A review of the role of gut microbiota in the metabolism of the steviol glycosides, stevioside and rebaudioside A, indicates that they are not absorbed intact but undergo hydrolysis by the intestinal ...microflora to steviol. Steviol is not metabolized by the intestinal flora and is absorbed from the intestine. The rate of hydrolysis for stevioside is greater than for rebaudioside A. Recent studies using mass spectrometry have shown that steviol-16,17-epoxide is not a microbial metabolite of steviol glycosides. Bacteroides species are primarily responsible for hydrolysis via their β-glucosidase activity. Fecal incubation studies with both human and animal mixed flora provide similar results, and this indicates that the rat is an appropriate model for studies on steviol glycosides. Given the similarity in the microbial metabolism of stevioside and rebaudioside A with the formation of steviol as the single hydrolysis product that is absorbed from the intestinal tract, the toxicological data on stevioside are relevant to the risk assessment of rebaudioside A.
In a broad range of species—including humans—it has been demonstrated that telomere length declines throughout life and that it may be involved in cell and organismal senescence. This potential link ...to ageing and thus to fitness has triggered recent interest in understanding how variation in telomere length is inherited and maintained. However, previous studies suffer from two main drawbacks that limit the possibility of understanding the relative importance of genetic, parental and environmental influences on telomere length variation. These studies have been based on (i) telomere lengths measured at different time points in different individuals, despite the fact that telomere length changes over life, and (ii) parent–offspring regression techniques, which do not enable differentiation between genetic and parental components of inheritance. To overcome these drawbacks, in our study of a songbird, the great reed warbler, we have analysed telomere length measured early in life in both parents and offspring and applied statistical models (so-called ‘animal models') that are based on long-term pedigree data. Our results showed a significant heritability of telomere length on the maternal but not on the paternal side, and that the mother's age was positively correlated with their offspring's telomere length. Furthermore, the pedigree-based analyses revealed a significant heritability and an equally large maternal effect. Our study demonstrates strong maternal influence on telomere length and future studies now need to elucidate possible underlying factors, including which types of maternal effects are involved.
A search for neutrinoless double-β decay (0νββ) in Xe136 is performed with the full EXO-200 dataset using a deep neural network to discriminate between 0νββ and background events. Relative to ...previous analyses, the signal detection efficiency has been raised from 80.8% to 96.4±3.0%, and the energy resolution of the detector at the Q value of Xe136 0νββ has been improved from σ/E=1.23% to 1.15±0.02% with the upgraded detector. Accounting for the new data, the median 90% confidence level 0νββ half-life sensitivity for this analysis is 5.0×1025 yr with a total Xe136 exposure of 234.1 kg yr. No statistically significant evidence for 0νββ is observed, leading to a lower limit on the 0νββ half-life of 3.5×1025 yr at the 90% confidence level.
The hydrolysis of the steviol glycosides rebaudioside (Reb) A and E, as well as steviolbioside (a metabolic intermediate) to steviol was evaluated in vitro using human fecal homogenates from healthy ...Caucasian and Asian donors. Incubation of each of the Rebs in both groups resulted in a rapid hydrolysis to steviol. Metabolism of 0.2mg/mL sample was complete within 24h, with the majority occurring within the first 16h. There were no clear differences in the rate or extent of metabolism of Reb E relative to the comparative control Reb A. The hydrolysis of samples containing 2.0mg/mL of steviol glycosides Reb A and Reb E tended to take slightly longer than 0.2mg/mL samples. Herein, we report for the first time that there were no apparent gender or ethnicity differences in the rate of metabolism of any of the Rebs, regardless of the concentrations tested. Steviolbioside, an intermediate in the hydrolysis of Reb E to steviol was also found to be rapidly degraded to steviol. These results demonstrate Reb E is metabolized to steviol in the same manner as Reb A. These data support the use of toxicology data available on steviol, and on steviol glycosides metabolized to steviol (i.e., Reb A) to underpin the safety of Reb E.
This trial evaluated the effects of 16 weeks of consumption of 1000
mg rebaudioside A (
n
=
60) a steviol glycoside with potential use as a sweetener, compared to placebo (
n
=
62) in men and women ...(33–75 years of age) with type 2 diabetes mellitus. Mean
±
standard error changes in glycosylated hemoglobin levels did not differ significantly between the rebaudioside A (0.11
±
0.06%) and placebo (0.09
±
0.05%;
p
=
0.355) groups. Changes from baseline for rebaudioside A and placebo, respectively, in fasting glucose (7.5
±
3.7
mg/dL and 11.2
±
4.5
mg/dL), insulin (1.0
±
0.64
μU/mL and 3.3
±
1.5
μU/mL), and C-peptide (0.13
±
0.09
ng/mL and 0.42
±
0.14
ng/mL) did not differ significantly (
p
>
0.05 for all). Assessments of changes in blood pressure, body weight, and fasting lipids indicated no differences by treatment. Rebaudioside A was well-tolerated, and records of hypoglycemic episodes showed no excess vs. placebo. These results suggest that chronic use of 1000
mg rebaudioside A does not alter glucose homeostasis or blood pressure in individuals with type 2 diabetes mellitus.
We present that the next-generation Enriched Xenon Observatory (nEXO) is a proposed experiment to search for neutrinoless double- β (0νββ) decay in 136Xe with a target half-life sensitivity of ...approximately 1028 yr using 5 × 103 kg of isotopically enriched liquid-xenon in a time projection chamber. This improvement of two orders of magnitude in sensitivity over current limits is obtained by a significant increase of the 136Xe mass, the monolithic and homogeneous configuration of the active medium, and the multiparameter measurements of the interactions enabled by the time projection chamber. Finally, the detector concept and anticipated performance are presented based upon demonstrated realizable background rates.
Results from a search for neutrinoless double-beta decay (0νββ) of ^{136}Xe are presented using the first year of data taken with the upgraded EXO-200 detector. Relative to previous searches by ...EXO-200, the energy resolution of the detector has been improved to σ/E=1.23%, the electric field in the drift region has been raised by 50%, and a system to suppress radon in the volume between the cryostat and lead shielding has been implemented. In addition, analysis techniques that improve topological discrimination between 0νββ and background events have been developed. Incorporating these hardware and analysis improvements, the median 90% confidence level 0νββ half-life sensitivity after combining with the full data set acquired before the upgrade has increased twofold to 3.7×10^{25} yr. No statistically significant evidence for 0νββ is observed, leading to a lower limit on the 0νββ half-life of 1.8×10^{25} yr at the 90% confidence level.
A custom-made 228Th source of several MBq activities was produced for the Borexino experiment to study the external background of the detector. The aim was to reduce the unwanted neutron emission ...produced via (α,n) reactions in ceramics typically used for commercial 228Th sources. For this purpose a ThCl4 solution was chemically converted into ThO2 and embedded in a gold foil.
The paper describes the production of the custom-made source and its characterization by means of γ-activity, dose rate and neutron source strength measurements. From γ-spectroscopic measurements it was deduced that activity transfer from the initial solution to the final source was >91% (at 68% C.L.) and the final activity was (5.41±0.30) MBq. The dose rate was measured with two dosimeters yielding 12.1mSv/h and 14.3mSv/h in 1cm distance. The neutron source strength of the 5.41MBq 228Th source was determined to be (6.59±0.85) s−1.
The Maya archaeological site at Colha in northern Belize, Central America, has yielded several spouted ceramic vessels that contain residues from the preparation of food and beverages. Here we ...analyse dry residue samples by using high-performance liquid chromatography coupled to atmospheric-pressure chemical-ionization mass spectrometry, and show that chocolate (Theobroma cacao) was consumed by the Preclassic Maya as early as 600 bc, pushing back the earliest chemical evidence of cacao use by some 1,000 years. Our application of this new and highly sensitive analytical technique could be extended to the identification of other ancient foods and beverages.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The GERDA experiment searches for the neutrinoless double beta (Ov beta beta ) decay of super(76)Ge using high-purity germanium detectors made of material enriched in super(76)Ge. For Phase II of the ...experiment a sensitivity for the half life T super(0) sub(1) super(v) sub(/2) similar to 2.10 super(26) yr is envisioned. Modified Broad Energy Germanium detectors (BEGe) with thick n super(+) electrodes provide the capability to efficiently identify and reject background events, while keeping a large acceptance for the Ov beta beta -decay signal through novel pulse-shape discrimination (PSD) techniques. The viability of producing thick-window BEGe-type detectors for the Gerda experiment is demonstrated by testing all the production steps from the procurement of isotopically modified germanium up to working BEGe detectors. Comprehensive testing of the spectroscopic as well as PSD performance of the Gerda Phase II prototype BEGe detectors proved that the properties of these detectors are identical to those produced previously from natural germanium material following the standard production line of the manufacturer. Furthermore, the production of BEGe detectors from a limited amount of isotopically modified germanium served to optimize the production, in order to maximize the overall detector mass yield. The results of this test campaign provided direct input for the subsequent production of the enriched germanium detectors.
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