Exposure analysis of five fish-consuming populations for overexposure to methylmercury.

Mercury, in the form of methylmercury, is found in a myriad of fish species consumed by recreational and subsistence fishers around the world. Many agencies have attempted to address the issue of mercury consumption, resulting at times in the placement of advisories on waterways used for fishing. In this study, consumption rates of three Native American populations and two recreational fishing populations consuming freshwater or saltwater fish species were examined. These consumption rates were combined with fish contamination data to assess the level of exposure to methylmercury and to determine if any of these populations exceed a derived tolerable daily intake (TDI) for methylmercury (0.035 to 0.08 microg/kg/day). The TDI is unlikely to result in adverse health effects and is based on scientific studies investigating sensitive endpoints in children of mothers who consume fish over prolonged periods of time. Results from the exposure analysis indicate that many within the Native American populations exceed the TDI. This occurs even though the mercury concentrations in certain fish species are comparable to concentrations found in fish from open waters where "background" levels are assumed. Recreational anglers consuming freshwater species have exposure levels below the TDI as do nearly all anglers consuming saltwater species. Similar populations or populations having comparable consumption patterns of fish with equal or higher mercury levels in other areas will also exceed the TDI level for mercury. The public health implications of this exposure analysis are discussed.

The effect of fish consumption on DDT and DDE levels in breast milk among Hispanic immigrants.

A study was conducted to (1) determine the concentration of DDT/DDE in the breast milk of mothers residing in the Yakima river basin (WA, USA), (2) assess the relative impact of fish consumption on the total DDT/DDE body burden, and (3) determine if the amount of DDT/DDE received by their breastfed infants exceeds levels that could produce deleterious effects. Results indicate that fish consumption did not significantly increase DDT/DDE breast milk concentrations. Subjects born in Mexico had elevated levels of DDT/DDE in breast milk compared to levels found in US born subjects regardless of fish consumption. Infant daily intake levels for the various subject groups were determined and compared to acceptable and tolerable daily intake levels. With benefits of breast milk well understood, breastfeeding should still be strongly recommended for these mothers.

Establishing tolerable dungeness crab (Cancer magister) and razor clam (Siliqua patula) domoic acid contaminant levels.

Domoic acid has been found in razor clams (Siliqua patula) and dungeness crabs (Cancer magister) in Washington State and elsewhere on the West Coast of the United States. Due to toxic effects associated with domoic acid exposure, an effort has been made to establish tolerable domoic acid levels in crabs and clams obtained from commercial harvest and sale and from individual recreational harvesting. To accomplish this, the amount of clams and crabs consumed by populations of concern was determined, a tolerable daily intake (TDI) was developed for individuals most sensitive to effects of this compound, and the TDI was equated with consumption patterns to determine tolerable clam and crab domoic acid levels. Results indicate that the primary health effects associated with domoic acid toxicity can be averted in populations of concern and for others consuming crabs or clams less frequently (or in lesser quantity) if domoic acid contaminant concentration does not exceed 30 mg/kg in the hepatopancreas and viscera of dungeness crabs or 20 mg/kg in clams.

Determination of a tolerable daily intake of DDT for consumers of DDT contaminated fish from the lower Yakima River, Washington.

DDT, DDE, and DDD have been detected at elevated concentrations in sediments and fish of the Yakima River, its tributaries and drainages. An assessment was conducted to evaluate the public health significance of eating fish from the river. This was accomplished by establishing a daily intake level of DDT for the population of greatest concern, and comparing this level to a tolerable daily intake. The most sensitive and highly exposed group was determined to be breastfeeding infants. Infant daily intakes of DDT, based on estimated mother's DDT-breast milk levels, were compared to a recommended tolerable daily intake. Results indicate that mothers who frequently consume Yakima River bottom-feeding fish could have breast milk DDT concentrations sufficiently high to expose their infants to levels above the tolerable daily intake.

Contact allergy to isothiazolinone derivatives: unusual clinical presentations.

Contact allergic reactions to the mixture of 5-chloro-2-methyl-4-isothiazoline-3-one and 2-methyl-4-isothiazoline-3-one are most frequently associated with intolerance to cosmetics. The present article points out that such reactions, particularly on the face, can have unusual clinical presentations that are very similar to seborrheic eczema, lupus erythematosus, lymphocytic infiltrate or photodermatitis. Atopic dermatitis is also often erroneously suspected.

Alterations of hepatic acetyl-CoA carboxylase by 2,3,7,8-tetrachlorodibenzo-p-dioxin.

The effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on acetyl-CoA carboxylase (ACC) activity and synthesis was examined. Male Wistar rats received a single i.p. injection of TCDD (53 micrograms/kg), and nine days later body weight, liver weight, hepatic lipid, ACC activity and mass were determined and compared to pair-fed controls. Body weights of TCDD-treated animals decreased, while liver weights increased resulting in an increase in liver to body weight ratios. ACC activity was decreased by 65%, however sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western analysis using a biotin specific probe revealed that ACC protein levels were not appreciably changed. In addition, there was a large increase in exogenous lipid material in TCDD-treated livers as determined by osmium tetroxide staining. These data suggest that the decrease in ACC activity may be due to direct inhibition of the enzyme by negative allosteric interactions with free fatty acids released from adipose tissue that subsequently accumulate in liver.

Expression of ras genes in rainbow trout liver.

Members of the ras gene family have been studied in a variety of species. Two ras genes expressed in the normal liver of rainbow trout, ras-1 and ras-2, as well as a portion of a genomic ras-1 allele, are described for the first time in this report. Over 500 bp of trout ras-1 and at least 300 bp of trout ras-2 genes expressed in normal liver have been sequenced; DNA homology to the human ras genes ranges from 76.8% to 87.1%. The base changes resulting from over 400 million years of evolutionary divergence between the species were primarily silent, with few changes in protein sequence. The partial DNA sequence of the genomic ras-1 allele has 86.8% homology to the first two exons of human c-Ha-ras, and its intron has several conserved sequences characteristic of vertebrate intron-exon junctions. However, the predicted amino acid sequence of trout ras-1 differs at only one of the first 172 amino acid residues from human c-Ki-ras with the alternate exon 4b. Since trout ras-1 differs at 17 and 18 residues from the human c-N-ras and c-Ha-ras proteins, respectively, over this region, we conclude that trout ras-1 is a c-Ki-ras gene. The highly conserved nature of this gene suggests that the ras p21 protein has identical functions in normal and neoplastic cells among higher and lower vertebrates.

Analysis of ras gene mutations in rainbow trout liver tumors initiated by aflatoxin B1.

The suspect human hepatocarcinogen aflatoxin B1 (AFB1) is a well-known potent initiator of hepatic tumors in rainbow trout (Oncorhynchus mykiss). Both hepatocellular carcinomas and mixed hepatocellular/cholangiocellular carcinomas are induced by AFB1 in trout, with the mixed form predominating. We previously isolated two c-ras genes from trout liver cDNA, and in the present study we analyzed DNA from 14 AFB1-induced trout liver tumors for point mutations in exon 1 of both genes. Using the polymerase chain reaction (PCR) and oligonucleotide hybridization methods, a high proportion (10/14) of the AFB1-initiated tumor DNAs showed evidence of activating point mutations in the trout c-Ki-ras gene. Of the 10 mutant ras genotypes, seven were codon 12 GGA----GTA transversions, two were codon 13 GGT----GTT transversions, and one was codon 12 GGA----AGA transition. Nucleotide sequence analysis of cloned PCR products from four of these tumor DNAs provided definitive evidence for two codon 12 GGA----GTA mutations, one codon 12 GGA----AGA mutation, and one codon 13 GGT----GTT mutation, in complete agreement with the oligonucleotide hybridization results. No mutations were detected in exon 1 of a second trout ras gene also expressed in liver, nor in DNA from control livers. This is the first report of experimentally induced ras gene point mutations in a lower vertebrate fish model. The results indicate that the hepatocarcinogen AFB1 induces c-Ki-ras gene mutations in trout similar to those in rat liver tumors.

Contact allergy to corticosteroids: a frequently missed diagnosis?

Contact allergy to corticosteroids is more prevalent than previously recognized and often goes undetected. Nineteen patients with corticosteroid contact allergy are presented. Sixteen reacted to tixocortol pivalate and also to other corticosteroids, particularly to hydrocortisone, which could explain exacerbations of eczema in these cases. Tixocortol pivalate may be a useful marker for screening patients for contact sensitivity to several corticosteroids.

Replication blocks and sequence interaction specificities in the codon 12 region of the c-Ha-ras proto-oncogene induced by four carcinogens in vitro.

We have examined the region surrounding codon 12 in the human c-Ha-ras proto-oncogene in vitro to determine the reaction intensities at the guanine nucleotides after exposure to the mycotoxin aflatoxin B1, to one of its human metabolites aflatoxin M1, to dimethyl sulfate, and to the major ultimate carcinogen of benzo(a)pyrene, benzo(a)pyrene diol-epoxide. Among the adducts produced, those at N-7-guanyl sites are alkali-labile and can be identified using a variation of the Maxam-Gilbert sequencing procedure. Data indicate that the guanine nucleotides of codon 12 have above average potential for adduct formation by the genotoxins when compared to other guanine sites, but were not the strongest sites. This codon 12 region has been inserted into single-stranded M13 phage, exposed to several of the genotoxins, and used as a template for DNA synthesis in vitro. There is a sequence-specific variation in polymerase inhibition at various adducted nucleotide sites, but replication blocks are not preferentially seen at the carcinogen-adducted guanines of codon 12. These results indicate that the predominance of point mutations which are detected in vivo at codon 12 do not reflect sequence-mediated preferential susceptibility of these sites to initial DNA adduction or to replication errors. The mechanisms controlling these sequence effects are not currently understood, and attempts to predict relative alkylation or termination frequencies based solely on local DNA sequence are not reliable.

Site-specific aflatoxin B1 adduction of sequence-positioned nucleosome core particles.

The question of how the presence of nucleosomal packing of DNA modifies carcinogen interaction at specific sites cannot be answered by studies on whole chromatin or bulk nucleosomes because of the heterogeneity of DNA sequences in the particles. We have circumvented this problem by using nucleosomes that are homogenous in DNA sequence and hence in DNA-histone contact points. A cloned DNA fragment containing a sea urchin 5 S gene which precisely positions a histone octamer was employed. By using 32P end-labeled DNA and genotoxins that allow cleavage at sites of attack, the frequency of adduction at every susceptible nucleotide can be determined on sequencing gels. The small methylating agent dimethyl sulfate and the bulky alkylating agent aflatoxin B1-dichloride (AFB1-Cl2) were used to probe the influence of DNA-histone interactions on DNA alkylation patterns in the sequence-positioned core particle. We find dimethyl sulfate to bind with equal preference to naked or nucleosomal DNA. In contrast, AFB1-Cl2 binding is suppressed an average of 2.4-fold at guanyl sites within nucleosomes compared with AFB1-Cl2 affinity at the corresponding site in naked DNA. The DNA is more accessible in regions near the particle boundary. We observe no other histone-imposed localized changes in AFB1-Cl2 sequence specificity. Further, sites of DNase I cleavage or proposed DNA bending show neither enhanced nor reduced AFB1-Cl2 adduction to N7-guanine. Since AFB1-Cl2 binding sites lie in the major groove, nucleosomal DNA appears accessible to AFB1-Cl2 at all points of analysis but with an access which is uniformly restricted in the central 100 nucleotides of the core particle. The data available do not indicate further localized or site-specific perturbations in DNA interactions with the two carcinogens studied.

Isolation and identification of acetyl-CoA carboxylase from rainbow trout (Salmo gairdneri) liver.

Acetyl-CoA carboxylase is the pivotal enzyme in the de novo synthesis of fatty acids and is the only carboxylase with a biotin-containing subunit greater than 200,000 daltons. The biotin moiety is covalently linked to the active site and has a high affinity (Kd = 10(-15) M) for the protein avidin. This relationship has been used in previous studies to identify acetyl-CoA carboxylase isolated from mammalian species. However, acetyl-CoA carboxylase has not been isolated and characterized in a poikilothermic species such as the rainbow trout. The present study describes the isolation and identification of acetyl-CoA carboxylase in the cytosol of rainbow trout (Salmo gairdneri) liver. The enzyme was isolated using two distinct procedures--polyethylene glycol precipitation and avidin-Sepharose affinity chromatography. Identification of the isolated protein as acetyl-CoA carboxylase was made by the following: (1) sodium dodecyl sulfate-polyacrylamide gel electrophoresis; (2) avidin binding; (3) in vivo labeling with [14C]biotin; and (4) acetyl-CoA carboxylase-specific activity. The subunit molecular weight of the major protein was 230,000 daltons +/- 3.3%. This protein was shown to bind avidin (Mr = 16,600) prior to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicating the presence of biotin. In addition, protein isolated from fish that had previously received intraperitoneal injections of [14C]biotin, showed the majority of radioactivity associated with the 230,000 dalton protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative binding and sequence interaction specificities of aflatoxin B1, aflatoxicol, aflatoxin M1, and aflatoxicol M1 with purified DNA.

The covalent binding of the activated forms of several aflatoxins to N-7 of guanine residues on purified DNA has been studied. The aflatoxins include aflatoxin B1 (AFB1) and two human metabolites, aflatoxicol and aflatoxin M1, along with aflatoxicol M1, a rabbit and trout metabolite. DNA binding studies using tritiated [3H]aflatoxins indicate that equimolar solutions of each aflatoxin upon activation with chloroperoxybenzoic acid readily react to produce covalently bound adducts. These reactions produce alkali-labile sites which can be identified using a simple variation of the Maxam-Gilbert sequencing procedure. Two DNA fragments were exposed to each aflatoxin, and the reaction intensities at 33 guanine residues were determined. As much as 10-fold variation in reaction intensities was observed for various guanyl sites. Data indicate that none of the aflatoxins had identical reaction profiles, although AFB1 and aflatoxicol M1 were similar, as were aflatoxicol and aflatoxin M1. Hence, the frequency with which the various aflatoxin epoxides might damage specific sites critical for tumor initiation in vivo would not be predictable from total covalent binding indices. The frequency of occurrence of modifications at particular sites for AFB1 was also compared with the empirical "rules" established for AFB1 by Misra et al. (Misra, R. P., Muench, K. F., and Humayun, M. Z. (1983) Biochemistry 22, 3351-3359). Identical sites within fragments were compared for each aflatoxin, and the data showed that the attacking frequency for some such sites varied significantly. These results indicate that binding intensity rules based on nearest neighbor nucleotides do not reliably predict guanyl-AFB1 binding frequencies.

Adult linear IgA bullous dermatosis with bronchial involvement.

A 54-year-old man is described, suffering from adult linear IgA bullous dermatosis with involvement of the bronchial mucosa. The main respiratory symptoms were recurring haemoptysis, episodic narrowing of the airways and persistent non-specific bronchial hyperreactivity. On CT scan the trachea had a saber-sheath shape with tracheal ring calcification. Endoscopically the tracheo-bronchial mucosa was diffusely purpuric and hyperaemic and also showed pale elevated plaques, bullous lesions and ulceration. Histological examination of biopsies of skin and nasal and tracheo-bronchial mucosa showed subepithelial blister formation associated with an accumulation of polymorphonuclear cells at the epithelial-subepithelial junction, and linear IgA deposits on direct immunofluorescence.