Methanol in urine as a biological indicator of occupational exposure to methanol vapor

Summary The exposure-excretion relationship and possible health effects of exposure to methanol vapor were studied in 33 exposed workers during the second half of 2 working weeks. Urinary methanol concentrations were also determined in 91 nonexposed subjects. The geometric mean value for methanol in urine samples from the latter was < 2 mg/1 (95% upper limit of normal, < 5 mg/l) when log-normal distribution was assumed. Among the exposed workers, the methanol level in urine samples collected prior to the work shift exceeded the 95% upper limit of normal. The time-weighted average intensity of exposure to methanol vapor was measured using personal sampling devices (in which water severed as an absorbent) in 48 cases of methanol exposure (i.e., 2 of the 33 exposed workers failed to provide urine samples, whereas 17 subjects were examined twice). Methanol concentrations in urine were determined in samples collected at the end of the shift from the 48 exposed cases as well as from 30 nonexposed controls. There was a significant correlation between the exposure to methanol vapor at concentrations of up to 5,500 ppm and the levels of methanol measured in the shift-end urine samples. The calculation indicated that a mean level of 42 mg methanol/l urine (95% confidence range, 26–60 mg/kg) was excreted in the shift-end urine sample following 8 h exposure to methanol at 200 ppm (the current occupational exposure limit). Dimmed vision and nasal irritation were among the most frequent symptoms complained during work. Three cases showing clinical signs of borderline significance were identified.     

Urinary methylhippuric acid isomer levels after occupational exposure to a xylene mixture

Summary The quantitative relationship between exposure to xylene vapor and urinary excretion of methylhippuric acid (MHA) isomers were studied in the second half of a working week. The participants in the study were 121 male workers engaged in dip-coating of metal parts who were predominantly exposed to three xylene isomers. The intensity of exposure measured by diffusive sampling during an 8-h shift was such that the geometric mean vapor concentration was 3.8 ppm for xylenes (0.8 ppm for o-xylene, 2.1 ppm for m-xylene, and 0.9 ppm for p-xylene), 0.8 ppm for toluene, and 0.9 ppm for ethylbenzene. Urine samples were collected at the end of the shift and analyzed for metabolities by HPLC. The statistical analysis showed that there is a linear relationship between the intensity of exposure to xylenes and the concentration of MHA in urine, that the regression line passes very close to the origin, and that the increment in observed (i.e., noncorrected) MHA concentrations as a function of increasing xylene concentration was 17.8 mg × 1^–1 ppm^–1. Further examination on the basis on individual xylene isomers showed that the slopes of the regression lines for o- and m-isomers were similar (i.e., 17.1 and 16.6 mg l^–1 ppm^–1, respectively), whereas that for p-xylene was larger (21.3 mg l^–1 ppm^–1).     

A sensitive enzyme-linked immunosorbent assay of ochratoxin A based on monoclonal antibodies

We prepared seven monoclonal antibodies (mAbs, OTA.1, 2, 3, 4, 5, 6 and 7) which were reacted with ochratoxin A (OTA), and have developed a specific and highly sensitive enzyme-linked immunosorbent assay (ELISA) for detection of OTA. The mAbs, OTA.1, 3, 4, 5 and 7, specifically reacted with OTA but much less with its analogs, ochratoxin B (OTB, about 1% of OTA) and ochratoxin alpha (OT alpha, less than 0.1% of OTA). One of the mAbs, OTA.2, equally reacted with OTA and OTB but hardly at all with (4R)-4-hydroxyochratoxin A or OT alpha (less than 0.1% of OTA). All of the mAbs reacted with ochratoxin C. None of the mAbs reacted with coumarin, 4-hydroxycoumarin or L-beta-phenylalanine. In the competitive ELISA with OTA.1 and OTA.7, the lowest detectable amount of standard OTA in solution was 50 pg/ml (2.5 pg per assay). This assay was applied for the quantitation of OTA added to chicken meat, wheat flour, porcine plasma and bovine serum. With minimal sample preparation, reliable and reproducible determinations were possible when concentrations of OTA were higher than 0.1-1 ng/g.     

Enhanced expression of heat shock protein 47 in rat model of peritoneal fibrosis.

OBJECTIVE: Peritoneal fibrosis is one of the serious complications of continuous ambulatory peritoneal dialysis therapy and is characterized by collagen accumulation. Heat shock protein 47 (HSP-47) is a collagen-specific molecular chaperon and is closely associated with collagen synthesis; however, the involvement of HSP-47 in the progression of peritoneal fibrosis is not fully understood. DESIGN: To examine the serial pathological alterations caused by peritoneal fibrosis, we made an experimental model of peritoneal fibrosis by daily intraperitoneal injection of chlorhexidine gluconate (CG) in rats for 28 days and examined the expression of HSP-47 together with that of types I and III collagen, alpha-smooth muscle actin (aSMA), and ED-1 (a marker for macrophages) using immunohistochemistry. Rats treated with saline containing 15% ethanol were used as the control group. RESULTS: In the control group, the peritoneal tissue was slightly thickened and HSP-47 was expressed in the peritoneum at day 28. In the CG group, the peritoneal tissue serially became thickened and fibrotic. The expression of HSP-47 was evident in mesothelial cells and submesothelial connective tissue after day 7 of treatment with CG, and increased thereafter. The expression of types I and III collagen and aSMA was proportionally strengthened during our experiments. ED-1-positive cells were present in thickened areas with abundant proliferation of collagen fiber. The number of cells positive for ED-1 increased gradually and reached a maximum at day 21. CONCLUSION: Our results indicate that, in a rat experimental model of peritoneal fibrosis, the expression of HSP-47 is associated with the progression of peritoneal fibrosis.     

Electron microscopic study on the development of the chicken ultimobranchial glands, with special reference to innervation of C cells

The development of chicken ultimobranchial glands was studied by electron microscopy. As early as at 8 days of incubation, some cells contained a few secretory granules, although most of the ultimobranchial cells were undifferentiated. Single axons or small bundles of axons were occasionally detected in close contact with the ultimobranchial cells. Subsequently, immature C cells gradually increased in number with age. At 12 days of incubation, the developing C cells, which contained some secretory granules from 60 to 200 nm in diameter, occupied the greater part of the gland. The cells were oval, elongated or irregular in shape and frequently gave rise to long cytoplasmic processes that touched other C cells. Numerous axons enveloped with Schwann cell processes occurred in close vicinity to C cells. At 14 days of incubation, the cytoplasmic processes of C cells reached their maximum number and size. Desmosome-like membrane specialization was observed at the contact between the processes and cell bodies of other C cells, while numerous microtubules were arranged in parallel to the long axes of the processes, and secretory granules were distributed along them. Thus, the C cells at these stages seem to regulate other homologous cells by direct contact. Axon terminals, which contained small, clear and large, densecored vesicles, were first found in direct contact with the surface of C cells in 14-day-old embryos. Subsequently, the cytoplasmic processes of C cells progressively decreased, while nerve fibers continued to increase in the ultimobranchial glands. At the late stages of embryonic development, many C cells displayed an oval outline and increased number and size of secretory granules. At hatching, many C cells were filled with large secretory granules ranging from 200 to 700 nm in diameter (average 300 nm). Some cells were still elongated or irregular in shape and contained small secretory granules, 60–200 nm in diameter.