Dynamics of phosphatase activities in a cork oak litter (Quercus suber L.) following sewage sludge application

As part of a study of the processes involved in litter biodegradation following sewage sludge (SS) addition, the variations over 14 months of phosphatase activities in a cork oak litter (Quercus suber L.) were investigated. A field experimental design was carried out using the litter-bag method on both a fertilized plot receiving SS applications (twice ) and a control plot. Acid (APH) and alkaline (BPH) phosphatases were measured, along with several biotic and abiotic variables potentially involved in the regulation of these enzymes. These included moisture, temperature, pH, water-extractable inorganic P (P_W), culturable heterotrophic bacteria and fungi. Sludge addition had significant effects on all the variables measured. Indeed, sludge increased significantly BPH activities, available P_W, microbial densities (i.e. bacteria and fungi) and pH in the fertilized plot. In contrast, APH activities decreased significantly following sludge addition. As a consequence, the BPH/APH ratio increased markedly and immediately in the fertilized plot, but only after the 1st amendment. Following the 1st preconditioning SS amendment, the 2nd fertilization had fewer effects on biological variables, because of summer dryness. The different properties examined varied significantly with incubation time, and most were significantly related to the seasonal patterns of litter moisture in this Mediterranean forest ecosystem. Hence, sewage sludge application modified the intensity of microbial responses to environmental factors, but biological patterns regulating P turn-over were maintained.     

Segmentation applied to weather-disease relationships in South American leaf blight of the rubber tree

South American leaf blight (SALB) is a severe threat to world rubber production. One way of controlling it is to set up plantations in zones not conducive to the disease. Such zones are known once a plantation has been set up, but few data are available on how climate affects the disease, especially in the Amazon region. With better knowledge of conditions that are favourable to SALB epidemics it would be possible to more accurately identify risk zones in Asia and Africa, continents that are still SALB-free. Based on a trial design involving detailed and frequent observations, and with a method rarely used in plant epidemiology, the segmentation method, the results presented in this article make it possible to list, in order of importance, climatic factors that influence disease severity under conditions where the climate varies little over the year.     

Detection of parathyroid hormone-related protein in cats with humoral hypercalcemia of malignancy

Background — Increased serum parathyroid hormone‐related peptide (PTHrP) concentration is used to diagnose humoral hypercalcemia of malignancy (HHM) in humans and animals. A commercially available assay for human PTHrP has diagnostic utility in the dog, but has not been assessed in cats. Objectives — The goals of this study were to determine serum or plasma levels of PTHrP in a population of hypercalcemic cats and to determine whether increased PTHrP concentration was associated with malignancy. In addition, we validated immunoradiometric assays (IRMAs) for intact parathormone (iPTH) and PTHrP for use with feline samples. Methods — A retrospective analysis of iPTH and PTHrP results from 322 hypercalcemic cats (ionized calcium concentration >1.4 mmol/L) was performed. Immunoassays for human iPTH and PTHrP (residues 1–84) were validated using standard methods, and reference intervals were calculated using values from 31 healthy adult cats. Hypercalcemic cats were classified as parathyroid‐independent (iPTH <2.3 pmol/L), equivocal (iPTH 2.3–4.6 pmol/L), or parathyroid‐dependent (iPTH >4.6 pmol/L). Seven cats with detectable or increased PTHrP concentrations were evaluated further for underlying disease. Formalin‐fixed neoplastic tissues were immunohistochemically stained using rabbit antibody to human midregion PTHrP. Results — Assays for iPTH and PTHrP showed acceptable precision for feline samples. The reference interval for iPTH was 0.8–4.6 pmol/L and for PTHrP was <1.5 pmol/L. The majority of hypercalcemic cats (263/322, 81.7%) were parathyroid‐independent, with fewer cats in the equivocal (32/322,9.9%) and parathyroid‐dependent (27/322,8.4%) groups. In 31 (9.6%) cats, PTHrP concentration was >1.5 pmol/L (range 1.5–26.6 pmol/L). All 7 cats for which follow‐up information was available had HHM; 6 had carcinomas (4 lung carcinomas, 1 undifferentiated carcinoma, 1 thyroid carcinoma) and 1 had lymphoma. All tumors had mild to moderate positive staining for PTHrP; however, lung carcinomas from normocalcemic cats also stained positive. Conclusions — Human IRMA for PTHrP (1–84) can be used to measure PTHrP in cats. Malignancies, particularly carcinomas, appear to secrete PTHrP and induce HHM in this species. Immunohistochemistry alone cannot predict the occurrence of HHM in cats.     

Discovery of symbiotic nitrogen-fixing cyanobacteria in corals

Colonies of the Caribbean coral Montastraea cavernosa exhibit a solar-stimulated orange-red fluorescence that is spectrally similar to a variety of fluorescent proteins expressed by corals. The source of this fluorescence is phycoerythrin in unicellular, nonheterocystis, symbiotic cyanobacteria within the host cells of the coral. The cyanobacteria coexist with the symbiotic dinoflagellates (zooxanthellae) of the coral and express the nitrogen-fixing enzyme nitrogenase. The presence of this prokaryotic symbiont in a nitrogen-limited zooxanthellate coral suggests that nitrogen fixation may be an important source of this limiting element for the symbiotic association.     

Migration behaviour and escapement of European silver eels from a large lake and wetland system subject to water level management (Grand‐Lieu Lake,France): New insights from regulated acoustic telemetry data

Current knowledge about the downstream migration of sexually mature European eels (Anguilla anguilla) remains incomplete, particularly in still water habitats such as lakes and wetlands subject to water level management. However, for the management of this endangered species, it is important to understand migration dynamics, and contribution to the breeding stock. This study aimed to assess the parameters that trigger and guide the migration of silver eels in the largest floodplain lake and associated wetlands in France (the sluice regulated Grand‐Lieu Lake). A telemetry survey of 50 acoustic and PIT‐tagged female silver eels was performed during the 2015–2016 migration period. We deployed a novel telemetric approach, using receivers to delimit several restricted virtual boxes to determine the instantaneous location of individuals and to transform simple discrete telemetric data into presence/absence data. The low numbers leaving the lake centre are probably explained by the lack of orienting water flows or other environmental clues, but whilst the fate of 34% (17/50) of the tagged eels is unknown, 18% (9/50) were caught by commercial fishermen. Modelling showed that detections were not clearly associated with environmental factors typically involved in riverine migrations (e.g. current velocity, atmospheric pressure and temperature) but they were particularly associated with higher and increasing water levels and, for eels exiting the lake, a sharp increase when sluice gates were opened to an effective gap of >75 cm. It is concluded that management of water levels and sluice gate opening during the migration period might aid escapement of silver eels.     

Does antimony affect microbial respiration in Mediterranean soils? A microcosm experiment

The aim of this study was to determine the effects of antimony on soil microbial respiration. Two Mediterranean calcareous soils were sampled: a contaminated soil close to an abandoned lead and silver smelter and a soil far from the pollution source and considered not to be contaminated. Two forms of antimony, antimony trioxide (Sb₂O₃) and potassium antimonyl tartrate trihydrate (C₈H₄K₂O₁₂Sb₁₂·3H₂O), were tested at three concentrations (50, 500 and 5000 ppm) in controlled conditions under short- (3 days) and medium- (3 months) term incubation. Modifications in the substrate-induced respiration (SIR) were assessed by gas chromatography respirometric measurements. Results clearly showed that SIR was immediately and significantly more affected by Sb input in a non-contaminated soil than in a long-term contaminated soil, especially since the concentration was high and Sb was added to a more soluble and available form (tartrate instead of mineral oxide).     

Mass marking of stocked European glass eels (Anguilla anguilla) with alizarin red S

This study describes a mass marking method suitable for European glass eel Anguilla anguilla, avoiding osmotic shock and reducing fish stress. During a single day, 360,000 glass eels intended for a stocking operation were bathed into an alizarin red S (ARS) solution, at a density of 346 ind.·l^?1 before being released into a freshwater marsh along with unmarked glass eels. After 15 days, examination of marked and unmarked eels kept in enclosures in the marsh showed 100% of otoliths had been successfully marked and that no excess deaths related to marking process had occurred. Seven months after stocking, results from biometric measurements and otolith analysis, carried out on a sample of 53 elvers caught by electrofishing and belonging to the size class of the 0⁺ cohort, suggest that: (i) the proportions of marked and unmarked remained unchanged, hence suggesting that the marking process had not caused excess mortality, (ii) there was no difference in length, body mass or condition factor between marked and unmarked individuals, demonstrating that marking had caused no harmful effect after 7 months, and (iii) ARS marks in otoliths remained clearly visible. The benefits of this ARS mass marking technique are discussed through a stocking operation.     

Raman-assisted crystallography reveals end-on peroxide intermediates in a nonheme iron enzyme

Iron-peroxide intermediates are central in the reaction cycle of many iron-containing biomolecules. We trapped iron(III)-(hydro)peroxo species in crystals of superoxide reductase (SOR), a nonheme mononuclear iron enzyme that scavenges superoxide radicals. X-ray diffraction data at 1.95 angstrom resolution and Raman spectra recorded in crystallo revealed iron-(hydro)peroxo intermediates with the (hydro)peroxo group bound end-on. The dynamic SOR active site promotes the formation of transient hydrogen bond networks, which presumably assist the cleavage of the iron-oxygen bond in order to release the reaction product, hydrogen peroxide.