ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00768.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractWe measured the regional cerebral oxidative metabolism (rCMRO2) with positron emission tomography in normal healthy volunteers in three different stages: rest, tactile learning, and tactile recognition of complicated geometrical objects. The frequency of manipulatory movements during tactile recognition was twice that of tactile learning. Tactile recognition with the right hand increased rCMRO2in six prefrontal cortical areas, bilaterally in the supplementary motor areas, the premotor areas and supplementary sensory areas, in the left primary motor and primary sensory area, in the left anterior superior parietal lobule, bilaterally in the secondary somatosensory area, the anterior insula, lingual gyri, hippocampus, basal ganglia, anterior parasagittal cerebellum, and lobus posterior cerebelli. These structures have in other studies been found to participate in manipulatory movements and analysis of somatosensory information. Tactile learning increased rCMRO2in the same structures as did tactile recognition. Thus we found no differences in the anatomical structures participating in storage and retrieval. However the rCMRO2increases in the left premotor cortex, supplementary motor area, and left somatosensory hand area were larger during tactile recognition in accordance with the higher frequency of manipulatory movements and higher flux of somatosensory information from the periphery during recognition. Despite this the rCMRO2was significantly higher in the neocerebellar cortex during tactile learning. Since there were no learning effects on the manipulatory movements, this extra metabolic activity in the lateral cerebellum was attributed to energy demanding processes associated with climbing fibre activity during storage of somatosensory information.

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00769.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractA peripheral nerve exudate, collectedin situfrom the proximal end of a severed rat sciatic nerve, can induce substantial axonal elongation from ganglion cells when tested on explanted adult rat retinae. The responsive cells are identified on the basis of their Thy 1.1 immunostaining properties. Similar outgrowth can be obtained from explants when the culture medium is supplemented with brain‐derived neurotrophic factor (BDNF). In addition, both BDNF and the sciatic nerve exudate can prevent ganglion cell degeneration as shown by the retrograde transport of a fluorescent dye that had been applied to the superior colliculus prior to explantation. The results demonstrate that soluble components, released by lesioned peripheral nerves, can effect adult retinal ganglion cells in a way that is reminiscent of that which has been describedin vivousing sciatic nerve grafts after sectioning of the optic nerve. The molecular nature of these components is discusse

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00770.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractWallerian degeneration of the distal stump of a severed peripheral nerve involves invasion by myelomonocytic cells, whose presence is necessary for destruction of myelin and for initiating mitosis in Schwann cells (Beuche and Friede, 1984). Degeneration of the distal ends of the axons themselves is assumed to occur by autolytic mechanisms. We describe a strain of mice (C57BL/6/Ola) in which leucocyte invasion is slow and sparse. In these mice, confirming Beuche and Friede, myelin removal is extremely slow. A new finding is that axon degeneration is also very slow. This is a consequence of lack of recruitment of myelomonocytic cells for if such recruitment is prevented in other mouse strains by a monoclonal antibody against the complement type 3 receptor (Rosen and Gordon, 1987) axon degeneration is again slowed. We have also, surprisingly, found that nerve regeneration in the C57BL/6/Ola mice is not impeded by the presence of largely intact axons in the distal stump and absence of recruited cells, myelin debris and the absence of Schwann cell mitosis.

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00771.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractDegenerative changes in the forebrain cholinergic nuclei have been studied morphometrically in behaviourally characterized aged female Sprague‐Dawley rats. In all regions analysed (medial septum, diagonal band of Broca, nucleus basalis, and striatum) the acetylcholinesterase‐positive neurons were reduced in both size and number in the aged (24‐months‐old) rats as compared to the young (3‐months‐old) controls. The overall reduction in cell size amounted to between 20 and 30% and the overall reduction in cell number to between 27 and 45%. Impairment in learning and/or memory performance in the aged rats, as assessed in the Morris' water‐maze task, was significantly correlated with both cholinergic cell size and cell number in the medial septum, and with cholinergic cell number in the diagonal band of Broca and in the striatum. In the nucleus basalis there was a trend in the same direction but it did not reach significance. In contrast to these degenerative changes in the cell body regions, no significant differences in cortical or hippocampal choline acetyltransferase activity were detected biochemically between the young and the aged rats, and the enzyme activity levels did not correlate with the degree of behavioural impairment in the aged rats.The present results provide evidence that all major forebrain cholinergic cell groups undergo degenerative changes with age in the rat, and that the most severe changes are found in those rats which display the most profound spatial learning impairments. Despite the severe changes at the cell body level, however, the choline acetyltransferase activity in the cortical projection areas are affected only to a minor degree, perhaps as a result of functional compensatory changes at the t

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00772.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractAdministration of convulsant drugs causes the rapid induction ofc‐fosin identified neurons within the mouse central nervous system (Morgan et al., 1987). In particular, Fos‐like immunoreactivity is evident in nuclei of granule cells of the hippocampal dentate gyrus within 30 minutes of the onset of seizure. By immunoelectron microscopy, Fos antibody binding was exclusively localized to dispersed chromatin (euchromatin) of several types of projection neurons and local circuit neurons in various brain regions and especially in the dentate gyrus, 210 minutes after a single injection of Metrazol. Fos‐like immunoreactivity was not detectable in the nucleolus, nor in the characteristic peripheral and nucleolus‐associated heterochromatin of hippocampal granule cells. No immunostaining was observed in nuclei of glial, ependymal or endothelial cells, and no cytoplasmic reactivity was seen in any cell type. These findings support a role for Fos in stimulus‐response coupling at the level of transcriptional regulation i

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00773.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Abstract1In order to determine whether the responsiveness of neurons in the caudolateral orbitofrontal cortex (a secondary cortical gustatory area) is influenced by hunger, the activity evoked by prototypical taste stimuli (glucose, NaCl, HCl, and quinine hydrochloride) and fruit juice was recorded in single neurons in this cortical area before, while, and after cynomolgous macaque monkeys were fed to satiety with glucose or fruit juice.2It was found that the responses of the neurons to the taste of the glucose decreased to zero while the monkey ate it to satiety during the course of which his behaviour turned from avid acceptance to active rejection.3This modulation of responsiveness of the gustatory responses of the neurons to satiety was not due to peripheral adaptation in the gustatory system or to altered efficacy of gustatory stimulation after satiety was reached, because modulation of neuronal responsiveness by satiety was not seen at earlier stages of the gustatory system, including the nucleus of the solitary tract, the frontal opercular taste cortex, and the insular taste cortex.4The decreases in the responsiveness of the neurons were relatively specific to the food with which the monkey had been fed to satiety. For example, in seven experiments in which the monkey was fed glucose solution, neuronal responsiveness decreased to the taste of the glucose but not to the taste of blackcurrant juice. Conversely, in two experiments in which the monkey was fed to satiety with fruit juice, the responses of the neurons decreased to fruit juice but not to glucose.5These and earlier findings lead to a proposed neurophysiological mechanism for sensory‐specific satiety in which the information coded by single neurons in the gustatory system becomes more specific through the processing stages consisting of the nucleus of the solitary tract, the taste thalamus, and the frontal opercular and insular taste primary taste cortices, until neuronal responses become relatively specific for the food tasted in the caudolateral orbitofrontal cortex (secondary) taste area. Then sensory‐specific satiety occurs because in this caudolateral orbitofrontal cortex taste area (but not earlier in the taste system) it is a property of the synapses that repeated stimulation results in a decreased neuronal response.6Evidence was obtained that gustatory processing involved in thirst also becomes interfaced to motivation in the caudolateral orbitofrontal cortex taste projection area, in that neuronal responses here to water were decreased to zero while water was drunk until satiety was produ

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00774.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe pathway from the mamillary complex to the cerebellum via the pontine nuclei has been studied using several anterograde and retrograde tracing techniques in the cat. We have also compared the pontine terminal regions of fibres from the mamillary complex and from the cingulate gyrus.Implantations of crystalline horseradish peroxidase wheat germ agglutinin (HRP‐WGA) in the mamillary complex and lesions of the cingulate gyrus were combined in the same animal with injections of HRP‐WGA, rhodamine‐B‐isothiocyanate (RITC), and Fluoro‐Gold in different parts of the cerebellar hemisphere.Fibres from both the mamillary complex and the cingulate gyrus terminate mainly within a transversely oriented, c‐shaped band in the ipsilateral, rostral pontine nuclei. Within this band the terminal fields of fibres from the mamillary complex and the cingulate gyrus form a mosaic‐like pattern of partly overlapping patches. Pontine regions receiving a mamillary input project mainly to the ventral paraflocculus, and to a lesser degree to the dorsal paraflocculus, but apparently not to the uvula or crus II. Judging from the literature it seems highly unlikely that other parts of the cerebellar hemispheres receive projections from these pontine regions. Fibres from the ventral paraflocculus were shown to terminate in the parvicellular part of the lateral cerebellar nucleus only.The present findings would seem to imply that inputs from the mamillary complex and a related cortical region, the cingulate gyrus, are partly integrated, partly kept separate at the precerebellar level. This would ensure that small groups of cells in the rostral pontine nuclei receive a specific set of afferents. Conceivably, the information transmitted to the cerebellum by these groups of pontine cells might be related to functions of the mamillary complex, such as learning, motivation, and s

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00775.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper examines the organization of host afferents within cerebellar grafts implanted into kainic acid lesioned cerebellum. Our selection of a cerebellum, a prime example of a ‘point‐to‐point’ system, permits precise determination of the degree and the specificity of host‐graft interactions.One month after a cerebellar injection of kainic acid, the lesion produced can be divided into two concentric regions: (i) a central necrotic zone, totally depleted of neurons (zone 1), and (ii) a peripheral zone which lacks all Purkinje cells but preserves its cortical lamination (zone 2). Two months after the implantation of solid pieces of embryonic cerebellum, the graft has evolved into a minicerebellar structure, occupying most of zone 1. The grafted minicerebellum consists of a highly convoluted trilaminated cortex with a core containing deep nuclear neurons. Purkinje cells are positioned between the molecular and granular layer with their short and irregular dendrites branching within the former. Donor foetal Purkinje cells migrate into the contiguous portion of the molecular layer of the host zone 2. These embryonic neurons set up within the upper three‐quarters of the host molecular layer, and develop monoplanar dendritic trees that span the whole width of the layer.The organization of host‐graft interactions was studied by autoradiography of anterogradely transported tritiated leucine, injected in the host bulbar region containing the caudal half of the inferior olivary complex (origin of all vermal climbing fibres) and the dorsally adjacent paramedian reticular nucleus (origin of a few mossy fibres). Numerous labelled fibres cross the host‐graft interface from the white matter of the host cerebellum, and provide innervation to the minicerebellar structure. The vast majority of these labelled axons terminate in the molecular layer, forming axonal arborizations that follow the shape of the Purkinje cell dendrites. The labelled climbing fibres are organized into uneven sagittally aligned strips, which mimic that of olivocerebellar projections in control rats. Only a small proportion of host labelled fibres end in the donor granular layer, forming typical mossy fibre rosettes. The latter are present in the region of the graft close to the host‐graft interface. In addition, labelled axons are observed climbing over the dendritic trees of grafted Purkinje cells that have invaded a portion of the host molecular layer of zone 2. In all regions containing grafted Purkinje cells and labelled climbing fibres, the density of the innervation is close to normal with practically all Purkinje cells receiving a climbing fibre.The extensive integration of the grafted cells into the deficient neuronal networks of the host clearly illustrates the positive neurotropic effect exerted by immature cerebellar neurons on adult extracerebellar afferent fibres. The hodological integration, allowing a possible restoration of the impaired cerebellar circuitry, takes place respecting the specificity and topographic distribution which characterize the ‘point‐to‐point’ arrangement of no

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00776.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe organization of the visual field representation within the thalamic reticular nucleus (TRN) of the rabbit was studied. Focal injections of horseradish peroxidase (HRP) and/or [3H]proline were made into visuocortical areas V1 and V2 and the dorsal lateral geniculate nucleus (dLGN). The resultant labelling in the thalamus was analysed.A single injection in V1 or V2 results in a single zone of terminal label within the TRN that is restricted to the dorsocaudal part of the sheet‐like nucleus. In comparisons of the zones of label following injections at two different cortical sites in V1, a medial to lateral shift in label across the thickness of the TRN sheet is accompanied by a medial to lateral shift in label in the dLGN; a dorsal to ventral shift in label within the plane of the TRN sheet is accompanied by a dorsal to ventral shift in label in the dLGN. Thus, like the dLGN the TRN receives a precise topographic projection from V1. In reconstructions from horizontal sections the zones of label within the TRN resemble ‘slabs’, which lie within the plane of the nucleus parallel to its borders. Thus, the slabs of visuocortical terminals and reticular dendrites are similarly oriented. As revealed by the orientation of the slabs, the lines of projection representing points in visual space are represented by the oblique rostrocaudal dimension of the TRN.Injections restricted to V1 produce terminal labelling that is confined to the outer two‐thirds of the TRN across its thickness, whilst those involving V2 result in terminal labelling within the inner one‐third of the nucleus. Thus, the adjacent cortical areas V1 and V2 project in a continuous fashion across the mediolateral dimension of the TRN. The organization of the map within the TRN, which was revealed by visuocortical injections, was confirmed by the pattern of retrograde labelling within the nucleus following geniculate injections of HRP.On the basis of these findings and those in other mammalian species, two major conclusions can be reached that alter our view of the TRN. First, rather than mapping onto the whole nucleus in a continuous fashion, the cortical projection to the TRN has significant discontinuities. Second, rather than integrating efferents from widespread cortical areas, the reticular dendrites are related to focal areas

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00777.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY