The developmental pathology of maternally derived Thp fetuses

The Thair pin (Thp) mutation is a deletion of 5 centimorgans of chromosome 17 in the mouse. When the mutant chromosome is passed to the fetus through the female, the heterozygous fetuses (Thp/+) die in utero. If the chromosome is passed through the male, the heterozygotes are viable and display a short-tailed phenotype. These maternally derived mutant embryos provide an excellent model system to study the effects of an incomplete female genome on development. The results reported here describe the findings of a pathological study of the affected fetuses from day 14 of development to birth. These observations indicate that the maternally derived Thp fetuses die in utero of congestive heart failure. The mutant fetuses displayed an enlarged heart, primarily the right side, and other cardiovascular abnormalities including ventricular septal defects, aortic stenosis, pulmonary artery dilation, and dilation of the venous circulatory system. The fetuses also displayed abnormal accumulation of extrafetal fluid in the visceral yolk sac and amion, as well as massive subcutaneous edema and ascites. The Thp fetuses were often pale and anemic, and they showed a decreased number of red blood cells per unit volume of blood and an increase in circulating nucleated red blood cells. Defects in the development of the labyrinthine and spongiotrophoblast regions of the placenta were also observed. The pathogenesis of the defects is discussed.     

Evaluation of heart malformations in B6C3F1 mouse fetuses induced by in utero exposure to methyl chloride

C57BL/6 female mice impregnated by C3H males mice to produce B6C3F1 fetuses were exposed daily for six hr to atmospheres containing 0, 250, 500, or 750 ppm methyl chloride, from gestation day 6 to gestation day 18. There were 74 to 77 females with copulation plugs per exposure concentration. Females exposed to 750 ppm ethyl chloride exhibited ataxia commencing on the seventh day of exposure (gestation day 12). They also showed hypersensitivity to touch or sound, tremors and convulsions. Six females in the 750 ppm group died and one was euthanized in extremis prior to scheduled sacrifice. On gestation day 18, all other females were euthanized for evaluation. Only dams exposed to 750 ppm exhibited significant decrease in body weight by gestation day 18, weight gain during the gestation period, and absolute weight gain (weight gain minus gravid uterine weight) versus controls. There were no treatment related-effects on these parameters in the other exposure groups. None of the groups exhibited exposure-related differences in pregnancy rate, gravid uterine weight, or maternal liver weight. There were no differences in the numbers of implantations, resorption, dead fetuses, nonlive (dead plus resorbed) fetuses, live fetuses, sex-ratio, or mean fetal body weight per litter. There was a significant exposure-related increase in the number and percentage of affected (nonlive plus malformed) fetuses per litter with the incidence of affected fetuses in the 750 ppm group significantly higher than controls. There was a statistically significant increase in the incidence of heart defects in the 500 and 750 ppm group relative to controls. Of the 37 fetuses in the study with heart defects, 23 were females, 14 were males. The heart defects observed included: absent or abnormal tricuspid valve, reduced number of papillary muscles and/or chordae tendineae on the right side, small right ventricle, globular heart, and white spots in the left ventricular wall. Multiple malformations were observed in one fetus from the 500 ppm group and in three fetuses in the 750 ppm group. It is concluded that methyl chloride inhalation exposure to pregnant C57BL/6 mice from gestation day 6 through gestation day 17 resulted in maternal toxicity only at the 750 ppm exposure concentration and was teratogenic to B6C3F1 conceptuses at exposure concentrations of 750 and 500 ppm, leading to fetal heart malformations. No evidence of embryo or fetotoxicity other than teratogenicity was seen at any of the exposure concentrations employed. No maternal, embryo or fetotoxicity or teratogenicity was associated with exposure of mice, during critical periods of embryo and fetal development, to 250 ppm of methyl chloride.     

Male disadvantage? Fetal sex and cardiovascular responses to asphyxia in preterm fetal sheep

Clinically and experimentally male fetuses are at significantly greater risk of dying or suffering injury at birth, particularly after premature delivery. We undertook a retrospective cohort analysis of 60 female and 65 male singleton preterm fetal sheep (103-104 days, 0.7 gestation) with mean arterial blood pressure (MAP), heart rate, and carotid and femoral blood flow recordings during 25 min of umbilical cord occlusion in utero. Occlusions were stopped early if fetal MAP fell below 8 mmHg or if there was asystole for >20 s. Fetuses that were able to complete the full 25-min period of occlusion showed no differences between sexes for any cardiovascular responses. Similar numbers of occlusions were stopped early in males (mean: 21 min, n = 16) and females (mean: 23 min, n = 16); however, they showed different responses. Short-occlusion males (n = 16) showed a slower initial fall in femoral vascular conductance, followed by greater bradycardia, hypotension, and associated organ hypoperfusion compared with full-occlusion fetuses. In contrast, short-occlusion females (n = 16) showed a significantly more rapid early increase in femoral vascular conductance than the full-occlusion fetuses, followed by worsening of bradycardia and hypotension that was intermediate to the full-occlusion fetuses and short-occlusion males. Among all fetuses, MAP at 15 min of occlusion, corresponding with the time of the maximal rate of fall, was correlated with postmortem weight in males (R(2) = 0.07) but not females. In conclusion, male and female fetuses showed remarkably similar chemoreflex and hemodynamic responses to severe asphyxia, but some males did show impaired hemodynamic adaptation within the normal weight range.     

Effect of hypoxic hypoxia on taurine concentrations in ventricles of mouse hearts

The effects of hypoxic hypoxia on the concentration of taurine in right ventricles was studied in the hearts of male CF1 mice caged individually and maintained for 16 hr per day in a hypobaric chamber evacuated to an air pressure of 307 mm Hg. After 23 days hearts were excised and right and left ventricles were separated and lyophilized. Hematocrits in chamber animals were 77-82%, compared to 45-49% for control mice. Mean weights of right ventricles of animals from the chamber were 11.2 +/- 0.9, compared to control values of 7.0 +/- 0.4, mg dry weight. The mean dry weights of left ventricles in both groups of animals were the same. There were no significant differences in the nmoles taurine per mg day tissue in either heart chamber, with mean values +/- S.E.M. of 124.0 +/- 4.6 and 135.0 +/- 4.5 in right ventricles and 128.0 +/- 4.3 and 110.9 +/- 15.3 in left ventricles of experimental and control animals respectively. Thus, hypertrophy which results from hypoxia is not accompanied by increased concentrations of taurine in right ventricles.     

Sex differentiation and mRNA expression of P450c17, P450arom and AMH in gonads of the chicken

The present study was conducted to reveal effects of in ovo injection of nonsteroidal aromatase inhibitor (Fadrozole) or estradiol at day 3 of incubation on mRNA levels of P45017alphahydroxylase (P450c17), P450 aromatase (P450arom) and anti-Müllerian hormone (AMH) in the chicken gonads. The mRNA levels in the gonads at days 4-8 of incubation were assessed by in situ hybridization analysis using digoxigenin labeling method. The in situ hybridization data were analyzed by relative expression of specific hybridizable signals of each mRNA corrected by the non-specific background by employing an image analyzer. P450c17 mRNA expression increased rapidly at day 6 of incubation in the male but decreased thereafter. In contrast to the transient expression in the male, the expression was gradually increased in the female. P450arom mRNA was not expressed in the male but was detectable in the female as early as day 6 and increased subsequently with days of incubation. AMH mRNA was expressed as early as day 5 of incubation followed by a sharp increase on day 6, which was maintained in the male thereafter. In contrast, the female showed very little expression. The injection of Fadrozole caused no effect on P450c17 mRNA expression, while it suppressed P450arom mRNA expression but increased AMH mRNA expression in the female. In contrast, the injection of estradiol induced P450arom mRNA expression significantly but suppressed AMH mRNA expression in the male. These results indicate that expression of P450arom and AMH is sexually dimorphic and is reciprocally regulated during early ontogenic life in chicken gonads.     

Circulating LH, FSH, prolactin, testosterone, delta 4-androstenedione, dehydroepiandrosterone sulfate and cortisol levels in the fetus in late gestation and in newborn male and female lambs

Gonadotropins, prolactin (PRL), testosterone (T), delta 4-androstenedione, dehydroepiandrosterone sulfate and cortisol (F) levels were determined from 14 days before birth to term in 3 female and 3 male ovine fetuses with a chronically implanted venous catheter, and in the same animals from birth to 72 h of age. In both sexes, plasma gonadotropins and androgens were low throughout the period of study while plasma F increased with gestational age. After birth, plasma gonadotropins and PRL tended to increase progressively with time while PRL concentrations were significantly higher in female than in male lambs. F and T concentrations decreased significantly within the first 12 and 6 h of postnatal life. Higher T values were again observed at 36 h in male lambs. These data indicate that the fetal hypothalamic-pituitary-gonadal axis is relatively quiescent in the last 14 days of gestation but is activated within the first 72 h after birth.     

Asymmetry and sexual dimorphism of lungs weight in fetal ontogeny.

1079 male fetuses and 727 female fetuses at the age of 20 to 41 weeks were investigated for the process of asymmetry and sexual dimorphism of lungs weight formation as well as developmental correlation between the weight of the lungs and the size of the heart. Statistical analysis of the results was applied. It was ascertained, among others, that asymmetry of lungs weight occurs in the investigated developmental period--the right lung is heavier than the left one about 20 to 30%. Between the increase in the weight of the lungs and the size of the heart positive correlation occurs, but it is not of directed character. A substantial, intersexual differentiation of lungs weight was not ascertained.     

Reproduction and development in rats chronologically exposed to 60-Hz electric fields

Previous studies have raised the possibility of reproductive and developmental changes in miniature swine chronically exposed to a strong 60-Hz electric field. Two replicate experiments on rats were performed to determine if similar changes could be detected in animals exposed under a comparable regime, which was based on average, induced-current densities and on the chronology of reproductive development, as dosimetrically and biologically scaled. Beginning at three months of age, female rats of the F0 generation and their subsequent offspring were chronically exposed to a 60-Hz electric field (100 kV/m unperturbed) for 19 h/day for the duration of experimentation. After four weeks of exposure, F0 female rats were mated to unexposed male rats during the field-off period. No significant developmental effects were detected in their litters, confirming our previous results with swine and rats. The F0 females were mated for a second time at 7.2 months of age, and the fetuses were evaluated shortly before term. In the first experiments, the incidence of intrauterine mortality was significantly less in exposed than in sham-exposed litters, and there was a tendency (P = .12) for an increased incidence of malformed fetuses in exposed litters. Neither end point was significantly affected in the second experiment. Copulatory behavior of the female F1 offspring, which were bred at three months of age, was not affected in either experiment. There was a statistically significant decrease in the fertility of F1 exposed females and a significant increase in the fraction of exposed litters with malformed fetuses in the first experiment; both end points were essentially the same in the sham and exposed groups of the second experiment. That the significant effects detected in the first experiment were not seen in the second may be attributed to random or biological variation. Alternatively, the finding may indicate that the response threshold for induction of malformations lies near 100 kV/m.     

Testosterone and dihydrotestosterone in sexual ducts and genital tubercle of rabbit fetuses during sexual organogenesis: Effects of fetal decapitation

Testosterone (T) and dihydrotestosterone (DHT) have been measured in the plasma, sexual ducts and genital tubercle in rabbit fetuses of both sexes during sexual organogenesis. T and DHT were also measured in decapitated male fetuses. In male, T appeared successively in testes (day 19), mesonephros (day 20) and Wolffian ducts (day 22). In sexual ducts, T levels increased from 20 to 25 days, then stabilized until birth. Since DHT was measurable, in sexual ducts of males only from 24 days onwards, T itself is the active hormone on the differentiation of Wolffian ducts. In female fetuses, T and DHT were undetectable, in sexual ducts, at any gestational age. In the genital tubercle T was undetectable in both sexes. In the genital tubercle of males DHT levels increased from 19 to 25 days, then stabilized. In female fetuses, DHT was episodically measurable in the genital tubercle but at levels always lower than in males. DHT is the active hormone on the differentiation of genital tubercle. In male decapitated fetuses T and DHT levels were reduced in sexual ducts and genital tubercle but the differences were not significant.     

Potential of fetal germ cells for nuclear transfer in cattle

The developmental potential of bovine fetal germ cells was evaluated using nuclear transfer. Male and female germ cells at three stages of fetal development from 50- to 57-, 65- to 76- or 95- to 105-day-old fetuses were fused to enucleated oocytes 2 to 4 hr prior to activation with 7% ethanol (5 min) followed by 5 hr culture in 10 microg/ml cycloheximide and 5 microg/ml cytochalasin B. The in vitro development of nuclear transfer embryos derived from germ cells was compared with those derived from embryonic cells (blastomeres from day 5 or day 6 embryos). Blastocyst rate (38%) obtained with germ cells from 50- to 57-day-old fetuses tended to be higher than when using germ cells from 65- to 76- or 95- to 105-day-old fetuses (23% and 20%, respectively). Within each stage of fetal development, the proportion of blastocysts derived from male germ cells tended to be higher than that obtained with female germ cells, but due to the high variation between individual fetuses this difference was not significant. With the post activation procedure used in this study, germ cells from 50- to 57-day-old fetuses supported the development of nuclear transfer embryos to the blastocyst stage significantly (P<0.05) better than nuclei of embryonic cells (38% vs. 3%). After transfer of blastocysts derived from germ cells of 50-to 57- and 65- to 76-day fetuses, respectively, 45% (5/11) and 50% (3/6) recipients were pregnant on day 30. The corresponding pregnancy rates on day 90 were 36% (4/11) and 17%(1/6). One live male calf was delivered by cesarean section at day 277 of gestation. Our results show that nuclei of bovine fetal germ cells may successfully be reprogrammed to support full-term development of nuclear transfer embryos.     

Effect of ectopic excitation on the ventricular pump function in chicken

The pump function of the heart ventricles was studied in chest-open anaesthetized adult female chickens under sinus rhythm and ectopic excitation of different localization. The intraventricular pressure in the right and left heart ventricles was measured by insertion of catheters through the ventricular free walls. Maximum systolic pressure, end-diastolic pressure, contractility (dP/dtmax) and relaxation (dP/dtmin) of both heart ventricles, and duration of the asynchronous contraction time of the left ventricle were analyzed. It was revealed that reduction of the pump function of the left ventricle tends to be greater under right ventricular ectopic excitation compared with left ventricular one. In comparison with the sinus rhythm, the pump function of the right ventricle was preserved to a greater extent under stimulation of the left ventricular apex and was significantly impaired under right ventricular ectopic excitation. Relaxation of both heart ventricles was more susceptible to ventricular ectopic excitation than contractility, and was more vulnerable in the right ventricle than in the left one. The direction of changes of the pump function of the heart ventricles in chickens under ventricular ectopic excitation was similar to changes of the pump function of mammalian hearts.     

Developmental expression of bovine adrenocortical steroid hydroxylases. Regulation of P-450(17 alpha) expression leads to episodic fetal cortisol production

The developmental expression of adrenocortical steroid hydroxylases was studied in bovine fetuses from 40 to 280 days gestational age. The expression of P-450(17 alpha) is first detected at a gestational age of 50 days and reaches a maximum at 60-70 days. The expression of P-450(17 alpha) then declines and is nondetectable at a gestational age of 100 days. P-450(17 alpha) is not expressed again until about 240 days, i.e. shortly before birth (approximately 280 days). P-450scc, P-450c21, P-450(11 beta) and adrenodoxin were present in fetal adrenals throughout gestation. This "on-off-on" pattern of P-450(17 alpha) expression during fetal development was associated with a corresponding episodic production of cortisol. Immunoreactive corticotropin (ACTH) levels in fetal plasma were elevated in small fetuses (corresponding to less than or equal to 100 days) and in near-term fetuses (corresponding to greater than 250 days) compared with those in mid-gestation fetuses. In primary culture, adrenal cells from mid-gestation fetuses contained no detectable P-450(17 alpha) but rapidly responded to ACTH with an increase in P-450(17 alpha) protein and mRNA. The tissue specificity of the developmental patterns is emphasized by the fact that both P-450(17 alpha) and P-450scc were detectable throughout the development of the fetal testes, whereas only P-450scc was detectable in fetal bovine ovary prior to 200 days. Thus, in fetal bovine adrenal it appears that ACTH is the major regulatory factor effecting the intermittent presence of P-450(17 alpha), whereas the presence of the other steroid hydroxylases is either regulated by additional factors or shows a much different sensitivity to ACTH.     

The appearance of surface H-2 antigens on fetal and postnatal murine hepatocytes in vivo and in vitro: A comparative study of MHC control

We have collected data on the kinetics of in vivo development of H-2^b antigens in fetal and postnatal hepatocytes from days 15–89 postcoitum (pc) in C57BL/10 mice using a sensitive immunoferritin labeling method combined with electron microscopy. We compared these data with data on the kinetic development of H-2^b antigens on fetal hepatocytes cultured from days 15, 16, and 17 pc onwards. Using the same techniques, we also compared the surface concentrations of H-2 antigens on the hepatocytes of pregnant and age-matched male and virgin female mice at day 110 pc. We found that the surface concentration of H-2 antigens on fetal and postnatal hepatocytes increased with time but that the birth event was associated with an increase in H-2 antigen expression from 60–80 ferritin grains per meter (F/m) to 190 F/m followed by a decrease to 115 F/m within 72 h of birth. The concentration of antigens on postnatal hepatocytes increased gradually and reached a maximum of 640 F/m on day 41 pc. By day 89 pc, however, this level had decreased 433 F/m, which was not significantly different from that found in day 110 pc males and virgin females. In contrast to previous findings, we found that hepatocytes cultured from days 15, 16, and 17 pc exhibited a large increase in H-2 surface antigen concentration within 48 h from 60–80 F/m to 1500–2200 F/m. After day 2, the H-2 concentration decreased and by days 14–17 in culture it was not significantly different from day 110 pc male and virgin female levels (485 F/m). Lastly, we found that the H-2 concentration on hepatocytes from pregnant mice was increased significantly (725 F/m) compared with the concentration of hepatocytes from day 110 pc males or virgin females. We postulate that the control of cell-surface major histocompatibility complex antigen concentration is achieved by a combination of intra and extracellular mechanisms and we discuss how this might be of benefit to the animal in vivo.     

Genetically determined transient edema found in the WB/ReJ mouse strain in a teratogenic survey with acetazolamide

A continuing survey of the genetic variability of different mouse strains to acetazolamide teratogenesis demonstrated the WB/ReJ strain expresses a high frequency of induced subcutaneous edema in day 15 fetuses. In treated WB/ReJ fetuses, the probability of expression of edema is independent of the expression of forelimb ectrodactyly and, with the dosage regime, there is no significant increase in acetazolamide-induced resorption. It was surprising to find a high frequency of spontaneous edema on day 15 in untreated WB/ReJ fetuses. The spontaneous edema is a transient trait with maximum expression (56%) on day 14, and it is resolved by day 17 without apparent consequence to the survival of previously affected fetuses. There is no sex dimorphism in the liability to express the transient edema. Preliminary genetic crosses to investigate the spontaneous edema were made between WB/ReJ and the C57BL/6J strain, which historically had not be observed to express spontaneous edema. A low frequency of spontaneous edema was observed on day 14 in both C57BL/6J and the reciprocal F1 fetuses. The trait is not additive because there is dominance deviation of the BC1 fetuses in the direction of the F1 fetuses. The data were fitted to a threshold model suggesting that the developmental liability to express the difference in transient edema is determined by more than one gene, but the data can be interpreted by a minimum of two loci with duplicate epistasis. The observed differences in frequencies of edema suggest the genetic model can be tested with relatively few test crosses.     

Fetal Sex Ratios in Southwestern Montana Elk

ABSTRACT The Trivers-Willard (1973) model suggests maternal control of offspring sex, in utero or by the end of parental investment, may be an adaptive advantage in some species. We tested for differential sex allocation using 11,408 known-sex fetal elk (Cervus elaphus) from biological collections and hunter harvest returns from 2 southwestern Montana, USA, elk populations (1961–2007). We included maternal and environmental condition covariates measured pre- and postconception and throughout pregnancy. Results suggested that adult female elk in southwest Montana did not differentially invest in male offspring when conditions were beneficial. We found evidence that, when the Northern Yellowstone elk herd was at low density, beneficial spring (May-Jun) growing conditions, as indexed by a local precipitation measure and a regional drought indicator, correlated with production of more female fetuses (1 SD increase in precipitation and 1 SD decrease in drought resulted in 6% and 5% more F fetuses, respectively). In the same herd, we found evidence that improved maternal condition, as indexed by kidney fat mass and heart fat mass, also correlated with production of more female fetuses (1 SD increase in kidney fat mass and heart fat mass resulted in 8% more F fetuses). When the same elk herd reached higher densities under different ecological conditions, no covariate was associated with a deviation in the 50:50 female-to-male sex ratio. Similarly, there was no association between covariates and fetal sex ratios in a nearby elk herd at high population density. In modeling, wildlife managers should consider factors that could alter sex ratios at birth, and also how biased sex ratios postpartum could affect population models.     

Dose- and stage-related sex difference in the incidence of cytosine arabinoside induced digit anomalies in the mouse fetus

Pregnant mice of the Jc1:ICR strain were injected intraperitoneally with a single dose of 2.5, 5, or 10 mg/kg of cytosine arabinoside (Ara-C) on day 9.5 or 10.5 of gestation (dg). Mice were killed on 18.4 dg, and the incidences of digit anomalies were compared between male and female fetuses. In the group treated with 10 mg of Ara-C on 9.5 dg, oligodactyly of the hindlimbs was produced more frequently in male fetuses. In the group treated with 5 mg of Ara-C on 10.5 dg, oligodactyly of the forelimbs tended to occur more frequently in male fetuses. Also, in this group, oligodactyly of the hindlimbs occurred more frequently in male fetuses, whereas polydactyly occurred more frequently in female fetuses. The observed difference in the incidences of digit anomalies between male and female fetuses may be explained either in terms of the sex-related time lag in the critical period for digit development or by a probable sex difference in embryonic susceptibility to Ara-C.     

Virilizing effect of methyltestosterone on female descendants in the rat

Pregnant rats were given daily a subcutaneous injection of methyltestosterone for 4 days from the 17th to the 20th day of gestation, and were allowed to be delivered to their offsprings (F1) which were used for the examination of later reproductive functioning. When observed for 21 weeks after birth, the growth rate of F1 from methyltestosterone-treated groups was higher than that of F1 from the control group. The anogenital distance in 50-microgram-treated F1 females started to become significantly longer on the 14th day and in 5-microgram-treated F1 females on the 28th day after birth than that in F1 from the control. The day on which vaginal opening took place in 50% of females was 34.4 days of age in both the control and the 5 microgram groups, but it delayed until 40.7 days in the 50 microgram group. Furthermore, persistent estrus was observed after about 90 days of age in the 50 microgram group. This persistent estrus disappeared by placing these females with males, resulting no pregnancy. In the 5 microgram group females could be pregnant, but their female fetuses (F2), when examined on the 21st day of gestation, had significantly shortened the length of the urovaginal septum. The observations show that virilization can be induced in the third generation.     

The male genital tract and the nipples of male and female offspring of rats given the non-steroidal antiandrogens DIMP and Sch 13521, during pregnancy.

Male and female offspring of rats given antiandrogens, the steroidal BOMT or the non steroids DIMP or Sch 13521, daily during the last third of pregnancy were studied. Detailed examinations were made of the genital tract of male, and of the nipples of male and female offspring. A) Male offspring. 1) Genital tract of newborn and 31-91 day old males : Modifications of the development of accessory sexual tissues were found in all treatment groups. As indicated by the severity of deviations from normal (morphology and weight of sex accessories), the antiandrogenic effect of the preparations, in the doses given to the mother rats, increased from BOMT (50 or 75 mg/day) via Sch 13521 (30 mg/day) and DIMP (50 or 60 mg/day) to Sch 13521 (60 mg/day). 2) Nipples of 10-60 day old males : Whole mount preparations were made unilaterally of the row of 6 mammary glands with nipples. The number of intact and abnormal nipples, respectively, was recorded. The relation between intact and abnormal nipples served as indicator of the efficiency of the antiandrogenic substances studied. The result showed that the antiandrogenic effect increased from BOMT to Sch 13521, 60 mg, in the same order as that arrived at from studies of the genital tract. The combined results obtained from the male offspring indicated that the tissues of the genital region, the growth and differentiation of which was most readily impaired by antiandrogens, were the same as those known from other work to be stimulated most easily in female rat fetuses by testosterone. B) Female offspring. Nipples of 31-60 day old females were judged from whole mount preparations and recorded as in the males. The nipples of adult virginal females were examined macroscopically. The same procedure was applied to lactating females, but the results were controlled in consecutive lactational periods and at autopsy. The 3 groups of females showed uniformly that 1) offspring of rats given BOMT during pregnancy had many (about 50 per cent) malformed nipples and 2) the treatment of mother rats with DIMP or Sch 13521 did not influence the development of nipples in female offspring. The result was assumed to be due to an androgenic effect of the steroidal antiandrogen, BOMT, on the nipple anlage.     

Time-response and dose-response to acetazolamide in the WB/ReJ and C57BL/6J mouse strains: genetic interaction in the ectrodactyly response

The WB/ReJ and C57BL/6J strains were compared in their time and dose responses to acetazolamide administered in a single subcutaneous injection regime. WB/ReJ has a genetically determined, high-frequency, transient fetal edema that has maximum expression on day 14 and is resolved by day 18. Acetazolamide, at 1,000 mg/kg, appears to induce edema in WB/ReJ with a time of response on days 9 and 10, and the induced edema follows the same time course of appearance and disappearance as the spontaneous trait. The dose-response analysis is not interpretable in the WB/ReJ and C57BL/6J strains and their reciprocal F1 fetuses because there was significant response only at the highest dose (2,000 mg/kg) used in this study. The time of ectrodactyly response is maximal on day 9 in both WB/ReJ and C57BL/6J strains. The dose-response analysis demonstrates that, for the usual measure of total fetuses with ectrodactyly (or penetrance), the Wb/ReJ and C57BL/6J strains and the WB/ReJ x C57BL/6J F1 (WB.B6F1) have the same slope of the dose-response curve and the strain difference in response can be interpreted as a difference in dosage tolerance. The tolerance of WB/ReJ is twofold greater than that of C57BL/6J. This overdominance of relative resistance to acetazolamide ectrodactyly supports the general finding of directional dominance of relative resistance among genetically different strain pairs. The median effective dose for penetrance of the ectrodactyly response of the reciprocal B6.WBF1 embryo is similar to the WB.B6F1, but the slope of the dose-response curve is significantly different, and a different teratogenic mechanism of response may be involved. Ectrodactyly was predominantly right sided in all genotypes, and, in bilaterally affected fetuses, the right forelimb was more severely affected. An unexpected difference between WB/ReJ and C57BL/6J was found when the laterality of ectrodactyly was analyzed further. There is a significant increase with dosage in bilaterally affected fetuses (a measure of expressivity) in C57BL/6J but not in WB/ReJ, even though the dose-response of total affected fetuses (penetrance) is similar in both strains. In C57BL/6J, the left and right forelimbs are correlated in their responses with the left, requiring approximately a threefold greater dose. The left and right forelimbs are symmetrical in response, and the difference can be interpreted in terms of a developmental (or teratogenic) gradient. In WB/ReJ, the right forelimb has the same dose response as C57BL/6J and requires a twofold greater dose than the right forelimb of C57BL/6J, but the left forelimb has a very flat slope and is not correlated with the response of the right.(ABSTRACT TRUNCATED AT 400 WORDS)