Potential effects of elevated atmospheric carbon dioxide on benthic autotrophs and consumers in stream ecosystems: a test using experimental stream mesocosms

Elevated atmospheric carbon dioxide (eCO₂) has been shown to have a variety of ecosystem‐level effects in terrestrial systems, but few studies have examined how eCO₂ might affect aquatic habitats. This limits broad generalizations about the effects of a changing climate across biomes. To broaden this generalization, we used free air CO₂ enrichment to compare effects of eCO₂ (i.e., double ambient ～720 ppm) relative to ambient CO₂ (aCO₂～360 ppm) on several ecosystem properties and functions in large, outdoor, experimental mesocosms that mimicked shallow sand‐bottom prairie streams. In general, we showed that eCO₂ had strong bottom‐up effects on stream autotrophs, which moved through the food web and indirectly affected consumer trophic levels. These general effects were likely mediated by differential CO₂ limitation between the eCO₂ and aCO₂ treatments. For example, we found that eCO₂ decreased water‐column pH and increased dissolved CO₂ in the mesocosms, reducing CO₂‐limitation at times of intense primary production (PP). At these times, PP of benthic algae was about two times greater in the eCO₂ treatment than aCO₂ treatment. Elevated PP enhanced the rate of carbon assimilation relative to nutrient uptake, which reduced algae quality in the eCO₂ treatment. We predicted that reduced algae quality would negatively affect benthic invertebrates. However, density, biomass and average individual size of benthic invertebrates increased in the eCO₂ treatment relative to aCO₂ treatment. This suggested that total PP was a more important regulator of secondary production than food quality in our experiment. This study broadens generalizations about ecosystem‐level effects of a changing climate by providing some of the first evidence that the global increase in atmospheric CO₂ might affect autotrophs and consumers in small stream ecosystems throughout the southern Great Plains and Gulf Coastal slope of North America.     

Carbon dioxide enrichment reduces shoot growth in sweet chestnut seedlings (Castanea sativa Mill.)*

Abstract. Two-year-old potted sweet chestnut seedlings were grown at 350 ppm CO₂ and 700 ppm, day and night in constantly ventilated tunnels during two full growing seasons, near Paris, France (48° N, 2° E). Enrichment with CO₂ caused an unusual shoot growth response. After the end of July, stem elongation ceased in 62% of the CO₂ enriched plants as compared with 37% in the control. The leaves of CO₂-enriched seedlings showed early senescence, indicated by premature yellowing and a decrease in chlorophyll content. This was associated with nutrient dilution brought about by the rapid growth of these trees. The increase in total dry weight of the CO₂-enriched seedlings was essentially the result of increase in the root dry weight (69%). Shoot weight decreased by 22% relative to the control. Total leaf area per enriched plant was 25% smaller than the control. This unusual pattern of growth and carbon allocation of the CO₂ treated Chestnut trees emphasizes the concept of a response specificity within trees to an increase of atmospheric CO₂.     

A simple stepwise procedure of deriving selection index with restrictions

Summary A simplified alternative procedure was derived for computing selection indices with various restrictions. The procedure involved construction of a sub-index for the unrestricted traits by the conventional methods (Smith-Hazel index approach) and construction of a sub-index for the restricted traits based on the restrospective index approach. The two subindices were then combined to obtain the desired index which met the prespecified restriction. The formulation is straightforward and easy to compute and does not involve the complicated formula as does the derivation of restricted index by the use of the Lagrange multiplier method. As a consequence of simplification, the proposed procedure is approximate in terms of optimal gain in net merit. The procedure presented can also be extended to derive an index with simultaneous imposition of multiple restrictions. Numerical examples were given to illustrate the use of this alternative approach.Animal Research Centre Contribution No. 1251     

Characterizing disease-associated changes in post-translational modifications by mass spectrometry

Introduction: Exploring post-translational modifications (PTMs) with the use of mass spectrometry (PTMomics) is a rapidly developing area, with methods for discovery/quantification being developed and advanced on a regular basis. PTMs are highly important for the regulation of protein function, interaction and activity, both in physiological and disease states. Changes in PTMs can either cause, or be the result of a disease, making them central for biomarker studies and studies of disease pathogenesis. Recently, it became possible to study multiple PTMs simultaneously from low amount of sample material, thereby increasing coverage of the PTMome obtainable from a single sample. Thus, quantitative PTMomics holds great potential to discover biomarkers from tissue and body fluids as well as elucidating disease mechanisms through characterization of signaling pathways.

Areas covered: Recent mass spectrometry-based methods for assessment of the PTMome, with focus on the most studied PTMs, are highlighted. Furthermore, both data dependent and data independent acquisition methods are evaluated. Finally, current challenges in the field are discussed.

Expert commentary: PTMomics holds great potential for clinical and biomedical research, especially with the generation of spectral libraries of peptides and PTMs from individual patients (permanent PTM maps) for use in personalized medicine.     

Ilizarov method in combination with autologous mesenchymal stem cells from iliac crest shows improved outcome in tibial non-union

Autologous bone grafting and ilizarov technique are the preferred mode of treatment for bone nonunion, studies suggest that bone marrow derived mesenchymal stem cells can be effective in treatment of tibial non-union where there is length of bone defect. The current study investigates the beneficial clinical outcome of combining the ilizarov procedure with intraosseous injection of autologous mesenchymal stem cells. The open-label study enrolled 25 patients with infected tibial non-union at the Shanghai Fengxian District Central Hospital, Shanghai, China between April 2010 and July 2014. Patients were randomised to undergo the ilizarov procedure with (n = 11) or without (n = 13) intraosseous injection of bone marrow derived mesenchymal stem cells. All participants were followed prospectively until union was achieved (primary end point). The mean length of the bone defect in the Ilizarov group and Ilizarov group plus MSC group was 6.09 and 5.84 cm respectively. The mean time from the original injury to the time of the treatment for tibial non-union was 5–22 months (mean 13.5 months) for the Ilizarov group and 6–21 months (mean 13.5 months) for Ilizarov plus MSc group. All 24 patients were followed up for 12–34 months (mean 16 months). Both groups achieved the primary endpoint of stable union of the tibial fracture. No adverse events were observed in any of the group. Our study demonstrates that using autologous bone marrow derived mesenchymal stem cell as an add-on therapy to the ilizarov procedure shows significant clinical benefit in fixation of tibial non-union.