Alteration of Fetal Liver Colony Formation by Prenatal Chlordane Exposure

Alteration of Fetal Liver Colony Formation by Prenatal ChlordaneExposure. BARNETT, J. B., BLAYLOCK, B. L., GANDY, J., MENNA,J. H., DENTON, R., AND SODERBERG, L. S. F. (1990). Fundam. App.Toxicol. 15,820–822. Female mice were treated with 0 or8 mg/kg chlordane daily for 18 days during pregnancy. The fetusesof these mice were assayed for fetal liver hematopoietic activityat 18 days gestational age. Hematopoietic activity was evaluatedfor in vitro granulocyte-macrophage colony-forming units (GM-CFU)and in vivo spleen CFU (CFU-S). The consistent finding was asignificant depression of the numbers of both fetal liver GM-CFUand CFU-S without a change in liver cellularity in fetuses exposedto 8 mg/kg chlordane. These data show that the damage to stemcells that persists into adult life as a result of chlordaneexposure, as reported earlier by Barnett et al (1990) Fundam.Appl. Toxicol 14, 688–695, occurred during the fetal period.     

Some Novel Inhibitors of Platelet Aggregation: Acute Toxicity in Mice and Its Relationship to in vitro Efficacy and Toxicity: II. Nipecotoylaminoalkane and Nipecotoylpiperazine Congeners

Some Novel Inhibitors of Platelet Aggregation: Acute Toxicityin Mice and Its Relationship to in vitro Efficacy and Toxicity.II. Nipecotoylaminoalkane and Nipecotoylpiperazine Congeners.LAWRENCE, W. H., LASSLO, A., TURNER, J. E., FENG, Z., AND BOND,S. E. (1990). Fundam. Appl. Toxicol. 14, 356–363. Fourclosely related nipecotoyl congeners are employed as molecularprobes to evaluate the effects of systematic molecular changesupon lethal potency of the compounds. The In vivo toxicities,effected by changes in molecular structure, are compared totheir in vitro concentrations inhibiting ADP-induced aggregationand epinephrine-induced primary aggregation of human blood plateletsand their toxicities to mouse fibroblasts (L-929 cells) in culture.To assist in the selection of compounds which offer the greatestpromise as therapeutic agents for further evaluation and toguide future development of optimal molecular structures, aratio of acute ip LD50 µmol/kg) [T_m] to concentrationinhibiting 50% ADP-induced platelet aggregation (µmol/liter)[A] is calculated for each compound. These ratios range from2.41 to 24.92 for the four compounds included in this study     

Developing Differentiated Epithelial Cell Cultures: Airway Epithelial Cells

Developing Differentiated Epithelial Cell Cultures: Airway EpithelialCells. WU, R., SATO, G. H., AND WHITCUTT, M. J. (1986). Fundam.Appl. Toxicol. 6, 580–590. Recent progress in cell cultureenables us to grow and to maintain differentiated epithelialcells in a serum-free defined culture environment. Such an epithelialcell culture system free from interference by other nonepithelialcell types should be used widely in studies related to toxicology,carcinogenesis, and disease-related problems. This approachwill lead to a better understanding of pathological changesindicated in the injured epithelial layer. The gap of informationexisting between in vivo and in vitro can be bridged togetherby this simple epithelial cell culture system by carefully analyzingchanges of cell properties from in vivo to in vitro and by thecell separation to enrich specific cell types in preparation.Furthermore, evidence has been accumulated suggesting that theproperties of epithelial cells in culture are part of the integralcellular physiologies of epithelial cells in vivo. These propertiesare, in most cases, related to cell injury which is reparableeven in vitro if the appropriate condition is provided. Usingthe airway epithelial cell culture system developed in our laboratoryas an example, the above points are discussed. Finally, we haveshown that a differentiated tracheal epithelium with a similarpolarity as in vivo was established in the described serum-freeculture condition.     

Percutaneous Absorption/Metabolism of Phenanthrene in the Hairless Guinea Pig: Comparison of in Vitro and in Vivo Results

Percutaneous Absorption/Metabolism of Phenanthrene in the HairlessGuinea Pig: Comparison of in Vitro and in Vivo Results. NG,K. M. E., CHU, I., BRONAUGH, R. L., FRANKLIN, C. A., AND SOMERS,D. A. (1991). Fundam. Appl. Toxicol. 16, 517–524. Thein vitro and in vivo percutaneous absorption/metabolism of phenanthrenewas investigated in hairless guinea pigs. Flow-through diffusioncells and Hepes-buffered Hanks' balanced salt solution (HHBSS)as receptor fluid were used in the in vitro system. When phenanthrenewas applied to excised guinea pig skin mounted on the cellsat dose levels of 6.6 and 15.2 µg/cm², 89.7 and 79.1%of the administered doses were respectively absorbed into theskin and receptor fluids during a 24-hr perfusion period. Theseresults are consistent with the in vivo data which showed approximately80% absorption over the same period of time. Phenanthrene wasmetabolized in vitro into phenanthrene 9,10-dihydrodiol, 3,4-dihydrodiol,1,2-dihydrodiol, and traces of hydroxy phenanthrenes. Of thematerials absorbed in vitro, 92% was the parent compound and7% the dihydrodiol metabolites. When a nonviable in vitro systemwas used, 68% of the applied 15.2 µg/cm² dose was absorbed.Data from the present study demonstrate that the in vitro systemis a good model for predicting in vivo percutaneous absorptionof phenanthrene, and that penetration of phenanthrene throughthe skin is controlled more by the passive rate of diffusionthan by metabolism.     

An in Vitro Model for Assessing Muscle Irritation Due to Parenteral Antibiotics

An in Vitro Model for Assessing Muscle Irritation Due to ParenteralAntibiotics. WILLIAMS, P. D., MASTERS, B. G., EVANS, L. D.,LASKA, D. A., AND HOTTENDORF, G. H. (1987). Fundam. Appl. Toxicol.9, 10–17. A rat skeletal muscle cell line (L6) was evaluatedfor its potential to discriminate the muscle-irritating liabilityof several parenteral antibiotics. The cells were exposed toclinical as well as diluted concentrations of tetracycline,cefoxitin, cephalothin, carbenicillin, erythromycin, ceforanide,cefazolin, and cephaloridine for 1 hr. Control cells were similarlyexposed to culture media for 1 hr. The cells were subsequentlyassayed for their content of the muscle-associated enzyme creatinekinase (CK). Depletion of CK relative to control cultures wasutilized as the index of cellular damage. The results of theseanalyses revealed the following ranking of antibiotic toxicityto L6 muscle cells: tetracycline, erythromycin, cefoxitin >cephalothin, carbenicillin > ceforanide, cefazolin > cephaloridine.The relative order of toxicity of these antibiotics to L6 cellsis in good agreement with their reported muscle-irritating liabilityin man. The correlation between the results obtained in vitroand the irritancy data in vivo suggests that this model maybe a useful adjunct to in vivo testing of parenteral antibioticsfor muscle-irritation liability.     

The Relationship between pKa and Skin Irritation for a Series of Basic Penetrants in Man

The Relationship between pK_a and Skin Irritation for a Seriesof Basic Penetrants in Man. BERNER, B., WILSON, D. R., STEFFENS,R. J., MAZZENGA, G. C., HINZ, R., GUY, R. H., AND MAIBACH, H.I. (1990). Fundam. Appl. Toxicol 15, 760–766. For a seriesof bases, which penetrate through human skin in vitro at similarrates (0.056–0.49 µM/cm²/hr), penetrant pK_ais shown to correlate with erythema, edema, and color meterreadings. As estimates of irritation, erythema, edema, and rednessmeasurements are highly linearly correlated. For the selectedseries, irritation becomes significant for bases with a pK_a> 8. The irritation potential of acids with pK_a 4 has beenpreviously reported; pK_a appears highly predictive of acuteskin irritation for acids and bases in man.     

Kinetic Studies and Structure--Activity Relationships of Bispyridinium Oximes as Reactivators of Acetylcholinesterase Inhibited by Organophosphorus Compounds

Kinetic Studies and Structure-Activity Relationships of BispyridiniumOximes as Reactivators of Acetylcholinesterase Inhibited byOrganophosphorus Compounds. SU, C-T., WANG, P-H., LIU, R-F.,SHIH, J-H., MA, C., LIN, C-H., LIU, C-Y., AND WU, M-T. (1986).Fundam. Appl. Toxicol. 6,506–514. The kinetics of thereactivation of acetylcholinesterase inhibited by isopropylmethylphosphonofluoridate was studied. The reactivators usedinclude nine bispyridinium monooximes and three bispyridiniumdioximes. The dissociation constant (K₁). and the rate constant(K₂) of dephosphonylation of the complex formed from the organophosphorusacetylcholinesterase (OP-AChE) and the oxime were measured.The reactivation parameters obtained from the in vitro kineticstudies were used to elucidate the structure—activityrelationships. The hydrophobic property of a nonoxime substituentat the 3-position on the pyridinium ring can exert a positiveeffect on their binding affinity to OP-AChE. However, the rateconstants (K₂) of the nucleophiic displacement of OP-AChE byoximes depend negatively on these physical and structural factorsof the oximes. The correlations of the in vivo antidotal efficacy(ED50) of these bispyridinium oximes have been analyzed withtheir pharmacological properties, e.g., reactivation potency,antimuscarinic activities, and antinicotinic activities. However,no satisfactory correlations were observed. It may be concludedthat the detoxication mechanism of poisoning by isopropyl methylphosphonofluoridateis different from those of pinacolyl methylphosphonofluoridateand paraoxon.     

The Broiler Chicken as a Model for Immunotoxicity Assessment: 1. Standardization of in Vitro Immunological Assays

The Broiler Chicken as a Model for Immunotoxicity Assessment.1. Standardization of in Vitro Immunological Assays. BAECHER-STEPPAN,L., NAKAUE, H. S., MATSUMOTO, M., GAINER, J. H., AND KERKVLIET,N. I. (1989). Fundam. Appl. Toxicol. 12, 773–786. Thebroiler chicken was developed as an alternative animal modelto laboratory rodents for immunotoxico-logic assessment. Invivo treatment with 100–200 mg/kg cyclophosphamide (CY)was used as a known immunosuppressive treatment to standardizethe assay systems. Protocols for assessing specific immunologicalfunctions were developed in specific pathogen-free (SPF) broilersto measure lymphocyte blastogenesis to T-cell (concanavalinA and phytohemagglutinin) and B cell (Staphylococcus aureuscells) mitogens, delayed-type hypersensitivity (Dm) to tuberculin,natural killer (NK) cell cytotoxicity, plaque-forming cell (PFC)response to sheep red blood cells (SRBC), and serum antibodytiters to SRBC. CY was an effective immunosuppressant in thebroiler system for assessment of lymphocyte responsiveness tomitogenic stimulation, DTH reactivity, and the antibody responceto SRBC as assessed by PFC and serum antibody titers. NK cytotoxicitywas not altered on a cellular level following treatment withCY at a dose that preduced greater than 75% depletion of spleencellularity. However, under these conditions, it must bc assumedthat the capacity of CY-treated birds to mediate NK effectorfunctions would be reduced. These results demonstrate the applicabilityof the broiler chicken as an animal model for immunotoxicitytesting.     

Genotoxic Properties of Haloacetonitriles: Drinking Water By-Products of Chlorine Disinfection

Genotoxic Properties of Haloacetonitriles: Drinking Water By-Productsof Chlorine Disinfection. DANIEL, F. B., SCHENCK, K. M., MATTOX,J. K., LIN, E. L. C., HAAS, D. L., AND PEREIRA, M. A. (1986).Fundam. Appl. Toxicol. 6,447–453. Chlorinated and brominatedhaloacetonitriles (HAN), known drinking water contaminants whichform during chlorine disinfection, were investigated for genotoxicactivity. The HAN produced DNA strand breaks in cultured humanlymphoblastic (CCRF-CEM) cells, bound to the nucleophilic trappingagent 4-(p-nitrobenzyl)pyridine and formed a covalent bond topolyadenylic acid in a cell-free reaction system. Thus, we havedemonstrated that these chemicals are genotoxic, which wouldindicate a potential for carcinogenic activity and for humanhealth hazard.     

A Critical Evaluation of Predicting Ocular lrritancy Potential from an in Vitro Cytotoxicity Assay

A Critical Evaluation of Predicting Ocular Irritancy Potentialfrom an in Vitro Cytotoxicity Assay. KENNAH, H. E., II, ALBULESCU,D., HIGNET, S., AND BARROW. C. S. (1989) Fundam Appl. Toxicol12,281-290. Numerous in vitro cytotoxicity assays have beenproposed as potential alternatives to the Draize eye irritancytest. The results reported, based upon the rank correlationof ocular irritancy with cytotoxicity, have been encouraging.However. direct calibration of in vivo to in vitro data utilizingseveral categories of chemicals has not been reported. Thisstudy evaluated the use of in vitro cytotoxicity data for predictingthe ocular irritancy potential of 24 chemicals(six surfactants,seven alcohols four ketones, four acetates and three aromatics).BALB/c 3T3 cells were grown overnight, then exposed for 30 minto at least four different concentrations of each chemical (expressedas volume percentage). Linear regression analysis of the logconcentration versus percentage of control growth was used tocalculate the concentration of toxicant that inhibited the normalgrowth rate by 50% (G150). The rank ordering of cytotoxicitybased upon the GI50s was surfactants > aromatics > alcohols> ketones or acetates. The larger molecular weight representativeof each senes (i.e., 2-ethyl-I-hexanol for alcohols) had lowerGI50 values than those of the lower molecular weight substances.The GI50 values were then directly calibrated against in vivoocular irritancy quantitated as percentage corneal swellingfollowing exposure of rabbits to the same test chemicals. Asignificant linear correlation between cytotoxicity and ocularirritancy was established only for surfactants and alcohols.For acetates, ketones, and aromatics there was little correlation.The overall poor correlation between cytotoxicity and ocularirritancy was attributed to differences in mechanisms of irritancy.The lack of correlation illustrates that in vitro cytotoxicitydata cannot be used to predict the ocular irritancy potentialof a broad spectrum of chemicals.     

Dose-Dependent Cytotoxicity of Chlorinated Hydrocarbons in Isolated Rat Hepatocytes

Dose-Dependent Cytotoxicity of Chlorinated Hydrocarbons in IsolatedRat Hepatocytes. DAHLSTROM-KJNG, L., COUTURE, J., LAMOUREUX,C, VAILLANCOURT, T., AND PLAA, G. L. (1990). Fundam. Appl. Toxicol.14, 833–841. The aim was to determine if isolated suspendedhepatocytes could differentiate between the effects of fourchlorinated hydrocarbons that are hepatotoxic In vivo and fourthat are not. Membrane integrity was assessed by measuring alanineaminotransferase (ALT) release after 30- to 180-min incubationsin vitro. From the results, the chlorinated hydrocarbons fellinto three groups: tetrachloroethylene and 1,1,2,2-tetrachloroeth-anewere the most potent cytotoxicants; CCl₄, 1,1,2-trichloroethane,and trichloroethylene exhibited intermediate cytotoxicity; andlow cytotoxicity was observed with CHCl₃, 1,1,1 -trichlo-roethane,and 1,1-dichloroethylene. Cytotoxicity ranking correlated poorlywith the reported In vivo hepatotoxicity of these agents. Theeffect of adding SKF-525A on the cytotoxicity of tetrachloroethyleneand CCI4 was also assessed. In addition, hepatocytes from ratspretreated with 2,5-hexanedione were used to determine if theywere more susceptible to the effects of CHCl₃, CCl₄ or tetrachloroethylene.SKF-525A decreased the cytotoxicity of both CO, and tetrachloroethylene,whereas pretreatment with 2,5-hexanedione enhanced their effect.The effects of both SKF-525A and 2,5-hexanedione on CCl in vitroare consistent with In vivo findings. However, tetrachloroethyleneis not hepatotoxic In vivo, suggesting that SKF-525A might actby stabilizing plasma membranes rendering the hepatocyte moreresistant to lysis. Overall, the results cast doubts on theuse of ALT release from isolated hepatocytes as an appropriatein vitro model for assessing hepatotoxic properties of chlorinatedhydrocarbons.     

Inhalation Teratology Studies of n-Butyl Mercaptan in Rats and Mice

Inhalation Teratology Studies of n-Butyl Mercaptan in Rats andMice. THOMAS, W. C., SECKAR, J. A., JOHNSON, J. T., ULRICH,C. E., KLONNE, D. R., SCHARDEIN, J. L., AND KIRWIN, C. J. (1987).Fundam. Appl. Toxicol. 8, 170–178. n-Butyl mercaptan (n-BM)is used as a solvent and a chemical intermediate. Pregnant CharlesRiver CD-1 mice and COBS CD rats were randomly assigned to acontrol group and to three n-BM-exposed groups of 25 rats and25 mice each. The animals were exposed by whole-body inhalationto mean n-BM concentrations of 10, 68, or 15 2 ppm on a 6-hrdaily exposure schedule. Rats were exposed on Gestation Days6–19 and mice on Gestation Days 6–16. The controlgroup was exposed to filtered air only on a comparable regimen.Cesarean sections were performed on all surviving mice on GestationDay 17 and on all rats on Gestation Day 20. Seventeen of then-BM-treated mice died: 8 at the 68-ppm level and 9 at the 152-ppmlevel; none of the n-BM-treated rats died. An increased postimplantationloss and increased early resorption occurred in mice exposedat 68 and 152 ppm, indicating embryotoxicity. An increased incidenceof cleft palate was observed in mice exposed to 10 or 68 ppmwhich was not statistically significant. Total fetal abnormalitieswere statistically significantly different from controls at68 ppm where maternal lethality was observed when based on thefetal unit although not when based on the litter unit. Ratsexposed to 152 ppm or less demonstrated no terata.     

Some Tautologous Aspects of the Comparison of Carcinogenic Potency in Rats and Mice

Some Tautologous Aspects of the Comparison of Carcinogenic Potencyin Rats and Mice. BERNSTEIN, L., GOLD, L. S., AMES, B. N., PIKE,M. C, and HOEL, D. G. (1985). Fundam. Appl. Toxicol. 5, 79–86.In risk estimation, the results of rodent carcinogenesis experimentsare often used to quantitatively predict effects in man. Thejustification for this approach has in large part been dependentupon the good correlation of carcinogenic potency found betweenmice and rats over large numbers of test chemicals. Using thedata base of chemicals tested by the NCI Bioassay Program, weobserve that there is a very high correlation of the maximumdoses tested (max-d) for rats and mice on a milligram per kilogrambody weight per day basis. Next we show that the calculatedcarcinogenic potency (b—defined in the paper) is restrictedto an approximately 30-fold range surrounding log(2)/max-d,which has a biological as well as a statistical basis. Sincethe max-d's for the set of NCI test chemicals vary over manyorders of magnitude, it necessarily follows statistically thatthe carcinogenic potencies will be highly correlated. This "artifact"of potency estimation does not imply that there is no basisfor extrapolating animal results to man. It does suggest, however,that the interpretation of correlation studies of carcinogenicpotency needs much further thought.     

Interspecies Comparisons of A/D Ratios: A/D Ratios Are Not Constant across Species

Interspecies Comparisons of A/D Ratios: A/D Ratios Are Not Constantacross Species. DASTON, G. P., ROGERS, J. M., VERSTEEG, D. J.,SABOURIN, T. D., BAINES, D., AND MARSH, S. S. (1991). Fundam.Appl. Toxicol. 17, 696–722. The hypothesis that the ratioof the adult (A) and developmental (D) toxicity of a chemicalis constant across animal species has been proposed as the basisfor identifying developmental hazards, both from traditionaldevelopmental toxicity screens using laboratory mammals andfrom alternative systems such as the coelenterate Hydra attenuata.The purpose of this study was to determine whether A/D ratiosare constant across species. The developmental and adult toxicityof 14 chemicals was assessed in four phylogenetically differentspecies. The chemicals tested were aminopterin, bromodeoxyuridine,cadmium chloride, caffeine, congo red, dinocap, dinoseb, diphenylhydantoin,epinephrine, ethylenethiourea, 2-methoxyethanol, mirex, all-trans-rtinoicacid, and trypan blue. These chemicals are representative ofa variety of toxic mechanisms and a range of potencies. Speciesused were the CD-1 mouse (Mus musculus), South African clawedfrog (Xenopus laevis), fathead minnow (Pimephales promelas),and fruit fly (Drosophila melanogaster). The mouse is a commonlyused model for developmental toxicity. The other species areknown to be sensitive to mammalian toxicants and have well-studiedembryologies. Mice were exposed to chemicals either po or bysc injection using a standard Segment II protocol in which pregnantmice are administered the test agent on a daily basis from GestationDays 6 to 15, adult toxicity is evaluated during and after treatment,and developmental toxicity is evaluated in fetuses at term.The exposzure duration spans the period of organ formation inthe embryo. The other species were exposed to test agents fora developmentally comparable period. This was from blastulation(shortly after fertilization) to the free-swimming tadpole stagein Xenopus (4 days); from blastulation to the free-swimmingfry stage in Pimephales (7 days); and for the entire larvalperiod, the period of development of the imaginal discs, inDrosophila (6 days). Adults of each species were exposed totest agents for 4, 7, and 6 days, respectively. The route ofexposure was via the water column in the two aquatic speciesand via the diet in Drosophila. Statistical lowest observedeffect level (LOEL) and no observed effect level (NOEL) valueswere generated for adult and developmental toxicity in eachspecies. A/D ratios were calculated using both LOEL and NOELvalues. The results indicate little concordance of A/D amongspecies: (1) A/D ratios calculated from LOEL data are withinthe same order of magnitude for all four species for only fourchemicals: dinocap, diphenylhydantoin, epinephrine, and mirex;(2) based on NOEL data, again only four have A/D ratios forall species in the same order of magnitude: dinocap, diphenylhydantion,epinephrine, and ethylenethiourea. It has been suggested thatan A/D ratio of 3 or greater is indicative of a developmentalhazard. Using this criterion, there was consistent agreementamong species only for dinocap (NOEL only), diphenylhydantoin,and all-trans -retinoic acid. Several statistical analyses forconcordance were applied to the data. In no case was A/D foundto correlate between species. These data indicate that A/D ratiosare not constant across these representative species, and thereis no basis for using A/D for hazard assessment.     

Lack of Genotoxicity of the Cancer Chemopreventive Agent N-(4-Hydroxyphenyl)retinamide

Lack of Genotoxicity of the Cancer Chemopreventive Agent N-(4-Hydroxyphenyl)retinamide.PAULSON, J. D., OLDHAM, J. W., PRESTON, R. F., AND NEWMAN, D.(1985). Fundam. Appl. Toxicol. 5, 144–150. As part ofthe preclinical drug safety evaluation of the cancer chemopreventiveagent N(4-hydroxyphenyl)retinainide (HPR) in vitro and in vivotests were conducted to assess its genotoxic activity. Negativefindings from HPR testing were demonstrated in the Ames Salmonella/microosomalactivation test, the L5178Y mouse lymphoma assay, and a ratbone marrow cytogenetics study. These data imply that HPR lacksthe ability to induce point mutations or chromosomal aberrations,and is therefore not genotoxic. Limited testing of retinyl acetatein the Ames test, the L5178Y mouse lymphoma assay, and the primaryrat hepatocyte/DNA repair assay yielded consistently negativeresults. These findings and previously published results concerningretinoid genotoxicity are discussed.     

Contribution of Monoaminergic Nervous System in Potentiation of 2-sec-Butylphenyl N-Methylcarbamate (BPMC) Toxicity by Malathion in Male Mice

Contribution of Monoaminergic Nervous System in Potentiationof 2-sec-Butylphenyl N-Methylcarbamate (BPMC) Toxicity by Malathionin Male Mice. TAKAHASHI, H., TANAKA, J., TSUDA, S., and SHIRASU,Y. (1987). Fundam. Appl. Toxicol. 8, 415–422. Malathion-inducedmarked potentiation of BPMC toxicity (about fivefold) was analyzedby measuring LD50 as an index of acute toxicity. The acute lethalityof BPMC was decreased by muscarinic blockers (atropine, methylatropine,or trihexyphenidyl) or a monoamine oxidase inhibitor (pargyline)and increased by a monoamine depleter (reserpine) or a dopaminergicblocker (haloperidol). The potentiation observed with BPMC andmalathion was decreased by the muscarinic blockers, monoaminedepleters (reserpine, -methyl-p-tyrosine), an -noradrenergicblocker (phen-tolamine), or haloperidol. The acute toxicitiesof other N-methylcarbamates MPMC (3,4-di-methylphenyl N-methylcarbamate),MTMC (3-methylphenyl N-methylcarbamate), NAC (1-naphthyl N-methylcarbamate),and XMC (3,5-dimethylphenyl N-methylcarbamate) were potentiatedby malathion to a lesser degree than that of BPMC. Atropineprotected against the lethalities of all N-methylcarbamates.Reserpine or haloperidol potentiated the lethalities of N-methylcarbamateswith a similar tendency toward malathion. When the inhibitoryeffect of each N-methylcarbamate on brain acetylcholinesterase(AChE) was compared with its LD50, among five N-methylcarbamatesBPMC had particularly strong anti-AChE activity. This characteristicof BPMC was not observed after the treatment with reserpine.These results suggest that BPMC may act not only on cholinergicnerves as an anti-AChE, but also on monoaminergic nerves whichantagonize the lethal cholinergic effect. Malathion might inhibitthe effect of BPMC on the monoaminergic nerves, thereby markedlypotentiating the lethal effect of BPMC.     

Cyanide Antagonism with Carrier Erythrocytes and Organic Thiosulfonates

Previous studies reported that resealed erythrocytes containingrhodanese (CRBC) and Na₂S₂O₃ rapidly metabolize cyanide to theless toxic thiocyanate both in vitro and in vivo. This provideda new conceptual approach to prevent and treat cyanide intoxication.Although the rhodanese-containing carrier cells with thiosulfateas the sulfur donor were efficacious, this approach has potentialdisadvantages, as thiosulfate has limited penetration of cellmembrane and product inhibition of rhodanese can occur due toinorganic sulfite accumulation. In order to circumvent substratelimitation and product inhibition by sodium thiosulfate, organicthiosulfonates were explored. These thiosulfonates have higherlipid solubility than thiosulfate and therefore can replenishthe depleted sulfur donor, as they can readily penetrate cellmembranes. Also, product inhibition of rhodanese is less aptto occur. This change in sulfur donors should greatly enhancecyanide detoxication, replenish the sulfur donor, and minimizeproduct inhibition of rhodanese. Present studies demonstratethe enhanced efficacy of exogenous organic thiosulfonates oversodium thiosulfate in the CRBC antidotal system to detoxifythe lethal effects of cyanide either alone or in combinationswith exogenously administered NaNO₂. Murine carrier erythrocytescontaining purified bovine liver rhodanese were administeredintravenously into male Balb/C mice. Subsequently, butanethiosulfonate(BTS) or Na₂S₂O₃ (ip), and NaNO₂ (sc) were co-administered priorto KCN (sc). Potency ratios, derived from the LD₅₀ values, werecompared in groups of mice treated with CRBC-Na₂S₂O₃ or CRBC-BTSeither alone or in combination with NaNO₂. The CRBC-BTS antidotalsystem shows strikingly enhanced protective effect over thatof the CRBC-thiosulfate system either alone or in combinationwith sodium nitrate.     

An Immunotoxicological Evaluation of 4, 4'-Thiobis-(6-t-butyl-m-cresol) in Female B6C3F1 Mice: 1. Body and Organ Weights, Hematology, Serum Chemistries, Bone Marrow Cellularity, and Hepatic Microsomal Parameters

An Immunotoxicological Evaluation of 4,4'-Thiobis-(6-t-butyl-m77-cresol)in Female B6C3F1 Mice. 1. Body and Organ Weights, Hematology,Serum Chemistries, Bone Marrow Cellularity, and Hepatic MicrosomalParameters. MUNSON, A. E., WHITE, K. L., JR., BARNES, D. W.,MUS-GROVE, D. L., LYSY, H. H., AND HOLSAPPLE, M. P. (1988).Fundam. Appl. Toxicol. 10, 691–700. Adult female B6C3F1mice were gavaged with 4,4'-thiobis-(6-t-butyl-m-cresol) (TBBC)in corn oil at doses of 10, 100, or 200 mg/kg daily for 14 consecutivedays. There was no overt toxicity, as manifested by grosslyobservable behavioral changes, decreased growth rate over theexposure period, or mortality. There were also no marked effectson serum chemistries or hematology, with the exception of asignificant increase (41%) in the number of leukocytes at thehighest dose. Absolute differential counts indicated that significantincreases occurred in the number of lymphocytes (31%) and neutrophils(177%). Studies with bone marrow indicated a significant 30%increase in the number of cells/femur from animals treated withthe highest dose of TBBC. The number of macrophage progenitors(CFU-M)/femur was significantly increased by 28%, while thenumber of granulocyte-monocyte progenitors (CFU-GM)/femur wasnonsig-nificantly increased by 20% in the high dose animals.The weight of both the spleen and liver was increased in a dose-relatedfashion, although the histopathology of the spleen of TBBC-treatedmice was not different from control. The livers of mice receivingthe high dose showed mild focal hydropic degeneration, mildhepatitis, and a slight increase in the number of Kupffer cells.No other organs were affected. Liver microsomal protein andcytochrome P-450 levels were increased in a dose-related fashion.Enzyme activities of aminopyrine demethylase and aniline hydroxylase,but not arylhydrocarbon hydroxylase, were also increased ina dose-related fashion.     

Photolysis Products of 2,4,5,2',4',5'-Hexabromobiphenyl: Hepatic Microsomal Enzyme Induction and Toxicity in Sprague-Dawley Rats

Photolysis Products of 2,4,5,2',4',5'-Hexabromobiphenyl: HepaticMicrosomal Enzyme Induction and Toxicity in Sprague-Dawley Rats.MILLIS, C. D., MILLS, R., SLEIGHT, S. D., AND AUST, S. D. (1985).Fundam. Appl. Toxicol. 5, 555–567. The irradiation of2,4,5,2',4',5'-hexabromobiphenyl (2,4,5-HBB) by ultravioletlight created a mixture of lower brominated polybrominated biphenyl(PBB) congeners. Three photoproducts, 2,4,5,3',4'-pentabromobiphenyl(-PBB), 2,4,5,2',5'-PBB, and 3,4,3',4'-tetrabromobiphenyl (3,4-TBB),as well as 2,4,5-HBB and the photolyzed 2,4,5-HBB mixture, wereadministered to rats as a single ip injection (90 mg/ kg, except3,4-TBB, which was given at 2 mg/kg) 2 weeks before sacrifice.All treatments except 3,4-TBB induced NADPH-cytochrome P-450reductase and aminopyrine-N-demethylase activities while alltreatments except 2,4,5-HBB induced ethoxyresorufin-O-deethylaseand UDP-glucuro-nosyltransferase activities. Thymus to bodyweight and spleen to body weight ratios were unchanged comparedto controls for all treatments whereas an increase in the liverweights was observed for all treatment groups. Histologic examinationrevealed that the photolyzed 2,4,5-HBB mixture caused moderateto severe hepatocyte enlargement. Results of tissue analysisfor the pure PBB congeners indicated that 2,4,5,2',5'-PBB and3,4-TBB were metabolized in vivo and this was confirmed by invitro metabolism studies. The results revealed that the photolyzed2,4,5-HBB mixture caused a mixed-type induction of hepatic drug-metabolizingenzymes. This is most likely due to the effect of 2,4,5-HBBand toxic congeners formed during the irradiation of 2,4,5-HBB.2,4,5,3',4'-PBB, which is toxic and apparently not metabolized,is believed to be the major congener contributing to the increasedtoxicity of the photolyzed 2,4,5-HBB mixture since 3,4-TBB wasmetabolized and appeared not to be as potent as inducer of arylhydrocarbon hydroxylase activity