Timing of accreting neutron stars with future X-ray instruments: towards new constraints on dense matter equation of state

The Enhanced X-ray Timing and Polarimetry (eXTP) mission is a space mission to be launched in the late 2020s that is currently in development led by China in international collaboration with European partners. Here we provide a progress report on the Czech contribution to the eXTP science. We report on our simulation results performed in Opava (Institute of Physics of the Silesian University in Opava) and Prague (Astronomical Institute of the Czech Academy of Sciences), where the advanced timing capabilities of the satellite have been assessed for bright X-ray binaries that contain an accreting neutron star (NS) and exhibit the quasi-periodic oscillations. Measurements of X-ray variability originating in oscillations of fluid in the innermost parts of the accretion region determined by general relativity, such as the radial or Lense-Thirring precession, can serve for sensitive tests enabling us to distinguish between the signatures of different viable dense matter equations of state. We have developed formulae describing non-geodesic oscillations of accreted fluid and their simplified practical forms that allow for an expeditious application of the universal relations determining the NS properties. These relations, along with our software tools for studying the propagation of light in strong gravity and neutron star models, can be used for precise modeling of the X-ray variability while focusing on properties of the intended Large Area Detector (LAD). We update the status of our program and set up an electronic repository that will provide simulation results and gradual updates as the mission specifications progress toward their final formulation.Comment: 16 pages, 6 figures, proceedings of IBWS conference, eds. Martin Jelinek and Marianna Dafcikova, 22-26 May 2023 (Karlovy Vary, Czech Republic), ISSN: 1336-033

Statement on the risks for public health related to a possible increase of the maximum level of deoxynivalenol for certain semi-processed cereal products

The European Food Safety Authority (EFSA) was asked to deliver a scientific opinion on the risks for public health related to a possible increase of the maximum level (ML) of deoxynivalenol (DON) for certain semi-processed cereal products from 750 µg/kg to 1000 µg/kg. For this statement, EFSA relied on existing occurrence data on DON in food collected between 2007 and 2012 and reported by 21 European countries. Due to the lack of appropriate occurrence data from pre-market monitoring, the impact of increasing the ML was estimated using a simulation approach, resulting in an expected increase in mean levels of the respective food products by a factor of 1.14-1.16. Based on median chronic exposure in several age classes, the percentage of consumers exceeding the group provisional maximum tolerable daily intake (PMTDI) of 1 μg/kg body weight (b.w.) for the sum of DON and its 3- and 15-acetyl-derivatives, established by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) in 2010, is approximately 2-fold higher with the suggested increased ML than with the current ML. Several acute exposure scenarios resulted in exceedance of the group acute reference dose (ARfD) of 8 µg/kg b.w. established by JECFA with up to 25.9 % of the consumption days above the group ARfD. The EFSA Scientific Panel on Contaminants in the Food Chain notes that the group health based guidance values (HBGVs) include 3-Ac-DON and 15-Ac-DON. The exposure from the acetyl-derivatives has not been covered in this statement, since the acetyl-derivatives are not included in the current or suggested increased ML and because only few occurrence data are available. An increase of the DON ML can be expected to be associated with an increase of the levels of DON and Ac-DONs, and can therefore increase the exposure and consequently the exceedances of the group HBGVs

Risks to human and animal health related to the presence of deoxynivalenol and its acetylated and modified forms in food and feed

Deoxynivalenol (DON) is a mycotoxin primarily produced by Fusarium fungi, occurring predominantly in cereal grains. Following the request of the European Commission, the CONTAM Panel assessed the risk to animal and human health related to DON, 3-acetyl-DON (3-Ac-DON), 15-acetyl-DON (15-Ac-DON) and DON-3-glucoside in food and feed. A total of 27,537, 13,892, 7,270 and 2,266 analytical data for DON, 3-Ac-DON, 15-Ac-DON and DON-3-glucoside, respectively, in food, feed and unprocessed grains collected from 2007 to 2014 were used. For human exposure, grains and grain-based products were main sources, whereas in farm and companion animals, cereal grains, cereal by-products and forage maize contributed most. DON is rapidly absorbed, distributed, and excreted. Since 3-Ac-DON and 15-Ac-DON are largely deacetylated and DON-3-glucoside cleaved in the intestines the same toxic effects as DON can be expected. The TDI of 1 μg/kg bw per day, that was established for DON based on reduced body weight gain in mice, was therefore used as a group-TDI for the sum of DON, 3-Ac-DON, 15-Ac-DON and DON-3-glucoside. In order to assess acute human health risk, epidemiological data from mycotoxicoses were assessed and a group-ARfD of 8 μg/kg bw per eating occasion was calculated. Estimates of acute dietary exposures were below this dose and did not raise a health concern in humans. The estimated mean chronic dietary exposure was above the group-TDI in infants, toddlers and other children, and at high exposure also in adolescents and adults, indicating a potential health concern. Based on estimated mean dietary concentrations in ruminants, poultry, rabbits, dogs and cats, most farmed fish species and horses, adverse effects are not expected. At the high dietary concentrations, there is a potential risk for chronic adverse effects in pigs and fish and for acute adverse effects in cats and farmed mink

Transcriptomic-based bioassays for the detection of type A trichothecenes

The type A trichothecenes T-2 toxin (T-2) and HT-2 toxin (HT-2) are hazardous Fusarium products that contaminate many field crops growing in cold to temperate regions across the world. Toxicity studies in laboratory and farm animals have been used to derive a temporary tolerable daily intake (t-TDI) for the sum of T-2 and HT-2 of no more than 60 ng/kg body weight. To protect the consumers, it is now necessary to screen a large number of food samples for the presence of these poisonous fungal metabolites. Towards that goal, we discovered that the transcriptional apparatus of a human carcinoma cell line (MCF7) provides a sensitive biological sensor of type A trichothecenes. In fact, exposure of this easy-to-culture cell line to T-2 or HT-2 results in the regulation of >2,000 different transcripts with expression changes ranging from >5,000-fold gene inductions to >40-fold gene repressions. These transcriptional responses have been exploited to develop practical microchip and reverse transcription-polymerase chain reaction (RT-PCR) assays for the detection of type A trichothecenes at parts per billion levels

A new PCR-based bioassay strategy for the detection of type A trichothecenes in food

Type A trichothecenes (primarily T-2 and HT-2 toxins) are common fungal metabolites found in a wide range of grains and other field crops grown in temperate climatic zones. By acting as potent inhibitors of protein synthesis, T-2 and HT-2 exert adverse effects particularly against rapidly proliferating tissues, including the bone marrow, the immune system and epithelial cells. Based on toxicity studies in laboratory and farm animals, a temporary tolerable daily intake for the sum of T-2 and HT-2 has been issued in the European Union. However, exposure assessments suggest that the combined intake of these natural compounds exceeds in many cases the proposed threshold. To further protect the consumers, it is therefore necessary to screen a large number of food samples for parts per billion levels of both T-2 and HT-2. Towards that goal, we are the first to report that these two type A trichothecenes induce fast and high-amplitude transcriptional changes in cultured human breast cancer cells. This specific response involving marker gene inductions by more than 1000-fold has been exploited to develop a real-time PCR-based screening method that displays a limit of detection of 5 ng/g for T-2 and 10 ng/g for HT-2. The practicability of this bioassay is demonstrated by its application to the detection of type A trichothecenes in different food matrices

Detection of hazardous food contaminants by transcriptomics fingerprinting

Unprecedented biotechnological advances in the past decade have delivered powerful transcriptomics methods that provide new opportunities for a risk-based and, hence, more effective control of food quality and safety. The fundamental hypothesis underlying the application of a transcriptomics or other “-omics” strategies is that toxicant-specific changes of gene expression will reveal the presence of chemical hazards with possibly adverse health effects. Indeed, living cells display wide adaptive plasticity by responding with characteristic expression signatures to various stimuli (e.g., proliferation signals, genotoxic or cytotoxic insults, oxidative bursts and other types of chemical stress). Flexible transcriptomics platforms that can be scaled to suit different applications in food quality and safety involve oligonucleotide microarrays (also known as “DNA chips”), focused polymerase chain reaction (PCR) arrays and, more recently, high-throughput “next generation” sequencing technologies. In this review, we illustrate the potential impact of transcriptomics for the detection of hazardous food constituents or contaminants, including dioxins, xenoestrogens, mycotoxins and Maillard reaction products. We also discuss the predictive power of “-omics” fingerprinting with respect to the identification of emerging contaminants and the significance of these methods for risk assessment at all stages of the food-production chain