Developmental toxicity evaluation of ethylene glycol by gavage in New Zealand white rabbits

Artificially inseminated New Zealand white (NZW) rabbits were administered ethylene glycol (EG) by gavage on Gestational Days (GD) 6 through 19 at doses of 0, 100, 500, 1000, or 2000 mg/kg/day, with 23-24 inseminated animals per group. Clinical signs were recorded and water consumption was measured daily; does were weighed on GD 0, 6-19, 25, and 30. At necropsy (GD 30), maternal liver, kidney, and gravid uterine weights were recorded. Histopathologic examination was performed on kidneys from 10 does/dose and for all unscheduled deaths. Ovarian corpora lutea were counted and uterine implantation sites (total sites, resorptions, dead and live fetuses) were recorded. All live fetuses were weighed, sexed, and examined for external, visceral, and skeletal malformations and variations. EG resulted in profound maternal toxicity at 2000 mg/kg/day (42% mortality; three early deliveries and one spontaneous abortion) associated with renal pathology and unaccompanied by any other indicators of maternal toxicity. Renal lesions at 2000 mg/kg/day involved the cortical renal tubules and included intraluminal oxalate crystals, epithelial necrosis, and tubular dilatation and degeneration. No dose-related maternal toxicity occurred at 100-1000 mg/kg/day. There was no indication of developmental toxicity at any dose tested, including no effects on pre- or postimplantation loss, number of fetuses, fetal body weight, or sex ratio (% male fetuses) per litter, and no evidence of teratogenicity. The "no observable adverse effect level" (NOAEL) for maternal toxicity was therefore 1000 mg/kg/day and the NOAEL for developmental toxicity was at least 2000 mg/kg/day in this study. The sensitivity of NZW rabbits relative to that of Sprague-Dawley rats and Swiss mice for maternal and developmental toxicity from gavage administration of EG during organogenesis can be determined for maternal toxicity: rabbits > mice > rats, and for developmental toxicity, mice > rats > rabbits.     

Developmental toxicity evaluation of isopropanol by gavage in rats and rabbits

Timed-pregnant CD (Sprague-Dawley) rats, 25/group, were dosed orally with aqueous isopropanol (IPA; CAS No. 67-63-0) solutions at 0, 400, 800, or 1200 mg/kg/day, once daily on Gestational Days (GD) 6 through 15 at a dosing volume of 5 ml/kg. Artificially inseminated New Zealand white rabbits, 15/group, were dosed orally with IPA at 0, 120, 240, or 480 mg/kg/day once daily on GD 6 through 18 at 2 ml/kg. Maternal body weights, clinical observations, and food consumption were recorded throughout gestation for both species. At scheduled euthanization for both species (GD 20, rats; GD 30, rabbits), fetuses were weighed, sexed, and examined for external, visceral (including craniofacial) and skeletal alterations. For both species, the pregnancy rate was high and equivalent across all groups; no dams or does aborted, delivered early, or were removed from study. In rats, two dams (8%) died at 1200 mg/kg/day and one dam (4%) died at 800 mg/kg/day. Maternal body weights and weight gain were equivalent across all groups, except for statistically significantly reduced gestational weight gain (GD 0-20; 89.9% of control value), associated with statistically significantly reduced gravid uterine weight at 1200 mg/kg/day (89.2% of control value). There were no treatment-related clinical signs or effects on maternal food consumption. All gestational parameters evaluated were equivalent across groups, including pre- and postimplantation loss, fetal sex ratios, and litter size. Twenty-two to 25 litters were examined per group. Fetal body weights per litter were statistically significantly reduced at the two highest doses (97.3 (n.s.), 94.7, and 94.3% of controls at 800 mg/kg/day and 92.1, 91.9, and 95.4% of controls at 1200 mg/kg/day for all fetuses and males and females separately). No evidence of increased teratogenicity was observed at any dose tested in rats. In rabbits, four does (26.7%) died at 480 mg/kg/day. Maternal body weights were statistically significantly reduced during treatment (GD 6-18) at 480 mg/kg/day (45.4% of control value) with a nonsignificant reduction in gestational weight change (GD 0-30; 77.3% of control value) at this dose. Profound clinical signs of toxicity and statistically significantly reduced maternal food consumption were observed at 480 mg/kg/day. All gestational parameters were equivalent across all doses administered. Thirteen to 15 litters were evaluated per group except for the 480 mg/kg/day group with 11 litters (due to maternal deaths). There were no treatment-related effects on pre- or postimplantation loss, fetal sex ratio, litter size, or fetal body weight/litter. Moreover, no evidence was found of increased teratogenicity at any dose tested in rabbits. Therefore, IPA was not teratogenic to CD rats or to NZW rabbits. The NOAELS for both maternal and developmental toxicity were 400 mg/kg/day in rats, and were 240 and 480 mg/kg/day, respectively, in rabbits.     

Effectiveness of continuous intravenous prostaglandin E 1 against pulmonary hypertension]

Teratogenicity studies of methyl bromide, a widely used fumigant, were conducted in rats and rabbits. Methyl bromide was dissolved in corn oil and administered orally to groups of 24 copulated female Crj:CD (SD) rats at dose levels of 0 (corn oil), 3, 10 or 30 mg/kg/day on days 6-15 of gestation and to groups of 18 artificially inseminated female Kbl:JW rabbits at 0, 1, 3 or 10 mg/kg/day on days 6-18 of gestation. Maternal rats and rabbits were euthanized on respective days 20 and 27 of gestation. Foetuses were examined for survival, growth and teratological alterations. Maternal toxicity was evident in the high-dose groups for both species. In these groups, maternal body weight gains and food consumption were significantly decreased during the dosing and post-dosing periods. Necropsy of maternal rats also revealed erosive lesions in the stomach and the surrounding organs. However, no treatment-related adverse effects were found in foetuses of the treated groups for both rat and rabbit studies. These results led to the conclusion that methyl bromide was not foetotoxic or teratogenic to rat and rabbit foetuses up to dose levels of 30 and 10 mg/kg/day, respectively, at which maternal toxicity was evident for both species.     

An update on the clinical use of methadone for cancer pain

The objective of this study was to evaluate the developmental toxicity of phthalic acid (PA), which is one of the metabolites of phthalic acid esters (PAEs). Pregnant rats were given PA at a dose of 0 (control), 1.25, 2.5, or 5.0% in the diet on day 7 through day 16 of pregnancy. Average daily intakes of PA were 1021 mg/kg for the 1.25% group, 1763 mg/kg for the 2.5% group, and 2981 mg/kg for the 5.0% group. Maternal toxicity occurred in the 2.5 and 5.0% groups as can be seen by significant decreases in the maternal body weight gain and food consumption during the administration period. No significant changes in maternal parameters were found in the 1.25% group. Neither deaths nor clinical signs of toxicity were noted in any groups. No significant changes induced by PA were detected in the incidence of postimplantation loss and number and sex ratio of live fetuses. Significant decreases in the weight of male fetuses and number of ossification center of the caudal vertebrae were found in the 5.0% group. Morphological examinations of fetuses revealed no evidence of teratogenesis. Thus it appears unlikely that PA may be responsible for the production of the developmental toxicity of PAEs.     

Neurochemical and neurobehavioral effects of repeated gestational exposure to chlorpyrifos in maternal and developing rats

Acute exposure to the organophosphate pesticide chlorpyrifos (CPF) on gestation day 12 (GD12, 200 mg/kg/ml, SC) causes extensive neurochemical changes in maternal brain but lesser changes in fetal brain. In the present study, we examined the relative neurotoxicity of repeated, lower-level CPF exposures during gestation in rats. Pregnant Sprague-Dawley rats were exposed to CPF (6.25, 12.5, or 25 mg/kg per day, SC) from GD12-19 and sampled at either GD16, GD20, or postnatal day 3 (PND3) for measurement of various maternal and developmental neurochemical markers. In contrast to the high acute dose exposure, no maternal toxicity was noted with repeated lower-level dosing. Extensive acetylcholinesterase (AChE) inhibition (83-90%) was noted in maternal brain at all three time points following repeated exposures (25 mg/kg). Higher AChE inhibition (58%) was noted in fetal brain at GD20 compared to 19-25% on PND3 in treated pups cross-fostered to control dams and in control pups cross-fostered to treated dams following repeated exposures (25 mg/kg per day). Whereas similar reductions in brain muscarinic receptor binding were noted at GD20 and PND3 in dams and developing brain between acute and repeated dosing regimens, greater changes in [3H]CD and [3H]cytisine binding were evident following repeated exposures. Righting reflex and cliff avoidance tests were markedly altered following repeated exposures. The results suggest that lower-level repeated exposures to CPF cause extensive neurochemical and neurobehavioral changes in developing rats in the absence of maternal toxicity.     

Gap-junction disassembly and connexin 43 dephosphorylation induced by 18 beta-glycyrrhetinic acid

In two Segment II Teratology studies, timed-pregnant Crl:CD[BR] (Sprague-Dawley) rats were treated orally (gastric intubation) on days 6-15 of gestation with ibutilide fumarate (ibutilide), a class III antiarrhythmic that has been shown to increase the refractory period and action potential duration of myocardial cells. In the first study, ibutilide does of 20, 40, and 80 mg/kg/ day were tested. Although maternal toxicity was equivocal in the 80 mg/kg/day group, all 23 rats that conceived had entirely resorbed liters when the animals were killed on day 20 of gestation. Similarly, 12 of 24 litters were completely resorbed in the 40 mg/kg/day group, with an 87.7% postimplantational loss. Of the surviving fetuses in this group, 48.6% had at least one malformation. The incidences of malformed pharynx and malformed palate, along with adactyly, were statistically significantly higher in this group than in the control group. In addition, a significant (P < 0.05) increase in total malformations (5.7% of the fetuses), relative to the controls (0.8%), was found for the 20 mg/kg/day group. Since a no observed adverse effect level (NOAEL) was not found, a second teratology study was performed. In this study, the ibutilide doses were 5, 10, and 20 mg/kg/day. The 20 mg/kg/day dose was again teratogenic with 9.2% of the fetuses malformed, as compared to a control value of 1.0%. Also, the incidences of scoliosis and interventricular septal defect were statistically significantly higher in this group. Although statistically significant differences were not detected, scoliosis was also found in the 10 mg/kg/day group (3 fetuses in 2 litters), along with a significant dose-response trend for this malformation. As the result, the NOAEL for ibutilide teratogenicity in rats was set at 5 mg/kg/day. This dose is 4 times the proposed maximum clinical dose (two 1 mg doses, each infused over 10 minutes, or 0.033 mg/kg for a 60 kg person), when corrected for 2.6% oral bioavailability in the rat at a dose of 10 mg/kg, as determined in separate studies.     

Study of the effects of beta-myrcene on rat fertility and general reproductive performance

beta-Myrcene (MYR) is a monoterpene found in the oils of a variety of aromatic plants including lemongrass, verbena, hop, bay, and others. MYR and essential oils containing this terpenoid compound are used in cosmetics, household products, and as flavoring food additives. This study was undertaken on investigate the effects of MYR on fertility and general reproductive performance in the rat. MYR (0, 100, 300 and 500 mg/kg) in peanut oil was given by gavage to male Wistar rats (15 per dose group) for 91 days prior to mating and during the mating period, as well as to females (45 per dose group) continuously for 21 days before mating, during mating and pregnancy, and throughout the period of lactation up to postnatal day 21. On day 21 of pregnancy one-third of the females of each group were submitted to cesarean section. Resorption, implantation, as well as dead and live fetuses were counted. All fetuses were examined for external malformations, weighed, and cleared and stained with Alizarin Red S for skeleton evaluation. The remaining dams were allowed to give birth to their offspring. The progeny was examined at birth and subsequently up to postnatal day 21. Mortality, weight gain and physical signs of postnatal development were evaluated. Except for an increase in liver and kidney weights, no other sign of toxicity was noted in male and female rats exposed to MYR. MYR did not affect the mating index (proportion of females impregnated by males) or the pregnancy index (ratio of pregnant to sperm-positive females). No sign of maternal toxicity and no increase in externally visible malformations were observed at any dose level. Only at the highest dose tested (500 mg/kg) did MYR induce an increase in the resorption rate and a higher frequency of fetal skeleton anomalies. No adverse effect of MYR on postnatal weight gain was noted but days of appearance of primary coat, incisor eruption and eye opening were slightly delayed in the exposed offspring. On the basis of the data presented in this paper the no-observed-adverse-effect level (NOAEL) for toxic effects on fertility and general reproductive performance can be set at 300 mg of beta-myrcene/kg body weight by the oral route.     

Protective effect of liposome encapsulation on paclitaxel developmental toxicity in the rat

Paclitaxel is an anticancer drug that has demonstrated severe embryotoxicity in chicks. This embryotoxicity is reduced by liposome encapsulation of the drug. The current study was designed to evaluate the potential of liposome encapsulation for reducing paclitaxel embryotoxicity in rats. Wistar rats were treated with paclitaxel on day 8 of pregnancy (plug = day 0) at doses of 0.67, 2.0, or 10.0 mg/kg intravenously. The same doses of paclitaxel encapsulated in liposomes were administered intravenously to other groups of animals. Control animals were given blank liposomes. Free paclitaxel produced maternal and embryotoxicity at 10.0 mg/kg with three of seven dams dying and resorption of all embryos in surviving dams. Liposome encapsulation at 10.0 mg/kg was not associated with maternal death and there were live fetuses on evaluation at term, although litter size was reduced and malformations occurred in surviving fetuses. At 2.0 mg/kg free paclitaxel, fetal weight was decreased and resorptions increased. Liposome encapsulation at 2.0 mg/kg produced litter results similar to those obtained in control animals given empty liposomes. Malformations were prominent at 2.0 mg/kg free paclitaxel and at 10.0 mg/kg paclitaxel in liposomes and included exencephaly/anencephaly, ventral wall defects, facial clefts, anophthalmia, diaphragmatic hernia, and defects of the kidney, cardiovascular system, and tail. Liposome encapsulation appeared to shift the developmental response to paclitaxel such that 10 mg/kg encapsulated drug produced effects similar to 2.0 mg/kg free drug. These results may have implications for drug delivery of therapeutic agents used during human pregnancy.     

Developmental toxicity of clarified slurry oil, syntower bottoms, and distillate aromatic extract administered as a single oral dose to pregnant rats

Clarified slurry oil (CSO), syntower bottoms (STB), and distillate aromatic extract (DAE) are refinery streams produced by processing crude oil. Each of these refinery streams is rich in both hydrocarbons having carbon numbers of C20 or greater and polycyclic aromatic compounds. Available data indicate that some refinery streams are developmentally toxic (manifested primarily as increased embryolethality and growth retardation) by the dermal route of exposure. However, there is no conclusive evidence for their being teratogenic. The present studies were designed to further explore the suspected teratogenic potency of refinery streams while at the same time limiting embryolethality. To profile teratogenic effects as a function of gestation day, pregnant rats received a single oral dose (2000 mg/kg) of CSO, STB, or DAE on one of gestation days (GD) 11-14; DAE and STB were also administered on GD 15. To profile effects as a dose response function, rats received a single oral dose of CSO, DAE, or STB on GD 12 at 125, 500, and 2000 mg/kg. Control animals were similarly treated but were administered tap water. On GD 20, dams were necropsied and the fetuses evaluated for normal development. In general, evidence of maternal toxicity (i.e., decreased body weight gain, decreased thymus weight) was observed at doses greater than or equal to 500 mg/kg. For each refinery stream tested, the incidence of resorption was greatest on GD 11. A common pattern of fetal malformations was observed for all of the refinery streams tested and included cleft palate, diaphragmatic hernia, and paw and tail defects. The incidence and type of malformation observed were influenced by the gestation day of exposure. The incidences of external and skeletal malformations were greatest on GD 11 and 12 for fetuses exposed to CSO; on GD 13 and 14, the incidence of malformation was comparable for CSO- and STB-exposed fetuses. The incidence of visceral anomalies was greatest on GD 11-13 for fetuses exposed to CSO and STB; on Gestation D 14, the incidence was comparable for each of the refinery streams tested. In general, the ability to produce adverse effects on development was greatest for CSO and least for DAE. Effects produced by STB were comparable to or less severe than those observed for CSO.     

Developmental toxicity of fleroxacin and comparative pharmacokinetics of four fluoroquinolones in the cynomolgus macaque (Macaca fascicularis)

The potential developmental toxicity of fleroxacin was studied (Phase I) and its pharmacokinetics was compared to ciprofloxacin, temafloxacin, and norfloxacin (Phase II) in the cynomolgus macaque (Macaca fascicularis). Phase I studies involved oral administration of fleroxacin (35 and 70 mg/kg-day) during Gestational Days (GD) 20-34 or 35-49 (N = 10/group); controls received vehicle only. Increased maternal toxicity (weight loss, anorexia, emesis) and embryolethality (4/10, 40%; GD 20-34) were observed at 70 mg/kg-day. Urinary excretion of estrogen conjugates was reduced for females with nonviable pregnancies during both treatment periods (GD 20-34 and 35-49), although steroid hormone levels in serum remained unchanged during treatment; no malformations or growth retardation were observed at gross examination. For Phase II studies, the pharmacokinetics of fleroxacin (70 mg/kg), ciprofloxacin (100 mg/kg), temafloxacin (100 mg/kg), and norfloxacin (150 mg/kg) were studied during a 3-day oral treatment regimen in the nonpregnant (N = 12; 3/quinolone) and pregnant (N = 3; fleroxacin only) macaque. Serial blood samples were collected on the first and third days of treatment in all animals; for pregnant females, the conceptus was removed on GD 31 for analysis of fleroxacin levels. Marked differences between the quinolones were noted in the AUC0-24 hr for nonpregnant females. Based on AUC0-24 hr on the first day of treatment, the rank order was fleroxacin > temafloxacin > ciprofloxacin > norfloxacin. On the third of treatment, the rank order for exposure was temafloxacin > fleroxacin > ciprofloxacin > norfloxacin. Overall, results indicated (1) no marked differences in pharmacokinetic parameters in pregnant versus nonpregnant females, (2) fleroxacin levels in embryonic tissues were similar to maternal plasma levels, and (3) there was a correlation between exposure and embryolethal doses for all fluoroquinolones which resulted in embryolethality except norfloxacin.     

Importance of metabolism in pharmacological studies: possible in vitro predictability

Groups of 20 male and 20 female Sprague-Dawley rats were administered undiluted Aquacoat ECD ethylcellulose aqueous dispersion by oral gavage at doses of 903, 2709 or 4515 mg/kg body weight/day (dry weight basis) for 90 days. Control animals received water at the same dosage volume as the high-dose group. Body weights and food consumption were recorded weekly. Blood was collected prior to study termination for haematology and clinical chemistry measurements. Survivors underwent complete necropsies on days 91 94. Selected organs were weighed and histologically examined. The only treatment-related clinical sign observed was pale faeces which was noted among males and females receiving 2709 and 4515 mg/kg/day Aquacoat ECD. No statistically significant differences in body weights, body weight gains, food consumption and organ weights were noted among males and females when compared with controls. No treatment-related effects in haematology parameters were noted. Significantly decreased total protein and globulin levels and increases in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in male rats receiving 2709 and 4515 mg Aquacoat ECD/kg/day were considered to be treatment related. No gross or microscopic lesions were attributed to Aquacoat ECD treatment. Under the conditions of this study, the no-observed-adverse-effect level (NOAEL) for female rats is in excess of 4515 mg/kg/day: the NOAEL for male rats is 903 mg/kg/day.     

Study on the developmental toxicity of orally administered isobutylidenediurea in rats

Developmental toxicity of isobutylidenediurea (IBDU) was determined by oral administration to Wistar rats. The substance was administered as an aqueous suspension to 22-24 pregnant rats per group by gavage in daily doses of 100, 400 and 1000 mg/kg body weight from day 6 post-coitum (p.c.) to day 15 p.c. The control group received the vehicle only (0.5% aqueous carboxymethyl cellulose solution). There were no substance-related effects in the dams concerning food consumption, body weight, body weight gain, uterine weights and clinical or autopsy observations even at the highest dose of 1000 mg/kg body weight/day. The reproduction data revealed no biologically relevant differences between the control and treated groups. The incidence and type of the foetal external, soft tissue and skeletal findings, which were classified as malformations, variations and/or retardations observed in the treated foetuses were similar to the concurrent and/or historical control data. Thus, under the conditions of this study, no signs of maternal toxicity or embryo/foetotoxicity were induced by IBDU and the no-observable-adverse-effect level on the maternal and developing organism was 1000 mg/kg body weight/day.     

Safety evaluation of amino peptidase enzyme preparation derived from Aspergillus niger

An amino peptidase enzyme preparation obtained from Aspergillus niger was subjected to a series of toxicological tests to document the safety for use as a processing aid for food. The enzyme preparation was examined for subacute and subchronic oral toxicity, and mutagenic potential. No evidence of oral toxicity or mutagenicity was found. Administration of the amino peptidase enzyme preparation at doses of 500, 1000 and 2000 mg/kg body weight/day for 90 days did not induce noticeable signs of toxicity. The no-observed-adverse-effect level (NOAEL) of the enzyme preparation in the subchronic toxicity study was 2000mg/kg body weight/day (equivalent to 1152 PHEA units/kg body weight/day). It can be concluded that no safety concerns were identified in the studies conducted with this amino peptidase enzyme preparation derived from Aspergillus niger and produced under controlled fermentation conditions.     

Bacterial endosymbiont-derived lipopolysaccharides and a protein on symbiosome membranes in newly infected amoebae and their roles in lysosome-symbiosome fusion

L-691,121 is a class III antiarrhythmic agent which blocks potassium currents, leading to prolongation of cardiac potential and prevention of cardiac arrhythmia. In a developmental toxicity study in rats, there was a dose-dependent decrease in embryonic/fetal survival, and death of the entire litter was seen at an oral dose of 0.8 mg/kg per day. The critical period for embryolethality was determined as gestational days (GD) 10-13. In a study where females received 1 mg/kg on a critical day (GD 10 or 12) and were killed at 24-h intervals, a high embryonic mortality was seen at 72 h (GD 10 treatment) or 48 h (GD 12 treatment) after dosing. The surviving embryos had morphological abnormalities such as enlarged cardiac tube and pericardium, generalized edema, and hematoma. In order to investigate a possible mechanism for the embryolethality, GD 11 embryos were dissected from females at 4 h after dosing of 1 mg/kg and incubated for 5 h in vitro. The embryonic heart rates were decreased for the first 2 h after incubation but tended to recover to control levels thereafter. When GD 11 embryos were incubated for 4 h with the drug, there were decreases in the heart rates during the entire observation period. In a washout study where the embryos were transferred to drug-free medium after 1-h exposure, decreased heart rates recovered to control levels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Safety evaluation of perfluoropolyethers, liquid polymers used in barrier creams and other skin-care products

Fomblin HC products are a 'family' of high-purity perfluoropolyethers manufactured for barrier cream and other personal care applications which involve direct application to the skin. To confirm the safety of such use, representative Fomblin HC products were tested in experimental animals for acute toxicity, primary and repeated insult irritancy, sensitization and photosensitization, subacute oral toxicity and comedogenicity; mutagenicity was examined in vitro, and irritancy or sensitization was also investigated on human skin (in patch tests with volunteers). A high molecular weight Fomblin HC only was tested in rats for subacute oral toxicity and in man for dermal effects. Single oral doses of 15 g/kg body weight were without evident toxicity to rats, as were single dermal applications or an ip injection at 5 g/kg. No primary irritant action was seen in rabbits or man, and similarly there was no evidence of skin sensitization or photosensitization in guinea pigs, or sensitization in man. No mutagenic action on Salmonella strains of tester bacteria was seen. In repeat dose irritancy or oral toxicity tests in rabbits or rats, no adverse effects of Fomblin HC products were noted; in particular, daily oral administration (1000 mg/kg/day) to rats over 28 days produced no significant reaction. No comedogenic action was found. From the known chemistry of the perfluoropolyethers, the test programme reported here and the limited published data, it is concluded that the intended use of Fomblin HC products in formulations applied to human skin has a high margin of safety.     

Repeated administration of alpha-hederin results in alterations in maternal zinc status and adverse developmental outcome in the rat

The administration of alpha-hederin, an inducer of metallothionein, results in a secondary zinc deficiency that may be an important maternally mediated mechanism of developmental toxicity. Previous studies have shown adverse developmental outcome with a single administration of alpha-hederin to rats on gestation day (GD) 8 or 11. The objective of this study was to determine whether dosing of alpha-hederin throughout organogenesis would result in a sustained elevation of maternal hepatic metallothionein and subsequent developmental abnormalities. Rats were administered dosage levels of 0 (vehicle only), 20, or 30 mumol/kg from GD 6-15. Maternal hepatic metallothionein levels were 10-fold higher on GD 16 in the treatment groups than the controls. Consequently, liver zinc concentrations increased 60% and 54%, whereas plasma levels decreased 23% and 33% in the 20 and 30 mumol/kg treatment groups, respectively. At GD 20, mean fetal weights of the treatment litters were 11% less than control litters. The administration of alpha-hederin resulted in a threefold increase in the number of offspring that exhibited developmental abnormalities, including visceral and skeletal malformations. Following an oral pulse of 65Zn subsequent to treatment with 0 or 20 mumol/kg of alpha-hederin, the distribution of 65Zn to the liver of treated dams was twice that of controls, whereas the radiolabeled zinc apportioned to the decidua and uterus decreased by 44%. Furthermore, the 65Zn detected in the embryos from treated dams was 70% lower than in embryos from control dams. In conclusion, low doses of a metallothionein inducer administered to the dam from GD 6-15 resulted in a sustained elevation of hepatic metallothionein and a subsequent redistribution of zinc leading to a decrease in the zinc available to the embryo and ultimately to adverse development of the offspring. Repeated dosing throughout organogenesis, as required in regulated safety assessment testing, increased the severity of the effects previously observed with single large dosages of the toxicant administered during midgestation.     

Effect of chronic maternal methadone exposure on perinatal development

The effect of perinatal exposure to methadone on body growth and brain development was studied in rat. Female Sprague-Dawley albino rats received daily intraperitoneal injections of 5 mg/kg dl-methadone-HCl during gestation and lactation. Body weights were reduced in drug-treated mothers during gestation and the first 2 weeks of lactation. No differences in gestation time, litter size, or infant mortality were recorded, however methadone-treated offspring grew more slowly than controls. Weight deficits persisted in rats observed 5-1/2 weeks after cessationof drug exposure (group 1) and in animals continuing to receive daily interperitoneal injections of 5 mg/kg (group 2). From birth to day 21, brain weight and length, cerebral width and cerebellar weight and width were generally smaller in methadone-exposed rats. Brain measurements of group 1 and group 2 animals on day 60 revealed a reduction in brain and cerebellar weights and cerebral and cerebellar widths from control values. Brain:body weight and cerebellum:brain weight ratios were similar to controls. Analysis of these results indicates that maternal methadone treatment retards the growth of young rats and affects brain development.     

Identification of a gene essential for O-acetylation of the Staphylococcus aureus type 5 capsular polysaccharide

It has been hypothesized that the developmental toxicity of certain compounds is, in part, due to maternal toxicity resulting in alterations in zinc (Zn) metabolism that affects the developing conceptus. In the present work the effects of developmentally toxic doses of 2-ethylhexanoic acid (EHXA), 2-ethylhexanol (EHXO), and valproic acid (VPA) on Zn metabolism were investigated in the pregnant rat. In experiment 1, dams were intubated with EHXA (3.13, 6.25, 9.38 or 12.5 mmol/kg), EHXO (6.25, 9.38 or 12.5 mmol/kg), VPA (1.56, 3.13, 6.25 or 9.38 mmol/kg), or corn oil (control; 1.0 ml/kg) at 14:00 h on gestation day (GD) 11.5, intubated with 32 microCi 65Zn at 22:00 h, and then killed at 08:00 h on GD 12.5. At the higher dose levels of EHXA and EHXO, and at all dosages of VPA, the percentage of 65Zn retained in maternal liver was higher, while that in the embryos was lower, than in controls. Chemical-associated changes in 65Zn distribution were associated with increased maternal liver metallothionein (MT) concentrations. In experiment 2, dams were fed diets containing 1, 25 or 97 microg Zn/g from GD 0-16 and intubated with 3.5 mmol EHXA or 1.0 ml corn oil/kg/d from GD 8-15. Dams were killed on GD 16 or 19. High incidences of encephalocele and tail defects were noted in the GD 16 fetuses of EHXA-treated dams fed either the low or adequate Zn diet, the highest incidences being in the low Zn group. On GD 19 the incidence of tail defects tended to be higher in the EHXA groups than in oil-treated controls, the highest incidence occurring in the low Zn EHXA group. Encephalocele was only observed in the low Zn EHXA-treated group. Fetal weight and crown-rump lengths were decreased by EHXA treatment and low dietary Zn. The incidence of rib anomalies was higher in the EHXA-exposed groups than in their respective oil controls. In experiment 3, GD 10.5 embryos collected from control dams were cultured for 48 h in serum from control or EHXA-treated male rats fed 4.5 or 25.0 microg Zn/g diets. Embryos cultured in either EHXA or low Zn sera exhibited delayed development; the addition of Zn to these sera eliminated their developmental toxicity. These results support the hypothesis that certain chemicals which induce maternal toxicity act, in part, to influence embryonic Zn metabolism and trigger abnormal development. Importantly, the teratogenic effects of these chemicals can be modulated by dietary Zn intake.     

Developmental toxicity of cysteamine in the rat: effects on embryo-fetal development

The reproductive and developmental safety of cysteamine has become an important issue to children with cystinosis because renal transplants and treatment with cysteamine reduce the complications associated with cystinosis and increase the lifespan of the affected children. In addition, there is the potential to decrease the severity or the incidence of renal Fanconi syndrome with administration of cysteamine to pregnant women carrying fetuses with cystinosis, and to ease significantly the burden of this disease throughout their lives. If cysteamine increases significantly the risk of fetal death, growth retardation or birth defects at doses used to treat women with cystinosis, treatment of the affected female should cease during pregnancy and would not be considered for fetal treatment. The goal of this study was to assess the developmental safety of exposure in utero to cysteamine in the rat. Pregnant rats were given cysteamine (as phosphocysteamine) from day 6.5 through day 18.5 postconception and fetuses were assessed for survival, growth, and structural abnormalities on day 20.5. Cysteamine was administered orally in doses of 0, 37.5, 75, 100, or 150 mg/kg/day. Cysteamine produced dose-dependent developmental toxicity with an apparent no adverse effect observed level of 75 mg/kg/day. Specific malformations were associated with this effect (cleft palate, kyphosis), as well as intrauterine growth retardation and fetal death at 100-150 mg/kg/day, without signs of maternal toxicity. Investigations continue into the mechanism for the developmental toxicity of cysteamine.