Verification of permeability for ionic liquid into biological specimens by using a mass spectrometer

The pretreatment method with ionic liquids (ILs) is convenient for scanning electron microscope (SEM) observation of biological specimens. It needs neither fixation nor vacuum vapor deposition of metals to prevent fracture, deformation and charge-up. Although it was pointed out that the reason why the specimens are not fractured or deformed under the vacuum without fixation is the penetration of the ILs into cells and replacement with the intercellular water of the specimen, the experimental results were not yet self-consistent. In this study, in order to verify this hypothesis, we investigated whether the components of 1-ethyl-3-methylimidazolium methylphosphonate ([EMIM][MePO3]) are detectable by using a time-of-flight secondary ion mass spectrometer (TOF-SIMS) and liquid chromatography. It was found that the components of [EMIM][MePO3] could be detected from inside of the biological specimens. Moreover, it was verified that there is no fracture and deformation of the specimen, whose residual concentration of the IL on the surface would be less than the limit of detection by TOF-SIMS. Therefore, these experimental results explicitly show that penetration of [EMIM][MePO3] into the specimen and subsequent replacement with the intercellular water inside the body is the reason for preventing fracture and deformation of the specimen under the vacuum.

Ionic liquid treatment for efficient sample preparation of hydrated bone for scanning electron microscopy

This study presents a new protocol for preparing bone samples for scanning electron microscopy (SEM) using a room temperature ionic liquid (RTIL) treatment method. RTIL-based solutions can be adopted as an alternative to lengthy and laborious traditional means of preparation for SEM due to their unique low-vapour pressure and conductive properties. Applied to biological samples, RTILs can be used quickly and efficiently to observe hydrated, unfixed structures in typical SEM systems. This first-time feasibility study of the optimization of this protocol for bone was explored through various SEM modalities using two distinct ionic liquids, 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMI][BF₄]) and 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMI][BF₄]), at varying concentrations of 5, 10, and 25 % v/v in aqueous solution through an addition-based method. Based on qualitative observations in the SEM, a 60-second solution addition treatment of 10 % v/v [BMI][BF₄] performed the best in imaging hydrated, unfixed bone samples, resulting in minimal charge buildup and no solution pooling on the surface. The treatment was applied effectively to a variety of bone samples, notably flat and polished, as well as highly topographical bone fracture surfaces of both healthy and osteoporotic human bone samples. In comparison to conventionally dehydrated bone, the RTIL treatment better preserved the natural bone structure, resulting in minimal microcracking in observed structures.

Electron Microscopy Imaging Applications of Room Temperature Ionic Liquids in the Biological Field: A Review

For biological imaging using electron microscopy (EM), the use of room-temperature ionic liquids (RTILs) has been proposed as an alternative to traditional lengthy preparation methods. With their low vapor pressures and conductivity, RTILs can be applied onto hard-to-image soft and/or wet samples without dehydration - allowing for a more representative, hydrated state of material and opening the possibility for visualization of in situ physiological processes using conventional EM systems. However, RTILs have yet to be utilized to their full potential by microscopists and microbiologists alike. To this end, this review aims to provide a comprehensive summary of biological applications of RTILs for EM to bridge the RTIL, in situ microscopy, and biological communities. We outline future research avenues for the use of RTILs for the EM observation of biological samples, notably i) RTIL selection and optimization, ii) applications for live cell processes and iii) electron beam and ionic liquid interaction studies.

An experimental intraradicular biofilm model in the pig for evaluating irrigation techniques

BACKGROUND

We established an in vivo intraradicular biofilm model of apical periodontitis in pigs in which we compared the efficacy of different irrigant activation techniques for biofilm removal.

METHODS

Twenty roots from the deciduous mandibular second premolar of 5 male pigs were used. After pulpectomy, canals were left open for 2 weeks and then sealed for 4 weeks to enable the development of an intracanal biofilm. The intraradicular biofilms was evaluated using SEM and bacterial 16S rRNA gene-sequencing. To investigate the efficacy of biofilm removal, root canal irrigations were performed using conventional needle, passive ultrasonic, subsonic, or laser-activated irrigation. Real-time PCR was conducted to quantitate the remaining biofilm components. Statistical analysis was performed using ANOVA followed by a Tukey kramer post-hoc test with α = 0.05.

RESULTS

The pulp exposure model was effective in inducing apical periodontitis and SEM analysis revealed a multi-layer biofilm formation inside the root canal. 16S rRNA sequence analysis identified Firmicutes, Bacteroidetes, and Fusobacteria as the predominant bacterial phyla components, which is similar to the microbiome profile seen in humans. None of the tested irrigation techniques completely eradicated the biofilm components from the root canal, but the subsonic and laser-activated irrigation methods produced the lowest bacterial counts (p < 0.05).

CONCLUSIONS

An experimental intraradicular biofilm model has been successfully established in pigs. Within the limitations of the study, subsonic or laser-activated irrigation demonstrated the best biofilm removal results in the pig system.

Prognostic Value of EMT-inducing Transcription Factors (EMT-TFs) in Metastatic Breast Cancer: A Systematic Review and Meta-analysis

The epithelial-to-mesenchymal transition (EMT) is a vital control point in metastatic breast cancer (MBC). TWIST1, SNAIL1, SLUG, and ZEB1, as key EMT-inducing transcription factors (EMT-TFs), are involved in MBC through different signaling cascades. This updated meta-analysis was conducted to assess the correlation between the expression of EMT-TFs and prognostic value in MBC patients. A total of 3,218 MBC patients from fourteen eligible studies were evaluated. The pooled hazard ratios (HR) for EMT-TFs suggested that high EMT-TF expression was significantly associated with poor prognosis in MBC patients (HRs = 1.72; 95% confidence intervals (CIs) = 1.53–1.93; P = 0.001). In addition, the overexpression of SLUG was the most impactful on the risk of MBC compared with TWIST1 and SNAIL1, which sponsored fixed models. Strikingly, the increased risk of MBC was less associated with ZEB1 expression. However, the EMT-TF expression levels significantly increased the risk of MBC in the Asian population (HR = 2.11, 95% CI = 1.70–2.62) without any publication bias (t = 1.70, P = 0.11). These findings suggest that the overexpression of potentially TWIST1, SNAIL1 and especially SLUG play a key role in the aggregation of MBC treatment as well as in the improvement of follow-up plans in Asian MBC patients.

Orthoamide und Iminiumsalze, XCI. N,N′,N″-Peralkylierte Guanidiniumsalze – Ionische Flüssigkeiten als Hilfsmittel in der Elektronenmikroskopie

Polymeric organic materials, e.g. cellulose fibres or nylon 6 (perlon), as well as inorganic materials, e.g. ceramics, can be coated with liquid or solid guanidinium salts. The coated materials can be inspected by scanning electron microscopy (SEM). The contrast and brightness of the pictures depend on the heaviest atom present in the anions. The best brightness and contrast were obtained with N,N′,N″-peralkylated guanidinium tetraiodidobismutates(III), which were prepared for the first time together with other guanidinium chloridometallates (Sb, Pb, Bi). Biological samples (cell cultures) can also be investigated by SEM with the aid of the guanidinium tetrachloridobismutate 4b after simple sample preparation.

Structural analysis of cellulose acetate and zirconium alkoxide hybrid fibres

We investigated the detailed structures of organic–inorganic hybrid fibres composed of cellulose acetate (CA) and zirconium alkoxides (Zr(OR)₄) using various measurements.

Simple observation of Streptococcus mutans biofilm by scanning electron microscopy using ionic liquids

Scanning electron microscopy (SEM) has been successfully used to image biofilms because of its high resolution and magnification. However, conventional SEM requires dehydration and metal coating of biological samples before observation, and because biofilms consist mainly of water, sample dehydration may influence the biofilm structure. When coated with an ionic liquid, which is a kind of salt that exists in the liquid state at room temperature, biological samples for SEM observation do not require dehydration or metal coating because ionic liquids do not evaporate under vacuum conditions and are electrically conductive. This study investigates the ability of ionic liquids to allow SEM observation of Streptococcus mutans biofilms compared with conventional coating methods. Two hydrophilic and two hydrophobic ionic liquids, all of which are electronic conductors, are used. Compared with samples prepared by the conventional method, the ionic-liquid-treated samples do not exhibit a fibrous extracellular matrix structure and cracking on the biofilm surface. The hydrophilic ionic liquids give clearer images of the biofilm structure than those of the hydrophobic ionic liquids. This study finds that ionic liquids are useful for allowing the observation of biofilms by SEM without preparation by dehydration and metal coating.

SEM observation of hydrous superabsorbent polymer pretreated with room-temperature ionic liquids

Room-temperature ionic liquid (RTIL), which is a liquid salt at or below room temperature, shows peculiar physicochemical properties such as negligible vapor pressure and relatively-high ionic conductivity. In this investigation, we used six types of RTILs as a liquid material in the pretreatment process for scanning electron microscope (SEM) observation of hydrous superabsorbent polymer (SAP) particles. Very clear SEM images of the hydrous SAP particles were obtained if the neat RTILs were used for the pretreatment process. Of them, tri-n-butylmethylphosphonium dimethylphosphate ([P_{4, 4, 4, 1}][DMP]) provided the best result. On the other hand, the surface morphology of the hydrous SAP particles pretreated with 1-ethyl-3-methylimidazolium tetrafluoroborate ([C₂mim][BF₄]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]) was damaged. The results of SEM observation and thermogravimetry analysis of the hydrous SAP pretreated with the RTILs strongly suggested that most water in the SAP particles are replaced with RTIL during the pretreatment process.

Depletion of RNA-binding protein RBM8A (Y14) causes cell cycle deficiency and apoptosis in human cells

RBM8A (Y14) contains an RNA-binding motif and forms a tight heterodimer with Magoh. The heterodimer is known to be a member of the exon junction complex that forms on mRNA before export and it is required for mRNA metabolism processes such as splicing, mRNA export and nonsense-mediated mRNA decay. Recently, deficient cellular proliferation has been observed in RBM8A- or Magoh-depleted cells. These results prompted us to study the role of RBM8A in cell cycle progression of human tumour cells. The depletion of RBM8A in A549 cells resulted in poor cell survival and the accumulation of mitotic cells. After release from G1/S arrest induced by a double thymidine block, the RBM8A-silenced cells could not proceed to the next G1 phase beyond G2/M phase. Finally, the sub-G1 population increased and the apoptosis markers caspases 3/7 were activated. Silenced cells exhibited an increased frequency of multipolar or monopolar centrosomes, which may have caused the observed deficiency in cell cycle progression. Finally, silencing of either RBM8A or Magoh resulted in mutual downregulation of the other protein. These results illustrate that the RBM8A-Magoh mRNA binding complex is required for M phase progression and both proteins may be novel targets for anticancer therapy.

Ionic liquid-based observation technique for nonconductive materials in the scanning electron microscope: Application to the characterization of a rare earth ore

A new approach for preparing geological materials is proposed to reduce charging during their characterization in a scanning electron microscope. This technique was applied to a sample of the Nechalacho rare earth deposit, which contains a significant amount of the minerals fergusonite and zircon. Instead of covering the specimen surface with a conductive coating, the sample was immersed in a dilute solution of ionic liquid and then air dried prior to SEM analysis. Imaging at a wide range of accelerating voltages was then possible without evidence of charging when using the in-chamber secondary and backscattered electrons detectors, even at 1 kV. High resolution x-ray and electron backscatter diffraction mapping were successfully obtained at 20 and 5 kV with negligible image drifting and permitted the characterization of the microstructure of the zircon/fergusonite-Y aggregates encased in the matrix minerals. Because of the absence of a conductive layer at the surface of the specimen, the Kikuchi band contrast was improved and the backscatter electron signal increased at both 5 and 20 kV as confirmed by Monte Carlo modeling. These major developments led to an improvement of the spatial resolution and efficiency of the above characterization techniques applied to the rare earth ore and it is expected that they can be applied to other types of ores and minerals.

Proteasome inhibitors and knockdown of SMG1 cause accumulation of Upf1 and Upf2 in human cells

The ubiquitin-proteasome system (UPS) is one of the most promising anticancer drug targets of the century. However, the involved molecular mechanisms are still unclear. The nonsense-mediated mRNA decay (NMD) pathway is a highly conserved pathway which degrades nonsense mutation‑containing mRNA selectively and efficiently. In this pathway, the SMG1-Upf1-eRF (SURF) complex binds to Upf2 on the exon junction complex and finally causes degradation of nonsense-containing mRNA. To reveal the relationship between the UPS and NMD pathways, we analyzed the effects of proteasome inhibitors on Upf1 and Upf2. The data showed that treatment with proteasome inhibitors caused the accumulation of the Upf1 and Upf2 proteins in A549 cells. In addition, we found that knockdown of SMG1 also caused the upregulation of Upf1 and Upf2 proteins, which was confirmed by different target sequences of siRNA. SMG1 and UPS appear to participate in different pathways of the degradation of Upf1 and Upf2, since simultaneous treatment with both of them caused additive effects. This study demonstrated the quantitative regulation of Upf1 and Upf2 proteins by UPS and SMG1.

RNA-binding protein RBM8A (Y14) and MAGOH localize to centrosome in human A549 cells

RBM8A (Y14) is carrying RNA-binding motif and forms the tight heterodimer with MAGOH. The heterodimer is known to be a member of exon junction complex on exporting mRNA and is required for mRNA metabolisms such as splicing, mRNA export and nonsense-mediated mRNA decay. Almost all RBM8A-MAGOH complexes localize in nucleoplasm and shuttle between nuclei and cytoplasm for RNA metabolism. Recently, the abnormality of G2/M transition and aberrant centrosome regulation in RBM8A- or MAGOH-deficient cells has been reported. These results prompt us to the reevaluation of the localization of RBM8A-MAGOH in human cells. Interestingly, our immunostaining experiments showed the localization of these proteins in centrosome in addition to nuclei. Furthermore, the transiently expressed eYFP-tagged RBM8A and Flag-tagged MAGOH also co-localized with centrosome signals. In addition, the proximity ligation in situ assay was performed to detect the complex formation in centrosome. Our experiments clearly showed that Myc-tagged RBM8A and Flag-tagged MAGOH formed a complex in centrosome. GFP-tagged PLK1 also co-localized with Myc-RBM8A. Our results show that RBM8A-MAGOH complex is required for M-phase progression via direct localization to centrosome rather than indirect effect.

Inhibition of mTORC2 but not mTORC1 up-regulates E-cadherin expression and inhibits cell motility by blocking HIF-2α expression in human renal cell carcinoma

PURPOSE

Molecular targeted drugs, such as mTORC1 inhibitors, have been clinically popularized for advanced renal cell carcinoma treatment but metastasis is still a serious concern. mTORC2 has several important functions, including HIF-2α activation in malignant cells. HIF-2α suppresses E-cadherin expression, which is associated with tumor invasion and metastasis. We investigated whether mTORC2 regulates E-cadherin expression and controls cell motility during HIF-2α down-regulation in renal cell carcinoma cells.

MATERIALS AND METHODS

We used PP242, a dual inhibitor of mTORC1/mTORC2 and the mTORC1 specific inhibitor rapamycin. E-cadherin expression in 786-O cells was examined using real-time polymerase chain reaction, Western blot and immunocytochemical staining. Cell motility was analyzed by time-lapse microscopy and wound healing assay.

RESULTS

High E-cadherin expression was found in RCC4/VHL cells but low levels were found in VHL defective RCC4 and 786-O cells. HIF-2α expression was suppressed only in RCC4/VHL cells. In 786-O cells HIF-2α inhibition induced by the dual mTORC1/C2 inhibitor PP242 (0.05 to 0.5 μmol/L) resulted in a dose dependent increase in E-cadherin expression and the restored E-cadherin was localized at cell-to-cell junctions. Treatment with the mTORC1 inhibitor rapamycin resulted in no significant change. The migration of PP242 treated cells was significantly suppressed compared with those treated with rapamycin.

CONCLUSIONS

Results show that mTORC2 might regulate E-cadherin expression and suppress cell motility by controlling the mTORC2-HIF-2α signaling pathway. The dual inhibitor of mTORC1/C2 as a cadherin regulatory agent may be a novel therapeutic strategy with tumoricidal agents for advanced renal cell carcinoma.

New insights into the regulation of epithelial-mesenchymal transition and tissue fibrosis

Tissue fibrosis often presents as the final outcome of chronic disease and is a significant cause of morbidity and mortality worldwide. Fibrosis is driven by continuous expansion of fibroblasts and myofibroblasts. Epithelial-mesenchymal transition (EMT) is a form of cell plasticity in which epithelia acquire mesenchymal phenotypes and is increasingly recognized as an integral aspect of tissue fibrogenesis. In this review, we describe recent insight into the molecular and cellular factors that regulate EMT and its underlying signaling pathways. We also consider how mechanical cues from the microenvironment affect the regulation of EMT. Finally, we discuss the role of EMT in fibrotic diseases and propose approaches for detecting and treating fibrogenesis by targeting EMT.

Possibility of scanning electron microscope observation and energy dispersive X-ray analysis in microscale region of insulating samples using diluted ionic liquid

The possibility of scanning electron microscope (SEM) observation and energy dispersive X-ray (EDX) spectrometry analysis in microscale regions of insulating samples using diluted ionic liquid was investigated. It is possible to obtain clear secondary electron images of insulating samples such as a rock and mineral at 5,000 times magnification by dropping 10 μL of 1 wt% of 1-ethyl-3-methylimidazolium acetate (EMI-CH₃COO) diluted with ethanol onto the samples. We also obtained EDX spectra of the samples in microscale regions (~5 μm²) without overlapping EDX spectra of other minerals with different composition. It might be possible to perform quantitative analysis of the samples if a method that does not need standard samples is applied or an X-ray detector sensitive for light elements was attached. The method of dropping 1 wt% EMI-CH₃COO diluted with ethanol onto insulating samples is useful for SEM observation, EDX analysis in microscale regions, and the preservation of scarce rock and mineral samples because ionic liquid can be easily removed with acetone.

Observation of live ticks (Haemaphysalis flava) by scanning electron microscopy under high vacuum pressure

Scanning electron microscopes (SEM), which image sample surfaces by scanning with an electron beam, are widely used for steric observations of resting samples in basic and applied biology. Various conventional methods exist for SEM sample preparation. However, conventional SEM is not a good tool to observe living organisms because of the associated exposure to high vacuum pressure and electron beam radiation. Here we attempted SEM observations of live ticks. During 1.5×10⁻³ Pa vacuum pressure and electron beam irradiation with accelerated voltages (2–5 kV), many ticks remained alive and moved their legs. After 30-min observation, we removed the ticks from the SEM stage; they could walk actively under atmospheric pressure. When we tested 20 ticks (8 female adults and 12 nymphs), they survived for two days after SEM observation. These results indicate the resistance of ticks against SEM observation. Our second survival test showed that the electron beam, not vacuum conditions, results in tick death. Moreover, we describe the reaction of their legs to electron beam exposure. These findings open the new possibility of SEM observation of living organisms and showed the resistance of living ticks to vacuum condition in SEM. These data also indicate, for the first time, the usefulness of tick as a model system for biology under extreme condition.