Effect of Ethanol on the Sodium and Potassium Conductances of the Squid Axon Membrane

The effects of ethanol on squid giant axons were studied by means of the sucrose-gap technique. The membrane action potential height is moderately reduced and the duration sometimes shortened by ethanol in sea water. Voltage clamp experiments showed that ethanol in sea water reduced the maximum membrane conductances for sodium (g'_Na) and potassium (g'_K). In experiments with multiple application of ethyl alcohol to the same spot of membrane, a reduction of g'_Na to 82 per cent and of g'_K to 80 per cent of their value in sea water was brought about by 3 per cent ethanol (by volume) while 6 per cent caused a decrease of g'_Na to 59 per cent and of g'_K to 69 per cent. Ethanol has no significant effect on the steady-state inactivation of g_Na (as a function of conditioning membrane potential) or on such kinetic parameters as τ_h or the time course of turning on gi g_Na and g_K. It is concluded that ethanol mainly reduces g_Na and g_K in the Hodgkin-Huxley terminology.     

Further purification of a fibroblast growth factor-like factor from chick embryo extract by heparin-affinity chromatography

Summary A mitogenic factor which promotes quail myoblast proliferation has been purified some 10⁵-fold from chick embryo extract by a combination of cation-exchange chromatography and heparin-affinity chromatography. The factor is eluted from heparin-Sepharose with 2M NaCl and is a single-chain polypeptide with an apparent molecular weight of 15000 to 17000. It is active at subnanogram level in triggering the proliferation and thereby delaying temporarily fusion of myoblasts. It also stimulates the proliferation of quail fibroblasts in a similar effective concentration range. For both myoblasts and fibroblasts the dose-response to the factor is quantitatively and qualitatively comparable with that of bovine pituitary fibroblast growth factor. These observations strongly suggest that the factor very probably corresponds to chicken fibroblast growth factor or to a closely related molecule(s) and that it is possibly involved in the regulation of myogenesis. This work was partly supported by a grant from the National Center of Neurology and Psychiatry (NCNP grant 86-01) of the Ministry of Health and Welfare, Japan.     

Effect of a synthetic progestin on ventilatory response to hypoxia in anesthetized rats

Effects on ventilatory responses to progressive isocapnic hypoxia of a synthetic potent progestin, chlormadinone acetate (CMA), were determined in the halothane-anesthetized male rat. Ventilation during the breathing of hyperoxic gas was largely unaffected by treatment with CMA when carotid chemoreceptor afferents were kept intact. The sensitivity to hypoxia evaluated by hyperbolic regression analysis of the response curve did not differ between the control and CMA groups. The reduction of ventilation after bilateral section of the carotid sinus nerve (CSN) in hyperoxia was less severe in CMA-treated than in untreated animals. Furthermore, the CMA-treated rats showed a larger increase in ventilation during the hypoxia test and a lower PO2 break point for ventilatory depression. Inhibition of hypoxic ventilatory depression by CMA persisted even after the denervation of CSN. We conclude that exogenous progestin likely protects regulatory mechanism(s) for respiration against hypoxic depression through a stimulating action independent of carotid chemoreceptor afferents and without a change in the sensitivity of the ventilatory response to hypoxia.     

Production of saikosaponins by tissue culture of Bupleurum falcatum L.

The studies for production of saikosaponins by tissue culture of Bupleurum falcatum L. were carried out to produce saikosaponins with several kinds of media and plant hormones. Among the media and plant hormones studied, Gamborg's B-5 [23] medium containing 0.5 ppm kinetin (k) and 1.0 ppm 3-indolebutyric acid (IBA) was the most effective medium and hormone for production of saikosaponins. The highest content of saikosaponin-d in the dried cells was 0.26%, which was similar to a concentration of Bupleuri Radix.Abbreviations MS medium used by Murashige and Skoog [22] - G medium used by Gamborg (B 5) [23] - W medium used by White [24] - NN medium used by Nitsch and Nitsch [25] - k Kinetin - BAP 6-Benzylaminopurine - 2,4 D 2,4-Dichlorophenoxyacetic acid - NAA -Naphtylacetic acid - IBA 3-Indolebutyric acid - IAA 3-Indoleacetic acid - ssd saikosaponin-d - PM Production medium - dw Dry weight