc, following stimulation of the optic chiasm, has four negative peaks corresponding to the optic nerve conduction latency groups t1, t2, t3 and t4. The t2 peak is reduced in the compound action potential recorded from the nasal margin of the optic disc but is prominent on the opposite side at the superior temporal margin. The t4 peak may be absent in this vicinity.

The frequency distributions of the diameters of intraretinal ganglion cell axons at the nasal margin and at the superior temporal margin of the optic disc are bimodal. Neither of these size distributions can be directly correlated with the multipeaked antidromic compound action potentials recorded at these same sites. However, by considering the frequency distribution difference between these sites, it is possible to infer (i) that the optic nerve t2 group may be represented intraretinally on the temporal side by a population of medium sized axons with a modal diameter of 0.8 μm and (ii) that the t4 group may be represented intraretinally on the nasal side by a population of small axons with modal diameter 0.3 μm.

In addition, a correlation of axon sizes with previously reported regional variations in the sizes of ganglion cell somas suggests that the optic nerve t4 conduction latency group may arise from small ganglion cells in the nasal streak and nasal peripheral retina and that the t2 group may arise from medium sized cells in the temporal area centralis.
Growth pattern of axons in the optic nerve of chick during myelogenesis
Authors: Arees Edward A.
Published: January 2005

The purpose of this experiment was to study the diameter of axons at the time of the initiation of myelin and the pattern of growth of axons in the optic nerve of the chick. Embryos between 15 and 20 days and chicks 3, 5, 22 and 60 days of age were studied on the electron microscopic level.

Based on axon diameter a unimodal distribution of unmyelinated axons is present through day 20 of incubation with a mean of approximately 0.35 μ. This population is represented through 22 days of age but from day 3 on, a second distinct population of unmyelinated axons is present which has a mean diameter that is approximately twice that of the smaller unmyelinated axons. All axons do not increase simultaneously in diameter but once growth starts, the unmyelinated axons apparently double in diameter at a relatively rapid rate prior to myelination.

On incubation day 17 less than 1% of the axons in the optic nerve is myelinated. The number of axons in this group and their diameter (mean approximately 1.2 μ) remain relatively constant through day 3 but from days 5 through 22, two distinct populations of myelinated axons are present with mean diameters of 0.51 μ, 1.76 μ, and 3.90 μ. These populations represent approximately 20%, 67%, and 13% respectively of the total fiber population.

As age increases the diameter of some myelinated axons is as small as or smaller than the unmyelinated axons at an earlier period in development. This suggests that factors other than axon diameter might be involved in the start of myelination. It appears that the increase in axon diameter does not occur in a continuous manner but in a saltatory manner from one size to another.
Synaptic organization of the dopaminergic neurons in the rabbit retina
Authors: Dowling John E. , Ehinger Berndt
Published: January 2005

A number of substances were tested for their ability to label amine‐accumulating neurons in the rabbit retina after fixation with OsO4 or glutaraldehyde and OsO4. Useful results were obtained with 5,6‐dihydroxytryptamine (5,6‐DHT) and 6‐hydroxydopamine (6‐HDA). Labelled processes were characterized by small (40–50 mm) pleomorphic synaptic vesicles containing electron‐dense cores, and at times by swelling of mitochondria and by increased electron density of membranes and cytoplasm. Fluorescence microscopy showed that 5,6‐DHT labelled both dopaminergic and indoleamine‐accumulating neurons. In most experiments, therefore, the indoleamine‐accumulating neurons were removed with 5,7‐dihydroxytryptamine. In such retinas the dopaminergic processes labelled by 5,6‐DHT were found to make synapses of the conventional type, characterized by an accumulation of synaptic vesicles on the presumed presynaptic side and some aggregation of material on the cytoplasmic side of the synaptic membranes and within the synaptic cleft. The dopaminergic processes were found to contact each other and also non‐dopaminergic amacrine cells and their processes. Conventional synapses onto dopaminergic processes were observed from both labelled and unlabelled amacrine processes. The input from labelled neurons was observed on varicose dopaminergic processes whereas input from non‐labelled elements was found on the intervaricose parts of the dopaminergic processes. No Contacts of dopaminergic processes with bipolar or ganglion cells were observed. Injections of 6‐HDA gave the same results, although this drug gave less distinct labelling which made the observations less decisive than with 5,6‐DHT. In retinas treated with 5,6‐DHT alone (i.e., in which the indoleamine‐accumulating neurons remained) numerous processes were observed which were both pre‐ and postsynaptic to bipolar terminals. These observations suggest that the indoleamine‐accumulating processes synapse with bipolar cells.

The results show that the dopaminergic neurons form a network involving only amacrine cells, suggesting a regulatory function for them. By analogy with the dopaminergic interplexiform cells of the goldfish retina, it is suggested that the dopaminergic neurons in the rabbit may regulate lateral inhibitory effects mediated by amacrine cells. Furthermore, the finding that the dopaminergic and indoleamine‐accumulating cells apparently have a different synaptic organization suggests that it is appropriate to categorize amacrine cells according to their transmitter content as well as their morphology.
Histochemical, pharmacological and microspectrofluorometric analysis of new sites of serotonin localization in the rat hypothalamus
Authors: Kent Daniel L. , Sladek John R.
Published: January 2005

Histopharmacological and microspectrofluorometric analysis was applied to the rat hypothalamus for the identification of serotonin. Neuronal perikarya, especially certain of those of the endocrinologically important arcuate nucleus, were seen to contain a yellow histofluorescence which possessed spectral characteristics consistent with the serotonin fluorophor. Serotonin was localized also within vericosities of various hypothalamic nuclei, as well as within an ependymally associated network of fibers. Pharmacological administration of the serotoninprecursor, tryptophan, resulted in the identification of serotonin histofluorescence and spectra within hypothalamic neurons, yielding evidence that these neurons possess the capacity to synthesize serotonin. These newly described cells may be of importance to the regulation of hypothalamically mediated endocrine function due to their neuroanatomical placement in the medial basal hypothalamus.
Projections to the inferior olive of the cat I. Comparisons of input from the dorsal column nuclei, the lateral cervical nucleus, the spino‐olivary pathways, the cerebral cortex and the cerebellum
Authors: Berkley K. J. , Worden I. G.
Published: January 2005

The present experiments compare the projections from the dorsal column nuclei (DCN), the lateral cervical nucleus (LCN), the spino‐olivary pathways (SO), the motor cortex (Ms1) and the cerebellum (CB) to the inferior olive of the cat. A differential labeling strategy was used for these comparisons.

It was found that projections from the contralateral DCN and LCN and the ipsilateral SO overlap extensively with each other in the dorsal accessory division of the inferior olive and the caudal half of the medial accessory olive. Projections from the contralateral motor cortex partially overlap these somato‐sen‐sory projections but they also extend into the principal division and into the rostral half of the medial accessory olive where other authors have found input from other “motor” sources such as the red n., the globus pallidus and the caudate n. The contralateral cerebellum projects heavily to most of the inferior olive except for a few regions in the caudal portions of the two accessory nuclei.

These results show that there is a partial segregation between somatosensory and motor inputs within the inferior olive and that the cerebellar feedback fibers appear to avoid at least parts of those regions where the somatosensory input is heavy. Some of this segregation, particularly within the medial accessory olive and the principal n., correlates with differences in both the olivo‐cerebellar connectivity and the cytoarchitecture of these regions.

Although the somatosensory and motor inputs are partially segregated, there are also several regions where these inputs overlap. These regions are: (1) an area in the medial half of the rostral portions of the dorsal accessory olive, and (2) a small oval zone in the middle of the caudal half of the medial accessory olive. This overlap provides an anatomical basis for electrophysiological evidence which demonstrates the existence of cells in some of these regions that respond to activation of both the cerebral cortex and the spinal cord (e.g., Crill and Kennedy, 1967).
The DNA content of Purkinje cells in mammals
Authors: Mann D. M. A. , Yates P. O. , Barton C. M.
Published: January 2005

Nerve cells have generally been assumed to have a diploid DNA content, typical of non‐dividing somatic cells. However several reports have suggested that certain never cell types, notably Purkinje cells of the cerebellum, are polyploid. Other studies have contradicted these findings, stating Purkinje cells to be diploid. In this paper we reinvestigate the DNA status of Purkinje cells, in a variety of mammalian species. Cell DNA content is measured on tissue smears by Feulgen microspectrophotometry. Results show that for all species examined by us, Purkinje cells, have, without exception, a DNA content comparable to that of somatic cells. A critical appraisal of the techniques used in those studies claiming a tetraploid DNA content for Purkinje cells leads us to believe our findings to a correct.
Light microscopic analysis of the kitten retina: Postnatal development in the area centralis
Authors: Tucker Gail Susan
Published: January 2005

A method was devised for morphological localization of the area centralis, and the timecourse of its formation as a structural entity was established. Postnatal differentiation of the retina proceeds as follows: the irregularly laminated ganglion cell layer of the newborn becomes unilaminar everywhere but in the presumptive area centralis, a difference which is first discernible at five to six days of age; the outer nuclear layer is always of the same thickness in the area centralis, while in the periphery the layer thins with time; the outer nuclear layer is always thinner in the area centralis than in the periphery; inner nuclear layer thickness is invariant early in postnatal life, but in the adult it is thicker in the area centralis than in the near temporal periphery; plexiform layers from by two weeks of age and reach adult thickness thereafter.

Retinal ganglion cells were measured and the percent distributions of three ganglion cell size classes (6–10 μm; 11–20 μm; 21–35 μm) were determined for the area centralis and near temporal periphery. Mean ganglion cell size is constant in center and periphery through five weeks of age, is adultlike in the periphery soon thereafter and in the center sometime after eight weeks of age. The percent distribution of ganglion cells by size class in center and periphery is not adultlike even at eight weeks of age. The implications of these observations and others are discussed relative to postnatal growth of the eye and placement of the area centralis in the retinal field and optic axis. The involvement of retinal cell proliferation, cell growth, ganglion cell dendrite formation and cell shape changes in the expansion of the retina are also discussed.
Cerebellar cortical efferent fibers of the paraflocculus of tree shrew (Tupaia glis)
Authors: Haines D. E. , Whitworth R. H.
Published: January 2005

Efferent projections from the paraflocculus of the tree shrew (Tupaia glis) were studied utilizing the Fink and Heimer ('67) method. Cerebellar corticonuclear fibers of both dorsal (Dpf) and ventral (Vpf) divisions of the paraflocculus terminate in the lateral cerebellar nucleus (NL) and in the posterior interposed nucleus (NIP). These fibers are ipsilateral, topographically organized and arranged into at least two dozens.

Following injury to either the Dpf or Vpf. degenerated axons are found in lateral and caudal regions of the NIP respectively. Consequently, these two portions of the paraflocculus have relatively exclusive terminal fields with overlap only at the periphery. Preterminal debris is seen in basically similar areas of the NL (caudolateral, caudal, ventral) after damage to either the Dpf or Vpf. This observation leads to the conclusion that the terminal fields for these areas of paraflocculur cortex are largely coextensive in the NL.

In addition to the topographical representation of the Dpf and Vpf in both the NL and NIP, there is evidence that these corticonuclear fibers are also organized into the general zonal pattern hypothesized by Voogd ('69). Persistent and numerous degenerated axons from both the Dpf and Vpf end in lateral and caudal NIP, respectively, corroborating the presence of a relatively wide zone C2 in both divisions of the paraflocculus. The Dpf and Vpf also project into the NL to a terminal field that appears to consist of two portions. One part located in caudal, ventral and/or caudoventral areas of the NL and a second at slightly more rostral and rostrolateral areas. The presence of a cortical region which is affiliated with two areas of the NL substantiates not only the existence of zone D in the paraflocculus, but gives experimental evidence that it may consist of two parts as previously suggested (Voogd, '69). From the Dpf many fibers enter the NL while few are seen in this nucleus after damage to the Vpf. This suggests that zone D is wider in the Dpf and narrower in the Vpf.

The results of this study do not support previous suggestions that the paraflocculus projects to either only the NL or to most of, or all of, the ipsilateral cerebellar nuclei. No projections to any contralateral cerebellar nuclei are seen. There is also no conclusive proof that the parafloccular cortex of Tupaia projects into the vestibular complex or to any other brainstem relay nuclei.
The synaptic terminations of certain midrain‐olivary fibers in the opossum
Authors: King James S. , Hamos James E. , Maley Bruce E.
Published: January 2005

The nuclear origin and distribution of midbrain‐olivary fibers has been described in a previous study utilizing axonal transport techniques (Linauts and Martin, '78a). The present report extends their results to the electron microscopic level and details the postsynaptic distribution of such fibers. Lesions within the ventral periaqueductal grey and adjacent tegmentum, the red nucleus or the nucleus subparafascicularis result in electron dense axon terminals within the olive at survival times of 48, 72 and 96 hours. At 72 hours, many degenerating presynaptic profiles shrink, become irregular in shape and are totally or partially surrounded by glial processes. The principal olivary nucleus contains the majority of these profiles. However, the subparafascicular terminals are more abundant in the rostral and intermediate parts of the medial accessory nucleus and the rubral terminals are concentrated within the dorsal lamella of the principal nucleus. The nuclear location of the degenerating terminals was determined by examination of 1 μm plastic sections cut in the transverse plane from each block face prior to thin sectioning. Degenerating terminals were counted in three cases, one from each of the three lesion sites described above. When taken together these cases show that just over 50% of the degnerating terminals are presynaptic to spiny appendages and are located within the synaptic clusters (glomeruli) described previously (King, '76). The percentage of degenerating terminals in the glomeruli increases to 70% when the lesion is in the ventral periaqueductal grey and adjacent tegmentum. The remaining degenerating terminals contact dendritic shafts outside the astrocytic boundaries of the synaptic clusters.

The synaptic vesicle populations within the degenerating terminals vary with the location of the lesion. Lesions in the ventral periaqueductal grey and the adjacent tegmentum result in the degeneration of terminals with either clear spherical vesicles or endings with both clear spherical vesicles and a variable number of large dense core vesicles. In contrast, the primary degenerative changes that occur after destruction of the red nucleus or the nucleus sub‐parafascicularis are in terminals with clear spherical vesicles. When the synaptic complex was present in the plane of section, regardless of the site of the lesion, the degenerating terminals could be classified as Gray's type I.

Thus, we have demonstrated that afferents from the mesencephalon terminate within synaptic clusters located in the principal and medial accessory (Part A) subnuclei of the inferior olive. Although the mesencephalic afferents have multiple origins (Linauts and Martin, '78a), many of their synaptic terminals contact spiny appendages within the synaptic clusters. This postsynaptic site also receives cerebellar terminals (King et al., '76). The origin of presynaptic profiles within the synaptic clusters that contain clear pleomorphlic vesicles is yet to be determined.
Experimental studies on the ultrastructural localization of acetylcholinesterase in the mediobasal hypothalamus of the rat
Authors: Carson Keith A. , Nemeroff Charles B. , Rone Michael S. , Nicholson Gayle F. , Kizer John S. , Hanker Jacob S.
Published: January 2005

Acetylcholinesterase (AChE) activity has been demonstrated ultra structurally in neurons of the arcuate nucleus and associated with fibers in the arcuate nucleus and the median eminence (ME) of the rat. In addition, the effects of neonatal monosodium glutamate (MSG) treatment and Halász deafferentation on the AChE staining and localization have been studied. Neonatal MSG‐treatment resulted in loss of the majority of AchE‐positive neurons in the arcuate nucleus while leaving neuropil staining intact. Haläsz deafferentation caused a loss of arcuate neuropil activity while leaving the neuronal staining unaltered. These observations are consistent with previous biochemical results suggesting the existence of a cholinergic tuberoinfundibular system with nerve cells in the arcuate nucleus and terminals in the median eminence. In addition, the deafferentation experiments indicated that extra‐hypothalamic cholinergic fibers may innervate the arcuate nucleus. Supporting evidence from other biochemical studies and the curious paucity of histochemical and biochemical AChE activity in the ME are also discussed.
GABA‐ergic pathways in the goldfish retina
Authors: Marc Robert E. , Stell William K. , Bok Dean , Lam Dominic M. K.
Published: January 2005

A high‐affinity uptake mechanism for [3H]‐γ‐aminobutyric acid (GABA) has been localized to type H1 cone horizontal cells and type Ab pyriform amacrine cells in the retina of the goldfish by light and electron microscope autoradiography. By stimulating isololated retinas with colored lights during incubation we have been able to use [3H]‐GABA uptake as a probe of light‐evoked changes in membrane potential. All colors of lights increase and darkness decreases [3H]‐GABA uptake by H1 cone horizontal cells. Our model of voltage dependence of GABA uptake predicts that all colors of light should hyperpolarize H1 cone horizontal cells and other investigators have shown by intracellular recording and dye‐marking that type H1 cone horizontal cells hyperpolarize to all wavelengths of light. We have also obtained evidence that dark‐induced depolarizatiion of cone horizontal cells leads to release of GABA. Type Ab pyriform amacrine cells show maximal [3H]‐GABA uptake in darkness and when exposed to green or blue lights, but red lights dramatically suppress uptake. We predict these neurons to be red‐depolarizing and recent intracellular recordings and dye‐marking by Famiglietti et al. ('77) support our conclusions. Synaptic relations of apparently GABA‐ergic neurons were investigated in the electron microscope. We propose type H1 cone horizontal cells to be both pre‐ and post‐synaptic to red‐sensitive cones and type Ab pyriform amacrine cells to be both pre‐ and post‐synaptic to red‐sensitive center‐depolarizing bipolar cells.
Development of distinct cell types in the feline red nucleus: A golgi‐cox and electron microscopic study
Authors: Sadun Alfredo A. , Pappas George D.
Published: January 2005

The feline RN contains neurons which fall into three size categories: giant (40–80 μm), medium (25–35 μm) and small (6–20 μm). These three populations of rubral neurons are distinguishable on the basis of a number of ultrastructural criteria and form classes not dissimilar from the traditional three divisions of cell types. Each of the three populations of rubral neurons can be further divided into three subgroups on the basis of a large number of configurational criteria discernible by the Golgi‐Cox method. Each of these nine cell types are clearly separate, distinguishable by at least three criteria, and are found in different regions of the RN.

It is shown that in 5‐day prenatal kitten, rubral neurons are already organized into the aforementioned three size categories. At this age most of the subpopulations are also distinguishable by the Golgi‐Cox method. However, the giant rubral neurons (about 30 μm) and the medium sized cells (about 20 μm) are much smaller than in the adult cat. The dendrites elaborate many fine processes which emerge from multiple varicosities. The neuropil differs strikingly from that of the adult in that the vast majority of axons are small and unmyelinated.

A number of changes in the RN are apparent as the kitten matures. The larger rubral cells undergo configurational changes before the smaller neurons, yet the giant cells continue to grow for a longer period of time. In the perinatal period, the extent of arborization of the dendritic trees diminishes, the number of spines decreases, and the long dendritic spines shorten. Somatic spines first appear in the giant cells at about one week after birth. In prenatal kittens, large cells frequently elaborate a tuft of fine branching processes in one region of the soma. These tufts later diminish in size and disappear by one week post‐natal.

Recent investigations (Pompeianao, '59; Condé, '66; King et al., '73; Sadun, '75) indicates that the RN of the cat is highly organized and very heterogenous. Afferent terminals are restricted to certain regions of certain cell types which are themselves specifically located within the RN. This specificity is apparent in perinatal kittens, despite the manifest immature appearance of the RN.
The medial geniculate body of the tree shrew, Tupaia glis I. Cytoarchitecture and midbrain connections
Authors: Oliver Douglas L. , Hall William C.
Published: January 2005

In this study of the medial geniculate body in the tree shrew eight subdivisions are identified on the basis of differences recognized in Nissl‐stained material. Experiments using the methods of anterograde and retrograde axonal transport and anterograde degeneration show that each subdivision has a unique pattern of connections with the midbrain.

The ventral division of the medial geniculate body contains at least two subdivisions, the ventral nucleus and the caudomarginal nucleus. The ventral nucleus is characterized by densely‐packed cells and receives topographically organized projections from the central nucleus of the inferior colliculus. The caudomarginal nucleus, on the other hand, receives its major midbrain projections from the medial nucleus in the inferior colliculus.

In the dorsal division four subdivisions are distinguished. The suprageniculate nucleus contains large, loosely‐packed cells and receives projections from the deep layers of the superior colliculus and from the midbrain tegmentum. The dorsal nucleus receives projections from the midbrain tegmentum. The deep dorsal and anterodorsal nuclei have neurons which resemble those in the dorsal nucleus. Both receive projections from the roof nucleus of the inferior colliculus but the deep dorsal nucleus receives an additional projection from the parabrachial tegmentum.

The medial division has a rostral and a caudal subdivision. The ascending projections to the rostral nucleus are from the lateral zone in the inferior colliculus and from the spinal cord. The caudal nucleus contains cells with large somas and receives projections from most of the midbrain areas which project to the other subdivisions of the medial geniculate body.
The medial geniculate body of the tree shrew, Tupaia glis II. Connections with the neocortex
Authors: Oliver Douglas L. , Hall William C.
Published: January 2005

In this study the temporal cortex of the tree shrew was subdivided on the basis of cytoarchitectonic criteria, and the connections of each subdivision with the thalamus and midbrain were analyzed with retrograde and anterograde techniques.

The results indicate that, with one exception, each subdivision of the medial geniculate body projects to a separate cortical area. The primary auditory cortex receives projections from the ventral nucleus. Surrounding the primary cortex are at least five additional cytoarchitectonically distinct areas which receive projections from the remaining medial geniculate subdivisions. The evidence suggests that there is very little overlap in the projections from each of these geniculate subdivisions. An exception is the projection of the caudal nucleus of the medial division. This subdivision apparently projects to most, if not all, of the cortical target of the medial geniculate body. Although the cortical projections of the caudal nucleus overlap those of the other medial geniculate subdivisions, the laminar distribution of its terminationsin cortex is different. The caudal nucleus projects primarily to layer VI whereas the other subdivisions of the medial geniculate body project primarily to layer IV and the adjacent part of layer III.

Anterograde techniques were also used to study the projections from the cortex back to the thalamus and to the midbrain. The projections to the thalamus precisely reciprocate the thalamocortical connections. The projections to the midbrain are to the same areas which the preceding study (Oliver and Hall, '78) showed give rise to ascending projections to the medial geniculate body. An exception is the central nucleus of the inferior colliculus which apparently does not receive a projection from the temporal cortex.
Isogenic grasshoppers: Genetic variability in the morphology of identified neurons
Authors: Goodman Corey S.
Published: January 2005

Although identified neurons are defined as constant and unique from animal to animal within the same species, we might expect to find phenotypic variablity in the number, morphology, and physiology of identified neurons if we examined them in enough sexually reproduced animals of the same species. Morphological variability and axonal abnormalities were previously encountered in a study of the large ocellar interneurons in 50 grasshoppers.

Both the somata and arborizations in the brain of the ocellar interneurons from one or more ocelli can be stained easily and repeatedly with cobalt, so that one can routinely examine the morephology of large numbers of cells in large numbers of animals.

In the present study, the large ocellar interneurons were examined in three types of animals: (i) animals from two different breeding poplulations and their offspring, (ii) the offspring within clutches from single mated pairs of known phenotypes, and (iii) isogenic animals from the parthenogenetic clones of single unmated females. The soma location, axonal pathway, location of arborizations, and fine branching patterns of 14 of the large ocellar interneurons were examined in 430 grasshoppers.

The large ocellar interneurons were examined in 11 clones raised in nearly constant and identical conditions. In most of the clones, the morphology of interneurons L5L and L5R was normal; all of the 82 animals examined from clones 4, 7, 9, 10, 12, 13, 16, and 17 were normal. Clones 8 and 2 had high percentages of animals with axonal abnormalities of interneuron L5: 16 out of 24 animals (66%) in clone 8 and 37 out of 42 animals (88%) in clone 2. All of the ocellar interneurons except for L5 were normal in all of these animals.

Thus, the abnormal development of at least one identified interneuron, L5, can occur with a high degree of genetic control and a high degree of specificity. The axonal abnormality of interneuron L5 was not the same in each of the 37 animals from clone, 2, although common mistakes and patterns were detected.
The identification of relay neurons in the dorsal lateral geniculate nucleus of monkeys using horseradish peroxidase
Authors: Norden J. J. , Kaas J. H.
Published: January 2005

Intraaxonal retrograde transport of the protein horseradish peroxidase (HRP) was used to identify relay neurons in the dorsal lateral geniculate nucleus (LGN) of owl (Aotus trivirgatus) and rhesus (Macaca mulatta) monkeys. In both species, from 94.1–98.6% of the neurons within columns extending through both parvocellular and magnocellular layers were labeled following injection of HRP into striate cortex. Labeled neurons were also identified in the thin ventral‐most S(0) Layers. Although most of the cells within the thin interlaminar regions in the LGN of both species were labeled following injections of HRP, many unlabeled neurons were identified within the large cell‐rich interlaminar region (IL) between the internal parvocellular and internal magnocellular layers in the LGN of the owl monkey, suggesting that IL may be a specialized containing a large number of intrinsic neurons. Finally, measurement of the cell diameters of neurons within the densely labeled areas in relay layers revealed that labeled and unlabeled neurons could not be distinguished on the basis of cell body size alone and that some of the smallest cells of the LGN project to striate cortex. These findings indicate that nearly all of the neurons of the main relay layers of the LGN in these two primates are relay cells and that the organization of the LGN in primates may differ significantly from that of other mammals with respect to the percentage of interneurons.
Proliferative and degenerative events in the early development of chick dorsal root ganglia. I. Normal development
Authors: McMillan Carr Virginia , Simpson Sidney B.
Published: January 2005

Development of the chick dorsal root ganglia was examined in 4.5‐ to 9.5‐day embryos. Tritiated thymidine (3H ‐ TdR) and autoradiography was used to analyze proliferative activity and the Feulgen procedure to analyze degenerative activity in ganglia 12–17. Proliferative activity was found to be elevated through 4.5 days of incubation when as many as 14% of the ganglionic cells become labelled following a one‐hour exposure to 3H‐ TdR. By 6.5 to 7.5 days proliferative activity decreased to 2–4% in the lateroventral (LV) regions and to approximately 1% in the mediodorsal (MD) regions of the ganglia. However there appears to be increased proliferative activity by the end of the experimental period at 9.5 days. Birthdate studies demonstrate that large‐scale neuronal production occurs between 4.5 and 6.5 days in LV regions and between 4.5 and 7.5 days in the MD regions. After those times ganglionic proliferative activity must be largely nonneuronal in nature. This nonneuronal proliferation is greater in LV than in MD regions and in brachial than in nonbrachial ganglia.

Degenerative activity was found to be absent from the ganglia until after 4.5 days of incubation. It then increases rapidly, and by 5.5 days 5% of the LV cells in nonbrachial ganglia are degenerating. Degenerative activity then declines but is still present at 9.5 days. In contrast to results of an earlier study (Hamburger and Levi‐Montalcini, '49), degenerative activity was also found in the LV region of brachial ganglia and the MD regions of brachial and nonbrachial ganglia. The pattern of LV degenerative activity in brachial ganglia is similar to that in nonbrachial activity increases throughout the experimental period, and by 9.5 days as many as 4% of the MD cells are degenerating.
A preganglionic autonomic nucleus in the dorsal gray commissure of the lumbar spinal cord of the rat
Authors: Hancock Michael B. , Peveto Cynthia A.
Published: January 2005

The distribution in the spinal cord of the rat of preganglionic neurons sending fibers into the hypogastric nerve was determined with the retrograde transport of horseradish peroxidase (HRP). Labeled cells were present in the intermediate gray matter of spinal segments L1‐L2. The majority (81%) of HRP‐filled cells formed a continuous column along the midline in the dorsal gray commissure. This cell column was termed the dorsal commissural nucleus (DCN). The remainder of HRP‐labeled cells were present bilaterally in the middle and lateral regions of the intermediate gray; the majority of the latter cells were located along the lateral border of the intermediate gray.

The present finding of a midline preganglionic autonomic cell column in the spinal cord of a mammal is contrary to previous reports, in which sympathetic preganglionic neurons have been localized primarily in the lateral intermediate gray. The DCN may be species‐specific and related to the system of short adrenergic neurons present in the pelvis.
A Golgi study of the early postnatal development of the visual cortex of the hooded rat
Authors: Juraska Janice M. , Fifková Eva
Published: January 2005

Although neuroanatomical plasticity has been demonstrated in the rat visual cortex, no systematic data on the dendritic development of the area are available. In the present study, the visual cortex of hooded rats at 1, 3, 5, 7, 10 and 15 postnatal days of age (P1‐P15) was impregnated with the rapid Golgi method. The cortex was divided into the superficial layers, II‐IV, and the middle layer V. At P1, pyramidal neurons had apical shafts and the beginning of the apical terminal arch. Analysis of both basilar and oblique dendritic number showed that pyramidal neurons of the middle layer developed more quickly than those in the superficial layers. The number of lower order basilar dendritic branches reached asymptote over the examined time period, whereas the higher order branches were still increasing in number but at a decelerating rate by P15. Dendrites at all ages exhibited varicosities which were especially prominent on the thin dendritic branches of the earlier ages. Some thin, filamentous processes, termed protospines, were found on dendrites and cell bodies at P1 to P5. They seemed to decrease by P7, when a few mature spines appeared. Spines increased in number on days P10 and P15. A comparison of the data from this study with quantified Golgi studies in adult rats indicates that by P10 and P15 the number of basilar branches is in the range seen in the adult.
Projections of a telencephalic auditory nucleus– field L–in the canary
Authors: Kelley Darcy B. , Nottebohm Fernando
Published: January 2005

Anterograde projections of a telencephalic auditory area – field L of the neostriatum – were traced in canaries, Serinus canarius. Field L was defined as the neostriatal projection of nucleus ovoidalis of the thalamus. Using amino acid autoradiography, two efferent projections of field L and adjacent neostriatum were observed: (1) a projection to the medial and ventral borders of nucleus hyperstriatum ventrale, pars caudale (HVc) and (2) a smaller projection to medial paleostriatum augmentatu (PA). When autoradiographic injection sites included neostriatum postero‐ventral to field L, a projection to archistriatum outlining the anterior and ventral borders of the nucleus robustus archistriatalis (RA) resulted. Injection sites that included neostriatum antero‐lateral to “L” gave rise to projections to the interior of HVc proper. Above background numbers of silver grains were consistently observed over caudal dorso‐lateral portions of nucleus ovoidalis. Following lesion of field L and adjacent neostriatum, argyrophilic degeneration was traced to medial PA and to a shelf of neostriatum underlying HVc. All observed anterograde projections were ipsilateral.

Two of the nuclei outlined by neostriatal projections in this study, HVc and RA, have important roles in the motor control of canary song (Nottebohm et al., '76). The development of song is dependent on auditory information. Auditory‐vocal neural connections described here may be involved in song learning.