We have applied an algorithm to improve the accuracy of particle identification and centroid coordinates for each particle image in particle tracking technique. The algorithm introduced two techniques; 1) cutting off by each threshold at the peak in the pixel intensity distribution for each image of local area around the particle, and 2) calculation of the centroid based on pixel intensities in the original image of the particle instead of binarized data. The former properly cuts the noise in the background for each particle which has large variety in level particle by particle due to fluctuating illuminations and out-of-focus particles in the image, and the latter avoids the loss of accuracy by the commonly used binarization. We have demonstrated that the algorithm significantly improves the accuracy in determination of centroid coordinates and the correctness in particle identification. We have also validated the advantage of the algorithm in accuracy by applying the algorithm to a sequence of confocal microscopy images of diffusing particles in a polysaccharide solution. This algorithm will be significantly useful in particle tracking technique for biological systems, especially for fluorescence microscopy observations with considerable obstructive stray fluorescent signals.
In this study, we try to extract the dynamics of the dislocations by measuring the time auto-correlation function of the scattered light intensity in the dilute lamellar phase. Our finding is that the lyotropic lamellar phase shows a bimodal decay of the correlation function. Fitting with the dispersion relation for the undulation fluctuation indicates that the fast mode is attributed to the undulation fluctuation of bilayer membranes. On the other hand, the slow relaxation mode is not explained by the undulation fluctuation. We interpret that the slow mode would be originated from a climb motion of the dislocation. Bimodal relaxation process would be attributed to a heterogeneous distribution of the dislocations in the lamellar structure.
Objective: To investigate the characteristics of the ratio of extracellular water (ECW) to total body water (TBW) volume (ECW/TBW) in a large group of healthy adults, measured by multi-frequency bioelectrical impedance (bioimpedance) analysis (MF-BIA). Subjects and methods: The correlation between ECW and TBW was studied in 957 healthy adults who underwent general medical examinations. Differences between measured and predicted ECW from ECW–TBW correlation equations (ΔECW) were calculated, and possible factors for non-zero ΔECW were explored. To investigate the influence of percent fat mass (%FM) on ECW/TBW, the ECW/TBW values of “lean” and “obese” groups, classified by %FM, were compared. ECW/TBW was also compared between “non-obese” and “obese class I-II” groups, classified by the body mass index for both genders. Results: ECW and TBW showed strong positive correlations in both genders. ΔECW was within ±0.2 L and increased with advancing age; ECW/TBW also increased. There were no significant differences in ECW/TBW between the “lean” and “obese” groups in either gender, or between the “non-obese” and “obese class I-II” groups in the female group. Conclusions: ECW/TBW measured by MF-BIA was considered to be an index of body water distribution in healthy adults ranging from “lean” to “obese class I-II,” which is not significantly affected by body fat.
Actin stress fibers (SFs) generate tension and play crucial roles in multiple cellular functions. However, it remains unclear how the tension changes in a single SF during cell movement on a substrate. In this study, we developed a new method to analyze the change in tension in a single SF in a cell with a Förster resonance energy transfer (FRET)-based tension sensor. With this new method, we have evaluated the relationship between the movement of SFs in the bottom of an MC3T3-E1 cell and their FRET ratio change, i.e., the tension change, for the first time to our knowledge. We found that the tension in SFs decreases when they rotate. The tension had no significant correlation with their translation nor with their length change.