The autonomic nervous effects of toluene remain less clear. To clarify this neurotoxicity, ten rotogravure printers and the same number of age-matched unexposed controls were examined, by using the coefficient of variation in electrocardiographic R-R intervals (CVRR), the distribution of nerve conduction velocities (DCV) and the maximal motor and sensory nerve conduction velocities (MCV and SCV) in the median nerve. Also, the C-CVHF and C-CVLF (two component CVs of the CVRR reflecting parasympathetic and sympathetic activities, respectively) were computed from component spectral powers using autoregressive spectral and component analyses. These printers had been exposed to toluene (estimated exposure levels of toluene at 83 ppm) for 1-36 years. The CVRR and C-CVHF were significantly lower in the printers than in the controls. No significant difference between the printers and the controls was found in either any DCV parameters or the SCV in the forearm, except the MCV and the SCV in the palm. In the light of previous work on the brainstem/hippocampus damages due to toluene, these data suggest that toluene causes potential damages in the central autonomic nervous system, mainly parasympathetic hypoa-ctivity.
An accurate and simple procedure for determining the quantity of freesilica in respirable dust samples by the pyrophosphoric acid method was achievedby employing a closed vessel dissolution technique using microwave heating. Dissolution conditions were optimized by using quartz particles less than 10 μm in diameter as representative respirable-size free silica and potassium feldspar (K-feldspar) of the same size as the matrix. The technique enabled dissolution of 100 mg of K-feldspar by pyrophosphoric acid in 3 min. Quartz recovery was 97% under these conditions. The technique was also tested on mixtures of quartz and K-feldspar in various ratios with reproducible and accurate results. These data satisfy the requirements for analysis of small amounts of respirable dust samples in work environments.
To examine hormonal response patterns to various stresses, urinary excretion of catecholamines and corticosterone was measured in spontaneously hypertensive rats (SHR) and Wistar-Kyoto normotensive rats (WKY) under the folowing conditions : immobilization, restiriction to a small space, introduction of new rats, and noise exposure. In WKY rats, immobilization caused a marked increase in urinary corticosterone, adrenaline and norad-renaline and a decrease in dopamine excretion. Restriction to a small space induced a less pronounced but still obvious increase in adrenaline and corticosterone and a decrease in dopamine. When other rats were introduced into the animal room, the senior rats showed an increase in adrenaline alone, while noise exposure produced an increase in corticosterone alone. These findings suggest that while severe stress, such as immobilization, causes marked changes in all 4 hormones, relatively mild stress produces changes in one to three, not all, hormones, and that catecholamine and corticosteroid responses are dissociated in some forms of the mild stress. It is considered that neuroendocrine responses to stress vary according to both the type of stress and its intensity. In SHR rats, the hormone response to severe stress was greater than in WKY rats, and the response was somewhat less than in WKY rats when exposed to mild stress. These findings do not imply that stress-induced hyperactivity of sympathetic adrenomedullary system participates in the developmentof hypertension in SHR rats.
The anemia frequently observed in lead poisoning is thought to resultfrom the shortening of erythrocyte life span in combination with inhibition of hemoglobin synthesis. However, the exact mechanism by which lead shortens the life span of red blood cells (RBCs) remains unclear. In the present study, the effects of injected lead on electrophoretic mobility, membrane sialic acid content, deformability and survival of rat RBCs were investigated in order to clarify therelationships between them. As indices of lead exposure, RBC counts, hemoglobin (Hb) levels, hematocrits (Ht), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC) and blood lead(blood Pb) levels in the rats were also examined. Exposure to lead significantlydecreased RBC counts, Hb levels, Ht, MCV and MCH. Similarly, exposure to lead significantly decreased the mobility, sialic acid content and deformability of ratRBCs. A shortening of erythrocyte survival time was also observed in the rats exposed to lead. It is speculated that decreases in membrane sialic acid content and deformability of RBCs induce a shortening of erythrocyte survival time in anemia caused by lead.
Epidemiological studies suggest that benzotrichloride (BTC) is a human carcino-gen. In the present study, BTC was tested to evaluate its ability to induce lung tumors as a result of systemic exposure. Administration of BTC by gastric intubation, 2.0-0.0315 μl/ mouse (4 doses), twice a week for 25 weeks, in female ICR mice, produced forestomach tumors (squamous cell caricinoma and papilloma), lung tumors (adenocarcinoma and adeno-ma) and tumors of the hematopoietic system (thymic lymphosarcoma and lymphatic leuke-mia) with dose-related response by 18 months. The present and previous studies indicate that the target organs of BTC carcinogenesis in mice are the local tissue which is primarily exposed, and the lung and hematopoietic tissue when BTC is administered systemically.