Biomedical subjects

E Shibata

Publications and source records attributed to E Shibata.

At least 37 records · Page 2Linked to original sources

PubMed2000

1-Bromopropane, an alternative to ozone layer depleting solvents, is dose-dependently neurotoxic to rats in long-term inhalation exposure.

1-Bromopropane has been newly introduced as an alternative to ozone layer-depleting solvents. We aimed to clarify the dose-dependent effects of 1-bromopropane on the nervous system. Forty-four Wistar male rats were randomly divided into 4 groups of 11 each. The groups were exposed to 200, 400, or 800 ppm of 1-bromopropane or only fresh air 8 h per day for 12 weeks. Grip strength of forelimbs and hind limbs, maximum motor nerve conduction velocity (MCV), and distal latency (DL) of the tail nerve were measured in 9 rats of each group every 4 weeks. The other 2 rats of each group were perfused at the end of the experiment for morphological examinations. The rats of the 800-ppm group showed poor kicking and were not able to stand still on the slope. After a 12-week exposure, forelimb grip strength decreased significantly at 800 ppm and hind limb grip strength decreased significantly at both 400 and 800 ppm or after a 12-week exposure. MCV and DL of the tail nerve deteriorated significantly at 800 ppm. Ovoid or bubble-like debris of myelin sheaths was prominent in the unraveled muscular branch of the posterior tibial nerve in the 800-ppm group. Swelling of preterminal axons in the gracile nucleus increased in a dose-dependent manner. Plasma creatine phosphokinase (CPK) decreased dose-dependently with significant changes at 400 and 800 ppm. 1-Bromopropane induced weakness in the muscle strength of rat limbs and deterioration of MCV and DL in a dose-dependent manner, with morphological changes in peripheral nerve and preterminal axon in the gracile nucleus. 1-Bromopropane may be seriously neurotoxic to humans and should thus be used carefully in the workplace.

Administration, Inhalation↗

PubMed1999

2-Bromopropane causes ovarian dysfunction by damaging primordial follicles and their oocytes in female rats.

Ovarian dysfunction induced by 2-bromopropane (2-BP) has been described in female factory workers and experimental animals. However, the underlying mechanism is still unclear. To establish the reproductive target site and define mechanisms of 2-BP toxicity in adult female rats, we examined the effects of different doses and duration of exposure to 2-BP in female rats. In the dose-dependent experiments, female rats were exposed to 2-BP at 100, 300, or 1000 ppm or fresh air (n = 9 each) in exposure chambers for 8 h/day for 9 weeks. In the time-course experiments, female rats were exposed to 2-BP at 3000 ppm for 8 h (n = 7 each). The rats were then euthanized 1, 3, 5, and 17 days after exposure. Differential follicle counts and in situ terminal deoxynucleotidyl transferase assay were used to evaluate 2-BP effect on primordial, growing, and antral follicles. Exposure to 2-BP at 300 and 1000 ppm produced a significant reduction in the percentage of primordial, growing, and antral follicles in a dose-dependent manner. Significant reduction in the percentage of primordial follicles at 17 days after exposure was observed in time-course experiments. Exposure to 2-BP at 3000 ppm for 8 h resulted in histological changes in primordial follicles complex at 5 and 17 days after exposure. These changes consisted of distortion of the symmetry of oocytes and their nuclei at Day 5 after exposure and appearance of eccentric pyknotic cells and shrinkage of oocyte nuclei at Day 17 after exposure. In situ end labeling showed increased numbers of apoptotic oocytes and granulosa cells in primordial follicles at Days 5 and 17 after exposure. Our results suggested that ovarian dysfunction induced by 2-BP was caused by the destruction of primordial follicle and its oocyte due to the induction of apoptosis. Our studies also show that the follicle differential count is a more sensitive method than the vaginal smear in monitoring the female reproductive disorders induced by 2-BP.

Animals↗

PubMed1999

Effect of inhalation exposure to 2-bromopropane on the nervous system in rats.

Exposure to 2-bromopropane (2-BP) is suspected to have adverse effects on the nervous system. The aim of this study was to investigate whether the exposure of rats to 2-BP had neurotoxic effects using histological and electrophysiological studies. Wistar strain male rats were exposed daily to either 100 or 1000 ppm 2-BP or to fresh air for 8 h a day for 12 weeks. Body weight was measured before exposure and every 2 weeks. Motor nerve conduction velocity (MCV) and distal latency (DL) were measured before exposure and every 4 weeks during exposure. Histological examination of the nervous system was also performed. Exposure of rats (n = 9) to 1000 ppm resulted in suppression of body weight gain and a significant decrease in brain weight compared to the control (n = 9). Electrophysiological measurements showed a significant decrease in MCV in 1000 ppm exposed rats at 8 weeks and significant prolongation of DL at 8 and 12 weeks. Abnormalities of the myelin sheath were detected in the common peroneal nerves. In 100-ppm exposed rats (n = 9), no significant changes were noted in body weight and the peripheral nerve. In conclusions, long-term exposure to 1000 ppm of 2-BP may result in peripheral neuropathy in rats.

Administration, Inhalation↗

PubMed1999

Haploid loss of bax leads to accelerated mammary tumor development in C3(1)/SV40-TAg transgenic mice: reduction in protective apoptotic response at the preneoplastic stage.

The dramatic increase in apoptosis observed during the development of preneoplastic mammary lesions is associated with a significant elevation in Bax expression in C3(1)/SV40 large T antigen (TAg) transgenic mice. The significance of Bax expression during tumor progression in vivo was studied by generating double-transgenic mice carrying the C3(1)/TAg transgene and mutant alleles for bax. C3(1)/TAg transgenic mice carrying mutant bax alleles exhibited accelerated rates of tumor growth, increased tumor numbers, larger tumor mass and decreased survival rates compared with mice carrying wild-type bax. Accelerated tumorigenesis associated with the bax+/- genotype did not require the loss of function of the second bax allele. Thus, haploid insufficiency of bax is enough to accelerate tumor progression, suggesting that the protective effect of Bax is dose-dependent. While levels of apoptosis in the preneoplastic lesions, but not carcinomas, were reduced in bax+/- or bax-/- mice compared with bax+/+ mice, rates of cellular proliferation in mammary lesions were similar among all bax genotypes. These data demonstrate that bax is a critical suppressor of mammary tumor progression at the stage of preneoplastic mammary lesion development through the upregulation of apoptosis, but that this protective effect is lost during the transition from preneoplasia to invasive carcinoma.

Animals↗

PubMed1999

Decreased antipyrine clearance following endotoxin administration: in vivo evidence of the role of nitric oxide.

Klebsiella pneumoniae endotoxin has been found to decrease hepatic P450-mediated drug-metabolizing enzyme activity in a time-dependent manner. In this study, we investigated the role of nitric oxide (NO) in the decrease in hepatic drug-metabolizing enzyme activity caused by endotoxin in vivo. We measured in vivo pharmacokinetic parameters of antipyrine in rats treated with endotoxin and/or a selective inhibitor of inducible NO synthase (iNOS), S-methylisothiourea. Intraperitoneal injection of endotoxin (1 mg/kg of body weight) dramatically decreased the systemic clearance of antipyrine, reflecting reduced hepatic drug-metabolizing enzyme activity, and significantly increased the level of nitrite and nitrate (NOx) in the plasma. S-Methylisothiourea (10 mg/kg) reversed this decreasing antipyrine clearance and reduced the level of NOx in plasma. Repeated injections of an NO donor, (+/-)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide (FK-409; 10 mg/kg), at a dose which maintained plasma NOx at the same levels as those caused by endotoxin injection, also decreased the systemic clearance of antipyrine. These findings suggest that the overproduction of NO observed in this animal model is at least partially responsible for the significant reduction in the hepatic drug-metabolizing enzyme activity that may happen in a gram-negative bacterial infection.

Animals↗

PubMed1999

Association between musculoskeletal pain in Japanese construction workers and job, age, alcohol consumption, and smoking.

A cross-sectional epidemiologic study was conducted to determine the prevalence of self-reported musculoskeletal pain (MSP) in construction workers and identify associations between MSP and individual factors (i.e., job, age, alcohol consumption, and smoking). The prevalence of total hand/arm pain (T-HAP), total shoulder pain (T-SP), and total low-back pain (T-LBP) was 28.4%, 28.7%, and 53.2%, respectively. Risk factors for total pain and for relatively severe pain in the hand/arm (RS-HAP), shoulder (RS-SP), and low-back (RS-LBP) were estimated by multiple logistic regression analysis. The results showed that musculoskeletal pain was significantly associated with age, and that the odds ratios (ORs) for relatively severe musculoskeletal pain increased almost linearly with age. Regarding job, compared with architects whose work is presumed to be sedentary, almost all ORs for T-HAP, T-SP, and T-LBP for non-sedentary construction jobs were significantly high. Current smokers of 20 cigarettes a day or more had significantly higher ORs for RS-HAP and RS-LBP than "never smokers". We suppose that 1) total and relatively severe pain were associated with age, 2) non-sedentary work was at higher risk of total MSP than sedentary work, and 3) heavy smoking contributed to RS-LBP.

Adult↗

PubMed1998

2,5-Hexanedione concentrations and morphological changes within the eye of albino rat.

Exposure to 2,5-hexanedione (2,5-HD), a major n-hexane metabolite, can cause loss of photoreceptor cells, particularly when combined with light energy. The aims of this study were to document the levels of 2,5-HD reached in relation to time in retina, aqueous humor, and serum of the Sprague-Dawley albino rat after: (1) a single oral administration of 2,5-HD (0.04 g/ kg body wt.) by tube feeding; and (2) after subchronic oral administration of 2,5-HD. In addition, morphometric analysis of the retina was carried out to evaluate cell loss at the end of administration and after various periods of recovery. The 2,5-HD concentration in retinal tissue, aqueous humor, and serum reached a peak within 1 h after exposure to a single dose of 2,5-HD. Twenty four hours after the exposure, only a minor amount of 2,5-HD could be detected in the retina and aqueous humor. When 2,5-HD was administered subchronically (0.04 g/kg body wt. per day, for 35 days) no loss of photoreceptor cells was seen immediately after the end of exposure or at the end of a 4-week recovery period. Rats exposed to 0.60 g/kg body wt. per day for 11 days showed no significant loss of photoreceptor cells immediately after the end of exposure but there was a substantial loss of photoreceptor cells after 2 and 4 weeks of recovery. The results demonstrate that 2,5-HD reaches the aqueous humor and retina, and penetrates blood-aqueous humor/retina barriers after oral administration. Moreover, retinal degeneration seen in the animals may be directly caused by 2,5-HD and these changes are dose dependent.

Administration, Oral↗

PubMed1998

Urinary 2,5-hexanedione increases with potentiation of neurotoxicity in chronic coexposure to n-hexane and methyl ethyl ketone.

OBJECTIVE: MEK (methyl ethyl ketone) is widely and frequently used as an ingredient of mixed solvents together with n-hexane. MEK is known to decrease urinary levels of 2,5-hexanedione dose-dependently in an acute or chronic coexposure with a constant level of n-hexane. This change in urinary 2,5-hexanedione appears to contradict the potentiation effect of MEK on n-hexane-induced neurotoxicity because it is believed that the toxicity of n-hexane is activated through n-hexane metabolism. We aimed to clarify how the urinary level of 2,5-hexanedione changes when MEK modifies the degree of n-hexane-induced neurotoxicity. METHOD: A total of 32 male Wistar rats were divided into 4 groups of 8 each and were then exposed to fresh air only, 2000 ppm n-hexane only, 2000 ppm n-hexane plus 200 ppm MEK, and 2000 ppm n-hexane plus 2000 ppm MEK, respectively. Inhalation exposures were performed 12 h/day, 6 days/week, for 20 weeks. Motornerve conduction velocity (MCV), distal latency (DL), and urinary 2,5-hexanedione were measured every 4 weeks. RESULTS: The MCV decreased, the DL increased, and urinary levels of 2,5-hexanedione increased in the 2000-ppm n-hexane plus 200 ppm MEK group in comparison with the 2000-ppm n-hexane only group following 4 weeks' exposure. On the 1st day of exposure, however, coexposure to MEK decreased urinary levels of 2,5-hexanedione dose-dependently. CONCLUSIONS: The present study showed that urinary concentrations of 2,5-hexanedione increased with potentiation of n-hexane neurotoxicity. Urinary 2,5-hexanedione concentration does not necessarily reflect the exposure concentration of n-hexane in coexposure to n-hexane along with MEK or other solvents, but it may be useful as a marker in the assessment of neurotoxicity in coexposure to n-hexane and other solvents.

Animals↗

PubMed1998

[Types and dimensions of mineral fibers in the atmosphere and from lungs of residents in the urban area].

OBJECTIVE: The objective of this study was to estimate the types and origin of the mineral fibers in the lungs of residents in the urban area. METHODS: Mineral fibers in the atmosphere from 21 urban areas were analyzed by direct transfer-analytical transmission electron microscopy (ATEM). Lung tissues of 36 urban residents without occupational asbestos exposure were also analyzed by ATEM after low temperature ashing. Measurement of dimensions of all types of mineral fibers, identification of asbestos, and classification of nonasbestos fibers according to the combination of main elements were carried out. RESULTS: 1. Chrysotile, amosite, actinolite, tremolite and 11 types of nonasbestos fibers were found in both the lung tissues and the atmospheric samples. The fibers, mainly composed of Al and Si, contributed 16.3% and 62.3% of the atmospheric samples and lung tissues respectively. On the other hand, the proportion of the fibers mainly composed of S and Ca were 43.7% and 0.0% in the atmosphere and lung tissues respectively. Those fibers mainly composed of P and Fe were 0.4% and 18.4% in the atmosphere and lung tissues respectively. 2. Fifteen types of nonasbestos fibers were found exclusively in the atmosphere. The average proportions for ten of these were less than 0.5% each. 3. Crocidolite was found exclusively in the lung tissues. 4. No significant difference in the geometric mean of length and diameter of asbestos was found between the atmospheric samples and lung tissues. Some types of nonasbestos fibers had significantly larger length and diameter in the atmospheres than in the lung tissues (p < 0.01). CONCLUSION: The results suggest that mineral fibers found in lung tissues could be classified into three groups on the basis of their behavior. 1) Some fibers, such as amphibole asbestos and fibers composed of Al and Si, are inhaled from the atmosphere and remain in the lung tissues for a long time. 2) Some fibers, such as those composed of S and Ca, are inhaled from the atmosphere and eliminated from the lung tissues within a relatively short time. 3) Some fibers found more in the lung tissues than in the atmospheres, such as those composed of P and Fe, are suspected to be generated in the lungs.

Air Pollutants↗

PubMed1997

A cohort mortality study of construction workers.

This report presents a mortality study among the 17,344 members of the Construction Workers' Health Insurance Society of Mie Prefecture in Japan. The study period was between 1973 and 1993. During this period, 480 members died. Age-specific mortality rates of Mie Prefecture were used as comparison standards. Significantly elevated standardized mortality ratio (SMR) and proportionate mortality ratio (PMR) were observed for "accidents and adverse effects." In addition, the PMRs of all cancers and "cancers of trachea, bronchus and lung" were also significantly elevated. The job classifications were reorganized into three groups, according to the frequency of asbestos exposure the workers experienced on the construction sites. The asbestos exposure was based on job classifications among 7,411 workers who had completed a self-administered survey questionnaire. In the frequent-exposure group, the PMR was significantly elevated for all cancers. In the medium-exposure group, the SMRs were significantly elevated for all cancers and "cancer of trachea, bronchus and lung." The PMR was significantly elevated for "cancer of trachea, bronchus and lung." In the less-exposure, group, the PMR was significantly elevated for "accidents and adverse effects." This study provided support for the hypothesis that working in the construction industry might be associated with high risks for asbestos-associated cancers and accidental deaths.

Accidents, Occupational↗

PubMed1997

Pulmonary metal distribution in urban dwellers.

To clarify the factors influencing the concentrations and distribution of metal elements in the lung, we analyzed the following 8 metals in the 5 lung lobes of 17 autopsied urban dwellers by flame or flameless atomic absorption spectrometry: aluminum (Al), cadmium (Cd), chromium (Cr), nickel (Ni), lead (Pb), manganese (Mn), copper (Cu), and Zinc (Zn). The arithmetic mean value (in micrograms of metal per gram of dry weight) calculated for five lobar metal concentrations in each subject ranged from 80 to 681 for Al, from 0.34 to 3.41 for Cd, from 0.41 to 12.7 for Cr, from 0.22 to 1.93 for Ni, from 0.15 to 1.47 for Pb, from 0.64 to 2.36 for Mn, from 2.84 to 7.24 for Cu, and from 40.7 to 77.6 for Zn. The eight metals were classifiable into two groups on the basis of the interindividual and interlobar concentration variations. The first group, consisting of Cu and Zn, was characterized by smaller interindividual variations (co-efficient of variation, CV < 30%) and smaller inter lobar variations (mean CV < 15%). Their levels were not affected significantly by sex, smoking habits, or possible occupational exposure to metal-containing dust. In contrast, the second group, consisting of Al, Cd, Cr, Ni, Pb, and Mn, exhibited larger interindividual variations (CV > 45%) and larger interlobar variations (mean CV > 25%). Concentrations of these metals, except for Cd, tended to be higher in the upper lobes than in the lower lobes. The concentrations of Al and Cr were significantly higher in men than in women. Smoking significantly elevated the levels of Cr, Cd, Ni, and Pb, and the concentrations of Al, Cr, Ni, and Mn were higher in subjects with possible occupational exposure to metal-containing dust than in those without such exposure. However, the interlobar distribution patterns of the metals did not seem to be influenced by sex, smoking habits, or occupational exposure to metal-containing dust.

Adult↗

PubMed1997

An efficient SAS program for extract stratification of person-years.

An efficient Statistical Analysis System computer program for the exact stratification of person-years is described, in order to determine the expected number of deaths or cases of diseases in a cohort for the calculation of standardized mortality ratios or standardized morbidity ratios. A comparison of this program with Macaluso's "Method B" program shows that the speed of the former is considerably faster than that of the latter, when the widths of the categories defined by all of the time factors are identical.

Age Distribution↗

PubMed1997

Ganglioneuroma of left adrenal gland in a patient with Turner syndrome during growth hormone therapy.

We report on a Japanese girl with Turner syndrome (45,XO) who developed ganglioneuroma of the left adrenal gland during growth hormone (GH) therapy. She had received GH replacement therapy from the age of 6.8 years. At the age of 10.3 years, abdominal ultrasonography revealed a mass which occupied the upper area of her left kidney. Computed tomography and magnetic resonance imaging of the abdomen showed a low density mass with a smooth surface located between the upper portion of the left renal vein and the pancreas. Microscopic examination resulted in a diagnosis of ganglioneuroma of the left adrenal gland. At present we cannot conclude that patients who have received GH replacement therapy are at higher risk for developing tumors compared to those without GH replacement therapy.

Adrenal Gland Neoplasms↗

PubMed1996

Role of tachykinin and bradykinin receptors and mast cells in gaseous formaldehyde-induced airway microvascular leakage in rats.

We have investigated the effects of CP-99,994 [(+)-(2s,3s)-3-(2-methoxybenzylamino)-2-phenylpiperidine], a tachykinin NK1 receptor antagonist, HOE 140 (D-Arg[Hyp3,Thi5,D-Tic7,Oic8]bradykinin), a bradykinin B2 receptor antagonist, and ketotifen (4-(1-methyl-4-piperidylidene)4 H-benzo[4,5]cycloheptal[1,2-b]thiophen-10(9H)-one hydrogen fumarate), a histamine H1 receptor antagonist with mast cell-stabilizing properties, on microvascular leakage induced by gaseous formaldehyde. Extravasation of Evans blue dye into airway tissues was used as an index of airway microvascular leakage. Leakage of dye in the trachea and main bronchi increased significantly in a concentration-dependent fashion after 10 min inhalation of formaldehyde (5-45 parts per million (ppm)). The airway response induced by 10 min inhalation of 15 ppm formaldehyde (trachea: 119.5 +/- 13.9 ng/mg, n = 7; main bronchi: 139.6 +/- 7.9 ng/mg, n = 7) was abolished by the administration of CP-99,994 (3 and 6 mg/kg i.v.), but not by the administration of HOE 140 (0.65 mg/kg i.v.) nor ketotifen (1 mg/kg i.v.). The increase in vascular permeability induced by formaldehyde in the rat airway was mediated predominantly by NK1 receptor stimulation. Activation of bradykinin receptors and mast cells did not appear to play an important role in this airway response.

Animals↗

PubMed1996

Toxic effects of hexane derivatives on cultured rat Schwann cells.

The cytotoxic effects of the following five hexane-related compounds were examined on Schwann cell DNA synthesis: 2,5-hexanedione (2,5-HD), 2-hexanol (2-OH), 2-hexanone (MnBK), 2,5-dimethylfuran (DF) and gamma-valerolactone (VL). Schwann cells were isolated from the sciatic nerves of neonatal Sprague-Dawley rats and cultured. [(3)H]-thymidine incorporation into Schwann cell nuclei was measured by scintillation spectrometry and autoradiography when hexane derivatives were added to the culture medium. All of the hexane-related compounds suppressed [(3)H]-thymidine incorporation in a concentration-dependent manner. DF was the most cytotoxic for the inhibition of Schwann cell DNA synthesis among the compounds. The finding suggests that DF-mediated cytotoxicity should be taken into account as a possible additional mechanism of hexane intoxication, especially in the impairment of mitotic cells.

Animals↗

PubMed1996

Effects of asymmetric dynamic and isometric liftings on strength/force and rating of perceived exertion.

A laboratory study was undertaken to determine the postural and physical characteristics and subjective stress during dynamic lifting of a usual load (10 kg) compared with during isometric lifting. The authors also aimed to clarify the effects of asymmetric lifting on these parameters. The subjects were thirteen male college students. They were asked to lift a box weighing 10 kg. They performed sixteen different lifting tasks from the floor to a height of 71 cm, involving a combination of three independent factors: two lifting modes (isometric lifting and dynamic lifting), four lifting angles in relation to the sagittal plane (sagittal plane, right 45 degree, right 90 degree and left 90 degree planes) and two lifting postures (squat and stoop). For each lifting task, strengths or forces and ground reaction forces were measured. At the end of each task, the authors asked the subjects to rate their perceived exertion (RPE) during lifting at ten sites of the body. Angle factor had a significant effect on isometric strengths and dynamic peak forces. Isometric strengths during the maximum 3 s were highest in lifting in the right 45 degree plane, followed by that in the sagittal plane, while those in the right 90 degree and left 90 degree planes were the lowest. However, peak forces in dynamic lifting were the highest in the lifting in the sagittal plane, followed by that in the right 45 degree plane, while those in the right 90 degree and left 90 degree planes were the lowest. Postural factor had a significant effect on height at peak force, which is higher in squat lifting than in stoop lifting. RPEs for the left arm, the backs and the right whole body in isometric lifting were significantly higher than in dynamic lifting of 10 kg. There were remarkably high RPEs for the ipsilateral thigh to the box in right 90 degree and left 90 degree planes during both isometric and dynamic liftings. Locations of the resultant force consisting of three component forces on the force plate were closer to the foot on the same side as the box in asymmetric lifting. Thus, some similarities and differences were found between isometric lifting and dynamic liftings regarding the indexes of strength used in this experiment. The authors consider that the subjects used the foot nearer to the box as a fulcrum during asymmetric lifting. Dynamic measurement using the 10 kg weight is less stressful than the conventional isometric measurement. It was possible to obtain the height data at peak force and time-based changes in the force and the box location during lifting only through dynamic lifting measurement. The results provide new knowledge about the biomechanical features of dynamic lifting tasks.

Adolescent↗

PubMed1996

Elevated urinary cadmium concentrations in a patient with acute cadmium pneumonitis.

BACKGROUND: Acute serious inhalation of cadmium fumes often causes chemical pneumonitis or metal fume fever. Because symptoms of both diseases begin several hours after exposure and closely mimic each other, one often mistakes chemical pneumonitis for metal fume fever in the early stages. It is, however, essential to differentiate between the two since chemical pneumonitis can progress to serious consequences. CASE: A 43-year-old man was admitted to the hospital 2 d after exposure to cadmium fumes. The initial diagnosis was metal fume fever on the basis of his history, and he was treated accordingly. His symptoms worsened however, and transient renal impairment was identified as consistent with cadmium-induced renal toxicity. Although the possibility of drug-induced renal damage could not be excluded, abnormal urinalysis findings on admission suggested that the renal tubular damage was caused by inhaled cadmium before admission. CONCLUSIONS: Measuring the urinary cadmium concentration is an effective method for confirming acute cadmium poisoning.

Adult↗

PubMed1996

[Concentration and fiber size of asbestos in lungs of residents living close to the serpentinite area].

Concentrations and fiber size distribution of asbestos in the lung tissue of 16 ( 8 males and 8 females) rural residents living close to the serpentinite area (neighboring group) were analyzed by low temperature ashing-analytical transmission electron microscopy, and were compared with those of 5 (5 males) rural and 53 (34 males and 19 females) urban residents living away from the serpentinite area (reference group). The results are as follows; 1. Pulmonary asbestos fibers were found in all rural residents. The types of asbestos fibers were chrysotile, amosite, crocidolite, actinolite, and tremolite. These findings were very similar to results for urban residents. 2. In males, the geometric mean concentration of actinolite-tremolite in the neighboring group (1.78 x 10(6) fibers/g dry lung) was significantly higher than those in the reference groups (rural: 0.32 x 10(6), urban: 0.31 x 10(6), p < 0.01). In females also, the geometric mean concentration of actinolite-tremolite in the neighboring group (0.59 x 10(6)) was significantly higher than that in the reference group (urban: 0.16 x 10(6), p < 0.05). There were no significant differences in the actinolite-tremolite concentrations between males and females in the neighboring group. 3. The serpentinite in this area have contained not only chrysotile but also both actinolite and tremolite. There was no significant relationship between actinolite-tremolite concentration and occupational history in the neighboring group. It is possible that actinolite and tremolite are liberated from the serpentinite to the atmosphere and inhaled by the residents near the serpentinite area which increases pulmonary actinolite-tremolite concentration. 4. The difference in the geometric mean concentration of chrysotile between the neighboring and the reference group was not statistically significant for both sexes, possibly due to the poor durability of chrysotile in the lung tissue. 5. There were no significant differences in the geometric mean of fiber length and diameter of actinolite-tremolite between the neighboring and the reference group.

Adolescent↗