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Assessing the impacts of invasive predators on the demography and distribution of native species is critical for understanding mechanisms of species persistence and informing the design of recovery programmes. On the oceanic island of Guam, the introduction of the predatory brown treesnake Boiga irregularis after World War II caused the near-total loss of the native forest avifauna. Localised snake control measures have been implemented since the early 1990s, yet it remains poorly understood how they have impacted Guam’s remaining native bird populations. To address this question, we combined intensive area searches of Andersen Air Force Base (AAFB) with island-wide transect surveys and opportunistic sightings to provide a comprehensive update on the distribution and abundance of Såli (Micronesian Starling, Aplonis opaca) – one of Guam’s last extant native bird species. Area searches of AAFB, where the largest remnant of the Såli population persists, revealed a 15-fold population increase since the last survey in the early 1990s, and transect surveys and opportunistic sightings indicate incipient recolonisation of other urbanised areas of northern and central Guam. We estimate the current island-wide population size at ~1,400 individuals. The population increase can likely be attributed to a combination of snake control measures and the Såli’s ability to exploit urban refugia for nesting and roosting. Although these trends demonstrate some population recovery, a skewed age ratio (>90% adults and subadults) at AAFB and a highly urbanised distribution and low abundance outside AAFB indicate that snake predation continues to strongly impact the population. More intensive snake suppression efforts, particularly in forested areas, may allow for the Såli population to attain its former distribution and abundance on Guam. More broadly, our findings reinforce the importance of urban areas as refugia for some threatened species.
The mechanisms underlying the association of insulin-like growth factor-I (IGF-I) and leg length (a marker of prepubertal growth) with cancer risk are uncertain. One hypothesis is that diet in early childhood might provide the link. The aim of the present study was to examine the association between early diet – in particular, the intakes of cows' milk and dairy products – and height, leg length and IGF-I levels at age 7–8 years.
Children participating in the Avon Longitudinal Study of Parents and Children.
Diet was assessed using a 3-day unweighed food record. Anthropometry, IGF-I and insulin-like growth factor-binding protein-3 (IGFBP-3) were measured by standard methods.
Data on both diet and height were available for 744 children (404 boys) and on diet and IGF for 538 (295 boys). After adjusting for energy, both cows' milk and dairy product intakes were positively associated with IGF-I (P=0.040 and 0.027, respectively) and IGFBP-3 levels (P=0.082 and 0.067, respectively). These associations persisted on adjustment for potential confounders, but were abolished on controlling for protein intake. In energy-adjusted models there was only weak evidence of associations of milk and dairy product intakes with anthropometry. In boys only, dairy product intake was positively associated with leg length (equivalent to a 0.058 (0.002, 0.114) standard deviation score increase in leg length per 100 g increase in daily intake).
These data provide some evidence that variation in childhood milk and dairy product intakes underlies associations of leg length, IGF-I and cancer risk. The association appears to be due to the protein content of milk.
A cytidine-free ribozyme with RNA ligase activity
was obtained by in vitro evolution, starting from a pool
of random-sequence RNAs that contained only guanosine,
adenosine, and uridine. This ribozyme contains 74 nt and
catalyzes formation of a 3′,5′-phosphodiester
linkage with a catalytic rate of 0.016 min−1.
The RNA adopts a simple secondary structure based on a
three-way junction motif, with ligation occurring at the
end of a stem region located several nucleotides away from
the junction. Cytidine was introduced to the cytidine-free
ribozyme in a combinatorial fashion and additional rounds
of in vitro evolution were carried out to allow the molecule
to adapt to this added component. The resulting cytidine-containing
ribozyme formed a 3′,5′ linkage with a catalytic
rate of 0.32 min−1. The improved rate
of the cytidine-containing ribozyme was the result of 12
mutations, including seven added cytidines, that remodeled
the internal bulge loops located adjacent to the three-way
junction and stabilized the peripheral stem regions.
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