Electronmicroscopic morphometry was performed on lung of 1, 3, 12 and21 months-old rats exposed to 0.1, 0.5, 3 and 10 ppm nitrogen dioxide (NO2) continuously for one month. The rats used in this experiment were all supplied at one time from one colony and kept uder a barrier system until exposure. Effects of aging on the responses of lungs to NO2 were studied by comparingthe dose-effect reaction patterns among the age groups. A trend of dose-dependent increase of arithmetic mean thickness of air-blood barrier was found in all age groups examined. The responses of lung to NO2 ex-posure showedage-related differences. Based on the morphometric index, the response declines from 1 to 12 months, but increases again in 21-months-old rats. The compartmental components of alveolar wall tissue such as type I epithelial cells, type II epithelial cells, interstitial cells, interstitial matrix and capillary en-dothelium appeared to have various degrees of response due to both age at onset of exposure and NO2 concentration, resulting in the appearance of varying stages in impairment or repair. Accordingly, the response of each compartmental com-ponent of lung to the concentrations of NO2 did not always exhibit a simple dose-dependent increase or decrease but sometimes indicated a multiphasic reaction pattern.
For detection of thioneins induced in cultured rabbit kidney cells after exposure to Cd++, the cytosol fraction of 35S-cysteine-labeled cells was carboxy-methylated and subjected to SDS-gel electrophoresis. By fluorography of the gel, labeled thioneins were specifically detected in the cytosol of Cd++-treated cells while not in untreted control cells. Relative amounts of the labeled thioneins can be estimated by this method, since densitometrical concentrations of the thionein bands on the fluorogram were proportional to the amounts of the proteins applied to the gel. Moreover, isometallothioneins could be separated by this procedure.
A method for quantitative analysis of free amino acids in rat brain was established. Rat midbrain was homogenized in HClO4 solution and the su-pernatant was applied to a high-performance liquid chromatograph attached to a fluorescence detector. Amino acids were separated in an ion exchange column prepared for amino acid analysis and were reacted with o-phthalaldehyde. Fluores-cence intensity was linear in a wide range of amounts of authentic amino acids (1.25-12.5 nmoles). Threonine, serine and glutamine were completely separated. Sixty minutes was required for the elution of nine amino acids, which were main components of free amino acids in rat midbrain. An 8-hr exposure of rats to 4000 ppm of toluene or hexane produced significant increase in glutamine con-tent of the midbrain.
The effects of melanogenesis-interrupting syhthetic detergents on the active sites of mushroom tyrosinase were investigated. Contrary to the generally accepted assumption, the catecholase activity was not irreversibly inactivated after the reaction on a large excess of p-tert-butylcatechol. The addition of catechol after the reaction on p-tert-butylcatechol reached a plateau led to further consumption of oxygen. The addition of p-cresol to the reaction system after the enzyme ceased to react on p-tert-butylcatechol also resulted in the oxidation of p-cresol. When catechol was the first substrate, however, further addition of a diphenol (such as p-tert-butylcatechol) or a monophenol (like p-cresol) after completion of the oxidation on catechol brought about no more oxygen uptake. Those two conflicting results could be explained by the assumption that the affinity of the oxidation product(s) of p-tert-butylcatechol to the active sites of cresolase and catecholase was much lower than that of the oxidation product(s) of catechol. In order to minimize occupational hazards (depigmentation), it is recommended that phenolic compounds and their oxidation products first be tested with regard to their degree of inhibition on tyrosinase before these chemicals are handled in factories.
Chrysotile inoculated intratracheally into normal and BCG immunised guinea pigs incited a macrophage response and reticulin fibrosis. The immunised animals showed a more rapid localisation of pulmonary lesions and disappearance of the chrysotile fibres leading to accelerated focal fibrosis. More rapid transport of chrysotile to the lymph nodes of immunised animals was also observed. These findings suggest that BCG vaccine can influence the development of pathological lesions of asbestosis in guinea pigs by inducing them earlier and more rapidly.
Pneumoconiosis among slate mine workers and pencil makers, has become a serious occupational hazard in Mandsaur, India. The dust samples were found to be hihgly hemolytic against human erythrocytes in vitro. The lytic property and the rate of dissolution of silica from the dust in body fluids indicated its potential toxicity.