Effect of Temperature on the Potential and Current Thresholds of Axon Membrane

The effect of temperature on the potential and current thresholds of the squid giant axon membrane was measured with gross external electrodes. A central segment of the axon, 0.8 mm long and in sea water, was isolated by flowing low conductance, isoosmotic sucrose solution on each side; both ends were depolarized in isoosmotic KCl. Measured biphasic square wave currents at five cycles per second were applied between one end of the nerve and the membrane of the central segment. The membrane potential was recorded between the central sea water and the other depolarized end. The recorded potentials are developed only across the membrane impedance. Threshold current values ranged from 3.2 µa at 267deg;C to 1 µa at 7.5°C. Threshold potential values ranged from 50 mv at 26°C to 6 mv at 7.5°C. The mean Q₁₀ of threshold current was 2.3 (SD = 0.2), while the Q₁₀ for threshold potentials was 2.0 (SD = 0.1).     

胎盘型碱性磷酸酶的纯化及部分性质的研究

 <正> 胎盘型碱性磷酸酶(P-ALP)是碱性磷酸酶(EC3.1.3.1.ALP)的一种同工酶。P-ALP除出现于妊娠妇女血清外,一些学者还从恶性肿瘤患者血清中发现此酶,并证明它是一种特异性较强的肿瘤标志物。据此,建立P-ALP的简易纯化方法,制备纯度较高的酶制品是建立P-ALP灵敏的微量检测法的先决条件。本文报道以L-苯丙氨酸(L-phe)为配基,用氯代环氧丙烷活化Sepharose 4B的亲和层析法,从人胎盘纯化P-ALP,并对其部分性质进行了研究。