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C Pinset

Publications and source records attributed to C Pinset.

47 records · Page 3Linked to original sources
PubMed1988

Control of myogenesis in the mouse myogenic C2 cell line by medium composition and by insulin: characterization of permissive and inducible C2 myoblasts.

Using subcloning and manipulations of culture conditions we have isolated from the mouse myogenic cell line C2 a variant cell line that we named inducible. Unlike the progenitor cells that are referred to as permissive, inducible myoblasts differentiate poorly in Dulbecco modified Eagle medium plus fetal calf serum (FCS) and require the presence of insulin at a high concentration (1.6 10(-6) M) or insulin-like growth factor I (IGFI) at a lower concentration (2.5 10(-8) M) to differentiate. Permissive and inducible myoblasts fail to differentiate when grown in MCDB202 medium plus 20% FCS, even after a prolonged arrest in G1 phase. This shows that an arrest in G1 is in itself insufficient to trigger terminal differentiation. Both cell types also exhibit distinct patterns of accumulation of muscle mRNAs corresponding to sarcomeric actins and myosin light chain MLC1A. The possibility that these two cell lines might represent two different stages of the progression of myoblasts toward terminal differentiation is discussed.

Actins↗
PubMed1987

Developmental pattern of mouse skeletal myosin heavy chain gene transcripts in vivo and in vitro.

We have studied the transcripts of the embryonic, perinatal, and adult fast myosin heavy chain (MHC) genes in mouse skeletal muscle in vivo before and after birth, and in vitro in myogenic cell lines. In vivo, in 15-day fetal muscle, embryonic and perinatal MHC mRNAs are both present, and the former is the major transcript. By 18 days the perinatal is predominant and the adult MHC mRNA appears. In beta-bungarotoxin-treated fetuses, a similar developmental pattern is detected, suggesting that it is nerve-independent and that primary myotubes alone undergo the same developmental changes. In vitro, in the absence of the nerve, embryonic, perinatal, and adult IIB MHC mRNAs accumulate. The level of the latter two isomRNAs is influenced by culture conditions.

Aging↗
PubMed1987

Proto-oncogenes.

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Animals↗
PubMed1987

Calcium-dependent effect of the thymic polypeptide thymopoietin on the desensitization of the nicotinic acetylcholine receptor.

The effects of the thymic polypeptide thymopoietin (Tpo) on the properties of the nicotinic acetylcholine receptor (AcChoR) were investigated by patch clamp techniques on mouse C2 myotubes and by biochemical assays on AcChoR-rich membrane fragments purified from the Torpedo marmorata electric organ. At high concentrations (greater than 100 nM), Tpo inhibits the binding of cholinergic agonists to the AcChoR in a Ca2+-insensitive manner. At lower concentrations (2 nM), Tpo applied on C2 myotubes simultaneously with nondesensitizing concentrations of acetylcholine results in the appearance of long closed times separating groups of openings. This effect depends on the presence of Ca2+ in the external medium. Outside-out recordings, performed with various concentrations of EGTA in the intracellular medium, suggest that Ca2+ acts on the cytoplasmic face of the membrane after entry through acetylcholine-activated channels. Parallel studies with T. marmorata AcChoR-rich membranes show that in the presence of Ca2+ Tpo causes a decrease in the apparent equilibrium dissociation constant of the noncompetitive blocker [3H]phencyclidine, enhances, at low concentrations, the binding of [3H]acetylcholine, and also alters the binding kinetics of the fluorescent agonist 6-(5-dimethylamino-1-naphthalenesulfonamido)-n-hexanoic acid beta-(N-trimethylammonium bromide) ethyl ester to the AcChoR. It was concluded that, in the presence of Ca2+, Tpo displaces the conformational equilibrium of the AcChoR towards a high-affinity desensitized state and increases the transition rate towards the same state.

Acetylcholine↗
PubMed1986

Effects of chlorpromazine and phencyclidine on mouse C2 acetylcholine receptor kinetics.

Patch-clamp techniques were used to record acetylcholine- (ACh) activated single-channel currents in cell-attached membrane patches from myotubes of the mouse cell line, C2. The effects of the phenothiazine derivative chlorpromazine (CPZ) and of the hallucinogen phencyclidine (PCP) on ACh-activated single-channel properties were studied under conditions where both compounds are positively charged (pH 7.2). The single-channel conductance was unaffected by either CPZ or PCP at concentrations ranging from 10 to 500 nM. 10-200 nM-CPZ and PCP led to shortened mean burst times. CPZ and PCP effects on mean burst times were voltage independent and did not vary in a simple linear manner with concentration. 10-200 nM-CPZ and PCP did not reduce channel opening frequencies, suggesting that the fraction of non-conducting state (occupied, blocked or desensitized) favoured at equilibrium was not significant at these concentrations. On the other hand, concentrations of CPZ and PCP higher than 300 nM did lead to depressed channel opening frequencies. In addition, we observed that, at these concentrations, the shortened burst duration reverses to the longer values found at lower effector concentrations. The effects of CPZ and PCP on ACh-activated single-channel kinetics are interpreted in terms of current models of ACh-receptor structure and conformational transitions.

Acetylcholine↗
PubMed1985

Induction of myogenic differentiation in serum-free medium does not require DNA synthesis.

Cells of the myogenic rat cell line L6 can be obtained as a confluent, quiescent population of undifferentiated myoblasts after growth in F12 medium supplemented with fetal calf serum. Myogenic differentiation can be induced in these cells by changing to Dulbecco's modified Eagle's (DME) medium containing insulin as the only protein component. Labeling of the cells with [3H]thymidine demonstrates that this induction of fusion occurs in the absence of DNA synthesis in about 85% of the cells. This result was confirmed using cytosine arabinoside: fusion of quiescent L6 cells was induced in the presence of this inhibitor of DNA synthesis. The myotubes formed in DME + insulin medium, with or without cytosine arabinoside, synthesize or accumulate proteins characteristic of differentiated muscle cells including myosin heavy and light chains, alpha-actin, alpha- and beta-tropomyosins, and the acetylcholine receptor. These experiments represent a direct demonstration that DNA synthesis is not required for the induction of myogenic differentiation in undifferentiated quiescent cells.

Animals↗
PubMed1984

Manipulation of medium conditions and differentiation in the rat myogenic cell line L6.

Myoblasts of the L6 rat cell line were grown in Ham's F12 nutrient medium containing 10% fetal calf serum (F12 + FCS). Although the cells were confluent by 6 days in culture, fusion was not observed even if cultures were maintained for 10-14 days. At least 80% of the cells in such confluent unfused cultures were in the G1 phase of the cell cycle and less than 5% of the cells in confluent cultures synthesized DNA during a 4-day period. The synthesis of muscle-specific proteins (alpha-actin, beta-tropomyosin, and myosin light chains LC1emb and LC2F) was negligible when compared to fused cultures of L6 cells grown for a similar time in Dulbecco's medium with 10% FCS (DME + FCS). When the unfused cultures were shifted from F12 + FCS to DME + FCS, DNA synthesis could be demonstrated in more than 95% of the cells and fusion occurred, indicating that neither proliferative nor myogenic capacity had been irreversibly lost. Raising the levels of calcium, varying the serum concentration from 0 to 20%, or the addition of medium components (present in DME but reduced or absent in F12) all failed to induce fusion in the L6 cells grown in F12. However, L6 cells will fuse in mixtures of F12 + FCS and DME + FCS. Fusion will also occur if L6 cells are grown at clonal density in F12 + FCS supplemented with calcium. While it has not been possible to determine why F12 + FCS is nonpermissive for L6 cells in confluent mass cultures, the results demonstrate that prolonged residence in the G1 phase of the cell cycle is not a sufficient condition for L6 myoblast differentiation to occur.

Animals↗
PubMed1982

[Proliferation and differentiation of a myogenic line in synthetic media].

When plated in plastic culture dishes, muscle cells of the L6 cell line are unable to proliferate or to differentiate in a synthetic medium composed of Dulbecco's Minimal Essential medium (DME), bovine fetuin (1 mg/ml) and bovine insulin (10 micrograms/ml). In contrast, these cells will proliferate and differentiate morphologically and biochemically in this medium if the culture dishes have been previously treated with DME containing fetal Calf serum. Pretreatment of dishes does not increase cell attachment in synthetic medium but seems to act as a factor increasing cell viability.

Animals↗
PubMed1978

Leucocyte-migration-inhibition test in patients with colorectal cancer: clinicopathological correlations.

Leucocyte-migration-inhibition test was used to study the immune reactions of leucocytes from 136 colorectal cancer patients, 43 patients with non-cancerous chronic colorectal diseases and 82 controls, with saline extracts of HT29 line. A positive inhibition was found in only 43% of colorectal cancer patients. It was higher in carcinomas of limited extension than in invasive ones (64% against 39%). Furthermore, operation by itself had a depressive effect on the reaction, as the positivity in 25 patients tested twice was 64% before operation and 32% after. Leucocytes from patients with non-cancerous chronic colorectal diseases gave many positive reactions (65%). The percentage of positivity was about the same for diseases with high, low or no risk of cancerization. Hence the antigen(s) of tumour extracts that react with patient's leucocytes are, at least partially, unrelated to cancer.

Cell Migration Inhibition↗
PubMedDate not supplied

Transplantation of adult-derived myoblasts in mice following gene transfer.

We have explored the use of myoblasts obtained from adult animals as a target for somatic gene therapy. Myoblasts from an adult beta-glucuronidase deficient (MPS VII) mouse were isolated and infected with a retroviral vector carrying the human beta-glucuronidase cDNA. Beta-glucuronidase was used as a reporter gene to follow the fate of genetically-modified myoblasts after transplantation into the tibialis anterior of MPS VII recipients. When experimental necrosis had been induced in the recipient muscle prior to cell injection, histological analysis demonstrated efficient engraftment of adult derived myoblasts following gene transfer. The reconstituted myofibres expressed the transgene for at least 10 weeks following transplantation.

Animals↗