What determines the way of deposition of excavated soil

Subterranean rodents continuously extend their burrow systems primarily in search of food, which has an important impact on the ecosystem in which they live. Excavated soil may be pushed either into aboveground mounds or into tunnels underground. Factors affecting the amount of burrowing and the preference of aboveground or underground soil deposition are, nevertheless, little known. We investigated the influence of food supply, soil hardness, and the animal’s body mass on the mode of soil deposition in ten burrow systems of free ranging silvery mole-rats Heliophobius argenteocinereus Peters, 1846. In each burrow system, we estimated the volume of backfilled tunnels and the volume of soil deposited aboveground. The highest amount of variation in these parameters was explained by the interaction of food supply and soil hardness. The ratio of the volume of backfilled tunnels to the volume of mounds was not significantly dependent on any of the explanatory variables. The proportion of backfilled tunnels decreased with the increasing volume of the complete burrow system. We propose that both low food supply and soft soil lead to an increased amount of burrowing, which results in a larger volume of soil deposited both above ground and under ground over a given period of time.     

Repeatability of nest predation in passerines depends on predator species and time scale

It has been proposed that some specific locations of bird's nests have higher intrinsic chances of being depredated than other locations. This predicts that fates of consecutive nesting attempts at the same site should be repeatable. We used 20 pairs of old thrush nests to simulate repeated nesting attempts at the same sites, both within and between breeding seasons (n=40  sites×2  trials×2  years=160). Each nest was monitored by a camera to record multiple predation events and to identify predators. Predation by all predator species was repeatable during a 15-day trial. Predation by principal predators (jay Garrulus glandarius , marten Martes martes / foina ) and total predation (all species combined) was not correlated within pairs of simultaneously exposed nests or within samples of nests from particular study plot, and not repeatable for individual nests between-trials or between-years. These findings suggest short-term effect of predator memory causing revisitation of previously depredated nests during a current nesting trial (all predators); do not support an effect of nest site features on multiple nest discoveries and/or an effect of nest location on repeated random encounters with the same nest (principal predators). Long-term repeatability and correlation within pairs of simultaneously exposed nests was detectable only in occasional predators (great spotted woodpecker Dendrocopos major , possibly also squirrel Sciurus vulgaris ), which suggests effect of nest location combined with site fidelity and individual foraging specialization of these predators. We conclude that repeatability of nest predation depends on the time scale considered and the local predator community. We caution against spurious findings of repeatable nest predation resulting simply from statistical properties of correlation in binary data (nest fates).     

Effects of environmental air pollution on endogenous oxidative DNA damage in humans

Epidemiological studies conducted in metropolitan areas have demonstrated that exposure to environmental air pollution is associated with increases in mortality. Carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) are the major source of genotoxic activities of organic mixtures associated with respirable particulate matter, which is a constituent of environmental air pollution. In this study,we wanted to evaluate the relationship between exposure to these genotoxic compounds present in the air and endogenous oxidative DNA damage in three different human populations exposed to varying levels of environmental air pollution. As measures of oxidative DNA damage we have determined 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) by liquid chromatography–tandem mass spectrometry (LC–MS/MS) and cyclic pyrimidopurinone N-1,N² malondialdehyde-2′-deoxyguanosine (M₁dG) by the immunoslot blot assay from lymphocyte DNA of participating individuals. The level of endogenous oxidative DNA damage was significantly increased in individuals exposed to environmental air pollution compared to unexposed individuals from Kosice (8-oxodG adducts) and Sofia (M₁dG adducts). However, there was no significant difference in the level of endogenous oxidative DNA and exposure to environmental air pollution in individuals from Prague (8-oxodG and M₁dG adducts) and Kosice (M₁dG adducts). The average level of M₁dG adducts was significantly lower in unexposed and exposed individuals from Kosice compared to those from Prague and Sofia. The average level of 8-oxodG adducts was significantly higher in unexposed and exposed individuals from Kosice compared to those from Prague. A significant increasing trend according to the interaction of c-PAHs exposure and smoking status was observed in levels of 8-oxodG adducts in individuals from Kosice. However, no other relationship was observed for M₁dG and 8-oxodG adduct levels with regard to the smoking status and c-PAH exposure status of the individuals. The conclusion that can be made from this study is that environmental air pollution may alter the endogenous oxidative DNA damage levels in humans but the effect appears to be related to the country where the individuals reside. Genetic polymorphisms of the genes involved in metabolism and detoxification and also differences in the DNA repair capacity and antioxidant status of the individuals could be possible explanations for the variation observed in the level of endogenous oxidative DNA damage for the different populations.     

Drivers of temporal changes in temperate forest plant diversity vary across spatial scales

Global biodiversity is affected by numerous environmental drivers. Yet, the extent to which global environmental changes contribute to changes in local diversity is poorly understood. We investigated biodiversity changes in a meta‐analysis of 39 resurvey studies in European temperate forests (3988 vegetation records in total, 17–75 years between the two surveys) by assessing the importance of (i) coarse‐resolution (i.e., among sites) vs. fine‐resolution (i.e., within sites) environmental differences and (ii) changing environmental conditions between surveys. Our results clarify the mechanisms underlying the direction and magnitude of local‐scale biodiversity changes. While not detecting any net local diversity loss, we observed considerable among‐site variation, partly explained by temporal changes in light availability (a local driver) and density of large herbivores (a regional driver). Furthermore, strong evidence was found that presurvey levels of nitrogen deposition determined subsequent diversity changes. We conclude that models forecasting future biodiversity changes should consider coarse‐resolution environmental changes, account for differences in baseline environmental conditions and for local changes in fine‐resolution environmental conditions.     

Emerging subject for chiral separation science: cluster boron compounds

The structural chirality is an inherent feature of fully synthetic boron cluster compounds that sometimes exhibit unique biochemical effects. HPLC studies with zwitter-ionic cluster boron compounds and electrophoretic studies with boron cluster anions reveal that the chiral separability of these species is remarkably dissimilar to that of organic species, if uncharged cyclodextrins are used as chiral selectors. Furthermore, marked differences were found between the analytical characteristics of the chiral separations of the boron cluster species and those of the organic species with uncharged cyclodextrins. The present-day experimental database indicates that the rules valid for the chiral separations of the organic species cannot be applied to the chiral separations of the boron cluster species without experimental verification. The current extent of research work devoted to the investigation of chirality and chiral separations of boron cluster species is negligibly small in comparison with that devoted to the investigation of chirality and chiral separations of organic species. This makes difficult a reliable explanation of both the particularities observed in chiral separations of boron cluster species with cyclodextrins as chiral selectors and the strange effects related to these separations at the moment.     

Synthesis and antimycobacterial properties of N-substituted 6-amino-5-cyanopyrazine-2-carboxamides

A series of fifteen new compounds related to pyrazinamide (PZA) were synthesized, characterized with analytical data and screened for antimycobacterial, antifungal and antibacterial activity. The series consists of 6-chloro-5-cyanopyrazine-2-carboxamide and N-substituted 6-amino-5-cyanopyrazine-2-carboxamides, derived from the previous by nucleophilic substitution with various non-aromatic amines (alkylamines, cycloalkylamines, heterocyclic amines). Some of the compounds exerted antimycobacterial activity against Mycobacterium tuberculosis equal to pyrazinamide (12.5-25 μg/mL). More importantly, 6-chloro-5-cyanopyrazine-2-carboxamide and 5-cyano-6-(heptylamino)pyrazine-2-carboxamide were active against Mycobacterium kansasii and Mycobacterium avium, which are unsusceptible to PZA. Basic structure-activity relationships are presented. Only weak antifungal and no antibacterial activity was detected.     

Extended longevity of reproductives appears to be common in Fukomys mole-rats (Rodentia, Bathyergidae)

African mole-rats (Bathyergidae, Rodentia) contain several social, cooperatively breeding species with low extrinsic mortality and unusually high longevity. All social bathyergids live in multigenerational families where reproduction is skewed towards a few breeding individuals. Most of their offspring remain as reproductively inactive "helpers" in their natal families, often for several years. This "reproductive subdivision" of mole-rat societies might be of interest for ageing research, as in at least one social bathyergid (Ansell's mole-rats Fukomys anselli), breeders have been shown to age significantly slower than non-breeders. These animals thus provide excellent conditions for studying the epigenetics of senescence by comparing divergent longevities within the same genotypes without the inescapable short-comings of inter-species comparisons. It has been claimed that many if not all social mole-rat species may have evolved similar ageing patterns, too. However, this remains unclear on account of the scarcity of reliable datasets on the subject. We therefore analyzed a 20-year breeding record of Giant mole-rats Fukomys mechowii, another social bathyergid species. We found that breeders indeed lived significantly longer than helpers (ca. 1.5-2.2fold depending on the sex), irrespective of social rank or other potentially confounding factors. Considering the phylogenetic positions of F. mechowii and F. anselli and unpublished data on a third Fukomys-species (F. damarensis) showing essentially the same pattern, it seems probable that the reversal of the classic trade-off between somatic maintenance and sexual reproduction is characteristic of the whole genus and hence of the vast majority of social mole-rats.     

Hemoglobin adducts in 1,3-butadiene exposed Czech workers: Female–male comparisons

We previously reported results of a molecular epidemiological study of female and male 1,3-butadiene (BD) exposed Czech workers showing that females appeared to absorb or metabolize less BD per unit exposure concentration than did males, based on metabolite concentrations in urine (Chem. Biol. Interact. 166 (2007) 63–77). However, that unexpected observation could not be verified at the time because the only additional BD metabolite measurement attempted was for 1,2,3,4-diepoxybutane (DEB) as reflected in specific N,N[2,3-dihydroxy-1,4-butyl]valine (pyr-Val) hemoglobin adduct concentrations, which were not quantifiable in any subject with the method then employed. Neither somatic gene mutations nor chromosome aberrations were associated with BD exposure levels in that study, consistent with findings in an earlier Czech study of males only. We have since measured production and accumulation of the 1,2-dihydroxy-3,4-epoxybutane (EBD) metabolite as reflected in N-[2,3,4-trihydroxy-butyl]valine (THB-Val) hemoglobin adduct concentrations. The mean THB-Val concentration was significantly higher in exposed males than in control males (922.3 pmol/g and 275.5 pmol/g, respectively), but exposed and control females did not differ significantly (224.5 pmol/g and 181.1 pmol/g, respectively). In both the control and exposed groups mean THB-Val concentrations were significantly higher for males than females. THB-Val concentrations were significantly correlated with mean 8-h TWA exposures for both males and females, but the rate of increase with increasing BD exposure was significantly lower for females. THB-Val concentrations also increased with increasing urine M2 metabolite [isomeric mixture of 1-hydroxy-2-{N-actylcysteinyl}-3-butene and 2-hydroxy-1-{N-acetylcysteinyl}-3-butene] concentrations in both sexes but the rate of increase was also lower in females than in males. There were no significant correlations between THB-Val concentrations and either somatic gene mutations or chromosome aberrations in either males or females. These results using another biomarker to measure a second metabolite of BD support the original conclusion that females absorb or metabolize less BD than males per unit exposure and indicate that the size of the difference increases with exposure. This observation in humans differs from findings in rodents where at prolonged exposures to high BD levels the females form higher amounts of hemoglobin adducts than do males, a difference that disappears at shorter duration lower exposure levels, while female susceptibility to BD induced mutations and tumorgenesis in rodents appears to persist at all BD exposure levels.     

Poikilothermic traits in Mashona mole-rat (Fukomys darlingi). Reality or myth?

The African mole-rats (Bathyergidae, Rodentia) is a mammalian family well known for a variety of ecophysiological adaptations for strictly belowground life. The smallest bathyergid, the hairless naked mole-rat from arid areas in Eastern Africa, is even famous as the only truly poikilothermic mammal. Another bathyergid, the Mashona mole-rat (Fukomys darlingi) from Zimbabwe, is supposed to have strong poikilothermic traits, because it is not able to maintain a stable body temperature at ambient temperatures below 20 °C. This is surprising because, compared to the naked mole-rat, this species, together with all congenerics, is larger, haired, and living in more seasonal environment. In addition, other Fukomys mole-rats show typical mammalian pattern in resting metabolic rates. In our study, we measured resting metabolic rate and body temperature of Mashona mole-rats from Malawi across a gradient of ambient temperatures to test its poikilothermic traits. We found that the adult mass specific resting metabolic rate was 0.76±0.20 ml O₂ g⁻¹ h⁻¹ and body temperature 34.8±1.1 °C in the thermoneutral zone (27–34 °C). Body temperature was stable (33.0±0.5 °C) at ambient temperatures from 10 to 25 °C. We thus cannot confirm poikilothermic traits in this species, at least for its Malawian population. Factors potentially explaining the observed discrepancy in Mashona mole-rat energetics are discussed.