Influence of water-level fluctuation duration and magnitude on sediment–water nutrient exchange in coastal wetlands

This study examined the influence of water-level fluctuation (WLF) on sediment–water nutrient exchange in the Laurentian Great Lakes. Water levels in the Laurentian Great Lakes have been below the long-term mean for the past 15 years, causing the exposure of sediments that previously have been either continuously inundated or periodically exposed. The magnitude, duration, and frequency of WLF, as well as land-use history, each can influence the amount and type of sediment–water nutrient exchange. We collected sediment cores from relatively pristine coastal wetlands located on Beaver and Garden Islands in northern Lake Michigan. Sediment cores were taken from different water depths to simulate WLF magnitude; desiccation time was experimentally manipulated to simulate WLF duration. At these relatively pristine wetlands, desiccation time and water depth significantly influenced flux. However, nutrient exchange did not behave in a consistent fashion; phosphorus, nitrate, ammonium, and sulfate flux varied based on sediment exposure history and desiccation time. Sediment–water nutrient exchange rates also were compared to prior measurements taken from more impacted coastal wetlands in southern Lake Michigan and Saginaw Bay in Lake Huron. This comparison revealed a stronger influence of anthropogenic stress than desiccation time, with impacted wetland sediments releasing more soluble reactive phosphorus, sulfate, and ammonium, and retaining more nitrate, than pristine wetlands. Our results indicate that WLFs have the potential to influence sediment–water nutrient exchange, which may influence system productivity, but environmental context can override this influence.     

Antibodies designed as effective cancer vaccines

Antigen/antibody complexes can efficiently target antigen presenting cells to allow stimulation of the cellular immune response. Due to the difficulty of manufacture and their inherent instability complexes have proved inefficient cancer vaccines. However, anti-idiotypic antibodies mimicking antigens have been shown to stimulate both antibody and T cell responses. The latter are due to T cell mimotopes expressed within the complementarity-determining regions (CDRs) of antibodies that are efficiently presented to dendritic cells in vivo. Based on this observation we have designed a DNA vaccine platform called ImmunoBody™, where cytotoxic T lymphocyte (CTL) and helper T cell epitopes replace CDR regions within the framework of a human IgG1 antibody. The ImmunoBody™ expression system has a number of design features which allow for rapid production of a wide range of vaccines. The CDR regions of the heavy and light chain have been engineered to contain unique restriction endonuclease sites, which can be easily opened, and oligonucleotides encoding the T cell epitopes inserted. The variable and constant regions of the ImmunoBody™ are also flanked by restriction sites, which permit easy exchange of other IgG subtypes. Here we show a range of T cell epitopes can be inserted into the ImmunoBody™ vector and upon immunization these T cell epitopes are efficiently processed and presented to stimulate high frequency helper and CTL responses capable of anti-tumor activity.Key words: DNA vaccines, cancer vaccines, melanoma, CTL, helper T cells     

Electrophysiological and biochemical responses of mouse vomeronasal receptor cells to urine-derived compounds: possible mechanism of action

Receptor cells of the vomeronasal organ (VNO) are thought to detect pheromone-like molecules important for reproductive physiology. Several compounds derived from male mouse urine have been demonstrated to affect endocrine events in female mice. In the present study, the ability of these compounds to affect VNO activity was tested. In dissociated VNO cells held under voltage clamp conditions, application of dehydro-exo-brevicomin (DHB) evoked an outward current at negative holding potentials and an inward current at positive holding potentials. Under current clamp, DHB reduced action potential firing. Since DHB application caused a decrease in membrane conductance, this compound appeared to act by reducing inward current through closing an ion channel. Biochemical experiments tested the effects of DHB and 2- (sec-butyl)-4,5-dihydrothiazole (SBT) on cAMP levels in the VNO. A mixture of DHB and SBT decreased cAMP levels in VNO sensory tissue and had no effect on VNO non-sensory tissue. The results suggest that pheromones have an inhibitory influence on action potential generation and on cAMP levels in receptor cells of the VNO.      

Phylogenetic analysis of carbamoylphosphate synthetase genes: complex evolutionary history includes an internal duplication within a gene which can root the tree of life

Carbamoylphosphate synthetase (CPS) catalyzes the first committed step in pyrimidine biosynthesis, arginine biosynthesis, or the urea cycle. Organisms may contain either one generalized or two specific CPS enzymes, and these enzymes may be heterodimeric (encoded by linked or unlinked genes), monomeric, or part of a multifunctional protein. In order to help elucidate the evolution of CPS, we have performed a comprehensive phylogenetic analysis using the 21 available complete CPS sequences, including a sequence from Sulfolobus solfataricus P2 which we report in this paper. This is the first report of a complete CPS gene sequence from an archaeon, and sequence analysis suggests that it encodes an enzyme similar to heterodimeric CPSII. We confirm that internal similarity within the synthetase domain of CPS is the result of an ancient gene duplication that preceded the divergence of the Bacteria, Archaea, and Eukarya, and use this internal duplication in phylogenetic tree construction to root the tree of life. Our analysis indicates with high confidence that this archaeal sequence is more closely related to those of Eukarya than to those of Bacteria. In addition to this ancient duplication which created the synthetase domain, our phylogenetic analysis reveals a complex history of further gene duplications, fusions, and other events which have played an integral part in the evolution of CPS.      

The resolution of lymphedema by interstitial flow in the mouse tail skin

Lymphangiogenesis is considered a promising approach for increasing fluid drainage during secondary lymphedema. However, organization of lymphatics into functional capillaries may be dependent upon interstitial flow (IF). The present study was undertaken to determine the importance of lymphangiogenesis for lymphedema resolution. We created a lymphatic obstruction that produces lymphedema in mouse tail skin. The relatively scar-free skin regeneration that occurred across the obstruction allowed the progression of lymphangiogenesis to be observed and compared with the evolution of lymphedema. The role of vascular endothelial growth factor-C (VEGF-C)/VEGF receptor (VEGFR)-3 signaling in lymphedema resolution was investigated by exogenous administration of VEGF-C or neutralizing antibodies against VEGFR-3. VEGF-C protein improved lymphedema at 15 days [reducing dermal thickness from 742 +/- 105 to 559 +/- 141 microm with 95% confidence intervals (CIs), P < 0.05] without increasing lymphatic capillary coverage (11.6 +/- 6.4% following VEGF-C treatment relative to 9.6 +/- 6.2% with 95% CIs, P > 0.50). Blocking VEGFR-3 signaling did not inhibit lymphedema resolution at 25 days (dermal thickness of 462 +/- 127 microm following VEGFR-3 inhibition relative to 502 +/- 87 microm with 95% CIs) or inhibit IF, although VEGFR-3 blocking prevented lymphangiogenesis (reducing lymphatic coverage to 0.2 +/- 0.7% relative to 8.7 +/- 7.3% with 95% CIs, P < 0.005). A second mouse tail lymphedema model was employed to investigate the ability of VEGF-C to increase fluid drainage across a scar. We found that neither neutralization of VEGFR-3 nor administration of VEGF-C affected the course of skin swelling over 25 days. These findings suggest that resolution of lymphedema in the mouse tail skin may be more dependent upon IF and regeneration of the extracellular matrix across the obstruction than lymphatic capillary regeneration.     

Trends in lizard translocations in New Zealand between 1988 and 2013

There is growing concern about mitigation-driven translocations that move animals from anthropogenic threats at donor sites because of their failure rate and lack of application of scientific principles and best practice. We reviewed all known lizard translocations in New Zealand between 1988 and 2013 and identified 85 translocations of 30 lizard taxa to 46 release sites. Most translocations (62%) were motivated by conservation goals for the species or the release site, and one-third were mitigation-driven translocations, typically motivated by habitat loss due to development. Mitigation-driven translocations began in 2003, and since that time have equalled the number of conservation-motivated translocations. Conservation-motivated translocations usually released lizards on islands without mammalian predators, whereas mitigation-driven translocations usually relocated lizards to mainland sites with introduced predators. Long-term monitoring has been sparse and often rudimentary. Eight lizard translocations have recorded population growth, including one mitigation-driven translocation that was into a fenced reserve. Research on commonly used management techniques to mitigate human-related impacts is recommended to establish whether these techniques benefit lizards in the long term.     

The importance of hyporheic sediment respiration in several mid-order Michigan rivers: comparison between methods in estimates of lotic metabolism

Metabolism was measured in four Michigan streams, comparing estimates made using a flow-through chamber designed to include the hyporheic zone to a 20 cm depth and a traditional closed chamber that enclosed to a 5 cm depth. Mean levels of gross primary productivity and community respiration were consistently greater in the flow-through chamber than the closed chamber in all streams. Ratios of productivity to respiration (P/R) were consistently greater in the closed chambers than the flow-through chambers. P/R ratios were consistently <1 in all streams when estimated with flow-through chambers, suggesting heterotrophic conditions. Maintenance of stream ecosystem structure and function therefore is dependent on subsidies either from the adjacent terrestrial system or upstream sources. Our results suggest that stream metabolism studies that rely on extrapolation of closed chambers to the whole reach will most likely underestimate gross primary productivity and community respiration.