Vascular Plant Responses to Elevated CO2 in a Temperate Lowland Sphagnum Peatland

Vascular plant responses to experimental enrichment with atmospheric carbon dioxide (CO₂), using MINIFACE technology, were studied in a Dutch lowland peatland dominated by Sphagnum and Phragmites for 3 years. We hypothesized that vascular plant carbon would accumulate in this peatland in response to CO₂ enrichment owing to increased productivity of the predominant species and poorer quality (higher C/N ratios) and consequently lower decomposability of the leaf litter of these species. Carbon isotope signatures demonstrated that the extra 180 ppmv CO₂ in enriched plots had been incorporated into vegetation biomass accordingly. However, on the CO₂ sequestration side of the ecosystem carbon budget, there were neither any significant responses of total aboveground abundance of vascular plants, nor of any of the individual species. On the CO₂ release side of the carbon budget (decomposition pathway), litter quantity did not differ between ambient and CO₂ treatments, while the changes in litter quality (N and P concentration, C/N and C/P ratio) were marginal and inconsistent. It appeared therefore that the afterlife effects of significant CO₂-induced changes in green-leaf chemistry (lower N and P concentrations, higher C/N and C/P) were partly offset by greater resorption of mobile carbohydrates from green leaves during senescence in CO₂-enriched plants. The decomposability of leaf litters of three predominant species from ambient and CO₂-enriched plots, as measured in a laboratory litter respiration assay, showed no differences. The relatively short time period, environmental spatial heterogeneity and small plot sizes might explain part of the lack of CO₂ response. When our results are combined with those from other Sphagnum peatland studies, the common pattern emerges that the vascular vegetation in these ecosystems is genuinely resistant to CO₂-induced change. On decadal time-scales, water management and its effects on peatland hydrology, N deposition from anthropogenic sources and land management regimes that arrest the early successional phase (mowing, tree and shrub removal), may have a greater impact on the vascular plant species composition, carbon balance and functioning of lowland Sphagnum–Phragmites reedlands than increasing CO₂ concentrations in the atmosphere.     

Penicillin‐binding protein folding is dependent on the PrsA peptidyl‐prolyl cis‐trans isomerase in Bacillus subtilis

The PrsA protein is a membrane‐anchored peptidyl‐prolyl cis‐trans isomerase in Bacillus subtilis and most other Gram‐positive bacteria. It catalyses the post‐translocational folding of exported proteins and is essential for normal growth of B. subtilis. We studied the mechanism behind this indispensability. We could construct a viable prsA null mutant in the presence of a high concentration of magnesium. Various changes in cell morphology in the absence of PrsA suggested that PrsA is involved in the biosynthesis of the cylindrical lateral wall. Consistently, four penicillin‐binding proteins (PBP2a, PBP2b, PBP3 and PBP4) were unstable in the absence of PrsA, while muropeptide analysis revealed a 2% decrease in the peptidoglycan cross‐linkage index. Misfolded PBP2a was detected in PrsA‐depleted cells, indicating that PrsA is required for the folding of this PBP either directly or indirectly. Furthermore, strongly increased uniform staining of cell wall with a fluorescent vancomycin was observed in the absence of PrsA. We also demonstrated that PrsA is a dimeric or oligomeric protein which is localized at distinct spots organized in a helical pattern along the cell membrane. These results suggest that PrsA is essential for normal growth most probably as PBP folding is dependent on this PPIase.     

Short-term exercise affects cardiac function ex vivo partially via changes in calcium channel levels,without influencing hypoxia sensitivity

Journal of Physiology and Biochemistry - Exercise is known to improve cardiac recovery following coronary occlusion. However, whether short-term exercise can improve cardiac function and hypoxia...     

Lipid‐rich zooplankton subsidise the winter diet of benthivorous Arctic charr (Salvelinus alpinus) in a subarctic lake

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Direct and indirect photodynamic therapy effects on the cellular and molecular components of the tumor microenvironment

Photodynamic therapy (PDT) is a novel cancer treatment. It involves the activation of a photosensitizer (PS) with light of specific wavelength, which interacts with molecular oxygen to generate singlet oxygen and other reactive oxygen species (ROS) that lead to tumor cell death. When a tumor is treated with PDT, in addition to affect cancer cells, the extracellular matrix and the other cellular components of the microenvironment are altered and finally this had effects on the tumor cells survival. Furthermore, the heterogeneity in the availability of nutrients and oxygen in the different regions of a tridimensional tumor has a strong impact on the sensitivity of cells to PDT. In this review, we summarize how PDT affects indirectly to the tumor cells, by the alterations on the extracellular matrix, the cell adhesion and the effects over the immune response. Also, we describe direct PDT effects on cancer cells, considering the intratumoral role that autophagy mediated by hypoxia-inducible factor 1 (HIF-1) has on the efficiency of the treatment.     

Isolation and characterization of squamous carcinoma cells resistant to photodynamic therapy

Photodynamic therapy (PDT) employing methyl δ-aminolevulinic acid (Me-ALA), as a precursor of the photosensitizer protoporphyrin IX (PpIX), is used for the treatment of non melanoma cutaneous cancer (NMCC). However, one of the problems of PDT is the apparition of resistant cell populations. The aim of this study was to isolate and characterize squamous carcinoma cells SCC-13 resistant to PDT with Me-ALA. The SCC-13 parental population was submitted to successive cycles of Me-ALA-PDT and 10 resistant populations were finally obtained. In parental and resistant cells there were analyzed the cell morphology (toluidine blue), the intracellular PpIX content (flow cytometry) and its localization (fluorescence microscopy), the capacity of closing wounds (scratch wound assay), the expression of cell-cell adhesion proteins (E-cadherin and β-catenin), cell-substrate adhesion proteins (β1-integrin, vinculin and phospho-FAK), cytoskeleton proteins (α-tubulin and F-actin) and the inhibitor of apoptosis protein survivin, in the activated form as phospho-survivin (indirect immunofluorescence and Western blot). The results obtained indicate that resistant cells showed a more fibroblastic morphology, few differences in intracellular content of the photosensitizer, higher capacity of closing wounds, higher number of stress fibers, more expression of cell-substrate adhesion proteins and higher expression of phospho-survivin than parental cells. These distinctive features of the resistant cells can provide decisive information to enhance the efficacy of Me-ALA applications in clinic dermatology.     

Partial and total fish meal replacement by agricultural products in the diets improve sperm quality in African catfish (Clarias gariepinus)

This study investigated the long-term effects of total and partial replacement of dietary fish meal (FM) by a mixture of agricultural products on sperm quality of African catfish Clarias gariepinus. Four isonitrogenous and isoenergetic diets were formulated containing graded levels of either 50% FM and maize meal (diet 1); 25% FM mixed with crude sunflower oil cake (SFOC) and bean meal (BM) (diet 2); 12.5% FM mixed with sunflower oil cake, BM and ground nut oil cake (GOC) (diet 3) and 0% FM mixed with de-hulled sunflower oil cake (SFOCD), BM and ground nut oil cake (diet 4). Gonadosomatic index (GSI), sperm quality, plasma sex steroids (11-keto testosterone [11-KT]; testosterone [T]; estradiol-17beta [E2]) were evaluated on 10 to 24 fish fed on each diet. Sperm quality was assessed using computer-assisted sperm analysis (CASA). Total replacement of fish meal by plant products markedly increased sperm volume, spermatocrit, spermatozoa integrity, and sperm motility. Fish fed diet 3 (12.5% fish meal) provided intermediate results on sperm quality whereas the lowest values were obtained in fish fed diets 1 and 2. In fish fed 0% fish meal (diet 4), androgen levels were higher and estrogen levels were lower than in fish fed fish meal diets. Based on dietary lipid and fatty acid analyses, these results suggest a positive impact of short chain n-6 fatty acids on androgen synthesis and sperm quality. In conclusion, a combination of ground nut oil cake, bean meal and sunflower oil cake (preferably when the sunflower is dehulled) in African catfish diet improves the sperm quality.     

Production of monocytic cells from bone marrow stem cells: therapeutic usage in Alzheimer's disease

Accumulation of amyloid β (Aβ) is a major hallmark in Alzheimer's disease (AD). Bone marrow derived monocytic cells (BMM) have been shown to reduce Aβ burden in mouse models of AD, alleviating the AD pathology. BMM have been shown to be more efficient phagocytes in AD than the endogenous brain microglia. Because BMM have a natural tendency to infiltrate into the injured area, they could be regarded as optimal candidates for cell-based therapy in AD. In this study, we describe a method to obtain monocytic cells from BM-derived haematopoietic stem cells (HSC). Mouse or human HSC were isolated and differentiated in the presence of macrophage colony stimulating factor (MCSF). The cells were characterized by assessing the expression profile of monocyte markers and cytokine response to inflammatory stimulus. The phagocytic capacity was determined with Aβ uptake assay in vitro and Aβ degradation assay of natively formed Aβ deposits ex vivo and in a transgenic APdE9 mouse model of AD in vivo. HSC were lentivirally transduced with enhanced green fluorescent protein (eGFP) to determine the effect of gene modification on the potential of HSC-derived cells for therapeutic purposes. HSC-derived monocytic cells (HSCM) displayed inflammatory responses comparable to microglia and peripheral monocytes. We also show that HSCM contributed to Aβ reduction and could be genetically modified without compromising their function. These monocytic cells could be obtained from human BM or mobilized peripheral blood HSC, indicating a potential therapeutic relevance for AD.     

Leishmania major: recruitment of Gr-1+ cells into draining lymph nodes during infection is important for early IL-12 and IFN gamma production

The production of interleukin-12 and interferon-γ is a key event for controlling leishmaniasis. Here, we tested the hypothesis that after murine infection with Leishmania major, cell migration into draining lymph nodes is crucial for early production of those cytokines. We showed that inflammatory cells carrying the marker of recently migrated cells, the Gr-1 antigen, including polymorphonuclear and mononuclear cells, migrate rapidly into the site of promastigote infection and, subsequently, into draining lymph nodes. Treatment with RB6-8C5 monoclonal antibody reduced local inflammation and migration of Gr-1+ cells into the draining lymph nodes. This reduction was associated with a decrease of interleukin-12 production by draining lymph node cells from BALB/c mice but not C57BL/6 mice. Additionally, interferon-γ was also reduced in both mouse strains after depletion of Gr-1+ cells, suggesting that these cells are important for early interleukin-12 and interferon-γ production. Our findings suggest that recently migrated myeloid cells, more than resident cells, are the major source of the early IL-12 production after L. major infection.