Osmo-respiratory compromise in the mosshead sculpin (Clinocottus globiceps): effects of temperature, hypoxia, and re-oxygenation on rates of diffusive water flux and oxygen uptake

In nature, mosshead sculpins (Clinocottus globiceps) are challenged by fluctuations in temperature and oxygen levels in their environment. However, it is unclear how mosshead sculpins modulate the permeability of their branchial epithelia to water and O2 in response to temperature or hypoxia stress. Acute decrease in temperature from 13 to 6 oC reduced diffusive water flux rate by 22% and ṀO2 by 51%, whereas acute increase in temperature from 13 to 25 oC increased diffusive water flux rate by 217% and ṀO2 by 140%, yielding overall Q10 values of 2.08 and 2.47 respectively. Acute reductions in oxygen tension from >95% to 20% or 10% air saturation did not impact diffusive water flux rates, however, ṀO2 was reduced significantly by 36% and 65% respectively. During 1-h or 3-h recovery periods diffusive water flux rates were depressed while ṀO2 exhibited overshoots beyond the normoxic control level. Many responses differed from those seen in our parallel earlier study on the tidepool sculpin, a cottid with similar hypoxia tolerance but much smaller gill area that occupies a similar environment. Overall, our data suggest that during temperature stress, diffusive water flux rates and ṀO2 follow the traditional osmo-respiratory compromise pattern, but during hypoxia and re-oxygenation stress, diffusive water flux rates are decoupled from ṀO2.

Assessment of Radiation Risk Perception and Interest in Tritiated Water among Returnees to and Evacuees from Tomioka Town within 20 km of the Fukushima Daiichi Nuclear Power Plant

In this study, we aimed to investigate radiation risk perception, mental health, and interest in tritiated water among evacuees from and returnees to Tomioka town, Japan, as well as to evaluate the intention to return (ITR) among evacuees living inside and outside Fukushima Prefecture. Of the 1728 respondents, 318 (18.4%) and 1203 (69.6%) participants reported living outside and inside Fukushima Prefecture, and 207 (12.0%) reported living in Tomioka. The ITR was not significantly different between those who lived inside and outside the prefecture among the evacuees. Similarly, there were no significant differences in radiation risk perception, mental health, and interest in tritiated water. However, the evacuees were independently associated with a motivation to learn about tritiated water (OR = 1.242, 95%Cl: 1.041-1.438, p = 0.016), reluctance to consume food from Tomioka (OR = 1.635, 95%Cl: 1.372-1.948, p < 0.001), and concern that adverse health effects would occur because of the Fukushima Daiichi Nuclear Power Plant accident (OR = 1.279, 95%Cl: 1.055-1.550, p = 0.012) compared to returnees, according to logistic regression analysis. Interestingly, the returnees were found to have better mental health but lower life satisfaction than the evacuees. These findings suggest the importance of ongoing risk communication about radiation exposure and tritiated water among residents regardless of their place of residency.

Tritiated Water Induces Toxicity in Human Umbilical Vein Vascular Endothelial Cells via IL8

We aimed to determine the toxic effects of tritiated water (HTO) on 12 generations (T1-T12) of human umbilical vein vascular endothelial cells (HUVECs) and elucidate the underlying mechanisms. We evaluated cellular senescence, interleukin (IL) 8 concentrations, and angiogenesis using β-galactosidase staining, enzyme-linked immunosorbent assay, and in vitro assays, respectively. The adhesion properties of contaminated cells and differentially expressed genes were assessed using the xCELLigence RTCA SP system and gene chip analysis, respectively. We found that long-term exposure to low levels of HTO can reduce the adhesion of HUVECs to the cellular matrix as well as their angiogenic capacity, while increasing their permeability, senescence, and adhesion to monocytes. Interleukin 8 activated the p38 and Epidermal Growth Factor Receptor (EGFR) pathways in HTO-treated cells and hence was identified as a key candidate of biomarker. The present study clarified the toxicity of HTO in vascular endothelial cells and identified IL8 as a novel protective target with important theoretical and practical values.

The response of human mesenchymal stem cells to internal exposure to tritium β-rays

There is no doubt that estimating the exposure risk of external and internal low-dose radiation is an imperative issue in radiobiological study. Human mesenchymal stem cells (hMSCs) are multipotent and self-renewing, supporting the regeneration of damaged tissue, including tissue damaged by radiation. However, the responses of hMSCs to internal exposure to radionuclides are still insufficiently understood. In order to evaluate the adverse effects produced by internal exposure to tritiated water (HTO) at a low dose, hMSCs were exposed to 2 × 107 Bq/ml HTO, and the biological effects after the exposure were examined. Apoptosis and DNA double-strand breaks (DSBs) were assayed to analyze the cellular response to the damage induced by HTO. Slight enhancement of apoptosis was found after treatment, except at the dose of 9 mGy. The number of DSBs at 24 h post-irradiation showed that the DNA damage was able to be efficiently repaired by the hMSCs. Moreover, the increasing proportion of the cell population in S phase proved that the persistence of residual γH2AX foci at lower concentrations of HTO was attributable to the secondary production of DSBs in DNA replication. Our work adds to the available data, helping us understand the risk of stem cell transformation due to internal exposure and its correlation with low-dose radiation-induced carcinogenesis.

Effects of Chahuangjing on Decorporation and Radiation Protection Against Tritiated Water

The purpose of this study was to investigate the effects of Chahuangjing, a novel traditional Chinese medicinal compound, on decorporation and radiation protection against tritiated water (HTO). Sixty male specific-pathogen-free-grade C57BL/6J mice were randomly divided into 12 groups: mice in 4 control groups were intraperitoneally injected with sterile water; mice in 4 HTO groups were intraperitoneally injected with 11.1 × 10⁵ Bq/g of HTO; and mice in the other 4 groups were administered with HTO and a Chahuangjing compound (0.2 mL, once daily). After 1, 7, 14, and 21 days, the mice were killed and samples were collected. A liquid scintillation counting method was used for tritium measurement. A fully automated hematology analyzer was used to assess blood samples. The superoxide dismutase (SOD) and malondialdehyde (MDA) content was analyzed using commercial kits. Chahuangjing significantly increased decorporation and shortened the effective half-life of tritium. To a certain extent, Chahuangjing alleviated the HTO-induced reduction in white blood cells and elevated red blood cells after HTO exposure. Moreover, Chahuangjing alleviated the HTO-induced reduction in SOD activity and reduced MDA. Our study demonstrated that Chahuangjing can enhance the elimination of tritium and reduce free radicals to alleviate HTO-induced radiation injury.

The Tritiated Water Skin Barrier Integrity Test: Considerations for Acceptance Criteria with and Without 14C-Octanol

PURPOSE

A study was designed to assess barrier integrity simultaneously using separate compounds (probes) for polar and non-polar pathways through the skin, ³H₂O and ¹⁴C-octanol, respectively; and to determine whether the two probe approach could better define barrier integrity.

METHODS

A 5-min dose of water containing ³H₂O and ¹⁴C -octanol was applied to ex vivo human skin mounted in Franz diffusion cells. The receptor solution was sampled at 30 min, analyzed for ³H and ¹⁴C content, and the correlation between water and octanol absorption was determined by statistical tests suitable for non-normally distributed data. This study was conducted on skin from 37 donors with from 3 to 30 replicate skin sections per donor (a total of 426 sections).

RESULTS

The correlation between ³H₂O and ¹⁴C-octanol absorption was low (Pearson correlation coefficient = 0.3485). The ³H₂O absorption cutoff used in this study to select for a normal skin barrier rejected some sections in which ¹⁴C-octanol absorption was within normal limits and accepted others in which ¹⁴C-octanol absorption was abnormally high. The converse was true for ³H₂O absorption when the ¹⁴C-octanol-based cutoff was used.

CONCLUSIONS

The results of the ³H₂O test or of similar tests that primarily assess the permeability of polar pathways through the skin may not necessarily provide information relevant to the absorption of highly lipophilic compounds. Octanol, or another molecule that more closely matches the physicochemical attributes of the test compound, may characterize properties of the skin barrier that are more relevant to compounds of low water solubility.

A new tritiated water measurement method with plastic scintillator pellets

A new tritiated water measurement method with plastic scintillator pellets (PS-pellets) by using a conventional liquid scintillation counter was developed. The PS-pellets used were 3 mm in both diameter and length. A low potassium glass vial was filled full with the pellets, and tritiated water was applied to the vial from 5 to 100 μl. Then, the sample solution was scattered in the interstices of the pellets in a vial. This method needs no liquid scintillator, so no liquid organic waste fluid is generated. The counting efficiency with the pellets was approximately 48 % when a 5 μl solution was used, which was higher than that of conventional measurement using liquid scintillator. The relationship between count rate and activity showed good linearity. The pellets were able to be used repeatedly, so few solid wastes are generated with this method. The PS-pellets are useful for tritiated water measurement; however, it is necessary to develop a new device which can be applied to a larger volume and measure low level concentration like an environmental application.

The Role of miR-34a in Tritiated Water Toxicity in Human Umbilical Vein Endothelial Cells

In this work, we investigated the toxic effects of tritiated water (HTO) on the cardiovascular system. We examined the role of microRNA-34a (miR-34a) in DNA damage and repair in human umbilical vein endothelial cells (HUVECs) exposed to HTO. Cell proliferation capacity was evaluated by cell counting, and miR-34a expression was detected using quantitative PCR (QT-PCR). The Comet assay and γ-H2AX immunostaining were used to measure DNA double-strand breaks (DSBs). Reverse transcription polymerase chain reaction was used to measure the expression level of c-myc messenger RNA (mRNA). The cells exposed to HTO showed significantly lower proliferation than the control cells over 3 days. The DNA damage in the HTO group was more severe than that in the control group, at each time point examined. The expression of miR-34a mimics caused increased DNA DSBs whereas that of the miR-34a inhibitor caused decreased DNA DSBs. The proliferation viability was the opposite for the miR-34a mimics and inhibitor groups. The expression levels of c-myc mRNA in cells transfected with miR-34a mimics were lower than that in cells transfected with the miR-34a-5p inhibitor, at 0.5 hours and 2 hours after transfection. In summary, miR-34a mediates HTO toxicity in HUVECs by downregulating the expression of c-myc.

Massic Activity Ratios of the NBS/NIST Tritiated-Water Standards Issued Between 1954 and 1999

As part of the preparation and calibration of three new National Institute of Standards and Technology (NIST) tritiated-water radioactivity Standard Reference Materials (SRMs), the massic-activity (activity of the sample divided by the mass of the sample) ratios of all of the available NBS/NIST tritiated-water SRMs issued between 1954 and 1999 were measured using liquid-scintillation (LS) counting. Four of the tritiated-water standards (SRMs 4361, 4926B, 4927C, and 4927D) were not available for measurement. All of the other tritiated-water standards (SRMs 4361B, 4361C, 4926, 4926C, 4926D, 4926E, 4927, 4927B, 4927E, and 4927F) were available, having been stored in flame-sealed glass ampoules. Where possible, massic-activity ratios measured by liquid-scintillation counting are compared with massic-activity ratios calculated from gravimetric dilution factors. The agreement is well within the stated uncertainties. For two of the tritiated-water standards that were not available for measurement (SRMs 4361 and 4926B), massic-activity ratios calculated from gravimetric dilution factors are available.