In 1983, 285 (male: 129, female: 156) VDT workers and 60 (male: 30, female: 30) control subjects were examined in order to detect the factors affecting the subjective symptoms of VDT workers. Biological information (for example: sex, age), life histories, information about VDT work, tests (for example: visual acuity), symptoms and interferences to daily life of VDT workers and control subjects were collected. The following results were obtained.
1. Female VDT workers experienced more fatigue from commuting to work, stiffness in shoulders, distant blurred vision complaints of visual acuity and sum of the scores of ocular complaints than female control subjects.
2. Only among female VDT workers, the longer the daily working hours, the greater were their ocular symptoms.
3. A remarkable relationships were observed between psychological burden factors (for example: self-control of VDT work, sensation of excessive VDT work) and subjective symptoms of the VDT workers (both sexes). In particular, VDT workers who considered VDT work to be excessive had marked by greater subjective symptoms than those who did not.

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Study were made on the effects of polarity of screen and color of display on work load of VDT tasks.
The subjects of the present experiment were eight healthy male college students (age: 21-23 yr) having a naked binocular vision of not less than 0.7 and no astigmatism nor hyperopia.
The test consisted of an experimental word processing task in which the subjects visually searched e's in given sequences of alphabetical letters displayed on the CRT and converted them to 5's through keyboard operation.
As for experimental conditions, four levels of screen image, that is, positive and negative screens and green and white colored displays were adopted and 2 hr were given for each operation time.
Critical flicker fusion (CFF), near point distance, accommodation time, subjective fatigue symptoms, heart rate, electromyogram in upper limbs and performance score were measured. The following results were obtained.
1) Decrease in C. F. F. and extension of near point distance were observed in all experimental conditions during the operating time.
2) Increase in complaints of subjective fatigue related to visual function was observed in all experimental conditions after two hour VDT task.
3) Greater extension of near point distance and larger complaints of subjective fatigue were observed in subjects using the green colored display than in those using the white colored display. This suggests that the the visual load using the green colored display is larger than that using the white colored display.
4) A larger decraesed in C. F. F. and greater complaints of subjective fatigue were demonstrated in subjects using negative screen than those using positive screen. This suggests that the visual load using the negative screen is larger than that using the positive screen.

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Effects of administration of lead acetate on Sidman avoidance behavior were assessed in juvenile and adult rats which were obtained by continued selective breeding and which have a high level avoidance ability and small individual differences (THA rat: Tokai high avoider rat). THA rats were administered lead acetate solution at 200-300 mg/kg/day as Pb until 7 wk of age through maternal milk before weaning from mothers which had been administered lead acetate from the 13th day of gestation and per os by gastric tube after weaning.
Three series of Sidman avoidance behavior tests were conducted from 49th, 100th and 150th day after birth each for 10 d, 1 h every day. In the first series, a significant delay of shock avoidance acquisition was observed in lead-administered male rats compared with the control subjects, while no acquisition delay was seen in female rats.
The lead administered male rats could be divided into two groups with different response patterns; a low susceptible group (LSG) which exhibited as good acquisition rate from the beginning similar to the control rats and a high susceptible group (HSG) which showed a significant delay and individual differences.
In the 2nd test series, very high avoidance rates were obtained in all the test groups except in male HSG, but in the 3rd test series, male HSG also attained a final acquisition of high avoidance rate.
There was no developmental variation between the groups nor difference in lead contents of the organs of the exposed group. Useful characteristics of THA rats for behavioral toxicology are discussed.

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A primary hepatocyte culture was used as a model system to assess the toxicity of various chemical substances. Chemical substances tested in this experiment included 14 kinds of organic solvents, arsenic acid and N-nitrosodiumethylamine, most of which are known as hepatotoxic materials. Enzyme (GPT and LDH) leakage and albumin secreted from the hepatocytes to culture medium were measured to evaluate the cell damage after exposure to the chemical substances at various concentrations for 3d. Cell counts and protein contents before and after exposure to the chemical substances were also measured during the course of these experiments. The extent of LDH leakge from hepatocytes was parallel to that of GPT leakage after exposure to the chemicals. Albumin secreted from the hepatocytes in the culture medium evidently decreased at concentrations of the chemicals which increased the enzyme leakage. Viable cell counts were significantly decreased by chemicals that increased the enzyme leakage, although the cell protein contents were not significantly affected.
The minimum concentration of the chemicals at which enzyme leakage from hepatocytes was significantly increased was defined as the lowest toxic concentration (TCL₀). Judging from TCL₀ values, the degree of toxicity in these chemicals seems to be almost identical to the degree of in vivo hepatotoxicity reported previously. We, furthermore, observed that there is a positive correlation (r=0.780, p<0.01) between PT₅₀ calculated by the LD₅₀ value reported previously and -Log|TCL₀|. These results indicate that the cultured rat hepatocytes can be applied to the selection test for hepatotoxic materials and also to short-term toxicity assessment of chemicals which affect liver function.

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THA (Tokai High Avoiders) rats were exposed in the exposure chambers to 100 and 500 ppm of toluene and air for 7 h every day from 13th day of gestation to 48 d of age. After the termination of toluene exposure, Sidman avoidance test was conducted on the rats for 10 d from 49 d of age (first test series), 100 d of age (second test series) and 150 d of age (third test series).
The results obtained are as follows.
1) No difference could be observed between the toluene exposed groups and controls in the initiation of pinna detachment, primary coat of downy hair, incisor eruption and eye opening. The body weight of the 100 ppm exposed group was slightly greater than that of the control and the 500 ppm exposed group. No difference was indicated between these three groups in reflex and locomotor activity.
2) Avoidance learning: Avoidance rate in the two exposed groups of male rats was significantly lower than those in the control during the 60 min of the test in the first test series, The magnitude of individual variations of avoidance rate in the two exposed groups of male rats was also remarkably greater than that of the control. No difference was seen between the two exposed groups in both avoidance rate and magnitude of avoidance variation.
In the second and third test series, the avoidance rate of the two exposed groups still did not attain the control levels during the period of the test series.
In female rats, the avoidance rate of the two exposed groups during the first 30 min of the test in the first test series was slightly lower than the control. This difference in avoidance rate observed between the exposed groups and the control disappeared during the latter 30 min of the test. In the second and third test series, the avoidance rate of both exposed groups reached the control level during the test period. It may be concluded from the foregoing findings that 100 ppm and 500 ppm toluene exposure during the fetal and suckling periods affects learning in the rats after termination of the growth period, and that the learning disorder still remained as long as 100 days after the end of toluene exposure, although the effect decerased gradually. It was also observed that this learning disorder appeared more distinctly in male rats than in female rats.

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A study was made on the effect of detection wavelength and separation mode of HPLC on determination of urinary hippuric acid (HA) and three isomers of methylhippuric acid (MHA). The interference of other constituents of urine in the determination was effectively decreased by detection at a short wavelength of 227.6nm. Meta and para MHAs were separated by the addition of β-cyclodextrine to the mobile phase. Four metabolites were successfully separated from other components of urine by the combination of ODS-silica packed-column and mobile phase (method F). The detection limits were found to be 50 and 5mg/l for HA and MHAs, respectively. MHAs could not be detected in the non-exposed subjects. Average levels (±SD) of HA in non-exposed males and females were 272.2 (±210.8) and 393.0 (±269.8)mg/l, respectively. The urinary levels of HA in females were significantly higher than those in males.

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Effects of the difference in input device on work load of VDT task were studied.
The subjects of the experiment were eight healthy male college students (age: 21-22 yr) having a binocular vision of not less than 0.7 and no astigmatism or hyperopia.
The test consisted of an experimental word processing task in which the subjects visually searched e's in given sequences of alphabetical letters displayed on the CRT and converted them to 5's through input device operation.
As for experimental conditions, two kinds of input devices, namely, keyboard and lightpen were adopted and 1 h was provided as each operation time.
Critical flicker fusion (CFF), near point distance, accommodation time, subjective fatigue symptoms, blinking counts, pupillary reflex, electromyogram in upper limb, neck and shoulder and performance score were measured.
The results were as follows.
1) Decrease in C. F. F. was observed in two experimental conditions during the process of operating time.
2) Increments in complaints of subjective fatigue related to visual function were seen in the two experimental conditions after 1 h VDT task.
3) A higher error rate in performance was observed in the subjects using the lightpen compared to the one using the keyboard.
4) The frequency of both blinking and pupil-size changes were lower in the subjects using the lightpen compared to those using the keyboard. This suggests that the gaze time of the VDT screen with lightpen-condition is longer than that in keyboard-condition.
5) Complaints of subjective fatigue to shoulders, back, arm and low back, and also larger amplitude of electromyogram in upper limb, neck and shoulder were observed in the subjects using the lightpen compared to those using the keyboard. This suggests that the muscular load of the upper limbs and the restriction of posture in the lightpen-condition are larger than those of the keyboard-condition.

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