Daily patterns of nest visits are correlated with ambient temperature in the Northern Wheatear

The diurnal pattern of foraging behaviour in birds is commonly linked to the risk of starvation and predation. During the breeding season, when offspring place additional demands on the quantity of food adults need to collect, diurnal foraging patterns may be influenced to a greater extent by food availability because adults need to balance starvation–predation risks not only for themselves but also their offspring. We used data-loggers to measure diurnal variation in rates of nest visits to 7- to 10-day-old nestlings of the insectivorous Northern Wheatear Oenanthe oenanthe in Swedish farmland habitat. Adults provisioned the nestlings with food for an average 19.5 h each day (n = 11 pairs), with visitation rates sharply increasing during the morning, remaining relatively stable between 0800 and 1700 hours, and then declining in the evening. This pattern is similar to daily temperature fluctuations and is consistent with the hypothesis that nest visit rates are a function of temperature-dependent prey availability. Higher rates of nest visits on warm days support this correlation between temperature and offspring feeding. However, without data on the rate of self-feeding by adults it is difficult to distinguish between patterns of nest visits being driven by food availability, or starvation–predation constraints being imposed on the parents; thus, future studies of patterns of offspring feeding should collect data on the self-feeding behaviour of the adults.     

Human abasic endonuclease action on multilesion abasic clusters: implications for radiation-induced biological damage

Clustered damages—two or more closely opposed abasic sites, oxidized bases or strand breaks—are induced in DNA by ionizing radiation and by some radiomimetic drugs. They are potentially mutagenic or lethal. High complexity, multilesion clusters (three or more lesions) are hypothesized as repair-resistant and responsible for the greater biological damage induced by high linear energy transfer radiation (e.g. charged particles) than by low linear energy transfer X- or γ-rays. We tested this hypothesis by assessing human abasic endonuclease Ape1 activity on two- and multiple-lesion abasic clusters. We constructed cluster-containing oligonucleotides using a central variable cassette with abasic site(s) at specific locations, and 5′ and 3′ terminal segments tagged with visually distinctive fluorophores. The results indicate that in two- or multiple-lesion clusters, the spatial arrangement of uni-sided positive [in which the opposing strand lesion(s) is 3′ to the base opposite the reference lesion)] or negative polarity [opposing strand lesion(s) 5′ to the base opposite the reference lesion] abasic clusters is key in determining Ape1 cleavage efficiency. However, no bipolar clusters (minimally three-lesions) were good Ape1 substrates. The data suggest an underlying molecular mechanism for the higher levels of biological damage associated with agents producing complex clusters: the induction of highly repair-resistant bipolar clusters.     

Reversal of motility loss in bongo antelope (Tragelaphus eurycerus isaaci) spermatozoa contaminated with hyposmotic urine during electroejaculation

Semen collected by a combination of ampullary (rectal) massage and electroejaculation of a bongo bull was incidentally contaminated with urine (1:3.7). At 1.5h post-collection, progressive motility was 0% but some spermatozoa had intermittently twitching tails. Subsequent dilution with media and processing improved the progressive motility (up to 50%) and intact membranes (up to 71%) of spermatozoa. After thawing, the respective values were 35 and 70%. The osmolarity and pH of the contaminated supernatant was 151 mOsm and 7.45, respectively. Initial progressive motility in a non-contaminated portion of semen collected during the same procedure was 80%, and, after thawing, 60 and 90%, of the spermatozoa showed progressive motility and intact membranes, respectively. In conclusion, urine-contaminated bongo spermatozoa can regain progressive motility after dilution with isosmotic solutions and survive cryopreservation.     

Induction of Phase Variation Events in the Life Cycle of the Marine Coccolithophorid Emiliania huxleyi

Emiliania huxleyi is a unicellular marine alga that is considered to be the world's major producer of calcite. The life cycle of this alga is complex and is distinguished by its ability to synthesize exquisitely sculptured calcium carbonate cell coverings known as coccoliths. These structures have been targeted by materials scientists for applications relating to the chemistry of biomedical materials, robust membranes for high-temperature separation technology, lightweight ceramics, and semiconductor design. To date, however, the molecular and biochemical events controlling coccolith production have not been determined. In addition, little is known about the life cycle of E. huxleyi and the environmental and physiological signals triggering phase switching between the diploid and haploid life cycle stages. We have developed laboratory methods for inducing phase variation between the haploid (S-cell) and diploid (C-cell) life cycle stages of E. huxleyi. Plating E. huxleyi C cells on solid media was shown to induce phase switching from the C-cell to the S-cell life cycle stage, the latter of which has been maintained for over 2 years under these conditions. Pure cultures of S cells were obtained for the first time. Laboratory conditions for inducing phase switching from the haploid stage to the diploid stage were also established. Regeneration of the C-cell stage from pure cultures of S cells followed a predictable pattern involving formation of large aggregations of S cells and the subsequent production of cultures consisting predominantly of diploid C cells. These results demonstrate the ability to manipulate the life cycle of E. huxleyi under controlled laboratory conditions, providing us with powerful tools for the development of genetic techniques for analysis of coccolithogenesis and for investigating the complex life cycle of this important marine alga.     

Immune response of nestling warblers varies with extra-pair paternity and temperature

Extra-pair mating is widespread in birds, but its adaptive function remains unclear. It is often suggested that females obtain superior genes for their offspring as a consequence of extra-pair mating, but the evidence is limited. In this study, we examined the hypothesis that extra-pair mating provides females with offspring that have superior immune responses. We found that the T-cell-mediated immune response of extra-pair young was stronger than that of within-pair young in common yellowthroats (Geothlypis trichas). This paternity effect occurred when we compared all nestlings in the population, as well as in comparisons of both paternal and maternal half-siblings. Paternal half-siblings had a stronger immune response when they were produced with extra-pair females than with the male's social mate, which suggests that the greater immune response of extra-pair young was caused by nonadditive (compatible) genetic effects. However, these patterns were only significant in the colder of 2 years. Immune response was related positively to air temperature and nestlings had a stronger immune response in the warmer year. We suggest that such environmental variation could obscure the genetic benefits of extra-pair mating.     

Biochemical characterization of cholesteryl ester transfer protein inhibitors

Cholesteryl ester transfer protein (CETP) has been identified as a novel target for increasing HDL cholesterol levels. In this report, we describe the biochemical characterization of anacetrapib, a potent inhibitor of CETP. To better understand the mechanism by which anacetrapib inhibits CETP activity, its biochemical properties were compared with CETP inhibitors from distinct structural classes, including torcetrapib and dalcetrapib. Anacetrapib and torcetrapib inhibited CETP-mediated cholesteryl ester and triglyceride transfer with similar potencies, whereas dalcetrapib was a significantly less potent inhibitor. Inhibition of CETP by both anacetrapib and torcetrapib was not time dependent, whereas the potency of dalcetrapib significantly increased with extended preincubation. Anacetrapib, torcetrapib, and dalcetrapib compete with one another for binding CETP; however anacetrapib binds reversibly and dalcetrapib covalently to CETP. In addition, dalcetrapib was found to covalently label both human and mouse plasma proteins. Each CETP inhibitor induced tight binding of CETP to HDL, indicating that these inhibitors promote the formation of a complex between CETP and HDL, resulting in inhibition of CETP activity.