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S Cullheim

Publications and source records attributed to S Cullheim.

At least 37 records · Page 2Linked to original sources
PubMed1998

Expression of MHC class I and beta2-microglobulin in rat spinal motoneurons: regulatory influences by IFN-gamma and axotomy.

The low expression of MHC antigens is believed to be one factor of importance contributing to the immune-privileged status of CNS neurons. We here describe that motoneurons, in contrast to other nerve cells in the lumbar spinal cord of the adult rat, express both MHC class I and beta2-microglobulin mRNA. The motoneurons also display in situ hybridization signal for IFN-gamma receptor mRNA. After a peripheral axotomy, the motoneurons show a clear upregulation of beta2-microglobulin mRNA. IFN-gamma treatment of cultured rat embryonic spinal motoneurons causes a similar upregulation of especially beta2-microglobulin. Based on these facts, we propose that spinal motoneurons can be influenced by IFN-gamma and recognized by cytotoxic CD8+ T-cells. These findings could be of relevance in the search for pathogenetic mechanisms in motoneuron-specific diseases, such as ALS.

Animals↗
PubMed1998

Distribution of glutamate-, glycine- and GABA-immunoreactive nerve terminals on dendrites in the cat spinal motor nucleus.

The dendritic tree constitutes more than 93% of the receptive membrane area of a spinal motoneuron, yet little is known about its synaptic inputs. In this study we examined the distribution of glutamate-, GABA- and glycine-like immunoreactivity in boutons apposing dendrites in the L7 spinal cord motor nucleus, by use of postembedding immunohistochemistry on serial sections. We examined 799 boutons apposing 401 cross-sectioned dendrites of different calibre (range 0.2-15 microm), and 14 first-order (stem) dendrites. Thirty-five percent (35%) of the boutons were immunopositive for glutamate and 59% for GABA and/or glycine. Among the latter, 30% showed glycine immunoreactivity only and 24% were immunoreactive for both GABA and glycine. Very few were immunoreactive only for GABA (5%). As few as 6% of the boutons were judged as not enriched for any amino acid analysed. The fine structural characteristics of the boutons were in accordance with previous descriptions. The sample of dendrites was arranged in calibre bins in order to facilitate distribution analysis. Stem dendrites differed from the other bins, with a high total bouton covering (61%) and a high bouton density. Sixty-nine percent of the membrane covering was by glycine- and/or GABA-immunoreactive boutons, whereas 18% was covered by boutons enriched in glutamate. For non-stem dendrites, bouton covering fell from 33% to 12% with decreasing calibre. However, bouton apposition length decreased in parallel, yielding a fairly uniform bouton density among dendrites of different calibre. The lack of correlation between packing density and dendrite calibre was also evident when the sample of dendrites was broken down into subsamples based on content of amino acid immunoreactivity. The latter analysis also revealed that both the relative covering and density of boutons containing inhibitory amino acids (57%; glycine and/or GABA) and glutamate (38%), respectively, did not vary systematically with dendrite calibre. Combined, the data indicate that in non-stem dendrites the proportion of excitatory and inhibition inputs does not change systematically throughout the dendritic arborizations of spinal alpha-motoneurons. Thus, spinal motoneurons can, with respect to the general synaptic architecture, be divided into two main compartments, i.e. the proximal soma-juxtasomatic compartment (including stem dendrites) and the distal dendritic compartment. The proximal domain is under a powerful glycine and/or GABA influence. Finally, based on the data presented here and previously published data, it was calculated that spinal alpha-motoneurons receive in the range of 50-140 x 10(3) synaptic boutons.

Animals↗
PubMed1998

Changes in the mRNA expression pattern, with special reference to calcitonin gene-related peptide, after axonal injuries in rat motoneurons depends on age and type of injury.

The axotomy reaction in motoneurons after a peripheral nerve transection in the adult animal is characterized by a robust upregulation of alpha-calcitonin gene-related peptide (CGRP) messenger RNA (mRNA) together with mRNAs encoding cytoskeletal and growth-related proteins. Here we have examined whether the nature of the lesion and the age of the animal have any impact on the mRNA regulation in severed cells. Thus, the effect of a sciatic nerve transection in the adult rat was compared with, on the one hand, ventral root avulsions in the adult animal and, on the other hand, sciatic nerve transection in the immature animal. In the two latter cases, a proportion of the lesioned cells die and overall chances of regeneration are small. In the adult animal a sciatic nerve transection induced an upregulation of alpha-CGRP mRNA from the 3rd day after surgery and throughout the first 3 weeks (the time span of the study). Also low-affinity nerve growth factor receptor (p75) and growth-associated protein-43 (GAP-43) mRNAs were upregulated during the entire 3-week period. In contrast, after ventral root avulsion, the expression of alpha-CGRP, c-jun, and p75 mRNAs were normalized within the 1st postoperative week, while GAP-43 mRNA was still upregulated at 3 weeks. Galanin message-associated peptide (GMAP) mRNA became upregulated preferentially in motoneurons subjected to ventral root avulsion, while nitric oxide synthase (NOS) mRNA was expressed exclusively after the latter type of injury. In the immature animal, alpha-CGRP mRNA was downregulated after sciatic nerve transection in rats aged 3 days or 7 days at the time of surgery; while, in contrast, an upregulation was seen in 12- or 21-day-old animals. GAP-43 and c-jun mRNAs were upregulated in lesioned motoneurons of all ages, while GMAP mRNA was upregulated preferentially in lesioned motoneurons of early postnatal animals. p75 mRNA was expressed in unlesioned immature motoneurons until the age of 7-10 days. The downregulation of p75 mRNA in intact cells at this age coincided with a developmental switch in the ability of axotomized cells to express increased levels of p75 mRNA. No expression of NOS mRNA was detectable in lesioned cells of any of the age groups. These results show that the age of the animal and the type of axonal injury are indeed to a high degree influencing the changes seen in the protein expression pattern in axotomized rat motoneurons. The different responses in these paradigms suggest differences in the trophic response from surrounding glia or the trophic responsiveness of lesioned motoneurons. Also, the results may indicate different roles for the studied substances during the regenerative response of lesioned neurons. Of the substances studied here, upregulation of alpha-CGRP and p75 mRNAs best correlated with a possibility of axon regeneration.

Aging↗
PubMed1997

Neonatal sciatic nerve transection induces TUNEL labeling of neurons in the rat spinal cord and DRG.

Transection of a peripheral nerve in neonatal rats induces an extensive death of axotomized neurons. We demonstrate here that spinal motoneurons and sensory dorsal root ganglia neurons become TUNEL-labeled after sciatic nerve transection in neonatal rats, thus indicating that apoptotic mechanisms are involved in the death process. Interestingly, there is also a profound increase of TUNEL-labeled interneurons in the deep dorsal horn. This location suggests that an intact afferent input and/or contact with target cells is essential for interneuronal survival. Death of motoneurons and sensory neurons could be a result of the injury per se and/or the deprivation of neurotrophic substances, secondary to the loss of contact with target cells.

Animals↗
PubMed1996

GDNF mRNA in Schwann cells and DRG satellite cells after chronic sciatic nerve injury.

Glial cell line-derived neurotrophic factor (GDNF) exhibits neurotrophic properties on different types of neurones, including fetal motoneurones and embryonic neurones of sensory ganglia. We demonstrate that chronic injury to the adult rat sciatic nerve induces a rapid up-regulation of GDNF mRNA expression in Schwann cells proximal as well as distal to the injury site, and that expression of this mRNA remains at high levels for at least 5 months after injury. In addition, GDNF mRNA increases and remains high in satellite cells and Schwann cells of the affected L4/L5 DRGs. These findings suggest that GDNF is an important factor in the events that follow upon adult chronic primary sensory neurone injury, and possibly also after adult motoneurone axotomy.

Animals↗
PubMed1996

Qualitative and quantitative analysis of glycine- and GABA-immunoreactive nerve terminals on motoneuron cell bodies in the cat spinal cord: a postembedding electron microscopic study.

The distribution of glycine- and gamma-aminobutyric acid (GABA)-like immunoreactivity (LI) in nerve terminals on the cell soma of motoneurons in the aldehyde-fixed cat L7 spinal cord was examined using postembedding immunogold histochemistry in serial ultrathin sections. Quantitative examination of 405 terminals on eight neurons of alpha-motoneuron size in the L7 motor nuclei from one animal was performed. A majority of the terminals (69%) were immunoreactive to glycine and/or GABA. These terminals contained flat or oval synaptic vesicles, thus classifying them as F type or as C type in one case. In no case was a type-F terminal unlabeled for both glycine and GABA. Most of the immunolabeled terminals were immunoreactive to glycine only (62.5%), whereas 35.4% contained both glycine- and GABA-LI. A very small number of immunolabeled terminals (2%) were immunoreactive to GABA only. In those terminals, where glycine- and GABA-LI coexisted, the gold particle density for each amino acid was only half of that seen in boutons containing only one of the two amino acids. The involvement of glycine and GABA in postsynaptic inhibition of spinal alpha-motoneurons is discussed, with particular reference to the possibility that these two inhibitory amino acids may be coreleased from a significant proportion of the nerve terminals impinging on the cell bodies.

Animals↗
PubMed1996

The development of nerve connections in the peripheral nervous system.

The structural basis for the functions of the brain is the wiring of nerve cells. The wiring is achieved by 100 billion neurons via some 100,000 billion synaptic connections. Formation of this network is a formidable task which requires intricate, but also reliable mechanisms at work. It is generally recognized that the precise connections between nerve cells are accomplished by two different sorts of mechanisms. First, various molecular guidance cues lead outgrowing axons from specific areas to particular target regions which are rather broadly defined. The second stage includes an exact, point-to-point matching between each axon and the specific target neurons. This is achieved by an intricate interaction between the involved nerve cells. In the following, the attention will primarily regard the second type of events, but some aspects on the initial outgrowth of axons and axon guidance mechanisms will also be given. A large part of the description will focus on the neuromuscular junction, since it has been extensively used as a model for the study of synapse development.

Axons↗
PubMed1995

Expression of NMDA receptor mRNAs in rat motoneurons is down-regulated after axotomy.

The cytotoxic effects of glutamate via the N-methyl-D-aspartate (NMDA) receptor have been suggested to take part in the events leading to death of motoneurons after neonatal axotomy. By the use of in situ hybridization and immunohistochemistry we have investigated motoneuron mRNA expression of the NMDA receptor subunits NR1, NR2B and NR2D and of the NR1 subunit protein in two lesion models leading to partial motoneuron death: sciatic nerve transection early postnatally in the rat and ventral root avulsion in the adult rat. The results were compared with a lesion model with no subsequent death of motoneurons, i.e. sciatic nerve transection in the adult rat. All lesions were followed by down-regulation of the mRNAs for all studied subunits in severed motoneuron populations; down-regulation was detectable already at early stages postoperatively before any significant death had taken place. The strongest down-regulation was in fact seen in the lesion with the largest loss of motoneurons (ventral root avulsion). The reduction in the expression of NR1 mRNA was paralleled by a decrease in NR1 subunit protein. We conclude that down-regulation of NMDA receptor subunit expression is part of the acute response to axonal injury in motoneurons, whether or not neuronal death follows, and that the susceptibility of lesioned motoneurons to excitotoxic effects should be highest early after axonal injury.

Animals↗
PubMed1995

Fibroblast growth factors regulate calcitonin gene-related peptide mRNA expression in rat motoneurons after lesion and in culture.

In this study, we have investigated the effect of fibroblast growth factors (bFGF and FGF-5) and brain derived neurotrophic factor (BDNF) on the expression of calcitonin gene-related peptide (CGRP) in rat motoneurons in vivo and in vitro. Following sciatic nerve transection in adult rats, the levels of alpha-CGRP and beta-CGRP mRNA were up- and down-regulated respectively in axotomized motoneurons, revealed by in situ hybridization histochemistry. Local administration of 1 microgram bFGF was able to entirely abolish the up-regulation of alpha-CGRP mRNA, and to further down-regulate beta-CGRP. These effects, albeit less pronounced, were still evident with 0.2 micrograms bFGF. In contrast, bFGF did not attenuate the lesion-induced decrease of choline acetyltransferase (ChAT) mRNA. Administration of BDNF did not significantly alter the expression of CGRP or ChAT mRNA in axotomized motoneurons. Both alpha- and beta-CGRP mRNAs could be detected by PCR in enriched motoneuron cultures prepared from rat embryos at embryonic day 14-15. Comparing the amplification of alpha- and beta-CGRP mRNAs with that of mRNA encoding glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in parallel samples, we found that cultures treated with FGF-5 had a lower ratio of alpha- and beta-CGRP mRNA to GAPDH mRNA, than did control or BDNF-treated cultures. BDNF, on the other hand increased alpha-CGRP and decreased beta-CGRP mRNA levels, though these effects were moderate compared with the effects of FGF-5. The results obtained in this study suggest that members of the FGF family of growth factors influence the expression of CGRP in rat motoneurons, and that the increase of this neuropeptide induced by axotomy may, at least in part, be due to deprivation of these target-derived factors.

Animals↗
PubMed1995

Spinal axons in central nervous system scar tissue are closely related to laminin-immunoreactive astrocytes.

Although transected central nervous system axons fail to regrow after injuries in adult mammals, they send sprouts into the scar tissue that forms at the lesion. We have investigated the relation between scar cells, laminin-like immunoreactivity and cut spinal axons in two previously characterized spinal cord lesion types. Labeling with antisera to glial fibrillary acidic protein and laminin demonstrated that the scar tissue formed after lesions in the rat and cat dorsal and ventral funiculi showed prominent gliosis and strong laminin-like immunoreactivity four days to one year postlesion. Axonal sprouts in the scar, visualized with antibodies to neurofilament (RT97) or by tracing using fluorescein-conjugated dextran, were ensheathed by a thin layer of strongly laminin-immunoreactive tissue. Immunoelectron microscopy demonstrated that axons in the scar were ensheathed predominantly by astrocytes, and that the surface of the cells outlining the axons in the scar showed strong laminin-like immunoreactivity. Adhesive and neurite orienting properties in the scar tissue were assessed in an in vitro system where PC12 cells were cultured on spinal cord slices from dorsal funiculus-lesioned rats. Very few cells adhered to the spinal cord section except for the part where the scar tissue had formed, where numerous cells were attached. The PC12 cells that had adhered to the scar tissue were mainly seen in parts of the scar that showed laminin-like immunoreactivity and their neurites predominantly followed tissue showing laminin-like immunoreactivity. The close association between axonal sprouts and laminin-like immunoreactivity indicates a role for laminin in axonal growth and/or guidance in the injured spinal cord.

Animals↗
PubMed1994

Extrasynaptic localization of taurine-like immunoreactivity in the lamprey spinal cord.

Taurine is an endogenous amino acid that can occur in nerve terminals in the central nervous system and that can produce inhibitory neuronal responses. It is unclear, however, whether this amino acid can function as a synaptic transmitter. To examine the distribution of taurine at high anatomical resolution in a vertebrate, light and electron microscopic immunocytochemical postembedding techniques were applied to the lamprey spinal cord (Ichtyomyzon unicuspis and Lampetra fluviatilis), which contains many large, unmyelinated axons. The most intense immunolabeling occurred in a population of liquor-contacting cells (tanycytes), located around the central canal, which extended processes to the dorsal, lateral, and ventral margins of the spinal cord. In addition, a proportion of the taurine-immunoreactive cells contained gamma-aminobutyric acid (GABA)-like immunoreactivity. A moderate level of taurine immunoreactivity was also present in ependymal cells, located around the central canal, as well as in astrocytes throughout all regions of the spinal cord. At the ultrastructural level, the taurine immunoreactivity showed an even distribution in the cytoplasm of the labeled cells. In contrast to the glial labeling, neuronal cell bodies and axons exhibited very low levels of taurine labeling, which were similar to the level of background labeling. The synaptic vesicle clusters within the axons did not show any clear accumulation of taurine immunoreactivity. These results suggest that taurine may have metabolic roles in the lamprey spinal cord, and, as in other systems, it may take part in osmoregulation. However, the lack of immunolabeling in presynaptic elements is not consistent with a role of taurine as a synaptic transmitter.

Animals↗
PubMed1994

Immunohistochemical evidence for coexistence of glycine and GABA in nerve terminals on cat spinal motoneurones: an ultrastructural study.

Previous electrophysiological and pharmacological studies have suggested the involvement of both glycine and gamma-aminobutyric acid (GABA) as transmitters in the reflex pathway mediating recurrent inhibition of cat spinal motoneurones. By use of the postembedding immunogold technique and antibodies against glutaraldehyde-conjugated amino acids it is shown that glycine- and GABA-immunoreactive nerve terminals occur in contact with cell bodies of alpha motoneurone size, as well as in the surrounding neuropil in the motor nuclei of the cat spinal cord. A substantial proportion of these terminals harbours both glycine- and GABA-LI. The enrichment of immunolabelling over synaptic vesicles in such terminals strongly suggests that both of these amino acids are used as transmitter substances.

Animals↗
PubMed1994

Increased trkB mRNA expression by axotomized motoneurones.

It has been previously demonstrated that members of the neurotrophin family may prevent death of motoneurones following axotomy. Here we report that the expression of mRNA for full-length trkB, which is a signal transducing receptor for BDNF and NT-4, increases transiently in spinal motoneurones after axotomy in adult rats. Thus, transection of the sciatic nerve resulted in markedly increased levels of trkB mRNA in axotomized motoneurones three days postinjury, while the levels had returned to normal within three weeks. The data support that neurotrophins may be important for survival and/or regeneration of motoneurones after axon lesion.

Animals↗
PubMed1994

trkC-like immunoreactivity in the primate descending serotoninergic system.

In the search for substances with a potential role in plastic responses of spinal motoneurons we have studied the distribution of trkC-like immunoreactivity in the spinal cord of adult monkeys (Macaca fascicularis). The presence of trkC, which is a signal-transducing receptor for neurotrophin-3, was detected by the use of indirect immunofluorescence with a rabbit polyclonal antibody raised against a synthetic peptide corresponding to the carboxy-terminal domain of the mouse trkC-encoded protein, thus detecting only full-length signal-transducing receptors. trkC-immunoreactive fibres/varicosities could be found at all spinal cord levels and the densest innervation was found in the autonomic intermediolateral and Onuf's nuclei, but somatic motoneuron pools also received a significant contribution of trkC-immunoreactive fibres. Terminals immunoreactive for trkC were also seen in the dorsal horn. Double-labelling experiments revealed a high degree of coexistence between trkC- and 5-hydroxytryptamine (serotonin)-like immunoreactivity in all areas except in the dorsal horn. The results of the present study suggest that neurotrophic signalling with an influence on serotoninergic as well as non-serotoninergic inputs to the adult monkey spinal cord is at hand.

Animals↗
PubMed1994

Adhesive/repulsive properties in the injured spinal cord: relation to myelin phagocytosis by invading macrophages.

The vigorous ingrowth of cut CNS axons into peripheral nerve grafts indicates that the lack of neuronal regeneration within the brain and spinal cord cannot be explained merely by CNS neurons having an inherent weak regenerative capacity. Rather, the brain and spinal cord seem to contain molecules that inhibit axonal growth and, indeed, oligodendrocyte myelin has been demonstrated to effectively block nerve fiber growth. Macrophages can in vitro counteract this growth prohibitory property of the CNS. In this study we have examined the recruitment of macrophages and the removal of myelin in relation to neurite adhesive/repulsive properties in the injured spinal cord of adult rats. Cells immunoreactive for the macrophage-specific antibody ED1 rapidly invaded the lesion area after an incision in the dorsal or ventral funiculus. The number of macrophages remained high for several weeks in the scar tissue formed after both these injuries. This type of scar tissue has previously been reported to permit ingrowth and long-term persistence of axons. In the denervated area rostral to a dorsal funiculus transection, no or few ED1-immunoreactive cells were detected within the first month after the injury. However, at subsequent stages an increasing number of macrophages was found in this region. Myelin was removed much more rapidly at the site of the lesion than rostral to this (in the area undergoing Wallerian degeneration). In order to study adhesive/repulsive properties in the injured spinal cord in relation to local myelin content we employed an in vitro system in which PC12 cells were cultured on spinal cord slices. PC12 cells failed to adhere to sections from the intact spinal cord as well as to sections taken rostral to a dorsal funiculus transection, whereas many cells adhered to the glial scar formed at the lesion. Even at 15 months after the injury, very few PC12 cells attached to sections taken rostral to the transection despite the fact that no myelin could be detected in the denervated area at that time. These data suggest that, in addition to myelin-related growth inhibitory molecules, other factors may be involved in the failure of PC12 cells to adhere to the denervated spinal cord. Such factors could also affect axonal regrowth after spinal cord injury. The adhesion of PC12 cells to the lesion area may be a result of a locally high content of extracellular matrix molecules and/or cell adhesion molecules, factors which are not expressed in the region undergoing Wallerian degeneration.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Quantitative and qualitative aspects on the distribution of 5-HT and its coexistence with substance P and TRH in cat ventral medullary neurons.

By use of the indirect immunofluorescence technique the distributions of 5-hydroxytryptamine (5-HT)-, substance P- and thyrotropin-releasing hormone (TRH)-immunoreactive (IR) neurons have been studied in the midline raphe nuclei and nucleus reticularis lateralis of the caudal brainstem (levels P18.3-P8.5; according to Berman (1968), in the cat, after treatment with colchicine. In addition, by use of the double-labelling technique, the coexistence between 5-HT-, substance P- and TRH-like immunoreactivity (LI) in these neurons was analysed. The results show that cell bodies in the midline raphe nuclei and nucleus reticularis lateralis contain 5-HT-, substance P- and TRH-LI. 5-HT-IR cells were more abundant than peptidergic neurons in all areas analysed. Quantitative estimations indicated that the total number of 5-HT-IR cells in the regions studied was about 17 x 10(3), while the corresponding numbers for substance P- and TRH-IR cells were 11 x 10(3) and 12 x 10(3), respectively. From double-labelled sections it was concluded that the vast majority of peptidergic cells also contained 5-HT-LI (87-100%). However, a subpopulation of 5-HT-IR neurons lacked peptide-LI (10-55%). The degree of coexistence varied with the brainstem level, in that neurons at more rostral locations showed a lower incidence of coexistence between 5-HT and peptide(s). The presence of all three compounds in one and the same cell body could also be demonstrated. In summary, 5-HT-, substance P- and TRH-IR cell bodies were encountered in medullary nuclei known to contain neurons with projection to the spinal cord. A high degree of coexistence between the compounds was demonstrated in these nuclei. The obtained results fit well with earlier studies on the patterns of distribution and peptide colocalization of 5-HT fibres in the spinal cord. The existence of biochemically distinct neuronal subpopulations within the 5-HT bulbospinal pathway is discussed.

Animals↗