Under Office of Prevention, Pesticides and Toxic Substances draft guidelines, CD weanling F0 rats (30 of each gender per group) inhaled tertiary amyl methyl ether vapor at 0, 250, 1500 or 3000 ppm 5 days a week and 6 h a day for 10 weeks, with vaginal cytology evaluated for weeks 8-10. The F0 animals then produced F1 offspring, with exposure 7 days a week from mating through to lactation. During the F1 prebreed exposure period, vaginal patency, preputial separation (PPS) and vaginal cytology were evaluated. The F1 animals were mated, with F2 anogenital distance measured on postnatal day zero. At F2 weaning 30 of each gender per group were selected for postwean retention, with no exposures, through vaginal patency and PPS. Body weights, feed consumption and clinical signs were recorded throughout the study. Adult F0 and F1 systemic toxicity was present at 1500 and 3000 ppm. Minor adult male reproductive toxicity was present at 3000 ppm. There were no adult effects on vaginal cyclicity, estrous cycle length, mating, fertility, pregnancy, gestational length or ovarian and uterine weights. There were no treatment-related gross or histopathologic findings in parental male or female systemic or reproductive organs. The F1 and F2 offspring toxicity was present at 1500 and 3000 ppm. The no-observable-adverse-effect level for adult systemic and offspring toxicity was 250 ppm and 1500 ppm for male reproductive toxicity (females at >3000 ppm).

Air Pollutants↗

PubMedDate not supplied

Attenuation of 2-methoxyethanol and methoxyacetic acid-induced digit malformations in mice by simple physiological compounds: implications for the role of further metabolism of methoxyacetic acid in developmental toxicity.

The ethylene glycol ether 2-methoxyethanol (ME) and its oxidation product methoxyacetic acid (MAA) are selective embryotoxins and equipotent as inducers of digit malformations when given by gavage to pregnant Crl:CD-1 ICR BR mice on gestation day 11. Earlier observations showed that the teratogenic effects were attenuated by delayed administrations of ethanol given at a time when all ME is already converted to MAA. That outcome suggested that acetate from ethanol catabolism might compete with methoxy-acetate in biosynthetic reactions relevant to MAA-induced malformations. Furthermore, 14C derived from [1,2-14C]-ME or [1-14C]-MAA is incorporated into all macromolecular fractions of the embryo, and 14C is exhaled by the dam in 14CO2. Those data indicate that 14C derived from 14C-ME catabolism enters into many metabolic reactions. The present study examined acetate and other simple physiological compounds with close relationships to carbon and one-carbon moiety metabolic pathways for their ability to attenuate digit malformations upon concomitant dosing with ME. All of the agents examined reduced the teratogenic effect significantly with a potency rank order of formate much greater than acetate = glycine much greater than D-glucose. The common link for their efficacy may be the one-carbon moiety oxidation pathway that involves tetrahydrofolic acid as a catalyst of one-carbon transfer into purines and thymidylate. Carbon from all of the attenuators administered is incorporated into those bases and then into DNA. It appears as if methoxyacetate enters into biochemical reactions analogous to those of acetate. This speculation is supported by the metabolic fate of 14C from 14C-ME in dam and embryo. Based on the indirect evidence obtained with all of the simple compounds that attenuate the ME-induced digit malformations, we postulate that abnormal macromolecules are generated by anabolic reactions and that those products disrupt normal paw development.

Abnormalities, Drug-Induced↗

PubMedDate not supplied

Choline metabolism in placenta: evidence for the biosynthesis of phosphatidylcholine in microsomes via the methylation pathway.

Microsomes from human, mouse and rat placenta were found to contain enzymatic activity which methylates the phospholipids phosphatidylethanolamine (PE), phosphatidyl-N-monomethylethanolamine (PMME) and phosphatidyl-N,N-dimethylethanolamine (PDME) to form phosphatidylcholine (PCh) with 3H-methyl-S-adenosyl-l-methionine as the methyl donor. The three labelled reaction products were isolated by solvent extraction and separated on thin-layer chromatography (TLC) plates. The endogenous methyltransferase activity was low, indicating that the methylation pathway is quantitatively not important for the synthesis of free choline to meet the fetal needs. The distribution of 3H-methyl among PMME, PDME and PCh revealed fairly even labelling of all products when analysed by TLC. Addition of authentic PE, PMME and PDME to a level of approximately 2.5 mM stimulated the incorporation of 3H-methyl into the total lipid-soluble fraction with all three substrates, but was most pronounced with PMME. Present observations suggest that all three methylation steps were catalysed by one enzyme with a pH optimum of 9.0 in a reaction that does not require Mg++.

Animals↗

PubMedDate not supplied

Effect of different sampling designs on outcome of endocrine disruptor studies.

In this article, we demonstrate how sampling strategy can influence the outcome of endocrine disruptor studies. In a study of the weak xenoestrogen bisphenol A (BPA), possible treatment-related effects on ventral prostate (VP) fresh weight were found in rat offspring at 6 months of age when only one or two male pups were randomly selected from each litter. In subsequent BPA and di-n-butyl phthalate studies, large intralitter variability of this specific end point was apparent when the VP weights from entire litter complements were examined. We modeled the effects of sampling 1, 2, or 3 pups from each litter using the full-litter complement data. When one pup was randomly selected, a substantial percentage of incorrect conclusions about the presence or absence of treatment effects occurred. These statistical modeling analyses raise significant concern about the selection of one pup per litter for highly variable end points.

Animals↗

PubMedDate not supplied

Characterization of urinary metabolites from [1,2,methoxy-13C]-2-methoxyethanol in mice using 13C nuclear magnetic resonance spectroscopy.

2-Methoxyethanol (2-ME) is an industrial solvent that induces developmental and testicular toxicity in laboratory animals. Oxidation of 2-ME to 2-methoxyacetic acid (2-MAA) is required for the generation of these adverse effects. The urinary metabolites of 2-ME were investigated to characterize the fate of 2-ME and 2-MAA. 13C NMR spectroscopy was used to detect and assign metabolites in the urine of pregnant CD-1 mice following administration of 250 mg/kg of [1,2,methoxy-13C]-2-ME. Two-dimensional NMR methods were used to correlate signals from the labeled carbons in each 2-ME metabolite and to determine the number of hydrogens attached to each carbon. Structures were assigned from the NMR data together with calculated values of shift for biochemically feasible metabolites and by comparison to standards. Pathways involved in forming metabolites assigned in this study include transformation of 2-ME via ethylene glycol, conjugation with glucuronide or sulfate, and oxidation to 2-MAA. Additional metabolites were assigned that can be formed from further conversion of 2-MAA to glycine and glucuronide conjugates, as well as metabolites derived from the incorporation of 2-methoxyacetyl CoA derivatives into intermediary metabolism. Elucidation of the further metabolism of 2-MAA may be important for understanding the mechanisms by which 2-ME induces adverse effects.

Animals↗

PubMedDate not supplied

[Ten year follow-up after single incision anterior cruciate ligament reconstruction using patellar tendon autograft].

AIM: We evaluated 74 patients 10 years after arthroscopically assisted ACL reconstruction using the central third of the patellar tendon as autograft. METHOD: IKDC, Tegner and Lysholm scores were used for clinical evaluation. Ligament stability was tested using the Rolimeter instrument. For statistics we used the Chi square test. RESULTS: At follow-up the Tegner activity level was 5.2, the Lysholm score was 93.6 points. Subjective assessment for function was rated normal or nearly normal in 83.7 %, for stability in 71.6 %. The side-to-side difference measured with the Rolimeter was normal in 87.8% and nearly normal in 12.2 %. Pivot shift was proven to be negative in 94.6 %. 29.7 % of patients showed degenerative changes in X-rays at follow-up. There was a significant correlation between time interval from injury to surgery and the grade of degenerative changes. Arthrosis significantly correlates with the rate of meniscus injury. Acute operative treatment increases the rate of arthrofibrosis significantly. CONCLUSION: To avoid osteoarthrosis we recommend an early (subacute) ACL reconstruction and meniscus refixation in the case of meniscus injury.

Adult↗

PubMedDate not supplied

Effect of chloramphenicol pretreatment on malathion-induced acute toxicity in the rat.

Pretreatment of rats with chloramphenicol (CAP) (100 mg/kg, ip) 30 min prior to a single oral LD50 dose of malathion (MTH) at 340 mg/kg completely protected against MTH-induced signs of cholinergic toxicity. Pretreatment with CAP also decreased the extent and duration of MTH-induced inhibition of cholinesterase (ChE). It was previously established that CAP inhibits (1) the cytochrome-P-450-catalyzed oxidative desulfuration of methylparathion to the much more toxic oxygen analog methylparaoxon (MOX) and (2) the carboxyesterase in rat liver. Since carboxyesterases account for 60% or more of the catabolism of MTH in the rat, the present results were surprising. Thus it appears that the inhibition of MTH toxicity by CAP pretreatment is attributable to inhibition by CAP of the metabolic activation of MTH to MOX.

Animals↗