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PubMed1999

Dissociation between sensitization and learning-related neuromodulation in an aplysiid species.

Previous phylogenetic analyses of learning and memory in an opisthobranch lineage uncovered a correlation between two learning-related neuromodulatory traits and their associated behavioral phenotypes. In particular, serotonin-induced increases in sensory neuron spike duration and excitability, which are thought to underlie several facilitatory forms of learning in Aplysia, appear to have been lost over the course of evolution in a distantly related aplysiid, Dolabrifera dolabrifera. This deficit is paralleled by a behavioral deficit: individuals of Dolabrifera do not express generalized sensitization (reflex enhancement of an unhabituated response after a noxious stimulus is applied outside of the reflex receptive field) or dishabituation (reflex enhancement of a habituated reflex). The goal of the present study was to confirm and extend this correlation by testing for the neuromodulatory traits and generalized sensitization in an additional species, Phyllaplysia taylori, which is closely related to Dolabrifera. Instead, our results indicated a lack of correlation between the neuromodulatory and behavioral phenotypes. In particular, sensory neuron homologues in Phyllaplysia showed the ancestral neuromodulatory phenotype typified by Aplysia. Bath-applied 10 microM serotonin significantly increased homologue spike duration and excitability. However, when trained with the identical apparatus and protocols that produced generalized sensitization in Aplysia, individuals of Phyllaplysia showed no evidence of sensitization. Thus, this species expresses the neuromodulatory phenotype of its ancestors while appearing to express the behavioral phenotype of its near relative. These results suggests that generalized sensitization can be lost during the course of evolution in the absence of a deficit in these two neuromodulatory traits, and raises the possibility that the two traits may support some other form of behavioral plasticity in Phyllaplysia. The results also raise the question of the mechanistic basis of the behavioral deficit in Phyllaplysia.

Action Potentials↗
PubMed2002

Genetic variability in hepatitis B viruses.

In 1988, it was reported that the full nucleotide sequences of 18 hepatitis B virus (HBV) strains clustered into four genetic groups (A to D) with more than 8% divergence between the groups. This classification of strains in terms of genome sequence has since proven to be an important tool in the understanding of HBV epidemiology and evolution and has been expanded to include three more genotypes. In parallel with the HBV genotypes described in humans, HBV strains isolated from different primates and hepadnaviruses found in woodchucks, ground squirrels, ducks and herons have been studied. Sequence differences between HBV genotypes can lead to structural differences at the level of the pregenome and can also lead to dramatic differences at the translational level when specific and commonly occurring mutations occur. There is increasing evidence that the clinical picture, the response to treatment and the long-term prognosis may differ depending on which genotype has infected the patient. The consideration of traditional serological patterns in a patient must therefore take the genotype of the infecting strain into account. Nucleotide variability between HBV strains has been used in several studies to trace routes of transmission and, since it is becoming increasingly clear that the differences between HBV genotypes are important, the need for reliable and easy methods of differentiating HBV genotypes has arisen. This review summarizes the knowledge of HBV genotypes with regard to their genetic, structural and clinically significant differences and their origin and evolution in the context of the hepadnaviruses in general.

Animals↗
PubMed2001

Mechanisms causing rapid and parallel losses of ribose catabolism in evolving populations of Escherichia coli B.

Twelve populations of Escherichia coli B all lost D-ribose catabolic function during 2,000 generations of evolution in glucose minimal medium. We sought to identify the population genetic processes and molecular genetic events that caused these rapid and parallel losses. Seven independent Rbs(-) mutants were isolated, and their competitive fitnesses were measured relative to that of their Rbs(+) progenitor. These Rbs(-) mutants were all about 1 to 2% more fit than the progenitor. A fluctuation test revealed an unusually high rate, about 5 x 10(-5) per cell generation, of mutation from Rbs(+) to Rbs(-), which contributed to rapid fixation. At the molecular level, the loss of ribose catabolic function involved the deletion of part or all of the ribose operon (rbs genes). The physical extent of the deletion varied between mutants, but each deletion was associated with an IS150 element located immediately upstream of the rbs operon. The deletions apparently involved transposition into various locations within the rbs operon; recombination between the new IS150 copy and the one upstream of the rbs operon then led to the deletion of the intervening sequence. To confirm that the beneficial fitness effect was caused by deletion of the rbs operon (and not some undetected mutation elsewhere), we used P1 transduction to restore the functional rbs operon to two Rbs(-) mutants, and we constructed another Rbs(-) strain by gene replacement with a deletion not involving IS150. All three of these new constructs confirmed that Rbs(-) mutants have a competitive advantage relative to their Rbs(+) counterparts in glucose minimal medium. The rapid and parallel evolutionary losses of ribose catabolic function thus involved both (i) an unusually high mutation rate, such that Rbs(-) mutants appeared repeatedly in all populations, and (ii) a selective advantage in glucose minimal medium that drove these mutants to fixation.

Adaptation, Physiological↗
PubMed2006

Reducing the cost of resistance; experimental evolution in the filamentous fungus Aspergillus nidulans.

We have studied compensatory evolution in a fludioxonil resistant mutant of the filamentous fungus Aspergillus nidulans. In an evolution experiment lasting for 27 weeks (about 3000 cell cycles) 35 parallel strains of this mutant evolved in three different environmental conditions. Our results show a severe cost of resistance (56%) in the absence of fludioxonil and in all conditions the mutant strain was able to restore fitness without loss of the resistance. In several cases, the evolved strain reached a higher fitness than the original sensitive ancestor. Fitness compensation occurred in one, two or three discrete steps. Genetic analysis of crosses between different evolved strains and between evolved and ancestral strains revealed interaction between compensatory mutations and provided information on the number of loci involved in fitness compensation. In addition, we discuss the opportunities for the experimental study of evolutionary processes provided by the filamentous fungus A. nidulans.

Aspergillus nidulans↗
PubMed1991

Comparative aspects of the distribution of substance P and dopamine immunoreactivity in the substantia nigra of amniotes.

In the present account, the relation between the descending, substance P (SP)-containing projection fibers from the striatum and the dopaminergic cell bodies in the midbrain tegmentum was investigated in several species of reptiles and the domestic chicken by means of antisera against SP and dopamine. It was found that in all species studied an almost complete match of the SP and the dopamine immunoreactivity occurs in the ventral tegmental area. In contrast, considerable differences were observed in the substantia nigra and the retrorubral area. Two different patterns were recognized: one pattern in which there is little overlap between the dopaminergic cells and SP fibers (lizards, turtles) and another with an extensive overlap (snakes, chickens). Similar patterns were found in mammalian species. On the basis of an out-group comparison with anamniotes, it is suggested that the pattern with little overlap represents the primitive character. The pattern with considerable overlap, found in the three classes of amniotes, should be considered an independent development from the same primitive character and should, therefore, be defined as an example of parallel homoplasy.

Animals↗
PubMed2005

Evolution of temporal order in living organisms.

Circadian clocks are believed to have evolved in parallel with the geological history of the earth, and have since been fine-tuned under selection pressures imposed by cyclic factors in the environment. These clocks regulate a wide variety of behavioral and metabolic processes in many life forms. They enhance the fitness of organisms by improving their ability to efficiently anticipate periodic events in their external environments, especially periodic changes in light, temperature and humidity. Circadian clocks provide fitness advantage even to organisms living under constant conditions, such as those prevailing in the depth of oceans or in subterranean caves, perhaps by coordinating several metabolic processes in the internal milieu. Although the issue of adaptive significance of circadian rhythms has always remained central to circadian biology research, it has never been subjected to systematic and rigorous empirical validation. A few studies carried out on free-living animals under field conditions and simulated periodic and aperiodic conditions of the laboratory suggest that circadian rhythms are of adaptive value to their owners. However, most of these studies suffer from a number of drawbacks such as lack of population-level replication, lack of true controls and lack of adequate control on the genetic composition of the populations, which in many ways limits the potential insights gained from the studies. The present review is an effort to critically discuss studies that directly or indirectly touch upon the issue of adaptive significance of circadian rhythms and highlight some shortcomings that should be avoided while designing future experiments.

Journal Article↗
PubMed1987

Repetition as the essence of life on this earth: music and genes.

In prebiotic nucleic acid replication, templates appear to have been in short supply. A single round of tandem duplication of existing oligomers assured progressive extension of templates to the length adequate for encoding of polypeptide chains. Thus, the first set of coding sequences had to be repeats of base oligomers encoding polypeptide chains of various periodicities. On one hand, the readiness of these periodical polypeptide chains to assume alpha-helical and/or beta-sheet secondary structures contributed to the extremely rapid initial functional diversification of these polypeptide chains. It would be recalled that most, if not all, of the sugar-metabolizing enzymes had already achieved the inviolable functional competence before the division of prokaryotes from eukaryotes. On the other hand, a certain (dipeptidic?) of the peptidic periodicities was apparently chosen as the timekeeping unit by the biological clock. Musical compositions too apparently evolved originally as a timekeeping device. Accordingly, repetitiousness is evident in all musical compositions. Evolution of musical compositions from the early Baroque to the late Romantic parallels that of coding sequences from rather exact repeats of base oligomers to more complex modern coding sequences in which repetitious elements are less conspicuous and more varied. Inasmuch as the earth is governed by the hierarchy of periodicities (days, months and years), such reliance on periodicities is rather expected.

Amino Acid Sequence↗
PubMed2006

Amplification of DNA from preserved specimens shows blowflies were preadapted for the rapid evolution of insecticide resistance.

Mutations of esterase 3 confer two forms of organophosphate resistance on contemporary Australasian Lucilia cuprina. One form, called diazinon resistance, is slightly more effective against commonly used insecticides and is now more prevalent than the other form, called malathion resistance. We report here that the single amino acid replacement associated with diazinon resistance and two replacements associated with malathion resistance also occur in esterase 3 in the sibling species Lucilia sericata, suggesting convergent evolution around a finite set of resistance options. We also find parallels between the species in the geographic distributions of the polymorphisms: In both cases, the diazinon-resistance change is absent or rare outside Australasia where insecticide pressure is lower, whereas the changes associated with malathion resistance are widespread. Furthermore, PCR analysis of pinned specimens of Australasian L. cuprina collected before the release of organophosphate insecticides reveals no cases of the diazinon-resistance change but several cases of those associated with malathion resistance. Thus, the early outbreak of resistance in this species can be explained by the preexistence of mutant alleles encoding malathion resistance. The pinned specimen analysis also shows much higher genetic diversity at the locus before organophosphate use, suggesting that the subsequent sweep of diazinon resistance in Australasia has compromised the scope for the locus to respond further to the ongoing challenge of the insecticides.

Adaptation, Physiological↗
PubMed2004

Parallel radiations in the primary clades of birds.

Knowledge of avian phylogeny is prerequisite to understanding the circumstances and timing of the diversification of birds and the evolution of morphological, behavioral, and life-history traits. Recent molecular datasets have helped to elucidate the three most basal clades in the tree of living birds, but relationships among neoavian orders (the vast majority of birds) remain frustratingly vexing. Here, we examine intron 7 of the beta-fibrinogen gene in the most taxonomically inclusive survey of DNA sequences of nonpasserine bird families and orders to date. These data suggest that Neoaves consist of two sister clades with ecological parallelisms comparable to those found between marsupial and placental mammals. Some members of the putative respective clades have long been recognized as examples of convergent evolution, but it was not appreciated that they might be parts of diverse parallel radiations. In contrast, some traditional orders of birds are suggested by these data to be polyphyletic, with representative families in both radiations.

Animals↗
PubMed1997

Phylogenetic survey of endomannosidase indicates late evolutionary appearance of this N-linked oligosaccharide processing enzyme.

Endo-alpha-D-mannosidase is a processing enzyme which in contrast to other glycosidases involved in the trimming of N-linked oligosaccharides of glycoproteins acts at an internal position by cleaving the linkage between the glucose-substituted mannose and the internal portion of the polymannose unit and thereby provides an alternate deglucosylating pathway. In order to evaluate at what stage in evolution this unusual enzyme first emerged, we have carried out a phylogenetic survey of its distribution among a broad group of eukaryotes ranging from unicellular organisms to highly developed animals and plants, all of which are known to have the capacity to N-glycosylate proteins and subsequently trim the nascent glucosylated polymannose oligosaccharides. It became evident from enzyme assays and in vivo studies that endomannosidase is limited in its distribution to members of the chordate phylum, including placental and marsupial mammals, birds, reptiles, amphibians, and fish, with the single except of the Mollusca in which it was detected in three distinct classes. The enzyme's absence in all other invertebrates examined as well as in yeast, various protozoa and higher plants, stands in contrast to glucosidase II and alpha 1,2-mannosidase which were found to be present in all eukaryotes studied. The observation that endomannosidase activity was not present in insects was confirmed by radiolabeling experiments with Sf9 cells in culture. These cells, which are widely employed for the expression of mammalian genes, were in distinction to mouse cells unable to circumvent a castanospermine (CST)-induced glucosidase blockade. Moreover we observed that Tetrahymenae, which synthesize glycoproteins with truncated N-linked oligosaccharides, could not process these beyond the Glc3Man5GlcNAc2 stage in the presence of CST. The late appearance of endomannosidase during evolution suggests a need for an alternate deglucosylation route in higher animals which parallels the development of elaborate complex N-linked oligosaccharides. Such carbohydrate units are believed to carry out vital biological functions and deglucosylation is a prerequisite to the further processing steps required for their formation.

Animals↗
PubMed2004

Development and evaluation of an online CO(2) evolution test and a multicomponent biodegradation test system.

Well-established biodegradation tests use biogenously evolved carbon dioxide (CO(2)) as an analytical parameter to determine the ultimate biodegradability of substances. A newly developed analytical technique based on the continuous online measurement of conductivity showed its suitability over other techniques. It could be demonstrated that the method met all criteria of established biodegradation tests, gave continuous biodegradation curves, and was more reliable than other tests. In parallel experiments, only small variations in the biodegradation pattern occurred. When comparing the new online CO(2) method with existing CO(2) evolution tests, growth rates and lag periods were similar and only the final degree of biodegradation of aniline was slightly lower. A further test development was the unification and parallel measurement of all three important summary parameters for biodegradation--i.e., CO(2) evolution, determination of the biochemical oxygen demand (BOD), and removal of dissolved organic carbon (DOC)--in a multicomponent biodegradation test system (MCBTS). The practicability of this test method was demonstrated with aniline. This test system had advantages for poorly water-soluble and highly volatile compounds and allowed the determination of the carbon fraction integrated into biomass (heterotrophic yield). The integrated online measurements of CO(2) and BOD systems produced continuous degradation curves, which better met the stringent criteria of ready biodegradability (60% biodegradation in a 10-day window). Furthermore the data could be used to calculate maximal growth rates for the modeling of biodegradation processes.

Aniline Compounds↗
PubMed2006

Spatial heterogeneity, predator cognition, and the evolution of color polymorphism in virtual prey.

Cryptically colored prey species are often polymorphic, occurring in multiple distinctive pattern variants. Visual predators promote such phenotypic variation through apostatic selection, in which they attack more abundant prey types disproportionately often. In heterogeneous environments, disruptive selection to match the coloration of disparate habitat patches could also produce polymorphism, but how apostatic and disruptive selection interact in these circumstances is unknown. Here we report the first controlled selection experiment on the evolution of prey coloration on heterogeneous backgrounds, in which blue jays (Cyanocitta cristata) searched for digital moths on mixtures of dark and light patches at three different scales of heterogeneity. As predicted by ecological theory, coarse-grained backgrounds produced a functional dimorphism of specialists on the two patch types; fine-grained backgrounds produced generalists. The searching strategies of the jays also varied with the habitat configuration, however. Complex backgrounds with many moth-like features elicited a slow, serial search that depended heavily on selective attention. The result was increased apostatic selection, producing a broad range of moth phenotypes. Backgrounds with larger, more uniform patches allowed the birds to focus on the currently most rewarding patch type and to search entire patches rapidly in parallel. The result was less apostatic selection and lower phenotypic variability. The evolution of polymorphism in camouflaged prey depends on a complex interaction between habitat structure and predator cognition.

Animals↗
PubMed1996

Sex-biased heteroplasmy and mitochondrial DNA inheritance in the mussel Mytilus galloprovincialis Lmk.

An exceptional mode of mtDNA inheritance involving separate maternal and paternal transmission routes has been reported recently in the mussel Mytilus edulis. This mode of inheritance provides an explanation for the high levels of heteroplasmy for two highly diverged genomes observed in males of this species. Here we provide evidence for a similar pattern of heteroplasmy in Atlantic and Mediterranean forms of the related mussel M. galloprovincialis. The results support the hypothesis that this mode of mtDNA inheritance has an ancient origin. In addition, the detection of some heteroplasmic females suggests preferential, rather than exclusive, transmission within male and female lines of descent. We also present evidence that the two highly diverged genomes display a parallel split between the Atlantic and Mediterranean forms, consistent with neutral evolution.

Animals↗
PubMed2004

Assessment of disease progression in parkinsonism.

In this brief article, we report preliminary results from an NIH-funded project to use functional brain imaging to study the natural history of neurodegeneration during the earliest clinical stages of PD. We used positron emission tomography (PET) to measure DAT binding (18F-FPCIT), resting glucose metabolism (18FFDG), and brain activation (H215O) responses in 20 newly diagnosed PD patients. The longitudinal study is being conducted at three time points for each measurement during a 5-year period. The interim results indicate the evolution of abnormal metabolic brain networks and activation responses occurring in parallel with presynaptic nigrostriatal dopamine dysfunction in early PD.

Aged↗
PubMed1978

Are chromosomal axial struc-ures and microtubular systems phylogenetic markers in the dinoflagellates?

Two new events concerning nuclear division and chromosomal predivision are described in the free-living marine dinoflagellate Prorocentrum micans E. considered by Loeblich (1976) as a primitive form. These events will be discussed in relation to the evolution of Dinoflagellates. (1) Presence of a paranuclear bundle of microtubules parallel to the extranuclear bundle passing through the dividing nucleus (Soyer, 1975, 1977b) and (2) Presence of a chromosomal axis in the predividing chromosomes (Soyer, 1977c).

Animals↗
PubMed2000

Implantable cardioverter defibrillator-an unusual case of inappropriate discharge during showering.

The evolution of diagnostic information provided in implantable cardioverter defibrillators (ICDs) has paralleled the advances in the therapeutic options incorporated in these systems. Contemporary devices are capable of providing recordings of electrical events surrounding all delivered and aborted device therapy. This report presents un unusual case of inappropriate discharge of an ICD, resulting from electromagnetic interference. A transvenous ICD system (Sentry Hot Can 4310 HC, Telectronics Denver, CO), was implanted in a patient with ischemic heart disease due to episodes of ventricular tachycardia refractory to antiarrhythmic treatment. One month post-implant the patient reported two consecutive shocks from the device while showering. The non-physiological cycle length (100 ms) recorded in conjunction to the scenario of the event, raised the suspicion of electromagnetic interference through electrical current leakage in the bathroom, an hypothesis that was subsequently proved. This case report underscores that electromagnetic interference can become hazardous in common daily activities of patients with an ICD.

Aged↗
PubMed2005

Oncolytic virotherapy: approaches to tumor targeting and enhancing antitumor effects.

The application of replicating viruses for the treatment of cancers represents a novel therapy that is distinct from traditional treatment modalities. It is apparent that the genetic changes that a virus produces within an infected cell in order to create an environment conducive to viral replication are often similar to the processes involved in cellular transformation. These include uncontrolled cellular proliferation, prevention of apoptosis, and resistance to host organism immune effector mechanisms. Deletions of viral genes involved in these processes have been exploited to produce viral mutants whose replication is selective for transformed cells. The use of tissue-specific transcriptional response or RNA stability elements to control the expression of critical viral genes has also resulted in targeted viruses. Work also is being undertaken to restrict or alter the tropism of viruses by altering their ability to infect certain cell types. Finally, the addition of exogenous genes can be used to increase the virus's lytic potential and/or bystander killing; to further induce the host's immune response against cancer cells; and/or to permit the controlled downregulation of viral replication if necessary. The combination of different tumor-targeting mutations in parallel with the expression of foreign genes has resulted in the evolution of second- and third-generation viruses that continue to become further distinct from their native parental strains. The movement of these viruses into the clinic has begun to demonstrate the potential of this approach in the treatment of cancers.

Apoptosis↗