Fractal characterisation of boundary irregularity in skin pigmented lesions

A growing literature shows researcher's interest in fractal analysis, arising from its ability to describe and characterise quantitatively the complexity of several tumour profiles. The aim of the work was to investigate the fractal properties of skin pigmented lesion boundaries. Although melanoma is one of the most aggressive tumours, early detection and a high rate of diagnostic accuracy, followed by timely excision, can allow complete recovery in melanoma patients. A modified approach to fractal dimension estimation was performed that was able to consider, in a data fit procedure, the range in which lesions show fractal properties. Identification of this zone is the most important step towards a correct fractal analysis procedure. The method was checked against a known fractal dimension object (Koch's curve) with an error of 0.007. The fractal dimension was estimated in 110 skin pigmented lesions and showed a significantly increasing linear regression (p < 0.05), from common naevi to naevi with dysplasia to melanomas. This result is important for screening, as it can inform the decision to excise precociously malignant lesions or to avoid unnecessary removal of benign ones. The limitations of the method are discussed.

Use of mathematical models of survivorship in the study of biomarkers of aging: the role of heterogeneity

An ever increasing number of people have been engaging in aging research using various interventions aimed to modify aging processes, and/or life span, of experimental animals. Since this type of studies needs outcome parameters for assessing the efficacy of such interventions, research on biomarkers of aging (ABs) has received new stimuli. In the present paper, the problem of the occurrence of a vicious circle any time we study ABs and determinants of aging is addressed. In fact, while ABs would represent the standard reference to be used in the study of the main causes of processes of aging, these very determinants should already be known in order to get reliable ABs. A feasible way to overcome this impasse is proposed, using mathematical models of survivorship or mortality based on biological hypotheses and accounting for inter-individual heterogeneity, a necessary ingredient for a correct interpretation of survival results. Specific kinetics of experimental parameters that are candidates as ABs can be compared to the kinetics hypothesized for general biological functions entering the model. We have built a model of this type that can also be used to perform a reliable overall gross estimate of the rate of aging, R(a), in the population, a parameter useful when judging the success of interventions aimed to act on determinants of aging. The perspective that theory of complex systems can be of help in the search for ABs is also discussed.

Long-live euthymic BALB/c-nu mice. I. Survival study suggests body weight as a life span predictor

This paper is the first of a series aimed to show the main physiological and pathological characteristics of male euthymic BALB/c-nu mice, a long-live strain of BALB/c mice bred in our own Institute. In particular, the first two paired papers are respectively devoted to general survival information and disease characteristics, also taking into account very old animals that are of high interest for studies on successful aging. In this paper we report the analysis of survival kinetics, the time course of body weight and the correlation between body weight and time-at-death. The longitudinal study has been performed on 88 male mice, checking individually their body weight and date of death and analyzing survival data by a model built by our own. Survival analysis shows quite higher longevity (median age: about 29 months) in this population when compared with other BALB/c strains. The most relevant finding on body weight is its correlation with longevity until the age of 22 months: thinner subjects live longer and lose weight at a lower rate than their heavier mates. Results have formed the basis on which to plan the cross-sectional experiment to study pathologies and biological parameters at different ages, including a group of mice at very advanced ages (34 months).

Long-live euthymic BALB/c-nu mice. II: spontaneous tumors and other pathologies

This paper is the second of a series aimed to show the main physiological and pathological characteristics of male euthymic BALB/c-nu mice, a long-live strain of BALB/c mice bred in our own Institute. The previous paired paper Piantanelli (Mech. Ageing Dev. (2001)) has been devoted to a survival study up to advanced ages highly interesting for studies on successful aging. In the present paper we report first data of a cross-sectional study on 4,15,22,28 and 34 months-old mice, dealing with tumors and other relevant pathologies. Results have shown that tumors or other pathologies can hardly be detected up to the age of 22 months. At 34 months of age about 40% of mice revealed a variety of neoplasia and other diseases are clearly detectable. These results suggest that a significant increase in longevity could be a factor increasing the risk of tumor development; thus, caution has to be paid in studies on mice utilized for long term carcinogenicity assay, where animals are sacrificed at the age of 18 months, according to the International Program. Finally, animals of the same chronological age have been subdivided in clusters according to their presumptive longevity, estimated taking advantage of the relationship between body weight and age-at-death found in the paired longitudinal study. This subdivision will be helpful in interpreting inter-individual variability of the biological parameters checked in these animals.