bluuebunny/crossref_metadata_2025 huggingface dataset:
Retinal structure in the smooth dogfish, Mustelus canis: General description and light microscopy of giant ganglion cells
Authors: Stell William K. , Witkovsky Paul
Published: January 2005

Giant ganglion cells (GGC) were demonstrated in retinas of adult dogfish by Golgi impregnation, reduced silver and vital methylene blue staining. All GGC have large, flattened perikarya, and dendrites which radiate in a single horizontal plane of the inner synaptic (plexiform) layer. They are identifiable as ganglion cells by their axons, which after a tortuous initial course enter the nerve fiber layer. We divide the GGC into three varieties: (1) ordinary, with perikarya in the layer of ganglion cells and nerve fibers, and with dendrites radiating in the inner (proximal) one‐fourth of the inner synaptic layer; (2) displaced or Dogiel's cells, with perikarya in the amacrine cell layer and dendrites radiating in the outer (distal) one‐fourth of the inner synaptic layer; and (3) intermediate, with both perikarya and dendritic trees at intermediate levels in the inner synaptic layer.

Only the ordinary and displaced GGC in the ventral portion of retinas stained with methylene blue were studied in detail. Cells of both types are arranged in irregular patterns with perikarya about 0.8–1.0 mm apart. Dendrites of the ordinary GGC spread within an elliptical field having a major axis of about 1.7 mm (2.0 mm max) and a minor axis of about 1.5 mm (1.7 mm max). The major axis is vertical in the eye. Dendrites of the displaced GGC spread within a circular field having a diameter of about 1.9–2.0 mm (2.2 mm max). Quantitative comparison of the dendritic trees of ordinary and displaced GGC shows that they differ also in details of dendritic morphology, the dendrites of the ordinary GGC being on the average more numerous and highly branched but shorter than those of the displaced GGC. Ordinary and displaced GGC, therefore, comprise distinct populations which must be presumed to differ functionally.

For both ordinary and displaced GGC, the dendritic density and, therefore, the total available postsynaptic surface per unit retinal area decline exponentially with distance from the center to the edge of the dendritic tree. In contrast, the sensitivity to light is constant throughout the receptive field centers of comparable diameter which have been analysed in parallel electrophysiological studies. While the diameters of the largest ganglion cell dendritic fields and receptive field centers are similar, therefore, more detailed correlations of structure and function cannot be made at present.
The organization and projections of the paleostriatal complex in the pigeon (columba livia)
Authors: Karten Harvey J. , Dubbeldam Jacob L.
Published: January 2005

The paleostriatal complex (PC) of the pigeon lies in the basolateral wall of telencephalon, and consists of three major subdivisions: the paleostriatum augmentatum (PA), paleostriatum primitivum (PP), and nucleus intrapeduncularis (INP). The lobus parolfactorius (LPO) lies on the medial aspect of PA and has often been considered to be part of PA. The present study of afferent and efferent connections of the paleostriatal complex supports earlier previous suggestions that the PC is directly comparable to the basal ganglia of mammalia. High concentrations of acetylcholinesterase were found in the PA, LPO and INP. Intense yellowish green fluorescence, probably dopamine, was confined to the PA and LPO.

Stereotaxic lesions were placed in either the dorsal ventricular ridge structures above the PC (neo‐ and hyperstriatum), PA, LPO or PP‐INP, and animals sacrificed from one to six days postoperatively. The brains were stained with the Fink‐Heimer methods for the demonstration of degenerating axons and terminals. The region of the neo‐ and hyperstriatum was found to project upon the PA, in a seemingly topographic manner. PA was found to project topographically upon the PP and INP. In contrast, the LPO contributed to the medial forebrain bundle, terminating in the rostral lateral hypothalamus. LPO does not appear to project to the PP or INP.

Lesions of PP‐INP resulted in massive degeneration of a descending tract, the ansa lenticularis. Terminal degeneration was found in the anterior and posterior nuclei of the ansa lenticularis of the ventral diencephalon, nucleus dorsalis intermedius posterior and nucleus spiriformis lateralis of the dorsal thalamus, and the nucleus tegmenti pedunculopontinus pars compacta et disseminata of the isthmic tegmentum. In these several features of histochemical and hodological organization the PC alone appears similar to the caudate‐putamen and globus pallidus complex of mammalian brains.

More specifically, the PA resembles the caudate‐putamen, whereas PP and INP resemble the external and internal divisions of the globus pallidus, respectively. Similarities and differences between avian and mammalian brains, and the relationship of the present study of the PC and previous studies of the dorsal ventricular ridge structures are discussed (Karten, '69; Nauta and Karten, '70).
The horizontal cells of the rhesus monkey retina
Authors: Boycott B. B. , Kolb H.
Published: January 2005

The large peripheral horizontal cells of the retina of the rhesus monkey are compared with the smaller horizontal cells of the central area. There is most probably only one morphological type of horizontal cell in the rhesus monkey retina. Its dendrites go into cones and it has a single axon. From the fovea to the periphery of the retina there is a gradation in the number of cones an individual horizontal cell contacts. In the fovea a horizontal cell contacts six to nine cones; this ratio increases towards the periphery to between 30 and 40 cones to one horizontal cell.
Proliferation and turnover of glial cells in the forebrain of young adult mice as studied by repeated injections of 3H‐thymidine over a prolonged period of time
Authors: Kraus‐Ruppert R. , Laissue J. , Bürki H. , Odartchenko N.
Published: January 2005

The magnitude of glial cell renewal was studied on young adult mice using repeated intraperitoneal injections of 3H‐thymidine every eight hours over a period of 30 days. Mean labeling indices one hour after the last injection were as follows: Glial cells of the subependymal layer of the lateral ventricle, 61.5%; oligodendrocytes (various sites), 24 to 36.2%; astrocytes (various sites), 14.3 to 30.8%, and satellites in the cerebral cortex, 32.7%. Since DNA synthesis time of the proliferating, immature glial cells is unknown and may be shorter than the time interval of eight hours chosen for repeated injections of 3H‐thymidine, these results are interpreted as representing minimum values for turnover, during 30 days, of the various cell types in different areas of the forebrain. The significance of a marked proliferative activity of the glial cells as related to differentiation and possible migration of subependymal cells, is discussed.
The conformation, cytology and synaptology of the opossum inferior olivary nucleus
Authors: Bowman Michael H. , King James S.
Published: January 2005

This investigation was undertaken to determine the detailed structure and ultrastructure of the inferior olivary nucleus of the opossum (Didelphis marsupialis virginiana). Serial sections of the medulla oblongata were cut in either the frontal, parasagittal or horizontal plane and stained by routine Nissl procedures to determine the cytoarchitecture of the inferior olivary nuclear mass. Because of the apparent lack of distinct principal and accessory olivary subnuclei, a polyethylene plastic scaled reconstruction was made to determine the morphological features of the opossum olivary complex. A descriptive nomenclature was adopted rather than a terminology that would imply analogy with other species.

Both light microscopic (Nissl and Golgi) and electron microscopic analyses disclosed a single type of neuron throughout the inferior olivary nucleus. These small to medium (10–30 μ), pleomorphic nerve cells contain a round, eccentric nucleus and a modest amount of cytoplasm. Additional features of olivary somata include diffuse Nissl substance, abundant subsurface cisternae and spines.

The moderately branched and entangled dendritic arbor of the olivary neuron bears simple thorns on its proximal, intermediate and distal portions. Multiple spine clusters and unique excrescences termed spine crowned appendages are located on intermediate and distal dendrites.

Complex synaptic islands (glomeruli) are found throughout the nucleus and contain a central core of profiles identifiable as spine crowned appendages and small dendrites and/or spines. These core elements are surrounded by numerous boutons which synaptically contact them, and by a small intermediate dendrite. A mantle of astroglial lamellae appears to isolate the glomerulus from the surrounding neuropil.

The majority of the synaptic profiles that contact the soma and proximal, intermediate and distal dendrites contain either round vesicles (type 1) or pleomorphic vesicles (type 2). An estimation of the distribution of these terminals indicates that a predominance of type 2 terminals end upon the somata and proximal dendrites, whereas more distal dendritic ramifications receive an approximately equal proportion of the two types of endings. In addition to these endings ( types 1 and 2 ), large efflorescent terminals contact distal dendrites located throughout the nucleus. Furthermore, in different areas of the nuclear realm, small boutons containing only flattened vesicles and fibrous profiles containing pleomorphic vesicles contact intermediate and distal dendrites, respectively.

A few large marginal reticular neurons are present around the permiter of the inferior olivary nucleus. These cells send one or more dendrites into the nuclear domain. Such intraolivary dendrites may be synaptically contacted by the same types of terminals that end upon olivary neurons.
Development of left‐right asymmetry in the habenular nuclei of rana temporaria
Authors: Morgan M. J. , O'Donnell J. M. , Oliver R. F.
Published: January 2005

An investigation of the habenular nuclei in tadpoles, young frogs, and fully matured Rana temporaria, revealed several consistent left‐right asymmetries. In tadpoles and young frogs, the left nucleus is partially divided by a vertical septum; lacks cells adjoining the third ventricle along part of its length; and contains fewer free cell bodies in its lumen than the nucleus on the right. In addition, the beginnings of a second nucleus on the left can be seen, lateral to the much larger main left nucleus. The fully grown adult has two distinct left habenular nuclei and only one on the right.
The neuronal organization of the inferior colliculus of the adult cat. II. The pericentral nucleus
Authors: Rockel A. J. , Jones E. G.
Published: January 2005

The intrinsic organization and the connections of the pericentral nucleus of the inferior colliculus have been studied with the Golgi and Nauta techniques. The pericentral nucleus is a thin sheet of densely packed cells extending over the dorsal and posterior surfaces of the inferior colliculus.

The pericentral nucleus is composed of spiny and non‐spiny cells. There are large and small spiny neurons, all of which have numerous dendritic spines. The large cells are the most spiny and frequently have spines on their somata. The small spiny cells in most cases have spines on the initial segments of their axons as well as on their somata. The small cell type has a locally ramifying axon and should probably be regarded as an interneuron. The non‐spiny cell‐types are large, and multipolar or fusiform. The dendrites of the multipolar cells extend through the thickness of the pericentral nucleus and the parent cell probably gives rise to the efferents of the nucleus.

Although the pericentral nucleus has previously been described as having a layered “cortical” structure, there is little evidence to justify this, since no clearly defined axonal or cellular layers are present. The pericentral nucleus receives a heavy descending projection of fibers from the auditory cortex, and an ascending projection from the upper brainstem (probably only from the dorsal nucleus of the lateral lemniscus). The ascending system of fibers may also contribute branches to the central nucleus of the inferior colliculus. The ascending and descending afferents run parallel to the surface of the pericentral nucleus but at right‐angles to each other, thus forming a rectangular grid. The possible functional significance of this grid‐like arrangement is discussed.

No evidence was found for a projection from the central nucleus to the pericentral nucleus, but axons were seen to pass in the opposite direction, from the pericentral nucleus to the central nucleus, running parallel to the cellular laminae in the latter nucleus.
A three dimensional study of layer I of the rat parietal cortex
Authors: Vaughan Deborah W. , Peters Alan
Published: January 2005

Serial thin sections have been used to reconstruct neuronal processes in the outer portions of layer I of adult rat somatosensory cortex. The reconstructions show that two distinct forms of dendrites exist in this area: one that is smooth and varicose and another that bears spines along a shaft of relatively constant diameter. These two dendritic types, which originate from nonpyramidal and pyramidal neurons respectively, have differences in the distribution of organelles. Cortical dendrites terminate with no apparent morphological modification which would permit their identification in isolated thin sections. A pyramidal dendritic ending is blunt, about 0.5 μ in diameter, with microtubules and smooth endoplasmic reticulum in the terminal cytoplasm. Very long mitochondria which are invariably present within pyramidal dendrites, penetrate into an ending. A smooth dendrite terminates in an expansion containing microtubules and smooth endoplasmic reticulum, but no long mitochondrion. One or two asymmetrical synapses occur at the end of each terminating dendrite but do not encompass the tip. The principal axonal elements in layer I are small unmyelinated axons with en passant boutons. Serial examination reveals that various combinations of synaptic contacts are possible between axons and dendrites of both types.
Cerebellopontine projections in the american opossum. A study of their origin, distribution and overlap with fibers from the cerebral cortex
Authors: Yuen Hugo , Dom Richard M. , Martin George F.
Published: January 2005

The origin, course and distribution of cerebellopontine fibers was studied in the opossum by employing the Nauta‐Gygax and Fink‐Heimer techniques. Our results substantiate and extnd those of Brodal, Destombes, Lacerda and Angaut ('72) concerning the existence of cerebellopontine projections and provide evidence for a hitherto unreported fastigial projection to the basilar pons. Destruction of the caudal, medial division of the fastigial nucleus elicits bilateral degeneration in a restricted area of the medial pontine nucleus. This small terminal field is located in the angle between the medial lemniscus and the pyramidal tract and is found throughout the caudal three‐fifths of the pons. The degenerating fibers do not course within the descending brachium conjunctivum, but reach the pons by filtering through the reticular formation from the uncinate fasciculus. Lesions that involve either the interpositus anterior or the dentate nucleus produce degeneration within the contralateral descending brachium conjunctivum and basilar pons. Terminal fields are located within the median, medial (paramedian nucleus of cat), peduncular, ventral and lateral nuclei. The heaviest degeneration is in the medial nucleus.

Although cerebellar and cortical projections have different targets in the basilar pons, there is some overlap. Fastigial and preorbital fibers have partial overlap in the dorsal part of the medial nucleus, whereas the peduncular and lateral nuclei are the areas of overlap between the interpositus anterior and dentate projections with those from forelimb (and probably face) cortical areas. This overlap is particularly obvious in the caudal part of the lateral nucleus and occurs between fibers from limb motor‐sensory cortex and those arising mainly within the anterior interpositus nucleus. There is no pontine overlap between cerebellar and visual or auditory cortical projections.
Morphological organization of monoamine‐containing neurons in the hypothalamus of the painted turtle (Chrysemys picta)
Authors: Parent A. , Poitras D.
Published: January 2005

The distribution and morphological aspect of monoamine‐containing neurons in the hypothalamus of the turtle (Chrysemys picta) were studied by means of light and fluorescence (Falck‐Hillarp method) microscopy. In this reptilian brain, numerous neurons of the catecholamine type are unevenly distributed within the hypothalamic periventricular gray. They are present in large number along the ependymal wall of the sulcus intrahypothalamicus (paraventricular organ) and of the infundibular recess, but are less numerous along the preoptic recess. Most of these neurons appear as small bipolar cells with a short club‐like ventricular process contacting the cerebrospinal fluid of the third ventricle, and a more tenuous varicose process either penetrating the underlying hypothalamic tissue or reaching the external layer of the median eminence. Thin “collaterals” may be seen to arise from a few intraventricular processes of neurons of the paraventricular organ in material prepared by the Golgi‐Cox method. Another small group (10 to 15 perikarya) of larger catecholamine‐containing neurons apparently without any ventricular process are also present in the basomedial area of the caudal hypothalamus. In the present study no intrinsic neurons of the serotonin (5‐hydroxytryptamine) type were found within the hypothalamus of (Chrysemys picta). However, numerous fine nerve terminals and varicose fibers of the serotonin type, most probably of extrahypothalamic origin, were observed along the chiasmatic ridge and within the lateral hypothalamus, respectively.
Fiber composition of the posterior lateral‐line nerve of goldfish, investigated by electrophysiological and microscopical techniques
Authors: Fukuda Jun
Published: January 2005

The trunk of the posterior lateral‐line nerve of goldfish was stimulated electrically, and the evoked compound spike potential was recorded from the proximal cut end of the nerve. The spike potential consisted of four components which were distinguished from each other by differences of excitability, refractory period and conduction velocity. They were named F‐1, F‐2, F‐3 and S, in the order of decreasing conduction velocity. All of these components could generally be elicited by stimulation of the small nerve branches innervating canal organs.

By means of light‐ and electron‐microscopical examination, the fiber diameter spectrum of the posterior lateral‐line nerve was obtained. The observed compound spike potentials were reconstructed successfully from this fiber spectrum. It is concluded that the three subgroups, F‐1, F‐2 and F‐3 components are thick myelinated fibers and the S component is thin myelinated fibers.
Measurement of nerve fiber diameters in the region of the dorsal spinocerebellar and spinocervical tracts in the cat
Authors: Loewy Arthur D.
Published: January 2005

Nerve fibers in the region of the dorsal spinocerebellar tract (DSCT) and the spinocervical tract (SCT) in the adult cat were measured at various spinal levels. Fiber measurements were made from photographs of transverse sections of Epon embedded material that had been fixed by vascular perfusion with a paraformaldehyde solution, post‐fixed in osmium tetroxide, and stained with Azur II‐methylene blue.

The fiber diameter histograms from the region of the DSCT exhibited a bimodal distribution and between 50 to 75% of the fibers had a diameter of less than 5 μ. The presence of a subpopulation of large sized nerve fibers was identified between the 10 to 15 μ diameter intervals and this subpopulation appeared to decrease in size at the rostral spinal segments. This observation agrees with the electrophysiological studies of Lundberg and Oscarsson ('60) who found that the conduction velocity of the DSCT decreases at rostral levels.

The fiber diameter measurements from the region of the SCT appeared to exhibit a unimodal distribution and between 40 to 75% of the fibers in this region had a diameter of less than 5 μ. By omission of fibers less than 5 μ, it could be shown that the mean values of the SCT decreased at successively rostral spinal levels. However, when the cumulative frequency distributions of the SCT data from different spinal levels were compared, a definite trend of statistically significant differences at the 0.05 level could not be established.

The average fiber density (number of fibers/mm2) of the DSCT was 16,617 and the average fiber density of the SCT was 15,927.

The heterogeneous organization of the dorsolateral fasciculus is discussed.
Synaptic organization in the dorsal cochlear nucleus of the cat: A light and electron microscopic study
Authors: Kane Eileen Cohen
Published: January 2005

This report describes some observations of the synaptic organization of one region of the cat dorsal cochlear nucleus (DCN). The large “fusiform cell” and its innervation from the cochlea are emphasized. The morphology of the mature fusiform cell and its postnatal development are described in rapid Golgi impregnations of perfusion‐fixed littermate cats. The mature features are correlated with profiles of fusiform cell bodies, apical dendrites, and basal dendritic trunks in electron micrographs from adult cat brains. Small neurons and granule cells are also identified in electron micrographs. In Golgi impregnations, axons of small cells and granule cells may terminate upon fusiform cells. Six classes of axons can be distinguished in rapid Golgi impregnations of the DCN. Two classes are of cochlear origin. One axonal class arises from small cells. The sources of the remaining axonal classes have not been identified in this study. Primary afferents can terminate as large, mossy endings in the DCN neuropil. They can also participate in axonal nests along with axons and dendrites of small cells. In electron micrographs, four synaptic endings can be distinguished. Primary cochlear fibers end in large terminals with asymmetrical synaptic complexes and round, clear vesicles. Primary axons can end in glomeruli, resembling those of the cerebellum, or in synaptic nests which are conglomerates of neuronal processes including other types of endings. The origins of the other synaptic types are not yet known. According to this study, primary afferent input could influence fusiform cells directly or indirectly, via small cells and granule cells.
Fine structure of the synaptic endings on the Mauthner cell of the goldfish
Authors: Nakajima Yasuko
Published: January 2005

This study has investigated the fine structure of the Mauthner cell of the goldfish. The animals were divided into three groups of three fish and each group was perfused with one of the following fixatives: osmium tetroxide, glutaraldehyde, or formaldehyde. Large myelinated club endings and smallvesicle boutons (SVBs) are found on the distal part of the lateral dendrite. The club endings have the structure of the mixed synapse and contain large, round synaptic vesicles. The SVBs, appearing as small boutons, show structural features of the chemical synapse, and contain small synaptic vesicles, which are round when fixed with osmium tetroxide, but become elongated when fixed with aldehyde fixatives. Small myelinated club endings, SVBs, and large‐vesicle boutons (LVBs) are observed on the proximal part of the lateral dendrite, on the ventral dendrite, and on the cell body (excluding the axon hillock region). The LVBs, mostly appearing as large boutons, show the structure of either the mixed or the chemical synapse. They contain large, round vesicles. On the axon hillock and initial axon segment, there exist unmyelinated club endings containing medium‐size elongated vesicles and spiral fiber endings containing round medium‐size vesicles. An attempt was made to correlate these different types of endings within physiological functions.
Genetically‐associated variations in the destribution of dentate granule cell synapses upon the pyramidal cell dendrites in mouse hippocampus
Authors: Barber Robert P. , Vaughn James E. , Wimer Richard E. , Wimer Cynthia C.
Published: January 2005

The Ammonic system of inbred mouse strains was examined with light and electron microscopic methods in order to determine whether genetically‐associated variations occur in the distribution of dentate granule cell synapses (mossy fiber boutons) upon the dendrites of hippocampal pyramidal neurons in Regio Inferior. The results of this investigation showed that both qualitative and quantitative variations of the mossy fiber system occur among the strains examined. The most striking variation was seen in strain BALB/cJ. These mice are unique in that their mossy fibers do not form an appreciable infrapyramidal synaptic field, but form an extensive intrapyramidal synaptic field instead. In marked contrast, SM/J mice exhibit an extensive development of infrapyramidal mossy fiber boutons while their intrapyramidal mossy fiber synaptic field, when present at all, is limited to a very small portion of Regio Inferior adjacent to the hilus of Area Dentata.

Since the mouse strains used in this study do not exhibit neurological defects (i.e., they are not neurological mutants identified through the presence of gross behavioral or external anatomical abnormalities), the described variations may be thought of as representing genotype‐dependent differences in the connectivity of the Ammonic system which might occur within a “normal,” heterogeneous population of mice, Genetic, developmental and functional implications of the observed variations in the distribution of mossy fiber boutons upon Regio inferior pyramids are discussed.
Degeneration argyrophilia as an index of neural maturation: Studies on the optic tract of the golden hamster
Authors: Leonard Christiana M.
Published: January 2005

The maturation of the retinofugal Systems of the golden hamster has been traced by using the Fink‐Heimer silver technique to stain the degenerating axons and terminal arorizations aferr enucleation at different ages from birth to adulthool. From birth to 12 days of age intense degeneration argyrophilia can only be seen at short (15–36 hours) survival times in the optic tract and its terminal areas. By 72 hours after enucleation virtually all traces of axon degeneration have vanished. Starting at about 14 days of age (time of eye opening) sparse evidence of residual degeneration argyrophilia can be found in strtum opticum and stratum griseum superficiale of the superior colliculus at 72 and even at 240 hours survival. The intensity of the long‐lasting degeneration argyrophilia rapidly increases durin the next two weeks although shortlatency degeneration argyrophiloia does not start decreasing in intensity until 24 days of age.

Since Lund and Lund (1972) have found that typicl optic tract synapses are first identifiable in the superior colliculus of the rat at the time of eye opening (12 to 14 days), it is possibnle that the onset of long‐lasting degeneration argyrophilia signals an important structural or functional change in the neuron. Since degeneration methods can be used to trace the maturation of fiber tracts of known origin and trajectory, they may provide a relatively convenient means of identifying periods in which particular fiber Systems are underoing rapid developmental changes.
Morphological and cytochemical studies of synapses formed in culture between isolated rat superior cervical ganglion neurons
Authors: Rees Rosemary , Bunge Richard P.
Published: January 2005

Neurons from the superior cervical ganglia (SCG) of perinatal rats were mechanically dissociated and established in culture by a method modified from that of Bray ('70). The neurons attached to the collagen substrate with some degree of reaggregation, and their rapidly growing processes soon formed an interconnecting network. Light and electron microscope examination showed that the morphology of the cultured cells resembled that of the SCG principal cell; neither satellite cells nor the small intensely fluorescent interneurons were observed. After six to seven days in culture, synapses were seen on both the principal cell somata and on their processes. After aldehyde fixation, the synapses contained clear, pleiomorphic vesicles; after KMnO4 fixation a variable number of the vesicles contained dense cores.

After reserpine treatment and KMnO4 fixation the synaptic vesicles of the cultured networks contained few dense cores. Similarly treated cultured networks showed an increase in the number of synaptic vesicles with dense cores if incubated with dihydroxyphenylalanine prior to fixation, but a suppression of this increase in the presence of a specific inhibitor of dopamine B‐hydroxylase, FLA 63.

The morphology of synapses in the cultured networks was compared to that of endings in the intact rat SCG and iris in vivo, both before and after treatment with norepinephrine and 5‐hydroxydopamine. The vesicles in the synaptic endings in cultures were found to resemble those of the adrenergic endings of the rat iris, and to be similar to those seen within neuronal processes in the rat SCG. Our findings indicate that adrenergic synapses are formed between isolated SCG principal neurons in culture, and thus support recent evidence that such synapses occur in the intact rat SCG. The absence of other tissues which could receive innervation, and of ensheathing satellite cells, may provide a possible explanation for their frequency in the culture situation.
Motor and sensory flight neurones in a locust demonstrated using cobalt chloride
Authors: Tyrer N. M. , Altman J. S.
Published: January 2005

The central projections of motor and sensory neurons involved in the control of the wing beat in locusts have been analysed using cobalt chloride introduced axonally. From sections fo cobalt material, components of particular neuropile regions can be identified. The cobalt method offers an important advance in the analysis of insect neuropile.

The flight motor neurones in the mesothoracic ganglion are all basically similar in shape, with no clear distinction between elevator and depressor neurones. All have a highly branched dendritic tree which ramifies extensively through the dorsal neuropile. A neurone innervating a particular muscle can be recognised in different individuals by characteristic features but the pattern of dendritic branching is variable. Neurones involved in both flight and walking have some branches in a deeper layer of neuropile than those concerned only with flight, where the branches lie superficially.

Sensory projections from the flight sense organs are complex but compact and their positions in the neuropile are very predictable. They have large interganglionic components. The stretch receptors and wing sense organ projections lie mainly in the dorsal neuropile, whereas the other thoracic sensory receptors project ventrally, with branches to the dorsal neuropile at a few specific points. Associations between certain branches of sensory and motor neurones are demonstrated and their implications for the organisation of the flight reflexes discussed. It is suggested that parts of the motor neurone dendritic tree may be functionally equivalent to interneurones.
Morphology of extraganglionic fluorescent neurons in the myenteric plexus of the small intestine of the rat
Authors: Oosaki Takeo , Sugai Naonori
Published: January 2005

Fluorescent histochemical observations on the small intestine of the rat demonstrated that single fluorescent cells, separate from the principal ganglia, were present in the myenteric plexus. These extraganglionic cells gave rise to single processes which entered the ganglia and the interganglionic strands. They were of a very small size and were generally unipolar or pseudounipolar. A few fluorescent cells were also observed scattered along the interganglionic strands. Interruption of extrinsic nerve pathways to the small intestine caused a disappearance of meshworks of fluorescent fibers in the myenteric plexus, but in some areas the fluorescent cell alone was seen to remain. A photograph taken from the denervated myenteric plexus revealed that the cell possessed a quite long process.
Branched chorda tympani neurons and interactions among taste receptors
Authors: Miller Inglis J.
Published: January 2005

The preterminal branching pattern of nerve fibers from the chorda tympani nerve was examined in the tongues of rats using a normal silver stain. The lingual branch of the trigeminal nerve was sectioned unilaterally proximal to where it is joined by the chorda tympani and these fibers were allowed to degenerate from eight to ten days prior to sacrifice of the animals. Termination of the chorda tympani fibers in the anterior tongue was found to be limited to the taste bud region of the fungiform papillae. The control side of the tongue showed ubiquitous fiber terminations in the basal layers of the common epithelium of the filiform papillae as well as in the lateral walls of the fungiform papillae. These fibers were assumed to be of trigeminal origin. Seventy‐nine percent of the fungiform papillae on the experimental side of the tongue received fibers from a branched nerve bundle. Branch points within the nerve bundles were located deep within the tongue 300–500 μ below the taste bud in 43% of the papillae, at the base of 36% of the fungiform papillae about 125 μ below the taste bud, and within the papilla.

These data corroborate electrophysiological observations that single chorda tympani fibers receive input from more than one taste bud. Lateral inhibition observed among adjacent taste buds has been postulated to result from interaction of fiber inputs at branch points in the afferent fiber. From a theoretical consideration of the morphology of chorda tympani nerve fibers it is concluded that modification of the neural response may be feasible at branch points.
Olfactory bulb connections with basal rhinencephalon in the ferret: An evoked potential and neuroanatomical study
Authors: Dennis Barbara J. , Kerr David I. B.
Published: January 2005

The lateral olfactory tract (LOT) of the ferret has been shown to project to most of the pyriform lobe, as in the cat. Only a small medio‐posterior region of the pyriform cortex (the angular cortex), which has a distinctly different appearance in Nissl stained sections, proves to be devoid of olfactory connections. Despite the fact that sub‐areas can be recognized within olfactory cortex, there is an underlying constancy in design throughout. Latency measurements indicate that fine collateral branches of the LOT reach the posterior olfactory cortex, whereas mainly larger diameter (faster conducting) fibres comprise the contribution to anterior olfactory cortex. Thus in the present context it is sufficient to recognise just an anterior and posterior subdivision of olfactory cortex, contingent on the above criterion and correlated with cytoarchitectural features, chiefly variations in cortical layers II and III of the regions concerned.

Pyriform cortex directly in receipt of LOT fibres, and associated deeper cortical zones, generated potentials in the olfactory bulbs which can only be attributed to centrifugal input, thus further substantiating an olfactory role for this cortex. In addition, non‐cortical regions in receipt of LOT fibres, namely the anterior olfactory nucleus, olfactory tubercle, cortical amygdaloid nucleus and nucleus of the lateral olfactory tract, also contribute centrifugal input to the bulbs. All these regions are thereby capable of providing a rather direct feedback on olfactory bulb activity. The exact pathways concerned have yet to be determined.
An autoradiographic study of the time of origin and the pattern of granule cell migration in the dentate gyrus of the rat
Authors: Schlessinger Alice R. , Cowan W. M. , Gottlieb D. I.
Published: January 2005

The dentate gyrus of the rat contains about 600,000 granule cells. These small neurons are generated over a prolonged period from the 14th day of gestation until sime time after the second postnatal week. The majority of the cells pass through their last phase of DNA synthesis in the postnatal period, and during the peak period of cell generation, between the fifth and seventh days after birth, up to 50,000 granule cells are formed each day. Contrary to earlier reports, most of the cells pass through their last mitotic division either within the stratum granulosum itself, or within the hilar region of the developing gyrus. The precursor population of cells in the hilar region must therefore constitute a pool of true neuroblasts. The origin of this pool of cells has not been definitely established but it seems probable that its cells are derived from the neuroepithelium lining the lateral ventricle adjacent to the region from which the hippocampal pyramidal cells are generated. Examination of the final location of granule cells labeled at different stages reveals three distinct morphogenetic gradients in the gyrus. The cells in the dorsal blade tend to be formed earlier than those in the ventral blade; cells in the more caudal (or temporal) portions of the gyrus are generated earlier than those in more rostral (or septal) regions; and in all regions the more superficial neurons in the stratum granulosum are formed earlier than the deeper granule cells. The bearing of some of these findings on the development and organization of the connections of the dentate gyrus is discussed.
Anatomical evidence for cone and rod‐like receptors in the gray squirrel, ground squirrel, and prairie dog retinas
Authors: West Roger W. , Dowling John E.
Published: January 2005

In the gray squirrel (Sciurus carolinensis), the prairie dog (Cynomys ludovicianus), and the Mexican and 13‐line ground squirrels (Citellus mexicanus and C. tridecemlineatus) there exist two distinct classes of photoreceptors that have cone‐like and rod‐like anatomical features respectively. These two receptor classes were previously known to exist in the gray squirrel, but only the cone‐like (C) receptor had been observed in the other species. We have now found small numbers of rod‐like (R) receptors in the other species. as well. R‐receptors comprise about 40% of the receptors in the gray squirrel, 10% of the receptors in the prairie dog, and 4–5% of the receptors in the two species of ground squirrel.

This paper describes certain light and electron microscopic features of these two receptor classes including their synaptic connections with second‐order cells and with each other. We find that the C‐receptor has a morphology and synaptic organization characteristic of other mammalian cones. However. the R‐receptor differs from other mammalian rods in certain morphological respects, and its synaptic organization has both cone and rod characteristics as well as some unusual features.
Nerve fiber hypertrophy in posterior tibial nerves of mice in response to voluntary running activity during aging
Authors: Samorajski T. , Rolsten Carolyn
Published: January 2005

Three‐month‐old male C57BL/10 mice were exercised by voluntary running activity in vertically revolving wheels for two hours each day until 24 months of age. Activity scores were recorded each day and the animals were regularly weighed and inspected for abnormalities. Control animals were similarly treated except that the acitvity wheels were immobilized.

At the end of the exercise period, survival was 84% for the exercise group and 64% for the controls. Light microscopic examination of the posterior tibial nerve of the surviving animals showed a significant fiber hypertrophy in response to the exercise. The number of myelinated fibers in nerves from exercised animals did not differ from those of the controls.

On the basis of these data, it is suggested that prolonged exercise does not prevent the loss of peripheral nerve fibers associated with age but rather, may exert an effect on the nervous system by modifying the surviving cells.
The pattern of ocular dominance columns in macaque visual cortex revealed by a reduced silver stain
Authors: LeVay Simon , Hubel David H. , Wiesel Torsten N.
Published: January 2005

A pattern of alternative dark and pale bands was observed in the straite cortex of the macaque monkey. The bands, which ran parallel to the surface, were seen in tangential sections stained with a reduced silver method for normal fibers and were most clear in layer 4C α, immediately deep to the line of Gennari. The dark bands were about 300 μ wide and showed blind endings and bifurcations. The light bands were about 50 μ wide and did not branch or terminate within area 17.

Because the dark bands were similar in width to the bands of terminal degeneration which have been shown to result from single‐layer lesions of the lateral geniculate body, it seemed possible that they corresponded to ocular dominance columns. To test this idea, the boundaries of ocular dominance columns were marked in a physiological experiment: tangential electrode penetrations were made in an anesthetized monkey and, as the electrode was advanced horizontally in the fourth layer, the eye preference of single units and of the background activity was monitored. Small electrolytic lesions were placed at the points where a change in eye preference occurred. The brain was subsequently fixed, sectioned tangentially and stained with the silver method. All the lesions — a total of 12 — fell directly on the pale bands. Moreover, the electrode had not passed over any pale bands without a lesion being placed. It was concluded that the dark bands do correspond to single ocular dominance columns and the pale bands to the boundaries between columns.

The banding appearance is due to a greater density of tangential fibers within columns than at the borders of columns. These tangential fibers are in part the preterminal arborizations of geniculocortical axons, since some of them have been shown to degenerate after geniculate lesion.

The ocular dominance columns were mapped for most of the striate cortex, using serial tengential sections stained with the silver method. The overall pattern was similar in several monkeys, though the details of the branching arrangements vaired from animal to animal. The columns met the 17–18 border at rigtht angles. On the outer surface of the hemisphere the columns converged from the 17–18 border, turned medially with repeated fusions of columns, and streamed over the lip of the calcarine fissure. In the roof of the fissure they met a second system of columns oriented parasagittally. In terms of the visual field, the columns ran roughly horizontally for the central 10° of the field, and circumferentially beyond that. The columns were not mapped in the stem of the fissure, the area corresponding to the far periphery of the field.

The constancy of column width across the cortex probably allows a functional matching between ocular‐dominance and orientation columns.
The topographical and laminar organization of the presubiculum's projection to the ipsi‐ and contralateral entorhinal cortex in the guinea pig
Authors: Shipley Michael T.
Published: January 2005

This is a detailed report of a previously described projection from the presubiculum to the entorhinal are (Shipley,1974). The terminal degeneration in the entorhinal area is specifically confined to the outer three layers of this cortex. The projection is topographically organized and confined to dorsal and medial parts of the entorhinal area. A similarly organized projection courses via the dorsal psalterium (dorsal hippocambal commissure) to the contralateral entorhinal area. Thus each presubiculum has an orgainzed terminal pathway to the entorhinal cortices of both hemisphers.
Lamination and differential distribution of thalamic afferents within the sensory‐motor cortex of the squirrel monkey
Authors: Jones E. G.
Published: January 2005

The structure of the first somatic sensory area (areas 3,1 and 2), of the motor area (area 4) and the intervening transitional field (area 3a) is described in the squirrel monkey (Saimiri sciureus) using Nissl, Bodian, Weil and Golgi preparations. The laminar arrangement of both cells and axons is briefly described and this is correlated with the Nauta and autoradiographic techniques. The latter method was used particularly in order to assess quantitative differences in the density of thalamic projections to the five cytoarchitectonic fields.

In the somatic sensory areas thalamic afferents terminate not only in layer IV but to a large extent also in a recognizable part of layer III (layer IIIb). In area 4 thalamic terminals fill much of layer III, reaching almost to layer II. In area 3a the extent is intermediate between that seen in areas 3 and 4. It is thought that the extensive spread of thalamic terminals is related to the elongated form of a particular class of spine‐bearing cell whose somata are situated in layer IV (Jones, 1975). In all areas a small proportion of thalamic afferents end also in layer I. Evidence is presented to indicate that specific afferent fibers emanating from the ventrobasal and ventrolateral complexes of the thalamus terminate in both the deep and superficial parts of layer I While “non‐specific” afferents from other thalamic sources end in the superficial part.

The autoradiographic studies indicate that there are considerable differences between the number of thalamic afferents ending in area 3 on the hand and in areas 1 and 2 on the other. Given this and the nature of the degenerating thalamic afferents observed in Nauta preparations, it is possible to identify thalamic afferents in normal Golgi preparations and significant differences are detectable in areas 4, 3 and 1 and 2. It is yet uncertain whether the slightly thinner, more sparsely distributed thalamic afferents ending in areas 1 and 2 are branches of those directed primarily to area 3.
Receptive fields of single cells and topography in mouse visual cortex
Authors: Dräger Ursula C.
Published: January 2005

The visual cortex was studied in the mouse (C57 Black/6J strain) by recording from single units, and a topographic map of the visual field was constructed. Forty‐five percent of the neurons in striate cortex responded best to oriented line stimuli moving over their receptive fields; they were classified as simple (17%), complex (25%) and hypercomplex (3%). Of all preferred orientations horizontal was most common. Fifty‐five percent of receptive fields were cicularly symmetric: these were on‐center (25%), off‐center (7%) and homogeneous on‐off in type (23%). Optimal stimulus velocities were much higher than those reported in the cat, mostly varying between 20° and 300°/sec. The field of vision common to the two eyes projected to more than one‐third of the striate cortex. Although the contralateral eye provided the dominating influence on cells in this binocular area, more than two‐thirds of cells could also be driven through the ipsilateral eye. The topography of area 17 was similar to that found in other mammals: the upper visual field projected posteriorly, the most nasal part mapped onto the lateral border. Here the projection did not end at the vertical meridian passing through the animal's long axis, but proceeded for at least 10° into the ipsilateral hemifield of vision, so that at least 20° of visual field were represented in both hemispheres. The magnification in area 17 was rather uniform throughout the visual field. In an area latral to area 17 (18a) the fields were projected in condensed mirror image fashion with respect to the arrangement of area 17. Medial to area 17 a third visual area (area 18) was again related to 17 as a condensed mirror image.