Interaction of benzo[a]pyrene, 2,3,3′,4,4′,5 hexachlorobiphenyl (PCB 156) and cadmium on biomarker responses in flounder (Platichthys flesus L.)

Interactive effects of a mixed pollutant exposure on biomarker responses were studied in European flounder (Platichthys flesus L.). The model chemicals, benzo[a]pyrene (BaP, 2.5 mg kg^-1), 2,3,3′,4,4′5 hexachlorobiphenyl (PCB-156, 2.5 mg kg^-1), and cadmium (cadmium, 1 mg kg^-1), were administered to fish by subcutaneous injections. Biomarker responses were quantified both following administration of single chemicals and sequential combinations of the chemicals in pairs. Significant induction of CYP1A protein levels and corresponding ethoxyresorufin-O-deethylase (EROD) activities was observed in BaP and PCB treated flounder after 2 and 8 days, respectively. The strongest induction (44 fold) was caused by BaP. No further induction was observed after additional treatment with PCB 156. CYP1A induction caused by BaP was inhibited (40% compared with BaP treatment alone) in flounder pre treated with cadmium, whereas induction by PCB 156 appeared to be unaffected by pre treatment with cadmium. Flounder treated with cadmium only had significantly elevated hepatic levels of metallothionein (MT) after 15 days. Pre treatment with BaP and PCB prior to cadmium inhibited the MT induction (30-50%) compared with cadmium alone. Furthermore, significantly higher glutathione S transferase activities were observed in flounder administered cadmium alone, and in flounder treated with BaP or PCB 156 prior to cadmium. GST selenium independent peroxidase activities appeared to be unaffected by any of the treatments in the present study. The results indicate that chemical mixtures may affect biomarker responses differently from compounds administered alone, and that the sensitivity of both CYP1A and MT are influenced by pollutants other than their primary inducers.     

Purification and properties of the germination-inducing factor in the ectomycorrhizal fungus Leccinum aurantiacum (Boletaceae)

A diffusion gradient bioassay on agar strips was developed for determination of the germination-inducing activity of exudates from mycelium of Leccinum aurantiacum (Bull.) S. F. Gray on basidiospores of the same species. The taxon-specific germination-inducing factor, GIF, present in the active exudates, was non-volatile, diffusible, soluble in water, methanol and ethanol, resistant to boiling of short duration, and stable after lyophilization if preserved at −20°C. Gel filtration and adsorption experiments contributed to the chemical and physical characterization of GIF. Passage of an exudate through a Sep-Pak C₁₈ minicolumn removed 99.5% of concomitant substances including germination inhibitors. GIF could then be eluted from the column with methanol without loss of activity.     

Clostridium perfringens invasiveness is enhanced by effects of theta toxin upon PMNL structure and function: The role of leukocytotoxicity and expression of CD11/CD18 adherence glycoprotein

Abstract Clostridium perfringens infections are characterized by the lack of an inflammatory response at the site of infection and rapidly progressive margins of tissue necrosis. Studies presented here investigated the role of theta toxin from C. perfringens in the pathophysiology of these events. Mice passively immunized with neutralizing monoclonal antibody against theta toxin and challenged with an LD₁₀₀ of log phase C. perfringens had significantly less mortality than untreated controls. Intramuscular injection of killed, washed C. perfringens in mice induced a massive time-dependent influx of polymorphonuclear leukocytes (PMNL) into tissue; injection of either viable, washed C. perfringens or killed organisms plus theta toxin dramatically attenuated PMNL influx although PMNL accumulated in adjacent vessels. The anti-inflammatory effects could not be attributed to an absence of chemoattractants since C. perfringens proteins had chemotactic factor activity, and killed bacilli generated serum-derived chemotactic factors. Scanning and transmission electron microscopy demonstrated the dramatic leukocidal effects of high doses of theta toxin on PMNL. In contrast, sublethal concentrations of theta toxin primed PMNL chemiluminescence, disrupted PMNL cytoskeletal actin polymerization/disassembly, and stimulated functional upregulation of CD11b/CD18 adherence glycoprotein. In summary, these results demonstrate that theta toxin is an important virulence factor in C. perfringens infection. In a concentration-dependent fashion, theta toxin contributes to the pathogenesis of clostridial gangrene by direct destruction of host inflammatory cells and tissues, and by promoting dysregulated PMNL/endothelial cell adhesive interactions.     

Evolution of the self-pollinating flower in Clarkia xantiana (Onagraceae). I. Size and development of floral organs

Clarkia xantiana has two subspecies that differ in breeding system: ssp. xantiana, which is outcrossing, and ssp. parviflora, which is self-fertilizing. Outcrossing is the ancestral breeding system for the genus Clarkia. Flowers of ssp. parviflora have characteristics commonly associated with selfing taxa: they are smaller and have little temporal and spatial separation between mature anthers and stigma (dichogamy and herkogamy, respectively). Flower morphology and development were studied in four populations of each subspecies to establish the developmental changes that occurred in the evolution of selfing. In particular, we sought to evaluate the hypothesis that the selfing flower may have arisen as a byproduct of selection for rapid maturation in the arid environment occupied by ssp. parviflora. This hypothesis predicts that development time should be reduced in spp. parviflora relative to ssp. xantiana. We also sought to compare the pattern of covariation of flower morphology and development between subspecies to that within subspecies. Similar within vs. between patterns of covariation could be indicative of developmental or functional constraints on the independent evolution of floral parts. In spite of significant variation among populations within subspecies, the subspecies clearly differ in flower morphology and development. All floral organs, except ovaries, are smaller in ssp. parviflora than in ssp. xantiana. The flower plastochron, the duration of flower development from bud initiation to anthesis, and the duration of protandry are all shorter in ssp. parviflora than in ssp. xantiana. Maximum relative growth rates are higher for all organs in ssp. parviflora than in ssp. xantiana. Thus, progenesis (i.e., via a reduction in development time) is combined with growth acceleration in the evolution of the selfing flower. Since reduced development time and growth acceleration both allow selfing flowers to mature earlier than outcrossing ones, selection for early maturation may have contributed to the evolution of the selfing flower form. The pattern of trait covariation differs within spp. parviflora relative to the patterns within spp. xantiana and between the two subspecies, suggesting that floral parts can and have evolved independently of one another.     

The evolution of plant-insect mutualisms

Mutualisms (cooperative interactions between species) have had a central role in the generation and maintenance of life on earth. Insects and plants are involved in diverse forms of mutualism. Here we review evolutionary features of three prominent insect-plant mutualisms: pollination, protection and seed dispersal. We focus on addressing five central phenomena: evolutionary origins and maintenance of mutualism; the evolution of mutualistic traits; the evolution of specialization and generalization; coevolutionary processes; and the existence of cheating. Several features uniting very diverse insect-plant mutualisms are identified and their evolutionary implications are discussed: the involvement of one mobile and one sedentary partner; natural selection on plant rewards; the existence of a continuum from specialization to generalization; and the ubiquity of cheating, particularly on the part of insects. Plant-insect mutualisms have apparently both arisen and been lost repeatedly. Many adaptive hypotheses have been proposed to explain these transitions, and it is unlikely that any one of them dominates across interactions differing so widely in natural history. Evolutionary theory has a potentially important, but as yet largely unfilled, role to play in explaining the origins, maintenance, breakdown and evolution of insect-plant mutualisms.     

Contribution of newly grown extramatrical ectomycorrhizal mycelium and fine roots to soil respiration in a young Norway spruce site

Background and aims

Partitioning of soil respiration is a challenging task when resolving the C cycling in forest ecosystems. Our aim was to partition the respiration of newly grown extramatrical ectomycorrhizal mycelium (ECM) and fine roots (and their associated microorganisms) in a young Norway spruce forest.

Methods

Ingrowth mesh bags of 16 cm diameter and 12 cm height were placed in the upper soil and left for 12–16 months in 2010 and 2011. The 2 mm mesh size allowed the ingrowth of ECM and fine roots whereas a 45 μm mesh size allowed only the ingrowth of ECM. The mesh bags were filled with either homogenized EA horizon soil, pure quartz sand (QS) or crushed granite (CG, only 2011), each with five replicates. Controls without any ingrowth were established for each substrate by solid plastic tubes (2010) and by 1 μm mesh bags (2011). Fluxes of CO₂ from the mesh bags and controls were measured biweekly during the growing season by the closed chamber method.

Results

The contribution of ECM to soil respiration was largest in the QS treatments, reaching cumulatively 1.2 and 2.2 Mg C ha^?1 6 months^?1 in 2010 and 2011, respectively. For EA and CG treatments, the cumulative respiration from ECM was larger than from controls, however the differences being not statistically significant. The respiration of newly grown fine roots in QS amounted to 1.0 Mg C ha^?1 in 2010, but could not be identified in 2011 since fluxes from 2 mm and 45 μm mesh bags were similar. The correlation of total root length in single QS mesh bags to CO₂ fluxes was poor. The contribution of fine root respiration was also not detectable in the EA and CG treatment. No correlation was found between the autumnal biomass of newly grown ECM and its cumulative respiration.

Conclusion

Our results suggest a substantial contribution of newly grown ECM to soil respiration. Respiration of ECM might be larger than respiration of fine roots.