bluuebunny/crossref_metadata_2025 huggingface dataset:
3H estradiol in catecholamine neurons of rat brain stem: Combined localization by autoradiography and formaldehyde‐induced fluorescence
Authors: Heritage A. S. , Grant L. D. , Stumpf W. E.
Published: January 2005

3H estradiol–17β was localized in nuclei of catecholamine (CA) neurons of the rat lower brain stem, i.e., midbrain, pons and medulla, by employing a combined formaldehyde‐induced fluorescence (FIF)‐autoradiography approach which permits the direct visualization of 3H estradiol uptake in relation to CA‐neuron perikarya and terminals. In the medulla, noradrenalin (NA)‐containing neurons in and adjacent to the nucleus (n.) reticularis lateralis (group A1) and in the vicinity of the n. tractus solitarii (group A2) concentrated 3H estradiol. In the pons, NA neurons dorsal to the n. olivaris superior (group A5), in the locus ceruleus (group A6) and ventral to the pedunculus cerebellaris superior (group A7) displayed 3H estradiol uptake. In the midbrain, dopamine (DA)‐containing neurons in the n. cuneiformis (group A8), in the zona compacta of the substantia nigra (group A9) and adjacent to the n. interpeduncularis (group A10), were not seen to concentrate 3H estradiol. This is in contrast to DA neurons in the n. arcuatus of the hypothalamus (group A12), previously reported to concentrate 3H estradiol. In addition, certain non‐CA‐containing neurons with nuclear uptake of 3H estradiol were observed to be surrounded by CA terminals in such areas as substantia grisea centralis, n. tractus solitarii and n. tractus spinalis nervi trigemini. This suggests a second mode of interaction between CA neurons and estrogen target neurons. The estradiol‐CA neuron relationships described may provide morphological substrates underlying functional interactions between estradiol and CA neurons in the rat brain.
Cell death of motoneurons in the chick embryo spinal cord. I. A light and electron microscopic study of naturally occurring and induced cell loss during development
Authors: Chu‐Wang I‐Wu , Oppenheim Ronald W.
Published: January 2005

The onset and sequence of cell death in the lateral motoneurons of the lumbar spinal cord of the chick embryo was studied between 4 and 18 days of incubation by light and electron microscopy. The naturally occurring degeneration of a few motoneurons begins already on day 4 of incubation, but the cell loss becomes much more frequent from day 5.5 to day 9, during which 40% of the neuron population degenerates. In the light microscope, the degenerating neurons are seen to undergo shrinkage and condensation. Ultrastructurally, two types of degeneration can be recognized. In the first, termed Type I, the polyribosomes are dissociated and appear free in the cytoplasm. Ribosomes also become detached from rough endoplasmic reticulum, although small pieces of cisternae of rough endoplasmic reticulum are still recognizable. Most of the mitochondria are vacuolized. These changes are accompanied by the appearance of a pyknotic nucleus which contains condensed chromatin masses. The most characteristic feature in what we term Type II degeneration is the striking dilatation of the endoplasmic reticulum, the nuclear envelope and the Golgi apparatus. Ribosomes still form distinctly rosette‐like polyribosomes. A few mitochondria show signs of degeneration. The nuclear profile in most cells of this type is rounded whereas the chromatin is becoming condensed. In the late stages of Type II degeneration, the dilated membrane systems break down into numerous vesicles some of which still have ribosomes attached. Only late in the sequence of Type II degeneration do polyribosomes then dissociate to free monoribosomes. The degeneration process in both types leads finally to cell death and complete cellular breakdown: the entire process being due to an autolytic mechanism. The nuclear envelope breaks down and the nuclear content becomes mixed with lytic cytoplasm. The dying cell finally either condenses into one big globule or several smaller fragmented globules. All the globular debris are highly osmiophilic and compact. Only at this stage of breakdown is the cell debris phagocytozed by radial ependymal processes and mononuclear leukocytes. The entire degenerative process in these immature neurons is strikingly rapid.

In the case of induced cell death by removal of the limb bud on day 2.5, we found that both types of degeneration described above also occur in the peripherally deprived lateral motor column (LMC). The only obvious difference is that limb bud removal increases the speed and the number of cells undergoing degeneration. By day 10, about 90% of the neuron population in the deprived LMC have completely disappeared.
The development and degeneration of Purkinje cells in pcd mutant mice
Authors: Landis Story C. , Mullen Richard J.
Published: January 2005

Purkinje cell degeneration (pcd), an autosomal recessive mutation in the mouse, causes the postnatal death of virtually all cerebellar Purkinje cells during the third and fourth postnatal week. We have compared the postnatal development of normal and pcd mutant Purkinje cells. The early deviations from normal development involve primarily the perikaryonal polysomes and endoplasmic reticulum. Many of the mutant Purkinje cells retain abnormally the basal accumulation of polysomes, a finding which permits the identification of affected animals at postnatal day 15, one week prior to the onset of behavioral abnormalities. In addition, the affected Purkinje cells possess unusual configurations of endoplasmic reticulum with associated electron‐dense particles similar to but larger than ribosomes, mature and forming intracisternal A particles and nematosomes. Before the pcd Purkinje cells degenerate they appear to receive all their appropriate synaptic contacts. Some disruption, however, of parallel fiber: Purkinje spine synaptogenesis occurs at late stages of development. Some spines lack presynaptic elements, postsynaptic thickenings are present along the dendritic shafts and parallel fibers appear to make synaptic contacts directly onto the shafts. The spectrum of early morphological changes that has been observed in pcd mutant Purkinje cells is thus far unique to this cerebellar abnormality.
The effects of undernutrition on Purkinje cell dendritic growth in the rat
Authors: McConnell P. , Berry M.
Published: January 2005

The effects of undernutrition on the developing cerebellum were studied in 30‐day‐old rats undernourished from birth byrestricting access to the lactating mother. These animals showed a significant reduction in cerebellar weight when compared with well‐nourished controls. Quantitative studies of the cerebeller vermis revealed a 34.2% reduction in total area, with the densityof both granule cells and Purkinje cells increased. Network analysisof Golgi‐Cox preprations indicated a significant increase in the density of dendritic fields of Purkinje cells, although there was a 37% decrease in overall network size, due to reduction inthe total number of dendritic segments, and a reduction in the length of distal segments. Topological analysis indicated that the network had developed by terminal branching, as in normal animals, butwithsome deviation from the usual purely random branching pattern.

All the observed modifications may be accounted for in terms of alterations in protein synthesis and DNA synthesis ocurring in undernourished animals. This leads to alterations in the extent of the intereuronal matrix, a rdduction in the number of granule cells and direct effects in Purkinje cell metabolism, all of which influence dendritic development, although the relative impotance of each of these factors awaits precise definition.
Categories of axons in the inferior cardiac nerve of the cat
Authors: Emery Dennis G. , Foreman Robert D. , Coggeshall Richard E.
Published: January 2005

Myelinated and unmyelinated axons in the inferior cardiac nerve of the cat were examined to determine how many axons were (1) sensory, (2) preganglionic sympathetic, and (3) postganglionic sympathetic. In one group of cats, a segment was removed from the middle of the inferior cardiac nerve as a control, and the proximal and distal stumps of the nerve were examined one week later. In another group of cats, the control segment of nerve was removed and the first thoracic white ramus communicans and sympathetic trunk were cut proximal to the stellate ganglion, followed in one week by examination of the proximal and distal stumps of the inferior cardiac nerve. In still another group of cats, the first five thoracic spinal nerves were cut just distal to the dorsal root ganglion. The counts of myelinated and unmyelinated axons after these surgical procedures indicated that, in the cat inferior cardiac nerve, all or almost all of the approximately 30,000 unmyelinated axons and 10% of the myelinated axons are postganglionic sympathetic fibers, and that approximately 90% of the myelinated axons are sensory.
Segmental homology and variation in flexor motoneurons of the crayfish abdomen
Authors: Mittenthal Jay E. , Wine Jeffrey J.
Published: January 2005

In the crayfish abdomen the anterior five of six ganglia are serially homologous. The locations and sizes of motoneuron somata of the fast and slow flexor systems have been determined by axonal infusion of cobalt. The somata form three clusters, distinguished by soma position in the ganglia and course of axons in the nerve cord. For the fast flexors, the anterior group shows the greatest departure from serial homology; it has one soma in the first ganglion (G1), three in G2 and G3, two in G4, and none in G5. The medial group contains the giant motoneuron, the peripheral inhibitor, and two smaller neurons in all five ganglia. The posterior group contains four somata in G1‐G4 and three in G5. The slow flexor motoneuron somata cluster into the same three groups.

Intersegmental variations in soma size and in volume of muscle innervated are positively correlated for the giant motoneuron and for the peripheral inhibitors of both fast and slow flexor muscles.

Corresponding clusters of neuropilar branches of the fast flexor peripheral inhibitor can be recognized in each of the anterior five abdominal ganglia of Procambarus. Inhibitors in G1‐G5 occupy roughly corresponding positions with respect to the dorsal giant interneurons and receive similar inputs.

Ganglia of the crayfish abdomen were compared by using the positions of serially homologous somata to define a mapping from each ganglion onto G2. The mappings support the conventional view that G2, G3, and G4 are typical abdominal ganglia, while G1 and G5 show special end effects.

Groups of flexor motoneurons homologous to the three groups in crayfish, and to some extent homologous neurons, can be recognized in ganglia of other decapod crustacea. Groups of motoneurons that are strikingly similar to the groups in decapod crustacea appear in several orders of insects. The groups in crustacea and insects may be homologous, and corresponding groups may exist widely within the Articulata. These apparent intersegmental and interspecific homologies suggest homology of large‐scale features of ganglionic organization.
Anatomical demonstration of orientation columns in macaque monkey
Authors: Hubel David H. , Wiesel Torsten N. , Stryker Michael P.
Published: January 2005

In the macaque monkey striate (primary visual) cortex, the grouping of cells into ocular dominance and orientation columns leads to the prediction of highly specific spatial patterns of cellular activity in response to stimulation by lines through one or both eyes. In the pesent paper these paterns have been examined by the 2‐deoxyuglucose autoradiographic method developed by Sokoloff and his group (Kennedy et al, '76). An anesthetized monkey was given an injection of 14C 2‐deoxyglucose and then visually stimulated for 45 minues with a large array of moving vertical stripes, with both eyes open. The 14C autoradiographs of striate cortex showed vertical bands of label extending through the full cortical thickness. Layer I was at most only lightly labelled, and layers IV b and VI wee the most dense. Layer IV c (the site of terminations of most geniculate afferents) was labelled uniformly along its length, as expected from the lack of orientation specificity of units recorded in that leyer. In the other layers the pattern seen in tangential sections was complex, consisting of swirling stripes with many bifurcations and blind endings, but with occasional more regular regions whee the stripes wee roughly parallel. Interstripe distance was rather constant, at 570 μm. Ocular dominance columns were examined in this same monkey, in the same region, by injecting one eye with 3H‐proline two weeks before the deoxyglucose experiment, and preparing a second set of autoradiographs of the sections after prolonged washing to remove the 14C‐deoxyglucose. As seen in tangential sections through layer IV c, these columns had the usual stripe‐like form, with a period of 770 μm, but were simpler in their pattern than the orientation stripes, with fewer bifurcations and less swirling. A comparison of the two sets of columns in the same area showed many intersections, but no strict or consistent relationships: angles of intersection showed a distribution that was not obviously different from that expected for any two randomly superimposed sets of lines.

Another monkey was stimulated with vertical stripes, but with only one eye open. Deoxyglucose autoradiographs of tangential sections showed regular uniform rows of label in layer IV c, with all the characteristic features of eye dominance columns. In the layers above and below IV c the rows in tangential view were broken up into regularly spaced patches of label, presumably representing aggregations of cells responsive to vertically oriented stimuli. The patches showed no consistent alignment across the ocular dominance rows, and indeed no such tendency would be expected, considering the complexity of the orientation columns. This pattern of labelling is again predicted from and confirms the previous physiological studies.
Connections of he visual cortex in the hedgehog (Paraechinus hypomelas). II. Corticocortical projections
Authors: Gould Harry J. , Ebner Ford F.
Published: January 2005

Cortical subdivisions based on cytoarchitectural and myeloarchitectural observation of normal tissue were correlated with the topography of corticocortical connections in the visual system of the Pakistani hedgehog. Large subpial aspiration lesions were made in both visual and non‐visual cortical regions to determine he areal limits of the corticocortical connections of the visual cortex. Subsequently, discrete electrolytic lesions were placed within the visual cortex. After appropriate survival periods, the brains were processed and stained with the Fink‐Heimer technique.

The results of these studies show that the visual cortex may be subdivided into four distinct regions from lateral to medial; the lateral parastriate cortex, the lateral and medial part of striate cortex, and the medial parastriate cortex. With in these regions, interhemispheric connections between visual cortices arise mainly in the lateral striate and lateral parastriate regions and terminate in a single band within the lateral portion of the cytoarchitecturally defined striate cortex. These corticocortical projections, therefore, substantially overlap with the geniculostriate projections. Lateral striate cortex and lateral parastriate cortex project in a reciprocal fashion that correlates well with the physiologically defined mirror image representation of two retinotopic maps of the binocular visual field on cortex. These connections are reflected about a line that is closely correlated with the medial edge of the band of commissural axon terminals that is located within the lateral striate cortex, instead of corresponding exactly with the striate‐parastriate border as they do in other mammals. Medial striate cortex projects to medial parastriate cortex, indicating that the monocular portion of V I is related to a separate secondary area of cortex on the medial wall of the hemisphere.
Different patterns of cochlear innervation during the development of the kitten
Authors: Pujol R. , Carlier E. , Devigne C.
Published: January 2005

The postnatal development of neuro‐epithelial junctions inside the kitten cochlea has been investigated by electron microscopy, and correlated with previous electrophysiological results. Two main stages of development are described. During the first postnatal days, outer hair cells look very immature with only a few afferent endings adjoining them. The inner hair cells, on the other hand, are surrounded by numerous endings with mature afferent and efferent synapses. Thus, when the efferent olive‐cochlear system begins to function during the first postnatal days, it is days, it is able to modify only inner hair cell responses. The second postnatal week is characterized by maturation of the large efferent endings below the outer hair cells. At the same time, direct efferent connections become sparce at the level of inner hair cells. The maturation of hearing, at the receptor level, seems to proceed in two steps, one related to inner hair cells and corresponding to a gross and primitive hearing, the other related to outer hair cells and corresponding to more precise and discriminative hearing abilities.
The number and distribution of ganglion cells in the retina of the brush‐tailed possum, Trichosurus vulpecula
Authors: Freeman Brian , Tancred Elizabeth
Published: January 2005

The distribution of ganglion cells in the retina of the adult brush‐tailed possum was determined by light microscopy of Nissl stained retinal whole mounts. Qualitatively, the distribution in this marsupial retina shows features, such as an area centralis and a visual streak, which are found separately or together in eutherian mammals. The possum retina is avascular and the eye has a weak tapetumin the superior fundus.

The retinal area is 260 mm2 and there are about 280,000 ganglion cells. The diameters of the ganglion cell somas range from 5μm to 26μm and the frequency distribution of soma size classes is skewed and unimodal (mean: 12.8μm) with 62% of the cells falling in the class of diameters 7‐13μm. Maps of ganglion cell density were made for five retinae. These mapsshow that there is a band of high ganglion cell density (> 2,000 cells mm−2) which extends across the retina about 0.6 mm above the optic disc in the tapetal region of the fundus and which lies in the plane of the animal's horizon when the eyes are in their primary position. By analogy with other species, this band is termed the visual streak. Near the temporal end of the visual streak, 2.9 mm from the optic disc, the ganglion cell density reaches a localized maximum of approximately 5,000 cells mm−2 thereby defining the centre of an area centralis (> 3,000 cells mm−2). The posterior nodal distance of the possum eye was estimated at 7.8 mm, which correspondsto a retinal magnification of 136μm per degree of visual field. There are up to 30,000 glial cells which lie in, or slightly vitread to, the layer of the retinal ganglion cells.
Anatomical observations on the dorsal column nuclei, their thalamic projection and the cytoarchitecture of some somatosensory thalamic nuclei in the monkey
Authors: Boivie Jörgen
Published: January 2005

The results of the present anatomical study on macaque monkeys concern some aspects of the dorsal column nuclei, their projection to the thalamus and the cytoarchitecture and topography of the recipient areas in the thalamus for the somatosensory pathways. Some observations regarding the cytoarchitecture of the dorsal column nuclei are reported; the gracile nucleus differs cytoarchitectonically over the rostrocaudal dimension in a way similar to the feline nucleus; the cuneate nucleus has a distinct pars rotunda (Ferraro and Barrera, '35) which might be analogous to a similar structure in the raccoon shown to be activated by afferents from the volar side of the hand and digits (Johnson et al., '68). Cytoarchitectonic observations and other arguments suggesting the presence of the nucleus Z in the monkey are presented.

In Nissl stained frontal sections, cut in the stereotaxic frontal plane as well as in sections cut perpendicular to the long axis of the brain stem the cytoarchitecture and topography of the posteromedial, ventroposterior and centrolateral thalamic nuclei of the macaque were analysed. The posteromedial nucleus (POm) has been found to include portions of Olszewski's ('52) magnocellular medial geniculate, suprageniculate and pulvinar nuclei. The nucleus ventralis posterolateralis (VPL) corresponds to the main portion of Olszewski's VPLc, whereas most of his VPLo corresponds to the nucleus ventralis intermedius of Hassler ('59) and Mehler ('71).

Electrolytic lesions were used to study the projection from the gracile and cuneate nuclei to the thalamus. With postoperative survival periods of 6 to 14 days the resulting degeneration was studied in frontal sections stained according to the Wiitanen modification of the Fink‐Heimer method. Both the gracile and cuneate nuclei project profusely to the contralateral nucleus ventralis posterolateralis and more sparsely to the contralateral posteromedial nucleus and the zona incerta. A distinct somatotopic organization exists in the projection to the ventroposterior nucleus, but not in that to the other target areas. The projection to the ventroposterior nucleus is very dense and evenly distributed except rostrally and dorsally, where it is more scattered.

It is concluded that the posteromedial and the ventroposterior thalamic nuclei are very similar in monkeys and cats regarding cytoarchitecture, topography and afferent projections from the dorsal column nuclei.
Organization of the mossy fiber system of the rat studied in extended hippocampi. I. Terminal area related to number of granule and pyramidal cells
Authors: Gaarskjaer Frank B.
Published: January 2005

A quantitative and qualitative study of the septotemporal organization of the hippocampal mossy fiber system has been carried out in the rat. Transverse sections of isolated and extended hippocampi were stained according to Nisel's or Timm's method. At 12 equidistant levels covering the entire length of the hippocampus the following parameters were measured: the length of the granule cell layer and the mossy fiber layer, the area of the fields containing mossy fiber boutons, the number of granule cells, and the number of pyramidal cells in the hilus and in the regio inferior.

Septally the pyramidal layer of the regio inferior is broad and the cells within the layer are relatively widely spaced. Here the mossy fiber boutons intrude deep into the layer. At more temporal levels the cells are tightly packed, the cell‐layer is narrower, and the boutons predominantly terminate suprapyramidally.

The length of the granular layer is greatest septally, while the length of the mossy fiber layer is greatest temporally. The area of the hilus, occupied by the mossy fiber boutons, is large at most of the temporal levels and small at the septal levels, whereas in CA3 the reverse is true. The greatest number of granule cells was found at the more septal levels. Conversely, the majority of the pyramidal cells in the hilus and in the regio inferior is situated temporally. The ratio of granule cells to pyramidal cells (hilus and regio inferior together) declines linearly from approximately ten at septal levels to approximately one at temporal levels. Because the mossy fibers are distributed fairly transverse to the long axis of the hippocampus, the variation in the ratio of granule cells to pyramidal cells reflects a corresponding variation in the number of innervating to innervated cells within the mossy fiber system.
The motor column and sensory projections of the branchial cranial nerves in the frog
Authors: Matesz Clara , Székely George
Published: January 2005

Motor nuclei and primary afferent projections of branchial cranial nerves were shown with the CoCl2 staining technique. Motor nuclei constitute a discontinuous column at the ventrolateral margin of the gray matter. The size of motoneurons decreases in the orocaudal direction within the column. The dendrites assemble in two main directions forming a dorsomedial and a ventrolateral dendritic array. The axons originate in the ventrolateral dendrites and run straight to the motor roots. Preganglionic vegetative neurons were found in a separate group at the level of the abducens nucleus, and intermingled with motoneurons at the level of the glossopharyngeus and vagus nuclei. Their axons join the visceral sensory roots of the respective nerve.

The tractus spinalia trigemini has a short and weak ascending limb, and a strong descending limb which decussates in the first and second segments of the spinal cord. A few uncrossed large fibers continue as far as the midthoracic level, In addition to trigeminal fibers, a small contingent of facial fibers and a significant number of vagus fibers contribute to the tractus spinalis. Small caliber fibers of the tractus and fine collaterals of large caliber fibers terminate in a continuous column which lies, in its largest part, in the neuropil medial to the tractus. The pattern of fiber terminations in this area is identical with that in the substantia gelatinosa. This area is called the nucleus spinalis trigemini. Coarse collaterals terminate in a discontinuous column of large and medium‐sized neurons, extending caudally to the obex region. This area is the largest at the level of the trigeminus nucleus and is called the nucleus principalis trigemini.

The cells of origin of the mesencephalic tractus of the trigeminus lie in the second and fourth layers of the optic tectum. The descending fibers run ventral to the tractus spinalis in a separate bundle. They emit collaterals to the large fiber termination areas and to branchiomotor nuclei. Direct contacts are established with trigeminus motoneurons. In the obex region a significant number of collaterals invade the dorsomedial part of the gray matter.

The fasciculus solitarius begins at the level of the trigeminal nucleus and terminates in the commissura infima at the medullospinal border. The nucleus solitarius begins at the oral pole of the glossopharyngeus nucleus. The fasciculus receives fibers from the facialis (intermedius), glossopharyngeus and vagus nerves. The fibers spread over the total extent of the fasciculus: the facialis fibers exhibit a preference for a dorsomedial position and the glossopharyngeusvagus fibers for a ventrolateral position. There are several interchanging fibers between the somatic sensory and visceral sensory projecting areas.

The results indicate a close similarity between amphibian and mammalian brain stem motor nuclei and sensory projections, though some parts are present in a primordial form in the frog.
An anterograde degeneration study of the tangential spread of axons in cortical areas 17 and 18 of the squirrel monkey (Saimiri Sciureus)
Authors: Colonnier M. , Sas E.
Published: January 2005

In area 17 of squirrel monkey, lamina IVB of Brodmann is divided into three sublaminae by a thin, dense row of cell bodies, the largest of which have apical poles. Study of the 17/18 border suggests that these are a group of pyramidal cells, continuous with the large border pyramids in the depth of layer III in area 18. In contrast, the densely packed granule cells of layers IVA and IVC appear to be continuous with those of layer IV of area 18. It is thus proposed that in area 17, the third and fourth neocortical layers not only divide into sublaminae, but that these in turn interdigitate and intermingle their cell types. The tangential extent of intracortical fibers has been studied by making perpendicular slits in both areas and measuring the spread of anterograde degeneration to each side of the lesion. In area 17, this spread is always the same whatever the orientation of the fibers with respect to visual field representation. Degenerating fibers are few in number and found mainly in layers I, IVB and VI. In layers IVB and VI they extend for 0.5–1.0 mm. In layer I, some reach as far as 2.0 mm. In area 18, degenerating fibers are more numerous and longer. They are plentiful in layer I, diminish considerably in layer II, increase again in number till the depth of III, are slightly less numerous in layer IV and are again plentiful in layers V and VI. Their length varies with orientation. In a direction corresponding to a visual field sector, they extend for 1.5–2.0 mm, a distance representing only a fraction of the total representation of a sector in the cortex. In a direction corresponding to a visual field zone, they extend further and the combined degeneration of the two sides spans the whole distance of area 18 from the vertical to the horizontal meridian (6 mm). It is suggested that at least some of the fibers of the stria of Gennari subserve binocular interaction and that the differential fiber lengths in area 18 are related to foveal acquisition or to a directional anisotropy of visual movement perception along sector‐zone axes.
Regional variations in glia and neuropil within the hypothalamic ventromedial nucleus
Authors: van Houten Mark , Brawer James R.
Published: January 2005

The normal fine structure of glia and neuropil in the various regional subdivisions of the hypothalamic ventromedial nucleus in the adult male albino rat is described in this report. Although most HVM astrocytes throughout the nucleus appear ordinary in cytology, certain astrocytes found in the posterior ventrolateral subdivision of the nucleus appear somewhat reactive, in that they contain numerous thick fascicles of gliofibrils and pleomorphic dense bodies. The processes of these reactive astrocytes elaborate multiple, concentric lamellae which encapsulate small, round, pyknotic masses (probably degenerate axonal elements). These degenerate profiles, which are greatly outnumbered by normal HVM boutons, may represent synaptic contacts that deteriorate spontaneously in the normal adult HVM. Other signs of spontaneous degeneration occurring within this neuropil include the occasional presence of large masses of necrotic debris which appear engulfed by microglia. These findings suggest the presence in the normal adult HVM neuropil of a low‐grade degenerative process with attendant gliosis, which is topographically centered about the posterior ventrolateral region of the nucleus.

Regions of neuropil containing degenerate boutons also contain altered neuronal processes, some of which may be growth cones. The topographic proximity of the degenerating boutons to possible signs of axonal or dendritic regeneration indicates that certain synaptic circuits in the normal adult HVM may be plastic, and subject to spontaneous remodelling.
Studies of visual function and its decay in mice with hereditary retinal degeneration
Authors: Dräger Ursula C. , Hubel David H.
Published: January 2005

Functional implications of mouse hereditary retinal degeneration have been studied at the level of the superior colliculus and visual cortex in the C57BL/6J‐le rd strain. On autoradiography at a light‐microscopic level, following eye injection with radioactive compounds, central visual structures appeared normal. A slight reduction in ipsilateral retinal projection was probably related to reduced retinal pigmentation associated with the light ear (le) mutation. In recordings from visual cortex and tectum in rd mice older than five months the cells discharged with highly rhythmic maintained activity. This ongoing activity depended on retinal input, since temporary asphyxia of the eye stopped it immediately. The frequency of the rhythm was influenced by the anesthesia. In these older mice no visual receptive fields could be mapped, but in a few tectal recordings it was possible to suppress the maintained activity by diffuse, very intense illumination. As in normal mice, no auditory or somatosensory responses were observed in the visual cortex or upper tectal layers. In recordings from tectum before the age of three weeks retinotopic topography and receptive fields were normal. By day 24 no receptive fields could be recorded from parts of the tectum representing the central 90‐100° of the visual field, whereas within a peripheral ring responses were still roughly normal under photopic conditions. Over the following four months these peripheral responses faded away slowly. Incremental thresholds, especially in the scotopic range, were elevated, rising slowly to unmeasurable values. Similarly during dark adaptation the thresholds fell to values several log units above those reached in normal mice; these values of dark adapted thresholds in rd mice rose with age. This is consistent with morphological changes known to occur in the retina as a consequence, of the rd mutation the rods degenerating before the cones.
Radioautographic investigation of gliogenesis in the corpus callosum of young rats II. Origin of microglial cells
Authors: Imamoto Kikuko , Leblond C. P.
Published: January 2005

Microglial cells are absent from the corpus callosum of newborn rats. In the hope of finding out when and how microglial cells appear with age, 3H‐thymidine was given intraperitoneally as single or three shortly spaced injections to 5‐day‐old rats weighing about 15 g; and these animals were sacrificed at various time intervals from 2 hours to 35 days later. Pieces of corpus callosum were taken near the superior lateral angle of the lateral ventricles; and semithin sections were radioautographed and stained with toluidine blue.

The corpus callosum of 5‐day‐old rats is composed of loosely arranged unmyelinated fibers and scattered cells. Among these cells, microglia are rare; there are a few astrocytes, many immature glial cells, rare pericytes, and 6‐7% of phagocytic “ameboid cells” consisting of a few monocytes and many macrophages. In the animals sacrificed two hours after 3H‐thymidine administration, label is present only in immature cells and “ameboid cells.”

As time elapses and the fibers of corpus callosum become myelinated, oligodendrocytes and, later, microglial cells appear. At the age of 12 days, microglial cells are present in substantial number; and by 19 days, the number doubles to reach a plateau. Many of the new microglial cells are labeled, e.g., 78.1% in 12‐day‐old animals (7 days after 3H‐thymidine administration). The labeled microglial cells must have come from the transformation of cells that acquired label early, that is, from the immature cells or the “ameboid cells.” The height of the peaks of labeling – 59.8% at nine days for immature cells and 77.8% at 12 days for “ameboid cells” – points to the latter as precursors of the highly labeled microglial cells. Furthermore, the “ameboid cells” disappear as microglial cells appear and there are transitional elements between these two cell types. Cell counts suggest that about a third of the “ameboid cells” transform into microglial cells, while the others degenerate and die.

Thus, the microglial cells which appear in the corpus callosum during the first three weeks of life result from transformation of the “ameboid cells” – a group of macrophages showing various stages of transition from monocytes. As for the occasional microglial cell appearing after the third week or in the adult, they presumably come directly from monocytes. In either case, monocytes would be the intial precursors.
Immunohistochemical localization of enkephalin in rat brain and spinal cord
Authors: Sar Madhabananda , Stumpf Walter E. , Miller Richard J. , Chang Kwen‐Jen , Cuatrecasas Pedro
Published: January 2005

The distribution of immunoreactive enkephalin in rat brain and spinal cord was studied by immunoperoxidase staining using antiserum to leucine‐enkephalin ([Leu5]‐enkephalin) or methionine‐enkephalin ([Met5]‐enkephalin). Immunoreactive staining for both enkephalins was similarly observed in nerve fibers, terminals and cell bodies in many regions of the central nervous system. Staining of perikarya was detected in hypophysectomized rats or colchicine pretretated rats. The regions of localization for enkephalin fibers and terminals include in the forebrain: lateral septum, central nucleus of the amygdala, area CA2 of the hippocampus, certain regions of the cortex, corpus striatum, bed nucleus of the stria terminalis, hypothalamus including median eminence, thalamus and subthalamus; in the midbrain: nucleus interpeduncularis, periaqueductal gray and reticular formation; in the hind brain: nucleus parabrachialis, locus ceruleus, nuclei raphes, nucleus cochlearis, nuclear tractus solitarii, nucleus spinalis nervi trigemini, motor nuclei of certain cranial nerves, nucleus commissuralis and formatio reticularis; and in the spinal cord the substantia gelatinosa. In contrast enkephalin cell bodies appear sparsely distributed in the telencephalon, diencephelon, mensencephalon and rhombencephalon. The results of the histochemical staining show that certain structures which positively stain for enkephalin closely correspond to the distribution of opiate receptors in the brain and thus support the concept that the endogenous opiate peptides are involved in the perception of pain and analgesia. The localization of enkephalin in the preoptic‐hypothalamic region together with the presence of enkephalin perikarya in the paraventricular and supraoptic nuclei suggest a role of enkephalin in the regulation of neuroendocrine functions.
The neurological organization of pathways between the dorsal lateral geniculate nucleus and visual cortex in old world and new world primates
Authors: Henderickson Anita E. , Wilson James R. , Ogren Marilee P.
Published: January 2005

Pathways between the dorsal lateral geniculate nucleus (dLGN) and visual cortex in Old World (Macaca, Papio, Erythrocebus, Cercopithecus) and New World (Saimiri, Cebus) primates were studied after injections of horseradish peroxidase and H3 or S35 amino acids into the dLGN or visual cortex. Trans‐synaptic autoradiography was also used to study these pathways after an injection of H3 proline‐fucose into one eye. The subsequent autoradiographs of visual cortex showed that Old World primates have separate eye inputs (ocular dominance columns) in striate cortex, whereas New World monkeys have overlapping or non‐separated eye inputs. In both primate groups the geniculocortical input to layer IVA formed a pattern which resembled a honeycomb in tangential sections, unlike the solidly labeled layer IVC. Also common to the two primate groups was a projection from dLGN to layer VI. There was no dLGN projection to any prestriate area in any of the primates. However, after an injection limited to the prestriate cortex of Macaca, light autoradiographic labeling was seen in the interlaminar zones and the magnocellular and S laminae, demonstrating a prestriate‐dLGN pathway.

Our results indicate that the primate visual system differs significantly from the cat in having no dLGN projection to area 18. There are also significant differences between primates in the level at which the possibility of binocularity (of an excitatory nature) first occurs in the striate cortex because in the species studied thus far with neuroanatomical methods, Old World primates have ocular dominance columns in layer IV but most New World monkeys lack them.
Termination of electroreceptor and mechanical lateral line afferents in the mormyrid acousticolateral area
Authors: Bell Curtis C. , Russell Charles J.
Published: January 2005

The projection regions of electroreceptor and mechanical lateral line afferents in electric fish of the mormyridae family are described.

Electroreceptor afferents from the posterior dorsal skin run in the dorsal branch of the posterior lateral line nerve. Electroreceptor afferents from ventral skin and mechanical lateral line afferents and efferents run in the ventral branch of the nerve. Horseradish peroxidase (HRP) injections into each branch resulted in filling of its central terminals with the marker enzyme. The method yields a Golgi‐like staining of afferent terminals, allowing some aspects of their morphology to be described. Comparison of results from dorsal and ventral branch injections shows the separate medullary regions to which electroreceptor and mechanical afferents project, and also demonstrates four separate somatotopic maps within the electroreceptor region.

Mechanical afferents end predominantly ipsilaterally in nucleus anterior and eminentia granularis as has been suggested by others. Ipsilateral endings in nucleus octavius are also seen. Electroreceptor afferents end exclusively in the cortex and nucleus of posterior lateral line lobe (PLLL). Within the cortex there are three distinct maps of the skin surface which are separated from each other by discontinuities in the cellular layers. Somatotopic mapping is also present in the nucleus of PLLL though it is less precise than in the cortical zones. Large club endings of the cells of this nucleus are filled with HRP. Labeled cells are seen within a small midline nucleus located at the level of the eighth nerve just above the medial longitudinal fasciculus. These are probably the cell bodies of lateral line efferents.
A golgi study on the subthalamic nucleus of the cat
Authors: Iwahori Nobuharu
Published: January 2005

The subthalamic nucleus (ST) of kittens was studied by means of the rapid Golgi silver impregnation method.

The neurons of the ST were classified into three types. Type I neurons, the main constituents of the ST, had oval or polygonal cell bodies with a mean diameter of 26 μm by 36 μm and four to six primary dendrites. Type II neurons had multipolar or polygonal cell bodies, which measured an average 31 μm by 43 μm and emitted four to seven primary dendrites. The cell bodies of the type III neurons were polygonal in shape, measured 23 μm by 26 μm in average and emitted four to six primary dendrites. The dendrite bundle and the dendrite pallisade were observed. Frequently dendrites of the ST extended into the cerebral peduncle (CP), and even cell bodies of some ST neurons were located within the CP. All of the parent axons of the ST neurons coursed rostrally, although intra‐ and extra‐nuclear axon‐collaterals arising from the ST neurons travelled rostrally, caudally or caudomedially.

The afferent fibers to the ST were divided into three groups; afferents via the Meynert's commissure (MC), descending and ascending afferents. The MC fibers, which ran across the CP, gave terminals to the ST. The descending afferents were axon‐collaterals of fibers descending in the CP and those of fibers running through the ST. The ascending afferents were also axon‐collaterals arising from ascending fibers in the CP. In addition to these afferents, many descending and ascending fibers of passage ran through the ST without emitting axon‐collaterals.
Patterns of retinal terminations and laminar organization of the lateral geniculate nucleus of primates
Authors: Kaas J. H. , Huerta M. F. , Weber J. T. , Harting J. K.
Published: January 2005

Autoradiographic tracing procedures have been used to study the organization of retinogeniculate axons in seven primates, i.e., four species of New World monkeys, one species of Old World monkeys and two species of prosimians. These data suggest that the basic primated pattern of geniculate lamination consists of two parvocellular layers, two magnocellular layers, and two poorly developed and highly variable superficial (S) layers which are ventrally lacoted. Ocular input to each member of each of the three pairs differs. In the macaque, the squirrel, and the saki monkey, the parvocellular layers subdivide and interdigitate into four leaflets so as to give the appearance of four parvocellular “layers”. These leaflets are much less extensive in the owl and marmoset monkeys. In some individual macaque monkeys, there is further splitting of the parvocellular leaflets into subleaflets, giving the appearance of six parvocellular “layers”. The prosimians (galago and slow loris) have two additional layers that are not found in pithecoid primates, and only one superficial layer is apparent. The two additional layers are termed “koniocellular” since they consist of very small cells. Finally, New and Old World monkeys have both ipsilateral and contralateral retinal input to the interlaminar zones.

We conclude that the basic pattern of lateral geniculate organization is six layers, but not the traditional six. Prosimians have evolved two additional layers, the koniocellular layers, and have possibly lost one superficial layer. Both New World and Old World monkeys have elaborated the parvocellular layers by forming leaflets to varying extents. With the possible exception of the single S layer in prosimians, layers form pairs that are similar in cell types, but different in ocular input.
The efferent connections of the anterior hypothalamic area of the rat, cat and monkey
Authors: Saper C. B. , Swanson L. W. , Cowan W. M.
Published: January 2005

The general morphology and topographic relations of the anterior hypothalamic area (AHA) in the rat, cat and squirrel monkey have been described, and its efferent connections analyzed autoradiograpically, after small injections of 3H‐labeled amino acids into, or around, the area. In all three species the AHA is rather poorly separated from the surrounding preoptic and hypothalamic areas and nuclei but shows three distinct cellularcondensations, lacated rostrally, and posterodorsally. Closely associated with the AHA are the retrochiasmatic area, the anterior periventricular nucleus and the scattered neurons usually referred to as the accessory supraoptic nucleus.

The AHA has primarily short connections to the adjoining medial preoptic area, the lateral hypothalamic area, the periventricular nucleus, the dorsomedial nucleus, and to the “capsule” of the vertromedial nucleus. However, it also has certain mor4 distantprojections, rostrally to a narrow zone centered in the ventral part of the lateral septal nucleus, and caudally to the dorsal premammillary nuclei, the posterior hypothalamic area and the central gray. There is some evidence to suggest that the various subdivisions of the AHA have different afferent connections. Thus the posterodorsal cell condensation appears to give rise to the bilateral projection to the dorsal premammillary nuclei, while the projections to the septum, the posterior hypothalamic area and the central gray seem to have their origin in the central condensation. Similarly, the retrochiasmatic area sends its efferents through the ventral supraoptic commissure to the amygdala, the anterior periventricular nucleus contributes to the periventricular fiber system and to the external lamina of the median eminence, and the accessory supraoptic neurons project to the internal lamina of the median eminence.
Some features of the spatial organization of the central nucleus of the inferior colliculus of the cat
Authors: Roth G. L. , Aitkin L. M. , Andersen R. A. , Merzenich M. M.
Published: January 2005

A series of neuroanatomical and neurophysiological experiments have been conducted within the central nucleus of the inferior colliculus (ICC) of the cat in order to determine some features of the spatial organization of the nucleus. Results from these experiments have demonstrated: (1) the origins of the auditory brain stem afferents to ICC and the topography of those projections in relation to the cochleotopic organization of ICC; (2) the segregation of at least some of those brain stem projections within ICC; and (3) ICC neurons with similar response properties (response properties which are often similar or identical to those of neurons in brain stem auditory nuclei) are often clustered within the nucleus. These results provide evidence that the laminated division of the ICC probably consists of anatomically, physiologically, and functionally distinct subdivision and that some aspects of auditory sensation may be encoded or represented separately (i.e., in spatially distinct “regions”) within the nucleus.