摘要:

AbstractTransection of the rat facial nerve leads to a rapid activation of both astrocytes and microglia around axotomized motoneurons. The factors involved in glial activationin vivoare poorly defined but cytokines have been implicated as major regulators of glial activityin vitro.In the present study we have investigated the expression of cytokine mRNAs in the axotomized facial nucleus that might be involved in glial activation. Eight hours after axotomy unilateral transection of the facial nerve had already induced a rapid accumulation of interleukin (IL)‐6‐mRNA, with a peak at 24 hours. No IL‐6 mRNA was detected on the unoperated control side. Transforming growth factor (TGF)‐β1 mRNA was detected at low levels in the normal facial nucleus, increasing to three times the normal level 2 days after axotomy. After day 7 TGF‐β1 mRNA levels gradually declined, with a second minor peak 21 days after axotomy.In situhybridization experiments, 4 and 21 days after axotomy, localized TGF‐β1 mRNA to activated microglial cells around regenerating motoneurons, as well as probably some astrocytes. Motoneurons did not express TGF‐β1 mRNA. TGF‐β3 was found to be normally expressed in the facial nucleus but was not regulated by axotomy. No mRNA for IL‐1, tumour necrosis factor‐α or interferon‐γ was found in the regenerating facial nucleus at any point in time. Our data indicate that IL‐6 might act as an early activating signal for glial cells in response to motoneuron axotomy, and that TGF‐β1 expressed by activated glial cells might provide a long‐lasting negative feedback

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00929.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe development of immunoreactivity for the calcium‐binding protein calbindin‐D28k (CaB) was investigated in the embryonic and hatched chick lumbosacral spinal cord. CaB‐immunoreactive neurons were revealed in the dorsal and ventral horns as well as in the intermediate grey matter from early stages of neuronal development. CaB immunoreactivity was first detected in large neurons in the presumptive dorsal horn at embyronic day 5, while small neurons in the lateral dorsal horn were the last to appear, at embryonic day 10. We have identified and traced the morphological maturation of six CaB‐immunoreactive cell groups, three in the dorsal horn and three in the ventral horn. In the dorsal horn these groups were (1) large neurons in the lateral dorsal horn (laminae I and IV), (2) small neurons in the lateral dorsal horn (lamina II), and (3) small neurons in the medial dorsal horn (lamina III). All three groups were present throughout the entire length of the lumbosacral spinal cord and showed persistent CaB immunoreactivity. In the ventral horn, CaB‐immunoreactive neurons were classified into the following three categories: (1) Neurons dorsal to the lateral motor column (lamina VII). These neurons were present exclusively in the upper lumbosacral segments (LS1 – 3), and they showed steady CaB immunoreactivity during their maturation. (2) Neurons at the dorsomedial aspect of the lateral motor column (at the border of laminae VII and IX). This population of neurons was characteristic of the lower segments of the lumbosacral cord (LS5 – 7) and presented transient CaB expression. (3) Neurons within the lateral motor column (lamina IX). These neurons were dispersed throughout the length of the lumbosacral spinal cord. They were three to four times more numerous in the upper than in the lower lumbosacral segments, and their numbers declined throughout LS1 – 7 as the animal matured. The characteristic features of the development of neurons immunoreactive for CaB are discussed and correlated with previous neuroanatomical and physiological studies concerning sensory and motor functions of the developing ch

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00930.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe response of the βAPP gene to neuronal injury was studied in the facial and hypoglossal nerve nuclei of the rat after corresponding nerve axotomy. Increased levels of βAPP 695, 714, 751 and 770 mRNAs were observed after either facial or hypoglossal nerve axotomy in the parent ipsilateral motor neurons. The increase was gradual, with maximal values 7 days after axotomy. βAPP mRNA expression returned to normal values 60 days after the lesion. Increased βAPP immunostaining was also detected in ipsilateral chromatolytic motor neurons. No change in βAPP immunoreactivity was observed in oligodendrocytes, another cell type expressing βAPP under normal conditions. A rapid increase in the expression of the GFAP gene was observed in reactive astrocytes surrounding chromatolytic neurons in the ipsilateral facial or hypoglossal nuclei. Thus, in contrast with other models of neuronal injury, where only the Kunitz protease inhibitor‐containing βAPP mRNA isoforms are increased, all βAPP mRNAs are increased in the axotomy model. Furthermore, although βAPP expression has been shown to be increased in reactive astrocytes following neuronal injury, in the present study the increase was essentially found in the motor neurons reacting

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00931.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe failure of axon regeneration in the injured mammalian central nervous system has been ascribed, in part, to the inhibitory effects of myelin proteins. To investigate the influence of myelination on neurite growth and regeneration by both central nervous system and peripheral nervous system neurons, isolated rat neonatal retinal ganglion cells and adult and neonatal dorsal root ganglion neurons were cultured on cryostat sections of both immature unmyelinated and mature fully myelinated adult rat optic nerve. In agreement with earlier studies using neonatal peripheral neurons, the adult optic nerve failed to support neurite outgrowth from any of the neurons tested. A new finding was that tissue sections from unmyelinated optic nerve (aged embryonic days 18 and 20, and postnatal days 1–3), also failed to support the growth of neurites from neonatal retinal ganglion cells and both neonatal and adult dorsal root ganglion neurons. Neonatal retinal ganglion cells also failed to extend neurites on sections of pre‐degenerated sciatic nerve, a tissue shown in our previous work to be a good substratum for supporting neurite growth for both neonatal and adult DRG neurons. These results suggest that cells in the immature optic nerve either express widely acting axon growth inhibitory molecules unrelated to previously described myelin proteins, or do not synthesize appropriate axon growth promoting molecules. They also reveal that, for axon regeneration, central nervous system and peripheral sensory neurons require distinct substratum interacti

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00932.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractDepolarization induced in rat hippocampal slices by a high concentration of extracellular K+leads to an increase in the phosphorylation of microtubule‐associated protein MAP2. The comparison of the major phosphopeptides derived fromin situandin vitrophosphorylated MAP2 suggests the implication of calcium‐dependent protein kinases, including calcium/calmodulin‐dependent protein kinase type II and protein kinase C, in the up‐phosphorylation of MAP2. In particular, a peptide containing the tubulin‐binding domain of the MAP2 molecule may be phosphorylated by protein kinase C. As the association of MAP2 with the cytoskeleton may be regulated by phosphorylation, we suggest that changes in the phosphorylation level bf MAP2 might be involved in synaptic remodelling in hippocampa

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00933.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have previously demonstrated that primary astrocyte cultures from neonatal rat cortex and C6 glioma cells express a calcium‐independent nitric oxide synthase (NOS) on induction with bacterial endotoxin (lipopolysaccharide, LPS). One hypothesis regarding the mechanism of the LPS induction is that it causes release of cytokines from these cells which then induce the enzyme directly. Such cytokine induction of NOS has been demonstrated in many extraneural cell types.l‐Arginine‐dependent increases in cyclic GMP correlate with smaller increases in accumulation of nitrite, the major oxidation product of nitric oxide, and hence can serve as a more sensitive measure of nitric oxide production. Here we provide evidence that interferon‐γ (IFN‐γ), interleukin (IL)‐1β and tumour necrosis factor‐α inducel‐arginine‐dependent cyclic GMP synthesis in C6 cells and that a combination of IFN‐γ and IL‐1β inducel‐arginine‐dependent cyclic GMP synthesis in astrocyte cultures, indicating that these cytokines induce NOS. In both cell types the induction by cytokines was less sensitive to inhibition by dexamethasone, IL‐10 and IL‐4 than was induction by LPS. These data suggest that cytokines can also induce a NOS in glial cells and that the mechanism of this induction may be more direct than that of LPS, since it is less sensitive to modulation by immunosuppressors. Due to the close associations of astrocytes with neurons and microvasculature, cytokine‐induced NOS could have potentially important pathophysiological

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00934.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the 12‐day‐old rat cochlea, the synthesis of inositol phosphates (IPs) can be activated via M3 cholinoceptors. This stimulation is blocked by ototoxins (mercury, ethacrynate, cisplatin, neomycin), drugs with side effects that lead to damage of hair cells and strial cells. As these toxic effects can be reversedin vivoby thiol molecules, we investigated whether modifications of thiol compounds could be involved in ototoxin‐induced inhibition of the IP turnover in the cochlea. For this purpose, we assessed whether the sulphhydryl‐modifying reagentsN‐ethylmaleimide and cadmium modify the carbachol‐stimulated formation of IPs in the 12‐day‐old rat cochlea. Both molecules inhibit the carbachol effect on a dose‐dependent way without altering the basal metabolism of IPs. As cadmium may block some calcium channels, the effect of verapamil, another calcium channel antagonist, was tested. Verapamil (1 –50 μM) does not alter carbachol‐evoked IP formation, suggesting that the inhibitory effect of cadmium is not due to a calcium influx block. Binding experiments with the muscarinic ligand quinuclidinyl benzylate (QNB) showed that the sulphhydryl‐modifying reagents do not displace QNB from binding sites. Combining ototoxins and reagents shows thatN‐ethylmaleimide acts synergistically with all ototoxins but ethacrynate while cadmium does so only with mercury. BothN‐ethylmaleimide and cadmium have additive effects with ethacrynate. As a supplement, disulphide bond‐modifying agents do not alter the carbachol‐enhanced metabolism of IPs. These results suggest that molecules having thiol‐modifying properties inhibit the carbachol‐induced turnover of IPs without acting at the muscarinic sites. Since thiol modifiers and ethacrynate share similar features in both QNB binding and IP response it is hypothesized that they strike

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00935.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this report we have studied the influence of hippocampal neurons on neuropeptide mRNA expression in both dorsal and ventral striatum in the rat. Intrahippocampal unilateral kainic acid injections were performed in control animals and in animals with a unilateral 6‐hydroxydopamine‐induced dopamine deafferentation of the striatum.In situhybridization combined with quantitative image analysis was used to study the expression of preprotachykinin A mRNA encoding the neuropeptides substance P and neurokinin A. The 6‐hydroxydopamine‐induced lesion caused a decrease of preprotachykinin A mRNA levels in the ipsilateral dorsal striatum and in both sides of the ventral striatum. In normal rats, the intrahippocampal kainic acid injection caused a twofold increase in preprotachykinin A mRNA in the limbic parts of the striatum, which are innervated by the hippocampus. No effect of the kainic acid injection was seen in the lateral parts of the dorsal striatum, a region which does not appear to be innvervated by the hippocampus. Animals with a 6‐hydroxydopamine lesion showed a similar kainic acid‐mediated increase in preprotachykinin A mRNA in parts of the ventral striatum. In the dopamine‐lesioned dorsal striatum and ventral striatum the decreased preprotachykinin A mRNA levels were normalized by the intrahippocampal kainic acid injection. These results show that kainic acid‐mediated excitation of hippocampal neurons causes a dopamine‐independent induction of preprotachykinin A mRNA expression in parts of the ventral striatum, and reverses the dopamine deafferentation‐induced decrease of preprotachykinin A mRNA in both dorsal and ventral striatum. Combined, our results suggest that hippocampal neurons can regulate preprotachykinin A mRNA expression in both the ventral and

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00936.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractExtending previous investigations of the topographic relationship between ocular dominance and orientation columns in the cat visual cortex the two systems were visualized with transneuronally transported [3H]proline and with activity‐dependent uptake of [14C]2‐deoxyglucose, respectively. In addition, we used the 2‐deoxyglucose method for a functional assay of both columnar systems. To this end, cats were injected with [3H]proline in the right eye. Two weeks later, they were stimulated monocularly through this eye by presenting contours of only a single orientation in the left and contours of many different orientations in the right visual hemifield while 2‐deoxyglucose was injected. The patterns of increased 2‐deoxyglucose uptake and of terminal labelling were analysed in flat‐mount sections of the visual cortices and in frontal sections of the lateral geniculate nuclei. In the lateral geniculate nucleus, regions of increased 2‐deoxyglucose uptake are in register with the [3H]proline‐labelled laminae of the open eye. In the visual cortex, the hemispheres stimulated with many different orientations showed a rather homogeneous accumulation of 2‐deoxyglucose over the entire extent and throughout all layers of area 17. The hemispheres stimulated with a single orientation displayed columnar patterns of orientation domains essentially similar to those obtained with binocular presentation of a single orientation. In particular and despite monocular stimulation, regions of increased 2‐deoxyglucose uptake were neither in register with the [3H]proline‐labelled terminals of the stimulated eye in layer IV nor confined to columns of neural tissue above and below these terminals. The maximal horizontal offset between the termination sites of thalamic afferents and activated orientation columns was in the order of 400 μm. These findings suggest several conclusions. (i) In the cat visual cortex, binocular convergence seems to occur so early in cortical processing that monocular stimulation with many orientations leads to a rather homogeneous activation of cortical tissue. (ii) From the termination zones of geniculate afferents activity is apparently distributed already within layer IV to the respective orientation columns. (iii) This horizontal spread of activity could be assured by target cells with radially extending dendrites and/or tangen

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00937.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIn the course of experiments studying the organization of ocular dominance columns in the visual cortex of cats, we noticed that—contrary to common belief—labelling with 2‐deoxyglucose after monocular stimulation failed to induce a pattern of ocular dominance columns but resulted in a rather homogeneous 2‐deoxyglucose uptake throughout area 17 in anaesthetized and paralysed animals. We wondered whether 2‐deoxyglucose columns could be obtained in awake animals and/or in strabismic animals, which have a more pronounced segregation of ocular dominance columns. To this end, we investigated 2‐deoxyglucose patterns after monocular stimulation in three groups of animals: (i) in awake normally reared cats, (ii) in awake strabismic cats and (iii) in anaesthetized and paralysed strabismic cats. Additionally, we labelled ocular dominance columns with intraocular [3H]proline injections. In all cats, monocular stimulation induced 2‐deoxyglucose patterns that were in precise register with the proline‐labelled ocular dominance columns in layer IV. Regions of increased 2‐deoxyglucose uptake extended in a columnar fashion through all cortical layers. In contrast to normally reared animals, in strabismic cats, the expression of 2‐deoxyglucose labelled ocular dominance columns was not abolished by anaesthesia or paralysis. However, there was a difference between the 2‐deoxyglucose patterns in the awake normally reared cats and the strabismic animals. In the former, the patches of 2‐deoxyglucose labelling were smaller and occupied less territory than the afferents of the stimulated eye in layer IV. Together with the results of the previous study, these data indicate that in awake normally reared and in awake and anaesthetized strabismic cats, but not in anaesthetized and paralysed normally reared animals, monocular stimulation activates selectively neurons in columns that are in register with the termination sites of afferents from the stimulated eye. This suggests the existence of a mechanism in normally reared animals which restricts cortical activation after monocular stimulation to territories that are in register with the afferents from the stimulated eye. This mechanism appears to be effective only when the animals are awake and actively exploring their environment. This and the fact that the active columns were narrower than the terminal fields of the stimulated eye suggest an active inhibitory process, perhaps related to mechanisms of selective attention. The observation that ocular dominance columns persist in strabismic cats even under anaesthesia can be accounted for by the lack of binocular conve

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00938.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY