SEARCH · PubMed Health

Results for “Evolutionary adaptability”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources

PubMed2005

Presence of a novel small RNA-containing virus in a laboratory culture of the endoparasitic wasp Venturia canescens (Hymenoptera: Ichneumonidae).

Parasitoid wasps use a variety of mechanisms to alter their host's physiology to the benefit of the developing endoparasite inside the host larva. Association of certain wasps with viruses and virus-like particles (VLPs) that contribute to their success in parasitism is one of the fascinating evolutionary adaptations conferring active or passive protection for the endoparasite from the host immune system. Venturia canescens has been shown to produce VLPs that provide protection for the developing parasitoid egg inside the host, Ephestia kuehniella. Here, we report on the presence of a novel small RNA-containing virus from V. canescens, designated as VcSRV, occurring in the ovaries of the wasp. The virus particles are found together with VcVLPs in the lumen of the calyx region of the ovaries and are injected together with the egg and VcVLPs into E. kuehniella larvae where they enter hemocytes. Alignment of the RNA-dependent RNA polymerase gene of VcSRV indicates that the virus most likely belongs to the recently described genus Iflavirus.

Amino Acid Sequence↗

PubMed2005

Food restriction, evolution and ageing.

The food restriction model for life extension is nearing "three-score and 10" years of age and remains in good shape, preserving much of the mystique of its youth. Although originally described for laboratory rodents, recent work shows that food restriction also appears to slow ageing processes in a range of other animal species, raising the question of whether this response represents some generalised evolutionary adaptation, perhaps a strategy to cope with periods of famine. If the food restriction response does have an adaptive basis, this would suggest that specific gene regulatory processes have evolved to shape the organism's physiological response to food restriction. It will then be important to investigate how these are organised and whether the same or different factors are at play in the various species in which food restriction extends life span.

Aging↗

PubMed2004

Enhanced nutrition of offspring as a crucial factor for the evolution of intelligence on land.

Whilst life in the sea is undoubtedly an ancient process organisms with an exclusively marine lineage have not evolved the degree of intelligence demonstrated by the most advanced terrestrial species. Among the differences between terrestrial and marine environments which may begin to account for this is the instability of the terrestrial environment in comparison to the ocean. Unlike the ocean, terrestrial environments are not buffered against rapid changes in temperature, available water and other environmental extremes. This represents a challenge for the vulnerable offspring of terrestrial species. Evolutionary adaptation to this challenge has included greater transfer of resources from adult to offspring, as demonstrated by terrestrial vertebrates. However the evolution of mechanisms allowing enhanced transfer of resources between generations also creates conditions whereby offspring can be born with larger and more costly brains, developed and nourished from the outset even when they are not likely to prove useful until later life. As nutrition of offspring on land improved through natural selection better brains may thereby have been facilitated, with subsequent evolution driven by proximate selective pressures. The culmination of this process may be seen in the enormous transfer of resources from parents to offspring characteristic of humans and the advanced intelligence associated with them. Medical implications of this theory include the possible impact on the maternal brain of increased transfer of resources to the developing brain during pregnancy and lactation. This could help to account for the observed association between mental illness and the puerperium.

Adaptation, Physiological↗

PubMed2004

Autonomic dysfunction may be an under-recognized cause of female fertility disorders.

Female conditions of impaired fertility comprise a heterogeneous group of disorders that are attributed to various anatomic, hormonal and immunologic disturbances. We hypothesize that autonomic dysfunction may be a previously unrecognized factor in female fertility disorders. Emerging physiologic and molecular evidence suggests that autonomic balance varies during normal menstrual cycles with a shift to sympathetic bias during the luteal phase. Furthermore, many diseases associated with autonomic dysfunction show catamenial variations in patterns consistent with a shift to sympathetic bias occurs during the second half of normal menstrual cycles. The shift to sympathetic bias during the normal luteal phase may be an evolutionary adaptation to address the immunologic and physiologic demands for successful implantation and gestation. Through direct modulation of the lymphoid system and activation of the cortisol pathway, sympathetic bias promotes a shift to relative T helper (Th)-2 biased immunity which may favor maternal tolerance of the embryo by attenuating Th-1 mediated interference of implantation. Indeed, a growing body of evidence has implicated abnormal Th balance in fertility disorders, but the link has been attributed to factors other than autonomic function, such as hormonal factors. After implantation, maternal sympathetic bias may further support gestation through physiologic changes necessary to maintain placental perfusion pressure. We propose that insufficient shift to sympathetic bias during the luteal phase, which manifests in inadequate shift towards Th-2 bias and down-regulation of Th-1 function, may be the mechanism of impaired fertility in certain patients. Our hypothesis portends new potential methods to treat fertility disorders by modulating autonomic balance.

Autonomic Nervous System Diseases↗

PubMed2005

Protein transport in Archaea: Sec and twin arginine translocation pathways.

The transport of proteins into and across hydrophobic membranes is an essential cellular process. The majority of proteins that are translocated in an unfolded conformation traverse the membrane by way of the universally conserved Sec pathway, whereas the twin arginine translocation pathway is responsible for the transport of folded proteins across the membrane. Structural, biochemical and genetic analyses of these processes in Archaea have revealed unique archaeal features, and have also provided a better understanding of these pathways in organisms of all domains. Further study of these pathways in Archaea might elucidate fundamental principles involved in each type of transport and could help determine their relative costs and benefits as well as evolutionary adaptations in protein secretion strategies.

Amino Acid Sequence↗

PubMed2006

Bdellovibrio: growth and development during the predatory cycle.

Predatory Bdellovibrio enter the periplasm of other Gram-negative bacteria, growing within and consuming them. Unravelling molecular details of this intimate association between bacterial predator and prey is challenging yet fascinating, and might lead to novel antibacterials in the future. Pioneering physiological and biochemical studies described the predatory life of Bdellovibrio in the 1960s and 1970s, later followed by recombinant DNA work in the 1990s, which led to a revival in Bdellovibrio molecular research. This revival continues in the 21st century with the advent of a genome sequence. Now worldwide research is underway on the comparative genomics and transcriptomics of predatory bacteria, and will illuminate the evolutionary adaptations to become predatory, and will hopefully ultimately illuminate how the predatory processes of Bdellovibrio can be employed against pathogenic bacteria and for humankind.

Bacterial Adhesion↗

PubMed2005

Planetary systems biology.

Combining paleogenetics, protein engineering, synthetic biology, and metabolic modeling, a planetary biology perspective is brought to bear on adaptive evolutionary events in ancient bacteria.

Bacterial Physiological Phenomena↗

PubMed2004

Absence of association with cancer risk and low frequency of alterations at a p53 responsive PIG3 gene polymorphism in breast and lung carcinomas.

The mechanisms of p53-dependent apoptosis involve a set of genes that possess the ability to modulate oxidative stress. One of them PIG3, is induced by p53 through a microsatellite in its promoter region. This microsatellite was found to acquire its full structure and p53-functional dependence only in Hominoidea (apes and humans) and has been proposed to represent an evolutionary adaptation of tumor suppressor mechanisms. Microsatellite instability and genetic constitution, comprising the presence of the low repetition allele (10 TGYCC repeats), at this locus have been hypothesized to provide an increased risk for cancer development. Therefore, in the present analysis we examined this polymorphism in two common human cancers, lung and breast and compared it with corresponding control cases. Furthermore, for lung cancer we employed two different ethnic groups, Greek and British. Analysis of this locus in this types of tumors showed: (1) a very low frequency of microsatellite instability and loss of heterozygosity (1.4% and 4%, respectively) in the examined carcinomas, (2) the homozygous presence of the 10 repeats allele only in the control cases, and (3) a non-significant increase of the most frequent allele (15 repeats) in the cancer groups as compared to control ones. The last two observations were found in both Greek and British populations. Taken together, these data do not support the notion that this PIG3 polymorphism is associated with an increased risk for cancer susceptibility. Larger studies including other types of cancer should also be performed.

Base Sequence↗

PubMedDate not supplied

Optimizing conductance parameters of cortical neural models via electrotonic partitions.

Development of automated methods for fitting computational models to observed biological data is an important challenge of neural modeling. Previous work has focused on generalized search techniques combined with distance measures tuned to specific neural morphologies. We propose general analysis techniques to guide construction of distance measures across a broader range of cell types. Specifically, we evaluate the use of multiple external stimuli to evoke characteristic behaviors of underlying active channel densities on a simple three-compartment model. We also examine the use of frequency analysis to smooth search space distortions induced by temporal shifts in recorded voltage traces. We propose a novel method of parameter optimization that is characterized by linear regression over the conductance densities using channel permissiveness as a basis of ionic current. We derive this method and demonstrate, given known anatomy and kinetics, it will solve all conductance densities in an N compartment model given N spatially distinct membrane potential traces with minimal error. We compare the regression method with the covariance matrix adaptation evolutionary strategy (CMA-ES) over a two-compartment cortical neuron and empirically show that regression over electrotonic partitions solves the cortical model near-optimally. We also show that electronic partitioning significantly improves search performance of CMA-ES on the cortical model.

Algorithms↗

PubMed2005

A direct brainstem-amygdala-cortical 'alarm' system for subliminal signals of fear.

We examined whether consciously undetected fear signals engage a collateral brainstem pathway to the amygdala and prefrontal cortex in the intact human brain, using functional neuroimaging. 'Blindsight' lesion patients can respond to visual fear signals independently from conscious experience, suggesting that these signals reach the amygdala via a direct pathway that bypasses the primary visual cortex. Electrophysiological evidence points to concomitant involvement of prefrontal regions in automatic orienting to subliminal signals of fear, which may reflect innervation arising from brainstem arousal systems. To approximate blindsight in 22 healthy subjects, facial signals of fear were presented briefly (16.7 ms) and masked such that conscious detection was prevented. Results revealed that subliminal fear signals elicited activity in the brainstem region encompassing the superior colliculus and locus coeruleus, pulvinar and amygdala, and in fronto-temporal regions associated with orienting. These findings suggest that crude sensory input from the superior colliculo-pulvinar visual pathway to the amygdala may allow for sufficient appraisal of fear signals to innervate the locus coeruleus. The engagement of the locus coeruleus could explain the observation of diffuse fronto-temporal cortical activity, given its role in evoking collateral ascending noradrenergic efferents to the subcortical amygdala and prefrontal cortex. This network may represent an evolutionary adaptive neural 'alarm' system for rapid alerting to sources of threat, without the need for conscious appraisal.

Adult↗

PubMed2004

Noradrenaline storage function of species-specific protein bodies, markers of monoamine neurons in human locus coeruleus demonstrated by dopamine-beta-hydroxylase immunogold localization.

Our histochemical and ultrastructural studies have identified, in human catecholamine locus coeruleus (LC) neurons, abundant and large spherical protein bodies (PB), containing histone-like, arginine-rich proteins, which originate as dense bodies in mitochondria. This species-specific phenotype in the neurons of man is highly intriguing. In the electron microscope PB are disrupted in LC neurons in depressed individuals, where noradrenaline is known to be reduced. This coincidence of ultrastructure and neurochemistry raises the question whether these bodies could qualify as noradrenaline-storing organelles in the human LC. Our rationale was to examine, in known model tissues that contain catecholamines--sympathetic ganglia and tumors of the autonomic nervous system--if vesicles show the same fine structure and histochemistry as the PB of the human LC. Hence, we selected biopsy tissues of five ganglioneuromas and postmortem tissues of LC from 25 control subjects. Since dopamine-beta-hydroxylase (DBH) is a hallmark of noradrenaline identity and present in dense core vesicles, the investigation of DBH localization with the immunogold method constituted the experiment of choice for this study. Histochemical determinations of arginine with Carmoisine L, and of lipids with Rhodamine B complemented the study of similarities between the PB of the human LC and ganglioneuromas. Our results showed, with the colloidal gold method, that DBH immunogold labeling was localized in the core and in the double membranes of the PB, and also in the adjacent mitochondria. These results indicate that protein bodies (a) are unequivocal storage vesicles of noradrenaline, and (b) derive from regular mitochondria and represent a new phenotype in man, which is probably an evolutionary adaptation of amine-storing organelles.

Adult↗

PubMed2006

Phlebotomine sand flies and Leishmania parasites: friends or foes?

Leishmania parasites need phlebotomine sand flies to complete their life cycle and to propagate. This review looks at Leishmania-sand fly interactions as the parasites develop from amastigotes to infectious metacyclics, highlighting recent findings concerning the evolutionary adaptations that ensure survival of the parasites. Such adaptations include secretion of phosphoglycans, which protect the parasite from digestive enzymes; production of chitinases that degrade the stomodeal valve of the sand fly; secretion of a neuropeptide that arrests midgut and hindgut peristalsis; and attaching to the midgut to avoid expulsion.

Adaptation, Physiological↗

PubMed2004

Dynamics of insertion sequence elements during experimental evolution of bacteria.

We review the intersection between two areas of microbial evolution that were research foci of Michel Blot. One focus is the behavior of insertion sequence (IS) elements, including their role in promoting the evolutionary adaptation of their hosts. The other focus is experimental evolution, an approach that allows the dynamics of genomic and phenotypic change to be observed in the laboratory. This review shows that IS elements are useful as markers for detecting genomic change over experimental time scales and, moreover, that IS elements generate some of the beneficial mutations that increase organismal fitness.

DNA Transposable Elements↗

PubMed2005

Evolutionary approaches to understanding sleep.

A major controversy over REM sleep's role in memory processing may owe to inadequate allowances for the highly conservative nature of evolutionary adaptations. The controversy hinges on whether NREM sleep, alone, retains primitive memory processing capabilities. The selective pressure for primitive sleep, is thought to have been the need to obviate conflicts between enormous neural processing requirements of complex visual analysis and split-second control of movements, on the one hand, and memory processing, on the other. The most efficient memory processing during mammalian and avian sleep appears to be a two-step process: synapses in individual component circuits of events are reinforced primarily by slow brain waves during NREM sleep, with the reinforced components temporally bound by fast waves, and manifested as dreams, during REM sleep. This dual action could account for partitioning of sleep periods into multiple NREM-REM cycles. It is proposed that in the absence of REM sleep, all needed memory processing can be accomplished by NREM sleep, alone, though less efficiently. Many symptoms of fatal familial insomnia are attributed to subnormal nightly reinforcement of brain circuitry because of almost total loss of sleep, and compensatory responses thereto during waking. During this disorder, sensory circuitry seemingly is spared by virtue of its supernormal reinforcement during almost continuous waking. Contrariwise, sparing of an adult's 'higher faculties' in encephalitis lethargica appears to owe to supernormal circuit reinforcement during almost continuous sleep.

Awareness↗

PubMed2006

Ion transport versus gas conduction: function of AMT/Rh-type proteins.

Although lipid membranes exhibit some permeability to the weak base NH3, organisms have developed specialized proteins that increase and regulate the NH3 fluxes across cellular membranes. In humans, the Rh glycoproteins, such as the erythrocyte-specific RhAG and the liver and kidney homologs RhBG and RhCG, are involved in the passage of NH3. Rh glycoproteins have distant relatives, called ammonium transporters (AMTs), in archae and bacteria. The crystal structures of AMTs show that the proteins are homo-trimers and that the center of each monomer forms a pore. AMT/Rh proteins have also been identified in plants. In contrast to the human Rh glycoproteins, these AMTs specifically transport NH4+ or co-transport NH3/H+. Hence, they can transport against NH3 gradients. The molecular determinants for the different transport mechanisms within proteins of the same family are currently unclear. The functional differences between AMT/Rh transporters are likely to be an evolutionary adaptation to different ammonium and nitrogen requirements in bacteria, plants and animals.

Ammonia↗

PubMed2004

Molecular phylogeny of the antitropical genus Pseudolabrus (Perciformes: Labridae): evidence for a Southern Hemisphere origin.

The genus Pseudolabrus comprises 11 species of marine nearshore fishes which are antitropically distributed: two species occur in East Asia, the remaining nine species being distributed in the Southern Hemisphere, mainly in the temperate Pacific. The distributions of their closely allied genera, collectively called "pseudolabrines" are, however, restricted to the Australia-New Zealand region. The molecular phylogeny of six of the 11 Pseudolabrus species from both Hemispheres and four of the five other pseudolabrine genera was reconstructed from nucleotide sequence data from mitochondrial DNA 12S rRNA, tRNAVal, and 16S rRNA genes. Both parsimony and Bayesian analyses were performed. Results are not consistent with a previous phylogenetic hypothesis based on osteological data, particularly in the relationship between Pseudolabrus and Notolabrus, indicating a probable need for reviewing the status of Notolabrus (or the delimitations of both Pseudolabrus and Notolabrus). The two Northern Hemisphere species of Pseudolabrus were monophyletic and nested deep into the clade of the Southern Hemisphere pseudolabrines, which indicates that both pseudolabrines and Pseudolabrus originated in the Southern Hemisphere. A dispersal rather than vicariance explanation for the antitropical distribution of Pseudolabrus is more parsimonious given the number of dispersal events, extinctions, and evolutionary adaptations required under the phylogeny. Based on molecular clock calibrations, the transequatorial divergence was suggested to be early to mid Pliocene at the earliest.

Animals↗

PubMed2003

Theories of bipedal walking: an odyssey.

In this paper six theories of bipedal walking, and the evidence in support of the theories, are reviewed. They include: evolution, minimising energy consumption, maturation in children, central pattern generators, linking control and effect, and robots on two legs. Specifically, the six theories posit that: (1) bipedalism is the fundamental evolutionary adaptation that sets hominids--and therefore humans--apart from other primates; (2) locomotion is the translation of the centre of gravity along a pathway requiring the least expenditure of energy; (3) when a young child takes its first few halting steps, his or her biomechanical strategy is to minimise the risk of falling; (4) a dedicated network of interneurons in the spinal cord generates the rhythm and cyclic pattern of electromyographic signals that give rise to bipedal gait; (5) bipedal locomotion is generated through global entrainment of the neural system on the one hand, and the musculoskeletal system plus environment on the other; and (6) powered dynamic gait in a bipedal robot can be realised only through a strategy which is based on stability and real-time feedback control. The published record suggests that each of the theories has some measure of support. However, it is important to note that there are other important theories of locomotion which have not been covered in this review. Despite such omissions, this odyssey has explored the wide spectrum of bipedal walking, from its origins through to the integration of the nervous, muscular and skeletal systems.

Adult↗

PubMed2000

Gustatory responsiveness to food-associated sugars and acids in pigtail macaques, Macaca nemestrina.

Taste-preference thresholds for five food-associated sugars and acids, respectively, as well as relative sweet-taste preferences were assessed in six pigtail macaques using two-bottle choice tests of brief duration (1 min). In experiment 1, the animals were found to significantly prefer concentrations as low as 10 mM maltose and sucrose, 20 mM fructose and glucose, and 30 mM lactose over tap water. In experiment 2, the monkeys were given a choice between all binary combinations of the same five saccharides presented in equimolar concentrations of 50, 100, 200, and 400 mM. Preferences for individual sugars were stable across the concentrations tested and indicate the following order of relative effectiveness: maltose>sucrose>glucose> or =fructose> or =lactose. In experiment 3, Macaca nemestrina was found to significantly discriminate concentrations as low as 5 mM malic acid, 10 mM ascorbic acid, 20 mM citric acid and acetic acid, and 0.5 mM tannic acid from the alternative stimulus. With the latter substance, the monkeys rejected all suprathreshold concentrations tested, whereas with the former four substances, the animals showed an inverted U-shaped function of preference. The results showed pigtail macaques to be the first primate species tested so far whose taste-preference threshold for maltose is as low as that for sucrose, and which - similar to rodents - prefers maltose over equimolar concentrations of sucrose and other saccharides. Further, unlike most other primates, pigtail macaques do not generally reject acidic tastants but show a substance- and concentration-dependent change in their behavioral response that may range from rejection to preference. The results support the assumption that the gustatory responsiveness of M. nemestrina to food-associated sugars and acidic tastants might reflect an evolutionary adaptation to its dietary habits.

Acetic Acid↗