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PubMed2002

[Atypical transformation of cell populations after low irradiation and other actions].

Ionizing irradiation at low doses and some weak non-irradiational (including non-mutagenic) actions can produce a peculiar cell reaction, such as a massive, dose-independent transition to a new regime of existence. The changes appear saltationally. They are maintained for a very long time by both rarely and actively dividing cells. The most characteristic phenotype of the studied transformation is a stable increase of probability of cell damage and death. Some other manifestations of this transformation have been also revealed. This unusual response is found upon observation of totally different biological objects (unicellular organisms, cells of various mammalian tissues) to be regarded as a general biological regularity. The role of such radiational alterations in pathogenesis of remote consequences of low-dose irradiation is discussed.

Adaptation, Biological↗
PubMedDate not supplied

[Specific long-term cellular changes under effects of low doses of radiation].

We examined the peculiar form of a tissue postirradiative reaction characterizing by massive, dose-independent transition of cell populations to the steady state modification with the essential raise of cell damage and cell loss probability as compared with the probability level of the same alterations in controls. We described some other signs of such type of cellular transformation. It was found that the indicated cellular condition occurred both in active and slowly proliferating tissues. The reaction occurred at relatively low doses of irradiation. Some nonmutagenic factors also may evoke such effects. Our experimental data allow us to suppose the epigenetic mechanizms taking part in the induction and preservation of such alterations. The discovered form of cellular reaction manifestating in different biological objects may be considered as some general biological tendency. The importance of the studied reaction in the pathogenesis of late consequences of low dose irradiation is discussed.

Adaptation, Biological↗
PubMed2006

Physiological anthropology: past and future.

Environmental studies in adaptive human biology by North American anthropologists have a history of strong investigative research. From both laboratory and field work, we have gained major insights into human response to physical and social challenges. While these results were considered by most professionals to belong within evolutionary biology, in fact the intellectual structure sprang almost entirely from physiological equilibrium models. Consequently, physiological process itself was the focus. Further, most of the physiological patterns were not linked directly to important outcomes such as work output, reproductive success or survival. About 1975, American physiological anthropologists, led by Paul Baker, turned to studies of health, change and stress response. These studies were strong, but were still neither genetic nor evolutionary in intellectual structure. Evolutionary human biology was taken over by a new body of theory now called "behavior ecology", positing that selfish genes control human behavior to promote their own reproduction. This was paralleled by strong use of evolutionary theory in some areas of molecular biology. However, although physiological anthropologists have not focused on evolution, we have been developing powerful causal models that incorporate elements of physiology, morphology, physical environment and cultural behavior. In these "proximate" biocultural models, it is of little importance whether outcomes such as work or energy management are genetically based. Our future offers two major challenges. First, we must confirm causal links between specific physiological patterns and outcomes of practical importance to individuals and societies. Second, if we are to take our place in evolutionary biology, the one overarching theory of life on earth, we must understand the heritability of physiological traits, and determine whether they play a role in survival and reproduction.

Adaptation, Physiological↗
PubMed2005

Magnetic colloids for the generic capture of viruses.

In molecular biology or in the diagnostic field, a strong interest has been devoted to the use of magnetic nanoparticles as an efficient tool for a fast and easy biomolecule extraction. Various methods allow the synthesis of numerous types of magnetic particles, but very few of them can be adapted to biological protocols. For biological tests based on the final detection of nucleic acids, the major difficulties in the choice of these magnetic beads are their fast magnetic separation, requiring a high magnetic oxide content and overall a good compatibility with enzymes used for nucleic acid amplification. In this study, magnetic colloids were obtained from oil in water (o/w) magnetic emulsion by a two-step polymer immobilization procedure. First, a polycation, poly(ethyleneimine), was adsorbed to ensure charge inversion of the emulsion droplets. Then poly(maleic anhydride-co-methyl vinyl ether) was either chemically grafted or adsorbed if under its hydrolyzed form. The obtained colloids were characterized in terms of colloidal stability, surface charge density, and morphology and were evaluated in a reverse transcription-PCR (RT-PCR) inhibition test. Selected colloids were used for the nonspecific capture of viruses, with RT-PCR being used as a means of detection. Particle size and charge studies allowed us to follow each step of their synthesis, showing the relevance of these methods. The prepared magnetic particles exhibit a good RT-PCR compatibility when used in the range of 5-40 microg in the 50 microl amplification mix. Finally, virus capture tests revealed a capture efficiency of 90% with an average detection sensitivity of 10(3)pfu/ml.

Chromatography, Gel↗
PubMed2004

Do hosts and parasites coevolve? Empirical support from the Schistosoma system.

Coevolution between host and parasite is, in principle, a powerful determinant of the biology and genetics of infection and disease. However, coevolution is difficult to demonstrate rigorously in practice and therefore has rarely been observed empirically, particularly in animal-parasite systems. Research on host-schistosome interactions has the potential for making an important contribution to the study of coevolution or reciprocal adaptation. This may be particularly pertinent because schistosomes represent an indirectly transmitted macroparasite, so often overlooked among both theoretical and empirical studies. Here we present ideas and experiments on host-schistosome interactions, in part reviewed from published work but focusing in particular on preliminary novel data from our ongoing studies of potential host-schistosome evolution and coevolution in the laboratory. The article is split into three main sections: we first focus on the evidence for evolution in the host, then in the parasite, before combining both to illustrate the gathering evidence of host-parasite coevolution in the snail-schistosome system. In particular, we demonstrate that genetic architecture, variability, and selective pressures are present for the evolution of resistance and susceptibility, virulence, and infectivity to occur, the mechanisms allowing such polymorphisms to be maintained, and that hosts and parasites appear to have reciprocal effects on each other's phenotype and genotype.

Adaptation, Biological↗
PubMed1984

Evolutionary theory and teleology.

The order within and among living systems can be explained rationally by postulating a process of descent with modification, effected by factors which are extrinsic or intrinsic to the organisms. Because at the time Darwin proposed his theory of evolution there was no concept of intrinsic factors which could evolve, he postulated a process of extrinsic effects--natural selection. Biological order was thus seen as an imposed, rather than an emergent, property. Evolutionary change was seen as being determined by the functional efficiency (adaptedness) of the organism in its environment, rather than by spontaneous changes in intrinsically generated organizing factors. The initial incompleteness of Darwin's explanatory model, and the axiomatization of its postulates in neo-Darwinism, has resulted in a theory of functionalism, rather than structuralism. As such, it introduces an unnecessary teleology which confounds evolutionary studies and reduces the usefulness of the theory. This problem cannot be detected from within the neo-Darwinian paradigm because the different levels of end-directed activity--teleomatic, teleonomic, and teleological--are not recognized. They are, in fact, considered to influence one another. The theory of nonequilibrium evolution avoids these problems by returning to the basic principles of biological order and developing a structuralist explanation of intrinsically generated change. Extrinsic factors may affect the resultant evolutionary pattern, but they are neither necessary nor sufficient for evolution to occur.

Adaptation, Biological↗
PubMed2004

Protein homology detection using string alignment kernels.

MOTIVATION: Remote homology detection between protein sequences is a central problem in computational biology. Discriminative methods involving support vector machines (SVMs) are currently the most effective methods for the problem of superfamily recognition in the Structural Classification Of Proteins (SCOP) database. The performance of SVMs depends critically on the kernel function used to quantify the similarity between sequences. RESULTS: We propose new kernels for strings adapted to biological sequences, which we call local alignment kernels. These kernels measure the similarity between two sequences by summing up scores obtained from local alignments with gaps of the sequences. When tested in combination with SVM on their ability to recognize SCOP superfamilies on a benchmark dataset, the new kernels outperform state-of-the-art methods for remote homology detection. AVAILABILITY: Software and data available upon request.

Algorithms↗
PubMed2001

The BvgAS two-component system of Bordetella spp.: a versatile modulator of virulence gene expression.

Bordetella pertussis and the closely related species B. parapertussis and B. bronchiseptica colonize the respiratory tract and cause related diseases in man or mammalian species, respectively. Expression of virulence factors by these pathogens is coordinately regulated by the BvgAS two-component system according to changes in the growth conditions. Signal transduction by the BvgAS system is characterized by a complex His-Asp-His-Asp phosphorelay. This system controls the expression of two distinct subsets of genes either in a positive (vag genes) or in a negative (vrg genes) manner. Most of the known virulence factors such as several toxins and adhesins are encoded by vag genes, whereas the functions of most vrg genes and the biological significance of the vrg regulon are not yet clear. This review discusses the current knowledge about the molecular mechanisms of virulence regulation and their relevance for infection by these respiratory pathogens.

Adaptation, Biological↗
PubMed1978

Virulence and persistence of three prototype strains of mumps virus in newborn hamsters.

Neuroadapted mumps virus (NMV) produces widespread central nervous system (CNS) disease and death after intracerebral (i.c.) inoculation of newborn hamsters. After intraperitoneal (i.p.) inoculation, NMV causes disseminated disease, moderate mortality and it persists in CNS tissues. Low tissue culture passage isolates of wild mumps virus do not establish CNS infection after i.p. inoculation; after i.c. inoculation they cause limited though persistent infection with little acute mortality. The biological behavior of a highly passaged vaccine strain of mumps virus (Jeryl-Lynn) is more similar to NMV than to the wild strain in its behavior in the newborn hamster.

Adaptation, Biological↗
PubMed1975

Effects of domestication on animal behaviour.

Centuries of domestication of animals by civilised man have had many measurable effects on the various species involved, but only in relatively recent history has scientific curiosity been directed to assessing their extent. The process of domestication is analysed and its known effects on animals reviewed through observations of and experiments with various species of domesticated animals conducted by researchers into animal psychology and biology. The known facts on the effects of domestication in animals are extrapolated in an attempt to determine to what extent modern man himself has been domesticated in the urban environment.

Adaptation, Biological↗
PubMed2004

Global changes in gene expression in Sinorhizobium meliloti 1021 under microoxic and symbiotic conditions.

Sinorhizobium meliloti is an alpha-proteobacterium that alternates between a free-living phase in bulk soil or in the rhizosphere of plants and a symbiotic phase within the host plant cells, where the bacteria ultimately differentiate into nitrogen-fixing organelle-like cells, called bacteroids. As a step toward understanding the physiology of S. meliloti in its free-living and symbiotic forms and the transition between the two, gene expression profiles were determined under two sets of biological conditions: growth under oxic versus microoxic conditions, and in free-living versus symbiotic state. Data acquisition was based on both macro- and microarrays. Transcriptome profiles highlighted a profound modification of gene expression during bacteroid differentiation, with 16% of genes being altered. The data are consistent with an overall slow down of bacteroid metabolism during adaptation to symbiotic life and acquisition of nitrogen fixation capability. A large number of genes of unknown function, including potential regulators, that may play a role in symbiosis were identified. Transcriptome profiling in response to oxygen limitation indicated that up to 5% of the genes were oxygen regulated. However, the microoxic and bacteroid transcriptomes only partially overlap, implying that oxygen contributes to a limited extent to the control of symbiotic gene expression.

Adaptation, Biological↗
PubMed2000

Evolutionary biology and the concept of disease.

In recent years, an increasing number of medical books and papers attempting to analyse the concepts of health and disease from the perspective of evolutionary biology have been published (Eaton et al., 1993; Ewald, 1993; Harrison, 1993; Nesse and Williams, 1995; Profet, 1991; Rose, 1991; Temple and Burkitt, 1994). This paper introduces the evolutionary approach to health and disease in an attempt to illuminate the premisses and the framework of Darwinian medicine. My primary aim is to analyse to what extent evolutionary theory provides for a biological definition of the concept of disease. This analysis reveals some important differences between functional explanations in the field of evolutionary biology and functional explanations in the field of medicine. Moreover, I shall argue that the biological functions relevant to the health of an organism cannot be determined on the basis of evolutionary theory. Accordingly, it seems that Darwinian medicine does not provide for the definition of a biological concept of disease. Still, Darwinian medicine may suggest why we are susceptible to certain diseases; it might also prove a suggestive heuristic on the basis of which new hypotheses concerning relevant treatments of various diseases might be advanced.

Adaptation, Biological↗
PubMed1998

Biology of moderately halophilic aerobic bacteria.

The moderately halophilic heterotrophic aerobic bacteria form a diverse group of microorganisms. The property of halophilism is widespread within the bacterial domain. Bacterial halophiles are abundant in environments such as salt lakes, saline soils, and salted food products. Most species keep their intracellular ionic concentrations at low levels while synthesizing or accumulating organic solutes to provide osmotic equilibrium of the cytoplasm with the surrounding medium. Complex mechanisms of adjustment of the intracellular environments and the properties of the cytoplasmic membrane enable rapid adaptation to changes in the salt concentration of the environment. Approaches to the study of genetic processes have recently been developed for several moderate halophiles, opening the way toward an understanding of haloadaptation at the molecular level. The new information obtained is also expected to contribute to the development of novel biotechnological uses for these organisms.

Adaptation, Biological↗
PubMed2000

Dental caries and the microbial ecology of dental plaque: a review of recent advances.

Our understanding of the microbial ecology of dental plaque has rapidly grown with recent developments in the techniques of molecular biology. In particular, knowledge of the mechanisms underlying the acquisition, establishment, pathogenicity, and evolution of the group of organisms responsible for dental caries--the mutans streptococci--has expanded to the point that we can now contemplate new opportunities for caries prevention. These advances reinforce developing concepts of dental plaque as an interdependent, interacting community of specialised organisms with an ability to rapidly adapt conferred by gene structures that facilitate the expeditious modular rearrangement of protein components.

Adaptation, Biological↗
PubMed2005

The probability of parallel evolution.

How often will natural selection drive parallel evolution at the DNA sequence level? More precisely, what is the probability that selection will cause two populations that live in identical environments to substitute the same beneficial mutation? Here I show that, under fairly general conditions, the answer is simple: if a wild-type sequence can mutate to n different beneficial mutations, replicate populations will on average fix the same mutation with probability P = 2/(n + 1). This probability, which is derived using extreme value theory, is independent of most biological details, including the length of the gene in question and the precise distribution of fitness effects among alleles. I conclude that the probability of parallel evolution under natural selection is nearly twice as large as that under neutrality.

Adaptation, Biological↗
PubMed2006

Enter the matrix: how to analyze the structure of behavior.

Several methods are available for analyzing different aspects of behavioral transition matrices, but a comprehensive framework for their use is lacking. We analyzed parasitoid foraging behavior in environments with different plant species compositions. The resulting complex data sets were analyzed using the following stepwise procedure. We detected abrupt changes in the event log files of parasitoids, using a maximum likelihood method. This served as a criterion for splitting the event log files into two parts. For both parts, Mantel's test was used to detect differences between first-order transition matrices, whereas an iterative proportional fitting method was used to find behavioral flows that deviated from random transitions. In addition, hidden repetitive sequences were detected in the transition matrices on the basis of their relative timing, using Theme. We discuss the results for the example from a biological context and the comprehensive use of the different methods. We stress the importance of such a combined stepwise analysis for detecting differences in some parts of event log files.

Adaptation, Biological↗
PubMed2006

Chemical sensitivity in Caenorhabditis elegans.

The small nematode Caenorhabditis elegans lives in the soil, where mechanical, thermal and most of all chemical stimuli strongly influence its behavior. Here we briefly review how chemical sensitivity is organized at the cellular and molecular level in this organism. C. elegans has less than 40 chemosensory neurons. With few exceptions each neuron senses more than one substance and each substance is sensed by more than one neuron. At the molecular level, as in other organisms, also in C. elegans, seven transmembrane G-protein-coupled receptors (GPCRs), heterotrimeric G proteins, cyclic nucleotidegated ion channels, TRP channels and Ca++ play crucial roles in chemical sensitivity. An unusual feature, possibly due to C. elegans's strong dependence on chemical cues, is the very large number of GPCR chemoreceptor genes (1300-1700) coded in its genome. Genetic approaches have also allowed the identification of new molecules involved in chemical sensitivity that would not have been discovered otherwise. In addition to the basic factors involved in primary signalling, the studies in C. elegans have revealed a network of regulatory pathways and molecules suggesting that fine modulation of the responsiveness of neurons is important, possibly to allow worms to negotiate a continuously changing environment. The experimental versatility of C. elegans has made it possible, in many cases, to determine precisely in which neuron a given molecule or pathway is required and for which biological response. This type of information can contribute to the general field of sensory signalling because it provides correlations between the biochemical properties of molecules and their cellular functions and between these and the in vivo behavioral responses of the animal.

Adaptation, Biological↗