Action ability modulates time‑to‑collision judgments

Time-to-collision (TTC) underestimation has been interpreted as an adaptive response that allows observers to have more time to engage in a defensive behaviour. This bias seems, therefore, strongly linked to action preparation. There is evidence that the observer’s physical fitness modulates the underestimation effect so that people who need more time to react (i.e. those with less physical fitness) show a stronger underestimation effect. Here we investigated whether this bias is influenced by the momentary action capability of the observers. In the first experiment, participants estimated the time-to-collision of threatening or non-threatening stimuli while being mildly immobilized (with a chin rest) or while standing freely. Having reduced the possibility of movement led participants to show more underestimation of the approaching stimuli. However, this effect was not stronger for threatening relative to non-threatening stimuli. The effect of the action capability found in the first experiment could be interpreted as an expansion of peripersonal space (PPS). In the second experiment, we thus investigated the generality of this effect using an established paradigm to measure the size of peripersonal space. Participants bisected lines from different distances while in the chin rest or standing freely. The results replicated the classic left-to-right gradient in lateral spatial attention with increasing viewing distance, but no effect of immobilization was found. The manipulation of the momentary action capability of the observers influenced the participants’ performance in the TTC task but not in the line bisection task. These results are discussed in relation to the different functions of PPS

Ageing of zinc in highly-weathered iron-rich soils

BACKGROUND AND AIMS: The reactivity and bioavailability of soluble metal added to soil decreases with time. This process, called ageing, has mainly been investigated in temperate soils. This paper uses isotopic exchangeability to investigate Zn ageing in a range of highly weathered and/or oxide-rich soils. METHODS: Changes in lability of soluble added Zn (450 mg Zn/kg soil) over time was measured in six contrasting soils, with pH adjusted to give ten treatments per soil type ranging from pH 4 to 7. RESULTS: Decreasing extractability and isotopic exchangeability (lability) over time revealed substantial fixation of added zinc in six highly weathered/variable charge soils. Strong negative relationships between pH and solubility, and pH and lability were observed. In soils with pH > 6.5 a significant proportion of the added metal becomes non-isotopically exchangeable within 15 s of addition. Correlations between Mn solubility and Zn lability throughout the incubation demonstrated the role of redox conditions (and pH) in regulating Zn lability. CONCLUSIONS: Results showed zinc fixation was strongly related to pH and ageing time, and relatively unaffected by soil type and mineralogy. Very rapid reductions in radiolability immediately (<15 s) after spiking suggest that precipitation plays a role in fixation of added soluble zinc at near neutral pH, however spectroscopic studies are needed to confirm this. Radiolability of added zinc was also affected by changing redox conditions during incubation.Erica Donner, Mike J. McLaughlin, Mark E. Hodson, Diane Heemsbergen, Michael St J. Warne, Stephen Nortcliff and Kris Broo

Global change effects on plant communities are magnified by time and the number of global change factors imposed

Global change drivers (GCDs) are expected to alter community structure and consequently, the services that ecosystems provide. Yet, few experimental investigations have examined effects of GCDs on plant community structure across multiple ecosystem types, and those that do exist present conflicting patterns. In an unprecedented global synthesis of over 100 experiments that manipulated factors linked to GCDs, we show that herbaceous plant community responses depend on experimental manipulation length and number of factors manipulated. We found that plant communities are fairly resistant to experimentally manipulated GCDs in the short term (<10 y). In contrast, long-term (≥10 y) experiments show increasing community divergence of treatments from control conditions. Surprisingly, these community responses occurred with similar frequency across the GCD types manipulated in our database. However, community responses were more common when 3 or more GCDs were simultaneously manipulated, suggesting the emergence of additive or synergistic effects of multiple drivers, particularly over long time periods. In half of the cases, GCD manipulations caused a difference in community composition without a corresponding species richness difference, indicating that species reordering or replacement is an important mechanism of community responses to GCDs and should be given greater consideration when examining consequences of GCDs for the biodiversity–ecosystem function relationship. Human activities are currently driving unparalleled global changes worldwide. Our analyses provide the most comprehensive evidence to date that these human activities may have widespread impacts on plant community composition globally, which will increase in frequency over time and be greater in areas where communities face multiple GCDs simultaneously

Concurrent genetic alterations in DNA polymerase proofreading and mismatch repair in human colorectal cancer

Genomic sequences encoding the 3′ exonuclease (proofreading) domains of both replicative DNA polymerases, pol delta and pol epsilon, were explored simultaneously in human colorectal carcinomas including six established cell lines. Three unequivocal sequence alterations, including one previously reported, were found, and all these were considered as dysfunctional mutations in light of the local amino-acid sequences. In particular, the F367S mutation found in the POLE gene encoding the pol epsilon catalytic subunit, which includes the proofreading domain, is the first found in human diseases. Surprisingly, the tumours carrying these proofreading domain mutations were all defective in DNA mismatch repair (MMR). In addition to the two cell lines with acknowledged MMR gene mutations, the third tumour was also demonstrated to harbour a distinct mutation in MLH1, and indeed exhibited a microsatellite-unstable phenotype. These findings suggest that, in concert with MMR deficiency, defective polymerase proofreading may also contribute to the mutator phenotype observed in human colorectal cancer. Our observations may suggest previously unrecognised complexities in the molecular abnormalities underlying the mutator phenotype in human neoplasms