TopBP1 and ATR colocalization at meiotic chromosomes: role of TopBP1/Cut5 in the meiotic recombination checkpoint

Mammalian TopBP1 is a BRCT domain-containing protein whose function in mitotic cells is linked to replication and DNA damage checkpoint. Here, we study its possible role during meiosis in mice. TopBP1 foci are abundant during early prophase I and localize mainly to histone gamma-H2AX-positive domains, where DNA double-strand breaks (required to initiate recombination) occur. Strikingly, TopBP1 showed a pattern almost identical to that of ATR, a PI3K-like kinase involved in mitotic DNA damage checkpoint. In the synapsis-defective Fkbp6(-/-) mouse, TopBP1 heavily stains unsynapsed regions of chromosomes. We also tested whether Schizosaccharomyces pombe Cut5 (the TopBP1 homologue) plays a role in the meiotic recombination checkpoint, like spRad3, the ATR homologue. Indeed, we found that a cut5 mutation suppresses the checkpoint-dependent meiotic delay of a meiotic recombination defective mutant, indicating a direct role of the Cut5 protein in the meiotic checkpoint. Our findings suggest that ATR and TopBP1 monitor meiotic recombination and are required for activation of the meiotic recombination checkpoint.     

Seasonal activity patterns and movements of the raccoon dog, a vector of diseases and parasites, in southern Finland

Activity patterns and movements of raccoon dogs (Nyctereutes procyonoides) were studied in Virolahti, southeast Finland, in 2000–2003. Activity data were compared to those collected from Evo, south-central Finland, in 1990–1993. Activity in winter was compared to weather (temperature and snow depth), day length and moon. Also circadian activity rhythm was studied in Evo. Raccoon dogs moved fastest in late winter after winter dormancy and slowest in autumn before settling in their winter dens. In March, males were moving more often than females. Raccoon dogs stayed usually in their dens in mid-winter (December–February) but were sometimes wandering around also during the harshest months of the year and changed their winter den on average three times. Both day length and weather affected the activity of raccoon dogs in winter. Animals usually stayed in their dens, when temperature was below –10 °C, snow depth >35 cm and day length <7 h and were moving around, when temperature was >0 °C, there was no snow and day length was >10 h. Day length and snow depth together predicted rather well the probability of animals being active during winter. Although raccoon dogs were more often active at night than during the light hours, they also showed rather much diurnal activity.     

Direct evidence for production of microcystins by Anabaena strains from the Baltic Sea

Anabaena is a filamentous, N(2)-fixing, and morphologically diverse genus of cyanobacteria found in freshwater and brackish water environments worldwide. It contributes to the formation of toxic blooms in freshwater bodies through the production of a range of hepatotoxins or neurotoxins. In the Baltic Sea, Anabaena spp. form late summer blooms, together with Nodularia spumigena and Aphanizomenon flos-aquae. It has been long suspected that Baltic Sea Anabaena may produce microcystins. The presence of microcystins has been reported for the coastal regions of the Baltic proper, and a recent report also indicated the presence of the toxin in the open Gulf of Finland. However, at present there is no direct evidence linking Baltic Sea Anabaena spp. to microcystin production. Here we report on the isolation of microcystin-producing strains of the genus Anabaena in the open Gulf of Finland. The dominant microcystin variants produced by these strains included the highly toxic MCYST-LR as well as [d-Asp(3)]MCYST-LR, [d-Asp(3)]MCYST-HtyR, MCYST-HtyR, [d-Asp(3),Dha(7)]MCYST-HtyR, and [Dha(7)]MCYST-HtyR variants. Toxic strains were isolated from the coastal Gulf of Finland as well as from the easternmost open-sea sampling station, where there were lower salinities than at other stations. This result suggests that lower salinity may favor microcystin-producing Anabaena strains. Furthermore, we sequenced 16S rRNA genes and found evidence for pronounced genetic heterogeneity of the microcystin-producing Anabaena strains. Future studies should take into account the potential presence of microcystin-producing Anabaena sp. in the Gulf of Finland.     

Sources of Listeria monocytogenes Contamination in a Cold-Smoked Rainbow Trout Processing Plant Detected by Pulsed-Field Gel Electrophoresis Typing

Sites of Listeria monocytogenes contamination in a cold-smoked rainbow trout (Oncorhynchus mykiss) processing plant were detected by sampling the production line, environment, and fish at different production stages. Two lots were monitored. The frequency of raw fish samples containing L. monocytogenes was low. During processing, the frequency of fish contaminated with L. monocytogenes clearly rose after brining, and the most contaminated sites of the processing plant were the brining and postbrining areas. A total of 303 isolates from the raw fish, product, and the environment were characterized by pulsed-field gel electrophoresis (PFGE). PFGE yielded nine pulsotypes, which formed four clusters. The predominating L. monocytogenes pulsotypes of the final product were associated with brining and slicing, whereas contaminants of raw fish were not detected in the final product. Air-mediated contamination in the plant could not be proved. In accordance with these results, an L. monocytogenes eradication program was planned. The use of hot steam, hot air, and hot water seemed to be useful in eliminating L. monocytogenes. None of the control samples taken in the 5 months after the eradication program was implemented contained L. monocytogenes.     

Pediastrum algae from the classic late glacial Bølling Sø site, Denmark: Response of aquatic biota to climate change

The late glacial and the early Holocene sediments of the classic site Bølling Sø in Denmark are being reinvestigated by multi-proxy analyses. We present here the record of Pediastrum species and discuss the climate-mediated changes in the aquatic ecosystem, as reflected by aquatic proxies (e.g. aquatic plants and mosses, cladocerans, ostracods, bryozoan statoblasts), as well as a number of other proxies (organic content, biogenic silica, carbonates, terrestrial plant macrofossils). Climate had warmed to such an extent at c. 12,500 ¹⁴C yrs BP that aquatic life could begin. Productivity was low and only very scarce indication of a warmer interval predating the Allerød chronozone was found. At the beginning of the Allerød chronozone climate ameliorated and productivity clearly increased. The cool climate of the Younger Dryas chronozone (YD) was more clearly reflected in the terrestrial ecosystem than in the aquatic ecosystem, where productivity appeared to remain rather high. The lake was very shallow and non-stratified during the YD, indicating low effective moisture. Probably it warmed throughout early in the open-water season and in that way enabled higher productivity, even if summer temperatures were rather low. It is also possible that the difference in July temperatures between the late part of the Allerød chronozone and the YD was not large in central Jutland. The amelioration of climate at the beginning of the Holocene is clearly reflected in all proxies. There is also evidence that the lake level rose. The lake probably remained alkaline during all of its history but some evidence suggests that pH was somewhat lowered during the YD chronozone. Pediastrum species appear to be relatively good indicators of environmental conditions; similarly, the concentrations may reflect productivity variations during changing climatic conditions.     

Overexpression and characterization of Wzz of Escherichia coli O86:H2

O-Antigen plays a critical role in the bacterium-host interplay, the chain length is an important factor in O-antigen functions. Wzz protein is responsible for O-antigen chain length regulation, but the mechanism is still unknown. Here, we overexpressed the Wzz of Escherichia coli O86:H2 in wzz mutant O86:H2 strain, the yield can achieve 15 mg/L. The recombinant Wzz was purified to 99% purity in dodecylmaltoside by sequential Ni-affinity chromatography and anion-exchange. Size exclusion chromatography and in vivo cross-linking experiments both showed that Wzz formed tetramer. Furthermore, analysis with circular dichroism revealed that the predominant structural composition in Wzz is alpha-helices, and incubation with O-antigen significantly changed Wzz conformation. The results suggested that Wzz protein can interact with O-antigen.     

The Origin and Evolution of Lake Vähä-Pitkusta, SW Finland – A Multi-Proxy Study of a Meromictic Lake

Lake Vähä-Pitkusta is a 35-m deep meromictic kettle-hole lake in SW Finland. The topmost 15cm of the sediment stratigraphy consists of black gyttja, representing the last ca. 600years. A sediment core from the deepest point was examined with multi-proxy methods to determine the origin and evolution of the basin, the onset of the meromictic conditions and the primary factors that initiated the meromictic processes. The results indicate that Lake Vähä-Pitkusta became isolated from the Baltic basin during the Yoldia Sea stage. After initial unstable sedimentary conditions the development continued steadily until ca. 2500–2300 cal.BP when there is indication of lake level rise and/or increased surface runoff, probably resulting from a cooler and moister climate. The diatom and cladoceran results indicate only a slight rise in the trophic state following the increased erosion. Pollen evidence suggests weak anthropogenic activity in the catchment during the last 1000 years, and this had only little effect on the trophic state, which remained rather low. Thus, it is most unlikely that the trophic state was the primary reason for the origin of meromixis, although it may have contributed to it. We tentatively suggest that the primary reason was the peculiar morphometric dimensions of Lake Vähä-Pitkusta (small, deep, sheltered from winds) which made it very sensitive and that even a very slight increase in soluble electrolytes may push it over the edge into meromixation. It is possible that this did not occur during the cold/moist period around ca. 2300 cal.BP but during the Medieval Climate Anomaly. Studies on sediment geochemistry are needed to verify this assumption.     

Chydorid Ephippia as Indicators of Past Environmental Changes – A New Method

I present a new method, ephippium analysis, to investigate past environmental changes which may have affected chydorid Cladocera (Anomopoda, Chydoridae). I studied chydorid ephippia from sediments of two small lakes (Kaksoislammi and Rutikka) in southern Finland. The relative adundance of chydorid ephippia periodically increased during the Holocene. Ephippia were abundant during the late Pleistocene/early Holocene transition, reflecting the severe climate (short open-water season) that existed prior to the onset of rapid postglacial warming. Both lakes experienced an environmental change in the late Holocene. In Kaksoislammi there was a dramatic change in predator–prey relationships following a decline in pH. All chydorids responded with increased gamogenesis. Prehistoric anthropogenic activities caused a rise in the trophic state in Rutikka and probably caused changes in the predator/food web. One chydorid, Alona affinis, reacted first with increased gamogenesis and then almost disappeared. These first results of ephippium analysis indicate that the method has a great potential in detecting periods of environmental change during the Holocene.