The effects of N-ras oncogene expression on PDGF-BB stimulated responses in cultured mouse myoblasts.

The role of the ras oncogene in the signalling pathway triggered by platelet-derived growth factor BB (PDGF-BB) has been investigated in a cell line which normally differentiates into myotubes. Following the activation of the N-ras oncogene, however, the cells proliferate and form foci. PDGF-BB stimulated the phosphorylation of tyrosine in several cellular proteins of molecular weight 185, 160, 94, 54, 44, 42 kDa and furthermore Ca2+ was released from internal stores. Activation of the N-ras gene by treatment of cells with dexamethasone (DEX) inhibited these responses to PDGF-BB. On the other hand, both ras-induced and -non induced cells responded to bradykinin (BK), foetal calf serum (FCS) and ionomycin (ION) by releasing Ca2+ from intracellular stores. The inhibition of the response to PDGF-BB in ras-activated cells has been further investigated. The binding of [125I]-PDGF-BB to its receptors was low and western blotting showed a low level of PDGF-BB receptor protein. This was in marked contrast to the receptor number seen in cells grown in growth medium or fusion promoting medium. These results indicate that cells transformed with the N-ras oncogene fail to respond to platelet-derived growth factor and exhibit a very low level of PDGF receptors. This suggests a role for the ras oncogene in the earliest steps of the signalling pathway.

Testing Wound-healing Activity in T15 Fibroblast Cultures: A Morphometric Analysis.

The purpose was to evaluate the use of mouse T15 fibroblast cell cultures for the investigation of wound-healing activity. In order to investigate their mechanisms of action, the effects of drugs with wound-healing activities were compared by using morphometric analyses by microscopy after cell staining. A number of parameters were used to evaluate the effects of titrated extracts from Centella asiatica and dexpanthenol (drugs that have been used in medical practice for their wound-healing activities) on cultured mouse T15 fibroblasts. These parameters were : the total number of cells ; the number of T15 cells in mitosis ; the percentages of fusiform, polygonal, round and vacuole-containing cells ; and the number of intracellular collagen granules. The results indicate that these two drugs exhibit wound-healing activities by activating fibroblast cells, and have cytoprotective effects, although their mechanisms of action on mouse T15 fibroblasts were different. On the basis of our findings, mouse T15 fibroblast cell cultures seem to be useful for the pharmacological screening of compounds with wound-healing activity.

Determination of genotoxic, antigenotoxic and cytotoxic potential of the extract from lichen Cetraria aculeata (Schreb.) Fr. in vitro.

Naturally occurring compounds can have protective effects towards mutagens and carcinogens as shown by numerous studies. In the present study, the genotoxic/antigenotoxic activities of the extract from lichen Cetraria aculeata (Schreb.) Fr., which has been identified as an antibacterial agent in former studies, were investigated against known mutagens such as 4-nitro-o-phenylenediamine (4-NPD) and 2-aminofluorene (2-AF) in TA98 and TA100 strains of Salmonella typhimurium in the presence or absence of metabolic activity. Further genotoxicity/antigenotoxicity of the extract against mitomycin C for micronucleus formation was also evaluated in human lymphocytes. The cytotoxic effects of the extract on mammalian cells were investigated in three different cell line types by MTT assay. The results obtained show that the extract of C. aculeata has a significant antigenotoxic activity in bacterial systems, but not in mammalian cells and cytotoxic activity in some mammalian cancer cells. However, it was not mutagenic in all systems. The findings suggest that the lichen extract may have a possible therapeutic potential and therefore this must be further investigated by other multiple in vitro bioassays for the development of therapeutic agents.

Inhibition of DNA synthesis by carvacrol in mouse myoblast cells bearing a human N-RAS oncogene.

Monoterpenes are dietary components found in the essential oils of a wide variety of plants. A number of these monoterpenes have antitumor activity. We have investigated the effects of carvacrol obtained by fractional distillation of Origanum onites L. essential oil, on DNA synthesis of N-ras transformed myoblast cells, CO25. Incubation of the cells with different doses of carvacrol prevented DNA synthesis in the growth medium and ras-activating medium, which contains dexamethasone. This result demonstrates that carvacrol inhibits growth of myoblast cells even after activation of mutated N-ras oncogene, suggesting the possibility that carvacrol may find application in cancer therapy.