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PubMed2004

Harmonic-hopping in Wallacea's bats.

Evolutionary divergence between species is facilitated by ecological shifts, and divergence is particularly rapid when such shifts also promote assortative mating. Horseshoe bats are a diverse Old World family (Rhinolophidae) that have undergone a rapid radiation in the past 5 million years. These insectivorous bats use a predominantly pure-tone echolocation call matched to an auditory fovea (an over-representation of the pure-tone frequency in the cochlea and inferior colliculus) to detect the minute changes in echo amplitude and frequency generated when an insect flutters its wings. The emitted signal is the accentuated second harmonic of a series in which the fundamental and remaining harmonics are filtered out. Here we show that three distinct, sympatric size morphs of the large-eared horseshoe bat (Rhinolophus philippinensis) echolocate at different harmonics of the same fundamental frequency. These morphs have undergone recent genetic divergence, and this process has occurred in parallel more than once. We suggest that switching harmonics creates a discontinuity in the bats' perception of available prey that can initiate disruptive selection. Moreover, because call frequency in horseshoe bats has a dual function in resource acquisition and communication, ecological selection on frequency might lead to assortative mating and ultimately reproductive isolation and speciation, regardless of external barriers to gene flow.

Acoustics↗
PubMed1997

The next hop.

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Animals↗
PubMed2006

Long-distance radical cation transport in DNA: Horizontal charge hopping in a dimeric quadruplex.

A series of DNA hairpins were synthesized and shown to associate to form quadruplexes formed by stacking five G-quartets in an antiparallel orientation. One of the hairpins in the quadruplex was linked covalently at the 5'-end to an anthraquinone (AQ) group and a 32P label was incorporated either at the 3'-terminus of the AQ-containing hairpin or on its partner hairpin in the quadruplex. Irradiation of the AQ group with UV light leads to the one-electron oxidation of the DNA and concomitant introduction of a radical cation into the DNA. Analysis by PAGE and autoradiography shows that the radical cation reacts at guanines both on the AQ-containing strand and with its partner hairpin in the quadruplex. This observation demonstrates that charge migration in DNA occurs vertically along a DNA chain and horizontally within a G-quartet.

Base Sequence↗
PubMed2004

The fixed combination of valerian and hops (Ze91019) acts via a central adenosine mechanism.

The aim of the study was to demonstrate competition between caffeine and a fixed valerian/hop extract combination (Ze91019) by the central adenosine mechanism. EEG was used to describe the action of caffeine on the central nervous system after oral administration (200 mg) in healthy volunteers. In addition to caffeine, the volunteers (16 in each group) received either placebo or verum (2 and 6 tablets containing the valerian/hop extract). The EEG responses were recorded every 30 min thereafter. The verum medication was capable of reducing (2 tablets) or inhibiting (6 tablets) the arousal induced by caffeine. This pharmacodynamic action was observed 60 minutes after oral administration, indicating not only competition between the antagonist caffeine and the partial agonist, i. e., the valerian/hop extract but also bio-availability of the compound(s) responsible for the agonistic action. In conclusion, the valerian/hop extract acts via a central adenosine mechanism which is possibly the reason for its sleep-inducing and -maintaining activity.

Administration, Oral↗
PubMed2007

Hopping, skipping or jumping to conclusions? Clarifying the role of the JTC bias in delusions.

INTRODUCTION: There is substantial evidence that patients with delusions exhibit a reasoning bias--known as the "jumping to conclusions" (JTC) bias--which leads them to accept hypotheses as correct on the basis of less evidence than controls. We address three questions concerning the JTC bias that require clarification. Firstly, what is the best measure of the JTC bias? Second, is the JTC bias correlated specifically with delusions, or only with the symptomatology of schizophrenia? And third, is the bias enhanced by emotionally salient material? METHODS: To address these questions, we conducted a series of meta-analyses of studies that used the Beads task to compare the probabilistic reasoning styles of individuals with and without delusions. RESULTS: We found that only one of four measures of the JTC bias--"draws to decision"--reached significance. The JTC bias exhibited by delusional subjects-as measured by draws to decision--did not appear to be solely an epiphenomenal effect of schizophrenic symptomatology, and was not amplified by emotionally salient material. CONCLUSIONS: A tendency to gather less evidence in the Beads task is reliably associated with the presence of delusional symptomatology. In contrast, certainty on the task, and responses to contradictory evidence, do not discriminate well between those with and without delusions. The implications for the underlying basis of the JTC bias, and its role in the formation and maintenance of delusions, are discussed.

Bias↗