Amiloride-insensitive Na+-H+ exchange: a candidate mediator of erythrocyte Na+-Li+ countertransport

Erythrocyte Na+-Li+ countertransport shows an increased activity in essential hypertension and diabetic nephropathy, but its nature remains unknown. This amiloride-insensitive membrane transport may not be a mode of operation of the amiloride-sensitive NHE1, the only Na+-H+ exchange isoform found in human erythrocytes. Whether an independent, although unknown, amiloride-insensitive isoform mediates Na+-Li+ countertransport is unclear. Na+-H+ exchange activity was measured in acid-loaded erythrocytes. Dimethylamiloride, a specific inhibitor of Na+-H+ exchange and phloretin, a known inhibitor of Na+-Li+ countertransport, gave a reduction in H+-driven Na+ influx (by 31 and 37%, respectively). This effect was additive, and a 66% reduction in H+-driven Na+ influx was found in the presence of both inhibitors. Internal acidification, a stimulus for Na+-H+ exchange, enhanced Na+-Li+ countertransport activity (from 287 +/- 55 to 1213 +/- 165 micromol x Lcell(-1) h(-1), mean +/- SEM, P = 0.003). This transport remained sensitive to phloretin under both conditions. Conversely, external acidification decreased Na+-Li+ countertransport activity (as expected for a Na+-H+ exchanger). Competition between internal H+ and Li+ or Na+ for a common binding site was present. Finally, similar kinetic parameters for external Na+ characterized Na+-Li+ countertransport and the phloretin-sensitive component of H+-driven Na+ influx. These findings suggest that both Na+-Li+ countertransport and the amiloride-insensitive, phloretin-sensitive component of H+-driven Na+ influx can be mediated by a previously unrecognized novel amiloride-insensitive Na+-H+ exchange isoform in human erythrocytes.     

Solubilities of Pb+2, Bi+3, Sb+3, and Cu+1 sulfides in (NaCl+KCl+Na2S) melts

Solubilities of common metal sulfides have been determined in the (NaCl+KCl) eutectic melt with and without Na₂S. A novel gas-phase equilibrium technique has been used for PbS, Bi₂S₃, and So₂S₃, and an improved liquid phase equilibrium technique for Cu₂S, which eliminates the errors due to physical entrapment of the sulfide phase and segregation on quenching, enabling precise measurements to be made. Solubilities in the (NaCl+KCl) eutectic melt were determined as a function of temperature in the rante 700° to 950°C, and were found to be small. The partial molar heats of mixing of the sulfides in the eutectic melt have been calculated from the solubility measurements, to be 13.3, 31.4, 37.1, and 49.0 kcal for PbSs), Sb₂S₂(l), and Cu₂S(s), respectively. Sodium sulfide addition was observed to enhance these solubilities, the effect being largest for Cu₂S followed by Sb₂S₃, Bi₂S₃, and PbS. This effect is explained qualitatively. It was observed that PbS and Sb₂S₃ obey Henry's law up to saturation in (NaCl+KCl+Na₂S) melts. O. P. MOHAPATRA, formerly Graduate Student, University of Toronto     

Combustion in Layered Ni + Al and Ti + Al + C Powdered Mixtures

Russian Journal of Non-Ferrous Metals - This study is devoted to the technology of producing cermet coatings using self-propagating high-temperature synthesis (SHS). The importance of the study is...     

用APACHE+PHP+MYSQL实现网站自动更新

在分析建立自动更新网站必要性的基础上,较详细地说明了如何利用APACHE+PHP+MYSQL工具实现网站自动更新中的权限控制、资料上传、自动更新,并给出了网页的部分源代码.     

"V+Num+是+Num"构式初探

汉语"V+Num+是+Num"构式具有特殊的句法特征,对于该构式的认知机制我们可以用舞台模型理论、空间映射理论作出解释.该构式的浮现意义是指最大限度(尽可能)地做某事,它表达了说话者积极进取而又无可奈何的复杂心态.     

Both Na+-K+ ATPase and Na +-H+ exchanger are immediately active upon post-ischemic reperfusion in isolated rat hearts

Lipases contained in commercial samples of lipase extracts from Rhizopus niveus (RNL) and Candida rugosa (CRL) have been selectively adsorbed on hydrophobic supports at very low ionic strength. Under these conditions, adsorption of other proteins (including some esterases) is almost negligible. More interestingly, these lipases could be separated in several active fractions as a function of a different rate or a different intensity of adsorption on supports activated with different hydrophobic groups (butyl-, phenyl- and octyl-agarose). Thus, although RNL seemed to be a homogeneous sample by SDS-PAGE, it could be separated, via sequential adsorption on the different supports, into three different fractions with very different thermal stability and substrate specificity. For example, one fraction hydrolyzed more rapidly ethyl acetate than ethyl butyrate, while another hydrolyzed the acetate ester 7-fold slower than the butyrate. Similar results were obtained with samples of CRL. Again, we could obtain three different fractions showing very different properties. For example, enantioselectivity for the hydrolysis of (R,S) 2-hydroxy-4-phenylbutanoic acid ethyl ester ranged from 1.2 to 12 for different CRL fractions. It seems that very slight structural differences may promote a quite different interfacial adsorption of lipases on hydrophobic supports as well as a quite different catalytic behavior. In this way, this new 'interfacial affinity chromatography' seems to be very suitable for an easy separation of such slightly different lipase forms.     

Ga3+ as a functional substitute for Fe3+: preparation and characterization of the Ga3+Fe2+ and Ga3+Zn2+ forms of bovine spleen purple acid phosphatase

A general method has been developed that allows the specific substitution of both iron atoms in the enzyme bovine spleen purple acid phosphatase (BSPAP), which possesses a dinuclear iron center at the active site. The approach is demonstrated by the preparation and characterization (atomic absorption spectrometry, enzyme kinetics, optical spectroscopy, and electron paramagnetic resonance spectroscopy) of two metal-substituted forms in which the ferric iron has been replaced by Ga3+: Ga3+Fe2+-BSPAP and Ga3+Zn2+-BSPAP. Both forms are colorless but exhibit enzymatic activity comparable to that of the native Fe3+Fe2+-BSPAP. Small but consistent changes in kinetics parameters and pH profiles were detected both upon substitution of Fe3+ by Ga3+ and upon substitution of Fe2+ by Zn2+. These results constitute the first evidence that the diamagnetic Ga3+ ion can serve as a functional analogue of Fe3+ in an enzyme, and suggest a novel approach for the study of the role of Fe3+ in other iron enzymes.     

A comparison research on replacements of Ba2+ by Lu3+ and Ba2+-Si4+ by Lu3+-Al3+ in BaSi2O2N2:Eu phosphors

As a cyan-emitting oxonitridosilicate phosphor,BaSi₂O₂N₂:Eu²⁺can be used as a competent cyan compensator to improve the color rendering index of white light-emitting diodes(WLEDs).However,low luminescence efficiency and poor thermal stability of this type of phosphor seriously suppress its actual application in full-spectrum lighting.The replacements of Ba²⁺by Lu³⁺and Ba²⁺-Si⁴⁺by Lu³⁺-Al³⁺can greatly increase the luminescence intensity and improve the thermal stability at the same time.With Lu³⁺doping,the internal quantum efficiencyηIQE Ba_0.925Si₂O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺is 24.08%higher than that of Ba_0.97Si₂O₂N₂:0.03 Eu²⁺.After Al³⁺co-doping,theηIQE is further increased by 10.31%compared to Ba_0.925Si₂O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺.When the temperature rises to 473 K,the luminescence intensity of Ba_0.925Si₂O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺maintains 62.32%of that at room temperature,which increases by 17.35%in relative to the Ba_0.97Si₂O₂N₂:0.03 Eu²⁺,while the luminescence intensity of Ba_0.925Si_1.97O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺,0.03 Al³⁺keeps 73.87%of the initial value,which increases by18.52%compared to Ba_0.925Si₂O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺.The mechanisms for luminescence and thermal stability improvement are proposed.The Ba_0.925Si_1.97O₂N₂:0.03 Eu²⁺,0.045 Lu³⁺,0.03 Al³⁺cyan phosphor,Y3 Al5 O12:Ce3+yellow phosphor and CaAlSiN3:Eu²⁺red phosphor are mixed thoroughly and coated on a blue LED(450 nm)to assemble a WLED.The WLED demonstrates a color rendering index(Ra)of 97.1 at150 mA,and the R1-R15 values are all above 90.The results indicate that as an effective cyan compensator in WLED,the BaSi₂O₂N₂:Eu²⁺,Lu³⁺,Al³⁺phosphor has great application prospect in the field of full-spectrum lighting.