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PubMed1989

Automated assignment of behavioural states in the human near term fetus.

Thirty-five 2-h recordings of fetal heart rate and fetal movements, made at 38-39 weeks of gestational age, have been analyzed in a partly automated procedure. Involved were 17 nulliparous and 19 multiparous women. To minimize subjectivity the classification of the heart rate was performed in a Delphi group opinion procedure consisting of three rounds. In the third round, three independent investigators classified 89.1% of the total tracing time as pattern A through D. The investigators could not classify 6.1% of the tracing time in any of the available categories. The percentages of coincidence of state parameters did not differ significantly between the fetuses of nulli- and multiparous women. Fifty percent of the fetuses showed true behavioural states, both in the nulli and the multiparous women. The percentage of time spent in state 1F was higher in the multiparous group (P less than 0.05). The other percentages of states did not differ significantly, neither did the duration of the enclosed epochs. The advantages and disadvantages of the automated assignment of fetal behavioural states are discussed.

Computers↗
PubMed2004

Enhanced growth and improved vascular function in offspring from successive pregnancies in endothelial nitric oxide synthase knockout mice.

OBJECTIVE: Transgenic mice that lack endothelial nitric oxide synthase have offspring with growth deficiency and abnormal vascular reactivity in later life. Our objective was to evaluate the role of parity in the modulation of the fetal programming of growth and vascular responses in these transgenic mice. STUDY DESIGN: Oligoparous (0-2 previous pregnancies) and multiparous (5-9 previous pregnancies) nitric oxide synthase knockout (-/-KO) female mice were bred with nitric oxide synthase -/-KO and wild type (+/+WT) male mice to produce nitric oxide synthase -/-KO and maternally derived heterozygous (+/-Mat) litters. The pups were weighed weekly. Carotid arteries of the adult females from these litters were used for in vitro vascular reactivity studies. RESULTS: Nitric oxide synthase knockout and nitric oxide synthase maternal litters that were born to oligoparous mothers had significant growth lag compared with corresponding multiparous litters. Length-tension characteristics were not different between the groups. However, optimal diameter, which is a measure of vascular tensile properties and resistance, was decreased in oligoparous compared with multiparous female offspring. Acetylcholine-mediated vasorelaxation was abolished, and contraction by phenylephrine and Ca ++ was increased in oligoparous, but not multiparous, female offspring ( P < .05). CONCLUSION: These data support the role of abnormal uterine environment in the fetal programming of postnatal growth and vascular function in later life. Successive pregnancies may lead to maternal uterine adaptations that bypass the lack of a functional nitric oxide synthase, which leads to improvement in postnatal growth and vascular function in the offspring. Given the reported effect of parity on the risk of preeclampsia, similar mechanisms may be operative in human pregnancy.

Animals↗
PubMed2004

Reproductive performance of gilts and sows in temperate versus subarctic and arctic zones of Norway.

The reproductive performance of gilts and sows from two regions in Norway was investigated in a retrospective analysis of data from the litter recording system. In the Northern region (North; between 65 degrees N and 71 degrees N), there are extreme shifts in natural photoperiod between winter and summer. In the Southern region (South; between 59 degrees N and 60 degrees 30'N), photoperiodic changes are less dramatic. Gilts were 8 days older at first mating or insemination in the North than in the South (P<0.01). A significantly lower proportion of sows in the North were mated or inseminated within 5 days post-weaning than in the South, a difference present both among primiparous and multiparous sows (P<0.01). Overall farrowing rate in the North was lower than in the South, but litter size (total number born) among those pigs that farrowed was larger. After correction for year, month, breed and age at first service, there were still lower odds of farrowing for gilts in North than in South. Neither for primiparous nor multiparous sows were regional differences in farrowing probability significant when year, month, breed and weaning to service interval were included in the model. Gilts and primiparous sows had a lower probability of farrowing following insemination during summer or autumn months, but service month was not significantly related to the farrowing probability of multiparous sows. For gilts, litter size was positively related to age at first service. For sows, litter size was lowest at weaning to service intervals between 6 and 10 days. Total numbers of piglets born per litter were estimated to be 0.36, 0.38 and 0.55 larger in the North than in the South (differences in least square means; gilts, primiparous sows and multiparous sows, respectively) (P<0.01). Litter size was lower after service during natural long photoperiod than during the rest of the year.

Aging↗
PubMed2004

Association of increased estrogen receptor beta2 expression with parity-induced alterations in the rat mammary gland.

In this study, we investigated the cellular and molecular events involved in parity-related alterations in mammary gland (MG) proliferation and differentiation. Rat MGs were removed on day 9 of either first (nulliparous), second (primiparous) or third (multiparous) pregnancy. Expression of steroid hormone receptors along with cellular biomarkers of proliferation and differentiation were quantified in all MG tissue compartments by immunohistochemistry. Wnt-4 (a Wingless-like morphogenic gene involved in MG development), ERbeta and ERbeta2 mRNA were evaluated by RT-PCR analysis. Serum levels of mammotrophic hormones were measured. In comparison to nulliparous and primiparous rats, multiparous animals exhibited decreased luminal cell proliferation and PR levels, whereas alpha-lactalbumin, ERalpha, ERbeta and ERbeta2 expression were increased. In myoepithelial cells, while parity induced a decrease in proliferative activity, subsequent pregnancies and lactations lead to an increased state of differentiation. Our results showed that at least two periods of pregnancy and lactation were necessary to modify the studied parameters. The lower proliferative activity and higher differentiation state of the multiparous MG are associated with both a decreased PR expression and increased ERalpha and ERbeta expression. Since ERbeta and/or ERbeta2 isoform expression was related to parity history, results suggest that the decreased proliferative activity and PR expression observed in the MG of multiparous animals may be associated with overexpression of ERbeta and/or the ERbeta2 isoform, thereby antagonizing the proliferative effects associated with ERalpha.

Animals↗
PubMed2006

Diurnal salivary cortisol levels in postpartum mothers as a function of infant feeding choice and parity.

Daily stress and sleep deprivation can influence the diurnal pattern of cortisol, which normally consists of high morning levels and a gradual decline throughout the day. While most individuals have consistent declining cortisol concentrations over days, others display either flat or inconsistent profiles. Postpartum mothers experience considerable home demands and sleep deprivation, yet, breastfeeding mothers perceive lower stress and reduced negative mood states compared to bottlefeeders. On the other hand, multiparity (having more than one child) is associated with reduced steepness in diurnal cortisol decline. Interestingly, no study to date has investigated the diurnal cortisol pattern and its stability across days in postpartum women as a function of their choice of infant feeding and parity. In this study, we measured salivary cortisol at four different time points during the day, on two non-consecutive days in first-time (primiparous) and second-time (multiparous) mothers at 5-20 weeks postpartum who were exclusively breastfeeding or bottlefeeding, and in non-postpartum mothers of young children (1-6 years). Among multiparous mothers, we found that cortisol levels in those who were bottlefeeding were higher than in breastfeeding mothers at both awakening and 1600 h. This effect remained significant after controlling for individual differences related to infant feeding choice, such as estradiol levels, education and income. No effect of infant feeding choice on cortisol concentrations was observed in primiparous mothers. While a consistent decline across days was common, some mothers presented a flat or inconsistent profile, a profile that was not associated with infant feeding choice or parity. Importantly, mothers with consistent declining profiles had the highest household income. Our findings suggest that although breastfeeding might promote a tighter regulation of diurnal basal cortisol secretion, in particular for multiparous mothers who are likely to be exposed to greater home demands and maternal responsibilities, some aspects of socioeconomic status such as income can also play a significant role in the stability of diurnal cortisol secretion across days.

Adult↗
PubMed2005

Overexpression of human Cripto-1 in transgenic mice delays mammary gland development and differentiation and induces mammary tumorigenesis.

Overexpression of Cripto-1 has been reported in several types of human cancers including breast cancer. To investigate the role of human Cripto-1 (CR-1) in mammary gland development and tumorigenesis, we developed transgenic mice that express the human CR-1 transgene under the regulation of the whey acidic protein (WAP) promoter in the FVB/N mouse background. The CR-1 transgene was detected in the mammary gland of 15-week-old virgin WAP-CR-1 female mice that eventually developed hyperplastic lesions. From mid-pregnancy to early lactation, mammary lobulo-alveolar structures in WAP-CR-1 mice were less differentiated and delayed in their development due to decreased cell proliferation as compared to FVB/N mice. Early involution, due to increased apoptosis, was observed in the mammary glands of WAP-CR-1 mice. Higher levels of phosphorylated AKT and MAPK were detected in mammary glands of multiparous WAP-CR-1 mice as compared to multiparous FVB/N mice suggesting increased cell proliferation and survival of the transgenic mammary gland. In addition, more than half (15 of 29) of the WAP-CR-1 multiparous female mice developed multifocal mammary tumors of mixed histological subtypes. These results demonstrate that overexpression of CR-1 during pregnancy and lactation can lead to alterations in mammary gland development and to production of mammary tumors in multiparous mice.

Animals↗
PubMed2000

Alterations in humoral immune responses associated with recurrent pregnancy loss.

OBJECTIVE: To investigate the reactivity of maternal antibodies with endometrium-derived antigens and to correlate their association with recurrent pregnancy loss (RPL). DESIGN: Prevalence study. SETTING: Academic research center. PATIENT(S): Nulliparous women (n = 10), women with RPL (n = 15), pregnant women (n = 8), and multiparous women with a normal obstetric history (n = 20). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Reactive antibodies were analyzed by Western immunoblot techniques and quantitated by densitometry. RESULT(S): Antibodies from women with RPL and multiparous women recognized antigens ranging from 10-120 kd on normal endometrium and endometrial tumors. Antibodies from most women with RPL (10/15) and from multiparous women (15/20) recognized 65-kd and 80-kd proteins in normal endometrium. Antibodies from women with RPL recognized 21-kd and 28-kd antigens (12/15 and 13/15, respectively) in endometrial tumors at a significantly greater rate (than did antibodies from multiparous women (5/20 and 8/20, respectively). Women with RPL had significantly lower levels of asymmetric IgG compared with controls. CONCLUSION(S): Recurrent pregnancy loss may be linked with the failure to elicit asymmetric IgG and a unique immunologic recognition of endometrial antigens.

Abortion, Habitual↗
PubMed2000

Adverse effects of epidural analgesia in labor.

OBJECTIVE: To examine the influence of epidural analgesia on labor and delivery in nulliparous and multiparous women. DESIGN: Data were collected on 847 consecutive parturients with singleton pregnancy and vertex presentation (384 nulliparous and 463 multiparous). The obstetrical and labor characteristics including maternal age, parity, gestational age, previous cesarean section, instrumental delivery, mode and timing of analgesia, mode of delivery, indications for cesarean section or instrumental delivery were analyzed comparing patients who received epidural analgesia with women who received systemic analgesia. RESULTS: Epidural analgesia was administered in 233 nulliparous and 141 multiparous women. A stepwise logistic regression analysis revealed that epidural analgesia independently affected the rate of non-spontaneous delivery and the duration of the second stage of labor in nulliparous (P=0.0017 and P=0.0036, respectively) and multiparous (P=0.001 and P=0.0081, respectively) women. Epidural analgesia independently affected the duration of labor only in nulliparous women (P=0.0001). CONCLUSION: Women should be informed that prolongation of labor and increase in nonspontaneous deliveries should be expected when choosing epidural analgesia in labor.

Adult↗
PubMed2005

A comparison of urinary and sexual outcomes in women experiencing vaginal and Caesarean births.

OBJECTIVE: To evaluate the urinary and sexual consequences of vaginal delivery compared with Caesarean section. METHODS: We performed a cohort analysis of data from a randomized controlled trial of episiotomy conducted in 3 Montreal hospitals in 1990-1991. Of the 999 trial participants for whom follow-up data were available, 135 delivered by Caesarean section (CS), and 864 had a vaginal birth (VB). After stratifying for parity, we compared rates of urinary incontinence (UI) and sexual functioning at 3 months postpartum in women who had a VB with the rates in women who had a CS. RESULTS: Primiparous women reported unspecified UI at 3 months postpartum more often (17.9%) in the VB group than in the CS group (6.4%). This difference remained significant whether or not there was a prior history of UI. Multiparous women showed no difference in rates of UI (VB 17.1% vs. CS 16.0%), whether there was a prior history of UI or not. Stress incontinence was greater among primiparous women in the VB group (VB 34.5% vs. CS 12.8%) regardless of prior UI history, but the proportion of women whose UI was severe enough to wear a pad was similar in primiparous women (VB 16.0%, CS 15.4%) and multiparous women (VB 23.8%, CS 25.0%). Women's sexual dissatisfaction was greater among primiparous women who had a vaginal birth (VB 70.1%, CS 54.5%), but in multiparous women, the rates of sexual dissatisfaction were similar (VB 64.2%, CS 71.4%). The frequency of dyspareunia for each mode of delivery was similar in primiparous women (VB 30.7%, CS 31.6%). Overall, both primiparous and multiparous women who had intact perineums after VB had less dyspareunia than those undergoing CS (VB 26.2, CS 40.7%). However, the proportion of women experiencing dyspareunia was greatest among those who had an episiotomy with or without forceps.

Adult↗
PubMed2001

Fear during labor.

BACKGROUND: The aims of the present study were to compare primiparous and multiparous women's experiences of fear of delivery during an early stage of active labor (cervix dilatation 3-5 centimeters) and to study whether fear of delivery, measured during the early stage of active labor, was a predictor of the amount of pain relief received during the remaining part of labor (cervix dilatation 5 cm - partus), of the duration of the remaining part of labor, and of the occurrence of instrumental vaginal delivery and emergency cesarean section. METHOD: Thirty-five primiparous and 39 multiparous women answered the Delivery Fear Scale (DFS) once during the early stage of labor and before they had received any pain relief. RESULTS: Primiparous women reported higher levels of fear than multiparous women did. Fear during the first phase of labor predicted only the total amount of pain relief received during labor. CONCLUSION: The clinical implications of the study are that the delivery staff should consider women's fear during labor and pay attention especially to primiparous women's increased risk of higher levels of fear during an early stage of active labor, as compared with multiparous women's. The challenge for staff of a delivery ward is to support the woman in labor in a way that decreases fear, which in turn might reduce the woman's need of pain relief.

Adult↗
PubMed2000

The Preterm Prediction Study: prediction of preterm premature rupture of membranes through clinical findings and ancillary testing. The National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network.

OBJECTIVE: Our objective was to determine the relative importance of demographic characteristics, clinical risk factors, and ancillary screening tests in the prediction of preterm birth as a result of premature rupture of membranes. STUDY DESIGN: A total of 2929 women were evaluated in 10 centers at 23 to 24 weeks' gestation. Demographic and clinical characteristics were ascertained. Cervicovaginal fetal fibronectin and bacterial vaginosis were evaluated. Cervical length was measured by vaginal ultrasonography. Patients were evaluated for spontaneous preterm birth caused by preterm premature rupture of membranes at <37 and <35 weeks' gestation. Multivariate analyses were performed separately for nulliparous women and multiparous women. RESULTS: Premature rupture of membranes at <37 weeks' gestation complicated 4.5% of pregnancies, accounting for 32.6% of preterm births. Univariate analysis revealed low body mass index, pulmonary disease, contractions within 2 weeks, short cervix (</=25 mm), positive results of fetal fibronectin screening, bacterial vaginosis, and a previous preterm birth caused by premature rupture of membranes (in multiparous women) to be significantly associated with preterm birth caused by premature rupture of membranes in the current gestation. Short cervix, previous preterm birth caused by premature rupture of membranes in multiparous women, and presence of fetal fibronectin were the strongest predictors for both preterm birth caused by premature rupture of membranes at <37 and <35 weeks' gestation. Women with positive fetal fibronectin screening results and a short cervix had greater risks both of preterm birth caused by premature rupture of membranes at <37 weeks' gestation (relative risk, 4.9) and of preterm birth caused by premature rupture of membranes at <35 weeks' gestation (relative risk, 13.5) than did those without these risk factors. Multiparous women with all three risk factors had a 31. 3-fold increased risk of preterm birth caused by premature rupture of membranes at <35 weeks' gestation. CONCLUSION: The combination of short cervical length, previous preterm birth caused by preterm premature rupture of membranes, and positive fetal fibronectin screening results was highly associated with preterm delivery caused by preterm premature rupture of membranes in the current gestation.

Cervix Uteri↗
PubMed2002

Parity and pregnancy outcomes.

OBJECTIVE: The issue of parity and risk of pregnancy outcomes has been controversial for many decades. We conducted a study to evaluate the association between parity and pregnancy outcomes and to clarify the basis of the classification of risk based on parity. STUDY DESIGN: The study is a cross-sectional analysis on a large routinely collected data set of singleton births from 1992 to 1997 in New South Wales, Australia. Pregnancy outcomes were compared among parity groups. RESULTS: There was a significant association between different parity levels and pregnancy outcomes in terms of obstetric complications, neonatal morbidity, and perinatal mortality, after adjustment for potential confounders, including age, maternal smoking status, and socioeconomic status. In terms of obstetric complications, neonatal morbidity, and perinatal mortality, subjects can be classified into 3 groups according to parity: nulliparity, low multiparity (parity 1, 2, and 3), and grand multipara (parity 4 to 8). Compared with low multiparity, mothers and babies of nulliparity and grand multipara are at higher risk. CONCLUSIONS: This study supported the definition of grand multiparity that should start from parity 4 or the 5th baby. Attention should be paid to subjects of nulliparity and grand multiparity for their different problems.

Australia↗
PubMed2002

Demographic and obstetric factors influencing pregnancy outcome in twin gestations.

OBJECTIVE: Our purpose was to identify the influence of parity and previous preterm delivery on pregnancy outcome in twin gestations. STUDY DESIGN: A retrospective comparative analysis of women with twin gestations completing an outpatient preterm labor surveillance program between April 1995 and February 2000 was performed. Included were those enrolled at <24 weeks' gestation. Parity, maternal age, prepregnancy body mass index (BMI), cerclage, tocolytic use, and pregnancy outcome were identified. Data were divided into nulliparas, multiparas without previous preterm delivery, and those with previous preterm delivery. Analysis of variance and the Pearson chi2 test were used for statistical analysis. RESULTS: Data were analyzed for 1268 twin pregnancies. The mean gestational age at delivery for the multiparous women without a history of previous preterm delivery (35.3 +/- 2.7 weeks) was significantly greater than the mean gestational age at delivery for nulliparous (34.4 +/- 3.2 weeks) and multiparous women with a previous preterm delivery (34.0 +/- 3.1 weeks), P <.001. The greater gestational age at delivery in the multiparous women without a previous preterm delivery was associated with a significantly shorter newborn hospital stay and a lower need for mechanical ventilation use compared with the other groups (all P values < or =.001). CONCLUSION: In twin gestations, multiparous women without history of previous preterm delivery have a significantly greater gestational age at delivery, a lower incidence of cerclage, and a reduced neonatal hospital stay than do nulliparous women or those with a history of a previous preterm delivery.

Analysis of Variance↗
PubMed2001

Has consanguinity any impact on occurrence of pre-eclampsia and eclampsia?

In this study we tested the hypothesis of an association between consanguinity and pre-eclampsia/eclampsia. This is a case-control study conducted at Princess Badea Teaching Hospital, Irbid-Jordan during the period May 1997-April 1998. The study population were Jordanian women delivered at Princess Badea Teaching Hospital with or without hypertensive disorders of pregnancy. The total number was 208 pre-eclamptic/eclamptic women (76 primiparous and 132 multiparous) and 618 randomly selected non-hypertensive women. In primiparous as well as multiparous women, it was evident that neither consanguinity nor the degree of the relationship to the husband in consanguineous marriages had an impact on the incidence of preeclampsia/eclampsia. However, comparing the incidence of consanguinity between pre-eclamptic/eclamptic and non-hypertensive, multiparous women married to a relative other than first cousin, the P value was 0.0248, which we explained as chance incidence. When we compared the incidence of consanguineous marriages as a whole between pre-eclamptic/eclamptic and non-hypertensive, multiparous women, there was no evidence of any impact of consanguinity on the incidence of pre-eclampsia/eclampsia.

Journal Article↗
PubMed1991

Digestion in steers and lactational performance of Jersey cows fed diets varying in natural protein level continuously or on alternate days.

Five crossbred beef steers (515 kg) were used in a Latin square experiment and 36 lactating Jersey cows (12 primiparous, 310 kg; 24 multiparous, 365 kg) were used in a completely randomized design study to determine effects on characteristics of digestion and lactational performance of daily alternation of the dietary level of natural protein (NP). In Experiment 1, steers were fed diets of 50% bermudagrass hay and 50% concentrate. Concentrate was approximately 18% crude protein (CP), formulated to be 60, 80 or 100% NP (varying proportions of soybean meal, urea and ground corn), and was fed at 1.5% body weight (dry matter basis). These concentrates were fed daily or ones with 60 and 100% NP were fed on alternate days. Alternate day feeding did not markedly affect characteristics of digestion, including ruminal escape of feed protein, and NP level of concentrate fed continuously had no effects either. In Experiment 2, cows were subjected to treatments similar to those in Experiment 1, and performance on d 20-40 of lactation was measured. Concentrate was given at 1 kg (as fed)/2.15 kg milk produced, yielding a dietary concentrate level of approximately 40% (dry matter basis). Alternate feeding depressed (P less than 0.05) overall milk fat percentage. Alternate feeding increased production of milk and protein and body weight of primiparous cows but caused little change with multiparous cows. Besides increasing the dietary level of concentrate, perhaps alternate feeding regimes have utility to lower milk fat level without impairing milk production. Level of NP in concentrate fed continuously did not affect performance by multiparous cows though primiparous cow performance was generally enhanced, possibly because CP intake was adequate for multiparous cows but marginal for primiparous cows. However, overall, efficiency of production of solids-corrected milk rose slightly with increasing NP.

Ammonia↗
PubMedDate not supplied

Inefficiency of lactation in primiparous rats: the costs of first reproduction.

To investigate the energetic costs of lactation in a female mammal in relation to previous reproductive history, we compared the performance of adult female Long-Evans rats that had previously bred (multiparous) with young females that had not previously given birth (primiparous). All litters were standardized to 10 +/- 1 young. We compared maternal production (growth of pups), body mass, and energy intake (food consumption) of mothers, as well as their energy expenditure (resting oxygen consumption). The mass of litters at birth and the growth of pups during lactation did not differ according to reproductive history of the mothers. The body mass of primiparous mothers was less than that of multiparous mothers, and primiparous mothers showed an increase in mass during early lactation. To accomplish the essentially identical production of offspring under these circumstances, the primiparous mothers consumed and expended more energy than the multiparous mothers. This remarkable performance of first-time mothers results in an overall efficiency of energy allocation to reproduction amounting to only 25%, compared with 38% in multiparous mothers. The energetic inefficiency of primiparous female lactation results largely from the excessive expenditures associated with physiological and behavioral performances of first-time reproduction, together with a small component of additional expenditure due to further growth by the primiparous mothers. We suggest that this inefficiency probably contributes to the observed low reproductive success of novice breeders; furthermore, active restraint of fecundity may be an evolutionary response to the constraints of the energetic inefficiency of primiparous breeding by female mammals.

Analysis of Variance↗
PubMed1981

The effect of parity on maternal hair chromium concentration and the changes during pregnancy.

The effect of parity of maternal hair chromium and the changes during pregnancy were investigated. Hair samples were collected from nulliparous and multiparous women and longitudinally from pregnant women. Chromium was determined by flameless atomic absorption. Mean hair chromium in multiparous women was low when compared with nulliparous women of comparable ages. No significant decrease in hair chromium was observed between multiparous women and women who had borne only one child. Mean hair chromium in longitudinal samples was observed to decrease with advancing pregnancy. When initial hair chromium values were below 200 ng/g, the significant decrease occurred only in the 3rd trimester of pregnancy. These results show that 1) hair chromium in multiparous women is lower than that in nulliparous women, 2) depending on chromium nutrition, hair chromium of pregnant woman shows a decrease with advancing pregnancy, 3) if adequate amounts of chromium are not taken during pregnancy, deficiency may result with increasing parity.

Chromium↗
PubMed1981

Selenium and the genesis of murine mammary tumors.

One hundred forty-seven female Sprague-Dawley rats were divided into 5 groups and at 60 days of age were treated i.g. with 5 mg of 7,12-dimethylbenzanthracene (DMBA) suspended in 1.0 ml of sesame oil. Selenium (Se), as selenium dioxide (SeO2), was administered in the drinking water to 4 of the 5 groups (30 rats/group) at 2 doses (2 and 4 mg/l) from 30-90 days of age (series 1) and from 90-150 days of age (series 2) prior to the onset of palpable mammary tumors. One group of rats (27 rats) served as controls. All rats were palpated weekly for mammary tumors and sacrificed 28 weeks after DMBA treatment. Total number of palpable mammary carcinomas which developed in each group were: controls, 60; series 1, 2 mg Se dose, 27, 4 mg Se dose, 29; series 2, 2 mg Se dose, 24, 4 mg Se dose, 32. Each dose level of Se in each series significantly (P less than 0.05) reduced the incidence of mammary carcinomas. These results provided evidence that Se can inhibit the early promoting phases of polycyclic hydrocarbon induced mammary carcinogenesis in female rats. Two hundred twenty-six nulliparous and 99 multiparous GR mice were treated daily with estrogen and progesterone for 13-16 weeks. Se (SeO2) was administered in the drinking water (2 mg/l) to one-half of these mice. Total number of mammary carcinomas in control nulliparous and multiparous mice were 119 and 90, respectively; in Se treated nulliparous and multiparous mice, 113 and 81, respectively. Se did not significantly effect mammary carcinoma incidence in hormone treated nulliparous and multiparous GR mice.

9,10-Dimethyl-1,2-benzanthracene↗