Impaired vitamin B12 metabolic status in healthcare workers occupationally exposed to nitrous oxide.

BACKGROUND: Previous studies demonstrated inactivation of vitamin B12 by nitrous oxide (N(2)O). The intraoperative exposure to N(2)O was shown to induce megaloblastic anaemia and myelopathy in subjects with subclinical vitamin B12 deficiency. In contrast, no data concerning the influence of occupational exposure to N(2)O on vitamin B12 metabolic status are available to date. In the present study, the vitamin B12 status in operating theatre personnel was assessed in relation to the extent of exposure. METHODS: Ninety-five operating theatre nurses with the history of exposure to N(2)O and 90 unexposed counterparts were examined. Vitamin B12 and folic acid were measured by immunoassay. Total homocysteine (tHcy), an indicator of impaired vitamin B12 metabolism, was determined by high performance liquid chromatography. N(2)O concentration was monitored by adsorption gas chromatography and mass spectrometry. RESULTS: No significant differences were found between both groups with respect to haematological parameters and folic acid. However, subjects exposed to N(2)O presented with lower vitamin B12 [372.8 (12.1) vs 436.8 (13.2) pmol litre(-1), P<0.001] and higher tHcy [11.2 (0.5) vs 8.9 (0.5) micromol litre(-1), P=0.006]. The changes in vitamin B12 status were aggravated in subjects exposed to N(2)O in concentrations substantially exceeding occupational exposure limit (180 mg m(-3)) [vitamin B12: 341.9 (17.7) vs 436.8 (13.2) pmol litre(-1), P=0.006; tHcy: 12.9 (0.7) vs 8.9 (0.5) micromol litre(-1), P=0.047]. CONCLUSIONS: Exposure to N(2)O in healthcare workers is associated with alterations of vitamin B12 metabolic status, the extent of which depends on the level of exposure.

Subchronic inhalation toxicity of 1,2,3-trimethylbenzene (hemimellitene) in rats.

Toxic effects of exposure to 1,2,3-trimethylbenzene (hemimellitene) in the condition of subchronic inhalation experiment were examined. Rats were exposed to vapours of hemimellitene at concentrations of 123 mg/m3, 492 mg/m3 and 1230 mg/m3, 6 h/day, 5 days/week for 3 months. After termination of a 3-month inhalation, animals were necropsied. Blood samples were obtained and selected organs were weighed and prepared for histological examinations. Subchronic inhalation exposure to hemimellitene resulted in an overall, low systemic toxicity. There were no changes in body weight gain and food consumption. At a concentration of 1230 mg/m3, the increase in relative liver weight was observed in male rats. It was accompanied by slight increase in sorbitol dehydrogenase activity. The increase in alkaline phosphatase activity was found in females only. Some disturbances in haematological parameters, characterised by the decrease in red blood cells and slight increase in white blood cells, segmented neutrophils and lymphocytes were observed in rats at high exposure concentration of 1230 mg/m3. The pulmonary lesions as well as the increased number of goblet cells and interstitial lung parenchyma infiltration were noted in male and female rats from the highest exposure groups.

Spontaneous spike-wave discharges in rat neocortex and their relation to behaviour.

A certain proportion of laboratory rats of various strains show spontaneous nonconvulsive ECoG seizures in the form of bursts of spike-and-wave discharges (SWD). Since in the majority of behavioural experiments the EEG is not controlled, the experimenter is usually unaware of this fact. The purpose of the present work was to find out whether the SWD trait is related to the rats behavioural performance in selected test situations. The experiment was performed on two groups of male Wistar rats, outbreds, aged six (group 6M, n = 17) and 24 months (group 24M, n = 14). First, in both groups the following forms of behaviour were assessed: (1) seeking water reward in an 8-arm radial maze, (2) exploration of a new object, (3) inhibition of a locomotor response (passive avoidance), and (4) paw-lick response to a thermal stimulus (54.5 degrees C) applied to the feet before and after intermittent footshock. The rats were then implanted with intrabrain electrodes and the level of SWD activity was assessed. Rats of the 24M group, compared with those of the 6M one, showed a significantly shorter exploratory response to a new object and diminished responsiveness to heat. The groups did not differ, however, in passive avoidance and radial maze performance. The analysis of 3-h ECoG sections revealed SWD bursts in 73% and nearly 93% of rats from groups 6M and 24M, respectively. The groups did not differ in the number of bursts or in the total duration of SWD activity. A correlation analysis of pooled data from both groups revealed that the exploration time of a new object was significantly (negatively) correlated with the number of SWD episodes. The total duration of SWD activity, and the number of perseveration errors in the radial maze, was significantly (positively) correlated with the total duration of SWD activity. The results suggest that SWD rats are behaviourally impaired in some test situations.

Sub-chronic inhalation toxicity of 1,2,4-trimethylbenzene (pseudocumene) in rats.

Toxic effects of exposure of 1,2,4-trimethylbenzene (pseudocumene) in the condition of sub-chronic inhalation experiment were examined. Rats were exposed to vapours of pseudocumene at concentrations of 123 mg/m3, 492 mg/m3 and 1230 mg/m3, 6 h/day, 5 days/week for 3 months. After 3 months of inhalation exposure animals were necropsied. Blood samples were obtained and selected organs were weighted and prepared for histological examinations. Sub-chronic inhalation exposure to pseudocumene resulted in an overall low degree of systemic toxicity. There were no changes in body weight gain, food consumption and absolute and relative organ weights. Slightly higher activity of sorbitol dehydrogenase was observed in male rats exposed to all concentrations applied. Some disturbances in hematological parameters characterised by decrease in red and increase in white blood cells were observed in male rats exposed to high concentration of 1230 mg/m3. The pulmonary lesions observed in male and female rats were statistically significant at mid and high concentrations of pseudocumene.

[Irritating effect and dermal toxicity of virkon, a disinfectant widely used in Poland]. / Ocena dzialania drazniacego i toksycznosci dermalnej Virkonu, preparatu dezynfekujacego szeroko stosowanego w Polsce.

The aim of the study was to define the threshold irritating effect of Virkon, a disinfectant widely used in Poland, on the rabbit's skin and eye, and its dermal toxicity in single exposure. The studies were carried out according to the OECD guidelines, modified by Krysiak. A 10% aqueous solution of Virkon in the conditions of multiple open exposure was defined as the threshold concentration evoking small inflammatory reaction. After a single administration of Virkon in aqueous solutions into the rabbit's eye, the value of sensitising effect index was 1.5 for 1% solution of the disinfectant in question which indicates weak inflammatory reaction. The study of dermal toxicity in a single exposure revealed neither animal death nor morphological changes in internal organs which suggests non-cutaneous absorption of Virkon. The present study may provide the basis for assessing dermatological changes in people exposed to disinfectants.

Studies on dermal, ocular and respiratory effects of 4-ethyltoluene in experimental animals.

The toxicity of 4-ethyltoluene to experimental animals was studied after single and repeated exposures. It was found that 4-ethyltoluene can be classified as a very mild skin and eye irritant. Sensory respiratory irritation of 4-ethyltoluene was studied in Balb/C male mice using the plethysmographic method. The concentration at which the respiratory rate decreased to 50% (RD50 value) was determined to be 4216 mg/m3 (2795-5850 mg/m3 for 95% confidence interval). To study repeated-dose inhalation toxicity, male and female outbred Wistar rats were exposed in a dynamic inhalation chamber to 4-ethyltoluene vapours at concentrations of 477 or 2337 mg/m3, 6 h/day, 5 days/week for 4 weeks (20 exposure days). No significant changes were observed in food consumption and body weight gain. Statistically significant, concentration-dependent changes in the number of total cells, as well as of macrophages, polymorphonuclear leucocytes and lymphocytes were found in bronchoalveolar lavage. In the fluid of bronchoalveolar lavage, a significant, concentration-related increase was noted in total protein and mucoproteins and the activity of beta-glucuronidase, gamma-glutamyl transferase, lactate dehydrogenase and acid phosphatase. Histopathology revealed an increased rate of bronchitis and pneumonia and perivascular lymphoid infiltrations in rats exposed to 2337 mg/m3 of 4-ethyltoluene.

[Evaluation of allergic sensitivity to the virkon disinfectant preparation widely used in Poland]. / Ocena dzialania uczulajacego Virkonu preparatu dezynfekujacego, szeroko stosowanego w Polsce.

The aim of the study was to define the sensitising effect of Virkon, a disinfectant widely used in Poland, especially in hospitals. The study was carried out on guinea pigs, using the maximisation test according to Magnusson and Kligman, modified by Krysiak. The assessment of dermal changes presented in the percentage of sensitised animals, being thus far the criterion adopted by Magnusson and Kligman, has been expanded to include our own criteria covering the intensity of reactions of testing samples and the results of eosinophilic and basophilic tests in peripheral blood. Using these parameters and applying pathomorphological examinations it was possible to indicate the difference in the intensity of sensitising effect of Virkon, depending on the concentration used. The results of the study showed that 1% aqueous solution of Virkon is the optimum concentration for monitoring its sensitising effects in people having contact with this substance.

[The evaluation of carcinogenic effect in rats and mice after intraperitoneal administration of refractory ceramic fibers]. / Ocena dzialania kancerogennego u szczurów i myszy po dootrzewnowym wprowadzeniu ogniotrwalych wlókien ceramicznych.

The carcinogenic effect of Langfaser and Thermowool ceramic fibres was assessed in Wistar rats and BALB/C mice. Fibres were administered into the animal peritoneal cavity in doses of 25 and 5 mg, and the animals were left for survival. Langfaser and Thermowool ceramic fibres were found carcinogenic. The carcinogenic properties of Thermowool ceramic fibre can be compared to those of Krokidoit UICC asbestos.

Updating of hygiene standards for carbon disulfide based on health risk assessment.

In 1995 the hygiene occupational standard values of carbon disulfide (CS2) were established in Poland: the maximum allowable concentration, eight-hour time weighted average (MAC-TWA)--18 mg/m3, and the short time exposure level (STEL)--30 mg/m3. For lack of reliable retrospective data on the CS2 exposure levels in the work environment and the dose-response relationship, the following have been taken into account in establishing these values: the nervous and vascular systems are recognized as the main CS2 exposure targets; long-term exposure to CS2 in the work environment, exceeding 30 mg/m3, induces the toxic effect in the nervous and cardiovascular systems; chronic exposure to CS2 at concentration below 20 mg/m3 does not produce adverse effects in the peripheral nervous and vascular systems; coronary heart disease does not occur more frequently in workers exposed to CS2. Aiming at updating the 1995 MAC value for CS2 the authors carried out an analysis of the recent literature data on the relation between exposure levels and health risk. The results of clinical and epidemiological studies published in 1995-1997 did not provide evidence that adverse health effects in the cardiovascular and neurological systems in persons occupationally exposed to CS2 at concentration below 48 mg/m3 is likely to occur. The studies of the harmful effects of low CS2 concentration on the reproductive system have not proved that CS2 affects the embryo and fetus. Moreover, in Poland the employment of women under conditions of CS2 exposure (regardless of concentrations) during pregnancy and breast feeding is banned. Because the latest reliable studies have not indicated that chronic CS2 exposure at the level of 20-48 mg/m3 exerts toxic effect on humans, CS2 concentration of 18 mg/m3 as MAC-TWA and 30 mg/m3 as STEL, adopted in 1995, need not to be updated.

[Evaluation of the carcinogenic effect of ceramic fibers in experiments on rats and mice]. / Ocena dzialania nowotworowego wlókien ceramicznych--w doswiadczeniu na szczurach i myszach.

The carcinogenic effect of Kaowoll raw and thermally used ceramic fibres was assessed in experiments on rats and mice. The fibers were applied intraperitoneally in doses by 25 and 5 mg, and the animals were observed over their life-span. It was found that Kaowoll fibers were carcinogenic and that high temperature did not change these properties.

A subchronic toxicity study of Rokanol B-2 in rats.

The toxicity of Rokanol B-2 was assessed following its administration to rats via oral gavage. A preliminary study of acute toxicity was performed to determine suitable dosing regimen/dose levels for future repeated-dose toxicity studies. For this purpose rats (15 males and 7 females) received single doses of 2,000, 1,500, 1,000 or 500 mg/kg and were killed after 2 or 14 days. No deaths occurred during the observation time. Dose-related irritation to the stomach mucosa was found. For the subchronic toxicity assessment, Rokanol B-2 was administered at daily doses of 8, 40 or 200 mg/kg to 59 male and 56 female Wistar rats by oral gavage, 5 days per week for 90 days. An interim experiment was performed after 28 days of dosing. Five animals/sex/group were terminated and necropsied. Blood samples for clinical chemistry and haematology were obtained and lungs, heart, adrenals, kidneys, liver, spleen, stomach, intestine, testes (males), uterus and ovaries (females) were weighed and prepared for histopathological examination. After 90 days of dosing all remaining animals were killed and necropsied. Blood samples were taken for evaluation of haematology and clinical chemistry, and selected organs (same as above) prepared for subsequent histological examination. In the high-dose group (200 mg/kg/day) a statistically significant reduction in body weight gain and food consumption, an increased weight of the liver in the males and disturbances in haematological parameters in the females were observed. Ulcerations of the mucous membrane of the stomach and hyperkeratosis, and in a few cases, pseudopapillomatous epithelial proliferation of foregaster and exudate in the submucosa of the stomach were noted. In the mid-dose group (40 mg/kg/day) some disturbances in hematological parameters in females and histopathological changes in rats of both sexes similar, but to a lesser degree, to changes observed in high-dose animals were indicated. In the low-dose group (8 mg/kg/day) no significant treatment-related effects were observed. The results of this study indicate that Rokanol B-2 possessed an overall low degree of systemic toxicity when administered orally to rats for 90 days. The NOAEL, observed in this study, was estimated as 8 mg/kg/day.

Experimental carcinogenicity and mutagenicity of non-asbestos natural fibres--preliminary report.

The aim of this investigation was to quantify the carcinogenic and mutagenic activity of antigorite occurring in the form of admixtures in different mineral raw materials (serpentinite, magnesite, dolomite and nickel ore). The carcinogenicity of dusts was evaluated after intraperitoneal injections of 5 mg (mice) or 20 mg (rats) of dust suspended in saline. A pathomorphological examination was performed in all the dead animals. For two raw materials--serpentinite and nickel ore--their mutagenic potency was investigated (SCE test was used in this study). Results obtained in the experiments on animals (rats and mice) showed that the biological aggressiveness of the mineral raw materials tested was associated with the content of antigorite fibres. Particularly the frequency of mesothelioma (5-85%) was related to the number of antigorite fibres longer than 5 microns. Both of the investigated raw materials (serpentinite and nickel ore) were mutagenic in the SCE test.

Acute toxicity of 2-butyne-1,4-diol in laboratory animals.

Acute toxicity of 2-butyne-1,4-diol (BYD) was evaluated in laboratory animals. The evaluation involved acute oral and dermal toxicity in rats, dermal and ocular irritation in rabbits and skin sensitization in guinea pigs. The oral LD50 values for BYD were 132 mg kg-1 in male rats and 176 mg kg-1 in female rats. Post-mortem histology showed severe damage in lungs, liver and kidneys. In surviving rats, moderate to severe degenerative changes were observed in the liver but only mild lesions in the kidneys. In acute dermal toxicity studies the test chemical was applied either as a solid substance or as 40% aqueous solution at a dose of 5 g kg-1 for 24 h. Within 48 h of application of the diluted test material, half of the rats died. Liver and kidneys were the primary targets and different stages of degeneration, including necrosis, were observed. No deaths occurred after application of the solid substance. In rabbits, BYD was slightly irritant to skin and eyes. No allergic contact dermatitis was observed in guinea pigs.

Subacute oral toxicity of 2-butyne-1,4-diol in rats.

2-Butyne-1,4-diol was given to male and female Wistar Imp:DAK rats by oral gavage for 28 consecutive days in daily doses of 1, 10 or 50 mg kg-1 day-1. After 28 days all animals were necropsied. Blood samples were obtained and selected organs were weighed and prepared for histological examination. Treatment-related effects in the high-dose group consisted of: fatal cases in both sexes; depressed body weight gain in males; increase of absolute and/or relative weights of liver and kidneys in both sexes; decreased red blood cell count, haematocrit value and haemoglobin concentration in female rats and elevated reticulocyte count and leukocyte count in both sexes; increased total serum protein content in females, elevated glucose concentration in males and higher activity of sorbitol dehydrogenase in both sexes; and histopathological evidence of hepatotoxicity and nephrotoxicity in decedents, and hepatic and splenic changes in survivors. Minor hepatic, splenic and erythrocytic changes were also found in some females given the middle dose. The dose of 1 mg kg-1 day-1 was considered to be the no-observed-effect level (NOEL), and 10 mg kg-1 day-1 the lowest-observed-effect level (LOEL).

[Asbestos substitutes and their biological effects. 3. Carcinogenic effects of synthetic amphiboles in animal experiments]. / Zamienniki azbestu i ich dzialanie biologiczne. 3. Dzialanie kancerogenne amfiboli syntetycznych oceniane w doswiadczeniu na zwierzetach.

This work presents the results of the test performed on rats to evaluate the carcinogenic effect of 4 synthetic amphiboles compared to that of the natural amphibole--crocidolite. The dose of the magnesium amphibole (Na2Mg6Si8(OH)2) administered to the animals contained 240 x 10(6) respirable fibres; the corresponding value for the nickel amphibole (Na2Ni6Si8O22(OH)2) was 339 x 10(6), for the cobalt amphibole (Na2Co6Si8O22(OH)2)--1000 x 16(6) for the geranium amphibole (Na2Mg6Ge8(OH)2)--250 x 10(6), and of the natural crocidolite amphibole (Na2Fe2Fe3Si8O22(OH)2) x 380 x 10(6) respirable fibres. The control animals (rats) received physiological NaCl solution. The number of peritoneal mesotheliomas following single intraperitoneal administration of 20 mg of the dust was adapted to be the measure of the carcinogenic activity of the dust. 3 synthetic (magnesium, cobalt and nickel) amphiboles and crocidolite caused development of malignant peritoneal mesothelioma in 11.1% to 71% rats. The results show that there is a relationship between the chemical composition of the synthetic amphiboles and their carcinogenic effect. Out of 4 investigated synthetic amphiboles, the magnesium amphibole, which contained magnesium and silicon, displayed most severe carcinogenic effect. The synthetic amphiboles containing either silicon and cobalt or silicon and nickel displayed 8.3 and 6.2 times weaker ability to induce peritoneal mesothelioma.

Acute toxicity of 1,4-butanediol in laboratory animals.

Acute toxicity of 1,4-butanediol (BAD) was evaluated in laboratory animals. The evaluation involved acute oral and dermal toxicity in rats, dermal and ocular irritation in rabbits, and skin sensitization in guinea pigs. The oral LD50 values for BAD were 1.83 g/kg and 2.00 g/kg, respectively for male and female rats. The histopathological changes were observed in the liver and kidneys. No mortality was observed in female rats after dermal application of BAD at a dose of 5 g/kg. The histopathological lesions were comparable to those observed in rats after oral gavage. BAD was slightly irritant to the skin and eye of rabbits. No allergic contact dermatitis was observed in guinea pigs.

Subacute oral toxicity of 1,4-butanediol in rats.

1,4-Butanediol (BAD) was administered to male and female Wistar Imp:DAK rats by oral gavage for 28 consecutive days. Treated rats received BAD at daily doses of 5, 50 or 500 mg/kg/day. After 28 days all animals were necropsied. Blood samples were obtained and selected organs were weighed and prepared for histological examination. Subacute oral administration of BAD resulted in an overall low degree of systemic toxicity. There were no changes in body weight, food consumption, and absolute and relative organ weights. Slightly higher activities of sorbitol dehydrogenase and alanine aminotransferase were observed in male rats given BAD at the highest dose of 500 mg/kg/day. Some disturbances in hematological parameters, characterized by macrocytosis and thrombocytopenia were observed in treated rats. Mild to moderate inflammation of the liver, characterized by proliferation of bile ducts and periportal infiltrations with fibroblasts and mononuclear cells, were found in treated animals. A statistically significant difference for histopathological changes was found in animals treated with BAD at the dose of 500 mg/kg/day only in the case where both sexes were jointly taken for comparison.

Computer image analysis of toxic fatty degeneration in rat liver.

Fatty degeneration of the liver is one of the most frequently observed pathological changes in the experimental estimation of the toxicity of chemical compounds. The intensity of this kind of damage is most often detected by means of a generally accepted scale of points, whereas the classification is performed according to the subjective "feeling" of the pathologist. In modern pathological diagnostics, computer analysis of images is used to perform an objective estimation of the degree of damage to various organs. In order to check the usefulness of this kind of method, comparative biochemical and morphometrical studies were undertaken in trichloroethylene (TRI)-induced fatty degeneration of the liver. TRI was administered to rats intragastrically, in single doses: 1/2; 1/3; 1/4; 1/6 and 1/18 DL50. 24 hours after the administration, the animals were sacrificed. The content of triglycerides in the liver was determined according to Folch et al. (1956). Simple lipids in the histochemical samples were detected by means of staining with a lipotropic, Fat Red 7B. The area of fatty degeneration was estimated in the microscopic samples by the use of an automatic image analyser IBAS 2000 (Kontron). The morphometrical data concerning the area of fatty degeneration in the liver amplified a high degree of correlation with the content of triglycerides (r = 0.89) and the dose of TRI (r = 0.96). The degree of correlation between the biochemical data and the dose of TRI was 0.88. The morphometrical studies performed have proved to be of great use in estimating the degree of fatty degeneration in the liver. This method enables precise, quantitative measuring of this sort of liver damage in the material prepared for routine histopathological analysis. It requires, however, the application of a specialized device for quantitative image analysis.

[Morphometric analysis of the rat lung after exposure to xylene vapors]. / Ocena morfometryczna pluc szczurów narazonych na pary ksylenu.

Pathomorphologic examinations of laboratory animals' respiratory system, carried out within evaluation of chemical substances toxicity, pose many diagnostic obstacles. Usually, pulmonary pathologies are evaluated based on arbitrarily adopted criteria and subjective "feelings" of a pathologist. To objectivize the results of pathomorphologic studies and evaluation of the usefulness of quantitative morphological techniques, morphometric tests of the lungs of rats exposed to m-xylene vapours of 4000 mg/m3 concentration for 1 and 3 months were carried out. Lungs were expanded by intratracheal insufflation of 10% formalin under controlled pressure of 23-25 cm water column. Using the stereological point--counting method, in microscope preparations evaluated was the relative volume of: a) normal and atelectatic lung parenchyma, b) peribronchial lymphatic tissue, c) interstitial inflammatory infiltrations. Pathological changes were presented in form of numbers; findings were analysed statistically with non-parametric tests of Krushal-Wallis and Mann-Whitney. The morphometric techniques demonstrated significant differences in the lungs of xylene-exposed rats, varying with the duration of exposure and applied dose, as compared to control animals.