Thermally induced formation of polychlorinated dibenzofurans from Aroclor 1254-contaminated mineral oil.

Numerous laboratory simulations and real-world events have demonstrated the thermal conversion of neat or high concentration of PCBs into the much more toxic PCDFs. Since millions of mineral oil transformers currently in service contain PCB concentrations in the 50 to 5000 ppm range, the thermal behavior of dilute PCB solutions is of practical and regulatory significance. In this work, neat Aroclor 1254 and 5000 ppm Aroclor 1254 in mineral oil were subjected to pyrolysis and combustion under a range of experimental conditions to define parameters resulting in maximal PCDF yields. The dependence of PCDF yield on Aroclor 1254 concentrations was then investigated in the 5000 to 50 ppm range. Combustion experiments demonstrated that PCDF yields expressed as micrograms PCDF/gram PCB were independent of concentration range, confirming that the process is kinetically first order in PCB. Much lower yields of PCDF were observed in the open tube pyrolysis experiments, as compared to combustion experiments and to earlier and concurrent sealed tube experiments. Slightly improved yields were observed in the pyrolysis experiments at lower concentrations, suggesting the existence of a PCB or PCDF destruction process of higher than first order kinetics. In all cases, yields expressed as micrograms PCDF/gram mixture were sharply and monotonically lower as concentrations decreased between neat or 5000 ppm Aroclor 1254 and 50 ppm Aroclor 1254.

The effects of Love Canal soil extracts on maternal health and fetal development in rats.

The effects of a solvent extract of the surface soil of the Love Canal chemical dump site, Niagara Falls, New York, and of a natural extract, or leachate, which is drained from the canal for treatment, on the maternal health and fetal development were determined in rats. The solvent extract, which was contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (2, 3,7,8-TCDD) at 170 ppb and numerous other chlorinated organic compounds with the primary identified components being the isomers of benzenehexachloride (BHC), was dissolved in corn oil and administered by gavage to pregnant rats at 0,25,75, or 150 mg crude extract/kg/day on Days 6-15 of gestation. A 67% mortality was observed at the highest dose. The rats were sacrificed on Day 20. Dose-related increases in relative liver weight accompanied by hepatocyte hypertrophy were observed at all dose levels. Fetal birthweight was decreased at 75 and 150 mg extract/kg/day. No major treatment-related soft tissue or skeletal malformations, except for delayed ossification, were observed. Based on literature values for BHC, all of the observed toxicity could be accounted for by the BHC contaminants of the extract. The crude organic phase of the leachate was administered to pregnant rats at 0,10,100, or 250 mg/kg/day as described above. Maternal weight gain decreased at 100 and 250 mg/kg/day, accompanied by 5 and 14% maternal mortality, and 1 and 3 dead fetuses, respectively. Early resorptions and the percentage of dead implants increased whereas fetal birthweights were decreased at 250 mg/kg/day. No major treatment-related soft tissue or skeletal malformations, except for delayed ossification, were observed. The primary components of the complex leachate by mass were tetrachloroethanes; however, 2,3,7,8-TCDD, which was present at 3 ppm, probably accounted for all the observed toxicity.

5'Chloropuromycin. Inhibition of protein synthesis and antitrypanosomal activity.

A facile, two-step conversion of puromycin aminonucleoside (PAN) into 5'-deoxy-PAN (5) via 5'-chloro-5'-deoxy-PAN (1) was accomplished. Replacement of the 5'-OH group of PAN with H or Cl resulted in the elimination of kidney toxicity associated with the administration of PAN. The corresponding puromycin derivatives, 5'-chloro-5'-deoxypuromycin (4) and 5'-deoxypuromycin (6), derived from 1 and 5, respectively, were compared in a ribosomal peptidyltransferase assay. Both compounds were excellent substrates for the transpeptidation reaction, confirming our previous observations with 6 that the 5'-OH of puromycin is not essential for activity at the ribosomal level. Thus, 4 represents a new puromycin derivative that retains puromycin-like activity at the ribosomal site but is capable of releasing only a nonnephrotoxic aminonucleoside upon enzymatic release of the p-methoxyphenylalanyl side chain. The chloro derivative 4 exhibited significant antitrypanosomal activity in mice infected with Trypanosoma rhodesiense. The 5'-deoxy derivative 6 was inactive against trypanosomes.

1,2,4-Triazole amino nucleosides. 1-beta-D-3'-Amino-3'-deoxyribofuranosyl-1,2,4-triazole-3-carboxamide and related nucleosides.

The synthesis of 1-beta-D-3'-amino-3'-deoxyribofuranosyl-1,2,4-triazole-3-carboxamide--the 3'-amino analogue of ribavirin--and five related nucleoside analogues is described. Each analogue exhibited LD50 concentrations greater than 100 microgram/mL against P-388 mouse lymphoid leukemia cells in tissue culture. Antiviral testing indicated that none of the compounds exhibited significant activity.