Macrophage distribution density is tightly regulated within the body, yet the importance of macrophage crowding during in vitro culture is largely unstudied. Using a human induced pluripotent stem cell (iPSC)-derived macrophage model of tissue resident macrophages, we characterize how increasing macrophage culture density changes their morphology and phenotype before and after inflammatory stimulation. In particular, density drives changes in macrophage inflammatory cytokine and chemokine secretion in both resting and activated states. This density regulated inflammatory state is also evident in blood monocyte derived-macrophages, the human monocytic THP-1 immortalized cell line, and iPSC-derived microglia. Density-dependent changes appear to be driven by a transferable soluble factor, yet the precise mechanism remains unknown. Our findings highlight cell plating density as an important but frequently overlooked consideration of in vitro macrophage research relevant to a variety of fields ranging from basic macrophage cell biology to disease studies.
OH airglow observed by the ISUAL (Imager of Sprites and Upper Atmospheric Lightning) instrument on board the FORMOSAT 2 satellite is reported in this paper. The satellite is sun-synchronous and it returns to the same orbit at the same local time daily. By using this property, we can study the upper atmosphere in detail. With a CCD camera, ISUAL has measured the emission layers of OH Meinel band at 630 nm for several two-week periods in 2004 and 2007 in equatorial regions. ISUAL images are snapshots of the atmosphere 250 km (height) × 1200 km (horizontal distance). These images of OH airglow are analyzed to derive its peak height and latitudinal variations. ISUAL observation is unique in its capability of continuous observation of the upper atmosphere as the satellite travels from south to north along a specific orbit. However, 630 nm filter also measured O(1 D) at 200 km, and there are interferences between O(1 D) and OH airglows as as observed from a distance in space. We have studied the overlap of two airglows by simulations, and our final analyses show that OH airglow can be correctly derived with its average peak height of 89 ± 2.1 km usually lying within ±10° latitude about the equator. ISUAL data reveal detailed structures of equatorial OH airglow such as the existences of a few secondary maxima within the equatorial regions, and the oscillations of the peak latitudes. These results are discussed and compared with previous reports.
Airglow variability is a topic that has been studied for decades but an understanding of the role of the dynamical influence underlying this variability has only been achieved recently. The UARS dynamics instruments, HRDI (High Resolution Doppler Imager) and WINDII (WIND Imaging Interferometer) have been instrumental in providing this understanding, because they measure both winds and emission rates, and so are able to determine the coupling between the two. But ground-based observations are also an essential ingredient to this understanding, which has grown through intercomparisons between dataset and models through workshops such as DYSMER. This presentation begins by describing the influence of the diurnal tide on oxygen and hydroxyl airglow emission rates, including the seasonal variation. This is followed by a description of two planetary scale disturbance phenomena, the springtime transition, and a stratospheric warming. Auroral influences are also considered. While these investigations cover a wide range of mechanisms there is an underlying thread which is that it is these large scale dynamical processes that are responsible for determining the distribution of the airglow patterns detected, and thus the distribution of concentration of atomic oxygen.
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