Metallic mercury in the arterial blood of normal and acatalasemic mice exposed to metallic mercury vapor

Concentration of metallic mercury in the arterial blood was higher in acatalasemic mice after exposure to 3.45 mg/m3 for 10 minutes in comparison with normal mice, whereas concentration of mercuric ion was lower in acatalasemic mice than in normal mice. Thus, the ratio of metallic mercury to total mercury in the arterial blood of acatalasemic mice was 5.86 +/- 3.61%, which was statistically significantly higher than the value (1.36 +/- 0.65%) of corresponding normal mice. The mercury concentration and distribution in the brain and liver of acatalasemic mice were higher than those in normal mice. Data indicate that the concentration of metallic mercury in the arterial blood of acatalasemic mice was higher than that of normal mice and that metallic mercury soluble in lipids is likely transferred to the brain and liver from the blood. Conclusively, metallic mercury in the arterial blood is the biologically active form for transferring mercury from blood to organs.     

Exhalation of metallic mercury by acatalasemic, hypocatalasemic and normal mice exposed to metallic mercury vapor.

In order to elucidate the amounts of metallic mercury exhaled from mice having different amounts of catalase activity, normal, homozygous hypocatalasemic and acatalasemic mice were exposed to radioactive metallic mercury vapor at three levels of concentrations (0.072, 0.144, and 0.297 mg/m3). The timed and cumulative amounts of metallic mercury exhaled from the mice were used to classify them, in the descending order, as being acatalasemic, hypocatalasemic, and normal at the three environmental mercury concentrations. The statistical differences in the mean values among the acatalasemic, hypocatalasemic, and normal mice were calculated by the use of one-way ANOVA and multiple comparison of the mean values by Tukey's method. The mean values of the timed amounts of exhaled metallic mercury were found to be significantly different (P less than 0.05) among the three kinds of mice several hours after exposure, and those of the cumulative amounts of exhaled metallic mercury were in the descending order of acatalasemic, hypocatalasemic and normal mice, and were significantly different among the three types of mice almost over the entire time course. Thus, negative correlation coefficients were obtained between the logarithms of the catalase activity in the lungs and the blood, and the logarithms of the cumulative amounts of exhaled metallic mercury.     

Levels of metallic mercury and mercuric ion in the venous and arterial bloods of normal and acatalasemic mice following exposure to mercury vapor

Levels of metallic mercury and mercuric ion in the arterial and venous bloods of normal and acatalasemic mice exposed to metallic mercury vapor in vitro and in vivo were investigated. Mercury uptake in venous blood from air saturated with mercury vapor with or without hydrogen peroxide in vitro was determined. Level of mercuric ion in venous blood of normal mice was significantly higher than that of acatalasemic mice. By contrast, metallic mercury in venous blood of acatalasemic mice was elevated relative to level in normal mice. Metallic mercury level in red blood cells and plasma was also significantly higher in acatalasemic mice. The ratio of metallic mercury to total mercury (Hg degrees + Hg2+) in the arterial and venous bloods of acatalasemic mice exposed to metallic mercury vapor was increased relative to normal mice. This ratio in red blood cells and plasma in the venous bloods of acatalasemic mice in vivo was also significantly higher than those of normal mice. The significance of metallic mercury in plasma for distribution of mercury in organs is discussed.     

Chiasmata distribution in the normal karyotype of mice

The number of chiasmata per cell and variance of chiasmata numbers were studied, as well as the recombinational interaction between different bivalents in CBA/Lac mice male line. No competition of bivalents for chiasmata was discovered in mice; at the same time, the chiasmata within one arm of the chromosome interfere with each other. The number of chiasmata per bivalent is estimated for each chromosome independently. The number of chiasmata per chromosome is limited both from below (minimum one chiasma independently of its size) and from above (positive interference of chiasmata).     

Pulmonary toxicity caused by acute exposure to mercury vapor is enhanced in metallothionein-null mice.

This study examined the protective role of metallothionein (MT) against pulmonary damage caused by acute exposure to metallic mercury (Hg0) vapor using MT-null and wild-type mice. Both strains of mice were exposed to Hg0 at 6.6 to 7.5 mg/m3 for 4 hr each day for 3 consecutive days. This dosing protocol was lethal to over 60% of MT-null mice but did not kill any wild-type mice. More severe pulmonary damage was found by histopathological observation in MT-null mice than in wild-type mice. MT levels in the lung were elevated in wild-type mice after Hg0 vapor exposure, and gel filtration of the lung cytosol revealed that most of the mercury was associated with MT. In MT-null mice, MT levels were below the limit of detection (0.2 microg/g tissue) for the MT assay even after exposure. After exposure to Hg0 vapor for 3 consecutive days, the pulmonary mercury levels in wild-type mice were significantly higher than in MT-null mice. These findings suggest that MT plays a protective role against the acute pulmonary toxicity of Hg0 vapor.     

Enzymatic oxidation of mercury vapor by erythrocytes

The formation of glutathione radicals, the evolution of nascent oxygen or the peroxidatic reaction with catalase complex I are considered as possible mechanisms for the oxidation of mercury vapor by red blood cells. To select among these, the uptake of atomic mercury by erythrocytes from different species was studied and related to their various activities of catalase (hydrogenperoxide : hydrogen-peroxide oxidoreductase, EC 1.11.1.6) and glutathione peroxidase (glutathione : hydrogen-peroxide oxidoreductase, EC 1.11.1.9). A slow and continuous infusion of diluted H2O2 was used to maintain steady concentrations of complex I. 1% red cell supsensions were found most suitable showing high rates of Hg uptake and yielding still enough cells for subsequent determinations. The results indicate that the oxidation of mercury depends upon the H2O2-generation rate and upon the specific acticity of red-cell catalase. The oxidation occurred in a range of the catalase-H2O2 reaction where the evolution of oxygen could be excluded. Compounds reacting with complex I were shown to be effective inhibitors of the mercury uptake. GSH-peroxidase did not participate in the oxidation but rather, was found to inhibit it by competing with catalase for hydrogen peroxide. These findings support the view that elemental mercury is oxidized in erythrocytes by a peroxidatic reaction with complex I only.     

Mercury concentrations in hair exposed in vitro to mercury vapor

Hair is often used as an index of environmental and industrial exposure to different metals. The interpretation of metal levels in hair is difficult because of the risk of external contamination. The aim of this study was to define the degree of external contamination of hair exposed in vitro to mercury vapor. Specimens of hair were exposed to concentration: 0.026, 0.21, and 2.7 mg Hg/m³ for 2–28 d. Mercury levels in hair increased during 28 d of exposure 2, 3 and 13, times, respectively, when compared to initial values. Mercury levels in hair exposed to the first and second (but not third) concentration of mercury vapor attained a steady state on the 21st d of exposure. The contamination of hair with mercury could not be removed by washing with water, solvent, and detergent. Hair may be used as an index of internal uptake of mercury provided that it was not externally exposed to mercury vapor. In cases of occupational exposure to mercury vapor, hair could become a useful tool for monitoring exposures.     

Treatment of mercury vapor toxicity by combining deferasirox and deferiprone in rats

The hypothesis that combination of deferasirox and deferiprone chelators might be more efficient as combined therapy than single therapy in removing mercury from the body was considered. Male Wistar rats were exposed to mercury vapor for 2 weeks. After mercury administration some abnormal clinical signs such as red staining around the eyes, greenish mottling on the liver, weakness, loss of hair and weight, were observed in animals. Chelators were given orally after mercury vapor application for 2 weeks. Mercury toxicity symptoms in rats decreased after drug administration. After chelation therapy, these rats were anesthetized with ether vapor and immobilized by cervical dislocation and then their heart, liver, kidneys, intestine, spleen and testicles were sampled for determination of mercury and iron concentration. The combined chelation therapy results showed that these chelators are able to remove mercury from the body and toxicity symptoms decreased.     

Lung dosimetry of inhaled radon progeny in mice

Biological response of exposure to radon progeny has long been investigated, but there are only few studies in which absorbed doses in lungs of laboratory animals were estimated. The present study is the first attempt to calculate the doses of inhaled radon progeny for mice. For reference, the doses for rats and humans were also computed with the corresponding models. Lung deposition of particles, their clearance, and energy deposition of alpha particles to sensitive tissues were systematically simulated. Absorbed doses to trachea and bronchi, bronchioles and terminal bronchioles, alveolar-interstitial regions, and whole lung were first provided as a function of monodisperse radon progeny particles with an equilibrium equivalent radon concentration of 1?Bq?m^?3 (equilibrium factor, 0.4 and unattached fraction, 0.01). Based on the results, absorbed doses were then calculated for (1) a reference mine condition and (2) a condition previously used for animal experiments. It was found that the whole lung doses for mice, rats, and humans were 34.8, 20.7, and 10.7?nGy (Bq?m^?3)^?1?h^?1 for the mine condition, respectively, while they were 16.9, 9.9, and 6.5?nGy (Bq?m^?3)^?1?h^?1 for the animal experimental condition. In both cases, the values for mice are about 2 times higher than those for rats, and about 3 times higher than those for humans. Comparison of our data on rats and humans with those published in the literature shows an acceptable agreement, suggesting the validity of the present modeling for mice. In the future, a more sophisticated dosimetric study of inhaled radon progeny in mice would be desirable to demonstrate how anatomical, physiological, and environmental parameters can influence absorbed doses.     

Safety assessment of inhaled xylitol in mice and healthy volunteers

BackgroundXylitol is a 5-carbon sugar that can lower the airway surface salt concentration, thus enhancing innate immunity. We tested the safety and tolerability of aerosolized iso-osmotic xylitol in mice and human volunteers.MethodsThis was a prospective cohort study of C57Bl/6 mice in an animal laboratory and healthy human volunteers at the clinical research center of a university hospital. Mice underwent a baseline methacholine challenge, exposure to either aerosolized saline or xylitol (5% solution) for 150 minutes and then a follow-up methacholine challenge. The saline and xylitol exposures were repeated after eosinophilic airway inflammation was induced by sensitization and inhalational challenge to ovalbumin. Normal human volunteers underwent exposures to aerosolized saline (10 ml) and xylitol, with spirometry performed at baseline and after inhalation of 1, 5, and 10 ml. Serum osmolarity and electrolytes were measured at baseline and after the last exposure. A respiratory symptom questionnaire was administered at baseline, after the last exposure, and five days after exposure. In another group of normal volunteers, bronchoalveolar lavage (BAL) was done 20 minutes and 3 hours after aerosolized xylitol exposure for levels of inflammatory markers.ResultsIn naïve mice, methacholine responsiveness was unchanged after exposures to xylitol compared to inhaled saline (p = 0.49). There was no significant increase in Penh in antigen-challenged mice after xylitol exposure (p = 0.38). There was no change in airway cellular response after xylitol exposure in naïve and antigen-challenged mice. In normal volunteers, there was no change in FEV1 after xylitol exposures compared with baseline as well as normal saline exposure (p = 0.19). Safety laboratory values were also unchanged. The only adverse effect reported was stuffy nose by half of the subjects during the 10 ml xylitol exposure, which promptly resolved after exposure completion. BAL cytokine levels were below the detection limits after xylitol exposure in normal volunteers.ConclusionsInhalation of aerosolized iso-osmotic xylitol was well-tolerated by naïve and atopic mice, and by healthy human volunteers.     

Concentration and distribution of insulin and insulin-like protein in the organs of normal and diabetic mice

Presence of insulin or insulin-like protein has been studied in mouse liver, kidneys, lungs, duodenum, jejunum, submandibular and parotid salivary glands, in femoral, diaphragmal and abdominal wall muscles by means of the immunofluorescent method. In order to understand the role of the extrapancreatic insulin for compensation of the insular insufficiency, corresponding organs have been examined in mice with alloxan diabetes. The immunoreactive insulin is proved to be present only in cells of the granular parts of the salivary tubules of the submandibular and striated ducts of the parotid glands. As demonstrates microfluorometry, a relative amount of insulin in the submandibular gland cells is 1.5 times and in the parotid gland cells--2 times as small as in beta-cells of the pancreatic glands. Under alloxan diabetes insulin content in the salivary gland cells decreases by 1.3-1.9 times (in the beta-cells--by 2.7 times). This may designate that the extrapancreatic insulin (or insulin-like protein) participates in compensation of hypoinsulinemia. In mice with alloxan diabetes, immunoreactivity of insulin is also revealed in hepatocytes.     

Uptake of mercury vapor by wheat: an assimilation model

Using a whole-plant chamber and ²⁰³Hg-labeled mercury, a quantitative study was made of the effect of environmental parameters on the uptake, by wheat (Triticum aestivum), of metallic mercury vapor, an atmospheric pollutant. Factors were examined in relation to their influence on components of the gas-assimilation model, [Formula: see text]