Experimental studies of sensitization to beryllium, zirconium, and aluminum compounds in the rabbit

Ion leaching from dental ceramics during static in vitro corrosion testing

Dental ceramics are often called inert materials. It can be hypothesized, however, that differences in the composition, microstructure, and environmental conditions will affect the degree of corrosion degradation in an aqueous environment. The aims of the study were, therefore, to study the ion dissolution from glass-phase ceramics, with or without crystalline inclusions, and from all-crystalline ceramics and to compare the effects of different corrosion media. Ceramic specimens were produced from glass-phase and oxide ceramics and given an equivalent surface smoothness, after which they were subjected to in vitro corrosion (Milli-Q water at 37 +/- 2 degrees C for 18 h and 4% acetic acid solution at 80 +/- 2 degrees C for 18 h, respectively). The temperature of the corrosion solution was slowly increased until it reached 80 +/- 2 degrees C to reduce the risk of microcrack formation at the surface. The analyses of ion leakage were performed with inductively coupled plasma optical emission spectroscopy. A large number of inorganic elements leached out from the various dental ceramics. The major leaching elements were sodium and potassium; in the acid-corrosion experiments, there were also magnesium, silicon, and aluminum and, on a lower scale, yttrium, calcium, and chromium. The various glass-phase ceramics displayed significant differences in ion leakage and significantly higher leakage values than all-crystalline alumina and zirconia ceramics. No significant difference in dissolution was found between high and low-sintering glass-phase ceramics or between glass-phase ceramics with high volume fractions of crystallites in the glass phase in comparison with those with lower crystalline content. It can be concluded, therefore, that none of the dental ceramics studied are chemically inert in an aqueous environment.

Effects of intrabronchial foreign body retention

Unrecognized bronchial foreign bodies (Fbs) cause irreversible changes in the airways. However, the exact course of these changes is not well-known. We developed an animal model of bronchial obstruction to radiologically and histopathologically assess the development of postobstructive pulmonary changes. A piece of peanut was placed in the airways of 21 rabbits through a 2.5-mm rigid bronchoscope. Animals were divided into three groups (groups I-III) that were sacrificed on day 3,10, and 30 after Fb placement, respectively. Prior to sacrifice, since there were no differences between the groups prior to Fb placement, computerized tomography (CT) of the lung was taken, and the lungs were harvested for histologic analysis under light microscope. In group I, leukocyte infiltration around the bronchial wall (P = 0.0003) and edema (P = 0.0384) around the alveolar septa were the predominant histological findings. The CT scan was normal. In group II and group III, increased amounts of mononuclear cells and macrophage infiltration around the bronchial wall were observed (P = 0.0008, P = 0.0409, respectively). There were no differences in presence of granuloma formation, emphysema, atelectasis, or thickness of alveolar septa among the three groups. The CT scan of group II showed consolidations plus minimal bronchial dilatation in the involved lung of the rabbits (P not significant). Bronchial cartilage destruction was seen in 4 out of 7 rabbits in group III (P = 0.0071). We conclude that 30-day retention of intrabronchial peanut caused bronchial cartilage destruction and fibrosis that were attributed as bronchiectatic changes in the airways of the lung parenchyma. Therefore, any case with suspected foreign body aspiration should be treated immediately to prevent possible irreversible changes of the lungs.

Patch testing with beryllium alloy samples in guinea pigs

An experimental study was conducted in guinea pigs for the predictive assessment of the beryllium alloy hazard in occupational exposure of the skin to beryllium compounds. Guinea pigs were sensitized to beryllium sulfate according to the maximized Magnusson and Kligman test, and challenged with beryllium alloys and metallic copper, beryllium and aluminum samples. Results showed a delayed skin hypersensitivity reaction in 30 to 60% of pre-sensitized guinea pigs challenged with copper-beryllium alloys and aluminum-beryllium alloy. An inflammatory follicular reaction was induced by copper in both controls and pre-sensitized guinea pigs.

Metals and the skin

Certain metals, and many metal-based compounds, are inherently toxic, and their presence in occupational and environmental settings raises appropriate questions concerning human exposure. Contact of these materials with the skin represents an important route of exposure, which is not well characterized. The purpose of this review, therefore, is to assemble the available, useful information pertinent to risk assessment following dermal contact. Specifically, we summarize here: (1) data relevant to the qualitative and (where possible) quantitative evaluation of metal compound permeation through the skin; (2) the role of each metal in metabolism, particularly with respect to the skin, and the potentially toxic effects that may result from dermal contact; and (3) the immunological characteristics (including allergenicity) of the metals and their derivatives. In total, information on 31 metals has been reviewed. It is clear that many diverse factors determine the ability of metal-based species to permeate biological membranes, not all of which have been fully defined. Therefore, considerably more experimentation, targeted at the development of high-quality transport data, will be required before the specification of practically useful structure-activity relationships are possible.

Zirconium. An abnormal trace element in biology

The action of Zirconium (Zr) on biological systems presents an enigma. It is ubiquitous, being present in nature in amounts higher than most trace elements. It is taken up by plants from soil and water and accumulated in certain tissues. The entry into animal systems in vivo is related to the mode of exposure and the concentration in the surrounding environment. Retention is initially in soft tissues and then slowly in the bone. The metal is able to cross the blood brain-barrier and is deposited in the brain and the placental barrier to enter milk. The daily human uptake has been known to be as high as 125 mg. The level of toxicity has been found to be moderately low, both in histological and cytological studies. The toxic effects induced by very high concentrations are nonspecific in nature. Despite the presence and retention in relatively high quantities in biological systems, Zr has not yet been associated with any specific metabolic function. Very little information is available about its interaction with the compounds of the genetical systems, such as nucleic acids. Apparently, the metal is neither an essential nor toxic element in the conventional sense. However, the increasing exposure to this element through its increasing use in new materials and following radioactive fallout, has increased the importance of the study of its effects on living organisms. The tetravalent nature of the ionic state and the high stability of the compounds formed are important factors that need to be considered, as also the accumulation of this element in the brain, reminiscent of the relationship between Al3+ and Alzheimer's disease.

Dosimetry of beryllium in cultured canine pulmonary alveolar macrophages

This study was designed to determine the dosimetry within macrophages of beryllium compounds administered at sublethal doses. Information on the dosimetry of beryllium within macrophages is required to guide further efforts to isolate and characterize beryllium-containing haptens. Inhalation of beryllium aerosols can cause chronic berylliosis, a progressive, granulomatous fibrosis of the lung. Studies in laboratory animals indicate that alveolar macrophages take up beryllium compounds and participate in a hypersensitivity immune response to beryllium-containing antigen. Beagle dog macrophage cultures were incubated with 7BeSO4 in solution or with suspensions of 7BeO particles that had been calcined at 500 or 1000 degrees C. Beryllium-7 was measured in fractions collected from cultures after successive centrifugation and filtration steps at 2, 6, 20, and 48 h after addition. An insignificant percentage of BeSO4 was taken up by the cells and did not cause cytotoxicity. Maximum BeO uptake occurred within 6 h, was 60 +/- 6% of added BeO, and was independent of BeO calcination temperature or specific surface area. Approximately 22% of 500 degrees C BeO dissolved within 48 h after addition to cell culture, concurrent with 39% cell killing. Dissolved beryllium remained associated with cells until a cytotoxic concentration was reached (2.2 x 10(-5) M, 15 nmol Be/10(6) cells), when the beryllium was released into the medium. There was no significant dissolution of the 1000 degrees C BeO within 48 h, and no significant cell killing. The results indicate that beryllium dissolved from phagocytized BeO was more cytotoxic than soluble beryllium added extracellularly. The data support an interactive mechanism in which phagocytized BeO particles were dissolved, and dissolved beryllium remained associated with the macrophage until a cytotoxic concentration accumulated, whereupon the beryllium was released to the medium and not appreciably taken up by viable cells.

The effect of beryllium compound solubility on in vitro canine alveolar macrophage cytotoxicity

Pulmonary alveolar macrophage cells (PAM), obtained by bronchopulmonary lavage of Beagle dogs, were exposed in vitro to beryllium oxide (BeO) particles calcined at either 500 or 1000 degrees C or to beryllium sulfate (BeSO4). Cell viability was determined by trypan blue dye exclusion after 20 h in culture. The most toxic material tested was BeSO4, followed by BeO calcined at 500 degrees C, then BeO calcined at 1000 degrees C. An in vitro dissolution technique was used to measure the relative solubility of the BeO particles. The BeO prepared at 500 degrees C exhibited greater solubility compared with BeO prepared at 1000 degrees C. This study extends previous work by examining the effects of beryllium compounds on canine PAM, and by relating PAM cytotoxicity with measured values of beryllium compound solubility.

The health effects of aluminum compounds in mammals

This review, which is based on evaluation of information published in the last decade related to the health effects of aluminum compounds in mammals, directs attention to the well-documented effects of A1(III) compounds on phosphate metabolism. It is suggested that the toxic effects currently associated with A1(III) compounds are dependent upon the nature of A1(III) complexes formed from electron donating groups, rather than restricted to the presence of the high charge density matrix of A1(III) itself.

Pseudo-lymphocyte monocytes--the memory cells responsible for the development of epitheloid cell granulomata. A new hypothesis

This hypothesis proposes that, in individuals with an appropriate genetic background, monocyte memory cells are formed when histiocytes and macrophages undergo mitosis following first exposure to a granulomagenic agent and circulate as pseudolymphocytes in the lymphocyte null cell population. It is proposed that epithelioid cell granulomata develop from a clone of cells formed from monocyte memory cells on the second or subsequent exposure to the same granulomagenic agent. Epithelioid cell granuloma formation is therefore not dependent on T-cell function, although the cellular nature of the granuloma appears to depend upon the nature of a concomitant but independent classical immune response. The implications of pseudolymphocyte memory cells on the development of granulomata of both exogenous and endogenous origin, and the relationships between lymphocytes and cells of the monocytic phagocyte series are discussed.

Toxicokinetic and toxicodynamic studies of beryllium

The question of dose-effect relations of berylliosis was examined by measuring the Be-concentration in blood and urine, as well as the immunological behaviour of T-lymphocytes for a group of occupationally exposed men (smaller than 8 ng Be/m3, 4-6 h daily) and a non-exposed control group. Normal values 1.0 +/- 0.4 ng Be/g(n=10) in blood and 0.9 +/- 0.5 ng Be/g(n=10) in urine were found by an optimized flameless atomic absorption spectrometry method. The corresponding values for the exposed group (n=8) showed a mean increase of a factor of 4. The preferential enrichment of Be in the prealbumin and in the nu-globulin fractions was determined by a preparative isotachophoretic column with physiological pH conditions, especially developed for this application. The Be-specific stimulation of the T-lymphocytes of the exposed group was increased significantly. In blood and urine samples of exposed (2-40 mg Be/m3 as Be(NO3)2) Wistar-rats and guinea pigs Be values up to 36 ng Be/g in serum and up to 300 ng Be/g in urine were determined. After Be exposure, guinea pig serum showed a significant increase in the nu-globulins after the isotachophoretical separation of the serum proteins, which could not be correlated with increased Be-levels in this fraction. 70% of the total Be(10-100 ng/g serum) were detected in the prealbumin, only about 1% in the nu-globulin fraction. The same results were found in serum samples with in vitro addition of Be. The lymphocyte transformation rates for the exposed animals were increased. Skin tests were found to be positive in 70% for exposed rats and in 50-70% for guinea pigs.

Effects of asbestos and beryllium on release of alveolar macrophage enzymes

Rabbit alveolar macrophages were exposed in culture medium to asbestos, beryllium sulfate, and beryllium oxide. The specific activities of the lysosomal hydrolases, acid phosphatase beta-N-acetylglucosaminidase and beta-glucuronidase plus the glycolytic enzyme, phosphohexose isomerase were determined in the medium, whole-cell homogenates, mitochondrial fractions, and supernatant. These hydrolases increased significantly in the medium but not in the mitochondrial fraction of cells exposed to dusts. Asbestos and beryllium sulfate were highly cytotoxic for alveolar macrophages in vitro and the data suggested that these agents were not associated with an increase in enzyme synthesis but rather a direct cytotoxic effect at the macrophage membrane level. For induction of enzyme release in vitro, a higher concentration of beryllium oxide was needed when compared with asbestos and beryllium sulfate. The cytotoxicity and enzyme release induced by these agents may represent an important nonspecific mechanism by which they induce inflammation and perhaps local proliferation of fibroblasts.