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Organ culture systems are useful for elucidating the process of testicular differentiation from mammalian undifferentiated genetically male gonads, as they permit various experiments, including experiments involving the control of gene expression. However, without addition of testicular differentiation-related factors, it is difficult to induce the formation of testis cord from immature gonads by a time point earlier 12 tail somites (ts) that corresponding to 11.0 days post coitum (dpc). In this study, we attempted to establish an organ culture system that induces testis formation from immature gonads (around 8 ts: 10.5 dpc) just before Sry (sex-determining region of the Y chromosome) expression. A paired gonad-mesonephros complex of around 8 ts was placed in the groove of an agarose gel block and put the semi-cylindrical piece of agarose gel to maintain the gonad morphology. The gonads were cultured in the gas phase for 96 hr. As a result, testis cord-like structures appeared in many genetically male gonads. Cells expressing the Sertoli cell markers Sox9 (SRY-box 9) and Amh (anti-Mullerian hormone) were observed, while granulosa cell marker Foxl2 (forkhead box L2) was not detected. In addition, Sox9- and Amh-expressing cells were observed throughout the entire gonad in many individuals. Amh mRNA expression was also upregulated. Surprisingly, formation of a partial testicular structure was observed from more immature gonads (6 ts). These results show that our gonadal organ culture system is useful for elucidating the regulation mechanism of Sry expression in undifferentiated bipotential gonads.

Neonicotinoid pesticides (NNs) act as agonists on nicotinic acetylcholine receptors (nAChRs) of insects, and there have been concerns about the effects of NNs on the health of mammals. Since nAChRs are expressed in immune cells, it is possible that NNs disturb the immune system. However, few reports have examined the immunotoxicity of clothianidin (CLO), a widely-used NN. Here, we report the effects of CLO on immune organs and type IV allergic reactions in ear auricles. We orally administered CLO at 0, 30 and 300 mg/kg/day (CLO-0, 30 and 300) to Sprague-Dawley rats for 28 days. The effects were evaluated by organ and body weights, histopathology, and immunohistochemistry (TCRαβ, CD4, CD8, CD11b, CD68, CD103). In addition, some cecal contents were subjected to preliminary gut microbiota analysis, because microbiota contribute to host homeostasis, including the immunity. Our results showed loose stool, suppression of body weight gain, significant changes in organ weights (thymus: decreased; liver: increased) and changes of the gut microbiota in the CLO-300 group. There were no obvious histopathological changes in immune organs. Granulomas of the ear auricles were found in one rat of each of the CLO-30 and 300 groups, but CLO had no apparent effect on the thickness or immunohistochemistry in the ear auricles. We present new evidence that CLO affects the thymus and intestine, and might enhance the local inflammatory response. These findings should contribute to the appropriate evaluation of the safety of NNs in the future.

The poultice formulation is a patch containing a large amount of water. It is known that the water contained in the adhesive polymer layer (ADPL) of poultice affects the cooling sensation and skin permeability of the active pharmaceutical ingredient (API). In this study, we evaluated the relationship between the water content in a ketoprofen poultice formulation and the amount of time the poultice was left out at room temperature after removal from the airtight container, as well as the influence of the decreasing water content on the skin permeability of the API. After removing the poultice from the container for 1 h, the mass of the ADPL decreased by approximately 40%. When the near-infrared (NIR) spectrum of the ADPL of poultice was measured, the peaks reflecting the hydroxyl group were attenuated depending on the time left out at room temperature. It is suggested that the changes in the mass and NIR spectrum of the ADPL are caused by the change in the water content. Moreover, when the permeability of API was evaluated on hairless mouse skin, the cumulative skin permeation amount and flux decreased, while the lag time was prolonged as the time left out increased. These results suggest that the skin permeability of the API is impaired by water evaporation and that maintaining the water in the ADPL in poultice is very important from not only the viewpoint of cooling sensation, tackiness and moisturizing but also the skin permeability of the API.

Although neonicotinoids are among the major classes of pesticides that affect mammalian nervous systems, little is known about sex differences in their effects. This study aimed to examine whether the neurobehavioral effects of a neonicotinoid, clothianidin (CLO), differed between sexes. Male and female C57BL/6N mice were orally administered CLO (5 or 50 mg/kg) at or below the chronic no-observed-adverse-effect-level (NOAEL) and sub- jected to behavioral tests of emotional and learning functions. Changes in neuroactivity in several brain regions and the concentrations of CLO and its metabolites in blood and urine were measured. Acute CLO exposure caused sex-related behavioral effects; decreases in locomotor activities and elevation of anxiety-like behaviors were more apparent in males than in females. In addition, male-specific impairment of short- and long-term learning memory by CLO exposure was observed in both the novel recognition test and the Barnes maze test. Male- dominant increases in the number of c-fos positive cells were observed in the paraventricular thalamic nu- cleus in the thalamus and in the dentate gyrus in the hippocampus, which are related to the stress response and learning function, respectively. The concentrations of CLO and most metabolites in blood and urine were higher in males. These results support the notion that male mice are more vulnerable than females to the neuro- behavioral effects of CLO and provide novel insights into the risk assessment of neonicotinoids in mammalian neuronal function.

Neonicotinoids, which act as agonists of the nicotinic acetylcholine receptors of insects, are widely used pesticides worldwide. Although epidemiological studies revealed that the detection amounts of neonicotinoids in urine are higher in the elderly population than other age-groups, there is no available information regarding the risks of neonicotinoids to older mammals. This study was aimed to investigate aging-related differences in the behavioral effects of the neonicotinoid pesticide clothianidin (CLO). We acutely administered a sub-NOAEL level (5 mg/kg) of CLO to adult (12-week-old) and aging (90-week-old) mice and conducted four behavioral tests focusing on the emotional behavior. In addition, we measured the concentrations of CLO and its metabolites in blood, brain and urine. There were age-related changes in most parameters in all behavioral tests, and CLO significantly decreased the locomotor activity in the open field test and elevated plus-maze test in the aging group, but not in the adult group. The concentrations of most CLO and its metabolites were significantly higher in the blood and brain and were slightly lower in the urine in the aging group compared to the adult group. These findings should contribute to our understanding of age-related differences in the adverse effects of neonicotinoids in mammals.

Neonicotinoids (NNs), a widely used class of systemic pesticides, are regarded as exhibiting selective toxicity in insects. However, NNs are suspected of exerting adverse effects on mammals as well, including humans. To date, only adult male animal models have been subjected to general toxicity studies of NNs; fetuses have yet to be considered in this context. Here, we focused on the NN clothianidin (CLO) for the first quantitative LC–MS/MS analysis of maternal-to-fetal transfer and residual property of once-daily (single or multiple days), orally administered CLO and its metabolites in mice. The results revealed the presence of CLO and its five metabolites at approximately the same respective blood levels in both dams and fetuses. In the dams, CLO showed a peak value 1 h after administration, after which levels rapidly decreased at 3 and 6 h. In the fetuses of each group, levels of CLO were almost the same as those observed in the corresponding dams. The present results clearly demonstrated rapid passage of CLO through the placental barrier. However, metabolite-dependent differences observed in blood pharmacokinetics and residual levels. This is the first quantitative demonstration of the presence of CLO and its metabolites in fetal mouse blood.

Evaluation of accidental sodium leak, combustion, and its thermal consequence is one of the important issues to be assessed in the field of sodium-cooled fast reactor (SFR) since the liquid sodium is chemically active and might give thermal load to plant building structure due to its exothermic reaction with oxygen in air atmosphere. Therefore, many experimental investigations and numerical simulation tools development have been and still now are being carried out to understand the details of sodium fire behaviors and to contribute to the investigation and preparation of appropriate mitigation measures in the plant design. From various kinds of sodium fire situations, the present paper treats the sodium pool fire and subsequent heat transfer behavior in air atmosphere two-cell geometry both experimentally and analytically because such two-cell configuration is considered as the typical one to possess important characteristic of multi-compartment system seen in an actual plant. Main description of this paper consists of a sodium pool fire experiment that was performed in a rectangular-shaped two-cell system with an opening between the cells, and the discussion of the experimental results. Inner volume of the experimental cells is about 70 m3. The amount of used sodium and the prepared pool surface area in the experiment are about 55 kg and 2.25 m2, respectively. The experiment has provided the temperature data measured in more than 100 positions for atmospheric gas and structures other than the data of oxygen concentration and suspended sodium aerosols concentration in the cells. The analyses of the measured data clarify the basic characteristics of sodium pool combustion and consequential heat and mass transfer in the cells, for instance, suggesting several features of multidimensional thermal-hydraulic behaviors such as thermal stratification near the opening between the two cells. In the discussion, numerical analysis using a lumped-parameter based zonal model safety analysis code ‘SPHINCS’ and the comparison of its results with the experimental data are also carried out to investigate the validity and applicability of the code to this type of sodium fire situation.

The Japan Sodium-cooled Fast Reactor (JSFR) adopts a double boundary for all sodium components. In this paper, design measures are investigated against a secondary sodium fire inside the reactor building, which might be assumed as design extension conditions. Candidate sodium fire measures for the secondary sodium systems compared in terms of safety are the sodium drain, nitrogen injection, pressure release valve, catch pan, and drain system for leaked sodium. Various sodium fires in the steam generator room have been analyzed by the SPHINCS code to evaluate the performance of the candidate sodium fire measures.

High cycle thermal fatigue on a structure caused by thermal striping phenomena is one of the most important issues in the design of fast breeder reactors (FBRs). In development of numerical simulation codes and in plant design and estimation by using the numerical estimation code, implementation of verification and validation (V&V) is indispensable process and also scaling issue from the subscale experiments to the full scale reactor should be considered. Therefore, a procedure called as V2UP (verification and validation plus uncertainty quantification and prediction) was made by referring to the existing guidelines on V&V (ASME V&V-10 and 20) and the methodologies of the safety assessment (CSAU, ISTIR, EMDAP). The V2UP consisted of five components as follows: (1) phenomena analysis with the Phenomena Identification and Ranking Table (PIRT) method, (2) implementation of the V&V, (3) design and rearrangement of experiments for the V&V, (4) uncertainty quantification in each problem and integration of uncertainties and (5) numerical prediction (estimation) for the target issue. Although the complete application of the procedure has not been performed at this moment, a flow chart of the V2UP procedure was described in this paper with recent results of the examinations.

In a sodium-cooled fast reactor (SFR), if considering hypothetical severe accidental condition such as the steel liner failure of structural concrete caused by intensive leakage of liquid sodium (N...

In this study, the kinetic behavior of the sodium (Na)–silica (SiO2) reaction was investigated for an assessment method of reactivity/stability of siliceous concrete against the sodium–concrete reaction (SCR) by postulating a severe accidental condition in the sodium-cooled fast reactor (SFR). The reaction behavior was tracked using a differential scanning calorimetry (DSC) equipped with a videoscope for viewing the changes in the sample during the reaction. The reaction was characterized as a partially overlapping multistep process controlled by physico-geometrical reaction scheme. The kinetic behavior in view of the change in the temperature at the maximum reaction rate with heating rate was analyzed using the simplified Kissinger method and the approximated Ozawa method. Further by separating the kinetic data for the overall reaction into five component reaction stages, the kinetic information for the second and third reaction stages was extracted. By comparing the kinetic results, it was revealed that the kinetic results determined from the kinetic data at the maximum reaction rate can be interpreted as is for the major reaction stage (the third reaction stage) controlled by an autocatalytic reaction. In addition, the second reaction stage was characterized as a possible premonitory process for the major reaction stage. Through the comprehensive interpretation of the kinetic results, significance of the kinetic analysis for the Na–SiO2 reaction using DSC for the reactivity/stability evaluation against SCR and for the safety assessment of SFR is discussed.

In the numerical analysis of sodium fire event following coolant leakage in a sodium-cooled fast reactor, sufficient understanding is needed for the liquid jet atomization to estimate the combustion rate accurately. In the present work, a liquid jet was emanated vertically downward from a circular nozzle onto a liquid film formed on a horizontal plate. The droplets produced at the impact point were investigated. The splash ratio (the ratio of the mass of the splashed droplets to the jet flow rate) was measured under varied experimental conditions of nozzle diameter, fall height and flow rate of liquid jet. The experimental result depended significantly on the morphology of liquid jet upon impact. The splashing rate was negligibly small when the liquid jet impinged as the continuous jet but a significant amount of liquid was splashed when the liquid jet impinged as the broken jet. Thus, we developed a method to estimate the impact frequency. It was shown that the splash ratio can be correlated well if the impact frequency is included in the correlation.

JAEA has developed sodium fire analysis codes, SPHINCS and AQUA-SF, to evaluate the consequences of sodium fire events, which are a key issue in sodium-cooled fast reactor (SFR) plants. This paper describes a PIRT (Phenomena Identification and Ranking Table) process for such events. The present PIRT can be utilized to validate the sodium fire analysis codes. Because a sodium fire event in an SFR plant involves complex phenomena, various figures of merit (FOMs) for importance ranking could exist in the PIRT process. Therefore, the FOMs are specified through a factor analysis. Associated phenomena in a sodium fire event are identified through both element- and sequence-based phenomena analyses. The importance of each associated phenomenon is evaluated by considering the sequence-based analysis of associated phenomena related to the FOMs. Then, a ranking table for the event is established. An assessment matrix of important phenomena and experiments is completed. Sufficiency of experimental data is confirmed for the validation of models corresponding to the identified important phenomena in the sodium fire analysis codes. Additional assessments are discussed specifically for the aerosol module and the CFD module in three-dimensional codes from a perspective of careful validation.

A liquid jet is of considerable importance in many industrial fields including jet cleaning, jet engine and combustion. As an important example, the Monju nuclear power plant in Japan experienced a sodium leak in 1995. This led to a fire accident because the sodium reacted with oxygen in the air. To predict the significance of the fire accident, accurate evaluation of the amount of splashed droplets caused by the sodium jet impingement is of great importance. In this work, the relationship between the condition of a liquid jet and the amount of splashed droplets is explored experimentally. In the experiments, a liquid jet was emanated vertically downward from a circular nozzle onto a liquid film formed on a horizontal plate. Visualization using a high speed camera was performed to observe the condition of the liquid jet. From the nozzle, the mode of the liquid jet changed jet, lump and drop. Here, the jet mode means the continuous jet with smooth surface, the lump mode the continuous jet with disturbed surface and the drop mode the broken jet. Dependences of the transition length to each mode on the important parameters such as the jet velocity and the nozzle diameter were investigated. Measurement was also conducted for the splash ratio that is defined as the ratio of the amount of splashed droplets to the jet flow rate. It was found that the splash ratio is high when the liquid jet is in the drop mode at the impact point. It was shown that the splash ratio can be correlated well as a function of the impact Weber number and the Strouhal number of the droplets impinging the liquid film.Copyright © 2016 by ASME