Modeling Sustainability of Arctic Communities: An Interdisciplinary Collaboration of Researchers and Local Knowledge Holders

How will climate change affect the sustainability of Arctic villages over the next 40 years? This question motivated a collaboration of 23 researchers and four Arctic communities (Old Crow, Yukon Territory, Canada; Aklavik, Northwest Territories, Canada; Fort McPherson, Northwest Territories, Canada; and Arctic Village, Alaska, USA) in or near the range of the Porcupine Caribou Herd. We drew on existing research and local knowledge to examine potential effects of climate change, petroleum development, tourism, and government spending cutbacks on the sustainability of four Arctic villages. We used data across eight disciplines to develop an Arctic Community Synthesis Model and a Web-based, interactive Possible Futures Model. Results suggested that climate warming will increase vegetation biomass within the herd’s summer range. However, despite forage increasing, the herd was projected as likely to decline with a warming climate because of increased insect harassment in the summer and potentially greater winter snow depths. There was a strong negative correlation between hypothetical, development-induced displacement of cows and calves from utilized calving grounds and calf survival during June. The results suggested that climate warming coupled with petroleum development would cause a decline in caribou harvest by local communities. Because the Synthesis Model inherits uncertainties associated with each component model, sensitivity analysis is required. Scientists and stakeholders agreed that (1) although simulation models are incomplete abstractions of the real world, they helped bring scientific and community knowledge together, and (2) relationships established across disciplines and between scientists and communities were a valuable outcome of the study. Additional project materials, including the Web-based Possible Futures Model, are available at http://www.taiga.net/sustain.     

Seasonal Variation of Antifouling Activities of Marine Algae from the Brittany Coast (France)

The antifouling activity of extracts (aqueous, ethanol, and dichloromethane) of 9 marine macroalgae against bacteria, fungi, diatoms, macroalgal spores, mussel phenoloxidase activity, and barnacle cypris larvae has been investigated in relation to season in bimonthly samples from the Bay of Concarneau (France). Of the extracts tested, 48.2% were active against at least one of the fouling organisms, and of these extracts, 31.2% were seasonally active with a peak of activity in summer corresponding to maximal values for water temperature, light intensity, and fouling pressure, and 17% were active throughout the year. This seasonal activity may be adaptive as it coincides with maximal fouling pressure in the Bay of Concarneau. Dichloromethane extracts of Rhodophyceae were the most active in the antifouling assays.     

Abl-dependent tyrosine phosphorylation of Sos-1 mediates growth-factor-induced Rac activation

The non-receptor tyrosine kinase Abl participates in receptor tyrosine kinase (RTK)-induced actin cytoskeleton remodelling, a signalling pathway in which the function of Rac is pivotal. More importantly, the activity of Rac is indispensable for the leukaemogenic ability of the BCR-Abl oncoprotein. Thus, Rac might function downstream of Abl and be activated by it. Here, we elucidate the molecular mechanisms through which Abl signals to Rac in RTK-activated pathways. We show that Sos-1, a dual guanine nucleotide-exchange factor (GEF), is phosphorylated on tyrosine, after activation of RTKs, in an Abl-dependent manner. Sos-1 and Abl interact in vivo, and Abl-induced tyrosine phosphorylation of Sos-1 is sufficient to elicit its Rac-GEF activity in vitro. Genetic or pharmacological interference with Abl (and the related kinase Arg) resulted in a marked decrease in Rac activation induced by physiological doses of growth factors. Thus, our data identify the molecular connections of a pathway RTKs-Abl-Sos-1-Rac that is involved in signal transduction and actin remodelling.     

A test of the CoHR motif associated with meiotic double-strand breaks in Saccharomyces cerevisiae

Meiotic recombination is not random along chromosomes; rather, there are preferred regions for initiation called hotspots. Although the general properties of meiotic hotspots are known, the requirements at the DNA sequence level for the determination of hotspot activity are still unclear. The sequence of six known hotspots in Saccharomyces cerevisiae was compared to identify a common homology region (CoHR). They reported that the locations of CoHR sequences correspond to mapped double-strand break (DSB) sites along three chromosomes (I, III, VI). We report here that a deletion of CoHR at HIS2, a hotspot used to identify the motif, has no significant effect on recombination. In the absence of CoHR, DSB formation occurs at a high frequency and at the same sequences as in wild-type strains. In cases where the deletion of sequences containing the CoHR motif has been shown to reduce recombination, we propose that it may be a reflection of the location of the deletion, rather than the loss of CoHR, per se.     

The complex life of simple sphingolipids

The extensive diversity of membrane lipids is rarely appreciated by cell and molecular biologists. Although most researchers are familiar with the three main classes of lipids in animal cell membranes, few realize the enormous combinatorial structural diversity that exists within each lipid class, a diversity that enables functional specialization of lipids. In this brief review, we focus on one class of membrane lipids, the sphingolipids, which until not long ago were thought by many to be little more than structural components of biological membranes. Recent studies have placed sphingolipids-including ceramide, sphingosine and sphingosine-1-phosphate-at the centre of a number of important biological processes, specifically in signal transduction pathways, in which their levels change in a highly regulated temporal and spatial manner. We outline exciting progress in the biochemistry and cell biology of sphingolipids and focus on their functional diversity. This should set the conceptual and experimental framework that will eventually lead to a fully integrated and comprehensive model of the functions of specific sphingolipids in regulating defined aspects of cell physiology.     

Structure-function evolution of the Transforming acidic coiled coil genes revealed by analysis of phylogenetically diverse organisms

Background  

Examination of ancient gene families can provide an insight into how the evolution of gene structure can relate to function. Functional homologs of the evolutionarily conserved transforming acidic coiled coil (TACC) gene family are present in organisms from yeast to man. However, correlations between functional interactions and the evolution of these proteins have yet to be determined.     

Analysis of in vivo and in vitro DNA strand breaks from trihalomethane exposure

BACKGROUND: Epidemiological studies have linked the consumption of chlorinated surface waters to an increased risk of two major causes of human mortality, colorectal and bladder cancer. Trihalomethanes (THMs) are by-products formed when chlorine is used to disinfect drinking water. The purpose of this study was to examine the ability of the THMs, trichloromethane (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and tribromomethane (TBM), to induce DNA strand breaks (SB) in (1) CCRF-CEM human lymphoblastic leukemia cells, (2) primary rat hepatocytes (PRH) exposed in vitro, and (3) rats exposed by gavage or drinking water. METHODS: DNA SB were measured by the DNA alkaline unwinding assay (DAUA). CCRF-CEM cells were exposed to individual THMs for 2 hr. Half of the cells were immediately analyzed for DNA SB and half were transferred into fresh culture medium and incubated for an additional 22 hr before testing for DNA SB. PRH were exposed to individual THMs for 4 hr then assayed for DNA SB. F344/N rats were exposed to individual THMs for 4 hr, 2 weeks, and to BDCM for 5 wk then tested for DNA SB. RESULTS: CCRF-CEM cells exposed to 5- or 10-mM brominated THMs for 2 hr produced DNA SB. The order of activity was TBM>DBCM>BDCM; TCM was inactive. Following a 22-hr recovery period, all groups had fewer SB except 10-mM DBCM and 1-mM TBM. CCRF-CEM cells were found to be positive for the GSTT1-1 gene, however no activity was detected. No DNA SB, unassociated with cytotoxicity, were observed in PRH or F344/N rats exposed to individual THMs. CONCLUSION: CCRF-CEM cells exposed to the brominated THMs at 5 or 10 mM for 2 hr showed a significant increase in DNA SB when compared to control cells. Additionally, CCRF-CEM cells exposed to DBCM and TBM appeared to have compromised DNA repair capacity as demonstrated by an increased amount of DNA SB at 22 hr following exposure. CCRF-CEM cells were found to be positive for the GSTT1-1 gene, however no activity was detected. No DNA SB were observed in PRH or F344/N rats exposed to individual THMs.     

Effect of a juvenile hormone analogue on lipid metabolism in a wing-polymorphic cricket: implications for the endocrine-biochemical bases of life-history trade-offs

The wing-polymorphic cricket, Gryllus firmus, has a flight-capable morph (LW[f]: long winged with functional flight muscles) and a flightless morph (SW: short winged with reduced nonfunctional flight muscles) that differ genetically in many aspects of lipid metabolism. To determine whether these differences result from genetically based alterations in endocrine regulation, the juvenile hormone mimic, methoprene, was applied to the LW(f) morph. This hormone manipulation converted the LW(f) morph into a SW phenocopy with respect to all aspects of lipid metabolism studied; that is, methoprene application decreased in vivo biosynthesis of total lipid and triglyceride, increased absolute and relative biosynthesis of phospholipid, increased oxidation of fatty acids, and decreased in vitro specific activities of each of six lipogenic enzymes and a transaminase. Furthermore, methoprene increased ovarian growth and decreased fat body mass and flight muscle mass in the LW(f) morph. Differences in each of these biochemical, morphological, or reproductive traits between hormone-treated and control LW(f) females were similar in magnitude to differences between unmanipulated LW(f) and SW females. Variation in endocrine regulation contributes significantly to genetically based differences in lipid metabolism between LW(f) and SW females. This is the first evidence for endocrine regulation of a genetically based life-history trade-off operating via hormonal effects on specific metabolic pathways and enzymes of intermediary metabolism.