The progression of visual and mental strain in VDT work was investigated through an experimentally-designed VDT task providing a number of stressors including pacing, repetition, judgment and output decisions. We measured the effects of CFF (critical fusion frequency), TAF (the ability to maintain concentration), EEG (electroencephalogram) and near-point accommodation of various changes in the duration of the testing period. The subjects were seven male university students who performed single multiplication problems at a rate of 60 per minute. The problems were presented to them on a CRT screen and on paper for periods of 90 min each.
The results obtained were as follows;
1) CFF values and near-point accommodation of VDT performance were significantly decreased compared to Non-VDT's as a control. The TAF test showed that the mental strain in a VDT task is greater than that in a Non-VDT task.
2) CFF values of VDT performance showed a tendency to decline in the 30th min after commencement, but in the 60th min and thereafter a significant lowering was noticed.
3) In TAF and near-point accommodation of VDT performance, the greatest decline was in the 60th min, and this was significantly reduced only immediately after the work period.
4) CFF values and near-point accommodation were not recovered after 60 min from the end of a 90 min VDT task. However, TAF·L values recovered in the 30th min after VDT performance.
5) The peak level of alpha waves from the parietal region moved toward the slow alpha band with the elapse of VDT task time, but returned [or reverted] to the initial state 30 min after the test period ended.

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It is presumed that systemic hypotension resulting from high concentration of 1, 1, 1-trichloroethane (1, 1, 1-TCE) inhalation may be induced by functional depression of the central nervous system. However, it is still uncertain the possibilities that one of the site of action where 1, 1, 1-TCE acts in systemic hypotension existed in the portion without the central nervous system. The present experiment was performed to investigate the role of the peripheral vessels as a site of action in the systemic hypotension following 1, 1, 1-TCE inhalation.
The right hindlimb of a dog anesthetized with sodium pentobarbital (25-30 mg/kg, intravenously) was amputated at the central level of the thigh bone leaving muscles and nerves. The isolated hindlimb was perfused with blood at a constant flow rate using a pump. Venous blood circulated in the isolated hindlimb was returned to the femoral vein. To measure the perfusion pressure of the isolated hindlimb, a small catheter was inserted into the artery and was connected to a pressure transducer (Nihon Kohden, MPU-0.5). In this perfusion experiment, the changes in perfusion pressure following 1, 1, 1-TCE inhalation are shown to be the reaction of peripheral vessels only as the site of action of 1, 1, 1-TCE. In other words, the effects of 1, 1, 1-TCE on central nervous system could be completely removed. Various concentrations of 1, 1, 1-TCE vapor, made by an inside circuit vaporizer, were inhaled during a period of approximately 2 min. Perfusion pressure was continuously recorded before, during and after the termination of inhalation. Concentrations of 1, 1, 1-TCE in the inspired air were measured by gas chromatography.
In an acute inhalation experiment, a fall in perfusion pressure was observed following 1, 1, 1-TCE inhalation. The fall in perfusion pressure gradually returned to the pre-inhalation level. The threshold concentration of 1, 1, 1-TCE to produce the fall in perfusion pressure was about 0.4 to 0.5% in inspired air, and a dose-response relationship was observed between the fall in perfusion pressure and the concentrations of 1, 1, 1-TCE exceeding the threshold level. The fall in perfusion pressure resulting from 1, 1, 1-TCE inhalation in concentration of 2.0 to 3.8% was not affected by pre-treatment with atropine (1.0 mg/kg, iv), propranolol (2.0 mg/kg, iv) or phentolamine (1.0 mg/kg, iv).
From these results, the following conclusions were arrived.
1) One of the sites of action for 1, 1, 1-TCE may be the peripheral vessels, and the peripheral vasodilator effect as a site of action may be related to systemic hypotension following 1, 1, 1-TCE inhalation.
2) The threshold concentration of 1, 1, 1-TCE required to induce a peripheral vasodilator effect is 0.4 to 0.5% in inspired air, and a dose-response relationship exists between the concentration of 1, 1, 1-TCE and peripheral vasodilatation.
3) The peripheral vasodilator effect as a site of action for 1, 1, 1-TCE is not related to the sympathetic and parasympathetic nervous system.

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Combined effects of noise and local vibration on the threshold of acoustic reflex (ART) were investigated. ARTs for three different stimuli (ARTWN, ART_1k, ART_4k) were determined in workers using hand-held vibration tools. The results obtained from these 72 workers (Group A) were compared with the ARTs in 100 control subjects (Group C) who had normal hearing acuity without any history of occupational noise exposure, as previously reported by the authors.
The mean age in group A was 46.6 ranging from 26 to 62. The mean period of noise and vibration exposure was 11.4 years in subjects mainly using chain saws and 9.2 years in subjects mainly using bush cleaners (Table 2). ARTWN and ART_1K in the exposed group showed significant differences compared to those in the non-exposed group (p<0.001), i.e., mean ARTWN was 89.6 dB SPL in Group A and 83.8 in Group C, mean ART_1K was 96.1 dB SPL in the former and 92.2 in the latter group (Table 7). No significant difference was observed in mean ART_4k between the two groups (p>0.1). The difference between ART_1K and ARTWN, [ART_1k-ARTWN], was significantly reduced in the exposed group (p<0.001), i.e., 2.7dB in Group A and 12.4 in Group C (Table 8). To clarify the effects of aging on [ART_1k-ARTWN], the exposed group was classified into three groups according to their HL_(4k+8k)/2. However, no significant correlation was observed between [ART_1k-ARTWN] and age in any of these 3 groups (p>0.1). Furthermore, it was important that [ART_1k-ARTWN] was reduced significantly (p<0.001) even in Group D with normal hearing acuity (HL_(4k+8k)/2<25 dB).
The present results were approximately in agreement with the results of the previous study of workers exposed to noise (Miyakita et al., 1981), and specific effects of local vibration were not observed on their ARTs. Although both noise and vibration are known to stimulate the sympathetic nervous system and may affect whole body in various manners, the effects of local vibration on the auditory organ and its mechanism have never been adequately elucidated. Further field and experimental studies are needed to resolve this complex problem in the future.

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マウス(IVCS雌)をメチル水銀含有飼料(水銀として10nmol/gの濃度で)および亜セレン酸含有飲料水(セレン濃度: 0, 8, 20, 50nmol/ml)で1週間または2週間飼育した.亜セレン酸の投与量および飼育期間によって臓器中全水銀,無機水銀濃度は変化した.
全水銀濃度はセレン投与量の増加に従い,脳,肝で増加,血液,腎,脾で減少した.無機水銀濃度は同じくセレン投与量の増加に従い,肝,脾で増加,腎で減少したが,脳では変化しなかった,全水銀中の無機水銀の割合は,肝,脾で上昇,脳,腎では不変である.なお血中無機水銀濃度はすべて検出限界に達しなかった.

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著者らは1978年以来,桜島の爆発により,鹿児島市内に落下した火山灰を採取し,ラットおよび家兎を用いての動物実験により,火山灰粉塵の気管内注入ならびに,粉塵吸入による呼吸器への影響について研究を行なった.
火山灰の化学的分析によれば, SiO₂の含有量が極めて多くて約58%を占め,次いでAl₂O₃, Fe₂O₃, CaO, TiO₂, MnO, P₂O₅, MgOなどの成分を有しており, silicosis発生の可能性が十分認められる.火山灰吸入家兎に, X線所見として粒状陰影も認められた.
次に火山灰粉塵の粒度分布をみるに, 10μm以下の粒子が, 270 mesh以下で93.25%, 325 mesh以下で99.05%を占めており,肺内深く侵入するこれらの粉塵は,気管内注入によっても,また吸入実験によっても,呼吸器に対する病変は著明で,粉塵は肺胞内に密に沈着し,一部はリンパ流にのって血管周囲に,あるいは気管支周囲に沈着し,喰細胞に貪食され,粉塵細胞を形成し,相隣接した肺胞に粉塵細胞が密在して,粉塵結節を形成する.この粉塵細胞の壊死や空胞形成により,線維細胞や小円形細胞等の細胞反応が現われ,これと同時に肺胞壁にガラス様変性が出現し,膠原物質の沈着がみられる.細胞反応はまた線維細胞増殖の増加となり,膠原線維が認められ,網状となってくる.そして粉塵結節がみられるにいたる.
著者らは,火山灰の呼吸器に対する作用として,病理組織学的に,気管支炎,肺気腫や無気肺,血管変化,粉塵結節や粉塵性線維化巣等を伴う塵肺症を発生することを実証することができた.
したがって,火山灰吸入の有害性について,十分認識することが必要であるとともに,これに対する予防対策,あるいは解決策を真剣に考えなければならない.

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The DNA-damaging activities of organic rubber additives such as rubber vulcanizing agents, vulcanization accelerators and rubber anti-oxidants were investigated by the rec-assay using spores of Bacillus subtilis strains H 17 and M 45. For metabolic activation, 9, 000×g supernatant solutions of the liver homogenate of Sprague-Dawley male rats previously treated with aroclor 1, 254 were used.
Spore rec-assays were carried out at the dose of 1 mg/disk, and the ratio of inhibition zones for M 45 to that for H 17 was calculated. Samples showing a ratio of more than 1.2 were judged positive. In order to know the DNA-damaging capacity of positive samples, the dose-response curves were prepared by carrying out the assays at various doses, and minimal inhibition concentration (MIC) for H 17 and M 45 was obtained from these curves by extrapolation. Then indices of DNA damagenicity were calculated through division of the MIC obtained with H 17 by that with M 45. The 0.005 μg/disk of mitomycin C and at 4 μg/disk of Trp-Pl were used as positive control, and the 50 μg/disk of kanamycin as negative control.
The results obtained are as follows:
1) Among 20 tested samples, p-quinone dioxime, bis-morpholine disulfide used as rubber vulcanizing agents and hexamethylenetetramine, zinc butylxanthate used as vulcanization accelerators gave positive results.
2) It was considered that the action of hexamethylenetetramine against DNA was due to the electrophilic state of this material. Furthermore, we supposed that DNA-damaging activity of p-quinone dioxime was concerned with free hydroxyl groups of this compound.
3) Indices of DNA damagenicity of p-quinone dioxime and bis-morpholine disulfide were increased and those of hexamethylenetetramine were decreased by carrying out metabolic activation, compared with the results without metabolic activation.
4) The DNA-damaging activity of zinc butylxanthate was caused to disappear by metabolic activation.
5) The sensibility of tested rubber anti-oxidants against Bacillus subtilis was very low, and 5 of 6 samples did not show antibacterial properties on the plates at the dose of 1 mg/disk.
6) The antibacterial activity of tetramethylthiuram disulfide used as vulcanization accelerators was as strong as that of kanamycin.

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著者らは農村婦人の貧血について研究を進めているが,その一環として, 1971年に一地方中核都市および周辺農村に居住する10職種(製靴工場,専売公社,バス会社,デパート従業員,栄養士,看護婦,看護学生,住宅街および近郊団地主婦,農村婦人) 1,926名を対象に血色素,血液比重,ヘマトクリット,血清鉄の測定を実施した.その結果,製靴工,看護婦,農村婦人が低値,看護学生,栄養士,住宅街主婦が高値を示した.同じ年齢層についてみても同様の傾向が見られた.製靴工,栄養士,看護婦,看護学生,住宅街主婦および農村婦人は1966年にも同様の調査を実施しているが,農村婦人の血色素水準の上昇が最も顕著であった.同じ職種の中では,未婚者より既婚者の血色素水準が低く,既婚者では乳児を持つ母視の水準が低く,婦人労働者の血色素水準は職場の労働条件のみならず,家庭の条件に強く規定されていることが示唆された.

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Brief treatment (3 min at 37°C) of human neutrophils with triphenyltin chloride (TPTCl) resulted in a dose-dependent inhibition of superoxide (O₂) production stimulated by concanavalin A+cytochalasin D. It was considered from the following findings that the inhibition may be caused by some functional disorders of neutrophils: 1) _O₂ generated by xanthine oxidase-acetaldehyde system was not inhibited by TPTCl. 2) There was no change in cell viability after treatment with TPTCl. When the other phenyltin compounds were examined, the relative potencies of inhibitory effect were shown to be in the order of TPTCl>diphenyltin dichloride>phenyltin trichloride>tetraphenyltin on a molar basis. Lysosomal enzyme release caused by neutrophils stimulated by N-formyl-methionyl-leucyl-phenylalanine (FMLP) was also inhibited by TPTCl. These results suggest that TPTCl inhibits the common pathway (s) of the two stimulus responses.

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Vibration hazards were surveyed in a population of quarry workers using chipping hammers and to a lesser extent, rock drills.
1. Sixty-nine male quarry workers, aged 49.1±8.7 and exposed to vibration for 16.4±5.1 years, were surveyed in 1981-82. They were exposed to vibration for about 2-4 hours per days, mainly under a piece-work pay system.
They had a high prevalence of Raynaud's phenomenon (36.2%) and numbness in upper extremities (53.6%). It is considered that the high prevalence was mainly due to large vibration levels in chipping hammers and rock drills and long daily exposure time.
The attacks of Raynaud's phenomenon were found predominantly in the left hand, which held chisels, whereas the restriction of motion in the elbow was predominantly in the right arm which pushed chipping hammers.
2. The same 49 male quarry workers in this population were also surveyed in 1976-77 and the prevalence of their complaints between 1976-77 and 1981-82 was compared.
The prevalence of Raynaud's phenomenon was the same, but the frequency of the attacks increased between the two periods. The prevalence of other complaints such as numbness, pain and chills in the upper extremities also increased.
Between 1976-77 and 1981-82, the prevalence of Raynaud's phenomenon, numbness, and pain in the upper extremities increased in the population of quarriers exposed to vibration for above 2.6 hours per day and 200 days per year, or 600 hours per year. On the other hand, the prevalence of these complaints mostly decreased in the population of quarriers with less exposure. These results suggest that a low limit of exposure time would be effective for the prevention of vibration diseases.

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