The mobilization of nutrient reserves into the ovaries of Aedes aegypti mosquitoes after sugar-feeding plays a vital role in the female's reproductive maturation. In the present work, three-dimensional secondary ion mass spectrometry imaging (3D-SIMS) was used to generate ultrahigh spatial resolution (~1 μm) chemical maps and study the composition and spatial distribution of lipids at the single ovarian follicle level (~100 μm in size). 3D-Mass Spectrometry Imaging (3D-MSI) allowed the identification of cellular types in the follicle (oocyte, nurse and follicular cells) using endogenous markers, and revealed that most of the triacyglycerides (TGs) were compartmentalized in the oocyte region. By comparing follicles from water-fed and sugar-fed females (n=2), 3D-MSI-Time of Flight-SIMS showed that TGs were more abundant in ovarian follicles of sugar-fed females; despite relative sample reproducibility per feeding condition, more biological replicates will better support the trends observed. While the current 3D-MSI-TOF-SIMS does not permit MS/MS analysis of the lipid species, complementary LC-MS/MS analysis of the ovarian follicles aided tentative lipid assignments of the SIMS data. The combination of these MS approaches is giving us a first glimpse of the distribution of functionally relevant ovarian lipid molecules at the cellular level. These new tools can be used to investigate the roles of different lipids on follicle fitness and overall mosquito reproductive output.

• Klíčová slova
• SIMS, imaging, lipids, mass spectrometry, mosquitoes, ovary,
• Publikační typ
• časopisecké články MeSH

An ultra sensitive method for arsenic (As) speciation analysis based on selective hydride generation (HG) with preconcentration by cryotrapping (CT) and inductively coupled plasma- mass spectrometry (ICP-MS) detection is presented. Determination of valence of the As species is performed by selective HG without prereduction (trivalent species only) or with L-cysteine prereduction (sum of tri- and pentavalent species). Methylated species are resolved on the basis of thermal desorption of formed methyl substituted arsines after collection at -196°C. Limits of detection of 3.4, 0.04, 0.14 and 0.10 pg mL-1 (ppt) were achieved for inorganic As, mono-, di- and trimethylated species, respectively, from a 500 μL sample. Speciation analysis of river water (NRC SLRS-4 and SLRS-5) and sea water (NRC CASS-4, CASS-5 and NASS-5) reference materials certified to contain 0.4 to 1.3 ng mL-1 total As was performed. The concentrations of methylated As species in tens of pg mL-1 range obtained by HG-CT-ICP-MS systems in three laboratories were in excellent agreement and compared well with results of HG-CT-atomic absorption spectrometry and anion exchange liquid chromatography- ICP-MS; sums of detected species agreed well with the certified total As content. HG-CT-ICP-MS method was successfully used for analysis of microsamples of exfoliated bladder epithelial cells isolated from human urine. Here, samples of lysates of 25 to 550 thousand cells contained typically tens pg up to ng of iAs species and from single to hundreds pg of methylated species, well within detection power of the presented method. A significant portion of As in the cells was found in the form of the highly toxic trivalent species.

• Klíčová slova
• Arsenic, Hydride generation, Inductively coupled plasma mass spectrometry, Speciation analysis,
• Publikační typ
• časopisecké články MeSH