Wolf predation and snow cover as mortality factors in the ungulate community of the Bialowieża National Park,Poland

Summary Wolf-ungulate interactions were studied in the pristine deciduous and mixed forests of the Bialowiea National Park in 1985–1989. The study period included two severe and two mild winters. The community of ungulates inhabiting Bialowiea National Park consisted of red deer Cervus elaphus, 55% of all ungulates; wild boar Sus scrofa, 42%; and roe deer Capreolus capreolus, moose Alces alces, and European bison Bison bonasus, about 1% each. The average size of red deer groups increased from 2.7 (SD 2.35) in spring and summer to 6.9 (SD 6.84) in autumn and winter. In winter the group size of red deer was positively correlated with the depth of snow cover and negatively correlated with the mean daily temperature. Average group size of wild boar did not change significantly between seasons; it was 6.8 (SD 5.16) in spring and summer and 5.7 (SD 4.67) in autumn and winter. Analysis of 144 wolf scats showed that wolves preyed selectively on red deer. In October–April, Cervidae (mostly red deer) constituted 91% of biomass consumed by wolves, while wild boar made up only 8%. In May–September deer formed 77% of prey biomass, and the share of wild boar increased to 22%. In all seasons of the year wolves selected juveniles from deer and boar populations: 61% of red deer and 94% of wild boar of determined age recovered from wolves' scats were young <1 year old. Analysis of 117 carcasses of ungulates found in Bialowiea National Park showed that predation was the predominant mortality factor for red deer (40 killed, 10 dead from causes other than predation) and roe deer (4 killed, none dead). Wild boar suffered most from severe winter conditions (8 killed, 56 dead). The percentage of ungulates that had died from undernutrition and starvation in the total mortality was proportional to the severity of winter.     

Cell-density-dependent changes in cell-surface glycopeptides and in adhesion of cultured intestinal epithelial cells

We studied mannose-containing glycopeptides and glycoproteins of subconfluent and confluent intestinal epithelial cells in culture. Cells were labelled with d-[2-³H]mannose for 24h and treated with Pronase or trypsin to release cell-surface components. The cell-surface and cell-residue fractions were then exhaustively digested with Pronase and the resulting glycopeptides were fractionated on Bio-Gel P-6, before and after treatment with endo-β-N-acetylglucosaminidase H to distinguish between high-mannose and complex oligosaccharides. The cell-surface glycopeptides were enriched in complex oligosaccharides as compared with residue glycopeptides, which contained predominantly high-mannose oligosaccharides. Cell-surface glycopeptides of confluent cells contained a much higher proportion of complex oligosaccharides than did glycopeptides from subconfluent cells. The ability of the cells to bind [³H]concanavalin A decreased linearly with increasing cell density up to 5 days in culture and then remained constant. When growth of the cells was completely inhibited by either retinoic acid or cortisol, no significant difference was observed in the ratio of complex to high-mannose oligosaccharides in the cell-surface glycopeptides of subconfluent cells. Only minor differences were found in total mannose-labelled glycoproteins between subconfluent and confluent cells by two-dimensional gel analysis. The adhesion of the cells to the substratum was measured at different stages of growth and cell density. Subconfluent cells displayed a relatively weak adhesion, which markedly increased with increased cell density up to 6 days in culture. It is suggested that alterations in the structure of the carbohydrates of the cell-surface glycoproteins are dependent on cell density rather than on cell growth. These changes in the glycopeptides are correlated with the changes in adhesion of the cells to the substratum.     

Binding of six nucleotide cofactors to the hexameric helicase RepA protein of plasmid RSF1010. 2. Base specificity, nucleotide structure, magnesium, and salt effect on the cooperative binding of the cofactors

Interactions of the RepA hexameric helicase with nucleotide cofactors have been examined using nucleotide analogues, TNP-ADP and TNP-ATP, and unmodified nucleotides. Thermodynamic parameters for the interactions of modified and unmodified nucleotides have been obtained using quantitative fluorescence titration and competition titration methods. The intrinsic binding constant of ATP is by a factor of approximately 10 and approximately 1000 higher than the value observed for ADP and PO(4)(-). The data suggest that helicase acquires free-energy transducing capabilities when associated with the ssDNA, thus, forming a "holoenzyme". ATP binding is characterized by significantly stronger negative cooperativity than ADP. The cooperative interactions are predominantly induced through the specific interactions of the gamma phosphate and the ribose with the protein. The salt effect on cofactor binding indicates a very different nature of the intrinsic and cooperative interactions. Surprisingly, binding of Mg(2+), to both the cofactor and helicase, predominantly controls the ADP-RepA interactions. Mg(2+) cations seem to play a role in affecting the distribution of high and low ssDNA-affinity states, through the strong effect on the diphosphate versus triphosphate binding. The data indicate that Mg(2+) has a dual function in nucleotide-helicase interactions. At low [Mg(2+)], NTP binds stronger than NDP and the enzyme is predominantly in the high ssDNA-affinity state. At higher [Mg(2+)], NTP binds weaker than NDP and the helicase subunits can exist in alternating low- and high-affinity states that facilitate the efficient dsDNA unwinding. The RepA helicase shows a preference toward purine nucleotides. The cooperative interactions are independent of the type of the base.     

Interactions of Chlorophyll and Polypeptide Mixture with Bacterial Reaction Centres

In aqueous solutions of chlorophyll (Chl) a with synthesized polypeptides, at high ratios of Chl to polypeptides (about 75–150 µM to 500 µM) clusters of polypeptides and pigment molecules were formed. The main absorption maxima of more than one formed cluster were located at about 500 nm (Soret band) and in the region of 720–806 nm (red band). The formation of these clusters was fairly slow (some hours) at room temperature and even slower at 4 °C. The rate of cluster formation increased with the increase in Chl concentration. The addition of the even low amount of reaction centres (RCs), separated from the purple bacteria Rhodobacter sphaeroides, to the sample of Chl with polypeptides caused a very strong decrease in the efficiency of cluster formation, and a change in concentration ratios of various pigment-polypeptide aggregates. It was probably a competition between the interaction of Chl with polypeptides and with the RCs. The yield of thermal deactivation of the clusters was high, much higher than that for the RCs alone and it was different for various types of cluster. The clusters absorbing at 725–750 nm were fluorescent with maximum of emission at about 770 nm, whereas clusters absorbing at about 800 nm were nonfluorescent.     

Nuclei of nonviable ovine somatic cells develop into lambs after nuclear transplantation

Here we report on the successful reprogramming of nuclei from somatic cells rendered nonviable by heat treatment. Granulosa cells from adult sheep were heated to nonphysiological temperatures (55 degrees C or 75 degrees C) before their nuclei were injected into enucleated metaphase II oocytes. Reprogramming was demonstrated by the capacity of the reconstructed embryos to develop to the blastocyst stage in vitro and into fetuses and viable offspring in suitable foster mothers. To our knowledge, this is the first report of cloned mammalian offspring originating from nonviable cells. In addition, our experiments show that heat-treating donor nuclei destabilizes higher-order features of chromatin (but leaves intact its nucleosomal organization) and results in a high proportion of reconstructed embryos developing to the blastocyst stage and beyond.     

Susceptibility of naked oat cultivar seeds to mechanical damage

Mechanical damage to seeds occurring during harvesting and threshing, especially in naked cultivars, is one of the main factors decreasing the size and quality of yield. The objective of this study was to assess the susceptibility of naked oat cultivars to mechanical damage, considering the biometric parameters of seeds determined on the basis of computer image analysis and weight tests. The testing was carried out on eight cultivars harvested between 2008 and 2010 at 15% moisture and threshed at either 1.6 or 2.4 m·s^?1 threshing drum speed. A 50% increase in the threshing speed caused an average 19% increase in the frequency and a 29% increase in the area of microdamage to seeds. There was a corresponding 4.1 mm² change in the microdamage area when using the threshing speed of 1.6 m·s^?1, and a 6.1 mm² change when using the threshing speed of 2.4 m·s^?1 was 53% and 68%, respectively, determined by a decreasing seed shape coefficient indicating seed elongation. The greatest resistance to mechanical damage was found on the Bullion cultivar, which was also characterized by the largest total projected area of seeds (7.14 mm²), as well as the greatest seed density (63.8 kg·hL^?1) and thousand kernel weight (TKW) (28.2 g).     

Dimeric RNA Recognition Regulates HIV-1 Genome Packaging

How retroviruses regulate the amount of RNA genome packaged into each virion has remained a long-standing question. Our previous study showed that most HIV-1 particles contain two copies of viral RNA, indicating that the number of genomes packaged is tightly regulated. In this report, we examine the mechanism that controls the number of RNA genomes encapsidated into HIV-1 particles. We hypothesize that HIV-1 regulates genome packaging by either the mass or copy number of the viral RNA. These two distinct mechanisms predict different outcomes when the genome size deviates significantly from that of wild type. Regulation by RNA mass would result in multiple copies of a small genome or one copy of a large genome being packaged, whereas regulation by copy number would result in two copies of a genome being packaged independent of size. To distinguish between these two hypotheses, we examined the packaging of viral RNA that was larger (≈17 kb) or smaller (≈3 kb) than that of wild-type HIV-1 (≈9 kb) and found that most particles packaged two copies of the viral genome regardless of whether they were 17 kb or 3 kb. Therefore, HIV-1 regulates RNA genome encapsidation not by the mass of RNA but by packaging two copies of RNA. To further explore the mechanism that governs this regulation, we examined the packaging of viral RNAs containing two packaging signals that can form intermolecular dimers or intramolecular dimers (self-dimers) and found that one self-dimer is packaged. Therefore, HIV-1 recognizes one dimeric RNA instead of two copies of RNA. Our findings reveal that dimeric RNA recognition is the key mechanism that regulates HIV-1 genome encapsidation and provide insights into a critical step in the generation of infectious viruses.     

Spatial and temporal density dependence regulates the condition of central Baltic Sea clupeids: compelling evidence using an extensive international acoustic survey

For the first time an international acoustic survey dataset covering three decades was used to investigate the factors shaping the spatial and temporal patterns in the condition of sprat and herring in the Baltic Proper. Generalized additive models showed that the spatial and temporal fluctuations in sprat density have been the main drivers of the spatio-temporal changes of both sprat and herring condition, evidencing intra- and inter-specific density dependence mediated by the size and distribution of the sprat population. Salinity was also an important predictor of herring condition, whereas temperature explained only a minor part of sprat model deviance. Herring density was an additional albeit weak significant predictor for herring condition, evidencing also intra-specific density dependence within the herring population. For both species, condition was high and similar in all areas of the Baltic Proper until the early 1990s, coincident with low sprat densities. Afterwards, a drop in condition occurred and a clear south–north pattern emerged. The drop in condition after the early 1990s was stronger in the northern areas, where sprat population increased the most. We suggest that the increase in sprat density in the northern areas, and the consequent spatial differentiation in clupeid condition, have been triggered by the almost total disappearance of the predator cod from the northern Baltic Proper. This study provides a step forward in understanding clupeid condition in the Baltic Sea, presenting evidence that density-dependent mechanisms also operate at the spatial scale within stock units. This stresses the importance of spatio-temporal considerations in the management of exploited fish.