Evidence that activation of Src family kinase is not required for fertilization-associated [Ca2+]i oscillations in mouse eggs

Recent evidence in marine invertebrate, frog, and zebrafish eggs suggests the involvement of a Src family kinase (SFK) in fertilization-induced Ca2+ release. In the present study, we have investigated whether activation of an SFK is required for initiation of intracellular Ca2+ ([Ca2+]i) oscillations in mouse fertilization. We detected a Hck-like protein and tyrosine-phosphorylated proteins in soluble and insoluble sperm fractions, respectively. However, the presence of these proteins did not correspond to the active fractions of porcine sperm extracts (pSE). Moreover, [Ca2+]i oscillations induced by pSE in mouse eggs were unaltered by pre-incubation of pSE with specific SFK inhibitors such as 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazol[3,4-d]-pyrimidine (PP2) or lavendustin A, despite the fact that the inhibitors were shown to be active both in vivo and in vitro. Another SFK inhibitor, peptide A, blocked oscillations when incubated with pSE prior to injection into eggs, but this inhibition required more than ten times the concentration reportedly required to inhibit SFK activity. In addition, pre-injection or pre-incubation of eggs with these inhibitors did not affect the ability of pSE to trigger [Ca2+]i oscillations in mouse eggs. Microinjection of a recombinant c-Src protein or mRNAs encoding constitutively active Src proteins did not induce [Ca2+]i release. Finally, when sperm and eggs, both of which were pre-treated with PP2, were fertilized, [Ca2+]i oscillations occurred normally. We can therefore conclude that activation of an SFK is neither necessary nor sufficient for triggering fertilization-induced [Ca2+]i oscillations.     

A general model of carcinogenesis (I)--Tumor evolution and gene deletion

Carcinogenesis is functionally a deletion alteration rather than addition of genetic information. Repressor genes may be more sensitive to 'neutral' mutations of DNA than those of structural genes, since selection pressure for deletion of repressors is extremely low in multicellular organisms. Dysfunction of repressors caused by genomic mutation induces autonomic expression of structural genes which is programmed a priori in each cell. Tumor progression can be explained by this deletion model with abnormal DNA repair. Alteration of DNA repairing units may be the initial mutation in carcinogenesis.     

Relationship between the energy distribution of electrostatic field change and lightning activity

A lightning strength parameter α (denoted as LSP or LAIDO), which is used for characterizing the phenomena of lightning activity, has been proposed, where α is defined by the characteristic energy obtained from the energy distribution of a radiated field component E in the electrostatic field changes produced by lightning discharge. Here, it is observed that the energy distribution of E_γ components is Maxwellian type. To prove more clearly the forementioned assumption from another viewpoint, changes of the amplitudes of the electrostatic field component E_S were measured and their distribution functions constructed. In the cloud-to-ground lightning discharges, the E_S components have a positive sign in the changes. However, those changes in the intercloud discharges are observed with either a negative or positive change depending on the distance between the striking point and the observation site. Therefore it is necessary to sum the numbers of occurrences of both positive and negative components for constructing an energy distribution of the E_S component. A fieldmill and a pair of doughnut-shaped electrostatic antennas are used in measuring the changes of the E_S component. As a result it is found that the changes of the amplitudes of the E_S components have a Maxwelliantype energy distribution. A characteristic energy β is defined which is obtained from the component of the electrostatic fields as a measure of LSP. Based on comparison of α and β it is clarified that β has the same characteristic nature with α. The lightning activity could be estimated from β.     

Effects of Heating Rate on Stress Evolution in Alkoxide-Derived Silica Gel-Coating Films

Silica gel films were deposited by spin coating on single-crystal Si wafers using an acid-catalyzed Si(OC₂H₅)₄ solution as a coating solution. The gel films were heated at various rates, where in situ stress measurement was conducted. In-plane tensile stress developed during the course of heating, and was found to be larger at lower heating rates at temperatures up to 350°C. The larger stress was thought to cause cracking at lower temperatures, which was previously observed at lower heating rates in in situ observation. The larger stress at lower heating rates was basically ascribed to the larger degrees of densification, which was revealed in the larger extent of reduction in thickness as well as in Si–OH/Si–O–Si and O–H/Si–O–Si infrared absorption band area ratios at lower heating rates. The difference in stress at different heating rates appeared to originate mainly in the difference observed at low temperatures below 130°C, suggesting that the heating rate particularly affects the densification that occurs via solvent evaporation. The increment in stress was reduced over 400°C when the heating rate was low, which was thought to result from the higher degree of densification already achieved below 400°C as well as the structural relaxation occurring at such high temperatures.     

Effects of supersonic treatment on the electrochemical properties and crystal structure of LiMn1.5Ni0.5O4 as a cathode material for Li ion batteries

The electrochemical properties and crystal structure of LiMn_1.5Ni_0.5O₄ treated with supersonic waves in an aqueous Ni-containing solution were investigated by performing charge-discharge tests, inductively coupled plasma (ICP) analysis, scanning electron microscopy (SEM), iodometry, X-ray diffraction (XRD), powder neutron diffraction and synchrotron powder XRD. The charge-discharge curve of LiMn_1.5Ni_0.5O₄ versus Li/Li⁺ has plateaus at 4.1 and 4.7 V. The 4.1 V versus Li/Li⁺ plateau due to the oxidation of Mn^3+/4+ was reduced by the supersonic treatment. During the charge-discharge cycling test at 25 °C, the supersonic treatment increased the discharge capacity of the 50th cycle. Rietveld analysis of the neutron diffraction patterns revealed that the Ni occupancy of the 4b site in LiMn_1.5Mn_0.5O₄, which is mainly occupied by Ni, was increased by the supersonic treatment. This result suggests that Ni²⁺ is partially substituted for Mn^3+/4+ during the supersonic treatment.     

Role of Tryptophan 38 in Loading Substrate Chain into the Active-site Tunnel of Cellobiohydrolase I from Trichoderma reesei

Cellobiohydrolase I from Trichoderma reesei ( Tr Cel7A) is one of the best-studied cellulases, exhibiting high activity towards crystalline cellulose. Tryptophan residues at subsites -7 and -4 (Trp40 and Trp38 respectively) are located at the entrance and middle of the tunnel-like active site of Tr Cel7A, and are conserved among the GH family 7 cellobiohydrolases. Trp40 of Tr Cel7A is important for the recruitment of cellulose chain ends on the substrate surface, but the role of Trp38 is less clear. Comparison of the effects of W38A and W40A mutations on the binding energies of sugar units at the two subsites indicated that the contribution of Trp38 to the binding was greater than that of Trp40. In addition, the smooth gradient of binding energy was broken in W38A mutant. To clarify the importance of Trp38, the activities of Tr Cel7A WT and W38A towards crystalline cellulose and amorphous cellulose were compared. W38A was more active than WT towards amorphous cellulose, whereas its activity towards crystalline cellulose was only one-tenth of that of WT. To quantify the effect of mutation at subsite -4, we measured kinetic parameters of Tr Cel7A WT, W40A and W38A towards cello-oligosaccharides. All combinations of enzymes and substrates showed substrate inhibition, and comparison of the inhibition constants showed that the Trp38 residue increases the velocity of substrate intake ( k _on for forming productive complex) from the minus side of the subsites. These results indicate a key role of Trp38 residue in processively loading the reducing-end of cellulose chain into the catalytic tunnel.     

Burning behavior of sedan passenger cars

Four full-scale fire experiments using 4-door sedan passenger cars were carried out. The cars were ignited either at the splashguard of the right rear wheel or at the left front seat in the passenger compartment with a gasoline spill. The temperature inside the burning car and the mass loss rate were measured. The burning of the 4-door sedan was composed of three compartmental fires: the engine compartment, the passenger compartment, and the rear part inclusive of the fuel. In the experiments where ignition was initiated at the splashguard, the flame spread in the following order: to the rear part of the car, to the passenger compartment, and to the engine compartment. Breakage of the window glass markedly affected the spread of fire into the passenger compartment. The quantity of gasoline in the fuel tank also affected the speed of spread of the fire, because the gasoline ignited at an early stage of the fire. In the experiment where ignition was initiated in the passenger compartment, the fire gained force after the windshield was broken entirely. The flame spread in the following order: to the passenger compartment, to the engine compartment, and to the rear part of the car. The temperature within the passenger compartment peaked at 1000 °C. The heat release rate (HRR) curves showed several peaks depending on the burning of the three compartments. The HRR increased markedly when the fire spread to several different parts of the car at the same time. The HHR peaked at 3 MW when the passenger compartment and fuel (gasoline) burned simultaneously. The measured HRR curves were characterized by superposition of a Boltzmann curve and a Gaussian curve in order to obtain a model, which allowed us to make a more precise prediction of the fire spread probability from a burning car to nearby structures. The HRRs of burning cars were described by the sum of HRR from each compartment.     

Dynamic centrifuge model tests and material point method analysis of the impact force of a sliding soil mass caused by earthquake-induced slope failure

Dynamic centrifuge model tests and associated analyses are carried out to develop a procedure for simulating the slope failure process during earthquakes and to evaluate the force of a sliding soil mass impacting a structure. This impact force is successfully measured in the dynamic centrifuge model tests using a slope height of 50 m in the prototype scale. The results of a pseudo-static limit equilibrium analysis, assuming a circular failure plane, show that a stability analysis can be an effective tool for evaluating the critical acceleration under which the slope failure starts, although it is not applicable for evaluating the runout distance or the impact force of the sliding soil mass to the structure. Therefore, an attempt is also made in this study to examine the applicability of empirical equations for evaluating the impact force by comparing the evaluated impact force using Hertz’s equation and an empirical equation based on fluid mechanics with the measured ones. The comparison reveals that these simple equations would not be able to estimate the impact force well, even though parameter setting is required for applying the equations. On the other hand, it is also found from a relevant analysis that the material point method (MPM) is an effective tool for simulating the failure behavior of a slope and for evaluating the impact force of a sliding soil mass induced by a slope failure.