Mineralization and plant uptake of 14C-labeled nonylphenol, nonylphenol tetraethoxylate, and nonylphenol nonylethoxylate in biosolids/soil systems planted with crested wheatgrass

Microcosm experiments (duration, 150 d) were conducted to evaluate the mineralization and plant uptake of [14C]nonylphenol (NP), [14C]nonylphenol tetraethoxylate (NPE4), and [14C]nonylphenol nonylethoxylate (NPE9) in a soil/biosolids (99.5:0.5 w/w) environment planted with crested wheatgrass (Agropyron cristatum). Three initial nominal concentrations (6, 24, and 47 mg/kg dry wt) each of NP, NPE4, and NPE9 were examined along with unplanted and unplanted poisoned controls. Phenol (22 mg/kg) also was evaluated as a more degradable reference compound. The biosolids were obtained from a municipal treatment plant, and the loamy sand soil was freshly collected. Mineralization ranged from 7% for NP to 53% for phenol, and no enhancement was observed in the planted systems. For NP, NPE4, and NPE9, 14C foliar tissues concentrations were proportional to exposure concentrations but were 10-fold lower than the root concentrations and two- to threefold lower than the soil concentrations. Bioconcentration factors (BCFs) based on 14C measurements ranged from 0.31 (mg compound/kg dry plant/ mg compound/kg dry soil) for systems spiked with NP to 0.52 for systems spiked with NPE9. Results of the NP analysis (initial concentration, 47 mg/ kg) showed a 90% decrease in the soil concentration and an average BCF of 1.0. The lower BCF calculated from the 14C analysis likely resulted from the presence of NP transformation products in the soil that are less available or are translocated by the plants but quantified by the combustion/liquid scintillation counting procedure.     

Metabolism of bis(2-chloroethyl)ether and bis(2-chloroisopropyl)ether in the rat

Male rats were given single peroral doses of bis(1-¹⁴C-2-chloroethyl)ether ([1-¹⁴C]BCEE) (40 mg/kg) and of bis(1-¹⁴C-2-chloroisopropyl)ether ([1-¹⁴C]BCIE) (90 mg/kg). Excretion of¹⁴CO₂ and urinary¹⁴C was followed for 48 hr. The time required to eliminate one half of the dose was 12 hr for [1-¹⁴C]BCEE and 19 hr for [1-¹⁴C]BCIE. In the case of [1-¹⁴C]BCEE, expired¹⁴CO₂ accounted for 11.5 ± 5.6(SD) % of the dose, urinary¹⁴C accounted for 64.7 ± 14.8%, and 2.4 ± 1.3% was found in the feces. The figures for [1-¹⁴C]BCIE were 20.3 ± 9.4% expired as¹⁴CO₂, 47.5 ± 8.1% as urinary¹⁴C, and 3.8 ± 0.3% as fecal¹⁴C. Thiodiglycolic acid (TDGA) accounted for roughly 75% of the total urinary¹⁴C collected after the [1-¹⁴C]BCEE dose. Lesser metabolites of BCEE were 2-chloroethoxyacetic acid (CEAA) (5%), and N-acetyl-S-[2-(2-chloroethoxy)ethyl]-L-cysteine (ACEEC) (7%). Metabolites of [1-¹⁴C]BCIE identified in rat urine were 2-(2-chloro-1-methylethoxy)propanoic acid (CMEPA), roughly 36% of the total urinary¹⁴C, and N-acetyl-S-(2-hydroxypropyl)-L-cysteine (AHPC) at 19%.     

Pharmacokinetics of inhaled [14C]-2-nitropropane in male sprague-dawley rats

Rats were exposed by inhalation for 6 hr to 20 or 154 ppm of 2-[¹⁴C]nitropropane (2-[¹⁴C]NP) and the disposition of radioactivity in these animals was followed for 48 hr. These data indicate that at least 40% of the inhaled 2-[¹⁴C]NP was absorbed. 2-[¹⁴C]NP was rapidly metabolized and eliminated, and thus has a low potential to accumulate in the rat during prolonged or repeated exposures. Numerous differences were observed in the disposition of 2-[¹⁴C]NP at the two exposure concentrations that indicate the kinetics of 2-[¹⁴C]NP were nonlinear in rats at the 154 ppm exposure concentration. These changes in the fate of 2-[¹⁴C]NP are consistent with and may explain the marked increase in the toxicity observed by others when rats were exposed to high concentrations (≥200 ppm) of 2-nitropropane.     

Uptake of nonylphenol and nonylphenol ethoxylates by crested wheatgrass

Nonylphenol (NP) and other hydrophobic biodegradation intermediates of nonylphenol ethoxylate (NPE) surfactants have been identified in wastewater treatment biosolids. These biosolids often are land applied, but little is known regarding the potential uptake of biosolid-derived contaminants by plants. Hydroponic experiments, 11 to 14 weeks in duration, were conducted to examine the uptake and translocation of 14C and unlabeled NP, nonylphenol tetraethoxylate (NPE4), and nonylphenol nonylethoxylate (NPE9) by crested wheatgrass (Agropyron cristatum). Phenol also was evaluated for comparison. Plant tissue was analyzed for 14C and for the parent compounds. Volatilization from the hydroponic system and rhizosphere mineralization also were quantified. At the conclusion of the study, most of the plant-associated 14C was found in the roots (NP = 98%, NPE4 = 92%, and NPE9 = 81%). Concentrations of 14C in the foliar tissue ranged from 0.002 to 0.045 mg-equivalent per kg (dry wt), but no parent compounds were detected, implying that the 14C was unextractable or in the form of metabolites. Transpiration stream concentration factors for NP, NPE4, and NPE9, calculated assuming the 14C was parent compound, were 0.012, 0.032, and 0.066, respectively. Little mineralization was observed for NP, NPE4, and NPE9 in the hydroponic system; however, for phenol, 16 to 30% of the added 14C was mineralized.     

Effect of dietary protein status on glucose utilization by the pentose cycle in pig adipose tissue

We investigated the effects of three levels of dietary protein (12, 18 and 23%) on lipid metabolism in pig adipose tissue (PAT). Eight-week-old male pigs were fasted for 96 hr and then refed for the same period of time. Adipose tissue biopsy samples were obtained and incubated for 3 hr in Hanks' salts containing 5.5 mM [1-¹⁴C], [6-¹⁴C], [U-¹⁴C] and [3-³H] glucose as well as 10 mM [2-¹⁴C] acetate and pyruvate. Fatty acids, CO₂, lactate and glyceride-glycerol yields were determined. An increase in dietary protein decreased (P<.05) glucose utilization and subsequent in vitro lipogenesis in PAT. A calculation of the role of the pentose cycle (PC) revealed a capacity to provide 60 to 90% of the NADPH required to support the observed rates of de novo fatty acid synthesis when glucose was a substrate. Several algorithms used to model PC acitivity in rat adipose tissue appeared to be inadequate for PAT because of a severe lack of triose phosphate pool equilibration and because of an apparent lack of CO₂ evolvement from the Krebs' Cycle. Tritium incorporation into fatty acids from [3-³H]glucose was related to ¹⁴CO₂ production from [1-¹⁴C]glucose and may be used to estimate glucose metabolism through the PC.     

Lipid metabolism in polychlorinated biphenyl-poisoned rats

To clarify the metabolism of lipids in polychlorinated biphenyl (PCB)-poisoned rats, in vivo and in vitro experiments were carried out. Male Wistar rats were separated into two groups, to one group a commercial flour diet was given and to the other group 500 ppm of PCB (Kanechlor-500) supplemented diet was given for 35 days. These animals were used for the following in vivo and in vitro experiments. (1) In vivo experiment: [¹⁴C] Acetate or [¹⁴C]glucose was administered to these rats and respiratory ¹⁴CO₂ and incorporation of ¹⁴C into the various lipid fractions in liver were determined. It was observed that the conversion into cholesterol from acetate or glucose was significantly accelerated in PCB-poisoned rats. However, no significant change was observed regarding respiratory ¹⁴CO₂ content between control and PCB-poisoned rats 90 min after administration of [¹⁴C]acetate or [¹⁴C]glucose. (2) In vitro experiment: Liver slices from control rats or PCB-poisoned rats were incubated with [¹⁴C]acetate or [¹⁴C]glucose for 90 min at 37°C and incorporation of ¹⁴C into various lipid fractions was investigated. In liver slices from PCB-treated rats, conversion into the [¹⁴C]sterol fraction from [¹⁴C]acetate and [¹⁴C]glucose was significantly accelerated.     

Structure elucidation and conformational analysis of gonadotropin releasing hormone and its novel synthetic analogue [Tyr(OMe), d-Lys, AzeNHEtGnRH: The importance of aromatic clustering in the receptor binding activity

The conformational properties of gonadotropin releasing hormone (GnRH) in dimethylsulfoxide-d₆ were investigated by nuclear Overhauser effect (nOe) enhancement studies and were compared with the conformational properties of its analogue [Tyr(OMe)⁵GnRH resulting after methylation of the tyrosine hydroxyl. Assignment of all backbone and side-chain protons was possible by combining information from intraresidue nOe studies with two-dimensional correlated spectroscopy (COSY/TOCSY) studies. Saturation of distinct proton resonances of the three aromatic residues Tyr, His, Trp, in clear areas of the NMR spectrum of GnRH resulted in interresidue enhancements of aromatic resonances indicating the proximity of the three aromatic rings. This spatial proximity is not observed in [Tyr(OMe)⁵]GnRH and is correlated with a lower receptor binding affinity in the rat pituitary (K_d = 1.53 ± 0.35 × 10⁻⁶ M) compared with that exerted by GnRH (K_d = 3.69 ± 0.89 × 10⁻⁹ M). However, substitution of Gly at position 6 of [Tyr(OMe)⁵]GnRH with d-Lys⁶ and further replacement of Pro at position 9 with the more rigid Aze residue [Tyr(OMe)⁵, d-Lys⁶, Aze⁹NHEt]GnRH significantly improved the binding affinity (K_d = 0.689 ± 10.15 × 10⁻⁹) and this may be due to the restoration of the ring cluster. Overall, the clustering of the aromatic rings observed in GnRH was not seen in [Tyr(OMe)⁵]GnRH and this conformational difference may be responsible for receptor recognition and higher binding of the parent peptide.     

Nonylphenol and Nonylphenol Ethoxylates in Fish,Sediment, and Water from the Kalamazoo River,Michigan

A survey measuring concentrations of nonylphenol (NP) and its ethoxylates (NPEs) in fish was performed in the Kalamazoo River, Michigan, USA, in 1999. Of 183 fish analyzed, 59% had no detectable NP or NPE. Detected concentrations were reported to range from 3.3 (limit of detection) to 29.1 ng NP/g wet weight. To further explore the means of exposure of NP and NPE in the fish, concentrations of NP and its mono-through tri-ethoxylates (NPE_1–3) were measured in fish, sediment, and water collected near two wastewater treatment plants on the Kalamazoo River in 2000. Samples were analyzed using exhaustive steam distillation with concurrent liquid extraction. Nonylphenol ethoxycarboxylates (NPE_1–3C) were also analyzed in water. Concentrations of NP and NPEs in fish were less than the method detection limits (MDLs) in all the samples except one fish, which contained 3.4 ng NP/g wet weight, just above the detection limit of 3.3 ng/g. Three of 36 sediments and 1 of 24 water samples contained detectable concentrations of NP or NPE₁. NPE₂, NPE₃, and NPEC were not detected in water samples. Received: 18 December 2001/Accepted: 13 May 2002     

Densities of dopamine D2 receptors are reduced in CNS regions of alcohol-preferring P rats

The densities of dopamine D₂ recognition sites labelled with [³H]sulpiride were determined in the caudate-putamen, nucleus accumbens (medial and lateral portions), olfactory tubercle, substantia nigra (pars reticulata and pars compacta), and ventral tegmental area (VTA) of alcohol-naive, selectively bred P (N = 7) and NP (N = 7) rats using quantitative autoradiography. The binding of [³H]sulpiride was 20–25% lower (P < 0.05) in the caudate-putamen, medial and lateral nucleus accumbens, and VTA of the P compared with the NP rats. No significant differences were observed between the P and NP rats in the olfactory tubercle or substantia nigra. [³H]Sulpiride binding, using standard membrane preparations, established with Scatchard analysis that the difference in the densities of D₂ recognition sites in the caudate-putamen between the P and NP rats was due to lower B_max values for the P line. The results indicate that the number of dopamine D₂ receptor sites is lower in several central nervous system regions of the P rats compared to NP rats.     

Persistence of methidathion in soils

Summary The organophosphorus insecticide, methidathion, degraded rapidly in a sandy loam, silt loam, clay loam and organic soil. Fifty percent of the initial applications decomposed in less than 2 weeks and more than 90% of the insecticide disappeared within 16 weeks. When soils were treated with methidathion containing¹⁴C in the ring or methyl side chain 40 to 66% of the radioactivity was expired as¹⁴CO₂ after 16 weeks. Over half of the remaining radioactivity could not be extracted from the soils while lesser amounts were recovered as the parent compound or as water-soluble degradation products.In fumigated soils 50% of the initial insecticide applications still remained after 16 weeks and less than 3% of the radioactivity was expired as¹⁴CO₂ which suggests that microorganisms are primarily responsible for the degradation of methidathion in soil.Scientific Paper 3340, College of Agriculture, Washington State University, Pullman. Supported by Public Health Service Grant CC 00258 and by Geigy Chemical Co., Ardsley, N.Y.     

Transport of organochlorine chemicals across cell membranes

[¹⁴C]DDT was absorbed into mixed lipid micelles during the digestion of olive oil by pancreatic lipase. Taurocholic acid and [¹⁴C]DDT combined together forming a mixed micelle was shown by Sephadex chromatography. DDT in mixed micelles is the apparent mode of intestinal absorption and was demonstrated by the uptake of these micelles using an everted gut sac technique. [¹⁴C]DDT in aqueous solution acted like a lipophilic drug in the manner in which it is passively transported across the cell walls of intestinal and mammary tissue. There was no inhibition of [¹⁴C]DDT uptake when HgCl₂, KCN, or Na Azide was added to the incubation solution. Also, competitive inhibition was not observed when TDE was added to the medium.     

Toxicokinetics and molecular interaction of [14C]-formaldehyde in rats

The excretion, tissue distribution, and binding of [¹⁴C]-formaldehyde were studied at different time intervals in male rats following a single intraperitoneal injection of 72 mg CH₂O (14.7 Ci)/ kg body weight. Within 30 min, 10% of the total dose was recovered in expired air as¹⁴CO₂ and by the end of 72 hr, 41% of the administered dose was eliminated through expired air. The total elimination of¹⁴CH₂O activity in urine and feces in 72 hr was 15%. Erythrocytes retained significant amounts of radioactivity, even at the end of 72 hr. Substantial levels of radioactivity were detected in most tissues one hr after administration, indicating a fast absorption and rapid distribution. Subcellular fractionation of the tissues showed that the highest levels of relative percent binding was in the microsomal fraction, whereas cytosol fractions contained lowest levels of bound radioactivity. DNA, RNA, protein and lipid fractions of liver and spleen tissues showed significantly elevated levels of¹⁴C-incorporation as compared to other tissues. Thein vivo incorporation of¹⁴C-activity showed an increased association of¹⁴CH₂O with RNA in all the tissues. The maximum registration of radioactivity in RNA was at 48 hr after administration. Significantly higher amounts of¹⁴C-activity were registered in DNA of all tissues. The maximum registration of radiolabel in DNA of most tissues was at 12 hr after the¹⁴CH₂O administration. The liver DNA showed maximal levels at 3 hr with a second peak at 48 hr.Substantial amounts of bound radioactivity in nucleic acids of all the tissues were observed even 72 hr after dosing. The relationship between macromolecular association and formaldehyde toxicity has been discussed.     

Effect of Critical Illness on Triglyceride Absorption

Background: Adequate nutrition support for critically ill patients optimizes outcome, and enteral feeding is the preferred route of nutrition. Small intestinal glucose absorption is frequently impaired in critical illness. Despite lipid being a major constituent of liquid nutrient administered, there is little information about lipid absorption during critical illness. Objectives: To determine small intestinal lipid, as well as glucose, absorption in critical illness compared with health. Materials and Methods: Twenty‐nine mechanically ventilated critically ill patients and 16 healthy volunteers were studied. Liquid nutrient (60 mL, 1 kcal/mL), containing 200 µL ¹³C‐triolein and 3 g 3‐O‐methyl‐glucose (3‐OMG), was infused directly into the duodenum at a rate of 2 kcal/min. Exhaled ¹³CO₂ and serum 3‐OMG concentrations were measured at timed intervals over 360 minutes. Lipid absorption was measured as the cumulative percentage dose (cPDR) of ¹³CO₂ recovered at 360 minutes. Glucose absorption was measured as the area under the 3‐OMG concentration curve. Data are median (range) and analyzed using the Mann‐Whitney U and Pearson correlation tests. Results: Lipid absorption was markedly less in the critically ill (cPDR¹³CO₂: patients, 22.6% [0%–100%] vs healthy participants, 40.7% [5.3%–84.7%]; P = .018). While glucose absorption was less at 60 minutes in the critically ill (3‐OMG₆₀: 13.2 [3.5–29.5] vs 21.1 [9.3–31.9] mmol/L·min; P = .003), this was not apparent at 360 minutes (3‐OMG₃₆₀: 92.7 [54.5–147.9] vs 107.9 [64.0–168.7] mmol/L·min; P = .126). There was no relationship between lipid and glucose absorption. Conclusion: Small intestinal absorption of lipid is diminished during critical illness.     

Fate of ethephon andN-methyl-2-pyrrolidone in soil and cotton plants

[¹⁴C]ethephon and [¹⁴C]N-methyl-2-pyrollidone (NMP) dissipated rapidly from three different soils. Half-life of [¹⁴C]ethephon was 3.3, 4.9, and 9.7 days, respectively, in clay, loam, and sand. The half-life of NMP was 3.9, 7.9, and 11.6 days, respectively in clay, loam, and sand when combined with nonlabeled ethephon, and was 4.0, 8.7, and 11.5 days, respectively, when applied alone to these soils. Soil treated with NMP contained less than 0.1 ppm NMP equivalents after 21 days and soils treated with [¹⁴C]ethephon contained less than 0.1 ppm ethephon equivalents after 28 days. In leaching studies with soils coated on thin layer chromatography plates, ethephon had frontal R_f values of 0.66, 0.59, and 0.20 in silt, loam, and clay, respectively, and streaked from the origin to near the solvent in sand. Frontal R_f values for NMP were 0.74, 0.65, 0.67, and 1.0 in silt, loam, clay, and sand. In cotton plants 14 and 21 days after treatment with [¹⁴C]ethephon or NMP, only a small portion of the applied doses were detected in plant tissues, and none remained on leaf surfaces after 21 days. An unidentified metabolite was detected along with NMP in leaf and terminal extracts of cotton plants treated with NMP.     

Laboratory Degradation Studies of <Superscript>14</Superscript>C-Atrazine and -Isoproturon in Soil from Sugarcane Cultivated Fields Under Kenyan Tropical Conditions

A study to compare the degradation rates of atrazine (6-chloro-N ²-ethyl-N ⁴-isopropyl-1,3,5-triazine-2,4-diammine) and isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] in soils from sugarcane fields with different practices of herbicides application was carried out. ¹⁴C-atrazine was poorly mineralized to ¹⁴CO₂ (1.10% ± 0.22%) after 139 days of incubation in soil without previous exposure to atrazine. In the same soil also with no previous isoproturon exposure isoproturon was mineralized to ¹⁴CO₂ by 7.70% ± 0.94%. Atrazine mineralization after 98 days was 13.4% ± 0.30% in soil which discontinued the use of atrazine in 1997 while it was 89.9% ± 1.23% in soil in which atrazine is currently being used. The isoproturon mineralization values were 7.24% ± 0.85% and 22.97% ± 0.96% in soil which discontinued atrazine and soil currently using atrazine, respectively.     

Using Acetone as Solvent to Study Removal of Anthracene in Soil Inhibits Microbial Activity and Alters Nitrogen Dynamics

Acetone is often used as a carrier to contaminate soil with polycyclic aromatic hydrocarbons (PAHs) and then to study the factors that control their removal. Acetone is an organic solvent that might affect soil processes. An alkaline saline (Texcoco soil) and an agricultural soil (Acolman soil) were amended with or without acetone, nitrogen + phosphorus (NP), and contaminated with anthracene at 520 mg/kg soil while emissions of CO₂ and N₂O and concentrations of NH₄ ⁺, NO₂ ^– and NO₃ ^– were monitored. The CO₂ emission rate decreased greater than 10 times in the soils amended with acetone. Emission of N₂O decreased 70 times in the Acolman soil amended with acetone and NP and 5 times in the Texcoco soil. The concentration of NH₄ ⁺ decreased in the unamended Acolman and Texcoco soil but increased when acetone was added in the first and remained constant in the latter. Acetone inhibited the increase in the amount of NO₃ ^– in the Acolman soil but not in the Texcoco soil. It was found that microbial activity as evidenced by the emission of CO₂, nitrification, and production of N₂O were inhibited by acetone. The amount of acetone used as solvent should thus be kept to a minimum, but it can be assumed that its effect on soil processes will be temporary, as microorganisms are known to repopulate soil quickly.     

Continuous osmotic minipump infusion of alcohol into brain decreases brain [Mg2+] and brain bioenergetics and enhances susceptibility to hemorrhagic stroke: An in vivo 31P-NMR study

³¹P-NMR spectroscopic studies were performed in vivo on brains of rats chronically infused for 7 and 14 days with 30% ethanol (in the third cerebral ventricle). Peripheral blood alcohol concentration (BAC) rose to between 16.5–30.5 mg/dl. Brain intracellular free Mg²⁺ ([Mg²⁺]_i) fell 33–39%, brain mitochondrial cytosolic phosphorylation potential (CPP) fell 31–48%, and brain phosphocreatine (PCr) fell approximately 15%; however, neither brain intracellular free hydrogen ion concentration (pHi) nor brain intracellular inorganic phosphate (Pi) were affected significantly by the chronic release of ethanol from the brain implants. Correlations were found between [Mg²⁺]_i and [PCr] and between [Mg²⁺]_i and CPP. Although brain free [MgADP] was not affected, [MgATP] fell by almost 20% accompanied by a 35–40% rise in free [ADP]. Interestingly, 14-day surgical implantation of 0.9% sterile saline into the third cerebral ventricle was associated with a 20% fall in brain [Mg²⁺]_i and a 35% fall in CPP; however, PCr, ATP, or pHi was not significantly altered. Systemic administration of 4 g/kg ethanol into the 7- and 14-day chronic ethanol animals resulted in a 9- and 12-fold increase in hemorrhagic stroke mortality compared to naive, control rats. Eating habits, grooming, gait and arterial blood pressure were not affected by the chronic brain implantation of ethanol. These data lend support to the notion, primarily based on epidemiologic evidence, that chronic exposure to alcohol can pose a high risk for hemorrhagic stroke. Our alcohol pump-implanted rats also might provide a new model of slow, moderate alcohol intoxication.     

The 14C-aminophenazone breath test in pesticide workers

Summary In 59 workers between the ages of 22 and 66, who had been exposed to pesticides, and 31 healthy controls between the ages of 22 and 28, the hepatic demethylation capacity was studied using the aminophenazone breath test (ABT). The ABT was carried out in two versions (version A: 111 kBq ¹⁴C-aminophenazone per 630 mg, version B: 111 kBq ¹⁴C-aminophenazone per 3 mg). The amount of ¹⁴CO₂ expired per mmol CO₂ per 70 kg body weight (b. w.) detected 1 h after ¹⁴C-aminophenazone intake was used to determine the demethylation capacity of the liver. The amount of expired ¹⁴CO₂ depended on the ingested dose (B > A). The ¹⁴CO₂-values measured in 13 controls did not differ from those obtained in 37 subjects who had been exposed to pesticides for 650h per year on the average [649 vs 726 DPM/mmol · 70 kg b. w. (A)]. The ¹⁴CO₂-values obtained in 22 subjects exposed to pesticides for 990 h per year on the average (B) were lower than those obtained in 18 healthy controls (736 vs 1024 DPM/mmol CO₂·70kg; P < 0.05). The ¹⁴CO₂-values of ABT decreased with increasing length of exposure per year (B; r = –0.51, P < 0.05).     

Leaching and degradation of 4-aminopyridine-14C in several soil systems

Leaching and degradation of 4-aminopyridine (a frightening agent for protecting grain crops from blackbirds) was studied in seven soils. Carbon-14-labeled 4-aminopyridine was strongly adsorbed onto soil colloids, with the degree of adsorption related to pH. Application of seven in. of simulated rainfall over 20 days to surface-treated alkaline soils leached 0.02% to 0.18% of the¹⁴C; radioactivity was detected in the runoff from only one of the four acidic soils. Degradation of 4-aminopyridine-¹⁴C to¹⁴CO₂ was negligible in soils incubated up to two months under anaerobic conditions. Under aerobic incubation, there was a one-week lag before extensive breakdown began. Degradation rates increased with increasing temperature and soil moisture during incubation, but soil composition had a greater influence. After three months at 30°C and 50% moisture, evolution of¹⁴CO₂ ranged from 0.4% for a highly acidic loam (pH 4.1) to more than 50% for a lighter-textured, alkaline, loamy sand (pH 7.8); the half-life of 4-aminopyridine in soils under these test conditions ranged from 3 to more than 22 months. A theoretical scheme is presented for the degradation of 4-aminopyridine in soils.     

Metabolism of 4-chlorophenyl methyl sulfide and its sulfone analog in cattle and sheep

Lactating cattle were treated with [¹⁴C] 4-chlorophenyl methyl sulfide (CPMS) or it's [¹⁴C] sulfone analog (CPMSO₂) as a single oral dose equivalent to 10.0 mg/kg b.w. Both compounds were absorbed through the gastrointestinal tract, CPMS was rapidly oxidized to CPMSO₂ in the CPMS-treated cow, but CPMSO₂ was quite resistant to further metabolism and it was excreted slowly by the kidneys. Thus, CPMSO₂ tended to circulate within the body and, after four days, was distributed more-or-less equally throughout the tissues of the body. Oral treatment of sheep with [¹⁴C] CPMSO₂ confirmed that the compound is slowly eliminated from the body of ruminants, although a sheep treated with a very low dose of the compound (0.022 mg/kg) eliminated radiocarbon (primarily through the urine) at a considerably faster rate than was observed at a much higher dosage (22 mg/kg). In the treated cattle, 1 to 3% of the administered doses was secreted into milk within a 4-day post-treatment period, and essentially all of this was in the form of CPMSO₂. Radiocarbon extracted from feces of the treated cattle was likewise totally in the form of CPMSO₂. Three major products were excreted into urine of the treated cattle, CPMSO₂ and two major metabolites, one of which was partially characterized as an hydroxylated CPMSO₂ derivative on the basis of GLC/mass spectral data. Our studies in ruminants with these environmental contaminants have implications for evaluating the toxicological significance of some structurally similar pesticides that may be metabolized to CPMSO₂ in mammals.