Application of atomic force microscopy to visualization of DNA, chromatin, and chromosomes.

The scanning force microscope (SFM, also called the atomic force microscope, AFM) provides a new and powerful method for visualization and manipulation of biological samples. Its high precision and sensitivity allow the investigator to interrogate samples at very high spatial resolution and simultaneously accumulate a variety of data types, including topography, viscoelasticity, chemical properties, and local friction. We provide here a brief review of the literature describing the current state of the art in the application of SFM to the study of DNA, chromatin and chromosomes, and some examples from this laboratory. Suggestions for future directions of this technology are also presented.

A non-traditional approach to risk assessment of respiratory exposure to outdoor air pollutants.

The aim of this study was to verify a non-traditional assessment of respiratory exposure to outdoor air pollutants in industrial areas. The technique involved environmental biological monitoring' using domestic rabbits in the neighborhood of a mercury-producing plant. Rabbits were exposed whole-body to mercury emissions for 6 months in special cages near the plant. Control rabbits were kept using the same schedule outside the polluted area. Potential toxicity was assessed by: (a) measurement of Hg-accumulation in lungs and other body tissues by atomic absorption spectroscopy (AAS); (b) scanning electron microscopy (SEM) of the tracheal surface; and (c) measurement of toxic effects on pulmonary alveolar macrophages (PAM) by a rossette assay (Fc immunoglobulin binding). We found increased Hg concentrations in the lungs, kidneys, liver, heart, brain and bone; changes in the mucosal relief of the trachea, and depression of PAM Fc receptor (FcR) activity to IgG. A 6-month chamber exposure of Wistar rats to the aerosol created from solid particles of the mercury-producing plant revealed the increase of Hg-content in the same body tissues except the brain, and, less intense morphologic changes on the tracheal relief. Biomonitoring using environmental exposure of domestic rabbits might be useful in screening for possible health hazards to the respiratory system from complex outdoor aerosols.

Issues related to dust aerosols in the magnesite industry. II. Environmental exposure.

Magnesite waste containing largely magnesium oxide (MgO) and a mixture of other metals forms aerosols with a considerable portion of respirable particles when released into the atmosphere. Several animal species (domestic rabbits, Wistar rats, cattle) were used to biologically monitor the accumulation and effects of inhaled magnesite aerosol in two actual locations of the magnesite industry. The study revealed the biological accumulation of magnesium, iron and other metals in the bodies of exposed animals (and F1 animals) as well as specific lesions on tracheal relief, morphological changes in organ microstructure (especially in the lungs, spleen, liver and myocardium), alternations in the reproductive capacity of females, distorted Mg:Ca:P ratio as well as changes in the immune profile. The findings of biological monitoring of animals are consistent with the conclusions of epidemiological studies.

Issues related to dust aerosols in the magnesite industry. I. Chamber exposure.

The present paper is an overview of the experimental research into the effects of flue magnesite dust in the magnesite industry in which the raw material (magnesite) is processed into refractory magnesite clinker. The issues related to dust are divided into two problem areas: a) dust aerosol arising in the process of ore mining and consisting largely of magnesite (MgCO3) and b) dust aerosol originating during ore baking in rotatory furnaces and made up mostly of MgO. Thus, larger groups of people become exposed to these aerosols as a result of solid particles escaping into the atmosphere than in the case of occupational exposure. Experimental research carried out on laboratory animals after chamber exposure provided findings on the deposition, retention and elimination of magnesite dust, on impaired balance between magnesium and calcium leading to damage of biological membranes, on how the immune profile or reproduction and embryogenesis is impacted as well as on the possible interaction with sodium salicylate as a result of an impaired acid base balance. These findings are followed up by evidence produced in the course of biological monitoring (Part II).

[Incidence of maxillary orthopaedic anomalies in adolescents]. / Výskyt cel'ustnoortopedických anomálií dorastu.

Within the framework of an epidemiological survey of the state of dentition the authors examined some 4% of adolescents in the East Slovakian region (aged 15-18 years). The authors recorded the following values according to Angle's classification: A II/1-14.3% A II/2-7.5% A III-3.1%. Abnormal position of the frontal teeth: retrusion-8.2% protrusion-12.2% cramming-19.7%. Incidence of malocclusion: deep occlusion-23.8% labial occlusion-4.4% open occlusion-5.8% crossed occlusion-7.3%. Diastema with normal position of the frontal teeth-7.9%. The authors evaluate the total incidence of maxillary orthopaedic defects-70.2%-as very high.

Bioaccumulation of metals from nickel smelter waste in P and F1 generations of exposed animals. I. Dynamics of metal distribution in the organs and AM activity.

A group of female Chinchilla rabbits was exposed respiratory to metal aerosol originating from dumped wastes of a nickel smelter. The experiment was carried out in a biomonitoring station situated 4 km away from the dump in the direction of prevailing winds. Metals (Fe, Cr, Ni) introduced by inhaled waste particles were found in the increased amount in the body organs of exposed (P and F1) animals. Following a 3-months exposure of female rabbits (P), the elevated level of Cr in liver and kidneys was found, and after 6-month exposure also in the heart and thigh muscles. The Ni content proved to be increased in the lungs, heart and thigh muscles following 3-month period and in the liver after the 6-month exposure. Concerning the Fe content, it was already elevated in all the organs investigated except the lungs after 3-month exposure. The alveolar macrophage (AM) count was increased significantly in the exposed female rabbits (P) only after 6 months (P less than 0.05) and rose continually till the end of 9-month exposure (P less than 0.01). The enzyme activity of lysosomes was enhanced after 9-month exposure. In F1 rabbits 6 weeks of age elevated levels of chromium were found in the liver, kidneys, heart and thigh muscles. The Fe content was increased in the liver and thigh muscle, while the Ni content was enhanced only in the brain. The increased mucus secretion was observed on the tracheal mucous relief of F1 rabbits in response to the noxious effect of needle-shaped metal particles using an electron scanning microscope, despite the short duration (6 weeks) of postnatal exposure. The reported findings emphasize the effects of metal particles originating from the waste of a nickel smelter in an environment where the mean value of the dust fallout was only 4 g.m-2.30 days-1.

Bioaccumulation of metals from a nickel smelter waste in P and F1 generations of exposed animals. II. Modulation of immune processes.

A group of female Chinchilla rabbits was exposed through inhalation to the metal aerosol derived from dumped waste of a nickel smelter. The experiments were carried out in a field exposure station. Increased levels of tissue immune complexes were found in the myocardium and lungs of P females, whereas F1 rabbits (exposed both prenatally and 6 weeks postnatally) from the same group of P females had significantly elevated serum circulating immune complexes as compared to controls. In P rabbits, nonspecific serum tumoricidal activity was increased by 8.2%, while in F1 animals the increase was by 14%. Transplantation immunity was examined in a group of inbred Lewis rats following the transplantation of a skin allograft from the ear of inbred Berlin-Druckrey rats. The mean time of allograft survival in animals following i.v. administration metal dust suspension 2 days prior to transplantation, was prolonged as compared to controls. On day 22 after allograft transplantation, lactate dehydrogenase activity was found to be reduced in peripheral lymphocytes, and the liver and spleen weight proved to be diminished. These findings suggest a modulating effect of the metal dust from a nickel smelter regarding nonspecific serum tumoricidal activity and transplantation immunity as well as immune complex formation.

Biomonitoring of environmental pollution hazards from a nickel smelter waste dump.

Longterm field exposure study was carried out on 10 rabbits placed for 6 months in a bioindication station located about 3 km downwind of a disposal site of nickel smelter waste dump. As revealed by the method of atomic absorption spectrophotometry, all of these animals showed elevated nickel and chromium levels in their body organs and hair. These findings were paralleled by histologic abnormalities in the lungs and liver tissues. Average dustfall values at the site of exposure did not exceed 5.5 g X m-2 X 30 d-1 during the period of observation. Dustfall deposits in this location contained nickel and chromium in amounts that were higher than in control locality. Analogous experiments on Wistar rats were carried out in a laboratory exposure chamber (exposure 4 h/day, 5 days/week, for a period of 6 months). After exposures to 50 mg X m-3 of metallic dust, lung parenchyma of rats was characterized by the presence of dust particles in various phases of phagocytosis as well as the presence of badly damaged or disintegrated alveolar macrophage cells, which pointed to metallic aerosol toxicity for biomembranes. The technique of air pollution biomonitoring on animals, correlated with the data on ambient air concentrations of the suspended particulate matter and its content of trace metals, appears to be a well suitable tool in establishing the potential air pollution hazards to the exposed populations living in the area of concern.

Modulation of peripheral lymphocyte and alveolar macrophage activity by magnesite emissions.

Modulation of alveolar macrophage and peripheral lymphocyte activities in rats exposed to magnesite emissions was tested under field and laboratory conditions. The field exposure test were conducted in a locality near a magnesite ore processing plant, the time observation was 18 weeks. The laboratory exposure tests were performed in an inhalation chamber at a constant magnesite dust aerosol concentration of 50 mg . m-3; the animals were exposed 4 hours a day, 5 days a week for a period of 70 days. Eighteen weeks of exposure to magnesium-polluted ambient air was found to increase the number of alveolar macrophages, to stimulate acid phosphatase activity in these cells, and to enhance activity of peripheral B lymphocytes to form EAC rosettes. The inhalation chamber experiments, evaluated after 46 and 70 days of exposure, resulted in an enhanced acid phosphatase activity of alveolar macrophages, enhanced lactate dehydrogenase activity of peripheral lymphocytes and in an increased percentage of B lymphocytes in blood, depending on exposure time. The activation of peripheral lymphocytes and alveolar macrophages observed in rats exposed under field and laboratory (here in dependence on exposure time) conditions clearly suggest that the cells participating in the induction and expression of the immune response are distinctly modulated in their activity by in vivo exposure to magnesite dust.

Rat and rabbit response (in relation to age) to inhalation of automobile exhaust fumes.

Rats of two age groups, of 119 and 163 g mean body weight, were exposed for three and thirty days, respectively, to automobile gases diluted with air. In addition, rabbits, of 1.88 kg mean body weight, were exposed for twenty-four days. The conditions of exposure were kept nearly constant as related to the concentration of CO in the chamber. The following determinations were performed: (1) Body weight measurements as evidence of growth of the animals; (2) The number of alveolar macrophages (AM) in the lung washings; (3) Damage to the integrity of the cytoplasmic membrane of AM; (4) Glucose-6-phosphate dehydrogenase activity (G6PD) in AM; (5) The acid-base balance in the capillary blood of the rabbits. The results of the 30-day exposure show that automobile exhaust gases significantly inhibit the growth of both age groups; with significant body weight losses in the older animals from the 16th day of exposure. The number of AM was elevated in both groups. The activity of G6PD increased in the AM of the younger animals and decreased in the AM of the older as compared with the controls. The number of dead AM was higher in the older than in the younger rats. After the three-day exposure, no significant difference was found in the number of AM washed from the lungs of both exposed groups, compared with the controls. However, G6PD activity and the number of viable AM in the older animals were decreased and the percent of dead phagocytes was significant. The opposite effect was seen in the younger group. Alterations of lung tissue structure in the exposed animals were apparent to the naked eye. Acid-base response showed metabolic and respiratory disturbances as evidenced by the decrease in carbon dioxide tension (PCo2), the rise of hemoglobin by the reduction of pH level and by the base excess (BE). The inhibition of the growth of the rabbits was noted. The intra- and extrapulmonary effect of automobile exhaust gases after inhalation was observed as a complex of disturbances of the fundamental metabolic processes in the organism. The gases affected the cells of lung defence-alveolar macrophages and their biosynthetic activity.