摘要:

AbstractThe peripheral membrane protein gephyrin copurifies with the inhibitory glycine receptor of mammalian spinal cord. It binds with high affinity to polymerized tubulin and has been implicated in the anchoring of the glycine receptor to cytoskeletal elements. Recently, cDNA cloning has identified variants of the gephyrin mRNA, which originate from alternative splicing of four exonic regions (cassettes 1 – 4). In this study, the expression patterns of gephyrin splice variants were determined in the adult and developing rat brain byin situhybridization with synthetic oligonucleotide probes. Gephyrin transcripts were detected throughout the brain and spinal cord, with mRNAs containing cassette 2 (C2 transcripts) being predominant in adult animals. C3 and C4 transcripts were seen in cerebellar granule cells and in the dentate gyrus, whereas a C1 probe did not produce detectable hybridization signals. During development, C2 and C3 mRNAs were found in most brain regions. Generally, the spatial and temporal distribution of gephyrin transcripts is similar to that of the glycine receptor β subunit mRNA reported previous

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00965.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe functional topography of the myelin‐associated glycoprotein (MAG) was investigated by electron microscopic analysis of rotary‐shadowed molecules of a MAG fragment (MAG 90) comprising the five immunoglobulin‐like domains of the extracellular part of the molecule. MAG 90 molecules appeared as rod‐like structures (18.5±1.2 nm long and 4.0±0.8 nm wide) with a globular domain at one end. Antibodies directed against the amino‐ and carboxy‐terminus of MAG 90 interacted with the non‐globular terminal region, indicating that the molecule is bent in the globular region with the amino‐ and carboxy‐terminal arms in close apposition to each other. An antibody which interferes with the binding of MAG to neurons interacted predominantly with the globular domain of MAG 90. The fibril‐forming collagen types I, III and V bound mainly to the non‐globular terminal region of MAG 90, whereas the majority of heparin molecules interacted with the globular region of the molecule. The L2/HNK‐1 carbohydrate structure was localized at the non‐globular region in the protein fragment comprising the fourth and fifth

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00966.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have examined the hypothesis, for the case of mouse axons, that isolating an axon from its cell body will lead to a rapid failure of fast axonal transport as anterogradely moving organelles vacate the axon in a proximo‐distal direction, and retrogradely moving organelles vacate it in the opposite direction. We used CD1 and BALB/c mice and the Wallerian degeneration‐resistant mutant C57BL/Ola. Sciatic nerves were cut high in the thigh; at various times up to 8 days later nerves were removed from the animal and individual myelinated axons from the segment distal to the cut were examined by video light microscopy to detect rapid organelle transport. Bidirectional fast organelle transport did decrease in amount with time but not nearly as rapidly as predicted, and anterograde and retrograde organelle velocities remained normal through time. In the C57BL/Ola mouse some structurally preserved axons contained organelles that transported at normal velocities in the anterograde and retrograde directions for as long as 8 days after axotomy. To test one of the possible origins of transported organelles in long‐surviving axons we examined organelle transport very close to narrow lesions in axons bathed in a medium compatible with intracellular function. No organelles crossed the lesion but bidirectional organelle transport took place proximal and distal to the lesion; the amounts were compatible with the interpretation that ∼30% of organelles reversed transport direction on either side of the lesion. We propose that at least some of the organelles that undergo persistent transport in axons isolated from their cell bodies shuttle back and forth between the ends of the isolated

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00967.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractDuring the development of the rat sciatic nerve extensive proliferation of glial cells occurs, and there is a very substantial rearrangement of the cytoarchitecture as axons and Schwann cells assume relationships which lead to the formation of the myelinated and unmyelinated axons characteristic of adult nerve. The maturation of Schwann cells from Schwann cell precursors and the matching of Schwann cell numbers to axons is an important part of this process. We have therefore studied the proliferation of Schwann cell precursors and Schwann cells during the development of the rat sciatic nerve from embryonic day 14 to postnatal day 28 by combining bromodeoxyuridine injections of rats with double‐label immunohistochemical techniques. The results reveal that DNA synthesis occurs in both Schwann cell precursors and Schwann cells throughout early nerve development. The labelling index is already substantial at embryonic day 14, but from embryonic day 17, when essentially all the glial cells have converted from precursor to Schwann cell phenotype, it rises sharply, peaking between embryonic day 19 and 20 before declining precipitously in the early postnatal period. This rapid decline in DNA synthesis coincides with the appearance of the myelin protein Po, and in individual cells DNA synthesis is incompatible with the expression of Poprotein. Non‐myelin‐forming Schwann cells, which mature later in development, continue to synthesize DNA until at least postnatal day 15, but by day 28 essentially all Schwann cells in the nerve are quie

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00968.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe quail – chick chimaera system was used to investigate the origin of the various neuronal cell types of the cerebellum from the mesencephalic and metencephalic brain vesicles at the 11‐ to 14‐somite stage in the avian embryo. We have already demonstrated that the cerebellum is derived from both the mesencephalic and metencephalic brain vesicles. The mesencephalic contribution to the cerebellum is restricted to a mediodorsal territory inserted as a V‐shaped area into the primitive metencephalic vesicle through complex morphogenetic movements taking place from day 2 to day 4 of embryonic development. Here we report that the cerebellar presumptive territory extends along the anteroposterior axis, over the caudal half of the mesencephalon and the rostral half of the metencephalon. Along the dorsoventral axis, the cerebellar anlage is located in the alar plates at the exclusion of the roof and basal plates, i.e. lies in the lateral walls of the neuroepithelium in the area included between ∼25 and 120° with respect to the sagittal plane. We also report that the neuroepithelium corresponding to the cerebellar presumptive territory also yields other brain structures (e.g. part of the optic tectum in the mesencephalon). The external granular layer (EGL) arises only from the rostral metencephalon, undergoing extensive tangential movements which we have analysed in detail: the more ventral the position of cells in the metencephalic alar plates the more rostral and lateral is their position in the EGL. Finally, we discuss the fact that the cerebellar cortex, an integrative structure of the brain, arises from the alar plates of the neural tube. This is consistent with the general spatial organization of the neural anlage of the vertebrate embryo, in which this part of the neuroepithelium is devoted to the production of interneurons, whereas the basal plate and the neural folds yield motor structures and primary sensory neurons re

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00969.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have studied the effects of tissue transplants and antibodies (IN‐1) against the myelin‐associated neurite growth inhibitory proteins on sprouting and regeneration of the rat corticospinal tract (CST). Transplantation of embryonic spinal cord tissue into bilateral transection lesions of the lower thoracic spinal cord in young adult rats resulted in a marked increase of the sprouting of the lesioned CST. This sprouting effect was probably elicited by soluble factors released from the transplants, and was enhanced by the IN‐1 antibodies. The retraction of lesioned CST fibres normally observed with prolonged survival times was also reduced by the presence of transplants. In spite of these growth‐promoting effects of the transplants, the regenerative elongation of CST sprouts into the caudal spinal cord was dependent upon the neutralization of the myelin‐associated inhibitory proteins. In the controls (no antibodies or control antibodies) only 27% of the animals showed elongation of CST fibres exceeding the sprouting distance of 0.7 mm. These fibres grew to a maximal length of 1.8 mm (mean±SEM, 1.2±0.1). In contrast, 60% of the IN‐1‐treated, transplant‐containing rats showed elongations of>0.7 mm, and these fibres grew up to 10.1 mm (4.6±0.5). Regenerating fibres crossed the lesion site through remaining tissue bridges. Neither embryonic spinal cord transplants nor a variety of implanted bridge materials could serve as a substrate for the rege

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00970.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractSecondary cultures of adult rat olfactory bulb (OB) contained three different types of cell: (i) process‐bearing cells; (ii) macrophage‐like cells and (iii) fusiform cells. The immunohistochemical properties of process‐bearing cells closely corresponded to those described for ensheathing gliain vivo.The most distinctive feature of these cells was their immunoreactivity for low affinity nerve growth factor receptor (NGFR). Process‐bearing cells also shared the ultrastructural properties of ensheathing gliain vivo, as well as the ability to ensheath olfactory axons. In contrast, macrophage‐like cells had the immunostaining properties of microglia, and fusiform cells were likely capillary endothelial cells.Neurites outgrowing from olfactory epithelium explants, when co‐cultured with adult OB cells, grew preferentially over NGFR positive cells. Olfactory neurites exhibited NGFR immunoreactivity and were enfolded by NGFR positive cells. After ensheathment, this immunoreactivity decreased from the neurite and disappeared from the glial membrane in contact with the neurite. However, NGFR immunoreactivity was maintained in the portion of the glial membrane not involved in ensheathing. In summary, ensheathing cellsin vitroretained both the ultrastructure shownin vivoand the ability to ensheath olfactory neurites. The Schwann cell‐like properties of ensheathing glia, could partially explain the permissibility of adult OB to

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00971.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractThe naturally occurring neuron death of normal development has been shown to depend on trophic factors produced and released by target cells. It has also been shown that the afferent supply and local interactions play a role in the control of this degenerative phenomenon. We studied the effect of trophic factors produced by intrinsic retinal cells on the survival of retinal ganglion cellsin vitro.Retinae of newborn hooded rats were retrogradely labelled with horseradish peroxidase injected into the superior colliculus to permit the identification of retinal ganglion cells in culture. We tested the effect of conditioned media either from aggregates or from explants of retinal cells from neonatal rats on the survival of ganglion cellsin vitro.Our results showed that both conditioned media increased the survival of these cells. The trophic activity was dose‐dependent, was maintained after dialysis against a 12 kDa membrane, was abolished by heating at 56°C for 30 min, and was not found in conditioned medium from cerebral cortical explants. Conditioned medium obtained without fetal calf serum presented the same trophic effect. These results suggest that the local control of developmental neuron death by intrinsic retinal cells may be mediated by neurotrophic facto

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00972.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractEffects of substance P on cultured neurons of the locus coeruleus of the rat were studied using the whole‐cell patch clamp technique. In some cells substance P produced a decrease in a K conductance which showed an inwardly rectifying property. In other cells substance P produced an initial inward current which was accompanied by a conductance increase. The rest of the cells showed responses which were mixtures of the above two responses. The measurement of the reversal potential of the initial inward current after suppressing the voltage‐gated Ca and K conductances suggests that it is caused by an increase in a non‐selective ionic conductance. In cells loaded with 260 μM GTPγS, application of substance P produced an irreversible reduction of the K conductance, while the initial inward current could still be recorded, suggesting that the former is mediated by a G protein, whereas the latter may be activated by a different signal transduction mechanism. The initial inward current was not eliminated by external application of high concentrations of tetrodotoxin,d‐tubocurarine or amiloride. Nor was it affected by the intracellular application of cyclic GMP or c

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00973.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

AbstractIntracellular recordings were made from CA1 neurons in rat hippocampal slices maintainedin vitro.When Na+currents were blocked with tetrodotoxin and K+conductances known to be sensitive to suppression by muscarinic agonists were blocked by 2 mM Ba2+, CA1 cells were depolarized by carbachol (3 – 10 μM) with an attendant conductance increase, whereas prior to Ba2+the agonist produced a decrease or no change in conductance. Under voltage clamp at ∼–60 mV and in the presence of tetrodotoxin and Ba2+, carbachol (3 – 10 μM) induced a variable‐latency biphasic inward current of up to 380 pA associated with a conductance increase of ∼50%. The first phase was associated with an increase (more than 2‐fold) of the Cs+‐sensitive, hyperpolarization‐activated cationic current,IQ. Carbachol also accelerated the kinetics ofIQat – 100 mV with an average 24% reduction in its activation time constant. The second phase reflected an additional inward current that was Cs+‐resistant, displayed little apparent voltage sensitivity and had a mean extrapolated reversal potential, determined in the presence of external Cs+(>5 mM), of ∼–20 mV. In a small proportion of cells the second phase of inward current was followed (or overlapped) by an outward current, also associated with a conductance increase, which reversed at ∼–70 mV. These carbachol actions were prevented by extracellular 300 μM Cd2+and 2 mM Mn2+, by high levels (>5 mM) of extracellular Mg2+or Ca2+, and by omission of Ca2+or reduction of extracellular Na+to 25 mM by substitution of NaCl with Tris orN‐methyl‐d‐glucamine. Carbachol action was not mimicked by oxotremorine (≤60 μM), but was irreversibly blocked by this drug. Likewise, atropine (100 nM) irreversibly and gallamine (10 μM) reversibly antagonized carbachol's action. The action of carbachol was blocked shortly after prior exposure of slices to 2 – 5 mM caffeine. Chronic or acute incubation of slices with 2 mM Li+potentiated (between 1‐ and 2‐fold) carbachol responses. The data indicate that muscarinic activation increases cationic flux by a calcium‐dependent potentiation ofIQand activation of a non‐selective conductance. The probability that inositol phospholipid metabolism

ISSN:0953-816X    

DOI:10.1111/j.1460-9568.1993.tb00974.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY