[Ferruginous bodies in the lungs of the general population during a 45-year period and mineralogical examination]

In order to determine the level of asbestos pollution in the lungs of members of the general population in and around Tokyo, the incidence of ferruginous bodies in autopsied or resected lungs during 5 periods over the 45 years from 1937 to 1981 was studied by a light microscopy. Core fibres, after removal of their ferruginous coatings with oxalic acid, and uncoated fibres were analyzed using a scanning electron microscope equipped with a Kevex energy-dispersive X-ray spectrometer. The incidence of ferruginous bodies in 5 g (wet) of digested lung tissue was shown to be 10% in period I (1937-1941), 18% in period II (1947-1951), 70% in period III (1958-1963), 74.4% in period IV (1970-1973) and 81.0% in period V (1980-1981). The major types of core fibres of ferruginous bodies were found to be asbestos, including amosite, crocidolite, chrysotile and the tremolite-actiolite series, but a small number of fibers of materials other than asbestos were also detected. In contrast, a large number of short fibers less than 5 microns in length in 1 g of wet lung tissue were classified as belonging to Mg + Si fibers (the ratio of Mg to Si components being 30% or over) and presumed to be chrysotile. Thus an annual increase in asbestos deposition in lungs of people living in and around Tokyo has been demonstrated and fine chrysotile fibers less than 5 microns in length seem to be the main type of deposited fibers.

Effects of KCl, MgCl2, and CaCl2 concentrations on the monomer-polymer equilibrium of actin in the presence and absence of cytochalasin D

Critical metal concentrations of KCl, MgCl2, and CaCl2 below which actin cannot exist in filamentous form at equilibrium were estimated to be approximately 8 mM, 0.2 mM, and 0.4 mM, respectively, when actin, 0.5 mg/ml, was incubated for a long time at pH 8.0 and 25 degrees C. These values were obtained by viscosity, UV absorbance and pyrene-labeled actin fluorescence measurements. In the case of CaCl2, viscosity measurements resulted in a larger critical concentration, 0.7 mM. It turned out that actin filaments formed in a low concentration of CaCl2 were easily fragmented by shearing force. The higher the actin concentration, the lower the critical metal concentration was. The critical concentrations of actin above which actin can exist as a polymer at equilibrium became larger as the KCl, MgCl2, and CaCl2 concentrations were lower. It is advisable to add 0.05-0.1 mM CaCl2 to a depolymerization solution to obtain a concentrated monomeric solution. In the presence of cytochalasin D, which preferentially blocks the elongation at the barbed end of actin filaments, the critical concentrations of KCl and CaCl2 were the same as in its absence. On the other hand, the critical concentration of MgCl2 was increased and the extent of polymerization was decreased by cytochalasin D. In the presence of 50 mM KCl and 1 microM cytochalasin D, 0.01-0.1 mM MgCl2 markedly decreased the extent of polymerization of actin at equilibrium, where the critical actin concentration was tenfold increased. It is suggested that Mg2+ enhances dissociation of actin monomers at the pointed end of an actin filament.

Are amorphous aggregates of actin formed at the initial stage of polymerization?

Amorphous aggregates of actin of various sizes were observed under an electron microscope, when actin polymerization was inhibited or retarded by EDTA or by low salt concentration. It was first thought that these aggregates could be intermediate complexes of actin in the process of polymerization. These aggregates were, however, present in usual G-actin solution as well as column-chromatographed or highly clarified samples. In the samples prefixed with glutaraldehyde, the aggregates were also observed. Moreover, similar aggregates were seen in denatured actin samples. Hence it is concluded that these aggregates of actin are artefact products due to the treatment with uranyl acetate used for negative staining.

Effect of alteration of pheripheral blood flow on the central circulation in man during supine cycling in different ambient temperatures

Whether the alteration of peripheral circulation caused by changing ambient temperature (Ta) affects central circulatory changes in man during supine cycling was investigated in four well-trained men, who exercised at two levels (117.7 or 176.6 W). Exercise metabolic rate (VO2) in cold (0 degree C or 10 degrees C) was the same as it was at 20 degrees C, whereas the cardiac output (CO; CO2 rebreathing technique) and heart rate were significantly lower (e.g.,176.6 W at 0 degree C, both p < 0.01). In heat (30 degrees C or 40 degrees C), the VO2 reduced with falling CO and mean arterial blood pressure from those at 20 degrees C (e.g., 176.6 W at 40 degrees C, all cases p < 0.01), whereas the peak post-exercise calf blood (CBFp) increased (p < 0.01). The VO2 and stroke volume (SV) were inversely proportional to the ratio of CBFp to CO/kg body weight (CBFp/CO) (r > -0.78, p < 0.001). Total peripheral resistance (TPR) was related to arteriovenous oxygen difference (A-VO2 difference) (r > 0.78, p < 0.001). The TPR and A-VO2 difference decreased as Ta rose, while CBFp/CO was almost the same. As CBFp/CO had exceeded 50 and further progressed, however, the two parameters elevated until the same level as that at 0 degree C. The present results suggest that during moderately prolonged (16--60 min) supine cycling in different Ta's the central circulatory changes are mainly affected by the altered peripheral blood flow in competing between skin and muscle for blood flow.