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Archives of Environmental Contamination and Toxicology (v.38, #4)
Dehalogenation of Xenobiotics as a Consequence of Binding to Humic Materials by J.-W. Park; J. Dec; J.-E. Kim; J.-M. Bollag (pp. 405-410).
Chlorinated phenols and anilines were transformed by oxidoreductive catalysts with release of chloride ions in both the absence and the presence of humic substances (syringaldehyde, catechol, and humic acid). Dehalogenation of these xenobiotics resulted from oxidative coupling reactions occurring at the chlorinated sites of the substrates. The effect of humic substances on dehalogenation depended on the mechanism of oxidative coupling. In a free-radical reaction mediated by peroxidase, laccase, or birnessite (δ-MnO2), syringaldehyde enhanced the dehalogenation of most of the chlorinated phenols, but it did not enhance the dehalogenation of the chloroanilines. With catechol, which does not form free radicals, dehalogenation was reduced or remained the same for both the chlorophenols and the chloroanilines. However, in tyrosinase-mediated reactions controlled by nucleophilic addition, catechol enhanced the dehalogenation of most of the chlorophenols, whereas syringaldehyde had little effect. Humic acid in most cases enhanced the dehalogenation of the chlorophenols, but it had little effect on the dehalogenation of the chloroanilines. On a molar basis, changes in dehalogenation caused by humic substances were proportional to the respective changes in substrate transformation. Only syringaldehyde was capable of releasing disproportionately high amounts of chloride ions from chlorophenols, apparently as a result of multiple cross-couplings to one molecule of the substrate.
A Multidisciplinary Approach to Assess History, Environmental Risks, and Remediation Feasability of Soils Contaminated by Metallurgical Activities. Part A: Chemical and Physical Properties of Metals and Leaching Ability by D. Venditti; S. Durécu; J. Berthelin (pp. 411-420).
Three soils contaminated by heavy metals (HMs) and aliphatic hydrocarbons originating from different industrial sources were characterized in a multidisciplinary study combining chemical, physical (Part A), and mineralogical (Part B) approaches to define history, environmental risks, and remediation feasibility. These were an agricultural soil located nearby a Zn/Pb smelter and two soils from a steel metallurgical (siderurgy) waste land. High Pb and Zn contents were reported for all, and high Cr, Cd, and aliphatic hydrocarbons were present in different combinations in two out of three soils. Carbonate matrixes more strongly cemented fine particles in the agricultural soil than in both siderurgical ones, but buffering capacities were stronger in the latter. After the disruption of these cements by ultrasounds, HM were concentrated in the <50-μm fraction of the agricultural and of one siderurgical soil. Sequential extractions indicated for all the soils a preferential association of HM with carbonates, Fe-Mn oxides, organic matter, and sulfides. The stirring of one siderurgical soil with water resulted in an immediate leaching of hexavalent chromium (0.3 mg · L−1) involving potential ecotoxicological risks.
A Multidisciplinary Approach to Assess History, Environmental Risks, and Remediation Feasability of Soils Contaminated by Metallurgical Activities. Part B: Direct Metal Speciation in the Solid Phase by D. Venditti; J. Berthelin; S. Durécu (pp. 421-427).
Three soils contaminated by industrial smelting activities previously characterized using chemical and physical approaches (Part A, Venditti et al.[2000] Arch Environ Contam Toxicol [in press]) were further investigated through a complementary mineralogical approach. X-ray diffraction allowed identification of the main mineral components: carbonates (calcite, siderite) and iron oxides (magnetite, hematite, goethite) prevailed in both siderurgical soils, and siliceous compounds were more abundant in the agricultural soil. Scanning electron microscopy coupled with energy dispersive x-ray microanalysis showed that carbonates and oxides contained low amounts of heavy metals (HMs), but the potential solubility of such species under acidic conditions associated to their abundance may result in a high mobility of associated contaminants. Microanalysis also revealed peculiar minor mineral forms (metallic nodules, alloys, ore residues) that were highly informative about the history of soil contamination. Small metal-rich particles were observed (brass, lead and zinc oxides). In such compounds, HMs showed high chemical stability and were consequently poorly mobile and toxic, but also poorly removable through chemical leaching. A risk of mechanical dispersion was suggested for these particles, particularly after the chemical and/or mechanical disruption of carbonate cements. These features allowed completion and confirmation of the conclusions achieved after chemical and physical investigations, providing accurate information about the history, environmental risks and remediation feasability of industrial soil contamination.
Characterization of Selected Element Concentrations and Enrichment Ratiosin Background and Anthropogenically Impacted Roadside Areas by R. A. Sutherland; C. A. Tolosa; F. M. G. Tack; M. G. Verloo (pp. 428-438).
Previous research by the National Contaminant Biomonitoring Program found fish from Manoa Stream, Hawaii, to have the highest concentrations of Pb in the nation. To explore possible source linkages we sampled background (uncontaminated) soil, roadside soil, and road deposited sediment in Manoa watershed and analyzed them for total and extractable concentrations of Al, Co, Cu, Fe, Mn, Ni, Pb, and Zn. Our concentration and enrichment ratio data indicate that Al, Co, Fe, Mn, and Ni were controlled by natural source variations, and Cu, Zn, and particularly Pb were anthropogenically enhanced. Labile Pb concentrations, extracted with either dilute HCl or EDTA, reached a maximum of 3,560 mg/kg compared to background values of <10 mg/kg. Additionally, 25% of the 169 contaminated samples analyzed had EDTA-extractable Pb enrichment ratios ≥11.5, where a value of 1 separates uncontaminated from contaminated media. Given the proximity of most samples to roadways it is reasonable to conclude that automotive emissions plus vehicle wear were the primary contributors of trace metals to the roadside system. These data are discussed in context with previous work on the fluvial bed sediments in this watershed in an attempt to examine the potential linkage with the biological accumulation of Pb in fish from Manoa watershed.
Influence of Petroleum Hydrocarbon Contamination on Microalgae and Microbial Activities in a Long-Term Contaminated Soil by M. Megharaj; I. Singleton; N. C. McClure; R. Naidu (pp. 439-445).
Petroleum hydrocarbons are widespread environmental pollutants. Although biodegradation of petroleum hydrocarbons has been the subject of numerous investigations, information on their toxicity to microorganisms in soil is limited, with virtually no work conducted on soil algae. We carried out a screening experiment for total petroleum hydrocarbons (TPH) and their toxicity to soil algal populations, microbial biomass, and soil enzymes (dehydrogenase and urease) in a long-term TPH-polluted site with reference to an adjacent unpolluted site. Microbial biomass, soil enzyme activity, and microalgae declined in medium to high-level (5,200–21,430 mg kg−1 soil) TPH-polluted soils, whereas low-level (<2,120 mg kg−1 soil) pollution stimulated the algal populations and showed no effect on microbial biomass and enzymes. However, inhibition of all the tested parameters was more severe in soil considered to have medium-level pollution than in soils that were highly polluted. This result could not be explained by chemical analysis alone. Of particular interest was an observed shift in the species composition of algae in polluted soils with elimination of sensitive species in the medium to high polluted soils. Also, an algal growth inhibition test carried out using aqueous eluates prepared from polluted soils supported these results. Given the sensitivity of algae to synthetic pollutants, alteration in the algal species composition can serve as a useful bioindicator of pollution. The results of this experiment suggest that chemical analysis alone is not adequate for toxicological estimations and should be used in conjunction with bioassays. Furthermore, changes in species composition of algae proved to be more sensitive than microbial biomass and soil enzyme activity measurements.
The Role of Ingestion as a Route of Contaminant Bioaccumulation in a Deposit-Feeding Polychaete by D. P. Weston; D. L. Penry; L. K. Gulmann (pp. 446-454).
A mass-balance bioaccumulation model was used to examine the bioaccumulation of benzo[a]pyrene (BaP) from ingested sediment by the deposit-feeding polychaete Abarenicola pacifica over a series of experiments employing nine different sediments. Through selective ingestion of fine-grained material, the worm was able to increase the BaP content of ingested sediment by 10–35% above that of the bulk material. During digestion, an average of 5–21% of the ingested BaP was absorbed from gut contents. The relative importance of ingestion as a route of BaP uptake was dependent on the time period of observation. Initial uptake of BaP was postulated to come from absorption of dissolved BaP across the body wall since, after short periods of exposure (<24 h), only 3–38% of observed BaP tissue concentrations could have been derived from ingested material. With time and with increased feeding activity, however, ingested sediment became the major source of BaP to the organism. After 72 h of exposure, 36–119% of the tissue BaP (mean = 77%) was estimated to have been derived from dietary absorption of ingested material, and with continued exposure the dietary route is likely to be as great or greater as the relative significance of the initial uptake from the dissolved phase diminishes. This work and other studies indicate that for many deposit feeders, ingested sediment can be the primary source for the bioaccumulation of hydrophobic toxicants.
Effects of Cadmium and Phenol on Motility and Ultrastructure of Sea Urchin and Mussel Spermatozoa by D. W. T. Au; M. W. L. Chiang; R. S. S. Wu (pp. 455-463).
Computer-assisted sperm analysis (CASA) was used to study the effects of Cd(II) and phenol on sperm motility of sea urchin and mussel. In parallel, ultrastructural changes of sperm induced by these two toxicants were also investigated and related to motility impairment. Spermatozoa of sea urchin were more sensitive than mussel spermatozoa to both toxicants. Sea urchin sperm motility showed a good dose-response relationship to Cd(II) levels as well as exposure time. Exposure to the two toxicants changed the size and shape of the midpiece, which might affect the balance of spermatozoa in their swimming. The plasma membrane became more convoluted, and such a change might affect the streamlining and integrity of spermatozoa and hinder their normal movement patterns. Most important, disorganization of mitochondrial membranes and cristae was observed, suggesting disruption of ATP supply for sperm movement. Cadmium also induced greater ultrastructural damages in sea urchin spermatozoa.
Polychlorinated Biphenyls and Metals in Marine Species from French Frigate Shoals, North Pacific Ocean by X.-S. Miao; C. Swenson; K. Yanagihara; Q. X. Li (pp. 464-471).
Polychlorinated biphenyls (PCBs) and metals were analyzed in coral (Porites lobata), fish (Stegastes fasciolatus), crab (Grapsus tenuicrustatus), and sediment samples collected from Tern Island, and the reference samples from Trig and La Perouse Islands. All three islands are part of French Frigate Shoals, a national wildlife refuge in the North Pacific Ocean. Average concentrations of total PCBs ranged from 154 to 274 ng/g in the sediments, from 120 to 267 ng/g in the corals, from 387 to 4,500 ng/g in the crabs, and 1,340 to 46,000 ng/g, dry weight, in the fishes. High concentrations in marine species indicate there is PCB source(s) in French Frigate Shoals, especially Tern Island. Tetra- and pentachlorobiphenyls were 64–66% of the total PCB levels in the sediments, and they accounted for 57–65% of total PCBs in the corals. Penta- and hexachlorobiphenyls were 76–84% of total PCBs in the fishes, and they accounted for 79–85% in the crab samples. The sediment and coral were predominated by lower chlorinated PCB congeners, whereas the fish and crab bioaccumulated mainly higher chlorinated congeners. Selenium concentrations (16–23 μg/g) in sediments were much higher than some reported baseline values (0.4–2.5 μg/g). The average concentrations of arsenic, cadmium, lead, and selenium in the coral and fish were about equal to or less than those in the sediments. Concentrations of arsenic and cadmium in the crabs (49–51 and 3–4 μg/g, respectively) were approximately twofold of those in the sediments.
Ultrastructural Localization of Heavy Metals (Hg, Ag, Pb, and Cu) in Gills and Digestive Gland of Mussels, Mytilus galloprovincialis (L.) by G. P. Domouhtsidou; V. K. Dimitriadis (pp. 472-478).
The intracellular localization of heavy metals using autometallography (AUM) was studied in the gills and the digestive gland of the common mussel Mytilus galloprovincialis, after an experimental exposure to 0.1 mg L−1 of Hg, 0.1 mg L−1 of Ag, 0.1 mg L−1 of Pb, and 0.1 mg L−1 of Cu for 98 days. In the gills, autometallographical black silver deposits (BSDs) were localized in the dense bodies observed in the apical and in the basal part of the cells. Among metals, Hg presented the highest accumulation, followed by Ag, Pb, and Cu. BSDs were more prominent in the abfrontal part of the gill filament in the case of Hg exposure and in the frontal part in the case of Ag and Pb exposure. In the digestive gland, Hg and Ag were localized in the heterolysosomes and the residual bodies of the digestive cells, as well as in the dense bodies of the basophilic cells. The heavy metal exposure also affected the gross morphology of the examined tissues and resulted in the fusion of residual bodies in the digestive cells, the fragmentation or vacuolization of the rough endoplasmic reticulum, and the increase in the number of granules in the basophilic cells. In the gills, fusion of the gill filaments was also noted.
Selenium Concentrations in the Colorado Pikeminnow (Ptychocheilus lucius): Relationship with Flows in the Upper Colorado River by B. C. Osmundson; T. W. May; D. B. Osmundson (pp. 479-485).
A Department of the Interior (DOI) irrigation drainwater study of the Uncompahgre Project area and the Grand Valley in western Colorado revealed high selenium concentrations in water, sediment, and biota samples. The lower Gunnison River and the Colorado River in the study area are designated critical habitat for the endangered Colorado pikeminnow (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus). Because of the endangered status of these fish, sacrificing individuals for tissue residue analysis has been avoided; consequently, little information existed regarding selenium tissue residues. In 1994, muscle plugs were collected from a total of 39 Colorado pikeminnow captured at various Colorado River sites in the Grand Valley for selenium residue analysis. The muscle plugs collected from 16 Colorado pikeminnow captured at Walter Walker State Wildlife Area (WWSWA) contained a mean selenium concentration of 17 μg/g dry weight, which was over twice the recommended toxic threshold guideline concentration of 8 μg/g dry weight in muscle tissue for freshwater fish. Because of elevated selenium concentrations in muscle plugs in 1994, a total of 52 muscle plugs were taken during 1995 from Colorado pikeminnow staging at WWSWA. Eleven of these plugs were from fish previously sampled in 1994. Selenium concentrations in 9 of the 11 recaptured fish were significantly lower in 1995 than in 1994. Reduced selenium in fish may in part be attributed to higher instream flows in 1995 and lower water selenium concentrations in the Colorado River in the Grand Valley. In 1996, muscle plugs were taken from 35 Colorado squawfish captured at WWSWA, and no difference in mean selenium concentrations were detected from those sampled in 1995. Colorado River flows during 1996 were intermediate to those measured in 1994 and 1995.
Ecotoxicological Assessment of Persistent Organic and Heavy Metal Contamination in Hong Kong Coastal Sediment by C. K. C. Wong; H. Y. Yeung; R. Y. H. Cheung; K. K. L. Yung; M. H. Wong (pp. 486-493).
The aim of the present project is to determine the feasibility of measuring hepatic cytochrome P4501A1 (CYP1A1) and metallothionein (MT) mRNA in fish as an integrative measurement of persistent organic pollutants (POPs) and heavy metal contamination in sediment arising in Hong Kong. Sediment samples were collected from different sites, including Victoria Harbour (VS6), Yim Tin Tsai (YTT) at Tolo Harbour, Mai Po marshes (MPM) at Deep Bay, and Southern Waters (SS6) of coastal waters. The samples were analyzed for total and extractable concentrations of Cd, Cu, Ni, Zn, and Pb, as well as PCBs and PAHs. In addition, biomarker responses were studied in tilapia exposed experimentally to coastal sediment for 7 days. Using RT-PCR technique, hepatic CYP1A1 and MT mRNA were measured. Three control groups were used, including one negative control group maintained in sea water only; the second and third positive control groups were in sea water but were intraperitoneally injected with either β-naphthoflavone (40 μg/g body weight) or cadmium chloride (10 μg/g body weight), respectively. The chemical data showed that VS6, YTT, and MPM were classified as Class C sediment according to the sediment quality criteria defined by the Hong Kong Environmental Protection Department, indicating the sites were heavily polluted. The exposure of tilapia to the sediment induced hepatic CYP1A1 (VS6 > YTT > MPM > SS6) and MT (VS6 > MPM > YTT > SS6) levels. The induction patterns were comparable to the levels of POPs and metal contamination in the sediment, indicating that the biomarker responses could be used to differentiate low to high levels of contamination among sediment.
Vitellogenin Induction and Other Biochemical Responses in Carp, Cyprinus carpio, After Experimental Injection with 17α-Ethynylestradiol by M. Solé; C. Porte; D. Barceló (pp. 494-500).
Prespawning, adult male and female carp, Cyprinus carpio, were intraperitoneally injected with a single dose of 500 μg/kg of 17α-ethynylestradiol (EE2). Blood samples were taken and vitellogenin levels were recorded previous to the injection and 8 days afterward. Western blot analysis of plasma VTG showed a marked response in both males (90-fold) and females (67-fold) after EE2 injection. Also, a significant inhibition of the cytochrome P450 monooxygenase system, namely, 7-ethoxyresorufin O-deethylase (EROD) activity, as well as immunodetected CYP1A protein was observed in the EE2-injected fish. Other cytochrome P450 isozymes, such as CYP3A or NADH cyt (b5) reductase, did not indicate any particular trend; whereas NADPH cyt (P450) reductase was significantly induced in EE2-injected animals. Total cytochrome P450, glutathion S-transferase (GST), and total glutathion peroxidase (GPX) fluctuated in a similar manner, but differences among treated and nontreated animals were not statistically significant. UDP glucuronyl transferase (UDPGT), similar to the antioxidant enzymes catalase, superoxide dismutase (SOD), and Se-GPX, progressively decreased in carrier and injected animals in comparison to the controls, although this trend did not reach statistical significance either.
Metals and Metalloids in Tissues of American Alligators in Three Florida Lakes by J. Burger; M. Gochfeld; A. A. Rooney; E. F. Orlando; A. R. Woodward; L. J. Guillette, Jr. (pp. 501-508).
Concentrations of metals and selenium were examined in tissues of American alligators (Alligator mississippiensis) from three lakes in central Florida, in one of which alligators have exhibited reproductive or developmental defects. Our overall objective was to determine whether the levels of metals were sufficiently high to confound the association between chlorinated hydrocarbons, which are elevated in eggs and juvenile plasma, and reproductive impairment. The concentrations of all metals were relatively low compared to those reported for alligators from elsewhere in Florida and the southeastern United States, suggesting that reproductive impairment is not due to metals and that metals pose no health risk to the alligators. We also wanted to determine whether skin, biopsied tail muscle, or tail tip tissue, all easily collected from live alligators, could be used as surrogate measures of internal tissue loads. Concentrations of arsenic, cadmium, chromium, lead, manganese, mercury, and selenium in liver were highly correlated with at least one of the three biopsied tissues. Only tin showed no significant positive correlation. No single tissue gave a high prediction of liver levels for all metals, although skin gave the highest correlation for mercury, and tail muscle gave the best overall correlation for lead and cadmium.
Toxic Assessment of PCBs by the 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Equivalent in Common Cormorant (Phalacrocorax carbo) from Japan by K. S. Guruge; S. Tanabe; M. Fukuda (pp. 509-521).
Common cormorants collected from three colonies and their fish diet were analyzed for PCB congeners and 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) were estimated. The highest total PCBs (40 μg/g wet weight) found in adult cormorants from Shinobazu Pond located in Central Tokyo, was sevenfold higher than that from Lake Biwa. IUPAC 153 was the most abundant congener in adults and eggs, whereas IUPAC 28 + 31 was higher in some chicks and exhibited growth-related congeneric enrichment. The estimated metabolic index (MI) for PCB congeners revealed that mono- and non-ortho coplanars had higher bioaccumulation in cormorant liver and were expected to cause toxic effects. Among non-ortho coplanars, IUPAC 126 was predominant, and total non-ortho coplanars and TEQs in cormorants were threefold higher in Shinobazu Pond than those from Lake Biwa. The non-ortho IUPAC 126 contributed a higher portion to the total TEQs followed by IUPAC 105 and IUPAC 77. The hepatic IUPAC 169/126 ratio increased significantly with TEQs, implying a potential induction of drug-metabolizing enzymes in Shinobazu Pond cormorants. Based on the available data, PCB contamination in cormorants is enough to pose sublethal effects, especially in Shinobazu Pond and Godaiba Island, Tokyo, Japan. This could be a reason for recently observed high chick and juvenile mortality in those colonies in Tokyo.
Mixed-Function Oxygenases, Oxidative Stress, and Chromosomal Damage Measured in Lesser Scaup Wintering on the Indiana Harbor Canal by T. W. Custer; C. M. Custer; R. K. Hines; D. W. Sparks; M. J. Melancon; D. J. Hoffman; J. W. Bickham; J. K. Wickliffe (pp. 522-529).
During the winter of 1993–1994, male lesser scaup (Aythya affinis) were collected on the heavily polluted Indiana Harbor Canal, East Chicago, Indiana, and examined for several bioindicators of chemical exposure. Livers were analyzed for activities of three cytochrome P450–associated monooxygenases and four measures of oxidative stress. Blood and spleen were analyzed by flow cytometry for chromosomal damage. In a concurrent study, scaup tissues were analyzed for organic and inorganic contaminants. Ethoxyresorufin-O-dealkylase (EROD) activity in livers of scaup collected in January 1994 was significantly higher than in livers of scaup collected in March 1994 or in livers of reference birds. Three hepatic monooxygenase activities were each significantly correlated with polycyclic aromatic hydrocarbon (PAH) concentrations in scaup carcasses. Thiobarbituric acid (TBA) activity in scaup livers was positively correlated with iron, boron, and lead concentrations in livers and polychlorinated biphenyl concentrations in carcasses. TBA activity was negatively correlated with protein-bound thiol activity and mercury concentrations in livers. The coefficient of variation of DNA content in scaup blood cells was correlated with PAH concentrations in scaup carcasses. This is the first field study with birds to demonstrate a correlation between liver monooxygenase activity and carcass PAH concentrations and to show a direct correlation between PAH concentrations in tissues and somatic chromosomal damage in blood.
Strychnine Alkaloid and Avian Reproduction: Effects Occur at Lower Dietary Concentrations with Mallard Ducks Than with Bobwhite Quail by C. A. Pedersen; R. T. Sterner; M. J. Goodall (pp. 530-539).
Separate subchronic reproductive toxicity studies were conducted using mallard ducks (Anas platyrhynchos) and northern bobwhite quail (Colinus virginianus). Three groups (32/group; 16 male-female pairs) of 17-week-old ducks (F0 generation) were fed Purina® Game Bird Breeder Layena® diets containing mean (±SD) 33.2 (±2.7), 68.9 (±1.8), and 140.9 (±5.1) μg/g strychnine for 20 weeks, with some pairs in each group fed control diet during a subsequent 3-week recovery period. Three groups (32/group; 16 male-female pairs) of 19-week-old quail (F0 generation) were fed similar diets containing mean (±SD) 279.2 (±10.1), 557.4 (±43.5), and 1,113.6 (±46.6) μg/g strychnine for 22 weeks without a recovery period. Separate groups of ducks and quail (32/group; 16 male-female pairs) were also fed control diets (0.0 μg/g strychnine) in each study. There were 16 weekly collections of eggs for the mallard study (13 for the diet-exposure period and 3 for the recovery period), and 11 collections for the quail study. Eggs laid during the last 13 and 10 weeks of the diet-exposure periods for ducks (plus 3 weeks of the recovery period) and quail, respectively, were incubated. Each hatch of F1 generation ducklings and chicks was observed for 14 days. Key results were: (1) the no observed adverse effect levels (NOAELs) for F0 ducks and quail were 33.2 and 1,113.6 μg/g strychnine, respectively—quail showed no reproductive effects at the current doses; (2) decreased egg production and hatching success occurred for mallard hens fed mean 140.9 μg/g strychnine diets; and (3) “normal-hatching” ducklings from eggs of F0 mallards fed mean 140.9 μg/g strychnine diets suffered greater mortality than ducklings from the other diet groups. Possible mechanisms of strychnine action on avian reproduction are discussed.
Sensitivity of a Standard Host Resistance Assay Using Streptococcus agalactiae for Assessing Exposure to Immunotoxicants in Wild Cotton Rats (Sigmodon hispidus) by L. C. Jones; R. L. Lochmiller; J. A. Sinclair; R. H. Morton (pp. 540-545).
Resident small mammals have been used for in situ biomonitoring of contaminated waste sites containing suspected immunotoxicants. Host resistance assays, which involve challenging animals with an actual pathogen, allow for testing of overall immune system function in animals. Because such assays have not been evaluated for use with wild rodent species, it was our objective to assess the efficacy of Streptococcus agalactiae as a pathogenic model for use in a host resistance assay for detecting alterations in immune system function in wild cotton rats (Sigmodon hispidus). The ability of the assay to detect immunosuppression was evaluated by inducing immunosuppression chemically (cyclophosphamide or dexamethasone) and by protein malnutrition. The estimated lethal dose of S. agalactiae that killed 50% of challenged animals (LD50) was 5.76 × 107 colony-forming units (CFUs). Although bacterial agglutination titers indicated that animals developed an antibody response when immunized, immunization was not sufficient to adequately protect animals from a subsequent pathogenic challenge. Sensitivity of the host resistance assay was only suitable for detecting substantial immunosuppression, such as that induced by protein malnutrition or dexamethasone administration.
Malathion Deposition, Metabolite Clearance, and Cholinesterase Status of Date Dusters and Harvesters in California by R. I. Krieger; T. M. Dinoff (pp. 546-553).
Date gardens in the Coachella Valley in California typically receive multiple treatments of malathion to control major insect pests. Variable amounts of malathion dust retention by skin and clothing and individual work behaviors limit the usefulness of clothing as an exposure dosimeter in date dusters and harvesters. To determine malathion absorption in workers, urine clearance of dimethyl phosphates (alkyl phosphates; AP) and malathion mono- (MCA) and di- (DCA) acids were estimated from date dusters (loaders/applicators) and harvesters (both on ground and high in trees). A series of self-administered doses of malathion were either ingested in gelatin capsules or applied to the volar surface of the forearm to guide biomonitoring. Each of the dimethyl phosphates (dimethylthio- > dimethyldithio > dimethyl-) and both malathion mono- and diacids were present in urine as soon as 2–3 h of work. On a micromole basis dimethylthiophosphate and the malathion acids (MCA > DCA) were the most prominent metabolites in urine. Applicator exposures ranged from 95–210 mg equivalents per day (1–3 mg/kg-day). Harvester exposures ranged from 1–270 μg/kg-day. Mid-season Monday morning urine specimens before work contained low or unmeasurable levels of malathion acids, indicating that malathion is rapidly metabolized and cleared from the body in the urine. Saliva was not useful for biomonitoring. No inhibition of cholinesterase activity was measured in any members of two separate crews of harvesters who had previous prolonged dust exposure (1 and 2 months).