Effects of bifenox and oxadiazon on isolated chloroplasts,plant mitochondria and leaf pieces

The effects of bifenox (methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate) and oxadiazon (5-tert-butyl-3-(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2(3H)-one on photosynthetic activity were investigated in isolated chloroplasts, and on respiratory activity in isolated mitochondria. The global effects of these chemicals were also investigated on cucumber cotyledon pieces. It was found that, in vitro, bifenox and oxadiazon acted on cotyledon pieces as typical diphenyl ether herbicides, causing complete pigment bleaching, even at low concentrations. In addition, bifenox and oxadiazon were shown to inhibit the photosynthesis process at the chloroplast level. At concentrations of up to 40-50 μM, oxadiazon and bifenox were observed to inhibit fully the light-dependent oxygen evolution of spinach class A chloroplasts, oxadiazon acting preferentially on electron transfer at the PS II level whereas bifenox acted on the photophosphorylation process. Comparison of the amounts of herbicide needed to inhibit photosynthesis and to cause bleaching of cucumber pieces leads to the conclusion that photosynthesis inhibition by bifenox and oxadiazon is only a secondary effect.     

The nature of bound residues derived from triforine in barley plants

The shoots of barley plants root-treated with [³H]-triforine fungicide (uniformly labelled in the piperazine ring) were analysed 30 days after treatment. Methanol extraction left a solid plant residue which contained 33% of the total ³H which had been incorporated into the shoots. Methanol acidified with hydrochloric acid extracted a further 18% of the triforine-derived bound residues as N-[2,2,2-trichloro-1-(piperazin-1-yl)ethyl]formamide (8%), and piperazine (10%). In the plants, these compounds had thus been complexed to plant constituents. Hot dimethyl sulphoxide (DMSO) extracted a further 13% of the total ³H, leaving a solid residue (mainly cellulose) which contained 2% of ³H, perhaps incorporated into the cellulose. Evaporation of the solvent from the DMSO extract gave a solid, the radioactivity of which (13%) could not be extracted by methanol. A part (7%) of this radioactivity could be released by successive hydrolysis with amyloglucosidase and β-glucosidase, which generated a complex mixture of polar and water soluble unknown radioactive compounds not including piperazine. These latter compounds would be the products of extensive metabolism of triforine (and its metabolite piperazine) bound to, or incorporated into starch. Most (11%) of the radioactivity of this solid could be released by hydrochloric acid hydrolysis, which also generated a complex mixture of polar and water soluble unknown radioactive compounds not including piperazine; a part (4%) of them could have been associated with lignin in the plant.     

Characterisation of bound residues of [3H]triforine in barley grain grown in the field

Barley was grown in an experimental field and at growth stage J (during the stem extension stage when the second node of the stem was formed and the next-to-last leaf was just visible), the aerial part of the plants was sprayed with an aqueous emulsion of a mixture of triforine and [³H]triforine (uniformly labelled in the piperazine ring) at the normal rate of 250 g triforine ha^?1. The barley was harvested when ripe, and the grain was analysed separately. Extraction of the grain with methanol left methanol-insoluble solids containing an amount of radioactivity (the bound residue) which represented 75% of the total radioactivity incorporated into the grain. Methanol acidified with hydrochloric acid extracted a further 7% of the triforine-derived bound residues in the form of radioactive iminodiacetic acid (1.1%), glycine (3.3 %), serine (0.9%), ethanolamine (0.2%) and unidentified compounds (1.5 %); in the grain, these compounds or their precursors had thus been complexed to grain constituents. Aqueous 0.03M sodium hydroxide extracted a further 27% of the total tritium which had been incorporated by means of α chemical bonds into the protein fraction; acid hydrolysis of the proteins yielded radioactive glycine (9.2%), serine (3.9%) and unidentified compounds (13.9%) which could have been a mixture of a large number of other amino-acids. The plant solids (which contained 41% of the total tritium) left after the alkaline aqueous extractions, were processed and separated into tritiated cellulose (4%) and starch (37%) fractions. The starch was hydrolysed and the resulting glucose was converted into the osazone (34%). After being recrystallised several times, the osazone contained a constant specific radioactivity, indicating that [³H]glucose was present. This glucose may be considered as having a carbon skeleton mainly originating biochemically from some metabolites of [³H]triforine; this tritiated glucose may also be considered as indirect evidence of the biochemical oxidation, by transamination, of the metabolites of [³H]triforine; in barley grain, the tritiated glucose (or at least a part of it) was anabolised into proteins. No piperazine was observed in the bound residues in the grain.     

Behaviour of famoxadone deposits on grape leaves

Famoxadone is a new fungicide developed for the control of crop diseases, including grape downy mildew (Plasmopara viticola). The majority (>90%) of the spray deposit from a famoxadone 500 g kg⁻¹ water‐dispersible granule formation on a grape leaf were found on the leaf surface or associated with epicuticular waxes. A significant fraction of this deposit could not be removed by a water wash, suggesting strong binding to the waxes. Nearly 100% of the spray deposit was still recovered after 12 days of exposure to a dry environment, confirming the good residual properties of the substance. Thirty per cent of the applied active ingredient was lost after exposure to a wet environment, probably via hydrolysis or wash‐off. Studies with radiolabelled famoxadone formulated as a suspension concentrate indicated that redistribution occurred both in dry conditions, via diffusion in the cuticular waxes, and in wet conditions via dissolution in water followed by re‐deposition. No systemic movement of famoxadone was observed within the treated plant. Grape plants treated with famoxadone alone or in mixture with cymoxanil and subjected to up to 50 mm of artificial rain remained well protected against downy mildew infections. Good rain‐fastness was observed even 2 h after fungicide application. Despite low water solubility, famoxadone spray residues on grape leaves were reactivated in surface water sufficiently quickly to prevent infection by P viticola. © 2000 Society of Chemical Industry     

Modelling historical mesocosm data: Application of a fish bioenergetics model in semi‐natural conditions

Developing ecological models for accurately predicting the dynamics of a population and individual physiological processes in field conditions is a challenging task for ecosystem management and ecological risk assessment. Here, we propose to assess the relevance of a dynamic energy budget (DEB) model calibrated using data previously generated from laboratory experiments for adult three‐spined sticklebacks (Gasterosteus aculeatus) living in semi‐natural conditions. We compared different ways of integrating different data sets such as temperature and prey abundance obtained in mesocosm experiments to assess the predictive capacity of the model. By this study, we provide recommendations for developing an appropriate environmental scenario (e.g. natural variations of food and temperature) for using a DEB model in a field context. We conclude that a DEB model calibrated with laboratory data can be used to predict the physiological processes of an organism living in semi‐natural conditions, but that the reproductive behaviour of the organism can affect the predictions. At last, we suggest that further studies on the feeding behaviour may be necessary for immature organisms.     

Global warming: Antioxidant responses to deal with drought and elevated temperature in Stylosanthes capitata,a forage legume

Drought can be more frequent and severe along with elevated temperatures (eT). To deal with the climate change impact on plants, we need to understand the plant biochemical performance. Nowadays, there is a lack of information about the antioxidant response of plants, mainly growing in field conditions and under the future climatic scenario. In this context, we carried out this experiment to analyse the antioxidant responses of the forage legume Stylosanthes capitata Vogel (in field condition) to eT and water deprivation. This work had four treatments: control, eT (+2°C above ambient canopy temperature), wS (water deprivation) and eT + wS. Temperature free-air controlled enhancement (T-FACE) system was used for warming, and samples were taken 17, 24 and 46 days after warming exposure at time periods of 6:00 a.m. and 12:00 p.m. The eT + wS treatments decreased catalase, superoxide dismutase (SOD) and ascorbate peroxidase activities, especially at 46 days. Nevertheless, glutathione (GSH) content was not modified by eT + wS treatments. Also, we determined an important inverse relation among SOD-GR-GSH and MDA-H₂O₂. In conclusion, combined stresses provoked detrimental effects of enzymatic antioxidant responses. Furthermore, we highlighted the importance of SOD-GR and GSH to avoid damages of reactive oxygen species in S. capitata grown under climate change. In addition, we suggest an adequate irrigation management in order to improve the antioxidant systems to face the eT, successfully; besides, we consider that the uses of tolerant cultivars are key under climate change conditions.     

Immune response to and tissue localization of the Wolbachia surface protein (WSP) in dogs with natural heartworm (Dirofilaria immitis) infection

Human and animal parasitic filarial nematodes, including the agent of canine and feline heartworm disease Dirofilaria immitis, harbour intracellular bacteria of the genus Wolbachia (Rickettsiaies). It is thought that these bacteria play an important role in the pathogenesis and immune response to filarial infection. Immunoglobulin G (total IgG, IgG1, IgG2) production against and immunohistochemical staining of tissues for the Wolbachia surface protein (WSP) from dogs with natural heartworm infection were evaluated. All infected dogs had significant total anti-WSP IgG levels compared to healthy controls. Interestingly, WSP was recognized by the IgG2 subclass in both microfilariemic dogs and in dogs with no circulating microfilariae (occult infection). However, microfilariemic dogs also produced gG1 antibodies. Positive staining for WSP was observed in lungs, liver and kidneys, in particular in glomerular capillaries of naturally infected dogs who had died from heartworm disease. Our results show for the first time that Wolbachia is recognized specifically by D. immitis--infected dogs and that the bacteria is released into host tissue. Furthermore, microfilariemic status appears to effect immune responses to this endosymbiont.     

Serum immunoglobulin G concentration in Southern elephant seal, Mirounga leonina (Linnaeus, 1758), from Elephant Island (Antarctica): sexual and adrenal steroid hormones effects

Serum immunoglobulin G (IgG; indirect enzyme-linked immunosorbent assay), as well as sexual and adrenal steroid hormones' concentrations (radioimmunoassay) were determined in 63 (male and female) Southern elephant seals (Mirounga leonine) at different developmental stages (weaned pups, juveniles and adults). In females, IgG values (mean+/-S.D.) were higher (P<0.05) in adults (15.9+/-6.5mg ml(-1)) than in juveniles (7.9+/-4.0mg ml(-1)), but similar to weaned pups (12.0+/-5.0mg ml(-1)). Estrogen concentration was higher (P<0.05) in adults than in the weaned pups. In females, a significant (P<0.05) correlation (R=0.4) between serum IgG level and progesterone concentration was observed. In males, testosterone concentration was higher (P<0.05) in adults than in the juveniles and weaned pups. Aldosterone and cortisol concentrations were higher (P<0.05) in weaned pups (1056.0+/-643.1pmol 1(-1) and 272.7+/-110.0 nmol 1(-1), respectively) than in the juveniles (638.6+/-579.7pmol1(-1) and 152.9+/-97.3nmol 1(-1), respectively) and adults (386.5+/-209.1pmol (-1) and 145.7+/-67.3nmol 1(-1), respectively). These findings indicate that weaned pups are subjected to a higher natural stressful condition in the field. Despite this, humoral immunity, measured through IgG concentration, is not impaired in weaned pups.     

Ultrastructural characteristics of spermiogenesis in the domestic duck (Anas platyrhynchos)

In this present study was observed that the spermatids underwent morphological differentiation and modifications, which primarily comprised nuclear elongation, during the process of spermiogenesis in the domestic duck. The acrosome was formed and the flagellum developed concomitantly with nuclear modifications. Thus, various modifications could be observed during this process, especially changes in the distribution of cytoplasmic organelles. Long cisternae of the rough endoplasmic reticulum present in the spermatid cytoplasm dissociated into vesicles and the distal centriole initiated the development of the flagellum in the cellular portion opposite to the acrosome. The ultrastructure of the spermatids of the domestic duck did not show the characteristic development of pre-acrosomal granules, but the acrosomal granule could be directly visualized in this species.