Transplant experiments. Growth-limiting factors for diatoms and bluegreen algae in Norwegian lakes

Population densities and total phosphorus concentrations in samples from different lakes of south-eastern Norway were determined. In addition some transplant experiments with dilute phytoplankton populations were carried out. A laboratory batch culture method was used.The diatoms studied may be divided into three ecological groups based on their cell densities and total phosphorus concentrations in the samples. This classification was supported by the experimental results. Cyclotella spp., Asterionella formosa and Tabellaria fenestrata did not grow or had low growth rates above pH 9. Synedra cf. acus and Fragilaria crontonensis had often high growth rates within the pH 9–10 range, but were not able to grow at pH values above 10. High pH-values had no effect on the growth rate of Oscillatoria. Oscillatoria, Synedra and Stephanodiscus were severely growth-limited in filtered water from oligotrophic lakes. Maximum growth rates of all the populations studied were often obtained after addition of phosphate and chelated iron (FeEDTA) in combination to filtered water samples from oligotrophic/mesotrophic lakes.     

Identification of identical TCRs in primary melanoma lesions and tumor free corresponding sentinel lymph nodes

It is generally believed that priming of efficient T-cell responses takes place in peripheral lymphoid tissues. Although this notion has been rigidly proven for infectious diseases, direct evidence for lymph node priming of in vivo T-cell responses against tumors is still lacking. In the present study, we conducted a full and nonbiased comparison of T-cell clonotypes in melanoma lesions and corresponding sentinel lymph nodes. Whereas most tumor lesions comprised a high number of T-cell clonotypes, only a small number of clonally expanded T cells were detected in the draining lymph nodes. Comparative clonotype mapping demonstrated the presence of identical T-cell clonotypes in the tumors and the respective sentinel lymph nodes, only when tumor cells were present in the latter. However, taking advantage of clonotype specific PCR amplification, TCR sequences representing clonally expanded T cells at the tumor site could be detected in the lymph nodes draining the tumors even in the absence of tumor cells. Evidence for the tumor-specific characteristics of these cells was obtained by in situ staining with peptide/HLA class I complexes demonstrating the presence of MART-1/HLA-A2- and MAGE-3/HLA-A2-reactive T cells at the tumor site, as well as in the draining lymph node. Our data indicate that T-cell responses to melanoma are primed in the sentinel lymph node by cross presentation of tumor antigens by dendritic cells.     

Novel selective thiazoleacetic acids as CRTH2 antagonists developed from in silico derived hits. Part 1

Structure–activity relationships of three related series of 4-phenylthiazol-5-ylacetic acids, derived from two hits emanating from a focused library obtained by in silico screening, have been explored as CRTH2 (chemoattractant receptor-homologous molecule expressed on Th2 cells) antagonists. Several compounds with double digit nanomolar binding affinity and full antagonistic efficacy for human CRTH2 receptor were obtained in all subclasses. The most potent compound was [2-(4-chloro-benzyl)-4-(4-phenoxy-phenyl)-thiazol-5-yl]acetic acid having an binding affinity of 3.7 nM and functional antagonistic effect of 66 nM in a BRET and 12 nM in a cAMP assay with no functional activity for the other PGD2 DP receptor (27 μM in cAMP).     

Oligosaccharides implicated in recognition are predicted to have relatively ordered structures

Fucosylated O- and N-linked glycans are essential recognition molecules in plants and animals. To understand how they impart their functions, through interactions with proteins, requires a detailed analysis of structure and dynamics, but this is presently lacking. In this study, the three-dimensional structure and dynamics of three fucosylated oligosaccharides are investigated using a combination of high field (800 MHz) nuclear magnetic resonance and long (50 ns) molecular dynamics simulations in explicit water. Predictions from dynamics simulations were in agreement with nuclear Overhauser cross-peak intensities. Similarly, a theory of weak alignment in neutral media resulted in reasonable predictions of residual dipolar couplings for the trisaccharide fucosyllactose. However, for larger penta- and hexasaccharides (LNF-1 and LND-1), the anisotropic component of the alignment was underestimated, attributed to shape irregularities of the fucosyl branches on an otherwise linear core, being more pronounced in a singly branched than a doubly branched oligosaccharide. Simulations, confirmed by experiment, predicted fucosylated molecules that are restricted to librations about a single average conformation. This restriction is partly due to microscopic water interactions, which act to stabilize intramolecular hydrogen bonds and maintain tight and ordered conformations; a view not forthcoming from simpler, nonaqueous simulations. Such a conclusion is crucial for understanding how these molecules interact with proteins and impart their recognition properties.     

Comparative multilocus phylogeography of two Palaearctic spruce bark beetles: influence of contrasting ecological strategies on genetic variation

While phylogeographic patterns of organisms are often interpreted through past environmental disturbances, mediated by climate changes, and geographic barriers, they may also be strongly influenced by species‐specific traits. To investigate the impact of such traits, we focused on two Eurasian spruce bark beetles that share a similar geographic distribution, but differ in their ecology and reproduction. Ips typographus is an aggressive tree‐killing species characterized by strong dispersal, whereas Dendroctonus micans is a discrete inbreeding species (sib mating is the rule), parasite of living trees and a poor disperser. We compared genetic variation between the two species over both beetles’ entire range in Eurasia with five independent gene fragments, to evaluate whether their intrinsic differences could have an influence over their phylogeographic patterns. We highlighted widely divergent patterns of genetic variation for the two species and argue that the difference is indeed largely compatible with their contrasting dispersal strategies and modes of reproduction. In addition, genetic structure in I. typographus divides European populations in a northern and a southern group, as was previously observed for its host plant, and suggests past allopatric divergence. A long divergence time was estimated between East Asian and other populations of both species, indicating their long‐standing presence in Eurasia, prior to the last glacial maximum. Finally, the strong population structure observed in D. micans for the mitochondrial locus provides insights into the recent colonization history of this species, from its native European range to regions where it was recently introduced.     

The occurrence of aerolysin-positive Aeromonas spp. and their cytotoxicity in Norwegian water sources

Aims:  The aim of the study was to investigate the occurrence of Aeromonas spp. and their aerolysin status in Norwegian natural water sources.
Methods and Results:  Seventy-one samples from 33 Norwegian water sources were examined for the presence of Aeromonas spp. From most of the sample sites, the strains were isolated on blood-ampicillin-agar and Difco Aeromonas agar simultaneously. The majority of the samples (73/77) contained Aeromonas spp., with an average of 35–100 cfu 100 ml^–1. The highest counts were found in faecally-contaminated water. Using PCR, 445 isolates were screened for the presence of aerolysin, and 79% of them were found to be carriers of the aerolysin gene. A selection of the isolated strains was tested on Vero cell cultures and 83% of them showed cytotoxicity.
Conclusions:  There is widespread occurrence of aerolysin-positive cytotoxic Aeromonas spp. in many different Norwegian natural waters, including drinking water sources.
Significance and Impact of the Study:  The widespread occurrence of potentially-pathogenic Aeromonas spp. in the environment demands that these bacteria should not be ignored in drinking water supplies and in the food industry.     

Seasonal trends in body mass, food intake and resting metabolic rate, and induction of metabolic depression in arctic foxes (Alopex lagopus) at Svalbard

 Post-absorptive resting metabolic rates (RMRs), body mass and ad libitum food intake were recorded on an annual cycle in captive arctic foxes (Alopex lagopus) at Svalbard. During the light season in May and in the dark period in November, RMR during starvation and subsequent re-feeding were also measured. In contrast to earlier findings, the present study indicated a seasonal trend in post-absorptive RMR (in W · kg⁻¹ and W · kg^−0.75). The values in the light summer were 15% and 11% higher than the values in the dark winter, suggesting a physiological adaptation aiding energy conservation during winter in arctic foxes. Body mass and ad libitum food intake varied inversely through the year. A significant reduction in RMR (in W and W · kg^−0.75) with starvation (metabolic depression) was recorded both in May and November, indicating an adaptation to starvation in arctic foxes. The lack of metabolic depression during a period of starvation that was concomitant with extremely cold ambient temperatures in November 1994 indicates that metabolic responses to starvation may be masked by thermoregulatory needs. At very low ambient temperatures, arctic foxes may require increased heat production which cannot be achieved via below-average rates of metabolism. Accepted: 7 June 1999     

Evolutionarily distinctive species often capture more phylogenetic diversity than expected

Evolutionary distinctiveness measures of how evolutionarily isolated a species is relative to other members of its clade. Recently, distinctiveness metrics that explicitly incorporate time have been proposed for conservation prioritization. However, we found that such measures differ qualitatively in how well they capture the total amount of evolution (termed phylogenetic diversity, or PD) represented by a set of species. We used simulation and simple graph theory to explore this relationship with reference to phylogenetic tree shape. Overall, the distinctiveness measures capture more PD on more unbalanced trees and on trees with many splits near the present. The rank order of performance was robust across tree shapes, with apportioning measures performing best and node-based measures performing worst. A sample of 50 ultrametric trees from the literature showed the same patterns. Taken together, this suggests that distinctiveness metrics may be a useful addition to other measures of value for conservation prioritization of species. The simplest measure, the age of a species, performed surprisingly well, suggesting that new measures that focus on tree shape near the tips may provide a transparent alternative to more complicated full-tree approaches.     

Can ant‐eating Zodarion spiders (Araneae: Zodariidae) develop on a diet optimal for euryphagous arthropod predators?

Abstract Little attention is paid to the behavioural and physiological adaptations of ant‐eating predators. It is expected that there should be a strong selection for traits related to prey handling, leading to the evolution of morphological, behavioural and nutritional adaptations. Such adaptations may then entail trade‐offs in handling and utilization of alternative prey. To investigate behavioural as well as nutritional adaptations and the occurrence of the corresponding trade‐offs in two ant‐eating spiders of the genus Zodarion [Zodarion atlanticum Pekár & Cardoso and Zodarion germanicum (C. L. Koch)], spiders are reared on two diets: ants (i.e. their preferred prey) and fruit flies (i.e. an alternative prey that is nutritionally optimal for euryphagous spiders). Food consumption is observed and several fitness‐related life‐history parameters are measured. Although spiders readily accept ants, more than one‐third of 35 spiders refuse to consume fruit flies and starve. Furthermore, severe hunger does not induce these individuals to accept fruit flies. Starving spiders die before moulting to the second stadium. Spiders that eat fruit flies increase only little and slowly in weight, and all of these die during the first two stadia. By contrast, spiders on an ant diet increase dramatically in weight, and develop up to the fourth stadium. These data indicate that fruit flies are not suitable for Zodarion, supporting the hypothesis that there are behavioural and nutritional trade‐offs. Taking into account the results of previous studies, it is suggested that nutritional trade‐offs are generally important for stenophagous spiders.