Postural sway frequency analysis in workers exposed to n-hexane, xylene, and toluene: assessment of subclinical cerebellar dysfunction.

To clarify the effects of organic solvents on the postural balance system, 29 male sandal, shoe, and leather factory workers exposed to n-hexane, xylene, and toluene (solvent workers) were examined by computerized static posturography with sway frequency analysis. Concentrations of metabolites of solvents in urine samples taken from the workers in the morning before work ranged from 0.41 to 3.06 (mean, 1.20) mg/g creatinine (Cn) for 2,5-hexanedione, from 0.10 to 0.43 (mean, 0.19) g/g Cn for methylhippuric acid, and from 0.05 to 2.53 (mean, 0.37) g/g Cn for hippuric acid; estimated concentrations of n-hexane in workplace air ranged from 13 to 100 (mean, 40) ppm. Control subjects were 22 healthy males without exposure to solvents. With eyes open, postural sway with a frequency of 2-4 Hz in solvent workers was significantly larger than that in controls in the anteroposterior direction. With eyes closed, sway with a frequency of 0-1 Hz was significantly larger in solvent workers in the mediolateral and anteroposterior directions. Results of multiple regression analysis showed that with eyes open the 1- to 2-Hz and 2- to 4-Hz sways were related positively to 2,5-hexanedione and inversely with methylhippuric acid. The pattern of changes suggests that the vestibulocerebellar and spinocerebellar afferent systems are asymptomatically affected by n-hexane; the effect of n-hexane on the vestibulocerebellar system is possibly inhibited by xylene.

Concentrations of trichloroethylene and its metabolites in blood and urine after acute poisoning by ingestion.

A 58-year-old man fell into a trichloroethylene reservoir bath head first, during a maintenance degreasing bath and accidentally ingested the solvent. Although he showed deep coma, chemical burns and pneumonia on admission, these symptoms gradually subsided. The concentrations of trichloroethylene (TRI) and its metabolites, trichloroethanol (TCE) and trichloroacetic acid (TCA) in blood and urine were measured during hospitalization. Eight hours after the accident, the concentrations of TRI and its metabolites in serum were 31.4 micrograms/ml TRI, 16.5 micrograms/ml TCE and 79.5 micrograms/ml TCA. The serum TRI concentration decreased to 4.3 micrograms/ml on the following day. Elimination of TCE and TCA from serum occurred biphasically, the estimated half-lives of each metabolites being about 52.6 and 50.4 h in an initial fast phase and 268.3 and 277.2 h in a subsequent slow phase, respectively. Urinary TRI excretion persisted for the first 2 days. The urinary TCE and TCA excretions were longer than that of TRI with a biphasic decrease and the total amount of TCE excreted during the first 2 days was about two times that of TCA. The half-life of urinary TCE excretion (t1/2 25.7 h) was shorter than that of TCA (t1/2 52.1 h) in the fast phase but did no difference during the slow phase, with each half-time being about 166.3 h. The kinetics of TRI metabolites in blood and urine in this case were in slight agreement with the results following inhalation exposure previously reported in the literature.

Changes in autonomic function as determined by ECG R-R interval variability in sandal, shoe and leather workers exposed to n-hexane, xylene and toluene.

To clarify if autonomic nervous system effects might be associated with exposure to organic solvents, 30 sandal, shoe and leather workers exposed to n-hexane, xylene, and toluene, and 25 unexposed controls were examined using the coefficient of variation in electrocardiographic R-R intervals (CVRR), combined with the distribution of nerve conduction velocities (DCV). The C-CVRSA and C-CVMWSA (two component CVs of the CVRR reflecting parasympathetic and sympathetic activities, respectively) were also computed from component spectral powers using autoregressive spectral and component analyses. Concentrations of the metabolites of the solvents in urine samples taken in the morning before work were 0-3.18 (mean 1.39) mg/l for 2,5-hexanedione, 0.10-0.43 (mean 0.19) g/g creatinine (Cn) for methylhippuric acid, and 0.05-2.53 (mean 0.41) g/g Cn for hippuric acid. In the solvent workers, the CVRR and C-CVRSA were reduced significantly when compared with the unexposed controls. The faster velocities of the DCV as well as the sensory median nerve conduction velocity (SCV) were significantly slowed in the solvent-exposed workers. The SCV was significantly correlated with the CVRR and C-CVMWSA among the solvent workers. These data suggest that chronic exposure to some organic solvents may affect cardiac autonomic function (mainly, parasympathetic activity) in addition to faster myelinated fibers of the peripheral nerves. However, the absence of significant dose-effect relations among the solvent workers makes it difficult to definitively attribute the differences to specific solvent exposures.

A three-dimensional reconstructive study of the layer structure of the human vocal cord.

The purpose of this investigation was to clarify the detailed histological structure of the human larynx and to clarify the cause of adaptation in high-frequency vibrations using three-dimensional histological reconstructions of human true vocal cords. In a first series of studies, 54 intact adult larynges were obtained from 398 human cavaders with known histories. Four of these laryngeal specimens were fixed in 10% formalin. Three of these were decalcified and embedded in paraffin and the other in Technovit-7100. The layer structure of each larynx was investigated with a three-dimensional reconstruction method using a personal computer. Results demonstrated that the elastic fiber layer in the superior surface of the vocal cord was wider than that in the inferior surface. The collagen fiber layer extends from the anterior commissure in a posterior direction. The elastic fiber layer connected both the anterior and the posterior macula flava, while the collagen fiber layer connected the thyroid cartilage and the anterior macula flava.

Total actual speaking time in infants and children with otitis media with effusion.

For the purpose of supporting the premise that remarkable improvements in the child's attitude and performance rendered by improving the hearing impairment after aspiration of effusion and insertion of ventilating tubes in infants and children causes the increase in actual speaking time, an apparatus for measuring the time of vibration of the vocal cords was newly devised. Using this instrument, the duration of speaking time of children with otitis media with effusion was measured preoperatively and postoperatively. Preoperative and postoperative mean speaking times (speaking minutes/measured hours) were found to be 8 min 24 s per hour and 10 min per hour, respectively (number of patients: 30). These variable means were significant when examined by a Student's t-test. Pre- and postoperative speaking times showed no significant differences (10 min 24 s preoperatively and 10 min 54 s postoperatively) in the control group for surgery, consisting of 5 children having adenoidectomy and/or tonsillectomy.

Measurement of young children's total actual speaking time by a newly devised accumulator as an assessment of otitis media with effusion.

Aspiration of effusion and insertion of ventilating tubes in children with persistent effusion are effective ways of treating otitis media with effusion. In consequence, an increase in actual speaking time rendered by improving the hearing impairment must surely enrich the lives of children afflicted with this disease. To assess the increase in speaking time following aspiration of effusion and insertion of ventilating tubes, we devised a speech accumulator (RYU et al., 1983) which records the vibration time of the vocal cords by a small contact microphone attached to the neck. Total actual speaking time was measured with this device in children with effusion, and preoperative and postoperative speaking times were compared. Furthermore, an increase in actual speaking time invariably coincided with gain of hearing by middle ear ventilation. Children in whom insertion of the tube and adenoidectomy and/or tonsillectomy were performed were recruited for the study. The placebo group for surgery was made up of children selected at random who underwent adenoidectomy and/or tonsillectomy and suffered no hearing impairment, hence, there was no insertion of the tube. There was no significant difference between preoperative and postoperative total speaking times in patients of the placebo group.