RESUMO
In recent decades, male infertility has been correlated with the shortening of sperm telomeres. Telomeres regulate the reproductive lifespan by mediating the synapsis and homologous recombination of chromosomes during gametogenesis. They are composed of thousands of hexanucleotide DNA repeats (TTAGGG) that are coupled to specialized shelterin complex proteins and non-coding RNAs. Telomerase activity in male germ cells ensures that the telomere length is maintained at maximum levels during spermatogenesis, despite telomere shortening due to DNA replication or other genotoxic factors such as environmental pollutants. An emerging body of evidence has associated an exposure to pollutants with male infertility. Although telomeric DNA may be one of the important targets of environmental pollutants, only a few authors have considered it as a conventional parameter for sperm function. The aim of this review is to provide comprehensive and up-to-date data on the research carried out so far on the structure/function of telomeres in spermatogenesis and the influence of environmental pollutants on their functionality. The link between pollutant-induced oxidative stress and telomere length in germ cells is discussed.
Assuntos
Infertilidade Masculina , Sementes , Masculino , Humanos , Telômero/genética , Células Germinativas/metabolismo , EspermatozoidesRESUMO
Until the middle of the 20th century, embryogenesis patterns were considered as based on a rigid, unidirectional ontogenetic development, whose nuclear programming yields an irreversibility feature for cellular determination. Further empirical pieces of evidence have provided new insights about a certain reversibility to cellular determination, finding new biomolecular mechanisms (nuclear reprogramming, dedifferentiation, transdifferentiation) which have clearly shown that such a reversibility exists, warranting a certain cellular plasticity inside cell cycle; moreover, they seem mainly ruled by epigenetic factors. In this framework, evolution can be viewed as a systemic transformation of the spatiotemporal epigenetic organization, and the maintenance of the stable final adult stage includes a possibility of dedifferentiation at the particular points of ontogenetic development leading to the achievement of the final stage though the alternate sets of epigenetic trajectories. This paper is aimed to briefly outline historically the main aspects which have led to define the mechanisms of cellular plasticity, highlighting the chief empirical facts supporting it and the related still unresolved problematic issues.
Assuntos
Reprogramação Celular , Epigênese Genética , Diferenciação Celular/genética , Transdiferenciação Celular , Reprogramação Celular/genética , EpigenômicaRESUMO
The contribution of Étienne Geoffroy Saint-Hilaire (1772-1844) to evolutionary biology is reviewed in commemoration of his 250th birthday. Geoffroy's views on saltational changes during embryogenesis of animals characterize him as a predecessor of the epigenetic concept of evolution, which is now developing in the frames of the extended evolutionary synthesis or evo-devo. While Lamarck distinguished between the two modes of evolution, one within the same level of organization and the other characterized by the transition to a more complex organization, Geoffroy Saint-Hilaire attempted to explain the second mode by the changes in embryogenesis triggered by environmental influences. In this regard, he placed the phenomenon of complexification in the centre of the evolutionary context. Geoffroy Saint-Hilaire can be considered also as an early predecessor of the cell theory. His ideas about the unique plan of structure for animal species and of the fundamental connections that establish the homology of anatomical parts represent an important contribution to the evolutionary concept.
Assuntos
Anatomia Comparada/história , Evolução Biológica , Epigênese Genética , História do Século XVIII , História do Século XIX , Humanos , MasculinoRESUMO
The celebrated 1917 work "On Growth and Form" of D'Arcy W. Thompson has established a landmark for mathematical biology, introducing new perspectives of study and research in biology, providing mathematical methods to morphology of biological systems. In this brief historical essay, we recall the novelties and relevance of the work from a retrospective stance, above all pointing out the crucial role played by it in the dawning of epigenetic standpoint. The role of underlying epigenetic processes in generation of biological forms via similarity transformations is analyzed within the framework of D'Arcy Thompson. The significance of D'Arcy Thompson as a predecessor of the relational biology and of the epigenetic concepts of evolution is discussed.
Assuntos
Adaptação Fisiológica/genética , Algoritmos , Evolução Biológica , Epigênese Genética/genética , Epigenômica/métodos , Modelos Teóricos , Animais , Biologia do Desenvolvimento/métodos , Humanos , Matemática , Morfogênese/genética , Estudos RetrospectivosRESUMO
Considering biosphere as a closed thermodynamical system, inside it, biological organisms may be considered as open thermodynamical systems exchanging energy and matter with ecosystem. Making appeal to non-equilibrium thermodynamics, anthropology, biology, sociology and cliodynamics, we discuss, from an interdisciplinary stance, some main moments of human evolution from either the phylogenetic and the ontogenetic standpoint, highlighting the crucial bifurcation which saw the rising of the modern societies with respect to primitive ones.