Effects of experimental warming on arctic willows (Salix spp.): a comparison of responses from the Canadian High Arctic, Alaskan Arctic, and Swedish Subarctic

Three species of dwarf, prostrate willow ( Salix arctica , S. rotundifolia and S. herbacea ) were subjected to experimental summer warming in high arctic Canada, arctic Alaska, and subarctic Sweden, respectively, as part of the International Tundra Experiment. Phenological and growth responses of these species were compared for the second season of the experiment. Stigmas became receptive and pollen dispersal occurred significantly earlier for S. rotundifolia and S. herbacea in the ITEX open-top chambers, but not for S. arctica . Warming had no effect on the timing of seed dispersal, leaf yellowing, or leaf senescence. The length and dry weight of the largest leaves were greater for warmed plants, and was significant for S. rotundifolia . The number of catkins/plot did not differ among species or treatments, but the fruit : flower ratio was reduced in the experimental plots.     

Time- and concentration-dependent effects of resveratrol in HL-60 and HepG2 cells

Resveratrol, a phytochemical present in grapes, has been demonstrated to inhibit tumourigenesis in animal models. However, the specific mechanism by which resveratrol exerts its anticarcinogenic effect has yet to be elucidated. In the present study, the inhibitory effects of resveratrol on cell proliferation and apoptosis were evaluated in the human leukaemia cell line HL-60 and the human hepatoma derived cell line HepG2. We found that after a 2 h incubation period, resveratrol inhibited DNA synthesis in a concentration-dependent manner. The IC50 value was 15 microm in both HL-60 and HepG2 cells. When the time of treatment was extended, an increase in IC50 value was observed; for example, at 24 h the IC50 value was 30 microm for HL-60 cells and 60 microm for HepG2 cells. Flow cytometry revealed that cells accumulated in different phases of the cell cycle depending on the resveratrol concentration. Furthermore, an increase in nuclear size and granularity was observed in the G1 and S phases of HL-60 treated and HepG2-treated cells. Apoptosis was also stimulated by resveratrol in a concentration-dependent manner in HL-60 and HepG2 cells. In conclusion, resveratrol inhibits cell proliferation in a concentration- and time-dependent manner by interfering with different stages of the cell cycle. Furthermore, resveratrol treatment causes stimulation of apoptosis as well as an increase in nuclear size and granularity.     

Stable intermediates determine proteins' primary unfolding sites in the presence of surfactants

Despite detailed knowledge of the overall structural changes and stoichiometries of surfactant binding, little is known about which protein regions constitute the preferred sites of attack for initial unfolding. Here we have exposed three proteins to limited proteolysis at anionic (SDS) and cationic (DTAC) surfactant concentrations corresponding to specific conformational transitions, using the surfactant‐robust broad‐specificity proteases Savinase and Alcalase. Cleavage sites are identified by SDS‐PAGE and N‐terminal sequencing. We observe well‐defined cleavage fragments, which suggest that flexibility is limited to certain regions of the protein. Cleavage sites for α‐lactalbumin and myoglobin correspond to regions identified in other studies as partially unfolded at low pH or in the presence of organic solvents. For Tnfn3, which does not form partially folded structures under other conditions, cleavage sites can be rationalized from the structure of the protein's folding transition state and the position of loops in the native state. Nevertheless, they are more sensitive to choice of surfactant and protease, probably reflecting a heterogeneous and fluctuating ensemble of partially unfolded structures. Thus, for proteins accumulating stable intermediates on the folding pathway, surfactants encourage the formation of these states, while the situation is more complex for proteins that do not form these intermediates. © 2008 Wiley Periodicals, Inc. Biopolymers 91: 221–231, 2009. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Population genetic structure of North Atlantic, Mediterranean Sea and Sea of Cortez fin whales, Balaenoptera physalus (Linnaeus 1758): analysis of mitochondrial and nuclear loci

Samples were collected from 407 fin whales, Balaenoptera physalus , at four North Atlantic and one Mediterranean Sea summer feeding area as well as the Sea of Cortez in the Pacific Ocean. For each sample, the sex, the sequence of the first 288 nucleotides of the mitochondrial (mt) control region and the genotype at six microsatellite loci were determined. A significant degree of divergence was detected at all nuclear and mt loci between North Atlantic/Mediterranean Sea and the Sea of Cortez. However, the divergence time estimated from the mt sequences was substantially lower than the time elapsed since the rise of the Panama Isthmus, suggesting occasional gene flow between the North Pacific and North Atlantic ocean after the separation of the two oceans. Within the North Atlantic and Mediterranean Sea, significant levels of heterogeneity were observed in the mtDNA between the Mediterranean Sea, the eastern (Spain) and the western (the Gulf of Maine and the Gulf of St Lawrence) North Atlantic. Samples collected off West Greenland and Iceland could not be unequivocally assigned to either of the two areas. The homogeneity tests performed using the nuclear data revealed significant levels of divergence only between the Mediterranean Sea and the Gulf of St Lawrence or West Greenland. In conclusion, our results suggest the existence of several recently diverged populations in the North Atlantic and Mediterranean Sea, possibly with some limited gene flow between adjacent populations, a population structure which is consistent with earlier population models proposed by Kellogg, Ingebrigtsen, and Sergeant.     

Fine Needle Aspiration Cytodiagnosis of Subacute (De Quervain's) Thyroiditis In an Endemic Goitre Area

Between 1977 and 1989 252 fine needle aspirates (FNAs) of the thyroid from patients with a clinical suspicion of subacute granulomatous (de Quervain's) thyroiditis were examined in the Department of Pathology of the University of Innsbruck, Austria. In the same period 31 cases with preoperative FNA were diagnosed histologically as subacute thyroiditis. Only in three of these cases were the cytological features of de Quervain's thyroiditis found in the preoperative FNA. However, in 13 of these 31 cases a cytological suspicion of malignancy was obtained. Subsequent histological examination revealed an acute phase inflammation of de Quervain's thyroiditis in most of these cases. We conclude that an accurate FNA diagnosis of de Quervain's thyroiditis, particularly in the acute stage, may cause difficulties due to a lack of typical features and the appearance of atypical thyroid follicular cells. For the cytopathologist, accurate clinical information relating to the possibility of de Quervain's thyroiditis is essential if unnecessary surgery is to be avoided.     

Actin mutations in hypertrophic and dilated cardiomyopathy cause inefficient protein folding and perturbed filament formation

Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) are the most common hereditary cardiac conditions. Both are frequent causes of sudden death and are often associated with an adverse disease course. Alpha-cardiac actin is one of the disease genes where different missense mutations have been found to cause either HCM or DCM. We have tested the hypothesis that the protein-folding pathway plays a role in disease development for two actin variants associated with DCM and six associated with HCM. Based on a cell-free coupled translation assay the actin variants could be graded by their tendency to associate with the chaperonin TCP-1 ring complex/chaperonin containing TCP-1 (TRiC/CCT) as well as their propensity to acquire their native conformation. Some variant proteins are completely stalled in a complex with TRiC and fail to fold into mature globular actin and some appear to fold as efficiently as the wild-type protein. A fraction of the translated polypeptide became ubiquitinated and detergent insoluble. Variant actin proteins overexpressed in mammalian cell lines fail to incorporate into actin filaments in a manner correlating with the degree of misfolding observed in the cell-free assay; ranging from incorporation comparable to wild-type actin to little or no incorporation. We propose that effects of mutations on folding and fiber assembly may play a role in the molecular disease mechanism.