Effects of silver nanoparticles on the freshwater molluscs Dreissena polymorpha and Marisa cornuarietis

Die vorliegende Arbeit vergleicht die Auswirkungen von Silber-Nanopartikeln (npAg) mit denjenigen von Silber-Ionen(Ag+) in der Süßwassermuschel Dreissena polymorpha und der Süßwasserschnecke Marisa cornuarietis. Mittels eines statischen, dreiwöchigen Expositionsversuchs mit nomineller Expositionskonzentration von 100 µg Ag/L wurde gezeigt, dass npAg in gleichem Ausmaß wie Ag+ in D. polymorpha aufgenommen wird. In den drei Organbereichen Mantel/Muskulatur, Kiemen und Gonade/Verdauungstrakt wurden eine Akkumulationsunterschiede festgestellt. Ab dem ersten Expositionstag wurde eine gleichbleibende Gewebekonzentration von rund 6 µg Ag/g Trockenmasse erreicht. Im Expositionsmedium zeigten beide Silberspezies ein ähnliches Verhalten und lagen beide teils agglomeriert bzw. an Partikel adsorbiert vor. Untersuchungen zur Silberaufnahme in verschiedenen Zellfraktionen des Muschelweichgewebes ergaben bei der Exposition mit npAg eine verstärkte Silberakkumulation in der Lysosomen-Fraktion, was durch Endocytose des npAg erklärt werden könnte. Es gab Hinweise darauf, dass sich npAg innerhalb der Lysosomen auflöst und dass anschließend dieselben Detoxifizierungsmechanismen greifen wie für Ag+. Diese Mechanismen könnten vor allem in der Einlagerung in metallreichen Granula und deren Speicherung in unterschiedlichen Zellkompartimenten bestehen. Die in D. polymorpha untersuchten toxikologischen Endpunkte (Fitness-Index, Glutathion-S-Transferasen, Katalase, Hitzeschockproteine) reagierten weder auf npAg- noch auf Ag+-Exposition. Silber-Nanopartikel wurden von M. cornuarietis -Embryonen in geringerem Ausmaß akkumuliert als Silber-Ionen. Es wird vermutet, dass nur Ag+ durch die Eihülle bis zum Embryo vordringt. Entsprechend reagierten die Schneckenembryonen deutlich empfindlicher auf Ag+- als auf npAg-Exposition. Letztere erhöhte bei einer Expositionskonzentration von 200 µg Ag/L die Mortalität nur geringfügig, während Ag+-Exposition bereits bei 30 µg Ag/L zu 100% Mortalität führte. Auch die anderen im Marisa Embryo Toxicity Test untersuchten toxikologischen Endpunkte zeigten Reaktionsmuster, die bei Ag+-Exposition stets deutlicher ausgeprägt waren als bei npAg-Exposition: Die Entwicklungsdauer wurde verkürzt, das Schlupfgewicht wurde reduziert, ebenso wie die Herzschlagrate. Die Ergebnisse der Arbeit zeigen, dass in Dreissena polymorpha sowohl npAg- als auch Ag+-Exposition zu gleich starker Silberanreicherung im Gewebe, aber jeweils nicht zu toxischen Effekten führen. Der Grund dafür ist vermutlich im Entgiftungsvermögen der Muschel zu suchen. In Marisa cornuarietis-Embryonen hingegen wurde npAg in deutlich geringerem Ausmaß als Ag+ aufgenommen. Außerdem hatte npAg-Exposition im Gegensatz zu Ag+-Exposition kaum toxische Auswirkungen in den Embryonen. Es gibt Hinweise darauf, dass npAg die Eihülle nicht zu durchdringen vermag, somit vom Embryo nicht aufgenommen wird und deshalb keine Toxizität entfalten kann. Die Tauglichkeit von M. cornuarietis- Embryonen für Toxizitätstests mit partikulären Substanzen ist hierdurch in Frage gestellt.This study compared the effects of silver nanoparticles (npAg) with those of silver ions (Ag+) in the freshwater mussel Dreissena polymorpha and in the freshwater snail Marisa cornuarietis. A three-week static exposure with a nominal exposure concentration of 100 µg Ag/L demonstrated that npAg and Ag+ accumulate to the same extent in D. polymorpha. No differences in accumulation could be detected between the three body parts mantle/muscle, gills and gonad/digestive tract. After the first day of exposure, a constant tissue concentration of approximately 6 µg Ag/g dry weight was reached. Both silver species exhibited a similar behaviour in the medium and were partly present as agglomerates and adsorbed to particles, respectively. Studies of silver uptake in various cell fractions of the mussels’ soft tissue revealed that silver accumulation in the lysosmal fraction was enhanced due to npAg exposition, which might be explained by endocytosis of npAg. There were indications that npAg dissolves within the lysosomes and afterwards the same detoxification mechanisms apply as for Ag+. These mechanisms might mainly consist of incorporation in metal-rich granules which were stored in different cell compartments. The examined toxicological endpoints in D. polymorpha (fitness index, Glutathione- S-transferases, catalase, heat shock proteins) did not respond to either npAg- or Ag+ exposure. Silver nanoparticles were taken up to a lesser extent by M. cornuarietis embryos than silver ions. There are hints that only Ag+ may penetrate the egg membrane and reach the embryo. Accordingly, the snail embryos responded more sensitively to Ag+- than to npAg exposure. The latter only slightly elevated mortality at an exposure concentration of 200µg Ag/L, while Ag+ exposure resulted in 100% mortality at 30 µg Ag/L. The other toxicological endpoints examined in the Marisa Embryo Toxicity Test showed patterns that were always more pronounced in Ag+ exposures than in npAg exposure: developmental time was shortened, hatching weight was reduced and heart rate was lowered. The results of this study show that both npAg- and Ag+ exposure result in similar silver accumulation in of Dreissena polymorpha, but do not lead to toxic effects. A probable reason might be the mussels’ detoxification capacity. However, in Marisa cornuarietis embryos, npAg was taken up to a much lesser extent than Ag+. Moreover, in contrast to Ag+ exposure, npAg exposure had hardly any toxic effects. There are indications that npAg cannot penetrate the egg membrane. It is thus not absorbed by the embryo and does not cause toxicity. The suitability of M. cornuarietis embryos for toxicity tests with particulate substances might be questioned

Systemic availability and metabolism of colonic-derived short-chain fatty acids in healthy subjects: a stable isotope study

The short-chain fatty acids (SCFAs), acetate, propionate and butyrate, are bacterial metabolites that mediate the interaction between the diet, the microbiota and the host. In the present study, the systemic availability of SCFAs and their incorporation into biologically relevant molecules was quantified. Known amounts of 13C-labelled acetate, propionate and butyrate were introduced in the colon of 12 healthy subjects using colon delivery capsules and plasma levels of 13C-SCFAs 13C-glucose, 13C-cholesterol and 13C-fatty acids were measured. The butyrate-producing capacity of the intestinal microbiota was also quantified. Systemic availability of colonic-administered acetate, propionate and butyrate was 36%, 9% and 2%, respectively. Conversion of acetate into butyrate (24%) was the most prevalent interconversion by the colonic microbiota and was not related to the butyrate-producing capacity in the faecal samples. Less than 1% of administered acetate was incorporated into cholesterol and <15% in fatty acids. On average, 6% of colonic propionate was incorporated into glucose. The SCFAs were mainly excreted via the lungs after oxidation to 13CO2, whereas less than 0.05% of the SCFAs were excreted into urine. These results will allow future evaluation and quantification of SCFA production from 13C-labelled fibres in the human colon by measurement of 13C-labelled SCFA concentrations in blood

Falsely elevated plasma testosterone concentrations in neonates : importance of LC-MS/ MS measurements

CITATION: Hamer, H.M. et al. 2018. Falsely elevated plasma testosterone concentrations in neonates : importance of LC-MS/ MS measurements. Clinical Chemistry and Laboratory Medicine (CCLM), 56(6):e141–e143, doi:10.1515/cclm-2017-1028.The original publication is available at https://www.degruyter.com/view/j/cclmIn newborns with atypical genitalia, suspicious for a disorder of sex development (DSD), measurement of testosterone is an essential part in the diagnostic workup. Previously, direct testosterone immunoassays have proven to be inaccurate because they tend to overestimate testosterone concentrations in the lower ranges, such as those in females and infants, but specifically also in neonates. Based on the concern for cross-reactivity in neonatal samples, the recently revised UK guideline on the initial evaluation of DSD from the UK Society for Endocrinology recommends that steroids in plasma or serum are measured by either LC-MS/MS or immunoassays after organic solvent extraction. The use of LC-MS/MS was considered superior by a recent consensus meeting of DSD experts across Europe, although validation and quality control remain challenging.Publishers versio

Effects of a wheat bran extract containing arabinoxylan oligosaccharides on gastrointestinal health parameters in healthy adult human volunteers : a double-blind, randomised, placebo-controlled, cross-over trial

Wheat bran extract (WBE) is a food-grade soluble fibre preparation that is highly enriched in arabinoxylan oligosaccharides. In this placebo-controlled cross-over human intervention trial, tolerance and effects on colonic protein and carbohydrate fermentation were studied. After a 1-week run-in period, sixty-three healthy adult volunteers consumed 3, 10 and 0 g WBE/d for 3 weeks in a random order, with 2 weeks' washout between each treatment period. Fasting blood samples were collected at the end of the run-in period and at the end of each treatment period for analysis of haematological and clinical chemistry parameters. Additionally, subjects collected a stool sample for analysis of microbiota, SCFA and pH. A urine sample, collected over 48 h, was used for analysis of p-cresol and phenol content. Finally, the subjects completed questionnaires scoring occurrence frequency and distress severity of eighteen gastrointestinal symptoms. Urinary p-cresol excretion was significantly decreased after WBE consumption at 10 g/d. Faecal bifidobacteria levels were significantly increased after daily intake of 10 g WBE. Additionally, WBE intake at 10 g/d increased faecal SCFA concentrations and lowered faecal pH, indicating increased colonic fermentation of WBE into desired metabolites. At 10 g/d, WBE caused a mild increase in flatulence occurrence frequency and distress severity and a tendency for a mild decrease in constipation occurrence frequency. In conclusion, WBE is well tolerated at doses up to 10 g/d in healthy adults volunteers. Intake of 10 g WBE/d exerts beneficial effects on gut health parameters

Correction to: Levamisole causes a transient increase in plasma creatinine levels but does not affect kidney function based on cystatin C (Pediatric Nephrology, (2022), 37, 10, (2515-2519), 10.1007/s00467-022-05547-9)

The original version of this article unfortunately contained a mistake. During the process of typesetting, the institutional author attribution “on behalf of the LEARNS consortium” was left out of the author group. The correct attribution is as shown above. The publisher apologizes for this mistake. The original article was updated

Levamisole causes a transient increase in plasma creatinine levels but does not affect kidney function based on cystatin C

Background: In pediatric patients treated with levamisole to prevent relapses of idiopathic nephrotic syndrome (INS), a transient and non-progressive rise in creatinine levels has been observed. It has been suggested that levamisole affects tubular secretion of creatinine. However, other potential mechanisms — nephrotoxicity and interference with the analytical assay for creatinine — have never been thoroughly investigated. Methods: In three steroid-sensitive nephrotic syndrome (SSNS) patients with elevated plasma creatinine levels, treated with levamisole 2.5 mg/kg every other day, serum cystatin C was determined. The glomerular filtration rate (GFR) was estimated using the full age spectrum for creatinine and the full age spectrum for cystatin C equations. Interference of levamisole with the enzymatic creatinine assay was tested using spare human plasma of different creatinine concentrations spiked with levamisole (4, 20, and 100 µM). Results: Three patients who received levamisole with elevated plasma creatinine levels had normal serum cystatin C levels and corresponding estimated GFR. There was no assay interference. Conclusion: Levamisole increases plasma creatinine levels, which is most probably due to impaired tubular secretion of creatinine since there was no assay interference and patients had normal eGFR based on serum cystatin C. However, interference of metabolites of levamisole could not be excluded. To monitor GFR, cystatin C in addition to creatinine should be used and be measured before and during levamisole use

C11-oxy C19 and C11-oxy C21 steroids in neonates: UPC2-MS/MS quantification of plasma 11β-hydroxyandrostenedione, 11-ketotestosterone and 11-ketoprogesterone

The purpose of this study was to identify the C11-oxy C19 and C11-oxy C21 steroids in male and female neonate plasma. At birth, the most abundant C11-oxy steroids detected in neonatal plasma were 11β-hydroxyandrostenedione, ∼13 nM, and 11-ketoprogesterone, ∼23 nM. C11-oxy C19 steroids were higher than C19 steroids in neonatal plasma, 22.2 nM vs 5.4 nM. The inclusion of C11-oxy C19 and C21 steroid reference ranges in routine steroid analyses will assist the characterization of disorders associated with impaired steroidogenic enzyme expression and the identification of potential biomarkers