Embryotoxicity of 3,3′,4,4′-tetrachloroazobenzene and 3,3′,4,4′-tetrachioroazoxybenzene in the chick embryo

The toxicity of 3,3,4,4-tetrachloroazobenzene (TCAB) and 3,3,4,4-tetrachloroazoxybenzene (TCAOB) to chick embryos was examined. TCAB or TCAOB was dissolved in corn oil and injected into the air cell of fertile chicken eggs. The time of injection had a major effect on embryo mortality as eggs injected with TCAB or TCAOB on the fourth day of incubation had a higher incidence of embryo mortality than eggs injected on days 11–13. Both TCAB and TCAOB were more toxic than all other chemicals that have been tested in the chick embryo with the exception of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Comparing the potency of the two compounds, TCAOB was more potent than TCAB in the chick embryo with an estimated LD₅₀ of 12 ng and 44 ng respectively. Rump edema was the major abnormality observed in embryos treated with either TCAB or TCAOB. Other malformations included altered feather pattern and lack of down, hemorrhage, external viscera, reduced body size, failure to withdraw the yolk sac, beak malformation, dilation of blood vessels, and monomicropthalmia. The results of this investigation suggest that both TCAB and TCAOB are teratogenic in the chick embryo.This work was presented in part at the Annual Meeting of the Society of Toxicology, San Diego, CA, March 1–5, 1981.     

Short-Term Distribution, Metabolism, and Excretion of 2,2′,5-Tri-, 2,2′,4,4′-Tetra-, and 3,3′,4,4′-Tetrachlorobiphenyls in Prepubertal Rats

The excretion and tissue retention of three ¹⁴C-labeled lower chlorinated biphenyls were examined in prepubertal male and female Sprague-Dawley rats following IV administration. Urine and feces were collected individually at different time intervals up to 72 h for pharmacokinetic analyses. After 72 h, different organs were removed and extracted in acetone:hexane (1:1, v/v) to determine radioactivity. Within the first 10 h after dosing, 2,2′,5-trichlorobiphenyl (PCB 18) was rapidly excreted in urine (8–18% of the administered dose), whereas only 0.6–0.8% of 2,2′,4,4′-tetrachlorobiphenyl (PCB 47) and 0.3–0.8% 3,3′,4,4′-tetrachlorobiphenyl (PCB 77) were found in urine during this time period. The half-life of elimination was shortest for PCB 18 (37.5 to 49.2 h). The half-lives for PCB 47 and PCB 77 were 351 to 672 h and 152 to 186 h, respectively. The cumulative total excretion (urinary + fecal) of PCB 18 within 72 h was 51–62%, of PCB 77 was 22–25%, and of PCB 47 was 7–10%. No parent PCBs were detected in urine. PCB 47 accumulated preferentially in adipose tissues (subcutaneous fat > mesenteric fat); relatively high levels of PCB 47 were also found in adrenals, ovaries, lungs, liver, and skin. The highest concentration of PCB 77 was found in serum, followed by adipose tissues. Very low concentrations of PCB 18 were found in most tissues; the highest being found in serum, followed by ovaries and adrenal glands. This study suggests that prepubertal rats retain higher short-term serum levels and have lower excretion rates than adult rats. Received: 3 February 1998/Accepted: 16 August 1998     

Biological Activity and Physicochemical Parameters of Marine Halogenated Natural Products 2,3,3′,4,4′,5,5′-Heptachloro-1′-Methyl-1,2′-Bipyrrole and2,4,6-Tribromoanisole

Physicochemical parameters (vapor pressure, water solubility, Henrys law constant) and biological activities of two halogenated natural products frequently detected in marine samples and food were determined. Synthetic 2,3,3,4,4,5,5-heptachloro-1-methyl-1,2-bipyrrole (Q1) and 2,4,6-tribromoanisole (TBA) were available in pure form. The physicochemical parameters were in the range of anthropogenic chlorinated compounds of concern. The aqueous solubilities at 25°C (S_w,25) of Q1 and TBA were 4.6 g/L and 12,200 g/L, respectively, whereas subcooled liquid vapor pressures were 0.00168 Pa (Q1) and 0.06562 Pa (TBA) as measured by the gas chromatographic–retention time technique. Q1 was negative by established test systems for the determination of ethoxyresorufin-O-deethylase (EROD) induction and by sulforhodamine B assay. EROD induction potency was at least 10^–7 times lower than that of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). At a relatively high concentration (20 M), Q1 inhibited specific binding of 2 nM [³H]TCDD to the in vitro-expressed human aryl hydrocarbon receptor (AHR) by 18%; lower concentrations showed no effect. Molecular modeling showed that Q1 is nonplanar, consistent with its relatively modest affinity as an AHR ligand. When tested for cell-growth inhibitory/cytocidal activity in human tumor cells, Q1 was only marginally, if at all, active with an IC₅₀ value >50 M compared with five to ten times lower IC₅₀ values for potent cytotoxins tested in the test system used. Furthermore, standard pesticide tests on insecticidal, herbicidal, and fungicidal activity did not provide any significant activity at highest concentrations. For TBA, the results in all tests were comparable with Q1. The SRB assay was also applied to the halogenated natural product 4,6-dibromo-2-(2,4-dibromo)phenoxyanisole, but no toxic response was found. Although it was apparent that Q1 and TBA had been proven to have relatively low biological activity in all tests performed, further research is necessary to clarify whether metabolites of the compounds eventually may possess a risk to humans or other living organisms. Nevertheless, the role of Q1 in nature remains uncertain.     

2,2′,4,4′,6,6′-六硝基二苯基乙烯的急性毒性评价

目的研究不敏感含能材料2,2′,4,4′,6,6′-六硝基二苯基乙烯(HNS)的急性经口毒性、急性眼刺激性、皮肤刺激性、皮肤致敏毒性,为HNS的职业健康防护提供理论指导。方法根据《化学品毒性鉴定技术规范》,采用SD大鼠、豚鼠、日本大耳白兔进行急性经口毒性、皮肤致敏毒性、急性眼刺激性和皮肤刺激性试验。结果急性经口毒性采用最大限量法一次性染毒,14 d观察期内大鼠无死亡,大体解剖无异常;急性眼刺激性试验,兔染毒0.1 g HNS后,眼刺激性总积分平均值为0分,未发现损伤作用;皮肤刺激性试验,兔染毒0.5 g HNS后,皮肤刺激性总积分平均值为0分,未观察到腐蚀性和刺激性;皮肤致敏试验,20只豚鼠染毒0.4 ml HNS,诱导浓度为1 000 mg/ml,激发浓度为500 mg/ml,激发接触24 h后共有5只豚鼠皮肤出现轻微红斑或水肿,48 h后染毒组皮肤反应恢复正常。染毒组阳性致敏率与阴性对照组比较,差异有统计学意义(P<0.05)。结论根据毒性分级标准进行判定,HNS低毒,无眼刺激性和皮肤刺激性,具有轻度致敏性。     

Reproductive,immunologie, and cytogenetic effects of dietary 3,3′,4,4′-tetrachloroazoxybenzene exposure to mice

The effects of chronic dietary exposure to 3,3,4,4-tetrachloroazoxybenzene (TCAOB) on the reproductive efficiency of female Swiss-Webster mice were measured. The immunocompetence of their offspring was assayed at weaning. No indications of toxicosis were seen in the adult females with the exception of a reduction in the thymus weight of the animals consuming 10 ppm TCAOB. Pup mortality to weaning and the percentage of females whelping were not affected by 0.1 ppm, 1 ppm, or 10 ppm of TCAOB in the diet. There was, however, a significant reduction in the number of pups (at birth and at weaning) per female whelping at 10 ppm TCAOB in the diet. The thymus weight and plaque-forming-cell response of the pups were also significantly reduced below control levels. The lymphocyte blastogenic response to Concanavalin-A and lipopolysaccharide, and total peripheral blood leukocyte count, were not affected by the concentrations of TCAOB tested. Dietary treatment of female mice with relatively high concentrations of this chemical resulted in reduced reproductivity capacity, but only moderate immuno-suppression of their offspring exposed duringin utero and early postnatal development.Spleen cells of mice exposedin vivo to TCAOB for 28 days via the diet were examined for chromosome damage and sister chromatid exchange. TCAOB was investigated because of its similarity to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD); TCAOB caused significantly increased chromatid breakage, suggesting that it may be affecting protein synthesis or may be a mutagen. However, TCAOB did not result in a significant increase in sister chromatid exchanges or isochromatid breaks even at a dietary concentration of 40 ppm.     

Adverse Effects of 2,2′,4,4′-Tetrabromodiphenyl Ether on Semen Quality and Spermatogenesis in Male Mice

2,2′,4,4′-Tetrabromodiphenyl ether (BDE47) is an environmental contaminant. To determine the reproductive toxicity, we studied groups of adult male mice and found that the rate of sperm capacitation was decreased significantly in three BDE47-exposed groups (0.0015, 0.045 and 30 mg kg^?1 day^?1). Sperm motility parameters (MOT, PRO, VCL and BCF) after capacitation were also declined in treated groups. Moreover, exposure to BDE47 at concentrations of ≥0.045 mg kg^?1 day^?1 caused increased germ cell loss and apoptosis in some seminiferous tubules. Our results suggest that short-term exposure to low-dose BDE47 may have adverse effects on semen quality and spermatogenesis in adult male mice.     

Effects of 3,3′,4,4′-tetrachloroazoxybenzene on selected immune parameters of the mouse

The effects of 3,3,4,4-tetrachloroazoxy-benzene (TCAOB) on the immune system of mice was examined and compared with cyclophosphamide (CY). This chemical can be produced as a result of microbial degradation of commonly used chloroaniline herbicides. Herbicides of the acylan-iline class generally have a low mammalian toxicity while remaining relatively inexpensive. Therefore, TCAOB could be formed anywhere in the environment where choroaniline pesticides are used. TCAOB treatment caused thymic atrophy and a decrease in white blood cell (WBC) count after sheep red blood cell (SRBC) immunization. A decline in the number of Lyt-1⁺ cells (T-helper lymphocytes) was seen in all TCAOB animals, with unimmunized mice also showing a decreased number of Lyt-2.2⁺ cells (T-suppressor lymphocytes). No change was found in the ratio of these two cell types. TCAOB did, however, result in a severe reduction in the number of plaque-forming-cells (PFCs) and in serum antibody concentration. CY caused a decrease in thymus weight, WBC count, the number of cells recovered per spleen, and the relative percentages of Lyt-l⁺ and Lyt-2.2⁺ cells recovered. The mice exhibited a lower lymphocyte blastogenic response to lipopolysaccharide (LPS) than control animals, but no change in Concanavalin A (Con-A) responsiveness. CY also resulted in a severe drop in the number of PFCs and the quantity of antibody produced following SRBC immunization.     

Chronic toxicity and bioaccumulation of 2,5,2′,5′- and 3,4,3′,4′-tetrachlorobiphenyl and Aroclor® 1242 in the amphipodHyalella azteca

The addition of 100 (g/L of Aroclor^® 1242 (A1242) or 2,5,2,5-tetrachlorobiphenyl (TeCB) during 10 week chronic toxicity tests withHyalella azteca resulted in complete mortality. There were no effects on survival, growth, or reproduction after addition of 30 g/L. Toxic effects were observed at tissue levels of between 30 and 180 g/g on a wet weight basis, and tissue levels appear to be a better indicator of toxicity than levels in water. No toxic effects were observed after additions of up to 2,700 g/L of the coplanar congener 3,4,3,4-TeCB.H. azteca has the ability to avoid accumulating in excess of 140 g/g 3,4,3,4-TeCB. The amount taken up was proportional to the amount added in water up to 100 g/L, but was constant at higher additions, possibly accounting for its relatively low toxicity. The low toxicity of the coplanar congener, as compared to the non-coplanar 2,5,2,5-TeCB, is in direct contrast to the high toxicity of coplanar PCB congeners to mammals and may be associated with slower rates of aromatic hydrocarbon metabolism in amphipods. Polychlorinated biphenyl levels measured in amphipods from Lake Ontario are approximately 100-fold below levels associated with toxicity inH. azteca, but are above levels which, through biomagnification up the food chain, lead to salmonid residues in excess of 2 g/g, a tolerance limit for human consumption.     

Tissue Distribution of Methylsulfonyl Metabolites Derived from 2,2′,4,5,5′-Penta- and 2,2′,3,4′,5′,6-Hexachlorobiphenyls in Rats

The time courses of fecal excretion and tissue distribution of metabolites derived from 2,2′,4,5,5′-pentachlorobiphenyl (CB101) and 2,2′,3,4′,5′,6-hexachlorobiphenyl (CB149) were investigated in male Wistar rats. The metabolism of both congeners involved primarily hydroxylation at the 3-position, and methylthiolation at the 4-position. Metabolites distributed in tissue were dominated by different ratios of 3- and 4-methylsulfonyl (MeSO₂) metabolites. The 3-/4-MeSO₂ metabolite ratios in liver and adipose tissue for both congeners were 0.41–0.61 at day 4, and then increased to 0.85–1.00 for up to day 42. In contrast, the ratios in lung were 0.03–0.04, and then decreased to 0.01. Compared to the unchanged PCBs at day 42, the distribution ratios of 3-MeSO₂ metabolites were greater in the order of liver (0.46 for CB101 and 0.21 for CB149) > kidney > blood > lung > adipose tissue, whereas those of 4-MeSO₂ metabolites were in the order of lung (9.50 for CB101 and 4.00 for CB149) > kidney > blood > liver > adipose tissue, indicating the different binding affinity of 3-MeSO₂ metabolites in liver from that of 4-MeSO₂ metabolites in lungs of rats. Furthermore, the structure-tissue affinity relationship for 3-MeSO₂ metabolites was investigated, following the administration of 11 3-MeSO₂-PCB congeners to rats. The results indicated that the retention potential of 3-MeSO₂ metabolites in the liver largely depends on the ortho-chlorine substitution in the biphenyl ring rather than the degree of chlorination. Received: 17 July 1998/Accepted: 11 January 1999     

Toxicity of 3,4,5,3′,4′,5′-hexachlorobiphenyl to mink

Diets supplemented with 0.01 or 0.05 ppm (mg/kg) of 3,4,5,3,4,5-hexachlorobiphenyl (345-HCB) were fed to mink to investigate the toxicological manifestations of this toxic polychlorinated biphenyl congener in a sensitive species. Dietary exposure of mink to 0.05 ppm 3,4,5,3,4,5-hexachlorobiphenyl for 135 days resulted in 50% mortality while no deaths occurred on 0.01 ppm 345-HCB. Clinical signs of toxicity included anorexia, bloody stools, disrupted molting patterns, and thickened, elongated and deformed nails. Ascites and gastric ulcers were present in animals that died. Statistically significant increases in liver, kidney, and adrenal gland weights were found in the 345-HCB-treated mink. Decreases in total and free triiodothyronine concentrations were observed in mink fed the 345-HCB-treated diets and total thyroxine was decreased in the mink fed 0.05 ppm 345-HCB. No consistent histopathologic lesions were found in the thyroid or adrenal glands of the 345-HCB-treated mink, nor were there any statistically significant differences between the 345-HCB-treated and the control mink in serum epidermal growth factor levels, plasma 17-estradiol and progesterone concentrations, hepatic aminopyrine N-demethylase, and benzo()pyrene hydroxylase activities, hypothalamic norepinephrine, dopamine, and serotonin concentrations or in the incorporation of (³H) thymidine by concanavalin-A-stimulated lymphocytes.Published with the approval of the Michigan Agricultural Experiment Station as Journal Article Number11963.     

Occurrence of Selected Polybrominated Diphenyl Ethers and 2,2′,4,4′,5,5′-Hexabromobiphenyl (BB-153) in Sewage Sludge and Effluent Samples of a Wastewater-Treatment Plant in Cape Town,South Africa

The reuse of treated effluent from wastewater treatment plants (WWTPs) as alternative water source for sport-field or landscape irrigation, agricultural, and other industrial purposes is growing significantly. Similarly, the application of treated sludge (biosolid) to agricultural soils is now being considered globally as the most economic means of sludge disposal. However, the presence of emerging organic contaminants in these matrices, including polybrominated diphenyl ethers (PBDEs), which are potential endocrine disruptors, portends a high health risk to humans and the environment in general. In this study, effluent and sewage sludge samples collected from a WWTP were analysed for some selected PBDE congeners (BDE congeners 28, 47, 99 100 153 154 183, and 209) as well as BB-153 using a high-capillary gas chromatograph equipped with an electron capture detector. The sum of the eight PBDE congeners ranged from 369 to 4370, 19.2 to 2640, and 90.4 to 15,100 ng/l for raw water, secondary effluent, and final effluent, respectively. A similar result was observed for sewage sludge samples, which ranged between 13.1 and 652 ng/g dry weight (dw). The results obtained for BB-153 were generally lower compared with those found for most PBDE congeners. These ranged from ND to 18.4 ng/l and ND to 9.97 ng/g dw for effluents and sewage sludge, respectively. In both matrices, BDE 47 and 209 congeners were found to contribute significantly to the overall sum of PBDEs. The reuse of the treated effluent, particularly for agricultural purposes, could enhance the possibility of these contaminants entering into the food chain, thus causing undesirable health problems in exposed subjects.     

Comparative toxicokinetics of 2,2′- and 4,4′-dichlorobiphenyls in the pond snailLymnaea stagnalis (L.)

Pond snails (Lymnaea stagnalis (L.)) were treated with 2,2-dichlorobiphenyl (DCB) or 4,4-DCB, to examine the toxicokinetic profile of these compounds. Snails were treated orally with 210 g 4,4-DCB (impregnated on food) for 14 hr, or snails were injected with 50 g of 2,2-DCB or 4,4-DCB in the foot. At different times after starting feeding or injection, tissues (albumen gland, digestive gland and digestive tube, central nervous system, remainder parts), hemolymph and faeces were analyzed for unchanged 2,2- or 4,4-DCB. The results showed that in case of oral administration of 4,4-DCB after 144 hr, 97.5% of the dose was excreted unchanged in the faeces. During the first 48 hr 4,4-DCB was found in all tissues. Thereafter, an exponential elimination was found (the rate constant of elimination (k_el) varied from 0.010–0.021 per hr, t_1/2 from 33–60 hr and the apparent clearance from 0.02–0.3 g/hr for the different tissues). After injection, the compounds were found in all the above mentioned tissues, especially in the digestive gland. There was a clear difference between snails injected with 2,2- and 4,4-DCB. Firstly, k_el for 2,2-DCB was higher (0.028 per hr vs 4,4-DCB: 0.001 per hr). Secondly, 2,2-DCB was lethal; 63% of the animals died after 72 hr.     

3′,4′-Dihydroxyflavonol attenuates spatial learning and memory impairments in global cerebral ischemia

Objectives: In the present study, effects of 3′,4′-dihydroxyflavonol (DiOHF) on anxiety-like behavior, and learning and memory were investigated in a model of transient global cerebral ischemia and reperfusion.

Methods: The animals were assigned to sham-operated, ischemia, and two DiOHF-treated (10 mg/kg i.p.) groups. DiOHF was administered at 1 hour before and immediately after the ischemia. Male rats were subjected to bilateral common carotid artery occlusion to induce acute cerebral ischemia for 20 minutes, followed by reperfusion for 7 days. The openfield, elevated plus maze (EPM), and Morris water maze tests were used to evaluate the effects of DiOHF treatment on ischemia-induced locomotor activity, anxiety-like behavior, and spatial and recognition memory impairments, respectively.

Results: In the open field test, locomotor activity in the ischemic rats was not altered 6 days after the ischemia, nor was anxiety-like behavior, which was evaluated with the EPM (P > 0.05). In the water-maze test, cerebral ischemia significantly decreased the exploration time in the target quadrant, and the platform crossing counts were lower (P < 0.05) in the probe trial test; this memory impairment was significantly improved by DiOHF applied 1 hour before and immediately after ischemia (P < 0.05).

Discussion: All together, these findings suggest that DiOHF reverses spatial learning and memory deficits resulting from transient global ischemia but has no significant effect on anxiety-like behavior.     

Determination of 4,4′-, 3,4′-, and 2,2′-Diaminodiphenylethers in Sediment Samples from the Sea Using Liquid Chromatography-Tandem Mass Spectrometry

A selective method has been developed for determining the concentration of 4,4′-, 3,4′-, and 2,2′-diaminodiphenylethers in sediment samples from the sea, using liquid chromatography/tandem mass spectrometry (LC/MS/MS). 4,4′-diaminodiphenylether is a suspected toxic compound, and categorized as “Class I Designated Chemical Substance” in Japan. We have investigated the levels of 4,4′-diaminodiphenylether in sediments to evaluate long-term water pollution. The methods detection limits for the 4,4′-, 3,4′-, and 2,2′-diaminodiphenylethers were 2.0, 1.7, and 4.8 ng/g-dry, respectively.     

Determination of urinary 4,4′-methylenedianiline and its acetylated metabolites by solid-phase extraction and HPLC analysis with UV and electrochemical detection

An analytical procedure based on solid-phase extraction and high-performance liquid chromatography using both ultraviolet and electrochemical detection was developed to determine, without derivatization, stable urinary forms of 4,4-methylenedianiline (MDA) and of its acetylated metabolites at the pg/1 level, in post-shift urine from 63 exposed workers. The determination of MDA,N-acetyl MDA (MAMDA) andN,N-diacetyl MDA (DAMDA) was achieved on the non-hydrolysed urine samples, and that of total MDA on urine samples after alkaline hydrolysis. It was necessary to protect urine samples with sulfamic acid in order to stabilize amines and to improve the precision and accuracy of the analyses. Under these conditions, unstable labile conjugates were determined as their parent stable amine. The distribution of total MDA, MDA, MAMDA and DAMDA was assessed in 116 urine samples. Their relative concentrations (arithmetic means) were found to be in the following order: total MDA > MAMDA > MDA > DAMDA. While MAMDA represented more than 50% of total MDA, MDA and DAMDA were lower than 15% and 3% respectively. Acetylation of MDA, described as a possible pathway of detoxication, is confirmed to be an important metabolization route in humans, essentially through the monoacetylated metabolite. However, the individual ratio MAMDA/total MDA was found to vary widely (roughly from 0% to 100%).     

Global Gene Expression Analysis in the Livers of Rat Offspring Perinatally Exposed to Low Doses of 2,2′,4,4′-Tetrabromodiphenyl Ether

Background

Polybrominated diphenyl ethers are a group of flame-retardant chemicals appearing increasingly in the environment. Their health effects and mechanisms of toxicity are poorly understood.

Objectives

We screened for the sensitive effects and mechanisms of toxicity of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) by analyzing the gene expression profile in rats exposed to doses comparable to human exposure.

Methods

Wistar dams were exposed to vehicle or BDE-47 (0.002 and 0.2 mg/kg body weight) every fifth day from gestation day 15 to postnatal day 20 by injections to caudal vein. Total RNA was extracted from the livers of pups and hybridized to the whole-genome RNA expression microarrays. The list of genes 2-fold differentially expressed was exported to PANTHER and Ingenuity Systems for analysis of enriched ontology groups and molecular pathways.

Results

Oxidoreductase and transferase protein families were enriched in exposed rats as were these biological process categories: carbohydrate metabolism; electron transport; and lipid, fatty acid, and steroid metabolism. Four signaling pathways (cascades of activation of drug-metabolizing enzymes) and 10 metabolic pathways were significantly enriched. Drug-metabolizing enzymes appear to be regulated by BDE-47 through an aryl hydrocarbon receptor–independent mechanism. Direct interaction with retinoid X receptor or its upstream cascade may be involved. The main metabolic effects consisted of activation of metabolic pathways: α- and ω-oxidation of fatty acids, glycolysis, and starch hydrolysis.

Conclusions

Altered expression of genes involved in metabolic and signaling pathways and functions of the organism occurs after perinatal exposure of rat offspring to BDE-47 at doses relevant for the general population.     

Assessment of occupational exposure to 4,4′-methylenedianiline by the analysis of urine and blood samples

Seven workers at a work site where methylenedianiline (MDA) was used as a curing agent for an epoxy resin were studied during 4 workdays and one weekend. Internal exposure was monitored by analysis of 4,4-MDA in hydrolysed urine and blood. After acidic hydrolysis, MDA was extracted, derivatised by use of pentafluoropropionic anhydride, and determined by gas chromatography and mass spectrometry, with negative ion chemical ionization. There was wide variation of MDA concentrations in hydrolysed blood between the workers (range 10–60 nmol/l). Also, the urinary excretion rate varied considerably both between and within the individual workers (0–90 mol/h). The urinary excretion displayed some variation in relation to exposed periods. The urinary levels were linearly related to the concentrations in blood (r _s= 0.93,P = 0.02). The present results show the value of excretion of MDA in hydrolysed urine and concentrations in blood as means for the biological monitoring of MDA exposure. In this case, the exposure was probably mainly dermal, in spite of extensive protection measures.     

Synthesis and aldose reductase inhibition activity of spiro-[9H-fluoren-9,4′-imidazolidine]-2′,5′-dione derivatives

A series of substituted spiro-[9H-fluoren-9,4′-imidazolidine]-2′,5′-diones was prepared by Bucherer—Berg condensation followed by various modifications of a carboxylic functional group. The compounds obtained were examined for their abilities to inhibit the enzyme aldose reductase both in vitro and in vivo.High potency in inhibiting the semi-purified calf lens enzyme in vitro was observed for several of the tested compounds. Two of the compounds have been found to be very effective in reducing sorbitol accumulation in the lenses and sciatic nerves of rats treated with streptozotocin. Substitution on positions 1 or 2 of the fluorene ring led to inactive compounds, whereas substitution on positions 3 or 4 enhanced inhibitory activity with respect to the unsubstituted spirofluorohydantoin 50. These observations are discussed in light of the previously published structural requirements of the allosteric binding site of the enzyme aldose reductase.