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Results for “Evolutionary adaptability”

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PubMed2002

Gustatory responsiveness to food-associated saccharides in European rabbits, Oryctolagus cuniculus.

Taste preference thresholds for six food-associated saccharides and relative sweet-taste preferences were assessed in 12 European rabbits using two-bottle choice tests of brief duration (3 min). In Experiment 1, the animals were found to significantly prefer concentrations as low as 30 mM maltose, 50 mM polycose and sucrose, 75 mM glucose, 150 mM fructose, and 175 mM lactose over tap water. In Experiment 2, the rabbits were given a choice between all binary combinations of the same six saccharides presented in equimolar concentrations of 100 and 200 mM. Preferences for individual saccharides were stable across the concentrations tested and indicate the following order of relative effectiveness: maltose=polycose>sucrose>glucose>fructose > or =lactose. The results showed rabbits to display a pattern of taste preference thresholds and relative taste preferences for food-associated saccharides similar to that found in rodents but differing markedly from that found in human and nonhuman primates. The results support the assumptions that rabbits, unlike most primates, but similar to rodents, may have specialized taste receptors for starch, and that the gustatory responsiveness of Oryctolagus cuniculus to food-associated saccharides might reflect an evolutionary adaptation to its dietary habits.

Animals↗

PubMed2001

Sensitized polygenic trait analysis.

Genetic variation in many biological processes and evolutionary adaptations is caused by polygenes--genes that act in combination to affect a particular trait. Despite the recent identification of several polygenes, many remain to be found, suggesting that new experimental and analytical methods are needed to facilitate their discovery. Here we discuss sensitized polygenetic trait analysis, a method that has emerged recently for simplifying the genetic analysis of polygenic traits. The method uses a known single gene mutation in linkage testing crosses to 'sensitize' the analysis. By increasing the frequency of affected individuals in segregating populations, linkages are more readily detected. This method has considerable potential, especially given the increasing variety of mutations that can be used to sensitize the genetic analysis of polygenic traits.

Animals↗

PubMed2002

Pancreatic polypeptide receptors: affinity, sodium sensitivity and stability of agonist binding.

Cloned rat, human and guinea-pig Y4 pancreatic polypeptide (PP) receptors expressed in Chinese hamster ovary (CHO) cells, as well as the rabbit Y4-like PP receptor, show a selective sensitivity to Na+ over K+ ion in PP attachment, but little sensitivity to Na+ in dissociation of bound PP peptides. Agonist binding to Y4 receptors of intact CHO cells also shows much greater sensitivity to Na+ over K+, and a tenacious attachment of the bound agonist. Binding sensitivity to K+ is greatly enhanced upon receptor solubilization. Pancreatic polypeptide sites also show large sensitivity to modulators of Na+ transport such as N5-substituted amilorides and to RFamides, as different from Y1 or Y2 receptors. Thus, PP binding is modulated by cation-induced changes in site environment (with selectivity for Na+) and ultimately results in a blocking attachment. This would support receptor operation in the presence of ion gradients, as well as prolonged agonist-delimited signaling activity (which can include partial antagonism). Also, this could point to an evolutionary adaptation enabling small numbers of PP receptors to perform extensive metabolic tasks in response to low agonist signals.

Amino Acid Sequence↗

PubMed1997

Immune privilege, T-cell tolerance, and tissue-restricted autoimmunity.

The eye is one of several specialized organs/tissues that display immune privilege, i.e. sites that permit foreign tissue grafts to enjoy prolonged (or even indefinite) survival. Immune privilege is an active, rather than a passive, process in which specialized tissues/sites and the immune system collaborate in providing immune protection without the risk of immunopathogenic injury to the tissue itself. Among the mechanisms that have been found to contribute to immune privilege is tolerance of peripheral T cells. Over the past few years, investigators have demonstrated at least four different pathways by which immune privilege can lead to T-cell tolerance: clonal deletion, clonal anergy, immune deviation, and T-cell suppression. In the case of the eye, privilege exists in part because antigens introduced into the eye are captured by distinctive local antigen-presenting cells that migrate via the blood to the spleen. At that site, they generate a stereotypic systemic immune response that is deficient in CD4+ T cells that mediate delayed hypersensitivity and that help B cells to secrete complement-fixing antibodies, yet replete with CD8+ T cells that function as cytotoxic cells and as regulatory cells. This response, termed anterior chamber associated immune deviation (ACAID), is mediated by antigen-specific regulatory T cells that secrete TGFbeta in an autocrine fashion and suppress effector functions of inflammogenic CD4+ T cells. Because intraocular inflammation is deleterious to vision, ACAID and immune privilege are considered to be evolutionary adaptations that enable the eye to benefit from immune protection against pathogens without suffering blindness from immune injury.

Animals↗

PubMed1997

Purification and characterisation of hepatic glutathione transferases from a herbivorous marsupial, the brushtail possum (Trichosurus vulpecula).

A single glutathione transferase isoenzyme was purified from hepatic cytosol of the brushtail possum and shown to represent 3.6 +/- 0.3% of the total cytosolic protein. Characterisation of the enzyme, termed Possum GST 1-1, indicated that it possessed similar catalytic activity and structural homology with isoenzymes belonging to the alpha class of glutathione transferases. This homodimeric GST exhibited a single band with an apparent molecular mass of 25.4 kDa on sodium dodecyl sulphate-polyacrylamide gels and an apparent pI of 9.8. Inhibition studies demonstrated that Possum GST 1-1 displays binding affinity for a range of inhibitors similar to that shown by alpha class GSTs purified from other mammals. Immunoblot analysis demonstrated immuno-cross reactivity between Possum GST 1-1 and antisera raised against human alpha GST, while this GST did not cross-react with antisera raised against human mu and pi GST. N-terminal sequencing of purified Possum GST 1-1 revealed that the N-terminus of the protein is chemically blocked. Sequence analysis of three internal peptide sequences demonstrated homology with mammalian alpha GSTs. Of particular interest is the significant substrate specificity that Possum GST 1-1 displays with both organic and inorganic hydroperoxides. It is proposed that this substrate specificity is an evolutionary adaptation to a diet high in potentially toxic plant allelochemicals.

Amino Acid Sequence↗

PubMed2002

Why can't Chinese Han drink alcohol? Hepatitis B virus infection and the evolution of acetaldehyde dehydrogenase deficiency.

An aldehyde-dehydrogenase (ALDH2) deficiency is a biological curb on excess alcohol-drinking. This enzyme deficiency is very common amongst Oriental people while it is relatively rare for most other populations. We observe that there is good geographical correlation between the prevalence of the mutant ALDH2*2 alleles and hepatitis B virus (HBV) infections. Populations that demonstrate a high ALDH2*2 prevalence are all located in HBV-endemic areas. Further, studies have shown that HBV and alcohol drinking exhibit a synergistic effect upon liver cirrhosis and cancer. A shorter life span for those with HBV infection and heavy alcohol consumption may result in a selection of the ALDH2*2 gene. We postulate that there may be patterns of evolutionary adaptation for ALDH2 deficiency in certain HBV-endemic areas and that these adaptations can produce differences in human alcohol-drinking capability.

Alcohol Drinking↗

PubMed1997

Origin and evolution of sleep: roles of vision and endothermy.

The origin of both sleep and memory appears to be closely associated with the evolution of mechanisms of enhancement and maintenance of synaptic efficacy. After the origin of activity-dependent synaptic plasticity, whereby single activations of synapses led to short-term efficacy enhancements, lengthy maintenance of the enhancements probably was achieved by repetitive activations ("dynamic stabilization"). These are thought to have occurred either in the course of frequent functional use, or to have been induced spontaneously within the brain to maintain synaptic efficacies in circuits that were in infrequent use. The latter repetitive activations are referred to as 'non-utilitarian' dynamic stabilization. With the evolution of increasing repertories and complexities of behavioral and sensory capabilities-with vision usually being the vastly preeminent sense-brain complexity increased markedly. Accompanying the greater complexity, needs for storage and maintenance of hereditary and experimental information (memories) also increased greatly. It is suggested that these increases led to conflicts between sensory input processing during restful waking and concomitant 'non-utilitarian' dynamic stabilization of infrequently used memory circuits. The selective pressure for the origin of primitive sleep may have been a need to achieve greater depression of central processing of sensory inputs-largely complex visual information-than occurs during restful waking. The electrical activities of the brain during sleep (aside from those that subserve autonomic activities) may function largely to maintain sleep and to dynamically stabilize infrequently used circuitry encoding memories. Sleep may not have been the only evolutionary adaptation to conflicts between dynamic stabilization and sensory input processing. In some ectothermic vertebrates, sleep may have been postponed or rendered unnecessary by a more readily effected means of resolution of the conflicts, namely, extensive retinal processing of visual information during restful waking. By this means, processing of visual information in central regions of the brain may have been maintained at a sufficiently low level to allow adequate concomitant dynamic stabilization. As endothermy evolved, the skeletal muscle hypotonia of primitive sleep may have become insufficient to prevent sleep-disrupting skeletal muscle contractions during 'non-utilitarian' dynamic stabilization of motor circuitry at the accompanying higher body temperatures and metabolic rates. Selection against such disruption during dynamic stabilization of motor circuitry may have led to the inhibition of skeletal muscle tone during a portion of primitive sleep, the portion designated as "rapid-eye-movement sleep." Many marine mammals that are active almost continuously engage only in unihemispheric non-rapid-eye-movement sleep. They apparently do not require rapid-eye-movement sleep and accompanying 'non-utilitarian' dynamic stabilization of motor circuitry because this circuitry is in virtually continuous use. Studies of hibernation by arctic ground squirrels suggest that each hour of sleep stabilizes brain synapses for as long as four hours.

Animals↗

PubMed2002

The biological effects of solar activity.

The synchronization of biological circadian and circannual rhythms is broadly viewed as a result of photic solar effects. Evidence for non-photic solar effects on biota is also slowly being recognized. The ultrastructure of cardiomyocytes from rabbits, the time structure of blood pressure and heart rate of neonates, and the heart rate variability of human adults on earth and in space were examined during magnetically disturbed and quiet days, as were morbidity statistics. Alterations in both the about-daily (circadian) and about-weekly (circaseptan) components are observed during disturbed vs. quite days. The about-weekly period of neonatal blood pressure correlates with that of the local geomagnetic disturbance index K. Circaseptans which are seen early in human life and in various other forms of life, including unicells, may provide information about the possible site(s) of life's origins from an integrative as well as adaptive evolutionary perspective.

Animals↗

PubMed2001

Orientation preference patterns in mammalian visual cortex: a wire length minimization approach.

In the visual cortex of many mammals, orientation preference changes smoothly along the cortical surface, with the exception of singularities such as pinwheels and fractures. The reason for the existence of these singularities has remained elusive, suggesting that they are developmental artifacts. We show that singularities reduce the length of intracortical neuronal connections for some connection rules. Therefore, pinwheels and fractures could be evolutionary adaptations keeping cortical volume to a minimum. Wire length minimization approach suggests that interspecies differences in orientation preference maps reflect differences in intracortical neuronal circuits, thus leading to experimentally testable predictions. We discuss application of our model to direction preference maps.

Animals↗

PubMed1999

Instantaneous postural stability characterization using time-frequency analysis.

Postural stability assessment is critical to a more accurate understanding of sway and balance control. The center of pressure (COP) metric has been shown to be a suitable output measure for time and frequency analysis. However, the center of pressure is a non-stationary signal. Standard time and frequency analysis methods may not be adequate for monitoring the dynamic changes in the center of pressure signal. In this study a time-frequency method, based on data-adaptive evolutionary spectral estimation, is applied to monitor the dynamic changes of the center of pressure in a non-stationary environment. Metrics including the instantaneous mean frequency (IMF), instantaneous spectral bandwidth (ISB), and instantaneous average power (IAP) are analyzed to characterize the center of pressure signal in both the anterior-posterior (AP) and the medial-lateral (ML) planes. Within the confines of this study, the IMF was found to be inversely proportional to IAP. The inverse proportionality factors were calculated in both eyes-open and eyes-closed trials during upright quiet standing. These findings suggest that the time-frequency analysis provides instantaneous metrics which describe the amplitude changes and frequency shift of the center of pressure under a variety of environmental conditions, thus providing a more reliable quantification of postural control.

Adult↗

PubMed2002

Plasticity of excitation-contraction coupling in fish cardiac myocytes.

Ultrastructure, molecular composition and electrophysiological properties of cardiac myocytes and functional characteristics of the fish heart suggest that cycling of extracellular Ca(2+) is generally more important than intracellular cycling of Ca(2+) stores of the sarcoplasmic reticulum (SR) in activating contraction of fish cardiac myocytes. This is especially true for the ventricle. However, prominent species-specific differences exist in cardiac excitation-contraction coupling and in the relative roles of extracellular and intracellular Ca(2+) sources among the teleostean fish. In fact, in some fish species (tunas, burbot) the SR of atrial myocytes, under certain circumstances, may act as the major source of systolic Ca(2+). These interspecific differences are obviously an outcome of evolutionary adaptation to different habitats and modes of activity in these habitats. There is also substantial intraspecific variation in the SR Ca(2+)-release-to-SL-Ca(2+) influx ratio depending on acute and chronic temperature changes. Consequently excitation-contraction coupling of the fish cardiac myocytes is not a fixed entity, but rather a highly variable and malleable process that enables fish to have an appropriate cardiac scope to exploit a diverse range of environments.

Acclimatization↗

PubMed2002

Intestinal microbial patterns of the common marmoset and rhesus macaque.

The intestinal microflora of common marmosets and rhesus monkeys were compared by enumerating bacteria from the small and large intestines. Rhesus monkeys had a consistent microflora pattern manifest by higher concentrations of total and Gram-negative aerobic and facultatively anaerobic bacteria, as well as aerobic and anaerobic Lactobacilli, in the large intestine as compared to the small intestine. In contrast, the marmoset microflora were considerably more variable. Approximately two-thirds of the marmosets (designated group A) had an overall profile that resembled the rhesus monkeys, but they had significantly higher concentrations of Gram-negative microflora in their large intestines than the rhesus monkeys. The remaining marmosets (group B) had higher concentrations of bacteria in the small intestine as compared to the large intestine, with the large intestinal concentrations being significantly lower than in the rhesus monkeys and group A marmosets. Moreover, the marmosets did not have detectable levels of aerobic Lactobacilli, and anaerobic Lactobacilli concentrations were significantly lower than in the rhesus macaques. Although it is unknown why microflora differ across species, it is likely that evolutionary adaptations in anatomy and functioning of the gastrointestinal tract influence the concentration and types of bacteria residing as the normal intestinal microflora.

Animals↗

PubMed2002

Comparison of the variable loop regions of myosin heavy chain genes from Antarctic and temperate isopods.

The evolutionary adaptations of functional genes to life at low temperatures are not well characterised in marine and fresh water invertebrates. Temperature has been shown to affect the functional characteristics of fish muscles, with changes in the velocity of shortening and ATPase activity being associated with myosin heavy chain (MyHC) isoform composition and the structure of the surface loop regions. Two PCR products spanning loops 1 and 2 of a MyHC gene from an Antarctic isopod (Glyptonotus antarcticus) were sequenced and compared with those of a temperate isopod (Idotea resecata), slow and fast fibres from lobster (Homarus gammarus) and a cold water amphipod (Eulimnogammarus verrucosus), revealing specific differences between the species, possibly related to fibre type and habitat temperature. The loop 2 region from G. antarcticus myosin was cloned and used for Northern analysis of total RNA from the other species. The cloned myosin cDNA hybridised specifically to a 6.6-kb transcript, in G. antarcticus muscle. In contrast, cDNA probes for lobster slow myosin and actin hybridised to muscle RNA from all species, demonstrating that a distinct MyHC isoform is expressed in the Antarctic isopod, as opposed to the temperate species. The inter- and intra-specific sequence differences in loop 2 region suggest that this may be a site for muscle adaptation to enable function at the low temperatures found in the Southern Ocean.

Actins↗

PubMed2002

Animal response to drastic changes in oxygen availability and physiological oxidative stress.

Oxygen is essential for most life forms, but it is also inherently toxic due to its biotransformation into reactive oxygen species (ROS). In fact, the development of many animal and plant pathological conditions, as well as natural aging, is associated with excessive ROS production and/or decreased antioxidant capacity. However, a number of animal species are able to tolerate, under natural conditions, situations posing a large potential for oxidative stress. Situations range from anoxia in fish, frogs and turtles, to severe hypoxia in organs of freeze-tolerant snakes, frogs and insect larvae, or diving seals and turtles, and mild hypoxia in organs of dehydrated frogs and toads or estivating snails. All situations are reminiscent of ischemia/reperfusion events that are highly damaging to most mammals and birds. This article reviews the responses of anoxia/hypoxia-tolerant animals when subjected to environmental and metabolic stresses leading to oxygen limitation. Abrupt changes in metabolic rate in ground squirrels arousing from hibernation, as well as snails arousing from estivation, may also set up a condition of increased ROS formation. Comparing the responses from these diverse animals, certain patterns emerge. The most commonly observed response is an enhancement of the antioxidant defense. The increase in the baseline activity of key antioxidant enzymes, as well as 'secondary' enzymatic defenses, and/or glutathione levels in preparation for a putative oxidative stressful situation arising from tissue reoxygenation seem to be the preferred evolutionary adaptation. Increasing the overall antioxidant capacity during anoxia/hypoxia is of relevance for species such as garter snakes (Thamnophis sirtalis parietalis) and wood fogs (Rana sylvatica), while diving freshwater turtles (Trachemys scripta elegans) appear to rely mainly upon high constitutive activities of antioxidant enzymes to deal with oxidative stress arising during tissue reoxygenation. The possibility that some animal species might control post-anoxic ROS generation cannot be excluded.

Adaptation, Physiological↗

PubMed2001

Dynamics of bacterial colonisation in the respiratory tract of patients with cystic fibrosis.

Mutations in the human genome may result in altered phenotypes. The cystic fibrosis (CF) patient, for instance, suffers from an aberrant composition of the epithelial lining of the gastrointestinal and respiratory tract. In this particular case, a single point mutation in the cystic fibrosis conductance regulator (CFTR) gene results in major physiological changes resulting in ecological changes that generate a niche particularly attractive to a selected set of microbial pathogens. We here present a review on the dynamics of the bacterial populations inhabiting the CF lung. Studies focusing on Staphylococcus aureus, Haemophilus influenzae and Pseudomonas aeruginosa will be summarised and discussed, whereas the technology used for microbial characterisation will be shortly highlighted. Emphasis, however, will be on those studies that assessed the genetic diversity among clinical isolates that were obtained over prolonged periods of time, enabling the distinction between persistent colonisation versus frequent re-infection by the selected pathogens. Evolutionary adaptation of pathogens to the CF lung is a common theme in many of these studies.

Bacteria↗

PubMed1999

Staying alive: evolution, culture, and women's intrasexual aggression.

Females' tendency to place a high value on protecting their own lives enhanced their reproductive success in the environment of evolutionary adaptation because infant survival depended more upon maternal than on paternal care and defence. The evolved mechanism by which the costs of aggression (and other forms of risk taking) are weighted more heavily for females may be a lower threshold for fear in situations which pose a direct threat of bodily injury. Females' concern with personal survival also has implications for sex differences in dominance hierarchies because the risks associated with hierarchy formation in nonbonded exogamous females are not offset by increased reproductive success. Hence among females, disputes do not carry implications for status with them as they do among males, but are chiefly connected with the acquisition and defence of scarce resources. Consequently, female competition is more likely to take the form of indirect aggression or low-level direct combat than among males. Under patriarchy, men have held the power to propagate images and attributions which are favourable to the continuance of their control. Women's aggression has been viewed as a gender-incongruent aberration or dismissed as evidence of irrationality. These cultural interpretations have "enhanced" evolutionarily based sex differences by a process of imposition which stigmatises the expression of aggression by females and causes women to offer exculpatory (rather than justificatory) accounts of their own aggression.

Aggression↗

PubMed1995

Protein L-isoaspartyl methyltransferase from the nematode Caenorhabditis elegans: genomic structure and substrate specificity.

We identified a protein L-isoaspartate (D-aspartate) O-methyltransferase (EC 2.1.1.77) in the nematode worm Caenorhabditis elegans. The methylation of abnormal L-isoaspartyl residues by this enzyme can lead to their conversion to L-aspartyl residues and represents a protein repair step for polypeptides damaged by spontaneous reactions during the aging process. We show that the levels of this enzyme increase 2-fold in C. elegans in the dauer larval form, a developmental stage where the organism can survive for extended periods of time. Utilizing degenerate oligonucleotide primers derived from conserved amino acid sequences of mammalian, plant, and bacterial L-isoaspartyl methyltransferases and PCR amplification, we made DNA probes that allowed us to obtain cDNA and genomic DNA clones encoding this enzyme in the nematode. The deduced amino acid sequence is 53% identical to the human enzyme and 29% identical to the Escherichia coli enzyme. Overexpression of the cDNA for the C. elegans enzyme in E. coli gave an active product with micromolar Km values for L-isoaspartyl-containing peptide substrates and for the methyl donor S-adenosyl-L-methionine. No methylation of D-aspartyl-containing peptides was detected under conditions where the human enzyme catalyzed this reaction, suggesting that the ability to methylate D-aspartyl residues in addition to L-isoaspartyl residues was a later evolutionary adaptation of this enzyme. The C. elegans gene for the methyltransferase, designated pcm-1, was mapped to a single site in a 31 kb region in the central portion of chromosome V. The gene is 3.2 kb in length and includes six introns. Although much smaller, its genomic organization is similar to that of the corresponding mouse gene, with identically positioned intron--exon splice junctions at five of seven sites. We propose that this gene plays an important role in facilitating the long term survival of this organisms.

Amino Acid Sequence↗

PubMed2004

Solution structure and backbone dynamics of the K18G/R82E Alicyclobacillus acidocaldarius thioredoxin mutant: a molecular analysis of its reduced thermal stability.

No general strategy for thermostability has been yet established, because the extra stability of thermophiles appears to be the sum of different cumulative stabilizing interactions. In addition, the increase of conformational rigidity observed in many thermophilic proteins, which in some cases disappears when mesophilic and thermophilic proteins are compared at their respective physiological temperatures, suggests that evolutionary adaptation tends to maintain corresponding states with respect to conformational flexibility. In this study, we accomplished a structural analysis of the K18G/R82E Alicyclobacillus acidocaldarius thioredoxin (BacTrx) mutant, which has reduced heat resistance with respect to the thermostable wild-type. Furthermore, we have also achieved a detailed study, carried out at 25, 45, and 65 degrees C, of the backbone dynamics of both the BacTrx and its K18G/R82E mutant. Our findings clearly indicate that the insertion of the two mutations causes a loss of energetically favorable long-range interactions and renders the secondary structure elements of the double mutants more similar to those of the mesophilic Escherichia coli thioredoxin. Moreover, protein dynamics analysis shows that at room temperature the BacTrx, as well as the double mutant, are globally as rigid as the mesophilic thioredoxins; differently, at 65 degrees C, which is in the optimal growth temperature range of A. acidocaldarius, the wild-type retains its rigidity while the double mutant is characterized by a large increase of the amplitude of the internal motions. Finally, our research interestingly shows that fast motions on the pico- to nanosecond time scale are not detrimental to protein stability and provide an entropic stabilization of the native state. This study further confirms that protein thermostability is reached through diverse stabilizing interactions, which have the key role to maintain the structural folding stable and functional at the working temperature.

Bacterial Proteins↗