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Biomedical subjects

L Ziskind-Conhaim

Publications and source records attributed to L Ziskind-Conhaim.

24 records · Page 2Linked to original sources
PubMed1984

Irreversible inhibition of phospholipid methylation and protein carboxymethylation does not alter acetylcholine receptor function in muscle cells.

The role of methyltransferase (MT) reactions in acetylcholine (ACh)-evoked depolarization and contraction in primary chick myotubes was determined by using a mixture of erythro-9-(2-hydroxy-3-nonyl) adenine, homocysteine thiolactone, and adenosine which together inhibit the activity of MT. Carboxy-MT and lipid-MT activities were inhibited irreversibly by 91 and 100%, respectively. ACh-induced muscle contraction was also inhibited within 10 min after application of the inhibitor mixture. However, in contrast to permanent inhibition of MT activities, inhibition of acetylcholine receptor (AChR)-dependent muscle contraction was reversible. Moreover, physiological studies showed that the inhibitor mixture had no effect on resting membrane potential or ACh-induced depolarization or desensitization. These results suggest that AChR function is not altered by methylation inhibitors and that changes in AChR-mediated contraction are not due to inhibition of MT activities.

Acetylcholine↗
PubMed1984

Redistribution of acetylcholine receptors on developing rat myotubes.

The mechanism of formation of acetylcholine receptor (AChR) clusters at developing mammalian endplates was investigated in vitro, using intercostal muscles from embryonic rats. The muscles were explanted in organ culture with the spinal cord attached, as described previously (Ziskind-Conhaim, L., and M. J. Dennis (1981) Dev. Biol. 85: 243-251). AChRs on the myofibers were labeled with [125I]-alpha-bungarotoxin shortly before clusters appeared and subsequently were cultured in unlabeled toxin for 1 day. Autoradiography of the cultured fibers demonstrated the presence of labeled clusters of AChRs indicating that the AChRs in the newly formed clusters arise from AChRs that had previously been uniformly distributed on the muscle surface.

Animals↗
PubMed1983

Developmental regulation of 16S acetylcholinesterase and acetylcholine receptors in a mouse muscle cell line.

We have studied the appearance, distribution and regulation of acetylcholinesterase (AChE) and acetylcholine receptors (AChRs) in a mouse skeletal muscle cell line (C2), that was originally isolated and described by Yaffe & Saxel [54]. In culture, cells from this line form spontaneously contracting myotubes, with overshooting action potentials that are TTX-sensitive. After fusion of myoblasts into myotubes, there was a dramatic increase in the amount of both AChE and AChR. Three forms of AChE, distinguished by their sedimentation on sucrose gradients, were synthesized: 4-6S, 10S, and 16S. The 4-6S and 10S forms appeared 1 day after the cells began to fuse, whereas the 16S form appeared only 2 days after fusion began. Maximal levels of the 16S AChE form (25-30% of the total) were obtained by reducing the concentration of horse serum in the fusion medium. Prevention of myoblast fusion by reducing the calcium levels in the medium decreased the total AChE by 70%, and only the 4-6S form was synthesized. Blocking spontaneous contractile activity of the myotubes by tetrodotoxin (TTX) led to a 50% reduction in all three esterase forms. Thus, the 16S, or endplate form of AChE is not specifically regulated by electrical or contractile activity in the C2 cell line. After fusion the number of AChRs increased rapidly for 3-4 days and then stabilized. Receptor clusters, ranging from 10-30 micron in length, appeared 1 day after myoblast fusion began. When cells were grown in medium containing reduced Ca2+, the total number of AChRs was decreased by 20-50%. Reduction of Ca2+ after myotubes and AChR clusters had formed resulted in dispersal of AChR clusters. Inhibition of muscle contractions with TTX did not affect the number of AChRs or their distribution.

Acetylcholinesterase↗