Cutaneous sensitization to some polyisocyanate prepolymers in guinea pigs.

Isocyanates are used extensively in the polyurethane industry. Pulmonary and dermal sensitization resulting from exposure to diisocyanates has frequently been reported, but the potential effects of polyisocyanates on health are less well known. Thus, since 1978, occupational exposure limits have been established for diisocyanates only. Nevertheless, respiratory diseases and dermatitis have been reported in the polyurethane industry after accidental isocyanate contact during spills or splashes. The aim of this experimental work was to assess the dermal hypersensitivity of guinea pigs to some polyisocyanate prepolymers by means of a well-conducted standard predictive Buehler test. Our results showed that dicyclohexylmethane 4,4'-diisocyanate (HMDI), toluylene 2,4-diisocyanate (TDI), TDI adduct triol, TDI isocyanurate, 1,6-hexamethylene diisocyanate (HDI), HDI isocyanurate, HDI biuret and isophorone diisocyanate (IPDI) induced dermal sensitization while IPDI isocyanurate did not. In conclusion, the dermal hypersensitivity of guinea pigs to some polyisocyanates was similar to those of their corresponding monomers except for IPDI isocyanurate, suggesting that the results from diisocyanate monomers could not be a valuable approach for the detection of the sensitization potency of the corresponding prepolymers.

Histopathological study in B6C3F1 mice chronically exposed by inhalation to glutaraldehyde.

Glutaraldehyde vapors are irritating for the skin, eyes, nose and lungs; respiratory symptoms and headaches have been described among workers exposed to low concentrations of glutaraldehyde far below to 190 ppb. This study was initiated to determine the chronic effects in mice of inhaled glutaraldehyde vapors. B6C3F1 mice were exposed using whole-body inhalation chambers, 6 h/day, 5 days/week, for 52 and 78 weeks to 100 ppb, or to filtered air (controls). In nasal passages at the level of the vestibule, hyperplasia of the squamous epithelium lining of the dorsal wall and lateral aspect of the atrioturbinate was observed in a greater number of exposed females than in controls. Epidermal erosion and ulceration as well as squamous and inflammatory exfoliation were also seen in the nasal lumens. All these changes were dependent on the length of glutaraldehyde exposure. The present data suggest that glutaraldehyde long term exposure only led to changes in nasal passages of female mice but did not induce mortality and/or tumors in nasal passages, in all mice. These results, along with the previous subchronic inhalation study of Gross et al., 1994, demonstrates that in a long term study, chronic glutaraldehyde exposure close to the current threshold limit values induced lesions at the more anterior part of the nasal passages in mice and that they likely result from an irritation mechanism (antero-posterior gradient).

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.

Use of non-radioactive methods for the determination of the expression, the sequence and the copy-number of transgene in mice.

Marshall's observation that "toxicology goes molecular", is turning out to be more true than ever; namely as it is observed that toxicological endpoints are the point of interaction between proteins and genes following the administration of toxicants. Transgenic mice represent a valuable tool for studying the adverse effects of chemicals in genetically engineered animals such as p53 deficient mice, or mice carrying the v-Ha-ras oncogene. The latter were used in our laboratory for such toxicological assessments of chemicals. In order to verify that the transgene was expressed in normal, as well as in tumor cells, the transgene was detected in different tissues fixed with various solutions using in situ hybridization. It was also specifically retrotranscribed from paraffin-embedded tissues and consequently sequenced using a Taq polymerase reaction. We found that the transgene was expressed in various organs. It carries a specific mutation of codon 12 leading to the activation of its encoded product (transducin: p21v-Ha-ras). Moreover using a laser scanning densitometer, it has been demonstrated that 2 to 3 copies of the transgene were present per genome-equivalent in some tissues. All experiments were realized using non-radioactive labelling and detection (chemiluminescent or colorigenic) methods. Indeed, the screening of such animals was realized in a easier and a safer manner using the methods described in this paper than the usual methods based on the use of radiolabelled precursors.

Histopathological changes in the respiratory tract of mice exposed to ten families of airborne chemicals.

The objective of this experimental work was to identify and compare the histopathological changes induced in the respiratory tract of Swiss mice exposed to repeated inhalation (4, 9 or 14 days) at typical concentrations of RD50, 0.3 x RD50 and 3 x RD50 of airborne chemicals. These substances were selected from ten chemical families: aldehydes, organic acids, alcohols, ketones, ethers, aromatic hydrocarbons, halogenated aromatic hydrocarbons, inorganic bases, amines and isocyanates. These experiments showed that the lesion intensity observed in the nasal passages varied with exposure duration and type of airborne chemical, but did not depend on the concentration of the substance. Results did not allow us to establish a relationship between the histopathological changes and the type of chemical family. No injuries were observed in trachea and lungs.

Experimental study of cutaneous tolerance to glycol ethers.

We tried out the potential irritant and sensitizing effect of the main glycol ethers found in industrial and consumer products. Cutaneous irritation was determined in the rabbit following the EEC method (European Economic Communities) and the Draize protocol, and the sensitizing effect was evaluated in the guinea pig by the maximized Magnusson and Kligman method. The results showed no delayed cutaneous hypertensitivity, and all glycol ethers studied were classified from slightly irritant to severely irritant according to the Draize protocol, though only 2-butoxyethanol and isopropoxyethanol were classified as skin irritants with the EEC method. Glycol ethers should be handled with all the care that should be taken in the safe use of organic solvents.

Nasal and pulmonary toxicity of glutaraldehyde in mice.

A concentration-dependent expiratory bradypnea, indicative of sensory irritation, occurred during a 15-min oronasal exposure of mice to glutaraldehyde in the concentration range of 0.7-4.5 ppm. The level of exposure which led to a 50% decrease in the respiratory rate (RD50) was found to be 2.6 ppm. For assessment of nasal toxicity, mice were exposed to glutaraldehyde vapours with concentrations of 2.6, 1.0, 0.3 ppm for periods of 6 h/day over the course of 4, 9 and 14 days and were immediately killed. Recovery was studied with another group of mice exposed to 1.0 ppm for 14 days and sacrificed after 1, 2 and 4 weeks rest time. Control groups were concurrently exposed to clean filtered air. The earliest lesions were observed in the respiratory epithelium of the septum, the naso- and maxilloturbinates, after 4 days of exposure to 0.3 ppm. Severe histopathological changes were still observed 2 weeks after the end of the exposure to 1.0 ppm. No exposure-related histological abnormalities were detected in the trachea and lungs. In conclusion, this experiment demonstrates that repeated exposure to 1/10 RD50 is associated with upper respiratory tract damage in mice, and this value does not seem to be an acceptable concentration limit for occupational exposure.

[Focusing on a test to evaluate the efficacy of skin barrier creams]. / Mise au point d'un test pour évaluer l'efficacité des crèmes barrières.

INTRODUCTION: The aim of this study was to adjust an experimental protocol with the rabbit to control the skin barrier creams efficacy. ELABORATE TECHNIQUE: Therefore, we applied irritant aqueous solutions and solvents on the shaved skin of the rabbit flank protected with one of these creams. We noticed inflammatory reactions of erythema and oedema but we also conducted an histological examination of the treated skin. DISCUSSION: This protocol is simple, there is no investment with equipment and only a few number of rabbits are required. There is only a difficulty with applying the same volume of cream since cream consistency is variable and makes the comparison between the different creams quite delicate. This method should be supported by well-controlled studies between several laboratories.

Changes in urinary proximal tubule parameters in neonatal rats exposed to cadmium chloride during pregnancy.

Pregnant Sprague-Dawley rats were injected intraperitoneally with physiological saline solution (vehicle) or cadmium chloride (CdCl2) at 2.0 or 2.5 mg kg-1 on days 8, 10, 12 and 14 of gestation. On postnatal day (PND) 3, 12 or 49, the offspring were examined for 8- or 24-h urinary excretion of beta 2-microglobulin (beta 2-m), metallothionein (MT) and urinary activity of three proximal tubular enzymes: gammaglutamyl transferase (GGT), alkaline phosphatase (ALP) and N-acetyl-beta-glucosaminidase (NAG). Treatment with CdCl2 did not affect growth or survival of offspring. Significant decreases in the urinary excretion of GGT, ALP and NAG were observed on PND 3, at both doses. Exposure to 4 x 2.5 mg kg-1 resulted in functional deficit of the proximal tubule on PND 3, as evidenced by the significant increase in beta 2-m. Except for a slight but significant increase of beta 2-m in 49-day-old males, all the other urinary parameters returned to control values on PND 12. There was no effect on MT. Results from this study show that prenatal exposure to CdCl2 can induce significant changes in the kidney biochemistry of rats in the early postnatal period.

Allergy to nickel or cobalt: tolerance to nickel and cobalt samples in man and in the guinea pig allergic or sensitized to these metals.

The aim of this study was to evaluate, in animals and humans sensitive to nickel or cobalt, the tolerance to manufactured metal samples of nickel and cobalt of a defined metallographic structure, plated or not with a layer of chrome or copper/chrome of a determined thickness. Under the defined experimental conditions, a guinea pig sensitized to one metal (nickel or cobalt) was intolerant to both metals (nickel and cobalt). A plating of chrome or copper/chrome did not act as a protection. In the human, it was not the same: the tolerance to metal samples was determined by the specific sensitivity. A plating of chrome or copper/chrome did not act as protection.

Effects of prenatal methylmercury exposure on urinary proximal tubular enzyme excretion in neonatal rats.

The basal developmental pattern of excretion of 3 proximal tubular enzymes was determined in 8-h urinary specimens from neonatal rats. Gammaglutamyltransferase (GGT), alkaline phosphatase (ALP), and N-acetyl-beta-glucosaminidase (NAG) activities were measured at 3, 6, 9 and 12 days after birth. Subsequently, methylmercury chloride (CH3HgCl), known to induce foetotoxic changes in the proximal tubule was administered on days 8, 10 and 12 of gestation at 3 or 6 mg/kg and its effects on the enzyme activities were examined. Dose-related increases in the 3 enzyme activities occurred at dose levels that produced no maternal or postnatal toxicity, nor overt morphological malformation of the kidney. The peak of enzyme activities averaged about 200% and 130% of the control values for GGT, ALP, and NAG respectively, and occurred on days 3 and 6 in the treated groups. Urinary enzyme activities returned to the control levels from days 6 to 12. Our data point to the possibility of detecting CH3HgCl-induced prenatal effect on the kidney by measuring the 8-h urinary excretion of enzymes by rats in the early postnatal period.

Nickel allergy: tolerance to metallic surface-plated samples in nickel-sensitive humans and guinea pigs.

The purpose of this work is to evaluate in nickel-sensitive patients and guinea pigs the tolerance to nickel samples, surface-plated with one or several metals of varying structures and thicknesses. All the metal samples elicited allergic reactions in the guinea pig. In humans, absolute tolerance was not observed for any sample. In humans, the interposing of a layer of bright copper between nickel and surface chrome greatly increased the tolerance.

Nasal and pulmonary toxicity of allyl glycidyl ether in mice.

A concentration-dependent expiratory bradypnea, indicative of irritation of the nasal mucosa, occurred during a 15-min oronasal exposure of mice to allyl glycidyl ether (AGE) in the concentration range of 1.9-8.6 ppm. The level of exposure responsible for a 50% decrease in the respiratory rate (RD50) was 5.7 ppm. Non-anaesthetized, tracheally cannulated mice exposed for 120 min to AGE at levels ranging from 105 to 185 ppm showed a concentration-dependent decrease in respiratory rate due to pulmonary toxicity. The level of exposure to AGE which produced a 50% decrease in the respiratory rate of tracheally cannulated mice (RD50TC) was 134 ppm. Mice were subjected to whole body exposure for 4, 9 or 14 days, 6 h/day to 7.1 or 2.5 ppm AGE. The 4-day exposure to 7.1 ppm AGE produced in the nasal cavities of mice lesions consisting of necrosis of the respiratory epithelium and complete erosion of the olfactory epithelium without pulmonary injury. Restorative responses were observed in the nasal cavities of mice exposed for 9 and 14 days to 7.1 ppm AGE. Exposure to 2.5 ppm AGE caused neither nasal nor pulmonary injury. The results indicate that AGE primarily affects the upper airways. They also make it questionable that the occupational standard of 5 ppm assures an adequate margin of protection against AGE-induced nasal effects.

Experimental sensitization of guinea-pigs to nickel and patch testing with metal samples.

Two groups each of 30 guinea-pigs were painted on 5 days/wk for 4 wk with 1% nickel sulphate in lanolin. The dose was applied to the shaved dorsal skin, which was prepared daily before treatment with sodium lauryl sulphate and injected intradermally each week during this period with 0.1 ml 1% potassium alum in distilled water, close to the site of NiSO4 application. Of the two groups of guinea-pigs submitted to this epicutaneous procedure, 63 and 80% developed skin allergy in response to challenge with 2% NiSO4 after a rest period of 2 wk, whereas no sensitization response was elicited by 1% NiSO4 in the guinea-pig maximization test. When two further groups were sensitized by the epicutaneous procedure, the first group, with a sensitization rate of 52% at the first challenge, showed no decline in response with five successive monthly challenges. Addition of NiCl2 to the drinking-water of the second group did not increase the sensitization rate induced by the monthly rechallenges with NiSO4. In guinea-pigs allergic to nickel, plating of Ni-coated brass discs with chromium as a special surface treatment prevented the occurrence of the contact allergy elicited by brass discs coated with Ni alone, whereas plating with gold/copper/cadmium did not.

Assessment of tail nerve function in rats chronically exposed to vinyltoluene.

In male Sprague-Dawley rats, motor and sensory conduction velocities (MNCV and SNCV) of the tail nerve decreased significantly as a result of oral administration of 400 and 200 mg/kg of 2,5 hexanedione (2,5-HD) once daily, 5 days a week for up to 7 and 15 weeks, respectively; and of whole-body exposure to 300 ppm of vinyltoluene for 6 h daily, 5 days a week for up to 21 weeks. Exposure to 100 ppm of vinyltoluene did not cause any significant impairment of tail nerve function throughout the 21-week exposure period. Significant changes in MNCV and SNCV were consistently observed from weeks 4 and 2, respectively, in 2,5-HD-treated rats. Changes resulting from exposure to 300 ppm of vinyltoluene were reported intermittently from week 15. Significant linear relationships were established between the length of treatment with 2,5-HD, length of exposure to 300 ppm of vinyltoluene, and the extent of impairment of tail nerve function. Structural damage to the sciatic nerves was only seen in 2,5-HD-treated rats. It is concluded that vinyltoluene can be regarded as an airborne chemical which leads to the development of a borderline experimental neuropathy at a level of 300 ppm.

The carcinogenic effect of a series of petroleum-derived oils on the skin of mice.

Six groups of 30 Swiss mice were treated by application to the skin in the dorsolumbar region two times a week for 12 months of a "white oil" and five samples of petroleum oils derived from the same "crude" (Middle East), which were collected in the same refinery at different stages of "solvent treatment" and which form a homogeneous series with increasing concentrations of polyaromatic hydrocarbons (PAH). The macroscopic and histopathologic examination of the animals (skin and organs) up to 18 months shows the following effects with respect to the 60-mouse control group: --a marked irritating effect for the "aromatic extract," the "distillate," and a "mixture" of intermediary concentration between "distillate" and "raffinate," --a definite tumorigenic effect on the skin (papillomas, kerato-acanthomas, squamous cell carcinomas, and fibrosarcomas) of the "aromatic extract" and the "distillate." The biological answer is in significant association with the PAH concentration of the samples, which is estimated by different analytical methods: viscosity index, percentage of aromatic carbon, "total PAH" according to a gravimetric method, and benzo[a]pyrene concentration.

Induced hepatotoxicity in female rats by aflatoxin B1 and ethynylestradiol interaction.

Female Sprague-Dawley rats were treated with a single ip dose of aflatoxin B1 (AFB1) (3 or 6 mg/kg). Twenty-four hours later and weekly until killed, some of the rats treated with AFB1 were given ethynylestradiol (EE) by gavage at the dose of 13 mg/kg. One, three, six, and nine months following the beginning of the experiment, animals were killed. Light microscopy of liver and histochemical determinations of gamma-glutamyltransferase (GGT) as well as the measurement of hepatic drug-metabolizing enzyme activities were investigated. The results show that AFB1 induced only very weak changes in the levels of different constituents studied. Thus, the mycotoxin did not affect GGT activity and increased epoxide hydrolase activity by a maximum of 42%. In contrast, EE significantly and progressively decreased (20 to 50%) the activity of UDP-glucuronosyltransferase (UDPGT) as well as the concentration of cytochrome P-450 and microsomal proteins. However, the estrogen increased the activity of epoxide hydrolase up to 150% as well as the activity of the hepatic (400%) and plasma (175%) GGT. The results also indicate that AFB1 amplified the EE-induced increase in liver weight and enhanced the depressive effects of the estrogen on microsomal proteins, cytochrome P-450, and UDPGT. Foci of cellular alteration which consisted of clear, acidophilic and basophilic cell lesions were seen in the livers of treated rats examined by light microscopy. These lesions were more prominent in the livers of animals given combinations of AFB1 and EE; they were accompanied by a strong intensity of GGT staining in the periportal area and a marked increase of the enzyme activity in the plasma (324%). From the sixth month, the livers of some animals treated with the combinations of AFB1 and EE showed hyperplastic nodules. This study indicates that the interaction between chronic administration of EE and a single ip injection of AFB1 induces hepatic lesions considered as possible forerunners of liver cell carcinomas. It also shows that GGT is a potential marker of preneoplastic lesions and may be used, therefore, in epidemiologic surveys in humans exposed to liver carcinogens such as the aflatoxins.

[Interaction between benzene and toluene in long term inhalation exposure in rats (author's transl)]. / Etude toxicologique chronique par inhalation chez le rat de l'association benzène - toluène.

Industrial chemicals are seldom used as pure substances; hazards resulting from exposure to mixtures have, however not been solved. Our study deals with chronic inhalation toxicity of a mixture of benzene and toluene; few studies have been completed on this subject. Our results show: - leucopenia with benzene alone, at a concentration of 50 p.p.m., that is not detectable in the presence of toluene; - metabolic variations consisting in: a decrease in the phenol urinary rate versus time with benzene alone; a sharp decrease of this rate from the third month of exposure on, in presence of toluene.