Influences of three factors (duration, density and difficulty) of a mental task onthe stress responses were studied in young male subjects. Arithmetical calculationtasks were assigned to the subjects by using a signal indicator. "Addition-subtraction task" of 60 consecutive min was accompanied by significantchanges in diastolic pressure, and in the serum levels of water and proteins (bothalbumin and globulin). These variables underwent changes at 10 min from the begin-ning of the task and remained thereafter on the constant levels up to 60 min. A comparative experiment on four density grades of "addition-subtraction task"showed that higher density tasks caused marked rises in the serum levels of freefatty acids and proteins (both albumin and globulin). It was thus elucidated thatthe density of the task is a factor involved in the stress induction by the task. No appreciable changes were provoked in every variables by a simple task con-sisted of comparison of two figures, whereas marked changes were brought aboutin the serum levels of water and proteins (both albumin and globulin) by a task con-sisted of calculation of the difference in two figures at the same task density asthe former. Moreover, pulse rate, diastolic pressure, and the serum levels of free fattyacids, water and proteins were considerably changed by "addition-subtraction task".
Using a new signal indicator "addition-subtraction task" of four density grades(60, 70, 80 and 90% of the maximum capacity of each subject) was assigned to 10 young male subjects for 15 min. The task was composed of two sorts of "addition-subtraction tasks" different in difficulty, one was "additon-subtraction task" of one figure and the other was that of two figures. Both tasks gave almost similar effects at the density range from 70 to 90% of the maximum capacity on the control levels of three variables (diastolic blood pressure, the serum levels of proteins and water) which had been noticed as the useful stress indices for some mental tasks. There-fore, it was elucidated that the density is the real factor involved in stress induction irrespectively of the difficulty in such paced tasks. From the rise in the serum protein level it was, moreover, presumed that these tasks were able to induce a certain stress response in the subjects at least at the density of 70%. A psychological effect of errors on stress induction was examined in 10 subjects at "addition-subtraction task" of two figures. However, any significant differences did not occur in the variables between in the cases with and without sound-signals for errors. Flicker values were unresponsive even to "addition-subtraction task" of two figures at the maximum capacity.
A vibration level meter with weighting network corresponding to human vibra- tion sensation has recently been planned by the Acoustic Society of Japan to assess vibration pollution. However, weight, size and position of a sensing element of a vibration pickup of the vibration level meter have not been standardized. To determine optimum values for them, the contact resonance was examined on combinations of eleven mounting materials and seven vibration pickups on a vibration table of electro- dynamic type in vertical and horizontal directions. It was found that the vibration pickup which had weight of 300 g was desirable for vertical and horizontal vibrations under almost all mounting conditions except in the case of some special materials. The contact resonance frequency between the pickup and the mounting material was able to be elevated to a considerably high frequency for vertical vibration, but for horizontal vibration it was lowered until near half the value in vertical vibration. Therefore, vibration occurring in human environment is desirable to be measured by a VL range of the vibration level meter, in which the weighting circuit of the amplifier has the same frequency characteristics as those of human vibration sensation below 90 Hz and above it the cut-off frequency nature is -18 dB/oct. Vibration pickup of the vibration level meter was able to be calibrated without bolting on the vibration table below 90 dB (0 dB=10-3 cm/sec2).
In relation to induction of chromosome changes by cyclamates and cyclohexylamine, influence on cell renewal rate and inhibition of DNA synthesis of these chemicals were examined. Both sodium cyclamate and cyclohexylamine revealed to affect cell growth and to prolong S-phase of cell cycle in certain dose levels. The influence was stronger in case of cyclohexylamine treatment than sodium cyclamate in terms of dose-response relationship. The relationship between chromosome changes and mitotic inhibition is to be clarified by further investigations.