Permeability of Squid Axon Membrane to Various Ions

The permeability of the squid axon membrane was determined by the use of radioisotopes of Na, K, Ca, Cs, and Br. Effluxes of these isotopes were measured mainly by the method of intracellular injection. Measurements of influxes were carried out under continuous intracellular perfusion with an isotonic solution of potassium sulfate. The Na permeability of the resting (excitable) axonal membrane was found to be roughly equal to the K permeability. The permeability to anion was far smaller than that to cations. It is emphasized that the axonal membrane has properties of a cation exchanger. The physicochemical nature of the "two stable states" of the excitable membrane is discussed on the basis of ion exchange isotherms.     

Somatostatin suppresses plasma aldosterone concentration in a case of Bartter's syndrome

The study was conducted to examine the effect of somatostatin on activated renin-angiotensin-aldosterone system in a case of Bartter's syndrome. After 60 minutes of 500 micrograms of somatostatin infusion, the plasma aldosterone concentration was reduced from the basal level of 250 pg/ml to 140 pg/ml, whereas plasma renin activity remained at the basal level. This result suggests that somatostatin may specifically inhibit aldosterone secretion in Bartter's syndrome and the agent can be applied to a treatment of this syndrome.     

Axonal microtubules necessary for generation of sodium current in squid giant axons: I. pharmacological study on sodium current and restoration of sodium current by microtubule proteins and 260K protein

Summary Effects of the reagents suppressing or supporting axoplasmic microtubule assembly were studied on the Na ionic current of squid giant axons by perfusing the axon internally with the solution containing the reagent. Among the reagents suppressing the assembly, colchicine, vinblastine, podophyllotoxin, sulfhydryl reagents such as DTNB and NEM, and chaotropic anions such as iodide and bromide, were examined. These reagents reduced maximum Na conductance and shifted the voltage dependence of steady-state Na activation in a depolarizing direction along the voltage axis. They also made the voltage dependence less steep, but did not affect sodium inactivation appreciably. Effects on Na ionic current of reagents which support microtubule assembly (Taxol, DMSO, D₂O and temperature) were opposite the effects of those agents suppressing assembly. At the same time, we demonstrated that after Na currents were partially reduced, they could be restored by internally perfusing the axon with a solution containing microtubule proteins, 260K proteins and cAMP under conditions favorable for microtubule assembly. For full restoration, it was found that the following conditions were necessary: (1) The microenvironment within the axon is suitable for microtubule assembly. (2) Tubulins incorporated into microtubules are fully tyrosinated at their C-termini. (3) A peripheral protein having a molecular weight of 260,000 daltons (260K protein) is indispensable. These results suggest that axoplasmic microtubules and 260K proteins in the structure underlying the axolemma play a role in generating Na currents in squid giant axons.     

Mechanical changes in squid giant axons associated with production of action potentials

The action potential of squid giant axons is accompanied by a quick and small swelling, about 0.5 nm in displacement of the surface, and about 1 dyne/cm² in pressure increase.     

Isolation and characterization of a thermophilic benzoate-degrading,sulfate-reducing bacterium,Desulfotomaculum thermobenzoicum sp. nov.

A new thermophilic sulfate-reducing bacterium, strain TSB, that was spore-forming, rod-shaped, slightly motile and gram-positive, was isolated from a butyrate-containing enrichment culture inoculated with sludge of a thermophilic methane fermentation reactor. This isolate could oxidize benzoate completely. Strain TSB also oxidized some fatty acids and alcohols. SO _inf4 ^sup2- , SO _inf3 ^sup2- , S₂O _inf3 ^sup2- and NO _inf3 ^sup- were utilized as electron acceptors. With pyruvate or lactate the isolate grew without an external electron acceptor and produced acetate. The optimum temperature for growth was 62°C. The G+C content of DNA was 52.8 mol%. This isolate is described as a new species, Desulfotomaculum thermobenzoicum.     

Axonal microtubules necessary for generation of sodium current in squid giant axons: I. Pharmacological study on sodium current and restoration of sodium current by microtubule proteins and 260K protein

Effects of the reagents suppressing or supporting axoplasmic microtubule assembly were studied on the Na ionic current of squid giant axons by perfusing the axon internally with the solution containing the reagent. Among the reagents suppressing the assembly, colchicine, vinblastine, podophyllotoxin, sulfhydryl reagents such as DTNB and NEM, and chaotropic anions such as iodide and bromide, were examined. These reagents reduced maximum Na conductance and shifted the voltage dependence of steady-state Na activation in a depolarizing direction along the voltage axis. They also made the voltage dependence less steep, but did not affect sodium inactivation appreciably. Effects on Na ionic current of reagents which support microtubule assembly (Taxol, DMSO, D2O and temperature) were opposite the effects of those agents suppressing assembly. At the same time, we demonstrated that after Na currents were partially reduced, they could be restored by internally perfusing the axon with a solution containing microtubule proteins, 260K proteins and cAMP under conditions favorable for microtubule assembly. For full restoration, it was found that the following conditions were necessary: (1) The microenvironment within the axon is suitable for microtubule assembly. (2) Tubulins incorporated into microtubules are fully tyrosinated at their C-termini. (3) A peripheral protein having a molecular weight of 260,000 daltons (260K protein) is indispensable. These results suggest that axoplasmic microtubules and 260K proteins in the structure underlying the axolemma play a role in generating Na currents in squid giant axons.     

Development of a psoriasis-like syndrome following lithium therapy

A correlation between lithium and psoriasis has been observed. In this paper, the case of a 17-yr-old girl is reported who developed psoriatic lesions after administration of lithium carbonate. Further-more, serum lithium levels in some psoriatic patients are disclosed, and induction of psoriasis by lithium in experimental animals is described. Serum lithium levels in 27 patients were significantly higher (p<0.025) than those of controls. Uninvolved parts of skin tissues obtained from three cases of psoriasis were transplanted to nude mice. After supplementing lithium as the chloride, these skin grafts developed the histologic change characteristic of psoriasis. However, the lithium compound by itself did not increase superoxide production of polymorphonuclear leukocytes in psoriasis.