Unusual selection on the KIR3DL1/S1 natural killer cell receptor in Africans

Interactions of killer cell immunoglobulin-like receptors (KIRs) with major histocompatibility complex (MHC) class I ligands diversify natural killer cell responses to infection. By analyzing sequence variation in diverse human populations, we show that the KIR3DL1/S1 locus encodes two lineages of polymorphic inhibitory KIR3DL1 allotypes that recognize Bw4 epitopes of protein">HLA-A and HLA-B and one lineage of conserved activating KIR3DS1 allotypes, also implicated in Bw4 recognition. Balancing selection has maintained these three lineages for over 3 million years. Variation was selected at D1 and D2 domain residues that contact HLA class I and at two sites on D0, the domain that enhances the binding of KIR3D to HLA class I. HLA-B variants that gained Bw4 through interallelic microconversion are also products of selection. A worldwide comparison uncovers unusual KIR3DL1/S1 evolution in modern sub-Saharan Africans. Balancing selection is weak and confined to D0, KIR3DS1 is rare and KIR3DL1 allotypes with similar binding sites predominate. Natural killer cells express the dominant KIR3DL1 at a high frequency and with high surface density, providing strong responses to cells perturbed in Bw4 expression.     

Anti-adipogenic effects of extracts of Ficus deitoidea var. deltoidea and var. angustifolia on 3T3-L1 adipocytes

Objective： This study examined the anti-adipogenic effects of extracts of Ficus deltoidea var. deltoidia and var. angustifolia, a natural slimming aid, on 3T3-L1 adipocytes. Methods： Methanol and water extracts of leaves of the F. deltoidea varieties were analyzed to determine their total flavonoid content （TFC） and total phenolic content （TPC）, respectively. The study was initiated by determining the maximum non-toxic dose （MNTD） of the methanol and water extracts for 3T3-L1 preadipocytes. Possible anti-adipogenic effects were then examined by treating 2-d post confluent 3T3-L1 preadipocytes with either methanol extract or water extract at MNTD and half MNTD （1/2MNTD）, after which the preadipocytces were induced to form mature adipocytes. Visualisation and quantification of lipid content in mature adipocytes were carried out through oil red O staining and measurement of optical density （OD） at 520 nm, respec- tively. Results： The TFCs of the methanol extracts were 1.36 and 1.97 g quercetin equivalents （QE）/100 g dry weight （DW）, while the TPCs of the water extracts were 5.61 and 2.73 g gallic acid equivalents （GAE）/100 g DW for var. deltoidea and var. angustilofia, respectively. The MNTDs determined for methanol and water extracts were （300.0±28.3） and （225.0±21.2） μg/ml, respectively, for var. deltoidea, while much lower MNTDs [（60.0±2.0） IJg/ml for methanol extracts and （8.0＋1.0） μg/ml for water extracts] were recorded for var. angustifolia. Studies revealed that the methanol extracts of both varieties and the water extracts of var. angustifolia at either MNTD or 1/2MNTD significantly inhibited the maturation of preadipocytes. Conclusions： The inhibition of the formation of mature adipocytes indicated that leaf extracts of F. deltoidea could have potential anti-obesity effects.     

Effect of sinter layer porosity distribution on flow and temperature fields in a sinter cooler

When sinters are filled into the sinter cooler from the sintering machine, it is commonly seen that, due to segregation effects, sinters of larger size usually accumulate closer to the inner wall of the sinter cooler, whereas those of smaller size are to the outer wall. This nonuniform distribution of sinters has led to uneven cooling effect throughout the cooler. This causes the sinters leaving the cooler at a large temperature difference. This undesired temperature difference leads to the deformation and even the destruction of the conveyors. The computational fluid dynamics (CFD) technique was used in the present work to investigate the heat and fluid flow phenomena within the sinter cooler corresponding to the different distribution of sinter layer porosity, which was highly dependent on the arrangement and orientation of sinters within the sinter cooler. It is confirmed that a high mass flow rate within the sinter layer causes a low temperature region and vice versa. The flow fields for vertically reducing porosity distribution and random distribution are almost identical indicating the relative insignificance of convective heat transfer mechanism.