Mutagenicities of styrene oxide derivatives on Salmonella typhimurium (TA 100): relationship between mutagenic potencies and chemical reactivity

The lethal and mutagenic effects of p-methyl-, m-chloro-, p-chloro- and unsubstituted styrene oxide on Salmonella typhimurium (TA 100) were investigated. At equal concentrations, p-chlorostyrene oxide was more lethal than p-methyl-, m-chloro- or unsubstituted styrene oxide. When the survival fraction was 0.8 or more, the mutagenicities of these compounds increased in the order: m-chlorostyrene oxide = p-chlorostyrene oxide less than styrene oxide less than p-methyl-styrene oxide. The mutagenicities of these compounds depended only on the reactivity of their benzylic site; the reactivity at their primary site and their partition coefficients appeared to have no effect.

Inhibitory effect of tiaramide on ADP-induced aggregation in rabbit platelets

Tiaramide in 10(-4) or 10(-5) M depressed the ADP-induced aggregation of rabbit platelets using the turbidimetric method. In modified Chandler's loop method, tiaramide in the same concentration accelerated the restoration of the time course of disaggregation.

Werner's syndrome: analysis of 15 cases with a review of the Japanese literature

Fifteen patients with Werner's syndrome were studied--12 males and 3 females, whose ages ranged from 17 to 59 years. Most of the previously reported clinical characteristics were confirmed, and an additional finding was the frequent occurrence of flat feet and hyperreflexia of the patellar and Achilles tendons. Also noted were an excessive urinary excretion of hyaluronic acid and a decrease in the T-cell subpopulation. The significance of these findings is discussed.

Dose-rate effects of ethyl methanesulfonate on survival and mutation induction in cultured Chinese hamster cells

The dose-rate effects of ethyl methanesulfonate (EMS) on the survival and induction of mutations in Chinese hamster Don cells were investigated. The most effective time of exposure to EMS for reducing the surviving fraction of cells was 4 h, shorter and longer exposure times being less effective. The threshold or minimal concentration of EMS giving a surviving fraction of 0.5 was 0.05 mg/ml. The minimal effective time of exposure to EMS for cell death was 1 h. Corrected survival curves showed that longer exposure times at lower dose rates of EMS had less cytotoxic effect than shorter exposure times at higher dose rates. After exposure of Don cells to various doses of EMS for various times, the frequencies of mutations resistant to 6--thioguanine (6TG) were measured. An exposure time of 4 h produced a lower mutation frequency than shorter or longer exposure times that resulted in the same surviving fraction of cells. An exposure time of 20 h produced the highest induced mutation frequency. This system using cultured Chinese hamster cells should be useful as a sensitive procedure for detecting the mutagenic actions of chemicals.

Urinary excretion of macromolecular acidic glycosaminoglycans in Werner's syndrome

The urinary acidic glycosaminoglycans (AGAG) of Werner's syndrome were isolated, purified and characterized by gel-chromatography, cellulose acetate electrophoresis, chemical analysis, streptomyces hyaluronidase susceptibility and viscometry. The AGAG appeared at the first peaks of the 0.6 M and 0.8 M fractions obtained through Sephadex G-100 were mainly a a hyaluronic acid (HA). HA was composed of 16% of the urinary AGAG. The AGAG at the first peak had the maximum molecular weight of 360 000 in the 0.8 M fraction followed by lesser molecular weights in the other fractions.

[Effect of clonidine on plasma insulin level in mice (author's transl)]

The influence of adrenergic agents, epinephrine and clonidine, on plasma immunoreactive insulin and plasma glucose concentrations was studied in mice. Subcutaneous injection of epinephrine in fasted mice did not alter the plasma glucose concentration (PG), while plasma immunoreactive insulin concentration (IRI) tended to increase gradually. Intravenous injection of glucose markedly increased IRI. Glucose-induced IRI increase was inhibited by a subcutaneous injection of epinephrine in spite of high elevation of PG. This inhibition of glucose-induced IRI increase by epinephrine was reversed after treatment with an alpha-adrenergic blocking agent, phentolamine. Propranolol, an beta-adrenergic blocking agent suppressed IRI to a greater extent as compared with IRI induced by simultaneous injection of glucose and epinephrine. These results indicate that beta-adrenoceptor stimulating action accelerates the insulin release induced by glucose while alpha-adrenoceptor stimulating action inhibits it. Subcutaneous injection of clonidine in fasted mice slightly decreased IRI and increased PG. The response of PG to clonidine was dose-dependent. Glucose-induced IRI increase was inhibited by an intravenous injection of clonidine, and PG was elevated under the same conditions. The inhibition of glucose-induced IRI increase by clonidine was reversed when phentolamine was given, and under these conditions, PG showed no change. Propranolol treatment did not result in a recovery of the inhibition of glucose-induced IRI increase by clonidine. When compared with the results of epinephrine treatment, it may be concluded that clonidine shows alpha-adrenoceptor stimulating action in the secretion of insulin from beta-cells of the endocrine pancreas.

Motility of rat ascites hepatoma cells, with reference to malignant characteristics in cancer metastasis

The motility of four strains of rat ascites tumor cells in an agar medium was studied quantitatively by means of time lapse cinematography. The motility of these cells differed characteristically with each strain. Yoshida sarcoma and AH-66F cells showed active locomotion and partial movement markedly, while AH-130 and AH-100B cells made no locomotion and only a slight movement.

Binding of dextran sulfate by virus-transformed cells, with reference to altered growth behavior by its treatment

Binding of 3H-labeled dextran sulfate on transformed and untransformed cells was studied in relation to the altered growth of transformed cells by this treatment. 3T3 and SV3T3 cells, and the isolated cells (SV3T3-R5) insensitive to dextran sulfate treatment were used. The rate of binding of 3H-dextran sulfate on SV3T3 cells was dose-dependent when examined by the liquid scintillation method. It was revealed in autoradiographic analysis that there was no difference in the binding capacity of 3H-dextran sulfate among 3T3, SV3T3, and SV3T3-R5 cells. The rate of binding proceeded linearly during the first 10 hr and then tended to decline. Thin sections (0.3 approximately 0.5 micron) of SV3T3 cells were autoradiographed to examine the site of localization of 3H-dextran sulfate. Depending on the incubation time with the cells, 3H-dextran sulfate was located first on the cell surface and then in the cytoplasm when incubated further. Finally, silver grains were detected even in the nucleus of SV3T3 cells. This process of localization was similar in 3T3 cells. Binding of 3H-dextran sulfate on SV3T3 cells was independent of the presence of calf serum in the medium.

Nature of catecholamine-like actions of ATP and other energy rich nucleotides on the bullfrog atrial muscle

The nature of the inotropic actions of exogeneously applied ATP and related compounds (AMP-PNP, GTP, GMP and guanosine) was studied in comparison with that of adrenaline on the bullfrog atrial muscle under voltage clamped and unclamped conditions with the double-gap method. ATP and GTP (10(-6-) - 10(-3) M) produced an immediate positive inotropic effect similar to that achieved with adrenaline. Dose-response curves of these drugs fitted the theoretical dose-response relations, but the curves of ATP and GTP were not significantly altered by propranolol. Under voltage clamped conditions, ATP, AMP-PNP (non-hydrolyzable analogue of ATP) and GTP augmentated the calcium inward current (ICa), ICa-dependent tension and the delayed outward current (Ix) as adrenaline. On the other hand, GMP and guanosine, which have a purine-ribose base but not a high energy phosphate bond, produced a negative inotropic effect, and depressed the Ix as adenosine. All these nucleotides and nucleosides inhibited the ICa-independent tonic tension. The facts that GTP and AMP-PNP showed the same effect as ATP indicated that neither the energy liberation from the phosphate bond nor the substrate for cyclic AMP formation is involved in their positive inotropic effects. It is proposed that the energy rich nucleotides modulate the adenylate cyclase activity, being mediated by some receptor located at the outer surface of the membrane other than beta-adrenergic receptor.

Stabilizing effects of adenosine on the membrane currents and tension components of the bullfrog atrium

The effects of exogenously applied adenosine on the membrane potentials, currents and tension components of the bullfrog double sucrose-gap method. Adenosine above 10(-3)M produced a prolongation of action potential accompanied by a slight augmentation of contraction which was followed by a sustained depression. The recovery was slow. Under voltage clamp conditions, adenosine merely produced a negative inotropic effect depressing Ica-dependent and -independent tensions. In the membrane currents, Inaf, Is(Ica), Ix and background current (Ib) were all depressed. In the presence of adrenaline, the increased Is, Ix and contraction were inhibited by adenosine in a lower dose (10(-5) -10 (-3) M), and the inhibition of Is and Ica-dependent tension were more prominent in the presence of than in the absence of adrenaline. Under the effect of ATP, which has a catecholamine-like action, similar selective inhibitions were observed. It was concluded that adenosine has a sustained stabilizing action on the myocardium to survive, especially in the presence of adrenaline, by depressing the augmented Ica and contraction.

Effect of low temperature on the membrane currents and tension components of bullfrog atrial muscle

In order to clarify the nature of inotropic action of low temperature, the effects of cooling on the membrane currents and tension components were studied on the bullfrog atrial muscle under voltage clamped and unclamped conditions with double gap method. Cooling (in between 35 degrees-7 degrees C) produced an increase of overshoot and a prolongation of the action potential accompanied by a slight depolarization of the membrane, a decrease of basal tension and an increase of twitch contraction. Under voltage clamp, a marked augmentation of contraction also occurred despite a decrease of basal tension, suggesting that the inotropic effect of cooling is not merely dependent on the prolongation of action potential. When the components of membrane current and tension were isolated in modified Ringer solutions, it became clear that ICa and ICa -dependent tension markedly increased at low temperature, while all other currents (INaf, INas, IK1 Ix) and ICa-independent tension decreased. Leaky membrane current (I1) for hyperpolarizing pulses also diminished. Temperature coefficient (Q10) of the ICa-independent tension component was 1.2-1.5 between 7 degrees C and 17 degrees C, while that of ICa-dependent tension varied depending on depolarization voltages. These data were discussed in relation to possible alteration of Ca concentration at outer and inner layers of the membrane which may depend on temperature.