Revision of the plant geographical territories of Israel and Sinai

The phytogeographical territories of Israel and Sinai are revised using a large mass of species distribution data. With the help of chorotype frequencies for 25 km² individual squares in Israel, territories were defined on the basis of the first two most frequent chorotypes. The similarity of boundaries in the resulting phytogeographical map with a physiognomic map suggests that the latter may be used in preliminary stages of the preparation of plant geographical maps.     

Meiotic behavior of an unequal bivalent in the grasshopper Calliptamus palaestinensis Bdhr.

Summary Unequal bivalents were found in two of four populations of the short horned grasshopper, Calliptamus palaestinensis bdhr. sampled in Israel.The inequality of the homologues was due to an extra segment which was heterochromatic and apparently terminal. Pairing configurations at pachytene and position of chiasmata at later stages revealed however that the extra segment was interstitial, and the long member terminated in a minute segment homologous to the terminal part of its normal partner. The percentage of reductional divisions at anaphase I corresponded well with the percentage of terminal chiasmata (i.e. distal to the extra segment) observed at diakinesis.The assumption of an interstitial position of the extra segment would explain the previously puzzling examples of unequal bivalents in Orthoptera whose reductional divisions have not been readily accounted for otherwise.     

Comparison of cytoplasmic superoxide dismutase in liver,heart and brain of aging rats and mice

Comparisons of the specific activity of cytoplasmic superoxide dismutase, in homogenates of liver, brain and heart demonstrate considerably reduced activity in livers of aging rats and mice, a very small reduction in specific activity in the heart and no reduction in the brain of aging animals.Antisera elicited in rabbits against purified superoxide dismutase from liver of either young or old rats revealed complete cross-reactivity with the heart and brain enzymes. They also exhibited complete cross-reactivity with the mouse enzymes from all three organs. This finding has, for the first time, enabled a comparison of possible age-dependent alterations in the same enzyme antigen in different cell types.Despite the differences in age-related changes in specific activity in homogenates of liver, heart and brain the enzyme shows a considerable decline in catalytic activity per antigenic unit in $\text{all}$ three organs in both aging rats and mice.     

Ethnic groups and high sensitivity C-reactive protein in Israel

Abstract

High-sensitivity C-reactive protein (hs-CRP) is a biomarker that correlates with atherothrombotic risk and outcome. hs-CRP is influenced by various modifiable and non-modifiable factors. We studied the relationship between ethnic background and hs-CRP level, among the Jewish population in Israel. A total of 3659 men and 2180 women were divided into two ethnic groups (Ashkenazi and Sephardic Jews), based on the knowledge of Jewish immigration patterns throughout the centuries. Mean hs-CRP levels were calculated for each group and were adjusted for various factors known to influence hs-CRP. Sephardic Jews were found to have higher adjusted mean hs-CRP levels (2.0 mg l^?1 for men and 3.9 mg l^?1 for women) compared with Ashkenazi Jews (1.5 mg l^?1 for men and 2.9 mg l^?1 for women). Ethnic background emerged as an independent significant predictor of hs-CRP levels. We demonstrated that ethnicity is an important factor when considering hs-CRP as a marker of atherothrombotic risk.     

Extinction debt in a common grassland species: immediate and delayed responses of plant and population fitness

Changes in landscape structure and environmental conditions due to habitat fragmentation can have significant effects on plant populations. Decreasing genetic diversity and changing population structure can reduce plant fitness and influence the long-term persistence of populations. Dry calcareous grasslands in Estonia have witnessed a large decline in area within the last 80 years, but due to extinction debt, the species richness in these grasslands has not yet responded to this decline. In these calcareous grasslands, we studied genetic diversity, phenotypic performance and population characteristics of a common habitat-specialist grass, Briza media. A decrease in genetic diversity was associated with a decrease in plant reproductive output. In addition, we found that some fitness components of B. media showed a delayed response to landscape changes. Specifically, plant height and germination success were related to historical rather than to current landscape parameters, indicating a time-lagged response of plant performance to habitat fragmentation. Dependence on historical landscape structure may thus result in a future decline in population fitness even if habitat loss and fragmentation no longer continue. The documented effect of current environmental conditions, however, shows that fitness-related traits are already slowly adapting to the changing conditions. Our results indicate that even common habitat-specialist species can be susceptible to landscape changes and be threatened by decreased population performance in the future.     

Novel Galanin Receptor Subtype Specific Ligand in Depression Like Behavior

Neuropeptide galanin and its three receptors, galanin receptor type 1–galanin receptor type 3, are known to be involved in the regulation of numerous psychological processes, including depression. Studies have suggested that stimulation of galanin receptor type 2 (GalR2) leads to attenuation of the depression-like behavior in animals. However, due to the lack of highly selective galanin subtype specific ligands the involvement of different receptors in depression-like behavior is yet not fully known. In the present study we introduce a novel GalR2 selective agonist and demonstrate its ability to produce actions consistent with theorized GalR2 functions and analogous to that of the anti-depressant, imipramine.     

Measuring carbon and N2 fixation in field populations of colonial and free‐living unicellular cyanobacteria using nanometer‐scale secondary ion mass spectrometry1

Unicellular cyanobacteria are now recognized as important to the marine N and C cycles in open ocean gyres, yet there are few direct in situ measurements of their activities. Using a high‐resolution nanometer scale secondary ion mass spectrometer (nanoSIMS), single cell N₂ and C fixation rates were estimated for unicellular cyanobacteria resembling N₂ fixer Crocosphaera watsonii. Crocosphaera watsonii‐like cells were observed in the subtropical North Pacific gyre (22°45′ N, 158°0′ W) as 2 different phenotypes: colonial and free‐living. Colonies containing 3–242 cells per colony were observed and cell density in colonies increased with incubation time. Estimated C fixation rates were similarly high in both phenotypes and unexpectedly for unicellular cyanobacteria 85% of the colonial cells incubated during midday were also enriched in ¹⁵N above natural abundance. Highest ¹⁵N enrichment and N₂ fixation rates were found in cells incubated overnight where up to 64% of the total daily fixed N in the upper surface waters was attributed to both phenotypes. The colonial cells retained newly fixed C in a sulfur‐rich matrix surrounding the cells and often cells of both phenotypes possessed areas (<1 nm) of enriched ¹⁵N and ¹³C resembling storage granules. The nanoSIMS imaging of the colonial cells also showed evidence for a division of N₂ and C fixation activity across the colony where few individual cells (<34%) in a given colony were enriched in both ¹⁵N and ¹³C above the colony average. Our results provide new insights into the ecophysiology of unicellular cyanobacteria.     

Structure,dynamics, and stability of the globular domain of human linker histone H1.0 and the role of positive charges

Linker histone H1 (H1) is an abundant chromatin‐binding protein that acts as an epigenetic regulator binding to nucleosomes and altering chromatin structures and dynamics. Nonetheless, the mechanistic details of its function remain poorly understood. Recent work suggest that the number and position of charged side chains on the globular domain (GD) of H1 influence chromatin structure and hence gene repression. Here, we solved the solution structure of the unbound GD of human H1.0, revealing that the structure is almost completely unperturbed by complex formation, except for a loop connecting two antiparallel β‐strands. We further quantified the role of the many positive charges of the GD for its structure and conformational stability through the analysis of 11 charge variants. We find that modulating the number of charges has little effect on the structure, but the stability is affected, resulting in a difference in melting temperature of 26 K between GD of net charge +5 versus +13. This result suggests that the large number of positive charges on H1‐GDs have evolved for function rather than structure and high stability. The stabilization of the GD upon binding to DNA can thus be expected to have a pronounced electrostatic component, a contribution that is amenable to modulation by posttranslational modifications, especially acetylation and phosphorylation.     

Comparative analysis detects dependencies among the 5' splice-site positions

Human-mouse comparative genomics is an informative tool to assess sequence functionality as inferred from its conservation level. We used this approach to examine dependency among different positions of the 5' splice site. We compiled a data set of 50,493 homologous human-mouse internal exons and analyzed the frequency of changes among different positions of homologous human-mouse 5' splice-site pairs. We found mutual relationships between positions +4 and +5, +5 and +6, -2 and +5, and -1 and +5. We also demonstrated the association between the exonic and the intronic positions of the 5' splice site, in which a stronger interaction of U1 snRNA and the intronic portion of the 5' splice site compensates for weak interaction of U1 snRNA and the exonic portion of the 5' splice site, and vice versa. By using an ex vivo system that mimics the effect of mutation in the 5' splice site leading to familial dysautonomia, we demonstrated that U1 snRNA base-pairing with positions +6 and -1 is the only functional requirement for mRNA splicing of this 5' splice site. Our findings indicate the importance of U1 snRNA base-pairing to the exonic portion of the 5' splice site.     

Ragweed plants and airborne pollen in the Baltic states

Presence of pollen in the atmosphere was determined inTartu in 1989–1997, in Kuressaare in 1996–1997 and iniauliai in 1997. Ragweed airpollen was found in latesummer in three years. The distribution, abundance andflowering of local ragweed plants were estimated. Itappeared that the number of local sources did notexceed twenty per country per year. Majority of thesesources consisted of a small number of pollinating A. artemisiifolia individuals. The largest localsources, consisting of several hundreds ofindividuals, were exclusively rare. Transport ofragweed pollen by air masses from distant sources wasstudied. It was found that incursions of ragweedpollen were determined by air fluxes originating fromthe Ukraine as well as from the southeastern andsouthern regions of the European part of Russia. Theseincursions occurred in extensive high-pressure areaswhose centre was located in the central region of theEuropean part of Russia with a periphery extending tothe Baltic countries.