摘要:

AbstractThe early postnatal development of neuropeptide Y‐containing neurons in the visual cortex of the cat was analyzed. Immunohistochemistry reveals several stages of morphological differentiation and degeneration. Completely undifferentiated neurons have very small somata with nuclei surrounded by a thin rim of cytoplasm and processes unclearly differentiated into dendrites and axons. Processes bear growth cones. Differentiating neurons show an increase in soma size and complexity of processes. Axons are recognizable. Fully differentiated neurons have well‐defined axonal and dendritic patterns. Degenerating neurons are identified by thick, heavily beaded processes covered by hairy appendages and vacuolar inclusions in the somata. Cell death is expressed by shrunken somata and lysed, fragmented processes.According to their postnatal time course of differentiation and/or degeneration, NPY‐immunoreactive neurons, which form several morphological distinct cell types, are grouped into 3 neuronal populations, (1) Pseudopyramidal cells, bitufted “rectangular” cells with wide dendritic fields, unitufted cells, and small multipolar cells are located in the gray matter and have a rather primitive morphology resembling cell types found in lower vertebrate cortex and tectum. They constitute a first transient neuronal population, because all neurons are fully differentiated at birth and become largely eliminated by postnatal day (P) 12. (2) Axonal loop cells are mainly located in the white matter. Their most prominent feature is an often long hairpin loop formed by either the main axon itself or by a major collateral. The axonal branches pass through the cortex to connect the white matter and layer I. Axons do not form local plexuses and terminal elements in the gray matter. Neurons differentiate perinatally, form a first peak from P6 to P10, followed by a decrease in cell number and innervation density at P12, followed by second peak from P15 to P20. After P20 the number of axonal loop cells steadily decreases, and they become eliminated by P48. (3) A third population consists of neurons with a higher degree of axonal ramification and a variety of axonal patterns. Early members are located mainly at the layer VI/white matter border, differentiate during the first postnatal week, and give rise to a diffuse innervations of the gray matter without forming specific terminal elements. Some of the early axonal patterns persist into adulthood, whereas others are not found in the adult brain. Late members of the third population are located mainly in gray matter layers VI and V, and differentiate from P18 onward into short axon basket cells possessing the typical perisomatic terminal bendings. They form the adult fiber and terminal strata until P48. So, the third population comprises transient as well as persisting neurons, and finally it represents the adult neuronal stock.The origin of transient cell types from the cortical subplate, the origin of persisting neurons from the cortical plate, and some functional implications following from these results are

ISSN:0092-7317    

DOI:10.1002/cne.902610202

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe distribution of methionine‐enkephalin‐Arg6‐Gly7‐Leu8, a unique peptide derived from proenkephalin A in the rat brainstem, was studied immunocytochemically by using a highly specific antiserum to this octapeptide sequence.Immunoreactive perikarya with various shapes and sizes were detected in many regions of the rat brainstem. Dense accumulation of immunoreactive perikarya and fibers was seen in the nuclei associated with special sensory and visceral functions, such as the interpeduncular nucleus, the parabrachial nucleus, the nucleus of the solitary tract, and the nucleus of the spinal tract of the trigeminal nerve. Clusters of methionine‐enkephalin‐Arg6‐Gly7‐Leu8–like immunoreactive perikarya and fibers were observed in certain areas considered to play a role in nociception and analgesia, such as the central gray of the midbrain central gray and the raphe magnus nucleus. Some methionine‐enkephalin‐Arg6‐Gly7‐Leu8‐like immunoreactive perikarya were distributed in the lateral reticular nucleus, the nucleus of the solitary tract, and the raphe magnus nucleus, where monoaminergic neurons were also detected. In addition to the previously reported enkephalinergic cells, we found many methionine‐enkephalin‐Arg6‐Gly7‐Leu8containing neurons; the rostral and caudal linear nucleus of raphe, the median raphe nucleus, entire length of the raphe magnus nucleus, the medial longitudinal fasciculus, the cuneate nucleus, the external cuneate nucleus, the gracile nucleus, and the area postrema. The wide distribution of this octapeptide‐like immunoreactivity reflected neurons expressing the preproenkephalin A gene distributed more widely than previously repo

ISSN:0092-7317    

DOI:10.1002/cne.902610203

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractImmunohistochemical methods were used to visualize choline acetyl‐transferase (ChAT)‐, serotonin‐, dopamine‐β‐hydroxylase (DBH)‐, and tyrosine hydroxylase (TH)‐containing fibers in the primary auditory cortex of the cynomolgus monkey (Macaca fascicularis). Each antiserum revealed a subpopulation of axons with a distinct density and laminar distribution. ChAT‐immunoreactive fibers were very dense in superficial layers, particularly in layers I, deep III, and IV, and very sparse in layers V and VI. No immunoreactive cell bodies were evident. Serotonin‐immunoreactive fibers were very dense in all cortical layers but exhibited some subtle laminar differences in fiber size and orientation. The densities of DBH‐ and TH‐immunoreactive fibers were substantially lower than the densities of both ChAT‐ and serotonin‐immunoreactive fibers, particularly in layer IV. However, there were substantial differences between the distribution of TH‐immunoreactive fibers and that of DBH‐immunoreactive fibers. For example, the density of TH‐immunoreactive fibers was substantially greater than that of DBH–immunoreactive fibers in layer I. In addition, TH‐immunoreactive fibers differed from the other three systems in that TH‐immunoreactive fibers exhibited a rostral to caudal gradient of decreasing density.This is the first characterization of the innervation of a specific cortical region by all four of these systems and the first detailed description of the cholinergic innervation of a primate neocortical region utilizing a specific anti‐ChAT antiserum. These striking differences in density and laminar distribution suggest that the subcortical extrathalamic systems furnishing these axons differ significantly in their modulation of cortical auditory processing. These data extend observations of previous studies which revealed that the expansion and specialization of the primate neocortex is accompanied by a pronounced regional and laminar differentiation in the intracortical distribution of these h

ISSN:0092-7317    

DOI:10.1002/cne.902610204

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe morphology of the terminal arborizations in laminae I‐II of primary afferent fibers was studied in sections stained by the heavy metal (nickel and cobalt) intensification of diaminobenzidine (DAB) after crushing one dorsal root with horseradish peroxidase (HRP) crystals, and with the mixed Golgi method which duplicated the staining provided by the first method. Besides the flame‐shaped arbors located in deep lamina IIi as an extension of the arbors of lamina III, which were derived from 1.7‐μm thick stem fibers (probably Aαβ fibers), six types of terminal arbors, all rostrocaudally oriented, arising from fine stem fibers and having preferential locations, were disclosed. The lateral third of laminae I‐II contained a longitudinal plexus of parallel 0.8‐μm thick stem fibers (C fibers) with longitudinal side branches generating many boutons en passant. Laminae I and IIo, in their middle third, contained dichotomizing longitudinal fibers with elongated boutons, arising from 1‐μm thick stem fibers (C or Aδ), and, in the medial third, a dense plexus with terminal networks carrying large boutons, which arose from 1.3‐μm thick stem fibers (Aδ). Fibers ending in terminal bouquets and issuing from 1‐μm thick stem fibers (C or Aδ) occupied the dorsal part of middle and medial lamina IIi, while the intermediate part contained clusters (swarms) of ultrafine boutons arising from extremely fine fibers. The whole medial lamina Hi also contained fine undulating fibers arising from 0.3 μm‐thick stem fibers (C fibers) with large boutons near their ends. The functional meaning of this multiplicity of morphological types and locations is still unclear. It may be clarified when single unit analysis of HRP‐injected fine fibers is made possible, or immunocytochemical stainings disclose the neurotransmitte

ISSN:0092-7317    

DOI:10.1002/cne.902610205

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe rat brain contains a large number of vasopressin (VP) immunoreactive fibers, the sites of origin of which have not yet been established completely. For instance, the sources of VP fiber systems in the amygdala, ventral hippocampus (VH), mediodorsal thalamic nucleus, ventral tegmental area, and dorsal raphe yet remain obscure. These VP fibers may originate in any of the recently described extrahypothalamic VP cell groups, viz., medial amygdaloid nucleus (AME), dorsomedial hypothalamic nucleus, or locus coeruleus, since VP efferents from these cells still remain to be demonstrated. In search of AME VP efferents three approaches were followed: (1) thePhaseolus vulgarisanterograde tracing method, (2) immunocytochemistry after AME lesioning, and (3) retrograde transport of a fluorescent dye in combination with immunofluorescence. The results demonstrate that VP cells in the AME project to (1) the lateral septum (LS) by the ventral amygdalofugal pathway and (2) the VH via the amygdalohippocampal transition zone. In addition, the VP projection from the bed nucleus of the stria terminalis (BST) to the LS was confirmed. There was no indication that VP cells in the AME project through the amygdalotegmental pathway to the medulla oblongata and spinal cord. The results support the possibility that the BST and AME are an anatomical entity that may be part of the central loci controlling sexual processes in the rat.

ISSN:0092-7317    

DOI:10.1002/cne.902610206

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractMethylazoxymethanol (MAM) injected postnatally affects cerebellar development in mice. A single injection at the fifth postnatal day produces hypogranular cerebella whereas a single injection at birth produces, in addition, a disorderly cytoarchitecture of the folium and alteration of Purkinje cell positioning (Bejar et al.: Exp. Brain Res.57:279–285, ′85). In the present study we have used immunohistochemistry with anti‐GABA immune serum and electron microscopy to further characterize these alterations. In addition to the already‐described nonoccupied dendritic spines of Purkinje cells both in mice injected the day of birth and or at the fifth postnatal day, we have observed, in animals injected at birth, the absence of pericellular baskets around Purkinje cells and the presence of heterologous synapses between mossy fibres and Purkinje cell dendrites. These heterologous synapses apparently disappear after postnatal day 20.By using an appropriate timing of MAM injection, different types of hypogranular cerebella, phenocopies of different mutants, can be obtained in large enough number to carry out extensive biochemical studies at each developmen

ISSN:0092-7317    

DOI:10.1002/cne.902610207

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractMotoneuron number in the lumbar lateral motor column of the bullfrog,Rana catesbeiana, was investigated through the course of premetamorphic development and in postmetamorphic frogs. Motoneurons were distinguished on the basis of histological characteristics into two classes, type L (less differentiated) and type M (more differentiated). The number of type L motoneurons on each side showed a precipitous decline between stages V and VI (6,300 to 2,500) and a slower rate of loss until stage XI (to 550). Type M motoneurons increased in number between stages V and VII (560 to 2,775) and declined precipitously between stages VII and VIII to a value similar to that of juvenile frogs (1,100). These changes in motoneuron number do not correspond to the formation of myotubes or to the appearance of contractile properties in hindlimb muscles. The development of myotubes in the hind‐limb occurs only after total motoneuron number has declined by 35%. Similarly, hindlimb muscle contraction develops after the early decline in type L motoneuron number and is restricted to proximal thigh at the peak of type M motoneuron number.In postmetamorphic frogs, a weak (r = 0.44) but statistically significant correlation was found between type M motoneuron number and body length. In the largest frogs (greater than 15 cm body length), 1262 ± 157 (mean ± s.d.) motoneurons were present, whereas the smallest frogs (less than 5 cm body length) had 1099 ± 98 motoneurons. These results are not consistent with previous findings that the variance of motoneuron number among small frogs is greater than that among larger frogs. The present results are thus inconsistent with explanations of size‐related differences in motoneuron number that are based on selection of small frogs with greater number of motoneurons for survival. The increase in motoneuron number may be due to a slow addition of newly born motoneurons to the LMC or to the differentiation of existing motoneurons. The latter possibility is supported by the finding that the number of presumptive type L profiles is less in larger

ISSN:0092-7317    

DOI:10.1002/cne.902610208

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractWe have mapped out the ectosylvian visual area (EVA) of the cat in a series of single‐ and multiunit recording studies. EVA occupies 10–20 mm2of cortex at the posterior end of the horizontal limb of the anterior ectosylvian sulcus. EVA borders on somatosensory cortex anteriorly, auditory cortex posteriorly, and nonresponsive cortex laterally. EVA exhibits limited retinotopic organization, as indicated by the fact that receptive fields shift gradually with tangential travel of the microelectrode through cortex. However, a point‐to‐point representation of the complete visual hemifield is not present.We have characterized the afferent and efferent connections of EVA by placing retrograde and anterograde tracer deposits in EVA and in other cortical visual areas. The strongest transcortical fiber projection to EVA arises in the lateral suprasylvian visual areas. Area 20, the granular insula, and perirhinal cortex provide additional sparse afferents. The projection from lateral suprasylvian cortex to EVA arises predominantly in layer 3 and terminates in layer 4. EVA projects reciprocally to all cortical areas from which it receives input. The projection from EVA to the lateral suprasylvian areas arises predominantly in layers 5 and 6 and terminates in layer 1. EVA is linked reciprocally to a thalamic zone encompassing the lateromedial‐suprageniculate complex and the adjacent medial subdivision of the latero‐posterior nucleus.We conclude that EVA is an exclusively visual area confined to the anterior ectosylvian sulcus and bounded by nonvisual cortex. EVA is distinguished from other visual areas by its physical isolation from those areas, by its lack of consistent global retinotopic organization, and by its placement at the end of a chain of areas through which information flows outward from the primary vi

ISSN:0092-7317    

DOI:10.1002/cne.902610209

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe development of synapses in the molecular layer of the rat piriform cortex was studied at embryonic days 15, 17, 19, and 21. The present study has sought to extend past studies of synaptogenesis by identifying not only changes in numbers of synapses, but also changes in numbers of potential precursors of synapses. A stereological method (Cruz‐Orive, ′80) was used to make volumetric estimations of the numbers of synapses, axonal puncta, vesicle‐associated puncta, and unapposed postsynaptic specializations. This stereological method was preferred to other morphometric methods because it is not influenced by changes in the size, shape, or orientation of the structures of interest. This was considered important since such changes might be expected during development.Large numbers of unapposed axonal specializations (axonal puncta and vesicle‐associated puncta) were found in all three sublaminae (lateral olfactory tract, Ia, and Ib) at all ages. The numerical density (number per unit volume of neuropil) and relative frequency of these structures changed significantly with time. In all three sublaminae, these changes were associated with changes in the number of synapses, although the numerical density and relative proportions varied between the sublaminae. These results suggested that axonal puncta could accumulate vesicles, thus becoming vesicle‐associated puncta, and that vesicle‐associated puncta could contact dendrites, thus forming synapses. In contrast, the numerical density of lone postsynaptic specializations remained low and no significant changes in their relative proportion in the population were found. This suggested that although lone postsynaptic sites were observed, they did not appear to play a major role in synaptogenesis in this region of the cortex. In addition to documenting developmental differences between the three sublaminae in the molecular layer, the results support a synaptogenic hypothesis in which the axon can form surface specializations that appear to be involved in synaptogenesis, independent of direct dendri

ISSN:0092-7317    

DOI:10.1002/cne.902610210

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractIn this report, we describe a new colloidal‐gold‐labelled retrograde tracer, wheat germ agglutinin (WGA) conjugated to enzymatically inactive horseradish peroxidase (apoHRP). This protein gold complex (WGAapoHRP‐Au) is a sensitive marker for retrograde tracing of the projections of CNS neurons at the light‐microscopic (LM) level when a silver‐enhancement procedure is used to detect the gold in the tracer. For electron‐microscopic (EM) analysis, the silver‐enhanced sections undergo a further gold‐toning step. This protects against rapid oxidation and dissolution of the silver precipitate during the osmication procedure.A major advantage of WGAapoHRP‐Au is that it can be used in a variety of multiple‐labelling studies. When the retrograde transport of the new tracer is combined with that of the fluorescent dye, True Blue, neurons that have bifurcating axons can be readily demonstrated. Simultaneous immunofluorescent detection of the cytochemistry of the double‐retrogradely labelled neurons is also possible. In contrast to a WGA‐HRP gold complex, the new complex has no enzymatic activity. Thus HRP‐based techniques (e.g., anterograde transport of WGA‐HRP or peroxidase‐antiperoxidase immunocytochemistry) can be performed on tissue that contains retrogradely labelled neurons marked with WGAapoHRP‐Au without having to pretreat tissue so as to destroy endogenous HRP enzyme activity. At the EM level, the gold is readily distinguished from DAB immunoreaction product. This makes both LM and EM double‐labelling studies possible.The great sensitivity of the new tracer, its compatibility with a variety of aldehyde fixatives, its ease of detection, and the fact that it can be simultaneously used with several fluorescent and HRP‐based immunocytochemical and tracing techniques make WGAapoHRP‐Au a valuable tool for LM and EM characterization

ISSN:0092-7317    

DOI:10.1002/cne.902610211

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY