600 research outputs found
Platelets Prime Hematopoietic-Vascular Niche to Drive Angiocrine-Mediated Liver Regeneration
A critical function for blood vessels is that they secrete paracrine factors necessary for development, homeostasis and repair of the rest of all organs. Among them, the liver is a highly vascular organ, and can undergo regeneration after injury. This liver regeneration process is governed by dynamic interplay between hepatocytes and non-parenchymal cells, liver sinusoidal endothelial cells (LSECs). However, how factors produced from LSECs triggered by injury remains to be defined. Following mouse in vivo liver injury model, activated platelets deploy stromal cell-derived factor 1 and vascular endothelial growth factor A to stimulate CXCR7+ LSECs, orchestrating hepatic regeneration. Upon injection of carbon tetrachloride, platelets and CD11b+VEGFR1+ myeloid cells were recruited to LSECs enabling to replenish liver mass. Liver regeneration was impaired in thrombopoietin-deficient (Thpo-/-) mice repressing platelet production. This impeded regeneration phenotype was recapitulated in mice with either conditional ablation of Cxcr7 in LSEC (Cxcr7iÎ/iÎ) or Vegfr1 in myeloid cell (Vegfr1lysM/lysM). These mice exhibited suppressed expression of hepatocyte growth factor and Wnt2, two crucial hepatocyte propagation factors. Administration of recombinant thrombopoietin restored the prohibited liver regeneration in the tested genetic models. These results suggest that platelets and myeloid cells activate the vascular niche to produce pro-regenerative endothelial paracrine factors. Modulating this âhematopoietic-vascular nicheâ might help to develop regenerative therapy strategy for hepatic disorders
Characterization of highly dispersed Ni/Al2O3 catalysts by EXAFS analysis of higher shells
The size and morphology of Ni/Al2O3 catalysts in the oxidic, reduced, and passivated state were determined by EXAFS analysis of the higher shells around the Ni atoms. In the oxidic state, the Ni cations were present in small NiOx particles with predominant (111) plane. Below 4.5 wt% Ni loading, the NiOx particles consisted of one Ni layer, and of two or three Ni layers above 4.5 wt% Ni. A Ni-Al contribution was observed in samples with low Ni loading. The layer which is in contact with the Al2O3 surface is affected by the support surface and its structure is highly distorted, while the other layers were not distorted and have a structure similar to that in bulk NiO. In the reduced state, the number of Ni metal atoms in the reduced Ni particles was smaller than 100 with a narrow distribution below a loading of 15.6 wt% Ni. Above this loading, the particle size suddenly increased and the distribution became wider. The distances and Debye-Waller factors were similar to those of bulk nickel which suggested a weak interaction between the particles and the support. In the passivated state, Ni kernels with 20-40 metal atoms were covered by a one layer thick NiO ski
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ããã®æž©ç±è² è·ã«å¯Ÿããäœæž©èª¿ç¯åå¿ã¯ä¿é²ãããããšã瀺åããããThe present study was conducted to examine how daily exercise for several hours at a fixed time modifies the pattern of day-night variations in body core temperature and behavior in rats. Spontaneous wheel running was adopted as a model of exercise to avoid any artificial stress on rats.1. Male Wistar rats were acclimated to cages with a running wheels. Then, the running time of rats were limited to the first or last 3 or 6 h of the dark phase. After a 2-week activity restriction, the rats were again allowed access to the wheel freely. Wheel revolutions of rats during the period corresponding to the previous running time significantly increased after the activity restriction.2. Male Wistar rats were kept in cages with a running wheel and allowed access to the wheel for 6 h in the last half of the dark phase. After a 3-week exercise period, they were denied to run in the wheel. Their body core temperature significantly increased for 2-3 hours in the last half of the dark phase.The results suggest that, in rats, voluntary running limited to a fixed time daily alters the pattern of nycthemeral variations in body core temperature and locomotor activity, i.e., body core temperature and running activity increase during the period when the rats were previously allowed to exercise.ç 究課é¡/é åçªå·:05670064, ç 究æé(幎床):1993 â 1994åºå
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