Nitric oxide generation in aqueous solutions of cigarette smoke and approaches to its origin.

By using the ESR spin trapping technique with the N-methyl-D-glucamine dithiocarbamate (MGD)2-Fe(II) complex, the generation of nitric oxide (NO), a gaseous free radical, was observed in NO spin trapping solution bubbled with the filtered main-stream of cigarette smoke. The ESR signal with a three-line spectrum characteristic of an NO radical, which was not observed immediately after bubbling of smoke, started rapidly increasing with time up to around 25 min after the last addition of ferrous ions Fe(II), and then slowly approached a peak value dependent on the burned cigarette mass and on the smoking speed. The production of NO was, however, much affected by air oxidation and enhanced by the addition of ascorbic acid. A certain concentration of sodium nitrite (NaNO2) solution, in which nitrite NO2- is assumed as the main origin of the NO, mimicked closely the time course of NO generation resulting from the smoke of one cigarette. The cigarette smoke that was passed through alkaline pyrogallol solution as a deoxidizer; however, it exhibited an unchanged intensity of NO signal throughout the measurement. These results strongly suggest that NO would be gradually reproduced from NO2- in the reductive aqueous solution containing excess Fe(II) through NO2, which is initially formed and is concomitantly oxidized from NO in cigarette smoke.

Spin trapping of nitric oxide in aqueous solutions of cigarette smoke.

Nitric oxide, a gaseous free NO radical (.NO) generated in particulate-free gas-phase main-stream smoke of cigarettes, was observed with electrical spin resonance (ESR) using a spin trapping technique. N-Methyl-D-glucamine-dithiocarbamate (MGD)2-Fe2+ complex was used for the NO radical spin trapper in aqueous solution. The intensity of the ESR signal of the spin adduct formed by bubbling smoke from one cigarette increased gradually with time over 2 hours at about 20 degrees C and was constant for 2 days or longer. The time course of the production of the NO radical followed the rate equation y = 1520(1-e-0.018t) for the first-order reaction up to around 25 min after mixing of Fe2+ solution and then slowly approached the maximum value determined by the concentration of the spin adduct. These findings suggest that NO radical is produced slowly from NO radical donors such as amine .NO complexes, peroxinitrite (ONOO-), and other reactants such as nitrogen oxides (NOx), which are produced from the smoke of tobacco leaves, and suggest that its generation could be involved in the decomposition or cleavage of such substances.

Chemical model of reaction cascades induced by activated enzymes or catalysts. Two-step cascades in visual transduction.

A dissipative system is approximated by a nonlinear rate equation: Z congruent to K1Z - K2Z3 (K2 greater than 0), in which the right side is derived from -delta G/delta Z of Taylor's series of the thermodynamic potential given by Gibbs' function G(Tc, Pc) (Z) at about the critical point C(Tc, Pc) of the control variables (parameters) T and P. The stability or instability of the system is treated by the changes in the control parameters. In the case that T not equal to P not equal to 0 in the steady state, Z = 0, and T and P pass the point C, K1 becomes negative. By this change, the G function is convex at Z = 0 and each product is created rapidly with concentration or number of the molecules Z = ([K1]/K2)1/2. This dynamic theory is applied to enzyme cascades. Based on cyclic GMP (cGMP) hypothesis in visual transduction, the cascade hydrolysis of cGMP of vertebrates is analyzed by dividing it into two-step reaction cascades: The initial process is that metarhodopsin II catalyzes the exchange of GDP for GTP by transducin (Gtd) and that GTP-Gtd complex is hydrolyzed to GDP-Gtd complex. In the following cascade cGMP is hydrolyzed with amplification of phosphodiesterase (PDE) activated by the removal of the small inhibitory subunit. The quantity of the hydrolysis of cGMP is estimated as approximately 5 x 10(4-5) molecules per photolyzed rhodopsin semiempirically, and this coincides well with experiments.

Effects of styrene on wheel-running and ambulatory activities in mice.

Effects of styrene on wheel-running and ambulatory activities were investigated in mice. Sixty male mice (ICR strain) were divided into 10 groups of six mice each, and they were exposed to styrene of about 930, 425, 60, 25 or 0 ppm (control group) for 4 hours a day, 5 days a week over 2 weeks. The wheel-running and ambulatory activity tests were conducted during 2 weeks of the styrene exposure, and 1 week before and after the exposure. The wheel-running activity decreased at the high concentrations (930 and 425 ppm), and the decreased activity did not recover to the control level after cessation of the exposure. In the ambulatory activity test, styrene exposure resulted in the decrease in the activity, though the change was not concentration-dependent. The present results suggest that the behavioral effect of styrene is clearly detectable by means of wheel-running and ambulatory activities in mice.

A self-organized chemical model and reaction cascade.

Some reaction cascades in biological systems are analyzed by a self-organized chemical model, an autocatalytic reaction. This model is described by the coupling of a primary system which stabilizes the initial stage of the reaction rapidly and a partial system which controls the primary system slowly. By the internal force caused by a trigger above the threshold, the coupled system in near-equilibrium is broken and changed into a new state. From the rate equation for the coupled system, a dimensionless nonlinear state equation, n = -n3 - un - v, is derived, where n is the concentration of intermediate, and u, v are dynamic variables of the system. This equation is similar to a nonequilibrium tri-molecular reaction. By using this chemical network theory, fibrin polymerization. F + F----fm----fp + X, where F is a fibrinogen molecule, fm is a fibrin monomer, fp is fibrin polymer, and X is small peptides released from fibrinogen, is discussed as an excellent example of the enzyme reaction cascade.

Network formation in negative charged membranes by two divalent cations and the catastrophe.

The ligands of Ca2+-Cu2+-phosphatidylserine (PS) complexes in membrane networks at the water-oil interface through the symmetry breaking instability and the head groups of PS molecules were changed into a solid-like state. A first step in this transition is described by the following scheme in one unit in which the molar ratio is Ca2+: Cu2+: PS = 1:2:4; [Oh]+2[Oh]*----3[Oh]*, where [Oh]* denotes a little distorted ligand structure [LnM2+...2H2O] from [LnM2+2H2O], where Ln is PS molecules (n = 2 to Cu2+ and 4 to Ca2+). All the ligands are changed to [D4h] by the unit-unit interaction due to the network formation; [Oh]*----[D4h]. The whole system is equivalent to Schlögl's scheme and is given by a cubic state equation for suitable variables transformations: x = -x3 - ux - v, where x corresponds to the concentration of [Oh]*, and u and v are related to rate constants in the first and the second steps, and they also depend on the initial [Oh] and the final [D4h] concentrations. This system is transferred into a new state with a cusp catastrophe.

Chemical dynamic approach to synergetics and instability in biological systems.

Based on Haken's theory, self-organization or synergetics is discussed using chemical dynamics to represent an autocatalytic reaction. In a simple case the changes in a self-organizing system are given by a set of two rate equations for a primary and a partial system. When these systems mutually form a feedback loop under the adiabatic condition, the rate equation of self-organization is described by a generalized Gibbs' free energy change delta U (delta x) followed by the reaction. The sign of the parameter k'3 (k0-kex; k0, kex: rate constants with or without an external stimulus) determines the instability of the coupled system in quasi-equilibrium (k'3 approximately greater than 0; k0 greater than kex). When the product exceeds the threshold (k'3 less than 0; k0 less than kex), the system transfers into a new state, or a phase transition appears. Considering the Boltzmann distribution, the transition parameter k'3 is evaluated by an average distribution of the states and the instability is discussed using the reaction velocities vqe and vqe in the quasi-equilibrium state. As an example of this model membrane excitation is discussed briefly.

Dynamic approach to thermotropic and inotropic phase transitions.

Thermotropic and inotropic phase transitions have been analysed with a dynamic theory on a self-organization. An equation of motion of a molecular assembly with strong interactions may be approximately described as: dQ/dt' congruent to -K1Q-K3Q3, where Q is a displacement from the equilibrium point Q0(identical to 0) in a vibrational state, K1 is a transition parameter. When the parameter K1 concerned with an internal driving force (partial system) changes from positive to negative through the potential bifurcation, the system transfers to a new stable state breaking down the symmetry. Such a sign change of K1 serves as a trigger to a phase transition. Using Weiss' approximation, we have evaluated the change of K1 by a function of temperature, kappa (T-TC), and have obtained the critical temperature TC of thermotropic phase transition. We have furthermore treated inotropic phase transition caused by the binding of divalent cations like Ca2+ using the function kappa (T-beta TC), where beta is a shift parameter of the critical temperature.

Effects of X-ray irradiation on hearing in guinea pigs.

Effects of X-ray irradiation on the hearing with CM and ABR to both air- and bone-conduction stimuli were studied continuously from immediately after the irradiation to a few weeks later. At 2, 4, and 6 krad, only slight conductive hearing impairment was found, but at 8 krad or more, CM and ABR disappeared abruptly, after having increased briefly. Advanced sensorineural hearing loss appeared at about 10 hours after irradiation ended at 8 krad, at about 6 hours at 10 krad, and at about 3 hours at 12 krad. More severe hearing impairment was observed at higher frequencies and the endocochlear d.c. potential (EP) decreased at about 7 hours after 10 krad irradiation. Histologically, no discernible changes in the hair cells or sensory hairs were found with a scanning electron microscope at about 6 hours after 10 krad irradiation, while with a transmission electron microscope, the outer hair cells in the basal coil of the cochlea were found to be mostly destroyed. However, no changes could be found in the inner hair cells or other supporting cells.

Effects of kanamycin on the auditory evoked responses during postnatal development of the hearing of the rat.

The ototoxic effects of kanamycin were studied in rats during the early postnatal period and at an adult age. Brain stem potentials as well as auditory cortical potentials were used for the estimating of ototoxic damage. The auditory potentials decreased promptly and markedly in the animals which were treated daily with 400 mg/kg body weight of kanamycin starting from the 11th day after birth. In these animals, the auditory potentials were almost completely abolished within 10 days after the beginning of the kanamycin treatment. However, when the same amount of kanamycin was applied earlier or later than that, i.e., avoiding the period of the initial appearance and the greatest development of auditory functions (from the 11th to the 15th day after birth in the rat), the auditory potentials were not apparently damaged. In light and scanning electronmicroscopy, marked ototoxic changes were observed which underlay the functional damage. The meaning of these findings is discussed.