The increased incidence of malignant melanoma in obese individuals is due to impaired melanogenesis and melanocyte DNA repair.

Obese individuals have a higher incidence of malignant melanoma (MM). We here suggest that the higher incidence is caused by a reduction of melanogenesis and a decreased capacity of melanocytes DNA repair. These effects are caused by an increase in the haematic levels of melanocyte stimulating hormone (MSH) antagonists, namely of the protein attractin, the melanocyte concentrating hormone (MCH), the agouti related protein (ASRP) and perhaps also agouti protein (ASIP), determining a lower activity of circulating MSH and of melanocortotropin receptors (MCRs) 1 and 4.

Synthetic aromatic compounds interfering with melanogenesis are responsible of the rising trend of malignant melanoma incidence.

The hypotheses is forwarded that the introduction in the environment of high concentrations of phenols and other aromatic compounds (AC) is one, perhaps the main cause of the continuously rising trend of malignant melanoma (MM) incidence. Two, non-mutually exclusive, possibilities could explain how AC may induce MM: (1) AC may act as inhibitors or alternative substrates of tyrosinase, the enzyme synthesizing melanin, thus impairing the melanocyte photoprotection. (2) AC may impair, directly or indirectly, the activity or synthesis of the melanocorticotropin receptor (MC1R), which photoprotects melanocytes from the UV rays (UVR) by stimulating the DNA repair system.

Mosaicism may explain the evolution of social characters in haplodiploid Hymenoptera with female workers.

The role of haplodiploidy in the evolution of eusocial insects and why in Hymenoptera males do not perform any work is presently unknown. We show here that within-colony conflict caused by the coexistence of individuals of the same caste expressing the same character in different ways can be fundamental in the evolution of social characters in species that have already reached the eusocial condition. Mosaic colonies, composed by individuals expressing either the wild-type or a mutant phenotype, inevitably occurs during the evolution of advantageous social traits in insects.

The main product of specialized tissues regulates cell life and may cause neoplastic transformation.

Many tissues and cells in vertebrates are highly specialized and devoted to a single function through the action of a single molecule, that we call the "main product" (MP) of the cell. The hypothesis here proposed is that these MPs control all aspects of the cell life, namely activity, division, differentiation and apoptosis. Evidences supporting this hypothesis are reported for the immune system, pancreatic beta-cells, melanocytes, connective tissues, thyroid cells, skin and erythroid cells.

The exceptionally high rate of spontaneous mutations in the polymerase delta proofreading exonuclease-deficient Saccharomyces cerevisiae strain starved for adenine.

Background: Mutagenesis induced in the yeast Saccharomyces cerevisiae by starvation for nutrilites is a well-documented phenomenon of an unknown mechanism. We have previously shown that the polymerase delta proofreading activity controls spontaneous mutagenesis in cells starved for histidine. To obtain further information, we compared the effect of adenine starvation on mutagenesis in wild-type cells and, in cells lacking the proofreading activity of polymerase delta (phenotype Exo-, mutation pol3-01).

The influence of colonial organization on thermotolerance and thermoresistance in Saccharomyces cerevisiae.

In this study we show that thermotolerance and thermoresistance of the yeast Saccharomyces cerevisae is enhanced when cells are in colonial condition. We also describe a method to select stable thermoresistant mutants which produce colonies from single plated cells at a temperature 2.5 degrees C higher than the maximum growth temperature of their parental strain.