Methylmercury Determination in Fish by Direct Mercury Analyzer.

BACKGROUND: There are two methods for quantifying methylmercury (MeHg) in fish using GC-electron capture detection (ECD): AOAC INTERNATIONAL Official Method 988.11 and the Korean Food Code (KFC) method. Both of these methods consume a large amount of chemicals and require long pretreatment times because of several complicated MeHg extraction steps. OBJECTIVE: In this study, a new method for the simple and rapid determination of MeHg in fish has been developed. The method is based on the investigation of oxygen combustion-gold amalgamation using a direct mercury analyzer (DMA) after the complete removal of MeHg by organic extraction and back-extraction to an aqueous medium. METHODS: The DMA is suitable for the analysis of both solid and liquid materials and has a good detection limit. The developed method was validated by comparing the MeHg recoveries (%) of both certified reference materials and the market-purchased fish samples with the MeHg concentration obtained using the KFC method. RESULTS: The following parameters pertaining to the developed method were established: detection limit, 1.02 µg/kg; LOQ, 3.09 µg/kg; linearity (r), 0.9998; range, 0.1-300 µg/kg; and recovery, 95-97%. CONCLUSIONS: Our method is a promising alternative by virtue of its much simpler and faster sample pretreatment procedure, with a MeHg recovery as high as that of the KFC method. HIGHLIGHTS: The developed method enables the simultaneous analysis of total Hg and MeHg with only DMA equipment.

[Characteristics and Risk Factors for Falls in Tertiary Hospital Inpatients].

PURPOSE: The aim of this study was to explore characteristics of and risk factors for accidental inpatient falls. METHODS: Participants were classified as fallers or non-fallers based on the fall history of inpatients in a tertiary hospital in Seoul between June 2014 and May 2015. Data on falls were obtained from the fall report forms and data on risk factors were obtained from the electronic nursing records. Characteristics of fallers and non-fallers were analyzed using descriptive statistics. Risk factors for falls were identified using univariate analyses and logistic regression analysis. RESULTS: Average length of stay prior to the fall was 21.52 days and average age of fallers was 61.37 years. Most falls occurred during the night shifts and in the bedroom and were due to sudden leg weakness during ambulation. It was found that gender, BMI, physical problems such elimination, gait, vision and hearing and medications such as sleeping pills, antiarrhythmics, vasodilators, and muscle relaxant were statistically significant factors affecting falls. CONCLUSION: The findings show that there are significant risk factors such as BMI and history of surgery which are not part of fall assessment tools. There are also items on fall assessment tools which are not found to be significant such as mental status, emotional unstability, dizziness, and impairment of urination. Therefore, these various risk factors should be examined in the fall risk assessments and these risk factors should be considered in the development of fall assessment tools.

Caenorhabditis elegans mitofilin homologs control the morphology of mitochondrial cristae and influence reproduction and physiology.

Human mitofilin is a mitochondrial protein that controls cristae formation. Here, we investigated the role of the Caenorhabditis elegans mitofilin homologs, IMMT-1 and -2, in reproduction, physiology, and mitochondrial cristae formation. Mutation of either immt-1 or immt-2 produced defects in germline development and egg-laying. These defects were exacerbated by the double mutation, which greatly reduced motility, increased levels of reactive oxygen species, decreased mitochondrial mass, and imparted resistance to oxidative stress. Cryo-electron microscopy and electron tomography revealed that each of the single mutations resulted in curved and stacked mitochondrial crista tubules as well as a reduced number of crista junctions. The immt-2 mutation was also associated with the presence of outer mitochondrial membrane pores, which were larger in the double mutant. IMMT-1 and IMMT-2 proteins were localized to the inner mitochondrial membrane, as seen by immunoelectron microscopy, and they behaved as oligomers or large complexes with F(1)F(0) ATP synthase in native polyacrylamide gel electrophoresis. These findings suggest that the two C. elegans mitofilin isoforms have non-overlapping functions in controlling mitochondrial cristae formation.

Three-dimensional structure of the cytoskeleton in Trichomonas vaginalis revealed new features.

The flagellated protozoan Trichomonas vaginalis has been widely studied owing to its medical significance and unique structure. The complicated three-dimensional (3D) structure of the cellular components of T. vaginalis was reconstructed from serial sections to enable observation of the spatial features of the whole cell. Electron tomography was used to examine the detailed structure of the cellular organelles. Tomographic reconstruction showed the mastigont system and the parabasal filament of T. vaginalis in detail. The last thin filament (Pf3) was located close to the adjacent filament, and the two filaments appeared to be vertically parallel in the cross-sectional view. It is likely that Pf3 cannot be distinguished from the adjacent filament in 2D images obtained from transmission electron microscopy. Our 3D reconstruction of T. vaginalis revealed the presence of an additional striated fiber, and 3D reconstruction by electron tomography showed twisting of the split parabasal filament.