PubMed Health⌕ Search

Biomedical subjects

A A Butov

Publications and source records attributed to A A Butov.

5 recordsLinked to original sources
PubMed2003

[Problems in using methods of analyzing gene expression in studying the aging process].

Aging processes are now actively investigated on the base of analysis of changes in gene expression. Many of the standard methods (such as hierarchic clustering, method of K-means, SOM (Self-organizing maps), Gene Shaving, etc.) do not take into account the specifics of time sets. In the article the new approach of the analysis and clustering of genes based on the processing of time increments in their expressions is presented. Genes in the resulting groups behave concertedly with any chosen "pilot" gene or simply together. The methods of clustering were tested on the data of gene expressions of C. elegans in aging. In the article the specific claims of believability of the experiments are discussed.

Aging↗
PubMed2002

[Problems of the existence of "optimal" function survival functions in experiments of varying protein supplies to Mediterranean fruit flies].

The paper is devoted to the discussion of the possibility of analyzing the changes in survival curves of Mediterranean Fruit Flies under different levels of reproduction by means of solving the optimization problem with some objective function. The investigation is carried out on the base of mathematical model with approximations resulting in the analysis of joint changes in survival functions and reproduction in flies subjected to different conditions of protein availability in food. The model describes possible mechanisms of evolutionary selection from the point of view of trade-off in average life span and reproduction.

Animals↗
PubMed2001

Have the oldest old adults ever been frail in the past? A hypothesis that explains modern trends in survival.

Three important results concerning the shape and the trends of the human mortality rate were discussed recently in demographic and epidemiological literature. These are the deceleration of the mortality rate at old ages, the tendency to rectangularization of the survival curve, and the decline of the old age mortality observed in the second part of the 20th century. In this paper we show that all these results can be explained by using a model with a new type of heterogeneity associated with individual differences in adaptive capacity. We first illustrate the idea of such a model by considering survival in a mixture of two subpopulations of individuals (called "labile" and "stable"). These subpopulations are characterized by different Gompertz mortality patterns, such that their mortality rates cross over. The survival chances of individuals in these subpopulations have different sensitivities to changes in environmental conditions. Then we develop a more comprehensive model in which the mortality rate is related to the adaptive capacity of an organism. We show that the trends in survival patterns experienced by a mixture of such individuals resemble those obtained in an analysis of empirical data on survival in developed countries. Lastly, we present evidence of the existence of subpopulations of phenotypes in both humans and experimental organisms, which were used as prototypes in our models. The existence of such phenotypes provides the possibility that at least part of today's centenarians originated from an initially frail part of the cohort.

Adolescent↗
PubMed2001

[Mathematical and simulating model of accelerated aging induced by 5-bromo-2-deoxyuridine].

The principles of stochastic modeling and simulation of the processes of aging and carcinogenesis by means of semimartingale methods are considered. The model fits to the experiments on activating of processes of aging be 5-bromodeoxiuridine postnatal exposure inducing genome instability. The model describes the multistage phenomena of aging and carcinogenesis by the system of stochastic equations in terms of multivariate and diffusion processes.

Aging↗