Emended descriptions of indole negative and indole positive isolates of Brachyspira (Serpulina) hyodysenteriae

Two type/reference strains of Brachyspira (B.) hyodysenteriae, 14 Belgian and German indole negative, and 14 Belgian, German and Swedish indole positive field isolates of strongly β-haemolytic intestinal spirochaetes were compared by pulsed-field gel electrophoresis (PFGE) patterns, biochemical reaction patterns, 16S rDNA sequences and MIC determinations of six antibacterial substances. Three tests for indole production, including a spot indole test, were compared with congruent results. All field isolates were classified as B. hyodysenteriae due to a high genetic and phenotypic similarity with the type strains. The Belgian and German indole negative isolates had identical and unique PFGE patterns for the tested restriction enzymes MluI and SalI, as well as identical 16S rDNA sequences, and they could not be differentiated by any of the methods used. Seven unique PFGE patterns were achieved from the 14 indole positive field isolates. The patterns were identical and unique for epidemiologically related isolates. Type/reference strains and isolates without known relation to other tested isolates showed unique banding patterns. The MICs of tylosin, tiamulin, erythromycin, clindamycin, carbadox and virginiamycin were determined in broth for all isolates. In contrast to Belgian and German isolates, the majority of the Swedish field isolates were susceptible to tylosin, erythromycin and clindamycin. Probable pathways of infection for some of the Swedish isolates were determined. The PFGE patterns of epidemic clones of B. hyodysenteriae remained stable for a period of up to 8 years. In vivo development of resistance to macrolide and lincosamide antibiotics due to use of tylosin was clearly indicated for two epidemic clones.     

Reactivity of secondary hydroxyl groups in methylβ-d-xylopyranoside toward aβ-o-4-type quinone methide

Methyl-d-xylopyranoside was allowed to react with-O-4-type quinone methide without a catalyst to elucidate the reactivities of secondary hydroxyl groups at the C2, C3, and C4 positions. Benzyl ether-type lignin-carbohydrate complex (LCC) compounds linked at the C2 and C4 positions were predominant, at a ratio of 23. However, the reactivity of the hydroxyl group at the C3 position was quite low. These results strongly suggest that the reactivity of the C2 hydroxyl group in xylan toward quinone methide intermediate is higher than that of the C3 hydroxyl group during biosynthesis of LCCs.     

Growth and mortality in underplanted tree seedlings in response to variations in canopy closure of Norway spruce stands

Six broadleaved tree species and Picea abies (L.) Karst. wereplanted under spruce plantations of varying densities, in Sweden.Treatments included control (994 stems ha^–1), dense (538stems ha^–1), sparse (294 stems ha^–1) and gap (0stems ha^–1) overstory treatments. There was an increasein height and diameter growth from control to sparse overstorytreatment of all underplanted tree species except for ash (Fraxinusexcelsior L.) and Norway maple (Acer platanoides L.). Site conditionsmay have hampered the growth of these species, as well as wildcherry (Prunus avium L.). Both oak (Quercus robur L.) and sprucehad greater growth in the gap treatment, relative to the othertreatments. Insecticide application did not influence seedlinggrowth or survival. The performance of beech (Fagus sylvaticaL.), lime (Tilia cordata Mill.), spruce and oak was consistentwith shade tolerance ranking. Beech and lime had a very highsurvival rate, even under the densest canopy. The growth andmortality of ash, maple and wild cherry differed significantlyfrom what was expected. This experiment demonstrated significantvariation in interspecific growth and mortality between sevenplanted tree species in relation to canopy density. Correctsite and species selection is crucial when underplanting inshelterwood systems.     

Impacts of seasonal air and soil temperatures on photosynthesis in Scots pine trees

Seasonal courses of light-saturated rate of net photosynthesis (A360) and stomatal conductance (gs) were examined in detached 1-year-old needles of Scots pine (Pinus sylvestris L.) from early April to mid-November. To evaluate the effects of soil frost and low soil temperatures on gas exchange, the extent and duration of soil frost, as well as the onset of soil warming, were manipulated in the field. During spring, early summer and autumn, the patterns of A360 and gs in needles from the control and warm-soil plots were generally strongly related to daily mean air temperatures and the frequency of severe frost. The warm-soil treatment had little effect on gas exchange, although mean soil temperature in the warm-soil plot was 3.8 degrees C higher than in the control plot during spring and summer, indicating that A360 and gs in needles from control trees were not limited by low soil temperature alone. In contrast, prolonged exposure to soil temperatures slightly above 0 degrees C severely restricted recovery of A360 and especially gs in needles from the cold-soil treatment during spring and early summer; however, full recovery of both A360 and gs occurred in late summer. We conclude that inhibition of A360 by low soil temperatures is related to both stomatal closure and effects on the biochemistry of photosynthesis, the relative importance of which appeared to vary during spring and early summer. During the autumn, soil temperatures as low as 8 degrees C did not affect either A360 or gs.     

LH-β and FSH-β mRNA expression in nesting and post-breeding three-spined stickleback, Gasterosteus aculeatus, and effects of castration on expression of LH-β, FSH-β and spiggin mRNA

The mRNA expression of the LH- and FSH- subunits were measured in nesting and post-breeding male three-spined sticklebacks, Gasterosteus aculetaus, as well as in castrated and sham-operated nesting males. Furthermore, expression of an androgen induced kidney protein, spiggin, and 11-ketotestosterone (11KT) levels, were measured in the castrated and sham-operated males. Nesting males had significantly higher levels of both LH- and FSH- mRNA expression compared to post-breeding males. Furthermore, sham-operated males had significantly higher levels of LH- mRNA and spiggin mRNA expression than the castrated fish. Expression of FSH-, on the other hand, did not differ between castrated and sham-operated males. There were strong positive individual correlations between circulating levels of 11KT on the one hand and expressions of LH- and spiggin mRNA, whereas the correlation between 11KT levels and FSH- mRNA was weak. The negative effect of castration on -LH mRNA indicates that gonadal hormones stimulate this expression, whereas this was not the case for -FSH. The observed decline in -LH expression after the end of the breeding season may be the result of cessation of the gonadal stimulation of the pituitary. On the other hand, it is not likely that this can explain the decline in FSH- expression.     

Identifying the biological effects of pre-commercial thinning on diameter growth in young Scots pine stands

Data from seven Scots pine (Pinus sylvestris L.) stands in central Sweden that had undergone pre-commercial thinning (PCT) were used to investigate the biological effect of PCT on the diameter at breast height (DBH) growth of the remaining trees. Two treatments were considered: a PCT treatment and a control (C) with no PCT. The DBH of the trees in each stand was measured on up to four occasions over 15 years. We examined mean DBH and DBH growth of the largest 300, 600, 900 and 1200 trees ha^?1. Two methods of selecting the trees used to calculate the mean DBH values for each measurement occasion were considered: the actual mean DBH (Dma), which is based on the DBH distribution of the trees on the measurement occasion in question, and the genuine mean DBH (Dmg), which is based on the DBH distribution of the trees on the final measurement occasion of the study and therefore focuses on the same set of trees for all measurement occasions. There was no clear difference between the Dma- and Dmg-based DBH increments, but the Dmg values tended to be somewhat larger both for the C and PCT treatments. Over a 15-year period, the relative mean yearly increments (Dma/Dmg) for different tree size classes ranged from 0.91 to 0.98, with lower values for the C treatment and larger DBH size classes. We found that PCT promotes DBH growth: over a 15-year period, the increased growth amounted to about 2.0 mm year^?1 compared to the trees in unthinned plots.     

Changes in arterial PO₂, physiological blood parameters and intracellular antioxidants in free-swimming Atlantic cod (Gadus morhua) exposed to varying levels of hyperoxia

Free-swimming Atlantic cod (Gadus morhua) were exposed to water oxygen pressures (P _wO₂) ranging from 18.1 to 41.5 kPa and sampled for blood using an indwelling caudal artery cannula. Arterial blood oxygen pressure (P _aO₂) increased with increasing P _wO₂, from 12.0 kPa in normoxia (18.1 kPa) to 34.2 kPa in the highest hyperoxic level tested (41.5 kPa). Blood CO₂ pressure and plasma bicarbonate concentration increased with P _wO₂, indicating reduced ventilation with increased P _wO₂. Plasma glucose, sodium and potassium were not affected by water oxygen level. Blood oxidative stress biomarkers, reduced glutathione, oxidized glutathione and the oxidative stress index (ratio between oxidized and total glutathione) differed intermittently between normoxia and hyperoxia. The oxidative stress index was higher in the blood of exposed compared to unexposed control cod. Together with elevated P _aO₂, these findings suggest increased production of reactive oxygen species and increased oxidative stress in Atlantic cod exposed to hyperoxia.     

Characterisation of agricultural drainage ditch sediments along the phosphorus transfer continuum in two contrasting headwater catchments

Purpose

This study investigated the phosphorus (P) source, mobilisation and transport potential of ditch bed sediments as well as surrounding field and bank soils in two agricultural headwater catchments with contrasting soil drainage capacities. This information is important for discerning the potential for ditches to attenuate or augment transfers of P from upstream sources and thus for developing appropriate management strategies for these features.

Materials and methods

Phosphorus sources were characterised using the Mehlich3-P, water-soluble P and total P tests. Phosphorus mobilisation potential was characterised using the Mehlich3-AL/P, Mehlich3-Ca/P and DESPRAL P tests. Phosphorus transport potential was characterised using data collected on the presence/absence of surface water in ditches during field surveys and downstream turbidity data.

Results and discussion

Ditch sediments had similar P source contents (Mehlich3-P, water-soluble P and total P) to the surrounding field soils and higher P contents than bank soils. However, calcium contents of sediments in the poorly drained catchment reflected the deep sub-soils rather than the surrounding field and bank soils. Mehlich3-Al/P and Mehlich3-Ca/P contents of ditch sediments in the well (non-calcareous) and poorly (calcareous) drained catchments respectively indicated potential for P retention (above thresholds of 11.7 and 74, respectively). However, sediments were less aggregated than field soils and may mobilise more particulate P (PP) during rain events. Nevertheless, the majority of surveyed ditches dried out from March to September 2011; thus, their potential to mobilise PP may be less important than their capacity to attenuate soluble and PP during this time.

Conclusions

In these and similar catchments, soluble P attenuation and particulate P mobilisation should be maximised and minimised, respectively, for example, by cleaning out the sediments before they become saturated with P and encouraging vegetation growth on ditch beds. This study also highlighted the influence of deep sub-soils on soluble P retention in ditches and thus the utility of characterising soils below depths normally included in soil classifications.

     

Element (Ag, Cd, Cu, Pb, Sb, Tl and Zn), element ratio and lead isotope profiles in a sediment affected by a mining operation episode during the late 19th century

Mining operations at Mårsätter in 1877–81 resulted in increased metal loading to a small lake, notably as sulphidic tailings. The event is taken as an opportunity to study the present environmental impact of a historical single major metal release. Lake water and four sediment cores were sampled and analysed for principal and trace elements in solid and aqueous phases as well as general hydrochemical conditions. Chronologies were determined from ²⁰⁶Pb/²⁰⁷Pb ratios and historical records. Ordinary sedimentation after the event has lead to that the tailings are found as a distinct layer at a depth of 18–22 cm in the sediment. The layer is characterized by elevated metal concentrations in the solid and pore water phases, respectively, circum neutral pH and sulphate concentrations below detection. Geochemical modelling indicated a preference for carbonate equilibrium in the waste while sulphides prevailed above it. It is concluded that the growth of the ordinary sediment on top of the waste has lead to a physicochemical barrier that seals of the waste from the overlying sediment. Chemical or physical rupture of the barrier will release the metals to downstream regions. According to the chronologies at least three sources have contributed to the present elevated levels of metals, in additions to the release of tailings. Copper from a historical blast furnace prior to the event at Mårsätter, transport from mineralized parts of the watershed and release of contaminated water from present mining operations maintain elevated levels of notably zinc, silver, cadmium and lead. At present less than 10% of the lead content at the sediment/water interface comes from atmospheric deposition. Increased levels of antimony and thallium were not observed prior to ca 1950.