Examining the assembly pathways and active microtubule mechanics underlying spindle self-organization

The bipolar organization of the microtubule-based mitotic spindle is essential for the faithful segregation of chromosomes in cell division. Despite our extensive knowledge of genes and proteins, the physical mechanism of how the ensemble of microtubules can assemble into a proper bipolar shape remains elusive. Here, we study the pathways of spindle self-organization using cell-free Xenopus egg extracts and computer-based automated shape analysis. Our microscopy assay allows us to simultaneously record the growth of hundreds of spindles in the bulk cytoplasm and systematically analyze the shape of each structure over the course of self-organization. We find that spindles that are maturing into a bipolar shape take a route that is distinct from those ending up with faulty structures, such as those of a tripolar shape. Moreover, matured structures are highly stable with little occasions of transformation between different shape phenotypes. Visualizing the movement of microtubules further reveals a fraction of microtubules that assemble between extra poles and push the poles apart, suggesting the presence of active extensile force that prevents pole coalescence. Together, we propose that a proper control over the magnitude and location of the extensile, pole-pushing force is crucial for establishing spindle bipolarity while preventing multipolarity.Comment: 22 pages, 5 + 2 figure

IR Absorption Nnalysis of Oxidation Behaviors of Nano-composite Phases with β-FeSi2 Nanocrystals and Si

We have investigated oxidation behaviors of nano-composite phase with β-FeSi2 nanocrystals (β-NCs) and Si on Si substrates. IR absorption measurements revealed that only oxidation of Si into SiO2 proceeded in the nano-composite phase. This fact is very important for realization of a novel composite phase with β-NCs and SiO2, which may contribute to enhancement of light emission and to prevent a large thermal quenching of light emission observed in the composite phase with β-NCs and Si.International Conference and Summer School on Advanced Silicide Technology 2014, July 19–21, 2014, Tokyo, Japa

Photoluminescence Property of Nano-composite Phases of β-FeSi2 Nanocrystals Embedded in SiO2

We have investigated photoluminescence (PL) behaviors of nano-composite phase of β-NCs embedded in SiO2 (β-NCs/SiO2). The inhomogeneous spectra consisting of the A, B, and C emission bands were observed. PL enhancement also was confirmed in comparison with β-NCs/Si. Under high pumping rate, we observed PL spectra near room temperatures (~270 K). This fact means that oxidation of the nano-composite phase can contribute to reduction of thermal quenching, which may come from increase of band offsets around β-NCs.International Conference and Summer School on Advanced Silicide Technology 2014, July 19–21, 2014, Tokyo, Japa

TORC1 regulates autophagy induction in response to proteotoxic stress in yeast and human cells

Misfolded and aggregated proteins are eliminated to maintain protein homeostasis. Autophagy contributes to the removal of protein aggregates. However, if and how proteotoxic stress induces autophagy is poorly understood. Here we show that proteotoxic stress after treatment with azetidine-2-carboxylic acid (AZC), a toxic proline analog, induces autophagy in budding yeast. AZC treatment attenuated target of rapamycin complex 1 (TORC1) activity, resulting in the dephosphorylation of Atg13, a key factor of autophagy. By contrast, AZC treatment did not affect target of rapamycin complex 2 (TORC2). Proteotoxic stress also induced TORC1 inactivation and autophagy in fission yeast and human cells. This study suggested that TORC1 is a conserved key factor to cope with proteotoxic stress in eukaryotic cells

Evaluation of calibration factor of OSLD toward eye lens exposure dose measurement of medical staff during IVR

The eye lens is a sensitive organ of which an x‐ray exposure dose should be managed during interventional radiology (IVR). In the actual situations, the eye lens is exposed to scattered x‐rays; they have different from the standard x‐ray energies which are used for general dose calibration of the dosimeter. To perform precise dose measurement, the energy dependence of the dosimeter should be properly accounted for when calibrating the dosimeter. The vendor supplies a calibration factor using 80‐kV diagnostic x‐rays under a free‐air condition. However, whether it is possible to use this calibration factor to evaluate the air kerma during the evaluation of the eye lens dose is unclear. In this paper, we aim to precisely determine calibration factors, and also examine the possible application of using a vendor‐supplied calibration factor. First, the x‐ray spectrum at the eye lens position during fluoroscopy was measured with a CdTe x‐ray spectrometer. We mimicked transfemoral cardiac catheterization using a human‐type phantom. Second, we evaluated the doses and calibration factors at three dosimetric points: front and back of protective goggles, and the front of the head (eye lens position). We used the measured x‐ray spectrum to determine the incident photon distribution in the eye lens regions, and x‐ray spectra corresponding to the dosimetric points around the eye lens were estimated using Monte Carlo simulation. Although the calibration factors varied with dosimetric positions, we found that the factors obtained were similar to the vendor‐supplied calibration factor. Furthermore, based on the experiment, we propose a practical way to calibrate an OSL dosimeter in an actual clinical situation. A person evaluating doses can use a vendor‐supplied calibration factor without any corrections for energy dependences, only when they add a systematic uncertainty of 5%. This evidence will strongly support actual exposure dose measurement during a clinical study

Changes in Cell Morphology Are Coordinated with Cell Growth through the TORC1 Pathway

SummaryBackgroundGrowth rate is determined not only by extracellular cues such as nutrient availability but also by intracellular processes. Changes in cell morphology in budding yeast, mediated by polarization of the actin cytoskeleton, have been shown to reduce cell growth.ResultsHere we demonstrate that polarization of the actin cytoskeleton inhibits the highly conserved Target of Rapamycin Complex 1 (TORC1) pathway. This downregulation is suppressed by inactivation of the TORC1 pathway regulatory Iml1 complex, which also regulates TORC1 during nitrogen starvation. We further demonstrate that attenuation of growth is important for cell recovery after conditions of prolonged polarized growth.ConclusionsOur results indicate that extended periods of polarized growth inhibit protein synthesis, mass accumulation, and the increase in cell size at least in part through inhibiting the TORC1 pathway. We speculate that this mechanism serves to coordinate the ability of cells to increase in size with their biosynthetic capacity

Iron and Nickel Line Diagnostics for the Galactic Center Diffuse Emission

We have observed the diffuse X-ray emission from the Galactic center (GC) using the X-ray Imaging Spectrometer (XIS) on Suzaku. The high-energy resolution and the low-background orbit provide excellent spectra of the GC diffuse X-rays (GCDX). The XIS found many emission lines in the GCDX near the energy of K-shell transitions of iron and nickel. The most pronounced features are FeI K alpha at 6.4 keV and K-shell absorption edge at 7.1 keV, which are from neutral and/or low ionization states of iron, and the K-shell lines at 6.7 keV and 6.9 keV from He-like (FeXXV K alpha) and hydrogenic (FeXXVI Ly alpha) ions of iron. In addition, K alpha lines from neutral or low ionization nickel (NiI K alpha) and He-like nickel (NiXXVII K alpha), and FeI K beta, FeXXV K beta, FeXXVI Ly beta, FeXXV K gamma and FeXXVI Ly gamma are detected for the first time. The line center energies and widths of FeXXV K alpha and FeXXVI Ly alpha favor a collisional excitation (CE) plasma for the origin of the GCDX. The electron temperature determined from the line flux ratio of FeXXV K alpha / FeXXV K beta is similar to the ionization temperature determined from that of FeXXV K alpha /FeXXVI Ly alpha. Thus it would appear that the GCDX plasma is close to ionization equilibrium. The 6.7 keV flux and temperature distribution to the galactic longitude is smooth and monotonic,in contrast to the integrated point source flux distribution. These facts support the hypothesis that the GCDX is truly diffuse emission rather than the integration of the outputs of a large number of unresolved point sources. In addition, our results demonstrate that the chemical composition of Fe in the interstellar gas near the GC is constrained to be about 3.5 times solar.Comment: 11 pages, 19 figures. Accepted for publication in PASJ Suzaku Special Issue (vol. 59 sp. 1

Eating-related distress and need for nutritional support of families of advanced cancer patients: A nationwide survey of bereaved family members

Background: A number of advanced cancer patients are suffering from physical and psychosocial burdens because of cancer cachexia, and these burdens also greatly impact on their family members and relationships between patients and family members. It is necessary to consider the psychosocial impact of cancer cachexia on family members of advanced cancer patients. Methods: A cross-sectional anonymous nationwide survey was conducted involving 925 bereaved family members of cancer patients who had been admitted to 133 inpatient hospices throughout Japan. Results: A total of 702 bereaved family members returned the questionnaires (response rate, 75.9%). Concerning eating-related distress, 'I served what the patient wanted without consideration of calories and nutritional composition' was highest (75.1%), and 'I tried making many kinds of meals for the patient' and 'I was concerned about planning meals for the patient every day' followed (63.0% and 59.4%, respectively). The top 5 of the 19 items were categorized as 'fighting back'. Need for nutritional support was high (72.2%), and need for explanations about the reasons for anorexia and weight loss of patients was moderate (41.4%). Explanatory factor analysis of eating-related distress identified the following four domains: (factor 1) feeling that family members forced the patient to eat to avoid death, (factor 2) feeling that family members made great efforts to help the patient eat, (factor 3) feeling that eating was a cause of conflicts between the patient and family members, and (factor 4) feeling that correct information was insufficient. Results of multiple logistic regression analysis showed that spouse, fair/poor mental status, factors 1, and 4 were identified as independent determinants of major depression (odds ratio [OR] 3.27 [95% confidence interval (CI) 1.24-8.60], P=0.02; OR 4.50 [95% CI 2.46-8.25], P<0.001; OR 2.51 [95% CI 1.16-5.45], P=0.02; OR 2.33 [95% CI 1.13-4.80], P=0.02, respectively). Conclusions: A number of family members of advanced cancer patients experienced high levels of eating-related distress and had a need for nutritional support