Biomedical subjects

K W Tsim

Publications and source records attributed to K W Tsim.

At least 37 records · Page 2Linked to original sources

PubMed1998

Cloning of cDNAs encoding xenopus neuregulin: expression in myotomal muscle during embryo development.

Neuregulin has diverse functions in neural development, and one of them is the up regulation of acetylcholine receptors (AChRs) at the muscle fiber during the formation of neuromuscular junctions. Although the primary source of neuregulin is derived from motor neuron, the expression in muscle has also been demonstrated. The precise role of neuron-derived and muscle-derived neuregulin during the early stages of development is not known. In order to study the role of neuregulin during early embryo development, we isolated the cDNAs encoding Xenopus neuregulin by cross-hybridization with its chick homologue. The amino acid sequence of Xenopus protein is 50 to 70% identical to members of the neuregulin family. The cDNAs encoding different isoforms of Xenopus neuregulin were identified, and these isoforms have two variation sites: (i) the spacer domain with either 0 or 43 amino acid insertion; and (ii) the C-terminus of EGF-like domain to derive either alpha or beta isoform. When the EGF-like domain of Xenopus neuregulin was expressed in mammalian cells, the recombinant protein was able to induce the expression of AChR and the tyrosine phosphorylation of erbB receptors in cultured myotubes. An approximately 6.5 kb transcript corresponding to neuregulin was detected in RNA isolated from brain and muscle. Various splicing variants were expressed in different Xenopus tissues. In situ hybridization showed a strong expression of neuregulin in developing brain and spinal cord of Xenopus embryo. In addition, it was also prominently expressed in the myotomal muscle. These data suggest that in addition to motor neurons, the postsynaptic muscle cells can also contribute neuregulin for synaptogenesis.

Amino Acid Sequence↗

PubMed1998

Over-expression of acetylcholinesterase stimulates the expression of agrin in NG108-15 cells.

Several lines of evidence suggest the non-cholinergic functions of acetylcholinesterase (AChE) in promoting neurite outgrowth of cultured neurons and in inducing the postsynaptic specializations of developing neuromuscular junctions. In order to support the hypothesis, a cholinergic synapse-forming cell line NG108-15 was over-expressed with chick AChE by cDNA transfection. The transfected NG108-15 cells secreted a approximately 105-kDa protein, recognized by anti-AChE antibody in Western blot analysis, corresponding to the chick AChE catalytic subunit. Over 80% of the recombinant enzyme were secreted into the conditioned medium and they were enzymatically active. In the NG108-15 cell-muscle co-cultures, the AChR-aggregating activity of NG108-15 cells was increased by the over-expression of AChE. The increase in AChR-aggregating activity of the transfected NG108-15 cells paralleled with the increase in agrin and neurofilament expression of the transfected cells as determined by their corresponding antibodies. However, the intracellular cAMP level remained unchanged in the AChE over-expressed NG108-15 cells. These results support the hypothesis that AChE could play a role in promoting neuron differentiation.

Acetylcholinesterase↗

PubMed1998

The calcitonin gene-related peptide-induced acetylcholinesterase synthesis in cultured chick myotubes is mediated by cyclic AMP.

In vertebrate neuromuscular junctions, post-synaptic specialization includes aggregation of acetylcholine receptors (AChRs) and acetylcholinesterase (AChE). The motor nerve provides soluble factors and electrical activity to achieve this striking localization of AChRs/AChE. Calcitonin gene-related peptide (CGRP), a neuropeptide synthesized by motor neurons, is able to stimulate the expression of AChR in cultured myotubes. Similar to AChR regulation, synthesis of AChE in cultured chick myotubes is also stimulated by CGRP. Application of CGRP onto cultured myotubes stimulated the accumulation of intracellular cyclic AMP (cAMP) as well as the expression of AChE mRNA and protein. However, the enzymatic activity of AChE remained unchanged. In cultured myotubes, various drugs affecting the intracellular level of cAMP, such as N6,O2'-dibutyryladenosine 3',5'-cyclic monophosphate, cholera toxin, and forskolin, could mimic the effect of CGRP in stimulating the expression of AChE. When myotubes were transfected with cDNA encoding constitutively active mutant Galpha(s), the intracellular cAMP synthesis was increased. The increase in cAMP level was in parallel with an increase in the expression of AChE, whereas transfection of active mutant Galpha(i) cDNA decreased the cAMP level as well as the AChE expression. In addition, expression of collagen-tailed AChE was up-regulated by the cAMP pathway. These findings indicated that CGRP-induced AChE regulation is mediated by the cAMP pathway and represented the first evidence to suggest that the regulation of mRNA synthesis of AChR and AChE can be mediated by the same neuron-derived factor.

Acetylcholinesterase↗

PubMed1997

Muscle-derived neurotrophin-3 increases the aggregation of acetylcholine receptors in neuron-muscle co-cultures.

Neurotrophins, a group of protein ligands that are structurally related to the prototype nerve growth factor (NGF), are prominently expressed in the skeletal muscle during the critical period of synapse formation. In the present study, we utilized a co-culture system of NG108-15 cells expressing the Trk receptors and C2C12 myotubes expressing the individual neurotrophins to examine whether these factors can act in a target-derived manner to influence the postsynaptic specializations. Our findings demonstrated that muscle-derived neurotrophin-3 (NT-3) has the unique ability to enhance the aggregation of acetylcholine receptors (AChRs) on the myotubes following co-culture with NG108-15 cells expressing TrkC. Taken together, our findings suggest that NT-3 can act as a retrograde factor to modulate the postsynaptic specializations.

Animals↗

PubMed1997

NG108-15 cells express neuregulin that induces AChR alpha-subunit synthesis in cultured myotubes.

A cholinergic neuroblastoma x glioma hybrid cell line NG108-15 is able to form functional synapses, and contains both AChR-aggregating and AChR-inducing activities when cocultured with myotubes. Several lines of evidence indicate that the AChR-inducing activity of NG108-15 cells is derived from neuregulin. The conditioned medium of cultured NG108-15 cells induced the expression of AChR alpha-subunit as well as the tyrosine phosphorylation of erbB-3 receptor. NG108-15 cells expressed neuregulin with a protein of approximately 100 kDa in size and transcripts of approximately 6.8 kbp, approximately 2.6 kbp and approximately 1.8 kbp; mRNAs encoding beta1 and alpha2 isoforms of neuregulin were revealed. NG108-15 cells were induced to differentiate by chemicals, and the chemical-induced differentiation of NG108-15 cells increased the level of neuregulin mRNA expression approximately 3-fold while the expression of a housekeeping gene remained relatively unchanged. The activity of neuregulin in the conditioned medium of NG108-15 cells was reduced by treating the medium with heparin and anti-neuregulin antibody. In addition, NG108-15 cells were transfected with antisense neuregulin cDNA and its expression of neuregulin was reduced, while its neuregulin-induced tyrosine phosphorylation activity was markedly decreased. This is the first direct demonstration that the NG108-15 cell-induced AChR upregulation on cultured myotubes is mediated by neuron-derived neuregulin.

Animals↗

PubMed1997

NG108-15 cells induce the expression of muscular acetylcholinesterase when co-cultured with myotubes.

Although muscular activity has been demonstrated to regulate the expression of acetylcholinesterase (AChE) in cultured myotubes, the exact role of the presynaptic terminus in regulating AChE expression at the neuromuscular junctions is not known. A chimeric co-culture of neuroblastoma x glioma hybrid NG108-15 cells with chick myotubes was established. By using chick-specific anti-AChE antibody, a protein of approximately 105 kDa in size corresponding to chick AChE catalytic subunit was revealed by Western blot analysis from the extracts of neuron-muscle co-cultures. In the co-cultures, NG108-15 cells induced the up regulation of muscle AChE expression by approximately 2.5-fold, while the control protein, chick muscle alpha-actinin at approximately 100 kDa, remained relatively unchanged. The NG108-15 cell-induced muscle AChE expression in the co-cultures was persistent when the muscular activity was blocked by alpha-bungarotoxin. In order to determine the AChE-inducing activity derived from NG108-15 cells, the cultured chick myotubes were treated with either conditioned medium of NG108-15 cells or its cell lysate. However, the muscle AChE, both in protein and activity levels, remained relatively unchanged. Our finding suggests that an AChE-inducing factor(s) is derived from the neuroblastoma cells in the co-cultures, but that may require the nerve-muscle contacts in culture.

Acetylcholinesterase↗

PubMed1997

Denervation decreases the ipsilateral expression of AChE in chick lumbaric motor neurons.

In vertebrate neuromuscular junctions, acetylcholinesterase (AChE; EC 3.1.1.7) is highly concentrated at the synaptic basal lamina and the postsynaptic muscle fiber. The postsynaptic muscle cell is the primary source of AChE. However, several lines of evidence indicate that the presynaptic motor neuron is able to synthesize and secrete AChE at the neuromuscular junctions. By using anti-AChE monoclonal antibody in immunohistochemical staining, we found that the AChE-positive cells were labeled only at the motor neurons of the chick spinal cords. When the protein extract of chick spinal cords was analyzed by a Western blot analysis, a protein band of approximately 105 kDa was recognized. In denervated chicks, the expression of motor neuron AChE, as recognized on a Western blot, decreased by approximately 50% 4 days after denervation. The AChE expression in denervated chick spinal cords, however, was restored to control level 10 days after denervation. The decreased AChE expression was restricted to the ipsilateral side of the denervated chick spinal cord while the contralateral side was relatively unchanged. In comparison with the contralateral side, the level of AChE protein and enzymatic activity expressed in the ipsilateral spinal cord was approximately 50% lower. This is the first demonstration to show that the ipsilateral and contralateral sides of chick spinal cords respond differently after nerve denervation.

Acetylcholinesterase↗

PubMed1997

The EGF-like domain of chick acetylcholine receptor-inducing activity (ARIA) contains its full biological activity.

Acetylcholine receptor-inducing activity (ARIA) is a glycoprotein initially purified from chick brain based on its ability to increase the synthesis of acetylcholine receptor (AChR) on cultured myotubes. cDNA encoding ARIA contains different domains and the functions of each domain in ARIA activity are not known. We used molecular genetic methods to construct a chimeric fusion protein, designated ARIA(S136-K205)-Fc, that contained the leader sequence, the EGF-like domain of chick ARIA (S136 to K205) and the Fc region of human immunoglobulin. The ARIA(S136-K205)-Fc cDNA was transfected into HEK 293 cells and stable cell lines secreting soluble ARIA(S136-K205)-Fc were obtained. The secreted ARIA(S136-K205)-Fc has a molecular mass of approximately 60 kDa and can be purified by protein G chromatography. The purified ARIA(S136-K205)-Fc retained its full biological activity of chick ARIA that included: (i) induction of tyrosine phosphorylation of erbB 3 receptor in C2C12 myotubes; and (ii) approximately 12-fold stimulation of AChR alpha-subunit mRNA synthesis when applied onto cultured chick myotubes. This Fc-tagged ARIA could be rapidly purified and provides a very useful ligand for identifying its true receptor(s) on muscle cell surface.

Animals↗

PubMed1997

Chick muscle expresses various ARIA isoforms: regulation during development, denervation, and regeneration.

Acetylcholine receptor inducing activity (ARIA) is a glycoprotein released from the motor neuron to stimulate the synthesis of acetylcholine receptors (AChRs) on the postsynaptic muscle fiber. Transcripts encoding ARIA were detected not only in brain but also in muscle, and immunohistochemical staining showed that muscle-derived ARIA was restricted to the neuromuscular junctions. RT-PCR analysis revealed three biological active isoforms of ARIA in chick muscle, namely ARIA beta 1, ARIA alpha 2, and ARIA beta 2 that were classified based on their variation in the carboxylterminus of the EGF-like domain. The expression of these ARIA isoforms in muscle change during development denervation, and nerve regeneration. ARIA beta 1, ARIA alpha 2, and ARIA beta 2 were expressed in embryonic and young chick muscles, while ARIA beta 1 was the major isoform expressed in adult chicken. The embryonic-like expression of ARIA alpha 2 and ARIA beta 2 was induced after nerve injury in adult chicken. However, the prominent expression of ARIA beta 1 in adult-like profile was restored after nerve regeneration. A splicing variation in the region between Ig-like and EGF-like domains of ARIA was also revealed; a zero-amino acid insertion (ARIASP0), a 17-amino acid insertion (ARIASP17), or a 34-amino acid insertion (ARIASP34) were identified. Unlike ARIASP0, the expression of ARIASP17 and ARIASP34 was found in muscle and sciatic nerve only. The expression of ARIASP0, ARIASP17, and ARIASP34 in chick muscle remained unchanged during development and after nerve injury. Moreover, the specific expression of these ARIA isoforms in cultured myotubes was not affected by drug treatments or by coculturing with neurons. Our findings provide strong evidence that muscle ARIA may play an important role in the formation of neuromuscular junctions.

Aging↗

PubMed1997

Antisense agrin cDNA transfection blocks neuroblastoma cell-induced acetylcholine receptor aggregation when co-cultured with myotubes.

A neuroblastoma x glioma hybrid cell line, NG108-15, was able to induce the aggregation of AChRs when co-cultured with myotubes. NG108-15 cells in culture expressed agrin, producing a protein of approximately 220 kDa and a transcript of approximately 8.0 kb. The mRNA encoding the agrin isoform having no amino acid insertion at either the Y or the Z site, namely agrin0.0, was the only transcript detected in NG108-15 cells when they were cultured alone or co-cultured with myotubes. NG108-15 cells could be induced to differentiate by chemical treatment, and the chemical-induced differentiation of NG108-15 cells increased the level of agrin mRNA expression approximately fourfold while the expression of a housekeeping gene remained relatively unchanged. The increase in agrin expression of differentiated NG108-15 cells paralleled the increase in AChR-aggregating activity of differentiated NG108-15 cells, indicating that the agrin derived from NG108-15 cells could be the receptor-aggregating factor. In addition, we created a stable clonal NG108-15 cell line that was transfected with antisense agrin cDNA and its expression of agrin was abolished, while its AChR-aggregating activity was completely lost when co-cultured with myotubes. This is the first direct demonstration that NG108-15 cell-induced AChR aggregation on cultured myotubes is mediated by neuron-derived agrin.

Agrin↗

PubMed1997

A role of midkine in the development of the neuromuscular junction.

Midkine (MK) is a member of a family of developmentally regulated neurotrophic and heparin-binding growth factors. It is expressed during the midgestation period in a retinoid-acid dependent manner during embryogenesis in the mouse. In vitro, it promotes neurite outgrowth from spinal cord neurons and cell migration. It expression is strongest in the central nervous system, thus suggesting a function for this protein in neural development. In this study, the role of MK in synaptogenesis was examined in the Xenopus system. A Xenopus MK cDNA was cloned from an embryonic library encompassing neurulation and synaptogenesis stages. By Northern blot analysis, MK mRNA was detected from the onset of neurulation and throughout the stages of synaptogenesis in the Xenopus embryo. This suggests that MK is also an important growth regulator in Xenopus embryogenesis. To study the function of MK in the development of the neuromuscular junction (NMJ), fusion proteins were made and their ability to induce the formation of acetylcholine receptor (AChR) clusters in cultured muscle cells was studied. Beads coated with MK strongly induce AChR clustering. When nerve-muscle cocultures were labeled with antibodies made against the MK fusion protein, MK immunoreactivity was detected at the NMJ. Unlike heparin-binding growth-associated molecule (HB-GAM), another member of this growth factor family, MK expression cannot be detected in the muscle but is present in spinal cord neurites. Consistent with these in vitro data is the observation that MK mRNA is only localized in the central nervous system but the protein is deposited at the intersomitic junction where the NMJ is located in vivo. Exogenously applied MK does bind to the heparan sulfate proteoglycan on the surface of Xenopus muscle cells. Agrin, a heparan-sulfate proteoglycan that induces the formation of AChR clusters in cultured muscle cells, binds strongly to MK. Bath application of MK in conjunction with agrin results in a change in the pattern of AChR clustering induced by agrin alone. These data suggest that MK is a neuron-derived factor that participates in the signal transduction process during NMJ development.

Agrin↗

PubMed1997

Expression and localization of endothelin converting enzyme in rat vas deferens.

Endothelins (ETs) are a family of vasoconstrictor and mitogenic peptides originally isolated from the endothelial cells. Three isoforms of ET, namely ET-1, ET-2 and ET-3, are generated from their respective intermediate precursors big ETs through specific endoproteolytic cleavage by endothelin converting enzyme (ECE). Using reverse-transcription polymerase chain reaction (RT-PCR), we have isolated a cDNA encoding for ECE from both the prostatic and epididymal halves of rat vas deferens. In situ hybridization using digoxigenin-labeled ECE cDNA probe demonstrated that ECE mRNA is preferentially localized in the inner longitudinal smooth muscle layer adjacent to submucosa region of rat vas deferens. Both ET-1 and big ET-1 at 30 nM potentiated electrically stimulated contractile response of prostatic vas deferens. Pre-incubation of tissue with a metalloprotease ECE inhibitor phosphoramidon (10 microM) strongly inhibited the response to big ET-1, but not to ET-1. On the other hand, big ET-1 failed to elicit contractile response of epididymal vas deferens. Phosphoramidon alone did not affect both the basal and electrically stimulated contractile responses in vas deferens. These data indicate that the circulating ET-1 and its immediate precursor big ET-1 could differentially regulate smooth muscle contractions in the prostatic and epididymal vas deferens of the rat.

Animals↗

PubMed1997

A globular, not asymmetric, form of acetylcholinesterase is expressed in chick motor neurons: down-regulation toward maturity and after denervation.

In vertebrate neuromuscular junctions, the postsynaptic specializations include the accumulation of acetylcholinesterase (AChE) at the synaptic basal lamina and the muscle fiber. Several lines of evidence indicate that the presynaptic motor neuron is able to synthesize and secrete AChE at the neuromuscular junctions. By using anti-AChE catalytic subunit, anti-butyrylcholinesterase (BuChE) catalytic subunit, and anti-AChE collagenous tail monoclonal antibodies, we demonstrated that the motor neurons of chick spinal cord expressed AChE in vivo and the predominant AChE was the globular form of the enzyme. Neither asymmetric AChE nor BuChE was detected in the motor neurons. The molecular mass of AChE catalytic subunit in the motor neuron was approximately 105 kDa, which was similar to that of the globular enzyme from low-salt extracts of muscle; both of them were approximately 5 kDa smaller than the asymmetric AChE from high-salt extracts of muscle. The level of AChE expression in the motor neurons decreased, as found by immunochemical and enzymatic analysis, during the different stages of the chick's development and after nerve lesion. Thus, the AChE activity at the neuromuscular junctions that is contributed by the presynaptic motor neurons is primarily the globular, not the asymmetric, form of the enzyme, and these contributions decreased toward maturity and after denervation.

Acetylcholinesterase↗

PubMed1997

Agrin-deficient myotube retains its acetylcholine receptor aggregation ability when challenged with agrin.

Agrin is a synapse-organizing molecule that mediates the nerve-induced aggregation of acetylcholine receptors (AChRs) and other postsynaptic components at the developing and regenerating vertebrate neuromuscular junctions. At the neuromuscular junction, three different cell types can express agrin, i.e., neuron, muscle, and Schwann cell. Several lines of evidence suggested that neuron-derived agrin is the AChR-aggregating factor, but the possible roles of muscle-derived agrin in the formation of AChR aggregate are not known. By using the recombinant DNA method, a clonal stable C2C12 cell line transfected with antisense agrin cDNA was created. RNA dot blot and western blot analysis indicated that the expression of agrin in the transfected cell was abolished by DNA transfection. When the agrin-deficient C2C12 cells were induced to form myotubes and subsequently cocultured with agrin cDNA transfected fibroblasts, AChR aggregates were formed in the cocultures. In addition, acetylcholinesterase (AChE) aggregates in agrin-deficient myotubes were also induced by exogenous agrin and the AChE aggregates were colocalized with the AChR aggregates. The agrin-deficient myotubes could also respond to neuron-induced AChR aggregation after coculturing with neuroblastoma cells. Thus, the agrin-deficient myotubes retain their ability to exhibit the agrin- or neuron-induced AChR aggregation. This result suggests that the formation of postsynaptic specializations during development and regeneration is mediated by neuron-derived agrin but not the agrin from muscle.

Acetylcholinesterase↗

PubMed1996

Calcitonin gene-related peptide increases the expression of acetylcholinesterase in cultured chick myotubes.

Calcitonin gene-related peptide (CGRP), a neuropeptide may play a role in the formation of neuromuscular junctions is synthesized by the motor neurons and is able to stimulate the expression of acetylcholine receptor (AChR) in cultured myotubes. By using antibody and DNA probe that are specific for acetyl cholinesterase (AChE), we reported the expression of AChE could also be stimulated by CGRP in cultured chick myotubes. After CGRP application, the amount of AChE protein, that showed a molecular weight of approximately 105 kDa as recognized by the anti-AChE monoclonal antibody, was increased by approximately 1.7-fold. Two transcripts encoding AChE, approximately 4.8 and approximately 6.0 kb, were identified and their levels of expression were increased to approximately 3-fold after treatment with CGRP. However, the total AChE enzymatic activity in the CGRP-treated myotubes was unchanged. These evidences suggest that most of the CGRP-induced AChE proteins in the cultured chick myotubes are the inactive pool of enzyme.

Acetylcholinesterase↗

PubMed1996

Cerebellar granule cells express a specific isoform of agrin that lacks the acetylcholine receptor aggregating activity.

Agrin is a synapse-organizing molecule that mediates nerve-induced aggregation of acetylcholine receptors and other postsynaptic components at the developing and regenerating vertebrate neuromuscular junctions. Several lines of evidence indicate that agrin might play a similar role in directing the organization of postsynaptic specifications of neuron-neuron synapse formation. Here we used immunological methods and polymerase chain reaction to identify the expression of agrin protein and alternatively spliced mRNA isoforms in the culture of rat granule cells. Anti-agrin polyclonal antibody labeled the cultured granule cells and it detected a protein of over 200 kDa in size from the lysate of the cultured cells. Analysis by polymerase chain reaction showed that the granule cells in culture expressed predominantly the B0 isoform of agrin mRNA. When granule cells were co-cultured with primary chick myotubes, there was no detectable effect on the aggregation of acetylcholine receptors on the surface of the myotubes. These results show that the cerebellar granule cells, similar to motor neurons in vitro, express and secrete agrin but it lacks the acetylcholine receptor aggregating activity.

Agrin↗

PubMed1996

Extracellular and asymmetric forms of acetylcholinesterase are expressed on cholinergic and noncholinergic terminal neuropil of the developing chick retina.

Only two out of four major acetylcholinesterase (AChE) subbands in the inner plexiform layer (IPL) of vertebrate retinae correspond to sites of cholinergic synaptic transmission, as has been shown by the co-distribution of AChE and choline acetyltransferase (ChAT) staining. The function and molecular identity of AChE in non-cholinergic subbands is unknown. We have used immunocytochemical methods to compare the development of asymmetric or extracellularly localized AChE with that of total AChE and ChAT in embryonic and adult chicken retinae. After injection of the AChE-specific monoclonal antibody 3D10 into the vitreous body of live embryos, a method that labels only extracellular AChE, five subbands in the IPL were labelled, whereas cell somata or their radial processes remained unstained. In contrast, the entire cell including processes was immunoreactive, when the 3D10 antibody was applied to permeabilized cryosections, suggesting that in cell bodies the enzyme is exclusively localized intracellularly. Compared with total AChE, detection of asymmetric AChE with the monoclonal antibody 6B6 was delayed, first being seen in cells of the inner nuclear layer and finally appearing on all subbands, reflecting more closely the course of synaptogenesis. Thus, extracellular and asymmetric forms of AChE are predominantly found on the terminal arbor neuropil of both cholinergic and non-cholinergic IPL subbands. These data show a differential distribution of extra- and intracellular AChE and suggest novel roles for the AChE in non-cholinergic IPL subbands.

Acetylcholinesterase↗

PubMed1996

Differential expression of ciliary neurotrophic factor receptor in skeletal muscle of chick and rat after nerve injury.

The activities of ciliary neurotrophic factor (CNTF) were initially thought to be restricted to cells in the nervous system. However, the recent identification of its receptor specificity-conferring alpha component (CNTFR alpha) in skeletal muscle has provided the clue to the unexpected actions of CNTF in the periphery. In the present study, we demonstrated that the mRNA expression of CNTFR alpha in chick skeletal muscle was decreased by approximately 10-fold after nerve transection; this finding is in sharp contrast to the dramatic up-regulation observed in denervated rat muscle. As a first step toward investigating the differential regulation of CNTFR alpha in chick and rat, we examined the mRNA expression of CNTFR alpha in different types of muscle following nerve injury in young and adult animals. Our findings demonstrated that the differential expression of CNTFR alpha observed in denervated skeletal muscle of the chick and rat was not dependent on age or muscle type. The temporal profile of the changes in CNTFR alpha expression was, however, dependent on the age of the chick as well as the types of muscles. Furthermore, the low level of CNTFR alpha expression observed in denervated chick muscle recovered to almost control levels in regenerating skeletal muscle. Taken together, our findings provided the first extensive analysis on the mRNA expression of CNTFR alpha and the alpha subunit of the acetylcholine receptor in various skeletal muscles of the chick following nerve injury and regeneration.

Aging↗