Effect of X-537A on the phosphorylated protein in sarcoplasmic reticulum vesicles

Summary The effect of the antibiotic X-537A on the phosphorylated ATPase (EP) was investigated. The results show that X-537A depresses the level of EP which is dependent on the Ca²⁺ gradient, while the Ca²⁺-independent EP is not affected. Acknowledgments. This work was supported by grants from the Instituto de Alta Cultura of the Portuguese Ministry of Education (No. CB/2) and the Calouste Gulbenkian Foundation.     

Effect of 723-1723-1723-1on ethanol withdrawal in mice

Summary ⁹ (10 mg/kg, i.p.) administered to mice immediately after withdrawal from a 3-day exposure to ethanol vapor was found to intensify withdrawal reactions. No effect was seen when ⁹ was administered chronically during the exposure to ethanol.     

海南岛万泉河口沉积环境演变

根据对柱样沉积物²¹⁰Pb定年及有机碳、硫和有机碳同位素含量分析, 研究万泉河口沉积环境演变. 硫和δ¹³C均自19世纪初期开始持续减少, 硫从1.92%逐渐减少到0.36%, δ¹³C从−20.63‰减少到−23.64‰. C/S比在20世纪之前一直很稳定, 处于0.47~0.80之间, 有机碳与硫呈正相关; 在此之后, C/S比急剧增加, 至表层为3.94, 硫的含量与有机碳的增加没有相关关系. 结果表明在19世纪之前万泉河口尚为开阔的海湾, 处于正常海洋环境,未形成被沙坝围封的泻湖, 海水能够直接出入. 19世纪初期开始, 随着玉带滩沙坝向北发育, 河口逐渐被围拦成泻湖型, 进入的海水量逐渐减少; 在19与20世纪之交, 水体已开始明显淡化, 发展成为今天近乎淡水的泻湖.     

Differential effects of the serotonin receptors on cultured rat cerebral cortical neurons

Effects of serotonin (5-HT) on cerebral cortical neurons were examined by patch clamp techniques. 5-HT produced a variety of responses such as outward (19/73 patches/neurons), slow inward (15/73 patches/neurons), fast inward (8/73 patches/neurons), and mixed currents (initially fast inward deflection followed by an outward response: 2/73 patches/neurons), with a latency of 12 sec, 15 sec, 0 sec, and 0 sec respectively, at a holding potential of −60 mV in whole-cell patches. The fast inward currents were again evoked by a selective 5-HT3 receptor agonist, 1-(m-chlorophenyl)-biguanide hydrochloride (CPBG). In the cell-attached patch clamp configuration, 5-HT inside the patch pipette elicited single channel currents with slope conductances of 42 pS and 132 pS (4/42 patches/neurons). CPBG inside the patch pipette evoked inward single channel currents with a lower slope conductance of 41 pS (3/23 patches/neurons). In contrast, application of 5-HT or a 5-HT₂ receptor agonist, α-methyl-5-hydroxytryptamine-maleate, outside the patch pipette induced outward single channel currents with a major slope conductance of 140 pS (8/30 patches/neurons) or 135 pS (6/20 patches/neurons), respectively. These results indicate that the outward and fast inward currents may be mediated respectively by the 5-HT₂ receptor, which is coupled to a G-protein, and by the 5-HT₃ receptor, which contains the non-selective cation channel, and that the mixed type may be caused by both the 5-HT₂ and 5-HT₃ receptors. Received 27 September 1996; received after revision 4 November 1996; accepted 7 November 1996     

Effect of hydrogen peroxide on the binding of Merocyanine 540 to human erythrocytes

The fluorescent dye Merocyanine 540 (MC540) is often used as a probe to monitor the molecular packing of phospholipids in the outer leaflet of biomembranes. In a previous study we showed that the increased staining of erythrocytes with a perturbed membrane structure was mainly due to an increase in the fluorescence yield of cell-bound MC540, rather than to an increase of the number of bound molecules. Erythrocytes and ghosts exposed to continuous fluxes of H₂O₂ exhibited pronounced lipid peroxidation. Further, red blood cells subjected to this form of oxidative stress also showed increased staining with MC540. It appeared that this was caused by a strong increase in binding of MC540, together with a slight red shift of the fluorescence emission maximum and a small increase in the fluorescence yield of bound MC540. The changed MC540 binding characteristics were not observed when lipid peroxidation was suppressed by the presence of the antioxidant BHT in the incubation medium. However, open ghosts exposed to H₂O₂ showed no increase of MC540 binding, excluding a direct involvement of lipid peroxidation. Measurement of fluorescence emission spectra and gel filtration studies showed that MC540 can bind to H₂O₂-exposed hemoglobin. Experiments with erythrocytes lysed in hypotonic medium after exposure to H₂O₂ revealed that peroxidation of lipids with H₂O₂ induced a non-specific permeabilization of the plasma membrane to MC540, thereby allowing MC540 to bind to the oxidatively denatured, more hydrophobic hemoglobin. These results indicate that conclusions about packing of phospholipids in the outer leaflet of the membrane based on increased MC540-staining should be drawn with care. Received 27 September 1996; received after revision 5 November 1996; accepted 27 November 1996     

Spectrum characteristics and pump wavelengths of Nd3+-doped double-clad fiber

Conclusion The optimum wavelength of Nd³⁺-doped double-clad fiber laser or amplifier made in China is near 830 nm. The efficiency of Nd³⁺-doped double-clad fiber devices pumped by 820-nm laser is low due to ESA. In order to increase the photochemical stability of the outer cladding, the material of the outer cladding must be advanced.     

The prey consumption and prey preference of the larvae of the mosquitoCulex (Lutzia) raptor on the larvae ofCulex quinquefasciatus

The maximum consumption of the larvae of the pest and vector mosquitoCulex quinquefasciatus by the predatory mosquitoCulex (Lutzia) raptor was studied at various instars of both the predator and the prey. The prey preferences of the predator when given lavae of different instars were also investigated. The IVth instar of the predator consumed the maximum number of Ist instar and the maximum biomass of IVth instar larvae of the prey. Instars I and II of the predator preferred the Ist of the prey; instars III and IV of the predator preferred instars II and III of the prey respectively.The predator consumed an average of 157.1 larvae during its whole larval period, when each instar of the predator was given its preferred instar of the prey.     

蕴涵环交换性的某些多项恒等式

设ｍ＞１，ｎ，ｐ，ｑ，ｒ，ｓ均为正整数，Ｒ是一个具有单位元１的环．证明了：如果Ｒ中的任意ｘ，ｙ满足且Ｒ具有Ｑ（ｍ）性质，则Ｒ是一个交换环．此外，在适当的条件下确立了Ｒ的交换性．