摘要:

AbstractThe expression and cellular distribution of glia‐derived nexin (GDN), laminin and fibronectin on C6 rat glioma cells, rat brain astrocytes and rat fibroblasts were investigated by immunoblotting and immunocytochemistry. Western blot analysis of C6 cell homogenates confirmed the specificities of the antibodies. Immunocytochemical staining of C6 cells, astrocytes and fibroblasts showed that laminin, fibronectin and GDN were abundant on the surface of glioma cells and astrocytes whereas on fibroblasts fibronectin was abundant though only traces of GDN and laminin could be detected. The light microscopy data were confirmed by ultrastructural studies showing that each antigen was present on the surface of the C6 rat glioma cells as numerous spots with slightly different distribution patterns for each of the antigens. In fibroblast cultures, the antigens were also localized in the extracellular matrix in the vicinity of the cells. Migrating fibroblasts but not migrating glioma cells or astrocytes deposit the matrix‐proteins onto the substratum leaving behind a track of GDN, laminin and fibronectin. When the cells were treated with heparin prior to antibody incubation, the GDN immunoreactivity completely disappeared, whereas the distribution and abundance of laminin and fibronectin was not affected. Our data show that GDN binds, possibly by a heparin‐like molecule, to the outer surface of cells or to the extracellular matrix and may protect cells and matrix proteins against proteolytic degrad

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00797.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractArea V5 or MT of primate extrastriate visual cortex is specialized for involvement in the analysis of motion and receives input from two layers, 4B and 6, of the striate cortex or V1. Injections of horseradish peroxidase ‐ wheatgerm agglutinin into V5 reveal a patchy distribution of labelled cells and axonal terminals in layer 4B, suggesting the presence of a segregated and functionally specialized subsystem within the layer. The patches are similar in size and frequency to the cytochrome oxidase blobs of layers 2 and 3, but bear little systematic relationship to them. V5‐efferent cells in layer 6, however, tend to avoid the cores of the blobs.The back projection from V5 is continuously distributed in layers 6 and 1, though it is absent inside representations of the central 10° in the latter; it is also diffusely distributed between the patches in layer 4B and over a territory wider than that occupied by labelled cells. It is thus inferred that the back projection probably influences (a) V5‐efferent cells other than those projecting to the injected site in V5, and (b) cells projecting to locations other than V5.There are no major changes in the cortical frequency of V5‐efferent cells with eccentricity in the visual field representation. The V5‐efferent cells of layer 6 are tenfold less frequent than those of layer 4B and as a population may therefore be involved with only a limited sector of directions of movement. Furthermore, their topographic distribution does not always coincide exactly with that of the layer 4B population, as if a site in V5 receives information about slightly non‐corresponding regions of the visual field from th

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00798.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractArea V2 of the cerebral cortex of higher primates has a complex cytochrome oxidase architecture whose most characteristic element is a set of stripes running orthogonal to its long axis. These stripes can be related to the segregation between the various pathways in which V2 participates. In the macaque monkey the more metabolically active stripes are alternately thick and thin and only one set, the thick stripes, is found to possess clusters of labelled cells following injections of horseradish peroxidase — wheatgerm agglutinin into area V5. Some of these clusters, but not all, coincide with substructures inside the thick stripes. V2 of the owl monkey has a similar organization except that the diversification into thick and thin stripes is less prominent, both in terms of their appearance and in that more than every alternate stripe is connected to area MT, the likely homologue of V5.The return projection from V5 to V2 is more widespread than the origin of the forward projection. It extends not only between the clusters of V5‐efferent cells within the thick stripes but also across the intervening thin stripes and less active interstripes. Because the latter subserve functions different from those of the thick stripes it would seem that their receipt of a back projection from an area to which they do not project, V5, may be relevant to the process of intergration of signals relating to different attributes of vis

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00799.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe postnatal development of protein kinase C isozymes II and III (PkCII/III) was investigted in the cat visual cortex by applying immunohistochemical methods with a monoclonal antibody against PkC(II/III).PkC(II/III)‐like immunoreactivity was found in astrocytes and neurons. All astrocytes but only a few of the immunoreactive neurons were homogeneously labelled. The majority of the latter exhibited a punctate distribution of reaction product. The staining pattern of neurons and glial cells showed developmental changes until at least 18 months of age. These were characterized by (1) a gradual increase of immunolabelled astrocytes, (2) an abrupt appearance of immunopositive neurons at 4 weeks of age, (3) an aggregation of immunolabelled neurons in a well‐delineated band in lower layer IV between 4 weeks and 12 months of age, and (4) a decrease in number of PkC(II/III)‐positive neurons after 12 months of age.These developmental changes in the expression of PkC(II/III)‐like immunoreactivity correlate well with the time course and the laminar selectivity of experience‐dependent malleability. Moreover, they correspond closely to changes in several systems that contribute to PkC‐activation and are thought to be involved in use‐dependent neuronal plasticity. Thus, we consider these results as compatible with the hypothesis that the PkC isozymes II and III participate in cellular mechanisms underlying use‐depen

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00800.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThetetanic(tta; X.‐52.6) mutation has been isolated on the basis of its sensitivity to extradoses of the normalShakergene complex (ShC) where the K+channel la is encoded. The mutant shows up to threefold elevation of the membrane bound protein phosphatase type 1 (PP1) activity in body extracts, probably due to reduced levels of the PP1 specific inhibitor 2 (I‐2). By contrast, PP1 activity in the head is only half of the normal value. In addition,ttafails to perform normally in a negative reinforcement olfactory paradigm. The functional relationships between phosphorylation, K+currents, phosphatase activity and modulation of synaptic activity during learning and memory are discussed in the light of their possible genetic li

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00801.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractResponse properties of neurons in brain slices of guinea pig parietal neocortex were examined following intracellular injection of the Ca2+chelators, EGTA and BAPTA. Although chelator injection did not cause any consistent change in passive membrane properties, it did induce 81% of neurons encountered at all sub‐pial depths to become ‘bursters’, in that just‐threshold depolarizing current pulses triggered all‐or‐none bursts of 2–5 fast action potentials. Transition to ‘burstiness’ was associated with disappearance of an AHP and appearance of a DAP. Although chelator caused a slight increase in steady‐state firing rate, marked accommodation persisted. Extracellular Co2+or Mn2+had an effect on steady‐state firing rate similar to that of the intracellular chelators; however, exposure to these Ca2+channel blockers also caused steady state depolarization, increased resting input resistance and time constant, and profound spike broadening. This treatment never induced transition to ‘burstiness’. Chelator‐injected neurons ceased to generate bursts when Ca2+was replaced by Mn2+in the Ringer's solution. During exposure to 10−6M TTX and 20 mM TEA, 50–200 msec Ca2+spikes followed brief depolarizing pulses. As chelator was injected into the cell, there was progressive prolongation of the Ca2+plateaus, which was associated with slowing of the rate at which membrane resistance gradually recovered following the initial increase in conductance.These findings indicate that under normal conditions, activity‐related increases in intracellular Ca2+activate processes which prevent most neocortical neurons from being bursters. These processes probably include Ca2+‐dependent K+currents, and Ca2+

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00802.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe temporal development of long‐term potentiation (LTP) was examined in the CA1 region of the hippocampal slice preparation (bath temperature 30°C). LTP was evoked by a single brief afferent tetanus (3–40 impulses at 50 Hz) given in the presence of picrotoxin (to facilitate LTP induction). Short‐lasting potentiation processes unrelated to LTP were excluded by comparing the potentiation obtained in picrotoxin solution with that obtained in normal solution or in the presence of the N‐methyl‐D‐aspartate receptor antagonist 2‐amino‐5‐phosphonovalerate. LTP was also evoked by pairing single test volleys with brief (2–3 impulses) heterosynaptic tetani in picrotoxin solution. Both methods showed no significant rise of LTP until about 3 s after the induction event. LTP thereafter developed almost linearly towards a peak within 20–25 s after the tetanus, the time course being practially independent of the induction method and of the relative amount of LTP evoked. The latency and rise time of LTP depended on bath temperature, being about twice as long at 25°C as at 30°C. Following the peak, LTP rapidly decayed to less than half its peak value in 8 min, the decay tending to be less with longer trains. The LTP component reaching its peak 20–25 s after a tetanus was practically occluded after a saturating homosynaptic tetanization, and was only partially recovered 1 h afterwards. The latency to the onset of LTP suggests an indirect coupling between the calcium influx, presumed to trigger the potentiation, and the expression of LTP. The independence of the early time course with respect to the induction strength indicates that the intervening system(s) o

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00803.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effects of quisqualic acid lesions of the nucleus basalis magnocellularis on short‐term memory capacities of the rat have been investigated using the delayed matching and non‐matching to position tasks. The lesions do not disrupt performance of either task by pretrained animals, but do disrupt the ability to acquire the non‐matching contingency, and to reverse to the non‐matching task when trained on the matching task. The unidirectional nature of the reversal deficit has been replicated. The generalized disruption of performance of either task by the muscarinic antagonist scopolamine was comparable in lesioned and control rats. The lesions were associated with extensive loss of acetylcholinesterase staining in the basal forebrain and in the neocortex, and 55% depletions of choline acetyltransferase activity in the neocortex but not in the hippocampus. These observations demonstrate that the cholinergic projection from nucleus basalis to the neocortex is not critical for normal short‐term memory, but that lesions involving this system do disrupt specific types of conditional discrimination

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1989.tb00804.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY