André Penninks

Toxicity of organotin compounds. III. Suppression of thymus-dependent immunity in rats by di-n-butyltindichloride and di-n-octyltindichloride

To evaluate the functional significance of di-n-butyl (DBTC)- and di-n-octyltin dichloride (DOTC)-induced lymphoid depletion various immune function studies were carried out. The delayed type hypersensitivity reaction, a parameter of cell-mediated immunity was decreased in rats fed 50 or 150 ppm of DOTC for 6 weeks. This decrease was dose-related. Allograft rejection, another cellular immune response, was significantly delayed by DBTC and DOTC. The antibody response against E. coli LPS, probably a T cell-independent antigen, was not affected by DBTC. However, the humoral immune response against sheep red blood cells (SRBC), which needs the co-operation of T helper cells and B cells, was distinctly depressed by DBTC. Hemagglutination and hemolysin titers as well as the number of direct plaque-forming cells against SRBC per spleen were decreased in a dose-related manner by DBTC. The phagocytic capacity of macrophages of rats was not affected by DOTC as was shown in the carbon clearance test. Altered immune functions were never found in mice or guinea pigs exposed to DBTC or DOTC. From this study it is concluded that both DBTC and DOTC induce immune suppression in rats by a selective inhibition of T-lymphocyte activity. Immune suppression was most pronounced in animals exposed to the chemicals during the developmental phase of the lymphoid system.

The range of minimum provoking doses in hazelnut-allergic patients as determined by double-blind, placebo-controlled food challenges

Background The risk for allergic reactions depends on the sensitivity of individuals and the quantities of offending food ingested. The sensitivity varies among allergic individuals, as does the threshold dose of a food allergen capable of inducing an allergic reaction.

Short term toxicity of tri-n-butyltinchloride in rainbow trout (Salmo gairdneri Richardson) yolk sac fry

Abstract Rainbow trout in the yolk sac fry stage were continuously exposed to tri-n-butyltin-chloride (TBTC) at concentrations of 0, 0.2, 1 and 5 ppb (μg/liter) for 110 days. After a 10 to 12 days exposure period, at the transition of the yolk sac fry stage to the swimming fry stage, all fish of the 5 ppb group suddenly died without any preceding symptoms. Hydropic degeneration of tubule segments of the pronephros was the main finding in these animals, whereas no histopathological changes were noted in animals exposed to 0.2 or 1 ppb for 10 days. At these exposure levels TBTC induced a significant and dose-related growth retardation resulting in a 44% decrease of the body weights in the 1 ppb group at the end of the experimental period. Hemoglobin content of the blood was decreased in a dose-related fashion and the number of red blood cells was significantly decreased at the 1 ppb exposure level. Histopathologically hyperplasia of liver cells was observed and as a consequence, the relative liver weights were significantly increased in a dose-related manner (both at a concentration of 0.2 and 1 ppb TBTC). From this study it is concluded that the applicability of tributyltin compounds as molluscicidal agents for the vector control of schistosomiasis remains very doubtful, since the concentrations required to kill snails are of the same range as those inducing disturbances in young rainbow trout.

Immune suppression as a consequence of a selective cytotoxic activity of certain organometallic compounds on thymus and thymus-dependent lymphocytes.

The biologic effects of organometallic compounds have been reviewed by Barnes and Magos’ and more recently by Thayer.* Organometallic compounds are used in a variety of applications. Organoarsenicals were much in use as antibiotics until about 1940, when they were largely replaced by penicillin; they also were developed as poison gas. From the organolead compounds, tetraethyllead has an especially important application as gasoline additive. The present report deals mainly with organotin compounds, which are applied as heat stabilizers, catalytic agents, and biocidal compounds.’ Trialkyltin compounds are extensively used as preservatives for wood and paper and as paint additives especially to control marine fouling. Triaryl compounds are effective fungicides and insecticides. Dialkyltins are mainly used as heat stabilizers, especially for the stabilization of plastics. Only some dioctyltin derivates are permitted by the U S . Food and Drug Administration as additives in polyvinyl chloride (PVC) products which come in contact with food. In European countries dimethyltins are also allowed in PVC for food packing purpose. With the possible exception of mercurials (not included in this article) organotin compounds have received more attention for their biologic effects than organic compounds of any other metal. Their toxicity has been extensively reviewed by Barnes and Stoner4 and more recently by Piver.’ However, no attention was paid to the effects of organotin compounds on the lymphoid system. In recent studies, Seinen and c o a ~ t h o r s ~ ~ have shown that the main effect of some dialkyltin compounds in rats was on the thymus and thymus-dependent lymphoid structures. The present report reviews the relationship of chemical structure of organotin, organolead, organogermane, and some organoarsenic compounds and their lymphocytotoxic activity. The consequence of organotin-induced lymphocytotoxicity for the functioning of the immune system will be evaluated.

Triorganotin-induced cytotoxicity to rat thymus, bone marrow and red blood cells as determined by several in vitro assays

To further investigate the immunotoxic effects of tri-n-propyltin chloride (TPTC), tri-n-butyltin chloride (TBTC) and triphenyltin chloride (TPhTC) several cytotoxicity tests with a series of trialkyltin chlorides and TPhTC were carried out, using isolated rat thymocytes as target cells. Thymocytes, cultured in a serum-supplemented medium, were exposed to organotin concentrations ranging from 0.01 to 10 microM for periods up to 30 h. Parameters such as cell count, trypan blue exclusion, chromium release, thymidine incorporation and cyclic AMP production were used to evaluate the cytotoxicity of these compounds. The more lipophilic compounds TPTC, TBTC, tri-n-hexyltin chloride (THTC) and TPhTC appeared most cytotoxic, reducing thymidine incorporation at concentrations as low as 0.05-1 microM. Membrane damage as determined by trypan blue exclusion and chromium release occurred at higher levels (1-10 microM). The water soluble homologue trimethyltin chloride (TMTC) was least effective in all test models. When phosphate-buffered saline supplemented with glucose was used as incubation medium, TBTC appeared more cytotoxic to thymocytes. Using this medium in 5-h incubations the cytotoxicity of TBTC to thymus, bone marrow and red blood cells was compared. Bone marrow cells were slightly less sensitive than thymocytes, while red cells were relatively resistant. In conclusion, of the triorganotin compounds especially the lipophilic homologues are cytotoxic in vitro.

How accurate and safe is the diagnosis of hazelnut allergy by means of commercial skin prick test reagents

Background: Allergy to tree nuts, like hazelnuts, ranks among the most frequently observed food allergies. These allergies can start at early childhood and are, in contrast to other food allergies, not always outgrown by the patient. Tree nut allergy is frequently associated with severe reactions. Diagnosis partially relies on in vivo testing by means of a skin prick test (SPT) using commercially available SPT reagents. Methods: Protein and allergen composition of nine commercial SPT solutions was evaluated using standard protein detection methods and specific immunoassays for measurement of five individual allergens. Diagnostic performance was assessed by SPT in 30 hazelnut-allergic subjects, of which 15 were provocation proven. Results: Protein concentrations ranged from 0.2–14 mg/ml. SDS-PAGE/silver staining revealed clear differences in protein composition. The major allergen Cor a 1 was present in all extracts but concentrations differed up to a factor 50. An allergen associated with severe symptoms, Cor a 8 (lipid transfer protein), was not detected on immunoblot in three products, and concentrations varied by more than a factor 100 as was shown by RAST inhibition. Similar observations were made for profilin, thaumatin-like protein and a not fully characterized 38-kD allergen. Ratios of individual allergens were variable among the nine extracts. SPT showed significant difference, and 6/30 patients displayed false-negative results using 3/9 products. Conclusion: Variability in the composition of products for the diagnosis of hazelnut allergy is extreme. Sometimes, allergens implicated in severe anaphylaxis are not detected by immunoblotting. These shortcomings in standardisation and quality control can potentially cause a false-negative diagnosis in subjects at risk of severe reactions to hazelnuts.

Determination of protein allergenicity: studies in rats.

For the safety evaluation of genetically engineered crops the potential allergenicity of the newly introduced protein(s) has become an important issue. There is, however, no universal and reliable test system for the evaluation of the allergenic potency of food products. The best known allergy assessment proposal is the careful stepwise process using the IFBC/ILSI decision tree. Unfortunately, the described tests are not always conclusive, especially if the gene source coding for the protein has no history of dietary use and/or an unknown history in terms of allergenicity. The further testing warranted should in particular be focused on the prediction of the sensitizing potential of the novel protein, for which animal models are considered to be needed. In this paper the results are summarized of a promising food allergy model developed in Brown Norway (BN) rats. The results demonstrate that BN rats can be sensitized orally to the various allergenic food proteins tested, resulting in significant antigen-specific IgE responses, without the use of adjuvants. Upon oral challenge of previously sensitized animals, local and systemic immune-mediated effects, such as increased gastrointestinal permeability and decreased breathing frequency and blood pressure, could also be observed.

Comparative toxicity of organotin compounds to rainbow trout (Oncorhynchus mykiss) yolk sac fry

The comparative toxicity of various organotin compounds was investigated in early life stages of the rainbow trout. Beginning with yolk sac fry, trout were continuously exposed for 110 days to tributyl- (TBTC), triphenyl- (TPhTC) or tricyclohexyltin chloride (TCHTC) at concentrations of 0.12-15 nM, to trimethyltin chloride (TMTC) at concentrations of 3-75 nM or to dibutyl- (DBTC) or diphenyltin chloride (DPhTC) at 160-4000 nM. The diorganotin compounds DBTC and DPhTC were about three orders of magnitude less toxic than the triorganotin homologs TBTC and TPhTC. Both for DBTC and DPhTC, a no-observable-effect concentration (NOEC) of 160 nM was established, corresponding to 40 and 60 ppb, respectively. Of the triorganotin compounds, TCHTC appeared to be the most toxic, inducing 100% mortality within 1 week at a concentration of 3 nM. Only a few trout survived exposure to 0.6 nM TCHTC for 110 days. TBTC and TPhTC caused acute mortality at a concentration of 15 nM. For both TBTC and TPhTC a NOEC of 0.12 nM was established, corresponding to water concentrations of 40 and 50 ppt, respectively. Histopathological examination revealed depletion of glycogen in liver cells of both di- and triorganotin exposed fish, except in the case of TMTC. No signs of toxicity were observed in fish exposed to up to 75 nM TMTC, the highest concentration tested. Atrophy of the thymus, the most prominent sign of toxicity of di- and tributyltin compounds in mammalian species, was not observed in early life stages of rainbow trout. Tail melanization was observed in the groups exposed to 3 nM TPhTC, 3 nM TBTC, 800 nM DBTC and 800 nM DPhTC. At the end of the exposure period, resistance to infection was examined by an intraperitoneal challenge with Aeromonas hydrophila, a secondary pathogenic bacterium to fish. Resistance of bacterial challenge was found to be decreased even at the lowest-effect concentration of both di- and triorganotin compounds.

On the mechanism of dialkyltin-induced thymus involution

In relation to the thymolytic activity of dialkyltin compounds, the effects of di-n-butyltin (DBTC) and di-n-octyltin dichloride (DOTC) on the ultrastructure of the rat thymus, the proliferation of bone marrow stem cells and their interference with growth hormone production are analyzed. Ultrastructurally, depletion of small lymphocytes in the thymic cortex, without signs of lymphocyte destruction or macrophage activation, was the most prominent feature of DOTC treatment. The thymus cortex was maximally depleted 96 h after a single i.p. injection of 1 mg DOTC/kg body weight. 120 h after DOTC treatment a repopulation of the cortex with small lymphocytes was noted together with the presence of many pale large nuclei of large lymphocytes, suggestive of active blast transformation. These thymus effects are probably not caused by a diminished input of bone marrow stem cells into the thymus, since neither the spontaneous blastogenesis nor the colony formation of bone marrow cells isolated from DBTC-treated animals were affected. An indirect mechanism of thymus involution induced by interference with the hormonal system is also very unlikely. A stress-related increase of glucocorticosteroids by dialkyltins has already been excluded (Seinen and Willems, 1976). An interference of dialkyltins with growth hormone production, as indicated in this study, did not occur. Application of growth hormone in amounts that reversed the hypophysectomy-induced thymus atrophy did not modify the thymus involution induced by DOTC treatment of rats. However, an interference with the production of thymic humoral factors cannot be excluded yet, although it is not supported by morphological changes in thymic reticular cells. Only an increased vacuolization of reticular epithelial cells is seen when the thymus is markedly involuted, but this is considered to be a consequence rather than a cause of thymus atrophy. Most probably the dialkyltin-induced thymus involution is caused by an antiproliferative activity, which is strongly supported by an inhibition of thymidine incorporation of thymocytes isolated from DBTC-treated rats.

Assessment of protein allergenicity studies in brown Norway rats

Abstract: For the safety evaluation of genetically engineered crops, the potential allergenicity of the newly introduced protein(s) has become an important issue. There is, however, no universal and reliable test system for the evaluation of the allergic sensitizing ability of food proteins. Therefore, there is a growing interest in the development of animal models. This paper summarizes the results of a promising food allergy model developed in Brown Norway (BN) rats. The results demonstrate that BN rats can be sensitized via the relevant oral route of exposure. Daily gavage dosing of the animals with several food proteins, without the use of adjuvants, resulted in significant antigen‐specific IgE responses. In addition, the profile of allergens recognized by the immune system of the BN rat, appeared comparable to the profile of allergens recognized by allergic humans. Besides oral sensitization, local and systemic immune‐mediated effects, such as increased gastrointestinal permeability, decreased breathing frequency, and decreased blood pressure, could also be observed in the sensitized animals after an oral challenge. All together, these observations suggest that this BN rat model might provide a suitable animal model to study the allergenicity of food proteins in humans.