* Chemistry and Life Sciences, Center for Life Sciences and Toxicology, Herman Laboratory Building, Research Triangle Institute, P.O. Box 12194, Research Triangle Park, North Carolina 277092194; and
Developmental and Reproductive Toxicology Group, National Toxicology Program, National Institute of Environmental Health Sciences, P.O. Box 12233, Research Triangle Park, North Carolina 27709
Received December 18, 2001; accepted April 29, 2002
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ABSTRACT |
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Key Words: formamide; developmental toxicity; teratogenicity; rabbits; morphological development.
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INTRODUCTION |
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FORM is generated in vivo as a metabolite of structurally related alkylformamides, which have medicinal and/or industrial uses. In mice, FORM was one of several metabolites found in the plasma and urine after exposure to N-methylformamide (Gescher et al., 1982; NMF; Ross et al., 1981
), a potential antitumor medication studied in recent clinic trials (Cody et al., 1992
; Del Bufalo et al., 1994
). NMF is also a potential photoproduct of the aqueous herbicide, fluridone, but environmental concentrations are likely to be quite low (ppb range; West and Turner, 1988
). More importantly, FORM is found as one of the major metabolites following exposure to N,N-dimethylformamide (DMF; Major et al., 1998
; Mraz et al., 1989
; Ogata et al., 1997
; Saillenfait et al., 1997
), another widely used industrial solvent (Cheng et al., 1999
; Lareo and Perbellini, 1995
; Sakai et al., 1995
; ). In human volunteers exposed to DMF by inhalation, a common route of occupational exposure, FORM accounted for
824% of the total dose excreted in the urine (Mraz et al., 1989
). In laboratory animals (mouse, rat, hamster), FORM accounted for
838% of the total dose (Mraz et al., 1989
).
The literature pertaining to the toxic effects of alkylformamides and their metabolites is extensive, and a thorough review exceeds the scope of the present manuscript. Developmental toxicity of NMF and DMF has been reported in laboratory animals; see the review by Kennedy (2001) and more recent studies, including those of Hellwig et al.(1991); Kelish et al.(1995); Rickard et al.(1995); Liu et al.(1989); and Saillenfait et al.(1997). For instance, NMF has been shown to cause increased embryolethality after nose-only inhalation exposure of maternal CD® rats to 150 ppm, 6 h/day on GD 7 to 16 (vaginal sperm = GD 1) (Rickard et al., 1995). In addition, reduced fetal weight was observed at 50 and 150 ppm, while increases in fetal malformations, including microphthalmia, anophthalmia, fused ribs and/or vertebrae, and distended brain ventricles were noted at 150 ppm. Oral gavage administration of NMF to pregnant rats on GD 6 to 15 (sperm detection = GD 0) produced reduced fetal viability and body weight, and an increased incidence of cephalocele and sternoschisis at 75 mg/kg/day in the presence of decreased maternal food consumption and weight gain (Liu et al., 1989
). In rabbits, oral gavage administration of 50 mg/kg/day NMF on GD 6 to 18 produced similar results (Liu et al., 1989
). Rabbit fetuses exhibited increased incidences of gastroschisis, cephalocele, domed head, and anomalies of the skull and sternum. Hellwig et al.(1991) reported that oral gavage administration of 0, 166, 503, and 1510 mg/kg/day DMF to rats, on GD 6 to 15, produced increased mid-gestation embryolethality at the high dose, in the presence of reduced maternal body-weight gain. Surviving fetuses had one or more anomalies including anasarca, tail aplasia, micrognathia, and anomalies of the ribs, sternum, and vertebral column. NMRI mice, exposed orally to 182 or 548 mg/kg/day DMF by gavage on GD 6 to 15, exhibited decreased fetal body weight at both doses and an increase in the total incidence of anomalies (malformations and variations) at the high dose (Hellwig et al., 1991
).
The reproductive and developmental toxicity of FORM has previously been investigated in mammalian species, including rats, mice, and rabbits (BASF, 1974a,b
; DuPont, 1967, 1992; Fail et al., 1998
; Gliech 1974
; Kennedy, 2001
; Merkle and Zeller, 1980
; Oettel and Frohberg, 1964
; Oettel and Wilhelm, 1957
; Thiersch, 1962
, 1971
). However, treatment periods in previous developmental toxicity testing and research focused either on critical periods of morphological development or covered the period of organogenesis. Merkle and Zeller (1980) evaluated pregnant Chbb:HM rabbits exposed to FORM by gavage on GD 6 through 18, at doses of 0, 23, 79, or 227 mg/kg/day. No significant maternal or developmental toxicity was observed at 23 mg/kg/day. Decreased maternal body weight, decreased fetal-body weight, and an increase in fetal morphological anomalies were observed at 79 mg/kg/day, whereas maternal mortality (80%) and no live litters were observed at 227 mg/kg/day.
None of the developmental toxicity studies conducted prior to 1998 exposed animals throughout the embryo/fetal period, as recommended by current guidelines for prenatal developmental toxicity testing (U.S. EPA, 1997, 1998
; U.S. FDA, 1994b
). Thus, current testing strategies call for a longer gestational exposure period and thereby eliminate the recovery period for potentially reversible endpoints such as maternal or embryo/fetal body weight. In rats, for example, oral exposure to FORM by gavage during major organogenesis (GD 615) was associated with decreased fetal body weight and increased fetal malformations in rats, including malformations of the vertebral column and ribs at 318 mg/kg/day (Covance Research Products, Inc., Denver, PA).), but not at 177 mg/kg/day (BASF, 1974b
, 1983
). However, in a more recent study, FORM was evaluated for developmental toxicity in Sprague Dawley rats after gavage administration of 0, 50, 100, or 200 mg/kg/day on GD 6 through 19 (George et al., 2000
; NTP, 1998b
). Using this extended treatment regimen, FORM did not affect prenatal viability or incidences of fetal malformation or variations, although average fetal body weight/litter was decreased at 100 and 200 mg/kg/day. Fetal body weight was affected at lower daily doses than in previous studies, possibly due to the longer total exposure period and lack of a recovery period between cessation of treatment and termination. The maternal toxicity NOAEL was 100 mg/kg/day and the LOAEL was 200 mg/kg/day. The developmental toxicity NOAEL was 50 mg/kg/day and the LOAEL was 100 mg/kg/day. Thus, modification of the study design may influence dose range selection as well as the overall pattern of results, including the critical endpoints that define the NOAEL/LOAEL values.
The widespread uses of FORM, as well as prior evidence of developmental toxicity for FORM and structurally related alkylformamides, warranted determination of developmental toxicity LOAEL and NOAEL values based on a study in nonrodents, designed in accordance with current regulatory guidelines. The results of the proposed investigation provide additional information relevant to the safety assessment of FORM exposure during pregnancy, with particular focus on in utero growth, viability, and morphological development. The present study was designed to establish NOAELs and LOAELs for maternal and developmental toxicity in a nonrodent species, following daily oral exposure by gavage throughout the embryo/fetal period. Because FORM had been previously studied using the shorter exposure period (i.e., major organogenesis) required by predecessor testing guidelines, the influence of the longer exposure period on dose-range selection and outcome for various toxicity endpoints in rabbits was also of interest.
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MATERIALS AND METHODS |
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The experimental animals were female Hra:(NZW)SPF; New Zealand White (NZW) rabbits (Covance Research Products Inc., Denver, PA). Prior to arrival at RTI, animals were individually identified by the supplier with a unique animal identification number, through the use of a subcutaneously implanted microchip (Avid, Norco, CA). A separate shipment of 48 animals was used for each replicate of the study. Prior to shipment to RTI, females were naturally mated at the vendor's facilities. For each replicate, animals arrived at RTI on GD 1 (n = 24) or GD 2 (n = 24). Animals were maintained in quarantine for 3 days after arrival at RTI. Female rabbits were assigned to treatment groups by stratified randomization for body weight on GD 0, as reported by the vendor, so that mean body weight on GD 0 did not differ among treatment groups (Fig. 1). Maternal body weight for confirmed pregnant females used in this study ranged from 2894 to 3919 g on GD 0 in Replicate I, and 3255 to 4185 g on GD 0 in Replicate II. The study design included two consecutive breeding dates for each replicate. Females were housed singly in stainless steel cages with mesh flooring (Hoeltge, Inc., Cincinnati, OH). Food (Purina Certified Rabbit Chow [#5322], PMI, St. Louis, MO) was rationed at
65 g for the first 24 h after arrival (GD 1 or 2). For the following 24 h, females received
125 g of food, which was available ad libitum for all females from GD 3 to scheduled sacrifice. Tap water (City of Durham, NC) was provided ad libitum to all females throughout the study. The light cycle (12 h light:12 h dark), temperature, and relative humidity in the animal rooms were monitored, recorded, and controlled (Siebe/Barber-Coleman Network 8000® System with SIGNAL® Software [Revision 4.1], Siebe Environmental Controls (SEC)/Barber-Colman Company, Loves Park, IL) throughout the study. The ranges for temperature and relative humidity were 63.971.3°F and 30.780.4% relative humidity, respectively, for Replicate I, and 63.969.4°F and 27.069.7% RH, respectively, for Replicate II.
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Dose selection was based on a screening study in which NZW rabbits (8 animals per group) were exposed to FORM (0, 10, 20, 40, 80, or 120 mg/kg/day) by gavage from GD 6 through 29 (NTP, 1998c). At 120 mg/kg/day, 3 females aborted (GD 25) or delivered early (GD 27 or 29). One maternal death occurred at each of the 40- and 80-mg/kg/day groups, but there were no deaths in any other group. At 120 mg/kg/day, maternal relative food intake was decreased during all measurement periods between GD 12 and 24, but the data were insufficient to evaluate this high-dose effect between GD 24 and 30. Maternal body gain was significantly decreased at the high dose for GD 12 to 15. Incidences of prenatal mortality and morphological anomalies were not affected. Gravid uterine weight and live litter size were unaffected. Average fetal body weight per litter was 106, 107, 104, 94, and 83% of the control weight in the 10-through 120-mg/kg/day groups, respectively. Although this apparent dose response did not reach statistical significance, the reduction of fetal body weight at the high dose was considered to be a biologically relevant response to FORM exposure. There were no external morphological anomalies noted in that study. Based on these results, doses of 0, 35, 70, and 140 mg/kg/day were selected for the present developmental toxicity study. The high dose of 140 mg/kg/day was chosen since no persistent clear-cut maternal toxicity was noted at 120 mg/kg/day in the screening study.
Observations.
Naturally mated does were weighed on GD 0 (vendor), and food and body weights were recorded on GD 3, 6, 9, 12, 15, 18, 21, 24, 27, 29, and 30. In addition, body weight was recorded immediately following termination on GD 30. Clinical signs were recorded once daily prior to initiation of treatment, and twice daily during the treatment period. Following termination by intravenous injection (marginal ear vein) of sodium pentobarbital on GD 30, maternal liver and gravid uterine weights were measured. Uterine contents were evaluated for the number of implantation sites, resorptions, late fetal deaths (i.e., fetuses with discernible digits and weighing greater than 10.0 g, but displaying no vital signs at the time of uterine dissection), and live fetuses. The uterus was stained to reveal possible early resorptions (Salewski, 1964) when visible evidence of pregnancy was not apparent.
Live fetuses were dissected from the uterus and immediately terminated by intraperitoneal injection of sodium pentobarbital. Each live fetus was counted, weighed, and examined for external morphological abnormalities, including cleft palate. Fetal carcasses were sexed and examined for visceral morphological abnormalities using a fresh tissue dissection method (Staples, 1974; Stuckhardt and Poppe, 1984
). Approximately one-half (50%) of the fetal carcasses were decapitated prior to dissection. Fetal heads were fixed and decalcified in Bouin's solution and subsequently examined using a free-hand sectioning technique (Wilson, 1965
). All fetal carcasses were eviscerated and the skeletons macerated and stained with alcian blue/alizarin red S stain (Marr et al., 1988
). All fetal skeletons were examined for skeletal morphological abnormalities. Due to the fact that
50% of the fetal carcasses had been decapitated, the skeletal structures of the head were only examined for intact carcasses.
Statistical analyses.
The unit for statistical measurement was the pregnant female or the litter. Quantitative continuous data (e.g., maternal body weights, fetal body weights, feed consumption, etc.) were compared among treatment groups by parametric statistical tests whenever Bartlett's test for homogeneity of variance was not significant. Statistical analyses were based on SAS® software (SAS Institute, Inc., 1989a,b
, 1990a
, b
,c
, 1992
, 1996
, 1997
) available at RTI.
General linear models (GLM) procedures were applied to the analyses of variance (ANOVA) and the tests for linear trend. Prior to GLM analysis, an arcsine-square root transformation was performed on all litter-derived percentage data: e.g., percent resorptions per litter, percent malformations per litter, and percent variations per litter (Snedecor and Cochran, 1967). For litter-derived percentage data, the ANOVA was weighted according to litter size. When a significant (p < 0.05) main effect for dose or replicate occurred, Dunnett's multiple comparison test (Dunnett, 1955
, 1964
) was used to compare each treatment group to the control group for that measure. A one-tailed test (i.e., Dunnett's) was used for all pair-wise comparisons to the vehicle control group, except that a 2-tailed test was used for maternal body and organ weight parameters, maternal feed consumption, fetal body weight, and percent males per litter.
Data for any measure that showed a significant (p < 0.05) dose x replicate interaction in a 2-way (dose x replicate) ANOVA were presented as mean ± SEM for each cell in the ANOVA design. Dose effects within each replicate were further evaluated using a one-way ANOVA, test for linear trend, and Dunnett's test.
All nominal scale measures were analyzed by a Chi-square test for independence for differences among treatment groups (Snedecor and Cochran, 1967) and by the Cochran-Armitage test for linear trend on proportions (Agresti, 1990
; Armitage, 1955
; Cochran, 1954
).
The alpha level for each statistical comparison was 0.05, and the significance levels for trend tests and pair-wise comparisons were reported as p < 0.05.
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RESULTS |
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The number of implantation sites per litter exhibited a decreasing trend that appeared to be due to effect in the surviving animals in the high-dose group (Table 2). No significant differences were observed among groups for the percent resorptions per litter, percent late fetal deaths per litter, and percent non-live (late fetal deaths and resorptions) implants per litter, although a significant increasing trend was noted for the percent non live implants per litter (Table 2
). Values for these parameters were higher and exhibited more variability than the control group. Examination of historical control data indicated that the values for the percent late fetal deaths per litter and percent non-live implants per litter were higher than maximum historical values (1.99 ± 1.12 and 16.15 ± 10.34, respectively), suggesting an increase in late gestational deaths in the surviving high-dose animals. The average numbers of live fetuses per litter in the low- and mid-dose FORM-treated groups were 98 and 89% of the control mean, respectively, and neither group was significantly different from the controls (Table 2
). However, the average number of live fetuses per litter was significantly reduced to 66% of the control value in the high-dose group. Male and female fetal body weight per litter exhibited decreasing trends and were both reduced to 85% of their control values at the high dose (Table 2
). This reduction was statistically significant for males and for both sexes combined, but not for females. The lack of statistical significance for the reduction in female fetal body weight at the high dose, most likely due to a smaller number of litters with female fetuses (7 vs. 8 for males or 9 for both sexes combined), does not invalidate the biological significance of this effect.
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DISCUSSION |
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In the present developmental toxicity study, naturally mated NZW rabbits were dosed by gavage with FORM (0, 35, 70, or 140 mg/kg/day) on GD 6 through 29. Maternal clinical signs of toxicity were limited to the reduction in or absence of fecal output, primarily at the high dose. However, maternal mortality during late gestation was increased at the high dose. In addition, abortion or early delivery was observed to be 4-fold higher in the high-dose group compared to the low- or mid-dose groups. Maternal body weight and weight gain, relative maternal feed consumption, and gravid uterine weight were also decreased at the high dose. In the absence of any other indicators of maternal toxicity (feed consumption, body weight, etc.), the transient decrease in maternal body weight on GD 18 to 21 was not considered to be a significant indication of maternal toxicity at this dose level. Liver weight (absolute and relative) was unaffected by treatment with FORM. FORM decreased fetal survival, live litter size (66% of control) and male fetal-body weight (85% of control) at the high dose, but did not affect the incidence of fetal malformations (external, visceral or skeletal) among survivors in the high-dose group, or at any other dose. Under the conditions of the present study, and based on the mg/kg/day treatment level, the rabbit conceptus was not more sensitive than the adult to the adverse effects of FORM administered orally throughout the embryo/fetal period of gestation. Thus, in the present developmental toxicity study, the NOAELs for both maternal and developmental toxicity were 70 mg FORM/kg/day administered on GD 6 through 29.
Based on similar treatment levels and similar parameters, the results of the present study can be compared to those of Merkle and Zeller (1980; Table 4). In the Merkle and Zeller study (1980), pregnant Chbb:HM rabbits were exposed to FORM by gavage on GD 6 through 18, at doses of 0, 23, 79, or 227 mg/kg/day. The results of the two studies agree well at the low doses and the high doses. No significant maternal or developmental toxicity was observed at either 23 mg/kg/day (Merkle and Zeller, 1980
) or at 35 mg/kg/day in the present study. At 140 mg/kg/day, the high dose in the present study, maternal mortality, a decrease in maternal body weight, a decrease in gravid uterine weight, and decreased fetal viability and fetal body weight were observed, whereas Merkle and Zeller (1980) observed 80% maternal mortality and no live litters at their higher dose of 227 mg/kg/day. Although the mid doses for these studies are close (70 mg/kg/day for the present study vs. 79 mg/kg/day for Merkle and Zeller, 1980
), the data do not agree as well as would be expected. In the present study, no persistent adverse maternal or developmental effects were observed at 70 mg/kg/day, whereas Merkle and Zeller (1980) observed decreased maternal body weight, decreased fetal body weight, and an increase in fetal morphological anomalies. The reason for the lack of concordance in these two studies at the mid dose is not clear, but could likely be due to the use of rabbits of different strains. The addition of comparative toxicokinetic data for these two strains of rabbit would aid in delineating actual differences in exposure to the test compound.
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ACKNOWLEDGMENTS |
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NOTES |
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1 To whom correspondence should be addressed. Fax: 9195416499. E-mail: jdg01{at}rti.org.
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REFERENCES |
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Agresti, A. (1990). Categorical Data Analysis. John Wiley and Sons, NY.
Armitage, P. (1955). Test for linear trends in proportions and frequencies. Biometrics 11, 375386.[ISI]
BASF (1974a). Report of the study of formamide for teratogenic effect in the rat after repeated, workday percutaneous application. Report Number NCI 008271T6, report date: 9/24/1974. Letter from BASF Corporation submitting information (5/27/1992; report in German), NTIS Number: OTS0539634.
BASF (1974b). Report on the examination of formamide and acetamide for teratogenic effect in rats after oral application. Report Number XIX/197, report date: 9/24/1974. Letter from BASF Corporation submitting information (Report in German, 5/27/1992), NTIS Number: OTS0539636.
BASF (1983). Cover letter and English translation of Report on the Examination of Formamide for Teratogenic Effects in Rats After Oral Application. BASF Wyandotte Corp. (1/11/83). NTIS Number: OTS0512663.
Budavari, S., O'Neill, M. J., Smith, A., Heckleman, P. E., and Kinneary, J. F. (1996). The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 12th Edition. Merck, Whitehouse Station, NJ.
Cheng, T. J., Hwang, S. J., Kuo, H. W., Luo, J. C., and Chang, M. J. (1999). Exposure to epichlorohydrin and dimethylformamide, glutathione S-transferases and sister chromatid exchange frequencies in peripheral lymphocytes. Arch. Toxicol. 73, 282287.[ISI][Medline]
Cochran, W. (1954). Some methods for strengthening the common c2 tests. Biometrics 10, 417451.[ISI]
Cody, R. L., Seid, J. E., and Natale, R. B. (1992). Phase-II trial of N-methylformamide in lung cancer. Invest. New Drugs 10, 215216.[ISI][Medline]
Del Bufalo, D., Bucci, B., D'Agnano, I., and Zupi, G. (1994). N-methylformamide as a potential therapeutic approach in colon cancer. Dis. Colon Rectum 37(Suppl. 2), S133137.[ISI][Medline]
Dunnett, C. W. (1955). A multiple comparison procedure for comparing several treatments with a control. J. Am. Stat. Assoc. 50, 10961121.[ISI]
Dunnett, C. W. (1964). New tables for multiple comparisons with a control. Biometrics 20, 482491.[ISI]
Fail, P. A., George, J. D., Grizzle, T. B., and Heindel, J. J. (1998). Formamide and dimethylformamide: reproductive assessment by continuous breeding in mice. Reprod. Toxicol. 12, 317332.[ISI][Medline]
George, J. D., Price, C. J., Marr, M. C., Myers, C. B., and Jahnke, G. D. (2000). Evaluation of the developmental toxicity of formamide in Sprague-Dawley (CD) rats. Toxicol. Sci. 57, 284291.
Gescher, A., Gibson, N. W., Hickman, J. A., Langdon, S. P., Ross, D., and Atassi, G. (1982). N-methylformamide: Antitumour activity and metabolism in mice. Br. J. Cancer 45, 843850.[ISI][Medline]
Gliech, J. (1974). The influence of simple acid amides on fetal development of mice. Arch. Exp. Pathol. Pharmakol. 282(Suppl.), R25.
Hellwig, J., Merkle, J., Klimisch, H. J., and Jäckh, R. (1991). Studies on the prenatal toxicity of N,N-dimethylformamide in mice, rats, and rabbits. Food Chem. Toxicol. 29, 193201.[ISI][Medline]
ITII (1988). Toxic and Hazardous Industrial Chemicals, Safety Manual for Handling and Disposal With Toxicity and Hazard Data. The International Technical Information Institute, revised: Tokyo.
Kelich, S. L., Mercieca, M. D., and Pohland, R. C. (1995). Developmental toxicity of N-methylformamide administered by gavage to CD rats and New Zealand white rabbits. Fundam. Appl. Toxicol. 27, 239246.[ISI][Medline]
Kennedy, G. L., Jr. (2001). Biological effects of acetamide, formamide, and their mono and dimethyl derivatives: An update. Crit. Rev. Toxicol. 31, 139222.[ISI][Medline]
Lareo, A. C., and Perbellini, L. (1995). Biological monitoring of workers exposed to N-N-dimethylformamide: II. Dimethylformamide and its metabolites in urine of exposed workers. Int. Arch. Occup. Environ. Health 67, 4752.[ISI][Medline]
Liu, S. L., Mercieca, M. D., Markham, J. K., Pohland, R. C., and Kenel, M. F. (1989). Developmental toxicity studies with N-methylformamide (NMF) administered orally to rats and rabbits. Teratology 39, 466.
Major, J., Hudak, A., Kiss, G., Jakab, M. G., Szaniszlo, J., Naray, M., Nagy, I., and Tompa, A. (1998). Follow-up biological and genotoxicological monitoring of acrylonitrile- and dimethylformamide-exposed viscose rayon plant workers. Environ. Mol. Mutagen 31, 301310.[ISI][Medline]
Marr, M. C., Myers, C. B., George, J. D., and Price, C. J. (1988). Comparison of single and double staining for evaluation of skeletal development: The effects of ethylene glycol in CD rats. Teratology 37, 476.[ISI]
Merkle, J., and Zeller, H. (1980). [Studies on acetamides and formamides for embryotoxic and teratogenic activities in the rabbit (author's translation)]. Arzneimittelforschung 30, 15571562.[Medline]
Mraz, J., Cross, H., Gescher, A., Threadgill, M. D., and Flek, J. (1989). Differences between rodents and humans in the metabolic toxification of N,N-dimethylformamide. Toxicol. Appl. Pharmacol. 98, 507516.[ISI][Medline]
NIOSH (2000). International Chemical Safety Cards, Formamide. National Institute of Occupational Safety and Health. Available at www.cdc.gov/niosh/ipcsneng/neng0891.html. Accessed May 23, 2000.
NTP (1998a). Developmental toxicity screen for formamide (CAS No. 75127) administered by gavage to Sprague-Dawley (CD®) rats on gestational days 6 through 19. Final Study Report (April 13, 1998). National Toxicology Program, http://www.ntis.gov.
NTP (1998b). Developmental toxicity evaluation of formamide (CAS No. 75127) administered by gavage to Sprague-Dawley (CD®) rats on gestational days 6 through 19. Final Study Report (December 30, 1998) NTIS Number: PB99139701. National Toxicology Program, http://www.ntis.gov.
NTP (1998c). Developmental toxicity screen of formamide (CAS No. 75127) administered by gavage to New Zealand White (NZW) rabbits on gestational days 6 through 29. Final Study Report (November 20, 1998). NTIS Number: PB2001-104060. National Toxicology Program, http://www.ntis.gov.
NTP (2000). Chemical Health and Safety Data. Formamide. National Toxicology Program. Available at http://ntp-server.niehs.nih.gov/. Accessed May 23, 2000.
NTP (2001). Developmental toxicity evaluation of formamide (CAS No. 75127) administered by gavage to New Zealand White rabbits on gestational days 6 through 29. Final Study Report (March 8, 2001). NTIS Number: PB2001104060. National Toxicology Program.
Oettel, H., and Frohberg, H. (1964). Teratogenic action of the elementary acid amides in experiments with animals. Naunyn Schmiedeberg Arch. Exp. Pathol. Pharmakol. 247, 363364.[ISI]
Oettel, H., and Wilhelm, G. (1957). Vergleichende Prufung von 14 Cytostatisch Wirksmen Produkten an 7 Tiertumorem. Naunyn Schmiedeberg Arch. Exp. Pathol. Pharmakol. 230, 559.[ISI][Medline]
Ogata, M., Numano, T., Hosokawa, M., and Michitsuji, H. (1997). Large-scale biological monitoring in Japan. Sci. Total Environ. 199, 197204.[ISI][Medline]
Rickard, L. B., Driscoll, C. D., Kennedy, G. L., Jr., Staples, R. E., and Valentine, R. (1995). Developmental toxicity of inhaled N-methylformamide in the rat. Fundam. Appl. Toxicol. 28, 167176.[ISI][Medline]
Ross, D., Gescher, A., and Hickman, J. A. (1981). Metabolic studies on the antitumor agent N-methylformamide. Br. J. Cancer 44, 278.
Saillenfait, A. M., Payan, J. P., Beydon, D., Fabry, J. P., Langonne, I., Sabate, J. P., and Gallissot, F. (1997). Assessment of the developmental toxicity, metabolism, and placental transfer of N,N-dimethylformamide administered to pregnant rats. Fundam. Appl. Toxicol. 39, 3343.[ISI][Medline]
Salewski, E. (1964). Staining method for a macroscopic test for implantation points in the uterus of the rat. Naunyn Schmiedebergs Arch. Exp. Pathol. Pharmakol. 247, 367.
Sakai, T., Kageyama, H., Araki, T., Yosida, T., Kuribayashi, T., and Masuyama, Y. (1995). Biological monitoring of workers exposed to N,N-dimethylformamide by determination of the urinary metabolites, N-methylformamide and N-acetyl-S-(N-methylcarbamoyl) cysteine. Int. Arch. Occup. Environ Health 67, 125129.[ISI][Medline]
SAS Institute, Inc. (1989a). SAS Language and Procedures: Usage, Ver. 6, 1st ed. SAS Institute, Cary, NC.
SAS Institute, Inc. (1989b). SAS/STAT Users' Guide, Ver. 6, 4th ed., Vol. 1 and 2. SAS Institute, Cary, NC.
SAS Institute, Inc. (1990a). SAS Language: Reference, Ver. 6, 1st ed. SAS Institute, Cary, NC.
SAS Institute, Inc. (1990b). SAS Language: Procedures Guide, Ver. 6, 3rd ed. SAS Institute, Cary, NC.
SAS Institute, Inc. (1990c). SAS Companion for the VMSTM Environment, Ver. 6, 1st ed. SAS Institute, Cary, NC.
SAS Institute, Inc. (1992). SAS Technical Report P-229, SAS/STAT Software: Changes and Enhancements, Release 6.07. SAS Institute, Cary, NC.
SAS Institute, Inc. (1996). SAS Companion for the Microsoft Windows Environment. SAS Institute, Cary, NC.
SAS Institute, Inc. (1997). SAS/STAT Software: Changes and Enhancements Through Release 6.12. SAS Institute, Cary, NC.
Sax, N. I., and Lewis, Sr., R. J. (1987). Hawley's Condensed Chemical Dictionary, 11th ed. Van Nostrand, Reinhold, NY.
Snedecor, G. W., and Cochran, W. G. (1967). Statistical Methods, 6th ed. Iowa State University Press, Ames, IA.
Staples, R. E. (1974). Detection of visceral alterations in mammalian fetuses. Teratology 9, 3738A.
Stuckhardt, J. L., and Poppe, S. M. (1984). Fresh visceral examination of rat and rabbit fetuses used in teratogenicity testing. Teratogen. Carcinogen. Mutagen. 4, 181188.[ISI][Medline]
Stula, E. F. et al. (1992). Embryotoxicity in Rats and Rabbits from Application of Formamide and Other Chemicals to Skin during Organogenesis. Haskell Laboratory for Toxicology and Industrial Medicine, E. I. DuPont de Nemours and Company, Wilmington, DE (NTIS Number OTS0571481 TSCA, Section 8ECF).
Thiersch, J. B. (1962). Effects of acetamides and formamides on the rat litter in vitro. J. Reprod. Fertil. 4, 219220.[ISI]
Thiersch, J. B. (1971). Investigations into the differential effect of compounds on rat litter and mother. In Congenital Malformations of Mammals (Name?, Ed.), p. 113. Masson, Paris.
U.S. EPA (1997). Prenatal Developmental Toxicity. Toxic Substances Control Act Test Guidelines; Final Rule. Part III, 40 CFR Part 799. August 15, 1997. U.S. Environmental Protection Agency. Fed. Regist. 62, 4383243834.
U.S. EPA (1998). Pesticides and Toxic Substances. U.S. Environmental Protection Agency, Office of Prevention, Health Effects Test Guidelines, OPPTS 870.3700, Prenatal Developmental Toxicity Study. EPA 712-C-98207.
U.S. FDA (1994a). Good Laboratory Practice Regulations for Nonclinical Laboratory Studies. U.S. Food and Drug Administration. Code of Federal Regulations (CFR) (March 21) 56FR12300.
U.S. FDA (1994b). International Conference on Harmonization; Guideline on Detection of Toxicity to Reproduction for Medicinal Products. U.S. Food and Drug Administration. Fed. Regist. 59, 4874648752.
West, S. D., and Turner, L. G. (1988). Residue level determination of the aquatic herbicide fluridone and a potential photoproduct (N-methylformamide) in water. J. Assoc. Off. Anal. Chem. 71, 10491053.[ISI][Medline]
Wilson, J. G. (1965). Embryological considerations in teratology. In Teratology: Principles and Techniques (J. G. Wilson and J. Warkany, Eds.), pp. 251277. University of Chicago Press, Chicago.