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D Montarras

Publications and source records attributed to D Montarras.

49 records · Page 3Linked to original sources
PubMed1984

Changes in ganglioside metabolism during in vitro differentiation of quail embryo myoblasts.

The metabolism of gangliosides was studied during the in vitro differentiation of both normal quail myoblasts and myoblasts which have been transformed by a temperature-sensitive mutant of Rous sarcoma virus (RSV). These transformed cells can be maintained undifferentiated if incubated at 35 degrees C, but they will differentiate when shifted to 41 degrees C. (D. Montarras and M. Y. Fiszman (1983) J. Biol. Chem. 258, 3882-3888). The analysis of [14C]Glucosamine-labeled gangliosides by two-dimensional thin-layer chromatography reveals variations in the metabolism of the gangliosides during the process of differentiation. During the formation of myotubes, it was observed that the accumulation of GD1a is reduced, while the accumulation of GD3 is increased. Therefore, this results in the variation of the ratio GD3/GD1a which increases from 1.8 to 25 in the case of clones of transformed myoblasts, and from 0.5 to 1.7 in the case of uninfected myoblasts. These variations which have been observed seem to be specific of the myogenic differentiation since they cannot be reproduced when differentiation is inhibited by BUdR treatment or when fibroblasts reach confluency and are blocked in the G1 phase of cell cycle. Furthermore, the transformed myoblasts in vitro are shown to be a good model system since their gangliosides composition is very similar to that of muscle cells in vivo.

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PubMed1983

A new muscle phenotype is expressed by subcultured quail myoblasts isolated from future fast and slow muscles.

Differentiation of quail myoblasts, isolated from thigh pectoralis and anterior latissimus dorsi muscle, was analyzed in primary cultures and in cultures obtained following repeated subculturing. Our study shows that quail myoblasts can survive many generations without losing their ability to form myotubes. However, during these subcultures the cells progressively express a new phenotype. This phenotype is characterized by a mixture of myosin light chains such that LC1F, LC2F, and LC2S are present in roughly equimolar amounts, each accounting for 25 to 30% of the total light chain synthesis while LC1S accounts for the remaining 10 to 15%, and by a mixture of fast and slow alpha tropomyosin in which alpha S accounts for 10 to 15% of the alpha subunits synthesis. Clonal analysis indicates that all cells in the population express this phenotype which is also characteristic of subcultures obtained from both future fast and slow muscles. Relationships between this phenotype and muscle development are discussed.

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PubMed1983

Fast and slow chicken skeletal muscles contain different alpha and beta tropomyosins.

Avian tropomyosin has been purified from fast skeletal muscles (breast muscle and posterior latissimus dorsi : PLD) and from a slow skeletal muscle (anterior latissimus dorsi : ALD) and the alpha and beta subunits have been further separated using preparative gel electrophoresis. These subunits have been subjected to partial proteolysis using different proteolytic enzymes. In this communication we show that this procedure allows to distinguish not only between fast and slow alpha tropomyosin but also between fast and slow beta tropomyosin. Furthermore we have raised an antiserum against the fast alpha tropomyosin and we present evidence to show that this antiserum does not cross-react with the slow alpha tropomyosin. These results are taken to indicate that all these tropomyosin subunits represent different gene products.

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PubMed1983

[A thermosensitive characteristic of the Schmidt Rupin strain of Rous sarcoma virus affecting the longevity of infected lines].

Quail embryo skin fibroblasts infected with wild type Rous sarcoma virus SR-RSV grow, at 36 or 41 degrees C, twice as fast (30 hours. mean division time) as the uninfected controls or the cells infected with RAV-1 virus. At 36 degrees C the SR-RSV infected cells stop growing after the same delay as the controls, thus having undergone twice as many doublings, (38 to 40 instead 18 to 20). However, at 41 degrees C, SR-RSV infected cells stop 5 to 6 divisions earlier. This cannot be reversed by shifting the cultures to 36 degrees C. Rising to 41 degrees C those cultures which grew previously at 36 degrees C reduce the number of residual divisions. No such effect is observed with NYts68 or PA101 viruses which display a reduced level of pp60v-src activity at 41 degrees C.

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PubMed1982

Changes in tropomyosin during development of chick embryonic skeletal muscles in vivo and during differentiation of chick muscle cells in vitro.

We have studied the changes in tropomyosin subunits and their pattern of phosphorylation during embryonic development and also during in vitro differentiation of cultured muscle cells. We have found that in 10-day-old embryos tropomyosin consists of 75% beta subunit and 25% alpha subunit. However, only 60% of the beta subunit is phosphorylated while the alpha subunit is almost exclusively present in its phosphorylated form. During subsequent development, the amount of alpha-tropomyosin increases so that by hatching it represents 50% of the total subunits. During the same time, the amount of phosphorylated variants for both the alpha and the beta subunits decreases so that after hatching they represent less than 20% of each subunit. In cultures of differentiating myoblasts, the alpha subunit is synthesized before the beta subunit, and within each subunit, the unphosphorylated variants are the first to be synthesized. The reason for this discrepancy is not known at the present time.

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PubMed1981

Characterization of the tropomyosin present in various chick embryo muscle types and in muscle cells differentiated in vitro.

Tropomyosin, present in various types of chick embryo muscle, has been characterized by two-dimensional gel electrophoresis. In skeletal muscle, it was found that both the alpha and beta subunits exist as two variants, alpha 1, alpha 2 and beta 1, beta 2. The most acidic variants (alpha 2 and beta 2) could be demonstrated to be phosphorylated and, based upon the facts that 1) after phosphatase treatment alpha 2 and beta 2 co-migrate with alpha 1 and beta 1 and 2) in vitro translation of skeletal muscle mRNA produces only alpha 1 and beta 1, we suggest that alpha 2 and beta 2 merely represent the phosphorylated forms of alpha 1 and beta 1. A similar situation is found in differentiated muscle cultures in vitro. In cardiac muscle or in cardiocytes, in culture, the only subunit of tropomyosin which is present (the alpha subunit) is also phosphorylated. However, in smooth muscle, none of the tropomyosin subunits is phosphorylated. The use of various modifications in the second dimension of two-dimensional gel electrophoresis has allowed us to separate completely the alpha subunits of slow and fast muscle tropomyosin and to show that: 1) the cardiac alpha subunit is distinct from either the slow alpha or the fast alpha subunit and 2) in vitro differentiated cells synthesize a tropomyosin which, by co-migration under various conditions, is identical with fast muscle tropomyosin.

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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.

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PubMedDate not supplied

Potential phasic and tonic muscles express a common set of fast and slow myosin light chains and fast tropomyosin during early development of chick embryo.

We investigated the expression of myosin light chains and tropomyosin subunits during chick embryonic development of the anterior (ALD) and posterior (PLD) parts of the latissimus dorsi muscles. As early as day 8 in ovo, both muscles accumulate a common set of myosin light chains (LC) in similar ratios (LC1F: 55 per cent; LC2S: 25 per cent; LC2F: 12 per cent; LC1S: 8 per cent) and a common set of tropomyosin (TM) subunits (beta 2, beta 1, alpha 2F). Later during development, the slow components of the LC regularly disappear in the PLD and the fast components of the LC and the alpha 2FTM disappear in the ALD, so that the adult pattern is almost established at the time of hatching. Thus, early in development, the two muscles accumulate a common set of fast and slow myosin light chains and fast tropomyosin and some isoforms are repressed at a later stage during development. These data might suggest that during development, the regulatory mechanisms of muscle specific isoform expression differ from one contractile protein to another.

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