摘要:

AbstractWe have examined the number and distribution of dying cells in the developing inner (INL) and outer (ONL) nuclear layers of sectioned quokka retinae (N = 31) from embryonic day (E)24 to postnatal day (P)192.Before birth, dying cells were seen in the optic fissure. Thereafter two major phases of cell death took place in the INL. The first phase was more pronounced within the vitread part with peak numbers of dying cells at P50. By contrast, during the second phase, cell death was more extensive in the sclerad portion; peak numbers of dying cells were recorded at P85 and P100 for the vitread and sclerad parts respectively. At these stages, photoreceptors were seen in the INL suggesting that these ectopic cells contribute to the pool of dying cells. The pattern of cell death broadly followed a central to peripheral sequence in the first phase but, in the second, was seen initially in midtemporal retina and then became panretinal. Dying cells were seen in the ONL but in smaller numbers than in the INL. There was a peak of cell death at P26 which may represent death of mitotic cells at the ventricular surface.In the quokka, retinal cell genesis takes place in two phases (Harman and Beazley:Neuroscience 28:219–232, ′89). The two major phases of cell death described here peak approximately 40 days after episodes of maximal cell genesis. These findings, together with data for the mouse, suggest that a biphasic pattern of cell genesis and cell death may be a feature of eutherian as well as marsupial retinal developm

ISSN:0092-7317    

DOI:10.1002/cne.902890102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractIn this work we examined the neuronal input to one of the serotoninergic centers in the brain, median raphe nucleus (MR). Special consideration is given to projections of the hypothalamus. To describe the afferents to MR, a retrograde transport technique was used after microinjection of WGA‐apoHRP‐Gold complex under pressure and subsequent gold‐silver intensification on formaldehyde‐fixed rat brain sections. Optimal conditions were obtained when the coordinates of the injection site were A ± 1.5, L ± 0.15, and H ± 2.7 according to Paxinos and Watson (The Rat Brain in Stereotaxic Coordinates.New York: Academic Press, '82). Results obtained under these conditions show a heterogeneous distribution of labeled neurons throughout the brain, including a large proportion (±65%) of hypothalamic neurons. Extrahypothalamic neurons projecting to MR were from the prefrontal cortex, lateral and medial habenular nuclei, the pontine area of the central grey, interpeduncular nucleus, dorsal raphe nucleus, oculomotor and trochlear nuclei, dorsal and laterodorsal tegmental nuclei, parabrachial nuclei, and lateral and interpositus cerebellar nuclei. Hypothalamic neurons connected to MR were found to be from medial and lateral preoptic areas, lateral hypothalamus, dorsomedian nucleus, the perifornical area, and the complex of mammillary bodies. Many other discrete regions contained different densities of labeled perikarya: the medial preoptic nucleus, paraventricular nucleus, retrochiasmatic area, arcuate nucleus, lateral magnocellular nucleus, and the posterior area. The MR appears as an integrative center receiving many neuroanatomically and functionally heterogeneous inputs from the

ISSN:0092-7317    

DOI:10.1002/cne.902890103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe organization of the dopaminergic mesostriatal fibers and their patterns of innervation of the basal ganglia in the squirrel monkey (Saimiri sciureus) were studied immunohistochemically with an antiserum raised against tyrosine hydroxylase (TH). Numerous fibers arose from midbrain TH‐positive cell bodies of the substantia nigra pars compacta (group A9), the retrorubral area (group A8), and the lateral portion of the ventral tegmental area (group A10). These fibers accumulated dorsomedially to the rostral pole of the substantia nigra where they formed a massive bundle that coursed through the prerubral field and ascended along the laterodorsal aspect of the medial forebrain bundle in the lateral hypothalamus. Some ventrally located fibers ran throughout the rostrocaudal extent of the lateral preopticohypothalamic area and could be followed up to the olfactory tubercle, whereas other fibers turned laterodorsally to invade the head of the caudate nucleus. At more dorsal levels in the lateral hypothalamus, many fiber fascicles detached themselves from the main bundle and swept laterally to reach the globus pallidus, the putamen, and the amygdala. Several TH‐positive fibers coursed along the dorsal surface of the subthalamic nucleus, and some invaded the dorsomedial third of this structure. The remaining portion of the subthalamic nucleus contained relatively few TH‐positive elements. In contrast, the globus pallidus received a dense dopaminergic innervation deriving mostly from two fascicles that coursed backward along the two major output pathways of the pallidum: the lenticular fasciculus caudodorsally and the ansa lenticularis rostroventrally. At the pallidal level, the labeled fibers merged within the medullary laminae and arborized profusely in the internal pallidal segment and less abundantly in the external pallidal segment. However, the caudoventral portion of the external pallidum displayed a dense field of TH‐positive axonal varicosities. Other fibers ran through the dorsal two‐thirds of the external pallidum en route to the putamen. The striatum contained a multitude of thin axonal varicosities among which a few long and varicosed fibers were scattered. These immunoreactive neuronal profiles were rather uniformly distributed along the rostrocaudal extent of the striatum but appeared slightly more numerous in the ventral striatum than in the dorsal striatum. The pattern of distribution of the TH‐positive axonal varicosities in the dorsal striatum was markedly heterogeneous: it consisted of typical zones of poor TH immunoreactivity lying within a matrix of dense terminal labeling. These zones of weak immunostaining were particularly obvious in the head of the caudate nucleus and dorsal portion of the putamen and their cross‐sectional areas ranged from 0.4 to 1.2 mm2. A few small zones of intense TH immunoreactivity were also noticed in the ventrolateral portion of the putamen. These findings reveal that the dopa‐minergic mesostriatal neuronal system is particularly well developed in the squirrel monkey and that its terminal arborization in the striatum respects the well‐established patch and matrix compartments. In additions, distinct fasciles of the mesostriatal system densely innervate the internal pallidum allowing the midbrain dopaminergic neurons to directly influence the output neurons of the basal ga

ISSN:0092-7317    

DOI:10.1002/cne.902890104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe projections to the basis pontis from cytoarchitectonically defined subregions of the superior (SPL) and inferior (IPL) parietal lobules were investigated in 14 rhesus monkeys by using the anterograde tracing techniques of autoradiography and horseradish peroxidase histochemistry. The results of our study confirm and complement available information regarding the parietopontine projections. The projections are found in clusters distributed in lamellae approximately concentric to the peduncle. They are directed most heavily towards the peripeduncular and lateral nuclei of the pons. There are also lesser, but nevertheless substantial projections to other nuclei including the intrapeduncular, ventral, dorsolateral, extreme dorsolateral, and dorsal nuclei. The dorsomedial, paramedian, and NRTP nuclei receive only minor projections. The SPL projections are relatively widespread with respect to the more focussed IPL projections. The IPL projections are, in general, situated more laterally and at more rostral levels of the pontine nuclei than are those of the SPL.The sulcal cortex of the SPL (area PEa) favors the dorsolateral, extreme dorsolateral, and ventral nuclei compared to the light projections to these nuclei from the convexity of the SPL. The sulcal cortex of the IPL, area POa, differs from the gyral cortex in favoring the ventral and extreme dorsolateral nuclei. The rostral IPL differs from the caudal IPL in that the intrapeduncular nucleus receives projections only from rostral regions, while the lateral nucleus receives projections preferentially from caudal regions. The pontine projections from the medial SPL, area PGm, are unique in the parietal lobe in that they include the paramedian nucleus. Projections arising from multimodal regions located caudally in the SPL (areas PEa and PGm) and IPL (areas PG and Opt) are more strongly represented and more laterally placed within the pontine nuclei than projections arising from more rostral, unimodal, posterior parietal regions.The heavy projections to the pontine nuclei from the posterior parietal cortex, and particularly from those caudal parietal regions that have prominent associative and limbic connections, seem to suggest that the corticopontocerebellar pathways permit a cerebellar contribution not only to the coordination of movement, but also to the modulation and integration of higher function.

ISSN:0092-7317    

DOI:10.1002/cne.902890105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractCoronal sections of the cerebral wall from developing ferrets (newborn to adult) were double‐stained with antibodies to vimentin and glial fibrillary acidic protein (GFAP). At birth, the dominant glial population was radial glia and these cells labeled only for vimentin. A small population of immature astrocytes in the cortical plate was double labeled for GFAP and vimentin. In successive days, the number of vimentin‐positive radial glia gradually decreased and they disappeared entirely at about 21 days. During this same period, the double‐stained astrocytes increased in number and were distributed throughout the cortical plate and intermediate zone. After 6 weeks of age the astrocytes were mostly confined to the developing white matter. Around this time they gradually lost their vimentin staining, and in the adult no vimentin‐positive elements were seen except at the ependymal surface.In newborn ferrets single radial glial cells were also visualized by applying the carbocyanine dye DiI onto the pial surface of fixed brains. While most radial glia extended from the ventricular zone to the pial surface, a substantial fraction of them had lost their contact to the ventricular zone. Their somata were displaced into the subventricular zone and lower portion of the intermdiate zone.The possibility that radial glia transform into astrocytes was directly tested by injecting fluorescent dyes under the pial surface of newborn ferrets at a time when virtually no GFAP‐positive astrocytes are present. The tracer, which was taken up in the upper portion of the cortical plate, stained the radial glial cell somata in the ventricular zone in a similar way as the dye DiI did in the fixed brains. As the radial glial cells disappeared at successively longer survival times, the tracer was ultimately found within newly formed GFAP‐positive astrocytes. These results provide strong support for the hypothesis that radial glia cells are the immature form of astrocytes (Choi and Lapham:Brain Res.148:295–311, ′78; Schmechel and Rakic:Anat. Embryol. (Berl.) 156:115–152, ′79), and also show that, at least in the ferret cortex, the transformation is accompanied by a change in the expression of intermedia

ISSN:0092-7317    

DOI:10.1002/cne.902890106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractIt is possible that the reported effects of early life undernutrition on brain morphology may be due to alterations in mother‐infant interactions and not directly to undernutrition. We have investigated this possibility by comparing artificially reared with mother‐reared rats. Four groups of black‐and‐white hooded male rats were reared. These consisted of mother reared control (MRC), mother reared undernourished (MRU), artificially reared control (ARC) and artificially reared undernourished (ARU). Artificially reared rats were raised in isolation away from their mothers from 5 to 21 days of postnatal age. They were fitted with a gastric cannula through which 'milk' was infused automatically. The period of undernutrition lasted from 5 to 25 postnatal days, following which the animals were fedad libitumuntil 312 days of age. Rats from each group were then killed by perfusion with buffered 2.5% glutaraldehyde. Pieces of visual cortex from each rat were postfixed in osmium tetroxide and embedded in resin. Stereological procedures at the light and electron microscopical levels were used to estimate the synapse‐to‐neuron ratios in cortical layers II to IV.Both MRC and ARC rats had about 7000 synapses per neuron. However, this ratio was about 8300 in MRU rats whilst it was only about 5000 in ARU animals. The rearing x nutrition interaction was statistically significant at the 0.1% level. These changes in the synapse‐to‐neuron ratio were mainly due to alterations in the numerical densities of the synapses rather than that of neurons.These results demonstrate that environmental isolation, as a result of artificial rearing procedures, and concurrent undernutrition during the first three weeks of postnatal life, interact with one another to produce marked morphological changes in the adult rat brain. However, environmental isolation was not, by itself, sufficient to cause permanent changes in interneuron

ISSN:0092-7317    

DOI:10.1002/cne.902890107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe morphology and distribution of dopaminergic interplexiform cells were analyzed in 9‐day‐old rat retinas processed as wholemounts for tyrosine hydroxylase immunohistochemistry. The mean number of dopaminergic interplexiform cells was estimated as about half of the total number of dopaminergic neurons in the immature retina, with a higher density in the temporal retina. Four interplexiform cells were individually analyzed and reconstructed with a computer system. Their arborizations could be divided into three different regions based on both their morphological features and their position within the retinal layers: (1) an internal arborization, spreading at the margin between the inner nuclear layer and the inner plexiform layer, composed of long, thick, somatofugal dendrites branching at acute angles, (2) an external arborization in the middle of the inner nuclear layer, formed by short, thin, varicose, recurved axon‐like processes branching at right angles, (3) and one or more scleral process(es), originating either from the cell body or from the internal arborization, running toward the outermost cell row of the INL, some of which reached the outer plexiform layer. Finally, analysis of the arborization network by computer simulations based on the 4 digitalized cells was compared with a nearest‐neighbour analysis of cell body distribution. It showed that cell bodies are almost randomly distributed—at least in the inferior retina—but that an adjustment of dendritic growth and orientation probably occurs to ensure a homogeneous coverage of the retina with a constant degree of overlap in the adult. This report represents the first three‐dimensional computer reconstruction of chemically identified neurons

ISSN:0092-7317    

DOI:10.1002/cne.902890108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe location of substance P (SP) in the lateral cervical nucleus (LCN) of monkeys (Aotus trivirgatus), cats, and rats was investigated with immunohistochemical methods. Light microscopic analysis showed that SP‐positive fibers and terminals are evenly distributed throughout the LCN of the monkey and rat, whereas the SP labeling in the LCN of the cat is concentrated in the medial part of the nucleus, with only very sparse labeling in the lateral part. Electron microscopic examination of the monkey LCN revealed the presence of SP‐like immunoreactivity within terminal boutons and unmyelinated axons. The SP‐positive boutons are in synaptic contact with dendrites and, occasionally, cell bodies; they contain densely packed, clear, round synaptic vesicles, as well as dense‐core vesicles.The distribution of SP‐like immunoreactivity in the LCN of monkeys, cats, and rats is similar to that of nociceptive‐responsive neurons demonstrated in electrophysiological experiments. The possible role of the SP‐containing fibers in the transmission of nociceptive information through the LCN

ISSN:0092-7317    

DOI:10.1002/cne.902890109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractWe describe, for the first time in insects, the presence of serotonin‐like immunoreactive dorsal unpaired median (DUM) neurons. In unfed, untreatedRhodnius prolixus, the cell bodies of these DUM neurons displayed only faint serotonin‐like immunofluorescence without any detectable fluorescence in the axons. There was, however, an extensive serotonin‐like immunoreactive peripheral complex. We have enhanced the immunostaining of the cell bodies and axons of these DUM neurons by using 5,7‐dihydroxytryptamine (5,7‐DHT) and nerve transection, and have further defined their morphology with cobalt backfilling and Lucifer yellow injection.Injection of 5,7‐DHT resulted in enhanced serotonin‐like immunostaining, after 24 hours, of five DUM neurons in the mesothoracic ganglionic mass. Each DUM neuron possessed bifurcating serotonin‐like immunoreactive axons projecting to the periphery via one of the five bilaterally paired abdominal nerves. Concomitant with the enhanced immunostaining in the cell body and axons of these DUM neurons was the depletion of a serotonin‐like immunoreactive neurohaemal area lying on each of the abdominal nerves and the depletion of serotonin‐like immunoreactive processes on the body wall. Enhancement of cell body and axon immunostaining was also observed in preparations in which the abdominal nerves had been transected 24 hours previously.The location and morphology of these DUM neurons were studied in further detail by using cobalt backfilling of the abdominal nerves and intracellular injection of Lucifer yellow followed by immunohistochemistry. The five serotonin‐like immunoreactive DUM neurons were found to represent a sub‐population in a group of ten DUM neurons located in the mesothoracic ganglionic mass and associated with the abdominal nerves. Each abdominal nerve received projections from two DUM neurons, only one of which was serotonin‐like immunoreactive.Electrophysiological recordings revealed that the serotonin‐like immunoreactive DUM neurons ofRhodniushad similar properties to previously described octopaminergic DUM neurons of insects.The five DUM neurons inRhodniusappear to represent a subpopulation of DUM n

ISSN:0092-7317    

DOI:10.1002/cne.902890110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractPAP immunocytochemistry with an antiserum against serotonin (5‐HT)‐glutaraldehyde‐protein conjugate (kindly donated by M. Geffard) was used to analyze the ultrastructural relationships of 5‐HT axon terminals (varicosities) in the frontal (Fr1‐Fr2), parietal (Par1), and occipital (Oc1M‐Oc2) cortex of adult rats. One hundred‐forty‐five immunostained varicosities from Fr1‐Fr2 (54 from layers I‐II; 91 from layer VI) and 97 each from the upper layers (I‐II) of Par1 and OcM1‐Oc2 were examined in groups of serial thin sections (mean number of sections in series: 3.2 to 7.3). These terminals were of comparable shape and size in the 4 cortical sectors examined, and averaged 0.66 ± 0.2 μm in mean diameter. The proportion of varicosities engaged in synaptic contact was evaluated by linear transformation of the relationship between the frequency of observed synaptic junctions and the number of thin sections available for examination. Reliability of the sampling was evidenced by a high coefficient of correlation (r>0.95) in each cortical sector. The synaptic incidence extrapolated for whole varicosities ranged from 28% (layer VI of Fr1‐Fr2) to 46% (Par1), without statistically significant differences between the 4 sectors examined. The interregional mean could thus be evaluated at 38%. The synaptic 5‐HT terminals always made asymmetrical junctions, which were exclusively found on dendritic spines and shafts, and appeared more frequent on spines than shafts in the deep frontal and the upper occipital cortex. In all 4 sectors, dendritic shafts and spines and other axonal varicosities were frequently encountered in the immediate microenvironment of the immunostained varicosities. It is concluded that the cortical 5‐HT innervation is predominantly nonjunctional throughout the neocortex of the adult rat, which reinforces earlier views of a highly divergent afferent system with particular functional properties and perhaps capable of widespread, global and/or sustained influ

ISSN:0092-7317    

DOI:10.1002/cne.902890111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY