Schaeferiana (Gaboniella subgen. n.) incompleta sp. n. from Gabon, with notes on its relationships and new records from the Central African Republic (Hemiptera, Heteroptera, Pyrrhocoridae)

A new subgenus, Gaboniellasubgen. n., of the genus Schaeferiana Stehlík, 2008, and its type species, Schaeferiana (Gaboniella) incompletasp. n. are described from Gabon. In addition the first state records of Sericocoris (Depressoculus) albomaculatus Stehlík, 2008 and Schaeferiana (Schaeferiana) mirabilis Stehlík, 2008 from the Central African Republic are provided.     

Molecular mechanisms of silybin and 2,3-dehydrosilybin antiradical activity—role of individual hydroxyl groups

The flavonolignans silybin (1) and 2,3-dehydrosilybin (2) are important natural compounds with multiple biological activities operating at various cell levels. Many of these effects are connected with their radical-scavenging activities. The molecular mechanisms of the antioxidant activity of these compounds and even the functional groups responsible for this activity are not yet well known. Their mechanism can be inferred from the structures of the dimeric products obtained from radical-mediated reactions of selectively methylated derivatives of 1 and 2. The radical oxidation of 1 methylated at 7-OH and 2 methylated at both 3-OH and 7-OH yields C–C and C–O dimers that enable the molecular mechanism of their E-ring interaction with radicals to be elucidated and shows the importance of the 20-OH group in this respect. The pivotal role of the 3-OH group in the radical-scavenging activity of 2 was confirmed through the formation of another type of dimer from its selectively methylated derivative.     

Ecology of Testate Amoebae in the Komo?any Ponds in the Vltava Basin

Testate amoeba (TA) assemblages were collected in 2005 from four ponds in Komo?any (Prague, Czech Republic). An analysis of seasonal taxonomic variability of TA populations and its correlation with the limnological characteristics of the area (temperature, pH, total organic carbon, nitrogen, phosphorus, heavy metals, etc.) was performed. The predominant genera were Difflugia, Arcella, and Centropyxis. The most significant changes in the TA community occurred between March and July. Arcella genus dominated in March and April; in May, Arcella and Centropyxis genera were present in the same amount; in June, Arcella genus disappeared, and Difflugia genus started to dominate the community. A multivariate redundancy analysis showed statistically significant correlations between the environmental parameters and the composition of the TA community. The results indicate a negative correlation between TA quantities and Ni, Cd, PAH, Mn, As, and Pb. TA were also affected by concentrations of NH4(+), NO3(-), and P, as well as by temperature variations. The observed correlations between the species composition and environmental parameters can be used in paleoecological interpretations of fossil TA communities. Our results also prove the suitability of TA as water quality indicators in urban areas.     

Micronuclei in lymphocytes from currently active uranium miners

Micronuclei can be used as markers of past radiation exposure, but only few studies have dealt with uranium miners. In this paper, we report on micronuclei in lymphocytes from individuals currently working at Ro?ná, Czech Republic, the last functioning uranium mine in the European Union. A modified micronucleus-centromere test was applied to assess the occurrence of micronuclei in stimulated lymphocytes, as well as their content in terms of whole chromosomes or fragments. Compared with unexposed individuals, the miners had higher frequencies of micronucleus-containing lymphocytes and higher percentages of micronuclei without centromeres, and the differences were significant for both parameters (0.74 ± 0.60 vs. 0.50 ± 0.42, p = 0.017 and 49 ± 44 vs. 12 ± 21, p = 0.0002; means ± standard deviations). There were also significant correlations between one or other of these parameters on the one hand and various dose values on the other, in particular with a 'retrievable' dose, that is, a dose whose effect should still be recognisable in lymphocytes assuming a half-life of 3 years. The 'retrievable' dose at which a doubling of the micronucleus frequency was observed was around 35 mSv, corresponding to a total dose of 90 mSv received while working in the mines. Altogether, our data show that the micronucleus-centromere test is a valuable tool for the assessment of past radiation exposure in uranium miners. The scatter in the data is of course far too great to allow individual dosimetry, but for groups of a few dozen exposed individuals, the method can be used to monitor doses clearly below 100 mSv.     

The Fe/S Cluster Assembly Protein Isd11 Is Essential for tRNA Thiolation in Trypanosoma brucei

Fe/S clusters are part of the active site of many enzymes and are essential for cell viability. In eukaryotes the cysteine desulfurase Nfs (IscS) donates the sulfur during Fe/S cluster assembly and was thought sufficient for this reaction. Moreover, Nfs is indispensable for tRNA thiolation, a modification generally required for tRNA function and protein synthesis. Recently, Isd11 was discovered as an integral part of the Nfs activity at an early step of Fe/S cluster assembly. Here we show, using a combination of genetic, molecular, and biochemical approaches, that Isd11, in line with its strong association with Nfs, is localized in the mitochondrion of T. brucei. In addition to its involvement in Fe/S assembly, Isd11 also partakes in both cytoplasmic and mitochondrial tRNA thiolation, whereas Mtu1, another protein proposed to collaborate with Nfs in tRNA thiolation, is required for this process solely within the mitochondrion. Taken together these data place Isd11 at the center of these sulfur transactions and raises the possibility of a connection between Fe/S metabolism and protein synthesis, helping integrate two seemingly unrelated pathways.     

A comparison of the enantioselective reduction potential of five strains of Saccharomyces cerevisiae towards a selected ketone

The enantioselectivity potential of five strains of Saccharomyces cerevisiae was studied for the reduction of ethyl N-{2-{4-[(2-oxocyclohexyl)methyl]phenoxy}ethyl} carbamate (1), an insect juvenile hormone bioanalog. The products of the reaction, the cis and trans isomers of ethyl N-{2-{4-[(2-hydroxycyclohexyl)methyl]phenoxy}ethyl} carbamate (2 and 3), were obtained in 45–49% (w/w) chemical yields and with 79 to > 99% enantiomeric purity values. The absolute configurations of the major products were assigned as ethyl (1S,2S)-N-{2-{4-[(2-hydroxycyclohexyl)methyl]phenoxy}ethyl} carbamate (2) and ethyl (1S,2R)-N-{2-{4-[(2-hydroxycyclohexyl)methyl]phenoxy}ethyl} carbamate (3). The products 2 and 3 belong to the series of the chiral insect juvenile hormone analogs.