•Human has obtained an exceptionally expanded cerebral cortex during evolution.•There are a few notable structural transitions in evolution until human cerebral cortex had appeared.•Developmental ...programs of the cerebral cortex have been changed in evolution.•Three major classes of genetic changes relevant to the evolutionary alterations of human cortical development have been studied.
One of the most important questions in human evolutionary biology is how our ancestor has acquired an expanded volume of the cerebral cortex, which may have significantly impacted on improving our cognitive abilities. Recent comparative approaches have identified developmental features unique to the human or hominid cerebral cortex, not shared with other animals including conventional experimental models. In addition, genomic, transcriptomic, and epigenomic signatures associated with human- or hominid-specific processes of the cortical development are becoming identified by virtue of technical progress in the deep nucleotide sequencing. This review discusses ontogenic and phylogenetic processes of the human cerebral cortex, followed by the introduction of recent comprehensive approaches identifying molecular mechanisms potentially driving the evolutionary changes in the cortical development.
Essentials
The role of C‐type lectin‐like receptor‐2 (CLEC‐2) in cancer progression is unclear.
CLEC‐2‐depleted mouse model is generated by using a rat anti‐mouse CLEC‐2 monoclonal antibody.
CLEC‐2 ...depletion inhibits hematogenous tumor metastasis of podoplanin‐expressing B16F10 cells.
CLEC‐2 depletion prolongs cancer survival by suppressing thrombosis and inflammation.
Summary
Background
C‐type lectin‐like receptor 2 (CLEC‐2) is a platelet activation receptor of sialoglycoprotein podoplanin, which is expressed on the surface of certain types of tumor cells. CLEC‐2–podoplanin interactions facilitate hematogenous tumor metastasis. However, direct evidence of the role of CLEC‐2 in hematogenous metastasis and cancer progression is lacking.
Objective and methods
We generated immunological CLEC‐2‐depleted mice by using anti‐mouse CLEC‐2 monoclonal antibody 2A2B10 and investigated whether CLEC‐2 promoted hematogenous tumor metastasis and tumor growth and exacerbated the prognosis of mice bearing podoplanin‐expressing B16F10 melanoma cells.
Results
Our results showed that hematogenous metastasis was significantly inhibited in CLEC‐2‐depleted mice. B16F10 cells co‐cultured with wild‐type platelets, but not with CLEC‐2‐deficient platelets, showed increased proliferation. However, B16F10 cell proliferation was not inhibited in CLEC‐2‐depleted mice. Histological analysis showed that thrombus formation in tumor vessels was significantly inhibited and functional vessel density was significantly increased in CLEC‐2‐depleted mice. These data suggest that CLEC‐2 deficiency may inhibit thrombus formation in tumor vessels and increase the density of functional vessels, thus improving oxygen and nutrient supply to tumors, indirectly promoting tumor proliferation. Furthermore, the overall survival of CLEC‐2‐depleted mice was significantly prolonged, which may be due to the suppression of thrombus formation in the lungs and subsequent inhibition of systemic inflammation and cachexia.
Conclusions
These data provide a rationale for the targeted inhibition of CLEC‐2 as a new strategy for preventing hematogenous tumor metastasis and for inhibiting cancer‐related thromboembolism.
Recent theoretical studies suggest the existence of low-mass, zero-metal stars in the current universe. To study the basic properties of the atmosphere of low-mass first stars, we perform ...one-dimensional magnetohydrodynamical simulations for the heating of coronal loops on low-mass stars with various metallicities. While the simulated loops are heated up to ≥106 K by the dissipation of Alfvénic waves originating from the convective motion irrespective of metallicity, the coronal properties sensitively depend on the metallicity. Lower-metal stars create hotter and denser coronae because the radiative cooling is suppressed. The zero-metal star gives more than 40 times higher coronal density than the solar-metallicity counterpart, and as a result, the UV and X-ray fluxes from the loop are several times higher than those of the solar-metallicity star. We also discuss the dependence of the coronal properties on the length of the simulated coronal loops.
ABSTRACT
We investigate the role of latitudinal differential rotation (DR) in the spin evolution of solar-type stars. Recent asteroseismic observation detected the strong equator-fast DR in some ...solar-type stars. Numerical simulations show that the strong equator-fast DR is a typical feature of young fast-rotating stars and that this tendency is gradually reduced with stellar age. Incorporating these properties, we develop a model for the long-term evolution of stellar rotation. The magnetic braking is assumed to be regulated dominantly by the rotation rate in the low-latitude region. Therefore, in our model, stars with the equator-fast DR spin down more efficiently than those with the rigid-body rotation. We calculate the evolution of stellar rotation in ranges of stellar mass, $0.9 \, \mathrm{M}_{\odot } \le M \le 1.2\, \mathrm{M}_{\odot }$, and metallicity, $0.5\, \mathrm{Z}_{\odot } \le Z \le 2\, \mathrm{Z}_{\odot }$, where M⊙ and Z⊙ are the solar mass and metallicity, respectively. Our model, using the observed torque in the present solar wind, nicely explains both the current solar rotation and the average trend of the rotation of solar-type stars, including the dependence on metallicity. In addition, our model naturally reproduces the observed trend of the weakened magnetic braking in old slowly rotating solar-type stars because strong equator-fast DR becomes reduced. Our results indicate that latitudinal DR and its transition are essential factors that control the stellar spin down.
The effect of applied stress during ultra-rapid annealing (URA) on the magnetic properties has been investigated for rapidly-solidified (Fe1-xCox)86B13Cu1 (x = 0–0.05) alloys. Nano-meter scale grains ...with an average size of about 15 nm and a small coercivity value of 5 ± 1 A/m are confirmed for all the alloys after URA at 763 K for 0.5 s. The saturation magnetic polarization (Js) of these nanocrystalline alloys shows a slight increase with Co content from 1.88 T at x = 0 to 1.94 T at x = 0.05. A clear creep-induced anisotropy (Ku) up to 460 ± 20 J/m3 is observed with a hard axis along the direction of applied tensile stress for x = 0–0.04 while an easy axis is confirmed in the same direction for x = 0.05. The saturation magnetostriction (λs) of nanocrystalline (Fe1-xCox)86B13Cu1 increases monotonously from + 13 ± 2 ppm to + 20 ± 2 ppm with an increase of x from 0 to 0.05 and the observed change in the anisotropy axis cannot be attributed to the bulk magnetoelastic effect. The magnetostriction was also measured for polycrystalline Fe1-xCox (x = 0–0.1) binary alloys prepared for comparison and λs of bcc-Fe is confirmed to change its sign from negative to positive by Co addition. A similar trend is confirmed for the local magnetostriction estimated for the bcc-Fe(Co) phase in the nanocrystalline samples by assuming the inverse effect of the local magnetostriction, suggesting that Ku in nanocrystalline (Fe1-xCox)86B13Cu1 (x = 0–0.05) alloys is due to the strain retained within the bcc-Fe(Co) nanocrystallites. Our results demonstrate that the shape of the hysteresis curve in the URA Fe-B based nanocrystalline alloys (HiB-Nanoperm) can be controlled by stress applied to the precursor amorphous ribbons during annealing.
•Creep-induced anisotropy is confirmed for HiB-Nanoperm annealed under stress.•A large uniaxial anisotropy up to 460 ± 20 J/m3 is realized by stress annealing.•Shape of hysteresis loops can be controlled by minor Co addition.•Low Hc of 5 ± 1 A/m and high Js of 1.88–1.94 T are obtained by rapid annealing.•Induced anisotropy is understood by inverse effect of the local magnetostriction.
Realization of a high-saturation magnetization comparable to that of Fe–Si steel in advanced Fe-rich nanocrystalline soft magnetic alloys is potentially a very effective approach to reducing the ...emission of greenhouse gasses. This potential has stimulated recent research on the development of new alloys with exceptionally high Fe concentrations. However, some nanocrystalline soft magnetic alloys at the Fe-richest compositions exhibit unexpectedly large values of field-induced magnetic anisotropy (Ku∼100Jm−3) which have a detrimental effect on the exchange-softening process in the nanostructures. Our viewpoint is that much attention must be paid to the induced anisotropies in order to utilize the full potential of the exchange-softening effect in Fe-rich nanocrystalline alloys. Possible origins of the large Ku value and the approach to suppressing the field-induced effect on Ku are discussed.
The mechanisms by which the diffusion rate in the plasma membrane (PM) is regulated remain unresolved, despite their importance in spatially regulating the reaction rates in the PM. Proposed models ...include entrapment in nanoscale noncontiguous domains found in PtK2 cells, slow diffusion due to crowding, and actin-induced compartmentalization. Here, by applying single-particle tracking at high time resolutions, mainly to the PtK2-cell PM, we found confined diffusion plus hop movements (termed "hop diffusion") for both a nonraft phospholipid and a transmembrane protein, transferrin receptor, and equal compartment sizes for these two molecules in all five of the cell lines used here (actual sizes were cell dependent), even after treatment with actin-modulating drugs. The cross-section size and the cytoplasmic domain size both affected the hop frequency. Electron tomography identified the actin-based membrane skeleton (MSK) located within 8.8 nm from the PM cytoplasmic surface of PtK2 cells and demonstrated that the MSK mesh size was the same as the compartment size for PM molecular diffusion. The extracellular matrix and extracellular domains of membrane proteins were not involved in hop diffusion. These results support a model of anchored TM-protein pickets lining actin-based MSK as a major mechanism for regulating diffusion.
Abstract
Recent observational and numerical studies show a variety of thermal structures in the solar chromosphere. Given that the thermal interplay across the transition region is a key to coronal ...heating, it is worth investigating how different thermal structures of the chromosphere yield different coronal properties. In this work, by MHD simulations of Alfvén-wave heating of coronal loops, we study how the coronal properties are affected by the chromospheric temperature. To this end, instead of solving the radiative transfer equation, we employ a simple radiative loss function so that the chromospheric temperature is easily tuned. When the chromosphere is hotter, because the chromosphere extends to a larger height, the coronal part of the magnetic loop becomes shorter, which enhances the conductive cooling. A larger loop length is therefore required to maintain the high-temperature corona against the thermal conduction. From our numerical simulations we derive a condition for the coronal formation with respect to the half loop length
l
loop
in a simple form:
l
loop
>
aT
min
+
l
th
, where
T
min
is the minimum temperature in the atmosphere, and parameters
a
and
l
th
have negative dependencies on the coronal field strength. Our conclusion is that the chromospheric temperature has a nonnegligible impact on coronal heating for loops with small lengths and weak coronal fields. In particular, the enhanced chromospheric heating could prevent the formation of the corona.
Abstract
By performing
N
-body simulations, we investigated the fundamental processes of collisions between dust aggregates composed of submicron-sized icy dust monomers. We examined the mass ...distribution of fragments in the collisional outcomes in a wide range of the mass ratio and the collision velocity between colliding dust aggregates. We derived analytic expressions of the mass distribution of large remnants and small fragments by numerical fitting to the simulation results. Our analytic formulae for masses of the large remnants can reproduce the contribution of mass transfer from a large target to a small projectile, which occurs for a mass ratio of ≳3 and is shown in a previous study. We found that the power-law index of the cumulative mass distribution of the small fragments is independent of the mass ratio and only weakly dependent on the collision velocity. On the other hand, the mass fraction of fragments of individual dust monomers decreases with an increasing total mass of colliding aggregates for a fixed mass ratio. This tendency implies that multiple hierarchical disruptive collisions (i.e., collisions between fragments, and collisions between fragments of fragments) are required for producing a large number of individual dust monomers via collisional fragmentation. Our fragment model suggests that the total geometric cross section integrated over the fragments is estimated to be about the same order as the geometric cross section of the target.
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