Metabolism of methyl-(E)-2-[2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl]-3-methoxyacrylate (azoxystrobin) in rat.

1. The metabolic fate of [(14)C]-methyl-(E)-2-[2-[6-(2-cyanophenoxy)pyrimidin-4-yloxy]phenyl]-3-methoxyacrylate (azoxystrobin) was determined in the male and female rat following a single oral dose of 1 and 100 mg x kg(-1) and in surgically prepared, bile duct-cannulated rats following a single oral dose of 100 mg x kg(-1). 2. Azoxystrobin was extensively metabolized with at least 15 metabolites. There was a sex difference, with females producing more metabolites than males. 3. The two principal metabolic pathways were hydrolysis of the methoxyacid followed by glucuronic acid conjugation and glutathione conjugation of the cyanophenyl ring followed by further metabolism leading to the mercapturic acid. There were also several other minor pathways.

Metabolism of 2-(4-methylsulphonyl-2-nitrobenzoyl)-1,3-cyclohexanedione (mesotrione) in rat and mouse.

1. The metabolic fate of [14C]-2-(4-methylsulphonyl-2-nitrobenzoyl)-1,3-cyclohexanedione (mesotrione) has been determined in the male and female rat and mouse following a single oral dose of either 1 or 100 mg kg(-1), in rat given 14 consecutive oral doses of 1 mg kg(-1), and in the surgically prepared, bile duct-cannulated rat following a single oral dose of 50 mg kg(-1). The excretion of a single i.v,. dose of 1 mg kg(-1) in the male and female rat was also investigated. 2. Mesotrione was extensively absorbed and rapidly excreted via urine in both rat and mouse. The absorbed dose was not well metabolized in either species. Unabsorbed material was subject to metabolic action by the gut microflora. 3. The major metabolic pathway was hydroxylation of the aromatic ring. There was evidence for cleavage of the dione and aromatic rings followed by reduction of the nitro group in the gastrointestinal tract. 4. There were no species differences in the metabolism and excretion of mesotrione, which could explain the species differences in toxicity reported for this class of compounds.

Metabolism of 2,3,5,6-tetrachloronitrobenzene (tecnazene) in rat.

1. The metabolic fate of [U-14C]-2,3,5,6-tetrachloronitrobenzene (tecnazene) has been determined in the male and female rat following a single dose of 1 mg/kg and in surgically prepared, bile-duct-cannulated rats following a single oral dose of 135 mg/kg. 2. Radioactivity in the female rat was excreted mainly in urine (82%). The male rat, however, excreted approximately equal amounts of radioactivity in urine and faeces (the latter via bile). 3. The principal metabolic pathway was conjugation with glutathione (GSH) and concomitant nitro-displacement. The GSH-conjugate and related metabolites were excreted in the bile and ultimately in the urine as the mercapturic acid conjugate. The cysteine conjugate underwent beta-lyase-mediated metabolism to yield a thiol that underwent subsequent methylation to the thioanisole followed by S-oxidation. 4. A novel tetrachloromethyldisulphide metabolite was also formed.

Metabolism and pharmacokinetics of deuterium-labelled di-2-(ethylhexyl) adipate (DEHA) in humans.

The metabolism and pharmacokinetics of [2H10]di-2-(ethylhexyl) adipate (DEHA) labelled on the ethyl side-chains was determined in six male volunteers. The dose administered was 46 mg [2H10]DEHA given orally. No parent molecule was found in plasma; however, the metabolite [2H5]2-ethylhexanoic acid (EHA) was detected (mean rate of formation: 1.63 +/- 1.19/hr; mean rate of elimination: 0.42 +/- 0.1/hr). Further oxidative metabolism products were detected in urine; the dominant metabolite identified was EHA present as a conjugate and accounted for an average of 8.6% of the administered dose. [2H5]2-Ethyl-5-hydroxyhexanoic acid, [2H5]2-ethylhexanedioic acid, [2H5]2-ethyl-5-keto-hexanoic acid and [2H5]2-ethylhexanol together accounted for a further 3.5% of the dose. The fate of the remainder was not determined.

The metabolism of cypermethrin in man: differences in urinary metabolite profiles following oral and dermal administration.

1. The pyrethroid insecticide cypermethrin was administered orally to six male volunteers as a single dose of 3.3 mg (cis: trans 1:1) and dermally to six volunteers at a dose of 31 mg/800 cm2 (cis:trans 56:44) as a soya oil-based formulation. Urine samples were collected for up to 5 days and analysed for the metabolites cis and trans 3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (DCVA), 3-phenoxybenzoic acid (3PBA) and 3-(4'-hydroxyphenoxy) benzoic acid (4OH3PBA) following an acid hydrolysis procedure. 2. Following oral dosing approx. equal amounts of (cis+trans DCVA) and (3PBA+4OH3PBA) were excreted with peak excretion rates occurring between 8 and 24 h after dosing. The ratio of trans:cis DCVA was on average 2:1. Based on DCVA measurements the amount of cypermethrin absorbed was estimated to be between 27% and 57% (mean 36%) of the administered dose. 3. Peak urinary excretion rates of metabolites occurred between 12 and 36 h after dermal dosing. The amount of metabolites derived from the phenoxybenzyl moiety (3PBA+4OH3PBA) was on average 4 times greater than the amount of (cis+trans DCVA) recovered in urine. The ratio of trans:cis DCVA was, on average 1:1.2. Based on the recovery of the phenoxybenzyl metabolites it is estimated that 0.85-1.8% (mean 1.2%) of the administered cypermethrin was absorbed. 4. These studies demonstrate marked differences in the urinary metabolite profile by the two routes, and provide an improved basis for determining the extent and main route of absorption of cypermethrin under occupational exposure conditions.

Oral pharmacokinetics of fluazifop-butyl in human volunteers.

1. Fluazifop-butyl, the active ingredient of FUSILADE, a selective herbicide, was administered orally to three male volunteers at a dose level of 0.07 mg kg-1 body weight. Over a period of 6 d between 80 and 93% of the dose was excreted in urine as the metabolite fluazifop, the majority within the first 24 h. Peak plasma concentrations of fluazifop occurred 1-2.5 h after administration. 2. The elimination of fluazifop from plasma and urine can be described by a one-compartment pharmacokinetic model and the elimination half-life was estimated from blood and urine data to be within the range 9-37 h. Fluazifop was found to bind to serum proteins. 3. The study indicates that the amount of fluazifop-butyl absorbed in exposed persons can be assessed by measuring fluazifop concentrations in urine.

Chemical modification of recombinant interleukin 2 by polyethylene glycol increases its potency in the murine Meth A sarcoma model.

Recombinant human interleukin 2 purified from Escherichia coli has limited solubility at neutral pH and a short circulatory half-life. This recombinant interleukin 2 was chemically modified by an active ester of polyethylene glycol. The modified interleukin 2 was purified by hydrophobic interaction chromatography and characterized by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and isoelectric focusing. This conjugate was compared to unmodified recombinant interleukin 2 in vitro and in vivo. Covalent attachment of the hydrophilic polymer polyethylene glycol enhanced the solubility of interleukin 2, decreased its plasma clearance, and increased its antitumor potency in the Meth A murine sarcoma model.

Serological characterization and gene localization of an Escherichia coli-expressed 37-kilodalton Treponema pallidum antigen.

A recombinant plasmid containing a 5.6-kilobase-pair DNA fragment of the Treponema pallidum genome was characterized by endonuclease mapping, and the encoded proteins were expressed in Escherichia coli and analyzed by use of in vitro transcription and translation. One of the proteins, identified as having a molecular weight of 37,000 (37K protein), was selected for further study. Initially, the seroreactivity of the partially purified 37K antigen was demonstrated by immunoblotting. After its purification to near homogeneity, the cloned T. pallidum protein was assessed for diagnostic significance by radioimmunoassay. Although first identified as seroreactive by screening with secondary syphilitic sera (T. E. Fehniger, A. M. Walfield, T. M. Cunningham, J. D. Radolf, J. N. Miller, and M. A. Lovett, Abstr. Annu. Meet. Am. Soc. Microbiol. 1985, B156, p. 44), the antigen was shown to be serologically reactive with antibodies in serum from all stages of syphilis but was not recognized by serum from controls by both immunoblotting and radioimmune assay. Further, a monospecific polyclonal rabbit antiserum generated to the 37K antigen recognized a polypeptide of the same molecular weight from T. pallidum but did not efficiently recognize proteins from five nonpathogenic treponemes tested. Therefore, because of reactivity with and specificity for T. pallidum antibodies, the 37K antigen may be of serodiagnostic value in the detection of syphilis.

Serospecificity of a cloned protease-resistant Treponema pallidum--specific antigen expressed in Escherichia coli.

We evaluated the serological reactivity of a protease-resistant antigen designated 4D which was encoded by Treponema pallidum DNA and was expressed in Escherichia coli from recombinant plasmid pAW329. This 19,000-molecular-weight antigen was purified in its native, non-protease-treated form from E. coli sonic extracts by molecular sieving and ion-exchange chromatography. Antibody binding to antigen 4D was detected by a radioimmunoassay. Antigen 4D-specific antibody was detected in 95% of the sera in a Centers for Disease Control syphilis serum panel. It was also detected in 55% of 121 primary syphilis patients, whereas syphilis antibody was detected in 83% of the sera by a fluorescent treponemal antibody absorption test and in 88% of the sera by a T. pallidum microhemagglutination test. In tests of 118 normal sera, less than 3% demonstrated antibody to antigen 4D; these results are similar to microhemagglutination and fluorescent treponemal antibody absorption test results. Rabbit antisera against Treponema phagedenis, Treponema refringens, Treponema denticola, and Treponema vincentii did not react with antigen 4D.

Correlation of autoagglutination and virulence of yersiniae.

Virulent strains of Yersinia pestis, Y. pseudotuberculosis and Yersinia enterocolitica invariably autoagglutinated in tissue culture media when grown at 36 degrees C. Avirulent strains did not possess this property.

Effects of heat-stable enterotoxin of Yersinia enterocolitica on ion transport and cyclic guanosine 3',5'-monophosphate metabolism in rabbit ileum.

Strains of Yersinia enterocolitica produce a heat-stable enterotoxin which is positive in the suckling mouse bioassay. Partial purification by a procedure previously worked out for heat-stable Escherichia coli enterotoxin yielded a substance which increases particulate guanylate cyclase activity and short-circuit current and inhibits active Cl-absorption in rabbit ileal mucosa. These effects of Y. enterocolitica enterotoxin are similar to those of heat-stable E. coli enterotoxin, suggesting a common mechanism of action.

Heat-stable enterotoxin of Escherichia coli: in vitro effects on guanylate cyclase activity, cyclic GMP concentration, and ion transport in small intestine.

A partially purified preparation of the heat-stable enterotoxin of Escherichia coli caused a rapid and persistent increase in electric potential difference and short-circuit current when added in vitro to the luminal surface of isolated rabbit ileal mucosa. As little as 1 ng/ml produced an easily detectable response. Under short-circuit condition, the enterotoxin abolished net Cl- absorption; this change was half that produced by theophylline, which stimulated net secretion. The enterotoxin did not change cyclic AMP concentration but caused large and persistent increases in cyclic GMP concentration. The electrical and nucleotide responses exhibited similar and unusually broad concentration-dependences and maximal effects could not be demonstrated. Theophylline elevated cyclic GMP concentration 3-fold both in the presence and absense of the enterotoxin, suggesting no effect of the toxin on cyclic GMP phosphodiesterase. Guanylate cyclase [GTP pyrophosphatelyase(cyclizing); EC 4.6.1.2] activity in a crude membrane fraction from intestinal epithelial cells was stimulated 7-fold by the enterotoxin. These results suggest that guanylate cyclase stimulation is the basis for the toxin's diarrheagenic effect.