Abstract  Dicationic guanidine, N-alkylguanidine, and reversed amidine derivatives of fused ring systems have been synthesized from their corresponding bis-amines. DNA binding studies suggest that the diguanidines and the N-alkyl diguanidines fluorenes bind in the minor groove in a manner similar to that of the previously reported dicationic carbazole derivatives. The diguanidines and the N-alkyl diguanidines showed promising in vitro activity against both Trypanosoma brucei rhodesiense and Plasmodium falciparum. Promising in vivo biological results were obtained for the dicationic N-isopropylguanidino-9H-fluorene, giving 4/4 cures of the treated animals in the STIB900 animal model for African trypanosomiasis. The N-methyl analogue showed high activity as well. In addition, with the goal of enhancing the oral bioavailability, two novel classes of potential guanidine prodrugs were prepared. The N-alkoxyguanidine derivatives were not effective as prodrugs. In contrast, a number of the carbamates showed promising activity. The value of the carbamate prodrugs was clearly demonstrated by the results, which gave 4/4 cures on oral administration in the STIB900 mouse model.

Abstract  This paper presents a framework for integrated probabilistic risk assessment of chemicals in the diet which accounts for the possibility of cumulative exposure to chemicals with a common mechanism of action. Variability between individuals in the population with respect to food consumption, concentrations of chemicals in the consumed foods, food processing habits and sensitivity towards the chemicals is addressed by Monte Carlo simulations. A large number of individuals are simulated, for which the individual exposure (iEXP), the individual critical effect dose (iCED) and the ratio between these values (the individual margin of exposure, iMoE) are calculated by drawing random values for all variable parameters from databases or specified distributions. This results in a population distribution of the iMoE, and the fraction of this distribution below 1 indicates the fraction of the population that may be at risk. Uncertainty in the assessment is treated as a separate dimension by repeating the Monte Carlo simulations many times, each time drawing random values for all uncertain parameters. In this framework, the cumulative exposure to common mechanism chemicals is addressed by incorporation of the relative potency factor (RPF) approach. The framework is demonstrated by the cumulative risk assessment of organophosphorus pesticides (OPs). By going through this example, the various choices and assumptions underlying the cumulative risk assessment are made explicit. The problems faced and the solutions chosen may be more generic than the present example with OPs. This demonstration may help to familiarize risk assessors and risk managers with the somewhat more complex output of probabilistic risk assessment.

Abstract  Background levels of exocyclic DNA adducts detected by ultrasensitive methods in tissues from unexposed humans and rodents arise from endogenous lipid peroxidation products such as trans-4-hydroxy-2-nonenal, crotonaldehyde and malondialdehyde. The levels of DNA adducts in rodent and human tissues and leukocytes were found to be highly variable and to be affected by lifestyle, the dietary intake of antioxidants and the type and amount of fatty acids and persistent chronic infections or inflammations, in which nitric oxide is often over-produced. Limited evidence suggests that etheno-DNA adducts play a role not only in vinyl chloride- and urethane-induced tumorigenesis but, together with other exocyclic lesions, also in several human cancers in which persistent oxidative stress leads to malignancy by increasing mutation rates and genomic instability. Therefore, promutagenic exocyclic adducts appear to be promising markers in molecular epidemiological studies for identifying endogenous sources of DNA damage and resulting oxidative modifications in cancers with poorly defined etiology and mechanisms and in intervention studies to assess the protective effects of antioxidants against cancer and, possibly, neurodegenerative diseases.

Abstract  The title compound, C(4)H(10)NO(+)·C(5)H(8)NOS(2) (-), is built up of a morpholinium cation and a dithio-carbamate anion. In the crystal, two structurally independent formula units are linked via N-H⋯S hydrogen bonds, forming an inversion dimer, with graph-set motif R(4) (4)(12).

Abstract  We herein outline the design of a new series of agonists of the pancreatic and GI-expressed orphan G-protein coupled receptor GPR119, a target that has been of significant recent interest in the field of metabolism, starting from our prototypical agonist AR231453. A number of key parameters were improved first by incorporation of a pyrazolopyrimidine core to create a new structural series and secondly by the introduction of a piperidine ether group capped with a carbamate. Chronic treatment with one compound from the series, 3k, showed for the first time that blood glucose and glycated hemoglobin (HbA1c) levels could be significantly reduced in Zucker Diabetic Fatty (ZDF) rats over several weeks of dosing. As a result of these and other data described here, 3k (APD668, JNJ-28630368) was the first compound with this mechanism of action to be progressed into clinical development for the treatment of diabetes.

Abstract  In this work multifunctional sorbents, based on surfactant-coated mineral oxides, are assessed for the simultaneous extraction/preconcentration of pesticide multiresidues from aqueous environmental samples. Seventeen pesticides, representative of all the common groups (triazines, phenylureas, carbamates, azols, anilides, chloroacetanilides, organophosphorous, phenoxyacids, aryloxy acids and phenols), are selected for this study. The sorbents assessed are pure sodium dodecyl sulphate (SDS) and mixed tetrabutylammonium (TBA)-SDS hemimicelles and/or admicelles adsorbed onto alumina. Because of their multifunctional character, these sorbents provide different retention mechanisms (i.e. hydrophobic, ionic and/or pi-cation interactions), which highly contribute to the efficient retention of pesticides with different polarities and acidities (bases, neutrals and acids). In addition, the low volume of eluent required for complete elution of analytes (typically 1-2mL) avoided the need of using time-consuming and tedious evaporation steps that generally are needed when cross-linked polymeric resins or carbon materials are used as sorbents. The performance of two sorbents, i.e. SDS and TBA-SDS mixed hemimicelles/admicelles, for the admicellar solid-phase extraction (ASPE) of pesticide multiresidue was comparatively investigated. The latter was selected on the basis of the higher breakthrough volumes permitted, the lower volume of eluent required and the higher sample and eluent flow rates allowed. The proposed ASPE/LC/UV approach provided detection limits lower than 100 ngL(-1) for the determination of the 17 pesticides tested. Recoveries from spiked (at the ngL(-1) level) river and underground water samples was quantitative for most of the pesticides tested.

Abstract  Black band disease (BBD) of corals is a complex pathogenic polymicrobial mat community that lyses coral tissue as it migrates over an infected colony. Two known toxins are produced by BBD microorganisms - sulfide, produced by sulfate-reducing bacteria, and microcystin, produced by cyanobacteria. Experiments were carried out to determine the effects of exposing healthy coral fragments to variable concentrations of purified microcystin, sulfide at a concentration known to exist in BBD, and a combination of the two. Healthy fragments of the coral Montastraea annularis were placed into experimental chambers with known toxin/s for 18-22.5 h. Fine structural analysis using scanning electron microscopy (SEM) showed that toxin exposure resulted in thinning or removal of the coral epidermal layer coupled with degradation of the gastrodermis. These effects were exacerbated when both toxins were used in combination. Exposure to sulfide and the highest concentration of microcystin caused zooxanthellae to dissociate from the coral tissue and to form clusters on the coral surface. Examination of coral fragments infected with BBD was carried out for comparison. It was determined that the effects of exposure to sulfide and microcystin on coral fine structure were consistent, both quantitatively and qualitatively, with the effects of artificially induced and naturally occurring BBD on M. annularis.

Abstract  A novel GPR119 agonist based on the 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazole scaffold was designed through lead optimization starting from pyrazole-based GPR119 agonist 1. The design is centered on the conformational restriction of the core scaffold, while minimizing the change in spatial relationships of two key pharmacophoric elements (piperidine-carbamate and aryl sulfone).

Abstract  A multiclass method has been developed for screening, quantification and confirmation of organic micro-pollutants in water by gas chromatography coupled to mass spectrometry with a triple quadrupole analyzer. The work has been focused on the determination of more than 50 compounds belonging to different chemical families: 19 organochlorine and organophosphorus insecticides, 6 herbicides, 7 polychlorinated biphenyls, 16 polycyclic aromatics hydrocarbons, 2 brominated diphenyl ethers, and 3 octyl/nonyl phenols and pentachlorobenzene. Most of these analytes are included in the list of priority substances in the framework on European Water Policy. Analyte extraction was performed by solid phase extraction using C18 cartridges, and five isotopically labeled standards were added before extraction as surrogates. Analyses were performed by gas chromatography with tandem mass spectrometry (MS/MS) in electron impact mode. Accuracy and precision were evaluated by means of recovery experiments using water samples fortified at two concentration levels (25 and 250 ng L(-1)), with satisfactory results for most of analytes. The excellent selectivity and sensitivity reached in selected reaction monitoring mode allowed us satisfactory quantification and confirmation at levels as low as 25 ng L(-1). Two MS/MS transitions were acquired for each analyte, using the Q/q intensity ratio as a confirmatory parameter. The method developed was applied to the analysis of surface, ground and wastewater samples collected from the Valencia Region (Spain). Analytical methodology using negative chemical ionization mode was also validated for the organochlorine compounds selected, showing a superior sensitivity and lower detection limits.

Abstract  In vivo and/or in vitro mammalian cell systems were used to evaluate sister chromatid exchange (SCE) induction and gene mutagenesis effects following exposure to ethyl carbamate (urethane), vinyl carbamate, ethyl N-hydroxycarbamate, and 2-hydroxyethyl carbamate. Although ethyl carbamate caused dose-dependent increases in SCE when injected into mice, it was ineffective for inducing SCE and gene mutation (6-thio-guanine resistance) in Chinese hamster V-79 cells cultured with or without the addition of S9 enzyme mix during treatment. Chemical-specific patterns of genotoxicity were evident for the known or suspect metabolites under test: only vinyl carbamate consistently (in vivo and in vitro) revealed strong activity for the genetic endpoints. SCE induction levels of 5-8 times baseline were observed after animal or cell culture exposures to vinyl carbamate. Doses required to produce this effect in V-79 cells in the presence of S9 mix were approximately 100 times lower than those needed when S9 was absent. The extensive gene mutagenesis (approaching 600 mutants/10(6) survivors) noted was completely dependent upon the presence of S9 mix. These observations are consistent with current theory holding that vinyl carbamate is a metabolic intermediate of ethyl carbamate, and is converted to the ultimately reactive species (presumably, vinyl carbamate epoxide) which is responsible for ethyl carbamate carcinogenesis.

Abstract  The potent bacterial mutagen 2-chloroacrolein is formed from the carcinogenic herbicide S-2,3-dichloroallyl diisopropylthiocarbamate (diallate) on incubation with hepatic microsomal monooxygenases or on reaction with m-chloroperbenzoic acid. A proposed activation mechanism for this promutagen involves sulfoxidation followed by [2,3] sigmatropic rearrangement and 1,2-elimination reactions. A portion of the highly reactive intermediate, diallate sulfoxide (proximate mutagen), is attacked by glutathione in a reaction which competes with its transformation to the ultimate mutagen, 2-chloroacrolein.

Abstract  A series of novel sulfamides incorporating the dopamine scaffold were synthesized. Reaction of amines and tert-butyl-alcohol/benzyl alcohol in the presence of chlorosulfonyl isocyanate (CSI) afforded sulfamoyl carbamates, which were converted to the title compounds by treatment with trifluoroacetic acid or by palladium-catalyzed hydrogenolysis. Inhibition of six α-carbonic anhydrases (CAs, EC 4.2.1.1), that is, CA I, CA II, CA VA, CA IX, CA XII and CA XIV, and two β-CAs from Candida glabrata (CgCA) and Mycobacterium tuberculosis (Rv3588) with these sulfamides was investigated. All CA isozymes were inhibited in the low micromolar to nanomolar range by the dopamine sulfamide analogues. K(i)s were in the range of 0.061-1.822 μM for CA I, 1.47-2.94 nM for CA II, 2.25-3.34 μM for CA VA, 0.041-0.37 μM for CA IX, 0.021-1.52 μM for CA XII, 0.007-0.219 μM for CA XIV, 0.35-5.31 μM for CgCA and 0.465-4.29 μM for Rv3588. The synthesized sulfamides may lead to inhibitors targeting medicinally relevant CA isoforms with potential applications as antiepileptic, antiobesity antitumor agents or anti-infective.

Abstract  BIOSIS COPYRIGHT: BIOL ABS. An automatized procedure has been developed for the spectrophotometric determination of ethiofencarb in water by reaction with p-aminophenol after alkaline hydrolysis to obtain the corresponding phenol sulphone. The hydrolyzed samples are continuously introduced into different manifolds at the same time as 300 mg/lp-aminophenol, 0.004 mol/l KIO4 and 0.04 mol/l NaOH solutions. The absorbance is measured at 638 nm after a reaction time of 6 min in stop flow. This absorbance band corresponds to the indo dye obtained from the reaction between the phenol sulphone of ethiofencarb and the quinoneimine form of the p-aminophenol and it permits a matrix-free spectrophotometric determination of ethiofencarb with a limit of detection of 33 mug/l. The recovery of ethiofencarb in different water matrices varies from 71 to 126%.

Abstract  New bis (pyridylurea) ligand, H2L, was synthesized by the reaction of ethylpyridine-2-carbamate (EPC) and p-phenylenediamine. The ligand was characterized by elemental analysis, IR, (1)H NMR, electronic and mass spectra. Reaction of the prepared ligand with Co(2+), Ni(2+), Cu(2+), Fe(3+), VO(2+) and UO2(2+) ions afforded mono, bi- and trinuclear metal complexes. Also, new mixed ligand complexes of the ligand H2L and 8-hydroxyquinoline (8-HQ) with Co(2+), Ni(2+), Cu(2+) and Fe(3+) ions were synthesized. The ligand behaves as bi- and tetradentate toward the transition metal ions, coordination via the pyridine N, the carbonyl O and/or the amidic N atoms in a non, mono- and bis-deprotonated form. The complexes were characterized by elemental and thermal analyses, IR, electronic and mass spectra as well as conductance and magnetic susceptibility measurements. The results showed that the metal complexes exhibited different geometrical arrangements such as square planar, tetrahedral, octahedral and square pyramidal arrangements. The Coats-Redfern equation was used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. 3D molecular modeling of the ligand, H2L and a representative complex were studied.

Abstract  A novel sample preparation method, "water with low concentration of surfactant in dispersed solvent-assisted emulsion dispersive liquid-liquid microextraction (WLSEME)", coupled with gas chromatography using an electron capture detector (GC-ECD) was developed for the analysis of the organochlorine pesticides (OCPs), heptachlor, α-endosulfan, 4,4-DDE, 2,4-DDD and endrin, in aqueous samples. A microsyringe is used to withdrew and discharge 10-12μL of the extraction solvent and 60-120μL of water as the dispersed solvent (containing 1mgL(-1), Tween 80) 4 times within 10s to form a cloudy emulsified solution in the syringe. This is then injected into an 8mL aqueous sample spiked with all above OCPs. Dodecyl acetate and 2-dodecanol were both selected as extraction solvents to optimize their conditions separately. The total extraction time was about 0.5min. Under optimum conditions, using dodecyl acetate (12μL) as extraction solvent, the linear range of the method was 10-1000ngL(-1) for all OCPs, and the the limits of detection (LODs) ranged from 1 to 5ngL(-1). The absolute recoveries and relative recoveries were from 20.8 to 43.5% and 83.2 to 109.8% for lake water, and 19.9-49.2% and 85.4-115.9% for seawater respectively. In the second method, 2-dodecanol as extraction solvent, the linear range was from 5 to 5000ngL(-1) for the target compounds, and the LODs were between 0.5 and 2ngL(-1). The absolute recoveries and relative recoveries ranged from 25.7 to 42.2% and 96.3-111.2% for sea water, and 22.4-41.9% and 90.7-107.9% for stream water. This could solve several problems, which commonly occur in ultrasound-assisted emulsification micro-extraction (USAEME), dispersive liquid-liquid micro-extraction (DLLME) and other assisted emulsification methods. These problems include analyte degradation, increased solubility of the extraction solvent and analyte, and high toxicity and large volume of the organic solvent used.

Abstract  A new kind of milli-sized sorbent-calcium alginate supporting a weak acidic pink red B (APRB)-calcium fluoride nano-sized hybrid-was prepared. The micro-structure of the hybrid and adsorbent were characterized, and its adsorption capacity for organic contaminants, e.g. dyes, PCBs and microcystin (MC)-LR, was investigated. Cationic dyes were adsorbed selectively via charge attraction, with a saturation capacity of 188 mg of cationic red 3R per gram of the milli-sized adsorbent. However, the adsorptions of PCBs and MC-LR corresponded to the octanol-water partition law, and their partition coefficients were calculated to be 7788.6 mg kg(-1) for PCB029, 13325 mg kg(-1) for PCB101, 434.6 mg kg(-1) for PCB180, and 369.2 mg kg(-1) for MC-LR. When the milli-sized adsorbent was used in the treatment of two concentrated dye wastewaters and two polluted ground waters, the removal of the colored substances, chemical oxygen demand (COD), and concentration of PCBs and MC-LR were satisfactory. In the synthesis of the materials, all of the reactants are easily available and harmless to the environment, and APRB may be obtained from concentrated APRB-containing wastewater instead. The development of the milli-sized hybrid adsorbent provided liquid-solid separation, for favorable use in engineering. It will play an important role in the treatment of concentrated wastewater and the remediation of ground water contamination.

Abstract  The piperidine ring of the title compound, C15H25N3O3, adopts a slightly distorted chair conformation with the cis substituents displaying an N-C-C-C torsion angle of 43.0 (3)°. The cyano group (plane defined by C-C-C N atoms) is bent slightly out of the plane of the amide group by 13.3 (2)°. The carbamate group is oriented at a dihedral angle of 60.3 (5)° relative to the amide group.

Abstract  In order to develop a novel and useful building block for the development of radiotracers for positron emission tomography (PET), we studied the radiolabelling of 1,4-disubstituted 3-[(18)F]fluoropiperidines. Indeed, 3-fluoropiperidine became a useful building block in medicinal chemistry for the pharmacomodulation of piperidine-containing compounds. The radiofluorination was studied on substituted piperidines with electron-donating and electron-withdrawing N-substituents. In the instance of electron-donating N-substituents such as benzyl or butyl, configuration retention and satisfactory fluoride-18 incorporation yields up to 80% were observed. In the case of electron-withdrawing N-substituents leading to carbamate or amide functions, the incorporation yields depend on the 4-susbtitutent (2 to 63%). The radiolabelling of this building block was applied to the automated radiosynthesis of NR2B NMDA receptor antagonists and effected by a commercially available radiochemistry module. The in vivo evaluation of three radiotracers demonstrated minimal brain uptakes incompatible with the imaging of NR2B NMDA receptors in the living brain. Nevertheless, moderate radiometabolism was observed and, in particular, no radiodefluorination was observed which demonstrates the stability of the 3-position of the fluorine-18 atom. In conclusion, the 1,4-disubstituted 3-[(18)F]fluoropiperidine moiety could be of value in the development of other radiotracers for PET even if the evaluation of the NR2B NMDA receptor antagonists failed to demonstrate satisfactory properties for PET imaging of this receptor.

Abstract  The antioxidant potential of organoselenium compounds has been extensively investigated because oxidative stress is a hallmark of a variety of human diseases. In this study, we report the influence of substituent groups on the antioxidant activity of (R)-Se-aryl thiazolidine-4-carboselenoate (Se-PTC) in several in vitro assays. The amino group in the thiazolidine ring affects the antioxidant activity of the compound. Our data revealed that Se-PTC a had higher radical scavenging efficiency in the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS(+)) assays compared to other compounds. In the ferric ion reducing antioxidant power (FRAP) assay, Se-PTC a exhibited ferric-reducing ability at concentrations as low as 5μM. However, this effect was diminished when the amino group was protected with carbamate (Se-PTC d). In the nitric oxide scavenging assay, Se-PTC c presented better NO-scavenging than Se-PTC b. However, Se-PTC a and d did not prevent NO formation at any of the tested concentrations. Se-PTC c decreased the sodium nitroprussate-induced lipid peroxidation in the cortex and hippocampus of mice. In summary, we demonstrate that Se-PTC is a promising antioxidant compound and that the compound's activity is influenced by the amino group and by the characteristics of the arylselenium substituents. Thus, these compounds may be used as synthetic antioxidants that provide protection against oxidative diseases.

Abstract  Irrigation with cyanobacterial-blooming water containing microcystin-LR (MC-LR) poses threat to the growth of agricultural plants. Large amounts of rice (Oryza sativa) field in the middle part of China has been irrigating with cyanobacterial-blooming water. Nevertheless, the mechanism of MC-LR-induced phytotoxicity in the root of monocot rice remains unclear. In the present study, we demonstrate that MC-LR stress significantly inhibits the growth of rice root by impacting the morphogenesis rice crown root. MC-LR treatment results in the decrease in IAA (indole-3-acetic acid) concentration as well as the expression of CRL1 and WOX11 in rice roots. The application of NAA (1-naphthylacetic acid), an IAA homologue, is able to attenuate the inhibitory effect of MC-LR on rice root development. MC-LR treatment significantly inhibits OsNia1-dependent NO generation in rice roots. The application of NO donor SNP (sodium nitroprusside) is able to partially reverse the inhibitory effects of MC-LR on the growth of rice root and the expression of CRL1 and WOX11 by enhancing endogenous NO level in rice roots. The application of NO scavenger cPTIO [2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylinidazoline-1-oxyl-3-oxide] eliminates the effects of SNP. Treatment with NAA stimulates the generation of endogenous NO in MC-LR-treated rice roots. Treatment with NO scavenger cPTIO abolishes the ameliorated effect of NAA on MC-LR-induced growth inhibition of rice root. Treatment with SNP enhanced IAA concentration in MC-LR-treated rice roots. Altogether, our data suggest that NO acts both downstream and upstream of auxin in regulating rice root morphogenesis under MC-LR stress.

Abstract  Dinoflagellates are microalgae that are associated with the production of many marine toxins. These toxins poison fish, other wildlife and humans. Dinoflagellate-associated human poisonings include paralytic shellfish poisoning, diarrhetic shellfish poisoning, neurotoxic shellfish poisoning, and ciguatera fish poisoning. Dinotlagellate toxins and bioactives are of increasing interest because of their commercial impact, influence on safety of seafood, and potential medical and other applications. This review discusses biotechnological methods of identifying toxic dinoflagellates and detecting their toxins. Potential applications of the toxins are discussed. A lack of sufficient quantities of toxins for investigational purposes remains a significant limitation. Producing quantities of dinoflagellate bioactives requires an ability to mass culture them. Considerations relating to bioreactor culture of generally fragile and slow-growing dinoflagellates are discussed. Production and processing of dinoflagellates to extract bioactives, require attention to biosafety considerations as outlined in this review. (c) 2006 Elsevier Inc. All rights reserved.

Abstract  Carbon dioxide and sulfur dioxide were simultaneously absorbed into aqueous 1,8-diamino-p-menthane (DAM) in a stirred semi-batch tank with a planar gas-liquid interface within a range of 0-2.0kmol/m3 of DAM, 0.01-0.12mole fraction of CO2, 0.001-0.012mole fraction of SO2, and 298-318K. Absorption data of each gas in the CO2-DAM and SO2-DAM systems are obtained to verify their reaction regimes, based on film theory, respectively, which are used to analyze the simultaneous absorption mechanisms of CO2 and SO2 in the CO2-SO2- DAM systems. In the simultaneous absorption rate of CO2 and SO2 into DAM solution, the absorption of CO2 belongs to the second-order reaction of finite rate and the absorption of SO2 belongs to the instantaneous reaction regime.

Abstract  1. As a sequel to the demonstration that urethane applied to mouse skin followed by repeated applications of a promoting agent (croton oil) acts as an initiator of carcinogenesis, 29 substances, most of them related pharmacologically or chemically to urethane, have been screened for similar activity. 2. Of four antileukaemic agents tested, triethylene melamine (T.E.M.) was found to be an effective initiator of carcinogenesis but not carcinogenic, for mouse skin, in the doses tested; nitrogen mustard, Myleran, and aminopterin, in maximum sublethal doses, showed no initiating activity. 3. Of five substances exerting a specific effect on mitosis (in addition to those included in the category of anti-leukaemic agents), none showed initiating activity. 4. Of six narcotic agents tested none showed unequivocal evidence of initiating activity. 5. Of eight urethane derivatives and related compounds, ethyl N-methyl carbamate and ethyl N-phenyl carbamate showed weak initiating activity. In neither case was this as strong as that of a molecularly equivalent dose of urethane. (See Addendum II). 6. Four miscellaneous substances were tested. Of these 1,2-benzanthracene was found to be an effective initiator of carcinogenesis but not carcinogenic, in the doses used; and β-propiolactone was found to be an initiator of carcinogenesis. The latter is being tested for carcinogenicity at present. (See Addendum I.) 7. The use of the “t” test of statistical significance for skew distributions, such as those encountered in these results, is discussed. As an alternative, a ranking test is proposed. 8. The histological appearance of the skin following one, or two, applications of the test substances is described. Of those with initiating activity triethylene melamine, ethyl N-methyl carbamate and ethyl N-phenyl carbamate gave rise to no recognisable changes in the skin. 1,2-Benzanthracene consistently produced a moderate epidermal hyperplasia. The response to β-propiolactone varied from slight to marked epidermal hyperplasia. 9. The results are discussed, and an attempt is made to correlate initiating activity with other properties. © 1955, The British Empire Cancer Campaign for Research. All rights reserved.

Abstract  Acetylcholinesterase (AChE) is a proven target for control of the malaria mosquito (Anopheles gambiae). Unfortunately, a single amino acid mutation (G119S) in An. gambiae AChE-1 (AgAChE) confers resistance to the AChE inhibitors currently approved by the World Health Organization for indoor residual spraying. In this report, we describe several carbamate inhibitors that potently inhibit G119S AgAChE and that are contact-toxic to carbamate-resistant An. gambiae. PCR-RFLP analysis was used to confirm that carbamate-susceptible G3 and carbamate-resistant Akron strains of An. gambiae carry wild-type (WT) and G119S AChE, respectively. G119S AgAChE was expressed and purified for the first time, and was shown to have only 3% of the turnover number (k(cat)) of the WT enzyme. Twelve carbamates were then assayed for inhibition of these enzymes. High resistance ratios (>2,500-fold) were observed for carbamates bearing a benzene ring core, consistent with the carbamate-resistant phenotype of the G119S enzyme. Interestingly, resistance ratios for two oxime methylcarbamates, and for five pyrazol-4-yl methylcarbamates were found to be much lower (4- to 65-fold). The toxicities of these carbamates to live G3 and Akron strain An. gambiae were determined. As expected from the enzyme resistance ratios, carbamates bearing a benzene ring core showed low toxicity to Akron strain An. gambiae (LC(50)>5,000 μg/mL). However, one oxime methylcarbamate (aldicarb) and five pyrazol-4-yl methylcarbamates (4a-e) showed good to excellent toxicity to the Akron strain (LC(50) = 32-650 μg/mL). These results suggest that appropriately functionalized "small-core" carbamates could function as a resistance-breaking anticholinesterase insecticides against the malaria mosquito.