Sohei Kondo

Thermodynamical Fundamental Equation for Spherical Interface

The relation between the radius of the Gibbs dividing surface and the superficial density is investigated in detail and the generalized Kelvin relation is obtained. Consequently the fundamental equation for spherical interface is expressed by dE=TdS+μdN−pαdVα−pβdVβ+γdA+(∂γ/∂a)Ada. The generalized Kelvin relation is the explicit differential equation for determining the location of the surface of tension which does not contradict with the conventional one. Thus the mathematical formalism of thermodynamics will be completed for treating spherical interface in a rigorous and self‐consistent manner, the last ambiguous point being eliminated from the conventional Gibbs treatments.

Radiation genetics in wheat, VIII. The RBE of heavy particles from B10 (n, α) Li7 reaction for cytogenetic effects in Einkorn wheat☆

The relative biological effectiveness (RBE) of alpha plus Li/sup 7/ recoil particles relative to gamma-rays has been studied for seedling height depression, chromosome aberrations, and chlorophyll mutations in Einkorn wheat. Irradiation with these heavy particles was administered by using the reaction of B/sup 10/ (n, alpha ) Li/sup 7/; wheat seeds, which had been previously soaked in aqueous solution at different borax concentrations (0 to 1.0 per cent), were exposed to thermal neutrons in a reactor. Subtracting the radiobiological effects of thermal neutrons for seeds soaked in pure water from those found for seeds soaked in borax solution, the net effects of the heavy particles were estimated and compared with the gamma-ray effects for seeds under the same soaking conditions as for neutron treatments. The RBE values obtained for chromosome aberrations in pollen mother cells and for chlorophyll mutations were 23 450 deg C in a 10 and 29 450 deg C in a 10, respectively. These figures are of the same order as those for fast neutrons previously reported for wheat and barley. Most of the present results are explicable on the assumption that chromosome breakage in wheat requires many ionizations to occur within a chromosome and that themorexa0» majority of radiation-induced chlorophyll mutations result not from point mutations but from chromosome breakage events. (auth)«xa0less

Synergistic Effects of P32 Decay and Ultraviolet Irradiation on Inactivation of Salmonella1 2

It is well known that bacteria (1), bacteriophages (2), yeast (3), and human cells (4) can lose their colonyor plaque-forming capacity by disintegration of radioactive phosphorus (P32) incorporated into their DNA molecules (reviewed by Stent and Fuerst, 5). The mechanism of those lethal effects remains unclear. The inactivation appears to be the consequence of the disintegration of a single atom of p32, but in organisms that have double-stranded DNA as their genetic material the efficiency of killing per disintegration is less than unity. In other words, P32 disintegration produces not only lethal damage but also nonlethal or latent damage in double-stranded DNA molecules. To elucidate the nature of these damages, we have examined the effects of p32 disintegration when combined with ultraviolet (UV) irradiation. Ultraviolet is more useful than ionizing radiation for this purpose because the mechanism of biological effects has recently been considerably elucidated at the molecular level (6-8). There is synergism between inactivation of colony-forming capacity of Salmonella by UV irradiation and by p32 decay; this synergism can be explained by interaction between pairs of different nonlethal chemical lesions in DNA, one of which is caused by UV and is photoreactivable, and the other caused by p32 disintegration. Experimental results and their analysis permit certain conclusions concerning the mechanism of the lethal action of p32 disintegration.

Comparative studies of mutation frequencies induced by 32P treatment and γ-irradiation in the male silkworm

Abstract The frequency of mutation induced in the male silkworm fed with 32 P on the third day of the fourth instar (shortly before meiosis) was compared with that induced by γ-irradiation. The daily dose of γ-rays was careflly adjusted day by day so as to fit the daily change in the absorbed dose delivered to the gonad by the ingested 32 P. The gonad dose for the 32 P treated group was estimated by applying Loevinger s equation; the parameters involved in the equation were experimentally determined with special care for biological factors. Using the 32 P dose estimates thus determined, we found that the mutation frequency was equal for the 32 P and γ-ray groups at the same absorbed dose. We conclude that there could be no chance for a mutation induced by 32 P transmutation to show up under the present conditions and that the proposed 32 P dosimetry is satisfactory.

A biophysical theory for radiation-induced polygenic mutations

SummaryGeneral equations have been derived for estimating polygenic mutation rate per locus per unit dose. It is argued that the present method for estimating polygenic mutation rate is on the same basis as the conventional method for obtaining major gene mutation rate. An example has been given in order to show how to use the equations for calculating polygenic mutation rate.A crude model has been proposed to account for the characteristics of radiation-induced polygenic mutations: (1) increase in quantitative variance of the polygenic character with increasing radiation dose, (2) more or less symmetrical distribution of the frequency of mutants with changed polygenic quantity about the mean, and (3) a high mutation rate per locus per unit dose.