(1) These results provide the first demonstration that embryonic neurons supply agrin-like molecules to the synapses they form with embryonic muscle cells.
(2) The stimulation of the expression of agrin-related molecules in these long-term cultures requires the presence of chick embryo extract or fetal calf serum.
(3) Agrin, a protein isolated from the synapse-rich electric organ of Torpedo californica, induces the formation of specializations on myotubes in culture which resemble the post-synaptic apparatus at the vertebrate skeletal neuromuscular junction.
(4) Agrin enriched by immunoaffinity chromatography from the central nervous system induced large numbers of AChR aggregates on cultured myotubes.
(5) We conclude that agrin released by rat motor neurons induced the chick myotubes to aggregate AChRs.
(6) Agrin-induced formation of AChR aggregates was not prevented by inhibition of protein synthesis, consistent with our previous results that agrin-induced accumulation of AChRs occurs by lateral migration.
(7) The rat agrin protein is concentrated at synapses, where it may play a role in development and regeneration.
(8) Immunofluorescence shows that on myotubes incubated with agrin at 4 degrees C, agrin binds in a uniform, finely punctate pattern that correlates poorly with the distribution of AChRs.
(9) By contrast, actin (visualized with fluorescein-phalloidin) and tropomyosin did not show specific associations with agrin-induced AChR clusters.
(10) In the present study we examined the role of extracellular matrix components in agrin-induced differentiation.
(11) Myotubes stimulated with agrin at 37 degrees C for greater than or equal to 2 hr show a coclustering of agrin binding sites and AChRs.
(12) The accumulation of AChE and BuChE into agrin-induced aggregates occurred in the absence of any change in the amount, rate of synthesis, accumulation, and release, or molecular forms of either enzyme.
(13) We also characterized the expression of muscle-derived agrin-like molecules at clusters of AChR.
(14) Here I report that the major agrin-like proteins from the nervous system and other tissues of the chicken are immunochemically and biochemically similar.
(15) Thus, in developing muscle, agrin or a closely related molecule (a) is expressed before AchR clusters are detected; (b) is colocalized with the earliest AchR clusters formed; and (c) can be expressed in muscle and at sites of high AchR density independently of innervation.
(16) These results demonstrate that expression of a single gene encoding agrin confers receptor clustering that is restricted to specific sites of cell-muscle contact.
(17) Other lines of study have provided clues as to how nerve-derived (extracellular) AChR-cluster inducing factors such as agrin might activate 43k-driven postsynaptic membrane specialization.
(18) However, as dorsal and ventral premuscle masses condensed (stage 22-23), mesenchymal immunoreactivity for laminin and agrin-like proteins, but not the proteoglycan, became concentrated in these myogenic regions.
(19) Immunofluorescent staining with an anti-agrin antibody reactive at Rana but not at Xenopus neuromuscular junctions was positive only at cross-species nerve-muscle contacts involving Rana neurons.
(20) Here we present evidence that agrin is highly concentrated in the cell bodies of motor neurons and is transported to axon terminals which is consistent with the agrin hypothesis.
Protein
Definition:
(n.) A body now known as alkali albumin, but originally considered to be the basis of all albuminous substances, whence its name.
Example Sentences:
(1) All mutant proteins could associate with troponin I and troponin T to form a troponin complex.
(2) By electrophoresis and scanning densitometry, actin was found to constitute about 4% to 6% of the total cellular protein in the human corneal epithelium.
(3) Comparison of the S100 alpha-binding protein profiles in fast- and slow-twitch fibers of various species revealed few, if any, species- or fiber type-specific S100 binding proteins.
(4) Standardization is possible after correction by the protein content of each individual section.
(5) The hypothesis that proteins are critical targets in free radical mediated cytolysis was tested using U937 mononuclear phagocytes as targets and iron together with hydrogen peroxide to generate radicals.
(6) These studies led to the following conclusions: (a) all the prominent NHP which remain bound to DNA are also present in somewhat similar proportions in the saline-EDTA, Tris, and 0.35 M NaCl washes of nuclei; (b) a protein comigrating with actin is prominent in the first saline-EDTA wash of nuclei, but present as only a minor band in the subsequent washes and on washed chromatin; (c) the presence of nuclear matrix proteins in all the nuclear washes and cytosol indicates that these proteins are distributed throughout the cell; (d) a histone-binding protein (J2) analogous to the HMG1 protein of K. V. Shooter, G.H.
(7) Following central retinal artery ligation, infarction of the retinal ganglion cells was reflected by a 97 per cent reduction in the radioactively labeled protein within the optic nerve.
(8) Increased dietary protein intake led to increased MDA per nephron, increased urinary excretion of MDA, and increased MDA per milligram protein in subtotally nephrectomized animals, and markedly increased the glutathione redox ratio.
(9) The presence of O-glycosidic linkages between carbohydrate and protein in the DF3 antigenic site was further supported by the presence of NaBH4-sensitive sites.
(10) Cyclic AMP stimulated phosphorylation by [gamma-32P]ATP of two proteins of apparent Mr = 20,000 and 7,000 that were concentrated in sarcoplasmic reticulum, but the stimulation was markedly dependent on the presence of added soluble cyclic AMP-dependent protein kinase.
(11) The quaternary structure of ribonucleotide reductase of Escherichia coli was investigated, with the use of purified B1 and B2 proteins and bifunctional cross-linking agents.
(12) This induction is sensitive to actinomycin D but not to protein synthesis inhibitor puromycin, indicating an effect of estradiol at the transcriptional level, possibly mediated by the estrogen receptor.
(13) The promoters of the adenovirus 2 major late gene, the mouse beta-globin gene, the mouse immunoglobulin VH gene and the LTR of the human T-lymphotropic retrovirus type I were tested for their transcription activities in cell-free extracts of four cell lines; HeLa, CESS (Epstein-Barr virus-transformed human B cell line), MT-1 (HTLV-I-infected human T cell line without viral protein synthesis), and MT-2 (HTLV-I-infected human T cell line producing viral proteins).
(14) This clinical improvement was also associated with a decrease of erythrocyte sedimentation rate (p less than 0.001), decrease of C-reactive protein (p less than 0.0001) and with improvement of anaemia (p less than 0.05).
(15) The mobility on sodium dodecyl sulfate-polyacrylamide gel electrophoresis is anomalous since the undenatured, cross-linked proteins have the same Stokes radius as the native, uncross-linked alpha beta gamma heterotrimer.
(16) We also show that the gene of the main capsid protein is expressed from its own promoter in an Escherichia coli strain.
(17) Western blot analysis of these mitochondria using an antibody against carnitine palmitoyltransferase II purified from beef heart demonstrates a 68-kDa protein, which under ischemic conditions apparently is decreased by 2 kDa.
(18) Fifteen sera ICA-IgG and ICA-protein A positive with high titres remained positive thereafter.
(19) Patient or fetal cord serum is commonly used as a protein supplement to culture media used in in-vitro fertilization (IVF).
(20) Using the oocyte system to express size-fractionated mRNA, we have also determined that the mRNA coding for this protein is between 1.9-2.4 kilobases in length.