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PubMed1986

Molecular aspects of adaptation to extreme cold environments.

Here are reviewed and summarized the strategies adopted by living organisms to survive low temperatures, from a molecular and membrane point of view. The presentation is aimed at a wide variety of readers. Two prime examples of connections between biological cold adaptation and the molecular level are (1) antifreeze proteins in fish from cold sea water, (the DNA sequence of the protein gene is now known) (2) the fluidity characteristics of cell membranes in a wide variety of organisms. In model membranes of phospholipids, stabler "s-phases" have recently been found to form at low temperatures. Antarctic endolithic organisms, living just under the surface of rocks, are exposed to long periods of low temperatures, and may develop such phases in their membranes. In the saturated phosphatidyl cholines, only lipids with a restricted range of acyl chain lengths show simultaneously s-phases and a main transition : This restricted range is about the restricted range found in natural membranes. The s-phases also form in the presence of natural cryoprotectants, and may be connected with botanical vernalization.

Acclimatization↗
PubMed2003

The dual biological identity of human beings and the naturalization of morality.

The last two centuries have been the centuries of the discovery of the cell evolution: in the XIX century of the germinal cells and in the XX century of two groups of somatic cells, namely those of the brain-mind and of the immune systems. Since most cells do not behave in this way, the evolutionary character of the brain-mind and of the immune systems renders human beings formed by t wo different groups of somatic cells, one with a deterministic and another with an indeterministic (say Darwinian) behavior. An inherent consequence is that of the generation, during ontogenesis, of a dual biological identity. The concept of the dual biological identity may be used to explain the Kantian concept of the two metaphysical worlds, namely of the causal necessity and of the free will (Azzone, 2001). Two concepts, namely those of complex adaptive systems (CAS) and of emergence (Holland, 2002), are useful tools for understanding the mechanisms of adaptation and of evolution. The concept of complex adaptive systems indicates that living organisms contain series of stratified components, denoted as building blocks, forming stratified layers of increasing complexity. The concept of emergence implies the use of repeating patterns and of building blocks for the generation of structures of increasing levels of complexity, structures capable of exchanging communications both in the top-down and in the bottom-up direction. Against the concept of emergence it has been argued that nothing can produce something which is really new and endowed of causal efficacy. The defence of the concept of emergence is based on two arguments. The first is the interpretation of the variation-selection mechanism as a process of generation of information and of optimization of free energy dissipation in accord with the second principle of thermodynamics. The second is the objective evidence of the cosmological evolution from the Big Bang to the human mind and its products. Darwin has defended the concept of the continuity of evolution. However evolution should be considered as continuous when there is no increase of information and as discontinuous when there is generation of new information. Examples of such generation of information are the acquisition of the innate structures for language and the transition from absence to presence of morality. There are several discontinuity thresholds during both phylogenesis and ontogenesis. Morality is a relational property dependent on the interactions of human beings with the environment. Piaget and Kohlberg have shown that the generation of morality during childhood occurs through several stages and is accompanied by reorganization of the child mental organization. The children respect the conventions in the first stage and gradually generate their autonomous morality. The transition from absence to presence of morality, a major adaptive process, then, not only has occurred during phylogenesis but it occurs again in every human being during ontogenesis. The religious faith does not provide a logical justification of the moral rules (Ayala, 1987) but rather a psychological and anthropological justification of two fundamental needs of human beings: that of rendering Nature an understandable entity, and that of increasing the cooperation among members of the human societies. The positive effects of the altruistic genes in the animal societies are in accord with the positive effects of morality for the survival and development of the human societies.

Adaptation, Biological↗
PubMed2004

Gametocytogenesis: the puberty of Plasmodium falciparum.

The protozoan Plasmodium falciparum has a complex life cycle in which asexual multiplication in the vertebrate host alternates with an obligate sexual reproduction in the anopheline mosquito. Apart from the apparent recombination advantages conferred by sex, P. falciparum has evolved a remarkable biology and adaptive phenotypes to insure its transmission despite the dangers of sex. This review mainly focuses on the current knowledge on commitment to sexual development, gametocytogenesis and the evolutionary significance of various aspects of gametocyte biology. It goes further than pure biology to look at the strategies used to improve successful transmission. Although gametocytes are inevitable stages for transmission and provide a potential target to fight malaria, they have received less attention than the pathogenic asexual stages. There is a need for research on gametocytes, which are a fascinating stage, responsible to a large extent for the success of P. falciparum.

Animals↗
PubMed2001

Computational genomics.

We now know how to read the sequences of nucleotide letters that comprise the genome at a rather frightening speed--a several-million-base bacterial genome in several days is not a problem for one of the sequencing centers, and a billion-base eukaryotic genome can be done in less than a year. But reading a text and understanding it are two different things. So how well can we understand the genome sequences? The answer to this question is central to the whole enterprise of genomics, and this is where computational analysis of genomes takes the driver's seat. Here I will try to briefly outline some major goals, problems, challenges and approaches of computational genomics. Such a young field is already quite diverse, and in this short article I will concentrate on several issues that seen to be critical for deciphering biology from genome sequences, rather than mathematical and computer-science aspects that are well covered in several excellent books.

Adaptation, Biological↗
PubMed2002

Biological and biomedical implications of the co-evolution of pathogens and their hosts.

Co-evolution between host and pathogen is, in principle, a powerful determinant of the biology and genetics of infection and disease. Yet co-evolution has proven difficult to demonstrate rigorously in practice, and co-evolutionary thinking is only just beginning to inform medical or veterinary research in any meaningful way, even though it can have a major influence on how genetic variation in biomedically important traits is interpreted. Improving our understanding of the biomedical significance of co-evolution will require changing the way in which we look for it, complementing the phenomenological approach traditionally favored by evolutionary biologists with the exploitation of the extensive data becoming available on the molecular biology and molecular genetics of host-pathogen interactions.

Adaptation, Biological↗
PubMed2005

Genome reduction in the alpha-Proteobacteria.

More than 20 alpha-proteobacterial genomes are currently available. These range in size from 1-9 Mb and represent excellent model systems for evolutionary studies of the organizational features of bacterial genomes. Computational inferences have shown that genome reductions have occurred independently in lineages such as Rickettsia and Bartonella that are associated with intracellular lifestyles. Analyses of these reduced genomes have provided insights into the evolution of vector-borne transmission pathways. Further research into the population biology of bacteria, arthropods and vertebrate hosts will help to refine the biology of host-pathogen interactions and will facilitate the design of vaccines and vector-control programs.

Adaptation, Biological↗
PubMed1971

Biological ion exchanger resins. 3. Molecular interpretation of cellular ion exchange.

The cell is presented as a biological ion exchanger resin. The similarities between ion accumulating cells and ion exchanger resins are correlated. The kinetic characteristics of biological ion exchange are shown to be amenable to analysis by a model commonly used for ion exchanger resins. The theories of ion exchange equilibria currently in use with ion exchanger resins are reviewed with their suitability for adaptation to biological ion exchange in mind.

Biological Transport↗
PubMed1999

Adaptive neural coding dependent on the time-varying statistics of the somatic input current.

It is generally assumed that nerve cells optimize their performance to reflect the statistics of their input. Electronic circuit analogs of neurons require similar methods of self-optimization for stable and autonomous operation. We here describe and demonstrate a biologically plausible adaptive algorithm that enables a neuron to adapt the current threshold and the slope (or gain) of its current-frequency relationship to match the man (or dc offset) and variance (or dynamic range or contrast) of the time-varying somatic input current. The adaptation algorithm estimates the somatic current signal from the spike train by way of the intracellular somatic calcium concentration, thereby continuously adjusting the neurons' firing dynamics. This principle is shown to work in an analog VLSI-designed silicon neuron.

Adaptation, Physiological↗
PubMed1995

A modular artificial neural net for controlling a six-legged walking system.

A system that controls the leg movement of an animal or a robot walking over irregular ground has to ensure stable support for the body and at the same time propel it forward. To do so, it has to react adaptively to unpredictable features of the environment. As part of our study of the underlying mechanisms, we present here a model for the control of the leg movement of a 6-legged walking system. The model is based on biological data obtained from the stick insect. It represents a combined treatment of realistic kinematics and biologically motivated, adaptive gait generation. The model extends a previous algorithmic model by substituting simple networks of artificial neurons for the algorithms previously used to control leg state and interleg coordination. Each system controlling an individual leg consists of three subnets. A hierarchically superior net contains two sensory and two 'premotor' units; it rhythmically suppresses the output of one or the other of the two subordinate nets. These are continuously active. They might be called the 'swing module' and the 'stance module' because they are responsible for controlling the swing (return stroke) and the stance (power stroke) movements, respectively. The swing module consists of three motor units and seven sensory units. It can produce appropriate return stroke movements for a broad range of initial and final positions, can cope with mechanical disturbances of the leg movement, and is able to react to an obstacle which hinders the normal performance of the swing movement. The complete model is able to walk at different speeds over irregular surfaces. The control system rapidly reestablishes a stable gait when the movement of the legs is disturbed.

Gait↗
PubMed1997

Germ theory vs. community theory in understanding and controlling the proliferation of biofilms.

Germ theory and pure culture methods have provided invaluable information concerning the role of bacteria in diseases resulting from a single organism which bypasses a host's defenses. However, they do not provide sufficient information concerning the synergisms which allow the members of biofilm communities to proliferate more effectively as communities rather than as individuals. The mechanisms of these synergies are potential targets for antimicrobial agents as well as potential mechanisms of resistance to antimicrobial agents. Understanding community-level phenomena in oral biology requires the culture, identification, and classification of functional plaque communities as well as new methods of identifying and quantifying communal relationships. Cultured biofilm communities also provide ideal models of bacterial self-organization in which information related to adaptive strategies arises not only through the recombination of genes within genomes, but also through the recombination of organisms within communities.

Adaptation, Biological↗
PubMed2004

[Biology of size and gravity].

Gravity is a force that acts on mass. Biological effects of gravity and their magnitude depend on scale of mass and difference in density. One significant contribution of space biology is confirmation of direct action of gravity even at the cellular level. Since cell is the elementary unit of life, existence of primary effects of gravity on cells leads to establish the firm basis of gravitational biology. However, gravity is not limited to produce its biological effects on molecules and their reaction networks that compose living cells. Biological system has hierarchical structure with layers of organism, group, and ecological system, which emerge from the system one layer down. Influence of gravity is higher at larger mass. In addition to this, actions of gravity in each layer are caused by process and mechanism that is subjected and different in each layer of the hierarchy. Because of this feature, summing up gravitational action on cells does not explain gravity for biological system at upper layers. Gravity at ecological system or organismal level can not reduced to cellular mechanism. Size of cells and organisms is one of fundamental characters of them and a determinant in their design of form and function. Size closely relates to other physical quantities, such as mass, volume, and surface area. Gravity produces weight of mass. Organisms are required to equip components to support weight and to resist against force that arise at movement of body or a part of it. Volume and surface area associate with mass and heat transport process at body. Gravity dominates those processes by inducing natural convection around organisms. This review covers various elements and process, with which gravity make influence on living systems, chosen on the basis of biology of size. Cells and biochemical networks are under the control of organism to integrate a consolidated form. How cells adjust metabolic rate to meet to the size of the composed organism, whether is gravity responsible for this feature, are subject we discuss in this article. Three major topics in gravitational and space biology are; how living systems have been adapted to terrestrial gravity and evolved, how living systems respond to exotic gravitational environment, and whether living systems could respond and adapt to microgravity. Biology of size can contribute to find a way to answer these question, and answer why gravity is important in biology, at explaining why gravity has been a dominant factor through the evolutional history on the earth.

Adaptation, Physiological↗
PubMed2006

Comment on "Statistical independence of escalatory ecological trends in Phanerozoic marine invertebrates".

Madin et al. (Reports, 12 May 2006, p. 897) reported that escalation has not been an important cause of biological change throughout the history of life. However, they evaluated the escalation hypothesis with inappropriate data. First, global-scale data integrate heterogeneous signals that obscure the economic context of life. Second, diversity data cannot yield information about selection and adaptation.

Adaptation, Biological↗
PubMed1979

Renal conservation of antifreeze peptide in Antarctic eelpout, Rhigophila dearborni.

In Antarctic notothenioid fishes large amounts (3% w/v) of small molecular weights of 2,600-23,500 and would be expected to be filtered into the urine, they remain in the blood because the kidneys of these fishes contain only aglomerular nephrons. Unlike the situation in most fishes, urine formation is the result of secretion rather than filtration and reabsorption. On the other hand, the peptide antifreezes in Northern Hemisphere fishes such as the winter flounder. Pseudopleuronectes americanus, are retained by the glomerular kidney even though inulin, of comparable weight, is rapidly filtered from the blood into the urine. The Antarctic eelpout (zoarcid), Rhigophila dearborni, which is unrelated to either the Antarctic notothenioids or P. americanus, also uses a peptide antifreeze (molecular weight 6,000) which is maintained at a concentration of 3% (w/v) in the blood plasma. We report here that the lack of antifreeze in the urine of R. dearborni probably reflects the fact that the glomeruli are not functional and cannot filter. We support this conclusion with morphological and physiological evidence and relate our findings to the conservation of biological antifreeze necessary for life in ice-laden polar waters.

Adaptation, Biological↗
PubMed2000

[The medicosocial aspects of the adaptation of servicemen].

The peculiarities of servicemen' adaptation at biological, psychological and social levels under peace-time conditions and during the fighting in Chechen Republic were studied with the help of clinical and physiological, psychophysiological and psychosociological methods. The method of integral qualitative and semi-quantitative assessment of human adaptation is described. It is shown that the main stage of adaptation in servicemen lasts not less than 1 year. However the complete adaptation of military men by the end of their service usually doesn't occur. The variants of adaptation course and perspective methods of its acceleration, character and causes of dysadaptive disorders in servicemen who participated in antiterrorist operations are discussed.

Adaptation, Physiological↗