Uptake and xylem transport of fipronil in sunflower

International audienceThe phenylpyrazole insecticide, fipronil, is used in seed coating against Agriotes larvae, which infest mainly corn and sunflower. Coating the seeds of the cultivated plants with fipronil has proven its effectiveness against Agriotes populations. In the case of sunflower or even corn, the possible root uptake of this insecticide may lead to a toxic effect against pollinators such as honeybees. In the present report, the uptake and transport of fipronil inside the sunflower seedling was studied in the laboratory. In a first study, sunflower was cultivated on an aqueous medium containing fipronil. An intense root uptake of fipronil occurred, leading to a transport into leaves depending upon transpiration. In a second study, plants were cultivated on a soil in which fipronil was uniformly distributed. Under our soil conditions (20% organic carbon), the partition coefficient between soil and water (K-d) was found to be equal to 386 +/- 30. The average rate of fipronil transfer from soil water to seedlings was from 2 to 2.6 times lower than water transfer. During the 3 week experiment, 55% of recovered labeled compounds was in the parent form and 35% had been converted to lipophilic metabolites, with either a 4-CF3-SO2 or 4-CF3-S substituant, which are also very potent lipophilic insecticides. This paper suggests that the possible uptake of fipronil by sunflower seedlings under agronomic conditions is mainly controlled by the physicochemical characteristics of the seed-coating mixture

How can the fipronil insecticide access phloem?

International audienceSeeds of sunflower plants coated with the fipronil C-14-insecticide were allowed to grow in the greenhouse. The distribution of the C-14-COM pounds was studied in each part of the plant after three months. After 83 days of culture small amounts of C-14-compounds were found in the inflorescence (0.6 parts per thousand of the seed deposit) which Were fipronil itself or its lipophilic or hydrophilic metabolites. The C-14-compounds were found in each part of the inflorescence (bracts, ray and disk florets containing pollen, akenes). The C-14-concentration in the xylem sap evaluated at this stage was much too low to explain the accumulated amount in the inflorescence. Under controlled conditions in a culture chamber, it was then demonstrated that a net phloem transfer of C-14-fipronil occurred from developed leaves to growing organs. This allowed us to suppose that a similar C-14-fipronil phloem transfer could occur toward the inflorescence during its formation. A quantitative evaluation suggests that most of the labeled. compounds at this stage were not coming from the leaves but from the roots and stem where storage compounds were hydrolyzed for sustaining inflorescence development

Soil distribution of fipronil and its metabolites originating from a seed-coated formulation

International audienceSeed-coating with the insecticide fipronil has been intensively used in sunflower cultivation to control soil pests such as wireworms. A research project was undertaken to determine the soil distribution of fipronil and of its main phenylpyrazole metabolites. Under agronomic conditions, the quantity of fipronil in the seed-coat (437 mu g/seed) decreased continuously during the cultivation period (3.9 mu g day(-1) during the first two months; 0.3 mu g day(-1) during the next four months). At the end of the cultivation period, 42% of all phenylpyrazole compounds remained in the seed-coat. Fipronil was poorly mobile in soil, and at the end of the cultivation period it was mostly concentrated in the soil layer close to the seed (3240 mu g k(-1) soil). Starting from the seed-coating, a fipronil concentration gradient was measured in the soil, up to a distance of I I cm from the seed. Degradation in the soil occurred at a moderate rate, probably due to the fact that water solubilization of the solid active ingredient present in the seed coating was rate limiting. Indeed, after 6 months of cultivation, only 51% of the fipronil seed-coating was found in the soil. about 7% having been absorbed by the sunflower plant. and 42% remaining in the seed coat. The predominant metabolites produced in the soil were sulfone-fipronil, sulfide-fipronil and amide-fipronil, which were produced at average rates of 5 mu g kg(-1) soil day(-1) 3 mu g ka(-1) soil day(-1) and 0.4 mu g kg(-1) soil day(-1), respectively. In contrast, the photoproduct, desulfinyl-fipronil, was barely detected. All phenylpyrazole compounds were poorly mobile, except for the amide derivative, which is devoid of insecticidal activity in marked contrast to the other metabolites. Furthermore, detectable soil contamination was limited to a zone of about 11 cm around the seed. (C) 2007 Elsevier Ltd. All rights reserved

Bees and systemic insecticides (imidacloprid, fipronil) in pollen: subnano-quantification by HPLC/MS/MS and GC/MS

International audienceImidacloprid and fipronil are two insecticides acting on the central nervous system. They are used worldwide, from the mid nineties, especially for seed coating of crops. Concomitantly to their introduction and their increasing use in French fields, honeybee populations decreased. Bee problems are nowadays reported in other countries (also called disappearing disease, desplobación de las colmenas, trouble des abeilles, deperimento degli apiari or colony collapse disorder). Bee problems have certainly several origins. Contamination of pollen and nectar by such chemicals appeared as one of the most probable cause, since subletal effects and chronic intoxications were observed on bees, at very low concentrations. We developed fully validated methods to measure contamination in pollen (sunflower and maize) for imidacloprid (HPLC/MS/MS) and for fipronil and 3 of its derivatives (GC/MS). For imidacloprid LOD and LOQ are 0.3 and 1 ng/g, respectively. For fipronil and each derivative (fiprole), LOD and LOQ are 0.07 and 0.2 ng/g, respectively. The averaged level of imidacloprid in pollen was 2-3 ng/g, which is 20-30 times higher than the concentration inducing significant mortality by chronic intoxication. Fiproles were detected in 48% of pollens issuing from treated crops. Fipronil and its sulfone derivative represented 77% and 17% of contaminants, respectively. The averaged fiprole sum Σf was 0.3 - 0.4 ng/g, which is 30-40 times higher than the concentration inducing significant mortality of bees by chronic intoxication

Quantitative analysis of mRNA-1273 COVID-19 vaccination response in immunocompromised adult hematology patients

Vaccination guidelines for patients treated for hematological diseases are typically conservative. Given their high risk for severe COVID-19, it is important to identify those patients that benefit from vaccination. We prospectively quantified serum immunoglobulin G (IgG) antibodies to spike subunit 1 (S1) antigens during and after 2-dose mRNA-1273 (Spikevax/Moderna) vaccination in hematology patients. Obtaining S1 IgG $300 binding antibody units (BAUs)/mL was considered adequate as it represents the lower level of S1 IgG concentration obtained in healthy individuals, and it correlates with potent virus neutralization. Selected patients (n 5 723) were severely immunocompromised owing to their disease or treatment thereof. Nevertheless, .50$ 300 BAUs/mL after 2-dose mRNA-1273. All patients with sickle cell disease or chronic myeloid leukemia obtained adequate antibody concentrations. Around 70% of patients with chronic graft-versus-host disease (cGVHD), multiple myeloma, or untreated chronic lymphocytic leukemia (CLL) obtained S1 IgG $300 BAUs/mL. Ruxolitinib or hypomethylating therapy but not high-dose chemotherapy blunted responses in myeloid malignancies. Responses in patients with lymphoma, patients with CLL on ibrutinib, and chimeric antigen receptor T-cell recipients were low. The minimal time interval after autologous hematopoietic cell transplantation (HCT) to reach adequate concentrations was,2 months for multiple myeloma, 8 months for lymphoma, and 4 to 6 months after allogeneic HCT. Serum IgG4, absolute B- and natural killer–cell number, and number of immunosuppressants predicted S1 IgG$ 300 BAUs/mL. Hematology patients on chemotherapy, shortly after HCT, or with cGVHD should not be precluded from vaccination. This trial was registered at Netherlands Trial Register as #NL9553

Quantitative analysis of mRNA-1273 COVID-19 vaccination response in immunocompromised adult hematology patients

Vaccination guidelines for patients treated for hematological diseases are typically conservative. Given their high risk for severe COVID-19, it is important to identify those patients that benefit from vaccination. We prospectively quantified serum immunoglobulin G (IgG) antibodies to spike subunit 1 (S1) antigens during and after 2-dose mRNA-1273 (Spikevax/Moderna) vaccination in hematology patients. Obtaining S1 IgG $300 binding antibody units (BAUs)/mL was considered adequate as it represents the lower level of S1 IgG concentration obtained in healthy individuals, and it correlates with potent virus neutralization. Selected patients (n 5 723) were severely immunocompromised owing to their disease or treatment thereof. Nevertheless, .50$ 300 BAUs/mL after 2-dose mRNA-1273. All patients with sickle cell disease or chronic myeloid leukemia obtained adequate antibody concentrations. Around 70% of patients with chronic graft-versus-host disease (cGVHD), multiple myeloma, or untreated chronic lymphocytic leukemia (CLL) obtained S1 IgG $300 BAUs/mL. Ruxolitinib or hypomethylating therapy but not high-dose chemotherapy blunted responses in myeloid malignancies. Responses in patients with lymphoma, patients with CLL on ibrutinib, and chimeric antigen receptor T-cell recipients were low. The minimal time interval after autologous hematopoietic cell transplantation (HCT) to reach adequate concentrations was,2 months for multiple myeloma, 8 months for lymphoma, and 4 to 6 months after allogeneic HCT. Serum IgG4, absolute B- and natural killer–cell number, and number of immunosuppressants predicted S1 IgG$ 300 BAUs/mL. Hematology patients on chemotherapy, shortly after HCT, or with cGVHD should not be precluded from vaccination. This trial was registered at Netherlands Trial Register as #NL9553