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Results for “Evolutionary adaptability”

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At least 235 records · Page 13Linked to original sources

PubMed2006

Export pumps in Epulopiscium fishelsoni, the symbiotic giant gut bacterium in Acanthurus nigrofuscus.

Activity of the potential antixenobiotic efflux pumps of Epulopiscium fishelsoni (epulos), the symbiotic giant gut bacterium of the algivorous surgeonfish Acanthurus nigrofuscus, was studied in vivo using various specific substrates and microfluorometry. Kinetic and inhibitor analyses revealed the following vital efflux activities: (1) verapamil-sensitive efflux of amphiphilic cationic compounds rhodamine B, Hoechst 33342, and ethidium bromide; (2) verapamil-sensitive efflux of hydrophobic neutral fluorescein diacetate; (3) verapamil-insensitive efflux of hydrophilic anionic fluorescein; and (4) verapamil-insensitive efflux of glutathione-S-bimane. Cytosolic enzymes, nonspecific esterase and glutathione S-transferase, were shown to participate in xenobiotic metabolism. The results suggest that the activity of the potential efflux pump in epulos are similar to those described in other bacteria but are kinetically characterized by an unusually high transport rate, probably mediated by hyperplasia of the plasma membrane. Further studies of the export pumps in epulos may unmask their evolutionary adaptation to a xenobiotic-rich host gut content.

Animals↗

PubMed2006

First evidence of poisonous shrews with an envenomation apparatus.

Herein, we report evidence of an envenomation apparatus (EA) in two different species of extinct "giant" shrews, Beremendia and an indeterminate soricine (Mammalia, Eulipotyphla, Soricidae), documented by very well preserved fossil specimens recovered from two Early Pleistocene cave deposits of the Sierra de Atapuerca in Burgos, Spain. The two soricine taxa from Atapuerca have evolved specialized teeth as EAs, which differ from those of recently reported mammals of the Paleocene age, being more similar to the ones described in the modern Solenodon. This discovery reveals the first instance of shrews possessing what appears to be an EA, an evolutionary adaptation that, in these species, was probably related to an increase in body mass and hunting of a larger-sized prey. The Atapuerca specimens would have a highly specialized EA, one of the very few reported for an extinct or living mammal of any time. In addition to the presence of a gutter-like groove along the medial side of the crown of the lower incisors, these two species also present stout jaws and a modified mandibular symphysis with a conspicuous cavity, which in life would likely contain large amounts of connective tissue. The strong mandible architecture of these large shrews would be, in this way, reinforced by a more immovable symphysis, increasing the bite force exerted over a potential prey. This adaptation, together with the grooved incisors, would ensure a rapid and efficient transmission of the poisonous saliva to paralyze relatively large-sized prey.

Animals↗

PubMed2005

Gamma chain receptor interleukins: evidence for positive selection driving the evolution of cell-to-cell communicators in the mammalian immune system.

The interleukin-2 receptor (IL-2R) gamma chain, or common gamma chain (gammac), is the hub of a protein interaction network in the mammalia that is central to defense against disease. It is the indispensable subunit of the functional receptor complexes for a group of interleukins known as the gamma-chain-dependent interleukins (IL-2, IL-4, -7, -9, -15, and -21). The gammac links these proteins through their interaction with it and their competition for its recruitment. The gammac-dependent interleukins also interact with each other to either enhance or suppress expression through manipulation of expression of receptor subunits. Given the influence of protein-protein interactions on evolution, such as those documented for many genes including the reproductive proteins of the sperm and egg coat, here we have asked whether there is a common thread in the evolution of these interleukins. Our findings indicate that positive selection has acted by fixing a large number of amino acid replacement mutations in every single one of these interleukins, this adaptive evolution is also observed in a lineage-specific manner. Crucially, however, there does not appear to have ever been an instance of adaptive evolution in the gammac chain itself, thereby providing an insight into the evolution of this hub protein. These findings highlight the importance of adaptive evolutionary events in the evolution of this central network in the immune system and suggest underlying causes for differences in defense responses in the mammalia.

Animals↗

PubMed2004

Evolution and arrangement of the hsp70 gene cluster in two closely related species of the virilis group of Drosophila.

To investigate the genetic basis of differing thermotolerance in the closely related species Drosophila virilis and Drosophila lummei, which replace one another along a latitudinal cline, we characterized the hsp70 gene cluster in multiple strains of both species. In both species, all hsp70 copies cluster in a single chromosomal locus, 29C1, and each cluster includes two hsp70 genes arranged as an inverted pair, the ancestral condition. The total number of hsp70 copies is maximally seven in the more thermotolerant D. virilis and five in the less tolerant D. lummei, with some strains of each species exhibiting lower copy numbers. Thus, maximum hsp70 copy number corresponds to hsp70 mRNA and Hsp70 protein levels reported previously and the size of heat-induced puffs at 29C1. The nucleotide sequence and spacing of the hsp70 copies are consistent with tandem duplication of the hsp70 genes in a common ancestor of D. virilis and D. lummei followed by loss of hsp70 genes in D. lummei. These and other data for hsp70 in Drosophila suggest that evolutionary adaptation has repeatedly modified hsp70 copy number by several different genetic mechanisms.

Animals↗

PubMed2002

Output pathways of the mammalian suprachiasmatic nucleus: coding circadian time by transmitter selection and specific targeting.

Every day, we experience profound changes in our mental and physical condition as body and brain alternate between states of high activity during the waking day and rest during night-time sleep. The fundamental evolutionary adaptation to these profound daily changes in our physiological state is an endogenous 24-h clock. This biological clock enables us to prepare ourselves to these daily changes, instead of only being able to show a passive and delayed response. During the past decade, enormous progress has been made in determining possible molecular components of the biological clock. An important question remains, however, regarding how the rhythmic signal from the biological clock is spread throughout the body to control its physiology and behavior. Indeed, ultimately, the only raison d'etre for the biological clock is its output (Green 1998). In the present review, we propose that the main mechanism for the spreading time-of-day information throughout the body consists of different circadian waves of suprachiasmatic nucleus (SCN) transmitter release, directed to a restricted number of specific SCN target areas, and affecting both neuroendocrine mechanisms and the peripheral autonomic nervous system.

Animals↗

PubMed2000

Immunocytochemical localization and secretion process of the toxin CSTX-1 in the venom gland of the wandering spider Cupiennius salei (Araneae: Ctenidae).

Fluorescein and horseradish peroxidase-labeled monoclonal antibodies were used to localize the predominant toxic peptide CSTX-1 in the venom gland of the spider Cupiennius salei. There was no polarity of CSTX-1 expression in repleted glands, whereas the glands of previously milked spiders showed a decreasing immunofluorescent response from the distal to the proximal portion. Detailed investigation revealed a new structure in the venom-secreting epithelium, which is postulated to be an evolutionary adaptation to increasing gland volume. CSTX-1 was found to be synthesized and stored as a fully active toxin within complex units, composed of long interdigitating cells running perpendicular to the muscular sheath and extending into the central lumen of the gland. These venom-producing units were found in all sectors of the gland, including the transitional region between the main gland and the venom duct. The venom is liberated from the venom-producing units into the glandular lumen following the contraction of the surrounding muscle layer. Free nuclei or other cellular fragments, which would have provided evidence for a holocrine secretion process, were not found in the glandular lumen or in the crude venom obtained by electrical stimulation. The fine regulation of the spider's venom injection process is postulated to be the function of the bulbous ampulla, situated in the anterior third of the venom duct.

Adaptation, Physiological↗

PubMed2003

Plasma insulin-like growth factor-I, testosterone and morphological changes in the growth of captive agile gibbons ( Hylobates agilis) from birth to adolescence.

We examined growth changes in concentrations of plasma insulin-like growth factor-1 (IGF-1) and testosterone, and somatometric parameters in two captive male agile gibbons from birth to about 4 years of age, to examine the evolution of growth patterns in primates. Plasma IGF-1 concentrations in agile gibbons generally increased with age with values ranging from 200 to 1100 ng/ml. The growth profiles in plasma IGF-1 in the gibbons were similar to those reported for chimpanzees. The highest concentrations of plasma testosterone (230 and 296 ng/dl) were observed within the first 0.3 years from birth, then the concentrations rapidly decreased and fluctuated below 100 ng/dl. Continuously higher IGF-1 concentrations were observed after 2.6 and 3.5 years of age. The profiles of plasma testosterone in these gibbons also resembled those of other primates including humans. However, their plasma testosterone levels in both neonate and adult stages (60 ng/dl) were lower than those reported for macaques and chimpanzees of respective stages. The obtained growth profiles of plasma IGF-1 and testosterone suggest that the adolescent phase starts around 2.6 or 3.5 years of age in male agile gibbons. The growth trend in many morphological parameters including body weight showed a linear increase without a significant growth spurt at approximately the onset of puberty. Head length and first digit length had reached a plateau during the study period. Brachial index, which indicates the relative length of forearm to upper arm, significantly increased gradually through the growth period. This result indicates that forearm becomes relatively longer than the upper arm with growth, which may be an evolutionary adaptation for brachiation.

Adaptation, Physiological↗

PubMed2006

Microbial diversity in natural environments: focusing on fundamental questions.

Interactions with Gijs Kuenen and other Dutch scientists have led my lab to fundamental insights into the composition, structure and function of a hot spring cyanobacterial mat community that should influence our thinking about all microbial communities. By focusing on the distribution of molecular sequence variants of predominant mat phototrophs, we have discovered that small-scale sequence variation can be ecologically meaningful. By applying novel cultivation approaches, we have been able to obtain genetically relevant community members and thus to test the hypothesis that closely related sequence variants arose via adaptive evolutionary radiation. By applying the analytical tools of organic geochemistry we have gained insight into the metabolisms of major phototrophic members of the mat community as well as interactions between phototrophic guilds. These observations challenge traditional paradigms about prokaryotic species and cause us to consider evolutionary ecology theory as we develop genome-based methods for high-resolution analysis of the species-like fundamental units comprising microbial communities, and for investigating how such units coordinate the physiological activities within guilds of the community.

Autotrophic Processes↗

PubMed2026

Nipah virus in the era of global connectivity: molecular evolution, transmission risk, and preparedness strategies.

Nipah virus (NiV) is a highly pathogenic zoonotic RNA virus belonging to the genus Henipavirus within the family Paramyxoviridae, representing a continuing global health concern due to its high case fatality rate and potential for epidemic expansion in the era of increasing international connectivity. The virus demonstrates strong evolutionary adaptability driven by the absence of proofreading mechanisms during RNA replication, enabling genetic diversification that may influence host range, virulence, and transmission dynamics. Molecular pathogenesis of NiV is primarily mediated through interaction of viral glycoproteins with ephrin-B2 and ephrin-B3 receptors, facilitating host cell entry, endothelial damage, and neuroinvasion. Immune evasion facilitated by the action of accessory proteins encoded by the P gene (P, V, W, and C) acts to suppress innate antiviral immunity through the inhibition of interferon induction and JAK/STAT signaling. Human-to-human transmission of Nipah virus remains limited, with epidemiological evidence indicating basic reproduction numbers generally below unity; however, respiratory involvement and healthcare-associated exposure may enhance cluster outbreaks. Global travel, ecological disruption, and fragmented surveillance systems contribute to spillover risk, particularly in South and Southeast Asia where fruit bats of the genus Pteropus serve as natural reservoirs. Despite advances in vaccine technology, including subunit, viral vector, mRNA-based platforms, and monoclonal antibody therapies, no licensed prophylactic or therapeutic agent is currently available for human use. Global preparedness remains challenged by the scarcity of high-containment biosafety facilities, limited research funding, and absence of integrated One Health surveillance networks. Ethical considerations surrounding wildlife population control further complicate disease mitigation strategies. Emerging genomic surveillance, artificial intelligence-assisted predictive modeling, and regional data-sharing frameworks are essential for early detection and response. Strengthening molecular research on viral-host interactions and transmission determinants will be critical for preventing future Nipah virus outbreaks in an increasingly interconnected world.

Genomic surveillance↗

PubMed1976

Homology of the giant serotonergic neurons (metacerebral cells) in Aplysia and pulmonate molluscs.

The properties of the giant cerebral serotonin-containing neurons of the opisthobranch mollusc Aplysia californica were studied and were compared to the existing data on the giant serotonin-containing neurons (metacerebral cells) of pulmonate mulluscs. Among the properties examined were: axonal distribution, synaptic input and output, pharmacological responses, biophysical characteristics, and plasticity. With only minor exceptions, the properties of the serotonin-containing neurons of Aplysia and of pulmonate molluscs were remarkably similar, and it was concluded that these identified neurons are true homologues. The establishment of the homology of the metacerebral cells of Aplysia to the metacerebral cells of pulmonate molluscs extends the known distribution of these neurons to a second major subclass (Opisthobranchiata) of molluscs. Since pulmonate and opisthobranch molluscs differ substantially in behavioral and anatomical features, the study of the metacerebral cells of these two groups may promote the understanding of the evolutionary adaptation of the nervous system to different environmental pressures.

Acetylcholine↗

PubMed1993

Classification of fumarate reductases and succinate dehydrogenases based upon their contrasting behaviour in the reduced benzylviologen/fumarate assay.

Reduction of fumarate by soluble beef heart succinate dehydrogenase has been shown previously by voltammetry to become increasingly retarded as the potential is lowered below a threshold potential of -80 mV at pH 7.5. The behaviour resembles that of a tunnel diode, an electronic device exhibiting the property of negative resistance. The enzyme thus acts to oppose fumarate reduction under conditions of high thermodynamic driving force. We now provide independent evidence for this phenomenon from spectrophotometric kinetic assays. With reduced benzylviologen as electron donor, we have studied the reduction of fumarate catalysed by various enzymes classified either as succinate dehydrogenases or fumarate reductases. For succinate dehydrogenases, the rate increases as the concentration of reduced dye (driving force) decreases during the reaction. In contrast, authentic fumarate reductases of anaerobic cells (and 'succinate dehydrogenase' from Bacillus subtilis) neither exhibit the electrochemical effect nor deviate from simple kinetic behaviour in the cuvette assay. The 'tunnel-diode' effect may thus represent an evolutionary adaptation to aerobic metabolism.

Animals↗

PubMed1995

The arrestin superfamily: cone arrestins are a fourth family.

Arrestins constitute a superfamily of regulatory proteins that down-regulate phosphorylated G-protein membrane receptors, including rod and cone photoreceptors and adrenergic receptors. The potential role of arrestin in color visual processes led us to identify a cDNA encoding a cone-like arrestin in Xenopus laevis, the principle amphibian biological model system. Alignment of 18 deduced amino acid sequences of all known arrestins from both invertebrate and vertebrate species reveals five arrestin families. Further analysis identifies 7 variable and 4 conservative arrestin structural motifs that may identify potential functional domains. The adaptive evolutionary relationship of Xenopus cone arrestin to the arrestin gene tree suggests high intrafamily homology and early gene duplication events.

Amino Acid Sequence↗

PubMed1996

A study of sleep in the European blackbird.

Sleep states in the blackbird, Turdus merula, were determined by recording the electroencephalogram (EEG), electrooculogram (EOG), electromyogram (EMG), and heart rate (HR), and from behavioral observations and responses to auditory stimulation by natural calls. The presence of changes in slow wave activity was determined from the power spectra of the EEG. Spectral power density in the 0.5-4.0 Hz band during slow wave sleep (SWS) attained highest values in the first part of the night, then declined. This trend in EEG spectra, which occurred across the night, probably reflects a homeostatic process strikingly similar to that observed in mammals. The reactivity to natural calls during SWS episodes also decreased across the night. Episodes of interhemispheric EEG asymmetry, which typically lasted from 2 to 4 s, occurred when birds displayed the front sleep posture and they constituted 140-200 s of each night. Unihemispheric sleep episodes probably result from unilateral activation of the visual system, and they could be considered as an evolutionary adaptation. HR was highest in wakefulness and lower in sleep but, due to large variability, reliable discrimination between sleep and wakefulness could not be made. Comparison of the blackbird's behavior during 4 different nights revealed a strong effect of the first night on sleeping behavior. A significant reduction in back sleep posture occurred during the baseline night, when lead wires were connected.

Animals↗

PubMedDate not supplied

Concerning the role of 24,25-dihydrolanosterol and lanostanol in sterol biosynthesis by cultured cells.

Rat hepatoma cells (H4-II-E-C3) efficiently converted a dietary supplement of [2-3H]24,25-dihydrolanosterol (1) to [3H]cholesterol while [2-3H]lanostanol (4,4,14 alpha-trimethylcholestanol (2) was recovered from the cells without apparent transformation, although it was esterified and induced an accumulation of lanosterol. A comparison of the chromatographic (TLC, GLC and HPLC), spectral (MS and 1H-NMR) and physical properties of 1 and 2 is given for the first time. The inability to detect 2 in nature coupled with our findings that 1 but not 2 is metabolized to cholesterol by H4 cells is interpreted to imply that the biosynthetic inclusion of the delta 8(9)-bond during the cyclization process of squalene-oxide to a tetracyclic product is an evolutionary adaptation selected for because the olefinic linkage is structually important in the subsequent conversion of lanosterol and its stereoisomers, e.g., cycloartenol, to delta 5-sterols.

Animals↗

PubMedDate not supplied

Anterior chamber associated immune deviation: the privilege of immunity in the eye.

Immune privilege in the anterior chamber of the eye, no longer considered a laboratory curiosity, results from an active, if deviant, systemic immune response. The specific features of this response, termed Anterior Chamber Associated Immune Deviation (ACAID) include (a) suppressed delayed hypersensitivity, (b) preserved humoral immunity, and (c) primed cytotoxic T cell responses. Induction of ACAID by intraocular antigens depends upon unique characteristics of the anterior segment of the eye and of the spleen. Evidence from animal models is presented in support of the contention that ACAID is an evolutionary adaptation of the immune response designed to provide those types of immune protection for the eye that interfere with vision as little as possible. ACAID may also have been created for the purpose of avoiding harmful immune responses (autoimmune diseases) to unique molecules of the eye (such as retinal S antigen), which the immune system never learns to regard as "Self." Because of this adaptation, the eye and the host are vulnerable to those pathogens whose elimination is dependent upon delayed hypersensitivity, such as malignant tumors and herpes simplex virus-1. As we come to understand the cellular and molecular mechanisms responsible for ACAID, a new generation of therapeutic strategies may be envisioned for certain eye diseases which are now of enigmatic cause and submit poorly to conventional therapy.

Animals↗

PubMed1989

Ontogeny of the lymphoid organs in an Antarctic teleost, Harpagifer antarcticus (Notothenioidei: Perciformes).

The effect of an evolutionary adaptation to low environmental temperature on the development of lymphoid organs was examined in Harpagifer antarcticus from Signy Island (South Orkney Islands; 60 degrees 43'S, 45 degrees 38'W). Thymus, pronephric kidney and spleen were typical, both in position and structural development, of those observed in warmer-water teleosts. The pronephric kidney was the first organ to be infiltrated by leucocytes, at 1 h post-hatch, though the infiltration of the thymic epithelia and the development of the splenic anlage were not observed until 4 weeks post-hatch. Full development of the lymphoid organs was not achieved until the juvenile stage. Although an increased infiltration of the thymus, by subepithelial connective tissues and epithelial mucous cells, occurred in the juvenile and adult stages, there was no evidence of an advanced stage of thymic regression or involution in the adult Harpagifer. Thus, a suppressive influence of the low temperature environment, on the onset and degree of lymphoid organ development and thymic involution, was indicated in this species.

Acclimatization↗

PubMed1991

Regulation of MHC expression.

The level of expression of class I and class II MHC antigens in any particular cell is not a fixed characteristic, but is subject to wide fluctuation. The "resting" level of expression varies widely in different cell types, e.g., the cells of the exocrine pancreas and the myocardial cell express neither class I nor class II MHC antigens, whereas B lymphocytes express high levels of both class I and class II. The factors regulating these resting levels are beginning to be elucidated at the DNA level. The resting levels of class I and class II MHC antigen expression can be very greatly increased, primarily as a consequence of exposure to various cytokines released during inflammatory responses, but also in response to other non-specific stimuli. This probably represents an evolutionary adaptation to increase the capacity of infected tissues to present foreign peptides to the immune system, and thereby favour the survival of the host. However, when this phenomenon occurs in a transplanted organ, the increased expression of the now foreign MHC antigens in the context of the new host very likely plays a role in the graft's own destruction. The increased expression of class I MHC antigens, especially if the cell does not express these antigens at all at the time of grafting, will very likely render the cell susceptible to CD8+ cytotoxic T lymphocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Starlings as herbalists: countering parasites and pathogens.

The avian nest protection hypothesis explains the widespread behavior of incorporating fresh green plant material into an otherwise dry nest matrix as an evolutionary adaptation. Species that exhibit this behavior tend to breed in previously inhabited nest sites and experience high ectoparasite and pathogen loads. Metabolites in the green plants control parasite and pathogen populations and decrease the effects of these agents on nestlings. The choice of plants is not arbitrary. In the case of European starlings, a nonrandom subset of available vegetation is selected, and it is these plants that have the largest impact on ectoparasite and pathogen populations. Experimental and observational evidence suggests that starlings select plants on the basis of chemosensory cues.

Journal Article↗