Biomedical subjects

J Chela-Flores

Publications and source records attributed to J Chela-Flores.

7 recordsLinked to original sources

PubMed1992

Towards the molecular bases of polymerase dynamics.

One aspect of the strong relationship that is known to exist between the processes of DNA replication and transcription is manifest in the coupling of the rates of movement of the replication fork (rf) and RNA polymerase (rt). We address two issues concerning the largely unexplored area of polymerase dynamics: (i) The validity of an approximate kinematic formula linking rf and rt suggested by experiments in which transcription is inhibited in some prokaryotes with the antibiotic streptolydigin, and (ii) What are the molecular bases of the kinematic formula? An analysis of the available data suggests possible molecular bases for polymerase dynamics. In particular, we are led to a hypothesis: In active chromatin rt may depend on the length (lambda t) of the transcript of the primary messenger RNA (pre-mRNA). This new effect is subject to experimental verification. We discuss possible experiments that may be performed in order to test this prediction.

Animals↗

PubMed1992

Influence of chromatin molecular changes on RNA synthesis during embryonic development.

Two aspects of the chromatin repeat length (rl) are discussed: (i) Why is rl longer for slowly dividing cells than in rapidly dividing cells?, and (ii) Why is the temporal evolution of rl a decreasing function of time (t) in mammalian cortical neurons, whereas it is an increasing function of t for granule cells around the time of birth? These questions are discussed in terms of a hypothesis which assumes a correlation between deoxyribonucleic acid (DNA) packaging, transcription, and replication.

Animals↗

PubMed1990

On the possible effects of homeostatic shifts in human embryonic development.

Possible etiological factors of congenital malformations as well as of human trisomies are considered in the framework of the repressor hypothesis. In this approach gene expression is envisaged from the point of view of the functional variations of the total activation energy for normal gene expression in homeostatic equilibrium. We restrict our attention to variations of the total activation energy under the effect of temperature gradients. We discuss the evidence that hyperthermia may be an etiological factor for trisomies in humans.

Animals↗

PubMed1988

A kinetic thermodynamic phenomenological approach to genetic expression of heat-shock proteins.

The approach of viewing complex biochemical phenomena as autocatalytic relaxation processes has been introduced previously (Liquori & Tripiciano, 1980; Liquori & Florio, 1985). In the present work this formalism is extended from its original framework regarding cell growth, to the problem of genetic expression. The case of the heat-shock response in organisms ranging from man to bacteria is discussed. Finally, we give some biochemical examples in which the new approach underlines evident temporal co-operativity.

Gene Expression Regulation↗

PubMed1988

Evolutionary implication of genetic code deviations.

We formulate the following hypothesis: Life's origin may have occurred during the lower Archaean at a time when the environmental temperature was higher than it is at present. Preliminary consequences of this hypothesis are studied from the point of view of molecular evolution. We restrict our attention to implications regarding the genetic code. We conclude that alternative assignment of termination codons may be understood in terms of: (a) the elevated temperatures to which the progenote may initially have been exposed; and (b) the subsequent response of its genome to the opportunity provided by the eventual loss of hyperthermal genetic expression during a thermal transition (TT) period, which was triggered off by the evolution of the dynamic Earth.

Biological Evolution↗

PubMed1987

Towards a collective biology of the gene.

Two features of heterochromatin: heteropycnosis (high values of chromatin condensation), and repressed genetic expression, force upon us the use of cooperative variables, rather than molecular ones. In particular a "repressor" hypothesis is formulated, in which a useful parameter is clearly identified. This enables us to discuss the synchronized repression of a large number, n, of genes (as in the case of the Barr body, in which n is larger than 100). The hypothesis is documented with phenomena known to occur in active chromatin. Possible tests are suggested.

Chromosomes↗

PubMed1985

Evolution as a collective phenomenon.

The quantum mechanical description of biosystems, which emphasise their dielectric properties and the presence of an uncorrelated condensate of phonons, (in analogy with Bose-Einstein condensation), is extended to a description of biosystems, in which the condensed phonons show anomalous averages, (in analogy with superconductivity). The theory is used to show that a quantum ultraviolet defence mechanism may have been present at the origin of chemical evolution, removing a difficulty in the standard scenario. Suggestions are made as to how to proceed experimentally to show the existence of a correlated phonon condensate.

Biological Evolution↗