Substituted 3-phenylpropenoates and related analogs: electron ionization mass spectral fragmentation and density functional theory calculations.

Analysis of ethyl 3-(2-chlorophenyl)propenoate by electron ionization mass spectrometry showed the distinct loss of an ortho chlorine. To characterize the structural requisites for the observed mass fragmentation, a series of 30 halogen-substituted 3-phenylpropenoate-related structures were examined. All ester-containing alkene derivatives exhibited loss of the distinctive chlorine from the 2-position of the phenyl ring. Analogous derivatives with the halogen (chlorine or bromine) in the para position did not evidence selective halogen loss. Results demonstrated that substituted 3-phenylpropenoates and their analogs fragment via the formation of a previously reported benzopyrylium intermediate. To understand the correlation between the intramolecular radical substitution and the abundance and selectivity of the chlorine (or other halogen) displacement, density functional theory calculations were performed to determine the charge on the principal cation involved in the chlorine loss (in the ortho, meta, and para positions), the charge for the neutral radical (noncation), the excess alpha-electron density on the relevant atom and the energy to form the cation from the neutral atom (ionization energy). Results showed that the selectivity and extent of halogen displacement correlated highly to the electrophilicity of the radical cation as well as the neutral radical. These data further support the proposed fragmentation mechanism involving intramolecular radical elimination.

Development of a class-selective enzyme-linked immunosorbent assay for mercapturic acids in human urine.

Epidemiological and toxicological studies often require the analysis of large numbers of samples for biological markers of exposure. The goal of this work was to develop a class-selective ELISA to detect groups of structurally closely related mercapturic acids with small nonpolar S-substituents. An assay was developed with strong recognition for mercapturates including S-benzylmercapturic acid (IC50 = 0.018 micromol/L), S-n-hexylmercapturic acid (IC50 = 0.021 micromol/L), S-phenylmercapturic acid (IC50 = 0.024 micromol/L), and S-cyclohexylmethylmercapturic acid (IC50 = 0.042 micromol/L). The same assay also showed weaker recognition for S-(1-hydroxynaphthal-2-yl)mercapturic acid and S-allylmercapturic acid (IC50 = 1.1 and 1.7 micromol/L, respectively). Subtle modifications to the hapten linker structure of the coating antigen proved to have a strong impact on the selectivity and the specificity of the assay. A slightly modified assay showed high recognition for S-benzylmercapturic acid (IC50 = 0.018 micromol/L) and weaker recognition for seven other mercapturic acids (IC50 = 0.021-10 micromol/L). Strong positive assay responses were detected in 12 urine samples obtained from persons with no known occupational exposure to exogenous electrophilic xenobiotics. Solid phase extraction and cross-reactivity indicated that the presumptive immunoreactive materials were similar in size and polarity to S-benzylmercapturic acid. The assay was more selective to mercapturic acids than the spectrophotometric thioether assay.

Identification of lumichrome as a sinorhizobium enhancer of alfalfa root respiration and shoot growth.

Sinorhizobium meliloti bacteria produce a signal molecule that enhances root respiration in alfalfa (Medicago sativa L.) and also triggers a compensatory increase in whole-plant net carbon assimilation. Nuclear magnetic resonance, mass spectrometry, and ultraviolet-visible absorption identify the enhancer as lumichrome, a common breakdown product of riboflavin. Treating alfalfa roots with 3 nM lumichrome increased root respiration 21% (P < 0.05) within 48 h. A closely linked increase in net carbon assimilation by the shoot compensated for the enhanced root respiration. For example, applying 5 nM lumichrome to young alfalfa roots increased plant growth by 8% (P < 0.05) after 12 days. Soaking alfalfa seeds in 5 nM lumichrome before germination increased growth by 18% (P < 0.01) over the same period. In both cases, significant growth enhancement (P < 0.05) was evident only in the shoot. S. meliloti requires exogenous CO2 for growth and may benefit directly from the enhanced root respiration that is triggered by lumichrome. Thus Sinorhizobium-alfalfa associations, which ultimately form symbiotic N2-reducing root nodules, may be favored at an early developmental stage by lumichrome, a previously unrecognized mutualistic signal. The rapid degradation of riboflavin to lumichrome under many physiological conditions and the prevalence of riboflavin release by rhizosphere bacteria suggest that events demonstrated here in the S. meliloti-alfalfa association may be widely important across many plant-microbe interactions.

Potent urea and carbamate inhibitors of soluble epoxide hydrolases.

The soluble epoxide hydrolase (sEH) plays a significant role in the biosynthesis of inflammation mediators as well as xenobiotic transformations. Herein, we report the discovery of substituted ureas and carbamates as potent inhibitors of sEH. Some of these selective, competitive tight-binding inhibitors with nanomolar K(i) values interacted stoichiometrically with the homogenous recombinant murine and human sEHs. These inhibitors enhance cytotoxicity of trans-stilbene oxide, which is active as the epoxide, but reduce cytotoxicity of leukotoxin, which is activated by epoxide hydrolase to its toxic diol. They also reduce toxicity of leukotoxin in vivo in mice and prevent symptoms suggestive of acute respiratory distress syndrome. These potent inhibitors may be valuable tools for testing hypotheses of involvement of diol and epoxide lipids in chemical mediation in vitro or in vivo systems.

Development of a highly sensitive enzyme-linked immunosorbent assay based on polyclonal antibodies for the detection of polychlorinated dibenzo-p-dioxins.

The development of an enzyme-linked immunosorbent assay (ELISA) based on polyclonal antibodies for the polychlorinated dibenzo-p-dioxins is described. We previously reported the synthesis of haptens and generation of antibodies for detection of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Antisera were screened with seven different coating antigens (hapten-protein conjugates), including trans-3-(7,8-dichlorodibenzo-p-dioxin-2-yl)-cis-2-methylpropeno ic acid (VII) and 5-(3,7,8-trichlorodibenzo-p-dioxin-2-yl)penta-trans,trans-2,4-dien oic acid (X). All inhibition screening and optimization studies were conducted using a less toxic surrogate standard for TCDD [2,3,7-trichloro-8-methyl-dibenzo-p-dioxin (TMDD; XVII)] which responded similarly to 2,3,7,8-TCDD in the ELISA. The most sensitive assay from the screening studies [coating antigen VII-BSA, 0.1 microgram/mL, and antiserum 7598 (anti-X-LPH), 1:10,000] was further optimized and characterized. It exhibited an IC50 value of 12 pg/well (240 pg/mL), with working range from 2 to 240 pg/well (40 to 4800 pg/mL). The influence of various physical and chemical factors (time, solvent, detergent) was investigated. The optimized assay was then used to assess cross-reactivity by congeners of halogenated dioxins and related structures. DMSO up to concentrations of 37.5% decreased the IC50 value in the assay, whereas methanol to concentrations of 30% did not lead to improved IC50 values.

Monitoring the pesticide-exposed worker.

Cholinesterase inhibitors-the organophosphates and the carbamates-are the most acutely toxic and widely used insecticides. They also comprise the only group of pesticides for which state laws exit requiring worker monitoring. This chapter focuses on cholinesterase monitoring, with attention to available assays and testing kits.

Rapid assays for environmental and biological monitoring.

Rapid, inexpensive, sensitive, and selective enzyme-linked immunosorbent assays (ELISAs) now are utilized in environmental science. In this laboratory, many ELISAs have been developed for pesticides and other toxic substances and also for their metabolites. Compounds for which ELISAs have recently been devised include insecticides (organophosphates, carbaryl, pyrethroids, and fenoxycarb), herbicides (s-triazines, arylureas, triclopyr, and bromacil), fungicides (myclobutanil), TCDD, and metabolites of naphthalene and toluene. New rapid assays have been developed for mercury.

Long vs. short monitoring intervals for peach harvesters exposed to foliar azinphos-methyl residues.

A dermal monitoring study of peach harvesters exposed to azinphos-methyl (AM) residues was conducted in Sutter County, California. Harvesters were paid by piecework, which allowed characterization of the relationship between dermal exposure (DE) and time or production. Workers wore 2 long-sleeved knit T-shirts for each monitoring interval and also provided a hand residue sample. Dislodgeable foliar residue (DFR) samples were also collected. The highest correlations were found for inner shirts vs. production and DE vs. time worked (r2 = 0.67, P < 0.01). DE was greatest after 2-h exposures and reached equilibrium after 3 h, indicating that exposure estimates from shorter intervals would overestimate exposure.

Assessment of azinphosmethyl exposure in California peach harvest workers.

We compared measurements of urinary alkylphosphate metabolites and oxime-induced reactivation of plasma cholinesterase (P-ChE) and erythrocyte acetylcholinesterase (RBC-AChE) with measurements of foliar residues, skin and clothing contamination, and P-ChE and RBC-AChE activities among 20 Northern California peach orchard workers exposed to the organophosphate agent azinphosmethyl (Guthion). Subjects entered orchards treated 30 d previously with azinphosmethyl and worked 21 d in treated fields during the ensuing 6 wk. Dislodgeable foliar residues ranged from 0.32-0.96 micrograms/cm2. Median reduction in RBC-AChE activity was 7% (p < .001) over the initial 3-d period of exposure and 19% (p < .01) over the 6-wk season. Urinary metabolites were the most sensitive indicator of recent exposure and correlated moderately with dermal and clothing levels (rs = +0.31-(+)0.55); urinary metabolites correlated well with RBC-AChE drawn 3 d after exposure began (rs = -0.77). No significant oxime-induced reactivation was found.

The effect of organophosphates on a chicken brain or sea urchin egg kinesin-driven microtubule motility assay.

The effect of neuropathic and non-neuropathic organophosphates (OPs) and acrylamide on an in vitro kinesin-driven microtubule (MT) motility assay was compared. The goal of the study was to determine whether this in vitro assay could confirm that a mechanism of action of neuropathic OPs was to impair kinesin activity and, therefore, possibly fast axonal anterograde transport (FAAT) in vivo. For our study, kinesin from chicken brain (CK) and sea urchin egg (SUK) was initially purified. Western immunoblotting confirmed the close antigenic homology between CK and SUK, using a mouse monoclonal sea urchin kinesin heavy chain-specific antibody (SUK 4). In the presence of microtubules (MTs) and MgATP, both CK- and SUK-driven MT movement was measured using a video-enhanced differential interference contrast microscope system with computer-assisted analysis. Using this assay system, we then tested separately the effect of two neuropathic OPs (diisopropylfluorophosphate (DFP) and phenyl saligenin phosphate (PSP)) and a non-neuropathic OP (paraoxon (PO)) each at a concentration of 10(-2) M at 27 degrees C. Additionally, we tested acrylamide (10(-2) M), since it is one of the best-characterized neurotoxins impairing FAAT in vivo. Our results demonstrated that none of these compounds significantly affected kinesin-driven MT motility in vitro compared to the standard controls. Further, this assay system was thus not able to discriminate between the neuropathic and non-neuropathic effect of these OPs.

Chlorothalonil exposure of workers on mechanical tomato harvesters.

Worker exposure to chlorothalonil (tetrachloroisophthalonitrile, Bravo during mechanical tomato harvester operations of fruit for processing was estimated from passive dermal dosimetry monitoring (gauze pad and undershirt dosimetry), air concentration measurements and hand washes. Gauze pad dosimeters placed outside of workers' clothing gave an average potential dermal exposure of 499.6 micrograms/h. Dermal exposure based on undershirt dosimetry averaged 43.4 micrograms/h. Air concentrations ranged from 0.002-0.02 microgram/l. Dislodgeable fruit residues were measured and used to develop transfer factors (cm2 h) for both the pad dosimetry (450) and shirt dosimetry (40). Study results indicate that normal work clothing provides a 90% reduction in dermal exposure to chlorothalonil and that contribution of inhalation to total exposure ranges from 8.1-28%.

Aryl-Substituted alpha-Aminooxycarboxylic Acids: A New Class of Auxin Transport Inhibitors.

Certain herbicidal aminooxyisovalerate analogs were noted in whole plant phytotoxicity bioassays to cause disoriented roots. Since this symptom is often characteristic of interference with the transport of the plant hormone auxin, the ability of several of these compounds to compete for the N-1-naphthylphthalamic acid (NPA) binding site in corn (Zea mays L.) coleoptile membranes was measured. Significant NPA binding activity was found, expecially for the 2,4-dichlorophenyl analog. Application of structure-activity principles from traditional auxin transport inhibitors to this new class of molecules led to the synthesis of the naphthyl analogue. This molecule was extremely active in competing for NPA binding and in eliciting whole plant growth regulator effects. Possible relationships between these molecules and the mode of auxin transport are discussed.

Amniotic rupture, extra-amniotic pregnancy, and vernix granulomata.

is report describes two cases of amniotic rupture with delivery of live-born infants; one at 31 weeks and the other at term. The size of these amniotic sacs was apparently inadequate to contain the fetus, and extra-amniotic pregnancy was considered to have occurred. The ruptured and separated amniotic sacs were larger than previously reported examples and resembled those of delivery artifact. However, both placentas contained vernix granulomata in the separated amniotic mesenchyme and in the denuded mesenchyme of the chorionic plates, confirming the diagnosis of antepartum amniotic rupture. These observations add significant diagnostic criteria for identifying this entity in the absence of the hitherto commonly associated fetal amniotic band syndrome. Regardless of presence or absence of amniotic band syndrome, this entity is a sporadic condition, and recurrence is extremely rare in subsequent pregnancies.

Plasticizers in the environment: the fate of di-N-octyl phthalate (DOP) in two model ecosystems and uptake and metabolism of DOP by aquatic organisms.

The fate of the plasticizer, di-n-octyl phthalate (DOP) has been examined in 33-day terrestrial-aquatic and three-day aquatic model ecosystems. The five organisms of the two systems contained residues of DOP, demonstrating the propensity of this lipoid soluble organic molecule to be concentrated from the water. The residues in the organisms in the three-day system were higher than in the 33-day system with the exception of the fish, indicating perhaps, that DOP can undergo some degradation before the fish is placed in the system on the 30th day. A half-life of five days for DOP disappearance from the water was calculated from water samples taken periodically. Further, effects of mixed function oxidase and esterase inhibitors were investigated on the metabolism of DOP by various selected organisms and tissues of the two ecosystems.

Laboratory model ecosystem studies of the degradation and fate of radiolabeled tri-, tetra-, and pentachlorobiphenyl compared with DDE.

Radiolabeled tri-, tetra-, and pentachlorobiphenyls (PCB) and DDE were studied in a laboratory model ecosystem for degradation pathways, and biomagnification in alga, snail, mosquito, and fish. Trichlorobiphenyl was degraded in all the organisms of the model ecosystem much more rapidly than tetrachloro- and pentachlorobiphenyl. Pentachlorobiphenyl was approximately as persistent as DDE. There was a linear relationship between lipid/water partition and ecological magnification and between water solubility and ecological magnification. No evidence of conversion of DDE to PCB was detected.