Some effects of a split litter cross foster design applied to 15 day old rat pups

Rat litters were divided and cross fostered on a postnatal Day 15 so that each mother had 4 of her own pups and 4 pups of a second litter, until weaning at 21 days. Daily weight and body temperature measurements made between Day 15 and 21 showed no differences between foster pups and pups who stayed with their biological mothers. However, by the age of 30 days, foster pups weighed less than pups reared by their own (biological) mothers; and foster pups at that age did not survive food deprivation as well as the pups reared by their biological mothers. In their Day 30 weights and the capacity to survive food deprivation, foster pups resembled pups that had been permanently separated from their mothers on postnatal Day 15. We conclude that the split cross foster design may introduce variability rather than reduce it. Nonetheless, this design may be useful in the experimental investigation of maternal behavior and mother-pup interactions in the rat.     

Biologic risk factors for low birthweight in Al Ain,United Arab Emirates

A prospective study of biological factors for low birthweight (LBW) among UAE nationals in the Al Ain Medical District was undertaken from 15 January 1992 to 14 January 1993, using a case control method. All 293 mothers of LBW infants and an equal number of mothers of the next normal weight infants born after the LBW infant were studied. Of the 3,485 live births, 293 (8.4%) were LBW (less than 2,500 g). Maternal age less than 25 years, lighter weight at booking, nulliparity, first cousin marriage and short interpregnancy interval (IPI) of 3 months or less significantly increased the risk of LBW in this population. After adjusting for other biologic confounders, only low maternal weight and short IPI significantly increased the risk of LBW. Modification of these biologic risk factors would help to reduce the incidence of LBW among the UAE population. © 1996 Wiley-Liss, Inc.     

Mother-offspring interaction and pup development in genetically deaf mice

The role of ultrasonic calls emitted by pups on maternal behavior has been investigated by using genetically deaf (dn/dn) and normal-hearing (+/+) mice of the GFF strain. The behavior and the sensory-motor development of unfostered and cross-fostered pups, as well as the behavior of the mothers, was analyzed. Deaf pups emitted fewer ultrasonic calls than pups with normal hearing. The cross-fostering procedure decreased the amount of vocalizations produced by normal pups, thus stressing the reinforcement effect of maternal behavior on pups' ultrasonic communication. No difference in maternal behavior emerged between deaf and normal-hearing mothers toward their pups. However, cross-fostered pups received less maternal care than pups raised by their natural mothers, this effect being more evident in deaf pups reared by mothers with normal hearing, than vice versa. Deafness, in both mothers and pups, seemed to be associated with increased locomotor activity, possibly to offset their auditory handicap in mother-offspring relationships. Furthermore, deaf pups showed a faster gain in weight than normal pups, this capability being affected by the genotype of the rearing parent. On the whole, these data could suggest that maternal behavior in deaf mice has became independent of ultrasonic stimuli emitted by the pups. Other biobehavioral characteristics of deaf mice indicate a more active role played by these pups in mother-offspring interaction in comparison with pups with normal hearing.     

Assessing the net effect of young maternal age on birthweight

Pregnancy during adolescence presents an increased risk for low birthweight, which is attributed not only to physiologic immaturity but also to socioeconomic and behavioral risk factors associated with adolescence. The independent effect of maternal age on birthweight is difficult to ascertain because age is closely entangled with these risks. We first examined the effect of being an adolescent mother on these risk pathways and then estimated the net effect of maternal age on birthweight (weight in grams or low birthweight (<2,500 g)) after controlling for these risks. We used data on 214 adolescent and 415 adult primiparae and their infants from the Cebu Longitudinal Health and Nutrition Survey, a community‐based survey in Metro Cebu, Philippines. Consistent with findings from other studies, adolescents in this sample were more socioeconomically disadvantaged, had poorer nutritional status during pregnancy, and received less prenatal care than adults. Bivariate analyses showed that infants of adolescents had a lower mean birthweight and were more at risk of low birthweight compared to those born to older mothers. When socioeconomic, biological, and behavioral risk factors were controlled for, young maternal age ceased to have an effect on birthweight in grams but remained a significant predictor of low birthweight. The common pathways through which maternal age influenced both birthweight variables were through its effects on maternal height and weight‐for‐height during pregnancy. In the model predicting birthweight in grams the maternal age effect was further manifested through prenatal care utilization. Am. J. Hum. Biol. 15:733–740, 2003. © 2003 Wiley‐Liss, Inc.     

Maternal behavior in the undernourished rat (Rattus norvegicus)

Undernutrition was produced in rat pups and their mothers by allowing the mothers access to only 40 percent of the food that they normally would eat. Undernourished or well nourished rat pups were fostered on undernourished or well nourished mothers when the pups were 8 days old. Retrieving times and maternal behaviors were recorded for a period of 2 hr. Neither the well nourished nor undernourished mothers treated the undernourished pups significantly differently from the well nourished pups. The undernourished mothers spent more time than well nourished mothers in exploratory behaviors (rearing up and sniffing) and took longer to retrieve their pups. No significant differences occurred in the time spent with the pups or other maternal behaviors. Decreases in maternal attentiveness to pups found in previous studies may be a result of competition from exploratory or food seeking behaviors.     

Preobesity in the infant OLETF rat: the role of suckling

The Otsuka Long Evans Tokushima Fatty (OLETF) rat model of obesity, which lacks CCK(1) receptors, has been extensively investigated over the last decade. We have recently focused on the early developmental stages of this strain, finding that OLETF pups are heavier than controls from birth and hyperphagic already from postnatal (PN) Day 2. OLETF mothers present differential maternal behavior patterns and increased nursing time and frequency, which might contribute to the preobese characteristics of the pups. The present investigation examined the pups' ability to gain weight from the nursing episodes. First, we measured the pups' weight gain from one nursing bout from their own dam. Next we examined the pups' weight gain after a feeding competition test with control pups from foster dams of both strains. OLETF pups gained more weight than controls from their own dams on PN Week 1 due to a higher suckling rate (and/or efficacy) and on PN Week 3 due to increased nursing time. When competing with control pups, OLETF pups gained significantly more weight after the same nursing bout, regardless of the strain of the mother. Body mass index (BMI) was significantly higher in OLETF pups compared to controls. The maternal parameters assessed from the experiment were latencies to pup retrieval and to nursing, and nursing duration; differences were only observed in nursing time. OLETF dams increased their average nursing time over the PN weeks, while control dams decreased their nursing time toward weaning. The results suggest an important contribution of OLETF pups toward their own preobese development.     

Energetic limits on reproduction: Maternal food intake

We examined the factors influencing maternal food intake and pup growth in Norway rats. Mother rats allowed pups in naturally large litters to grow at a slower rate than pups in naturally small litters. Pups reared by dams in a warm ambience (26°C) gained weight more slowly than dams at 22°C, and maternal food intake but not weight gain was depressed in the high ambient temperature. Pup growth at 18°C was unimpaired, with those dams eating no more and gaining no less weight than dams at 22°C. Nest material, however, was found to be essential for the successful rearing of young at cooler ambient temperatures. While restriction of food during gestation resulted in a marginally lower weight gain for the pups during the first 2 weeks postpartum, the dams appeared not to mobilize corporal stores or increase their food intake during lactation. Heavy body weight mothers did not eat any more, nor did they gain any less weight nor rear larger pups than light body weight dams. Rat mothers increased their consumption of a diet diluted with non-nutritive fiber to equal the nutritive intake of their controls, with their pups not differing in their growth rate. Pups reared by dams eating a high quality diet grew faster than pups with dams on the control diet. Food intake by mother rats is required during lactation relative to the amount of milk that is delivered to the pups, rather than to an absolute amount of food. Lactating females with a concurrent pregnancy neither increase their food intake nor appear to mobilize their corporal stores to deal with the added energetic drain of pregnancy. Indeed, their young grew somewhat more quickly than pups nursed by dams that were simply lactating. Taken as a whole, these results suggest that Norway rat dams apparently do not monitor and defend a maximal pup growth rate. Rather, rat dams seem to continue to defend their own homeostasis, and by doing so, allow the young to grow and survive under a wide variety of circumstances.     

The role of diet in mother-infant reciprocity in the spiny mouse

One-day-old spiny mouse pups responded preferentially to bedding soiled by lactating conspecifies fed the same diet as their mothers. Following this test, pups were fostered onto different-diet females. When retested at 84–96 hr of age, no preferences were shown for bedding soiled by a female fed the biological mother's diet vs bedding of a female fed the different diet. When tested again at 120–132 hr of age, however, the pups preferred the bedding associated with their foster mother's diet. In a 2nd experiment, recently parturient females retrieved 1-day-old pups born of same-diet females faster than pups born to novel-diet females. These results indicate that pup preferences for chemical cues produced by lactating conspecifics can be altered by sufficient exposure to a 2nd female maintained on a different diet and that neonatal chemical cues, like maternal chemical stimuli, are diet-dependent.     

Effect of methamphetamine exposure during prenatal and preweaning periods lasts for generations in rats

Our previous studies demonstrated that methamphetamine (MA) administration during gestation and/or lactation affects maternal behavior in rats and that birth weight and sensory-motor coordination of their pups are also influenced. The present study tested the hypothesis that the effect of MA induces long-term changes affecting second generation of rats that were not exposed to the drug. Adult females exposed during prenatal and preweaning periods to 5 mg/kg MA daily, were examined for regularity of estrous cycle and mated with stimulus, unexposed males. Dams (nontreated absolute control, saline- and MA-exposed) were observed with their pups in two tests of maternal behavior (observational and retrieval tests). Their pups were further tested throughout the preweaning period to examine their development. Our data demonstrate that MA-exposed mothers displayed more nursing, were more often in the nest and in contact with their pups, and were faster in retrieving their pups than saline-exposed and/or control mothers. There were no differences in litter characteristics, birth weight and weight gain of pups between groups. Interestingly, pups from mothers exposed to MA during prenatal and preweaning period had impaired sensory-motor coordination. They achieved righting reflex in mid-air later than both control groups. Additionally, they had more falls in rotarod and bar-holding tests than pups from both control and saline-exposed mothers. In homing performance, pups from MA- and saline-exposed dams learned slower to return to the home box than pups from control dams. Thus, the present study demonstrates that MA abused by mothers may affect two generations of their offspring.     

Factors affecting birthweight of rural Australian Aborigines

AIM: To examine factors affecting birthweight of Aboriginal infants in the Kimberley region of north-west Australia. Research design: A retrospective study of maternal and infant health records obtained through routine data collection. Subjects and methods: Birthweight and length of 2959 infants born to 1822 women from 1986 to 1994 were analysed. Mothers and infants were matched using unique identification codes. Index births and subsequent births to the same mother were collated in order to examine relative birth order effects and to calculate birth intervals. RESULTS: Regression analysis showed significant associations between weight of the index birth and maternal age (p < 0.001), remoteness of locality (p < 0.01), sex of the infant (p < 0.001) and maternal height (p < 0.001). Length at birth was significantly associated with ethnicity of infant (Aboriginal vs Aboriginal/non-Aboriginal admixture, p < 0.05), sex (p < 0.001), remoteness (p < 0.01) and maternal height (p < 0.001). Similar associations were observed for second and subsequent births. Birth interval was not associated with birthweight or length. Low birthweight was also more common to Aboriginal mothers compared with mothers of Aboriginal/non-Aboriginal admixture (13.1% vs 9.2%; chi(2) = 5.1, p < 0.025) even though there were no differences in height between these two groups. Teenage mothers (< or =19 years) were no more likely to have low birthweight babies than older mothers. Of the variables examined, the only significant predictor of low birthweight was a previous low birthweight baby (relative risk = 4.45, p < 0.001). CONCLUSIONS: Short birth intervals and teenage births were not significant contributors to low birthweight in the present study. The high prevalence and duration of breastfeeding in the Kimberley may contribute to long average birth intervals. Pre-term birth, rather than intrauterine growth retardation, is likely to be the most common cause of low birthweight in this population.     

Preobesity in the infant OLETF rat: The role of suckling

The Otsuka Long Evans Tokushima Fatty (OLETF) rat model of obesity, which lacks CCK₁ receptors, has been extensively investigated over the last decade. We have recently focused on the early developmental stages of this strain, finding that OLETF pups are heavier than controls from birth and hyperphagic already from postnatal (PN) Day 2. OLETF mothers present differential maternal behavior patterns and increased nursing time and frequency, which might contribute to the preobese characteristics of the pups. The present investigation examined the pups' ability to gain weight from the nursing episodes. First, we measured the pups' weight gain from one nursing bout from their own dam. Next we examined the pups' weight gain after a feeding competition test with control pups from foster dams of both strains. OLETF pups gained more weight than controls from their own dams on PN Week 1 due to a higher suckling rate (and/or efficacy) and on PN Week 3 due to increased nursing time. When competing with control pups, OLETF pups gained significantly more weight after the same nursing bout, regardless of the strain of the mother. Body mass index (BMI) was significantly higher in OLETF pups compared to controls. The maternal parameters assessed from the experiment were latencies to pup retrieval and to nursing, and nursing duration; differences were only observed in nursing time. OLETF dams increased their average nursing time over the PN weeks, while control dams decreased their nursing time toward weaning. The results suggest an important contribution of OLETF pups toward their own preobese development. © 2008 Wiley Periodicals, Inc. Dev Psychobiol 50: 202–202, 2008.     

Hypercholesterolaemia in pregnancy as a predictor of adverse pregnancy outcome

Background

Prevention of viable spontaneous preterm birth and low birth weight through screening is one of the key aims of antenatal care as these have implications for the child, mother and society. If women can be identified to be at high risk of these adverse birth outcomes in early pregnancy, they can be targeted for more intensive antenatal surveillance and prophylactic interventions.

Objectives

This study is therefore aimed to determine the association between elevated maternal serum cholesterol level in pregnancy and adverse pregnancy outcome.

Methods

It was a prospective observational cohort study in which eligible participants were enrolled at gestational age of 14 to 20 weeks. Blood samples were obtained to measure total serum cholesterol concentrations and the sera were then analyzed enzymatically by the cholesterol oxidase: p-aminophenazone (CHOD PAP) method. Pregnancy outcomes were obtained by extraction from medical records and the labour ward register.

Results

The incidences of the two adverse pregnancy outcomes examined in the study (preterm births and low birth weight (LBW) in term neonates) were 8.0% and 14.4% respectively. Preterm birth was 6.89-times more common in mothers with high cholesterol than in control mothers with normal total cholesterol level (38.5% versus 5.4%, P=0.029) while LBW was 7.99-times more common in mothers with high total maternal cholesterol than in mothers with normal cholesterol (87.5% versus 10.5%, P=0.019).

Conclusion

We can infer that the high maternal serum cholesterol (hypercholesterolaemia) is associated with preterm delivery/ low birth weight (LBW) in term infants. However, further validation of these findings with more robust prospective and longitudinal characterization of maternal serum cholesterol profiles is required in subsequent investigations.     

The effect of active and passive maternal smoking before and during pregnancy on neonatal weight at birth

IntroductionSmoking during pregnancy is a risk factor for adverse pregnancy outcomes. Data on the correlation between passive maternal smoking and pregnancy outcomes remain limited. We investigated the effect of active smoking and environmental tobacco smoke (ETS) during pregnancy on neonatal birthweight, including the risk for low birthweight (LBW).Material and methodsThe study was conducted between 2010 and 2012. A group of 8625 women were surveyed during postpartum hospitalization. Outcome measures included mean birthweight of newborns. Additionally, odds ratios with confidence intervals were calculated to investigate the risk for LBW in active and passive smoking groups of mothers.ResultsLower birthweight (46 g – 307 g; p < 0.05) and a higher risk for LBW (OR = 1.35, 95% CI: 1.05–1.75; p < 0.05) were observed in all infants born to smoking mothers. A negative effect of ETS in pregnancy on the reduction of mean birthweight was also found. Additionally, we analyzed the cumulative effect of active and passive smoking on neonatal birthweight. A statistically significant reduction in neonatal weight at birth was found in a group of women who smoked actively and passively during pregnancy (130 g; p < 0.05).ConclusionsSmoking is associated with decreased birthweight and in a group of active smoking mothers increased risk for LBW. This effect is dose-dependent and is also present in a group of women who smoked before pregnancy. There is also a cumulative effect of active smoking and ETS causing decreased neonatal birthweight and increased risk for low birthweight.     

Postnatal undernutrition in rats: attempts to develop alternative methods to food deprive pups without maternal behavioral alteration.

Two methods were investigated as attempts to undernourish rat pups without the disturbances in maternal behavior that accompany the procedures used to date for this purpose. In the 1st method, a litter of 12 pups was raised by both a lactating mother and a "sensitized" female. The sensitized female was provided under the assumption that she could correct for the deficit in maternal care when 1 mother raises a large litter. The results showed that the pups raised by the 2 females were constantly removed by the females from each other's nests; the females engaged in constant fighting and showed altered maternal behavior. As a consequence the pups lost more weight than control underfed young. The 2nd method consisted of removing 6-8 nipples from virgin females which were mated 10 days later. After delivery these females raised litters of 6 pups. Their maternal behavior was equal to that of unoperated controls, and at weaning the pups had 20-50% less body weight. This method could be useful to study undernutrition effects on behavior, without confounding experimental variables.     

Factors affecting birthweight of rural Australian Aborigines

Aim : To examine factors affecting birthweight of Aboriginal infants in the Kimberley region of north-west Australia. Research design : A retrospective study of maternal and infant health records obtained through routine data collection. Subjects and methods : Birthweight and length of 2959 infants born to 1822 women from 1986 to 1994 were analysed. Mothers and infants were matched using unique identification codes. Index births and subsequent births to the same mother were collated in order to examine relative birth order effects and to calculate birth intervals. Results : Regression analysis showed significant associations between weight of the index birth and maternal age ( p < 0.001), remoteness of locality ( p < 0.01), sex of the infant ( p < 0.001) and maternal height ( p < 0.001). Length at birth was significantly associated with ethnicity of infant (Aboriginal vs Aboriginal/non-Aboriginal admixture, p < 0.05), sex ( p < 0.001), remoteness ( p < 0.01) and maternal height ( p < 0.001). Similar associations were observed for second and subsequent births. Birth interval was not associated with birthweight or length. Low birthweight was also more common to Aboriginal mothers compared with mothers of Aboriginal/non-Aboriginal admixture (13.1% vs 9.2%; &#104 2 = 5.1, p < 0.025) even though there were no differences in height between these two groups. Teenage mothers ( &#114 19 years) were no more likely to have low birthweight babies than older mothers. Of the variables examined, the only significant predictor of low birthweight was a previous low birthweight baby (relative risk = 4.45, p < 0.001). Conclusions : Short birth intervals and teenage births were not significant contributors to low birthweight in the present study. The high prevalence and duration of breastfeeding in the Kimberley may contribute to long average birth intervals. Pre-term birth, rather than intrauterine growth retardation, is likely to be the most common cause of low birthweight in this population.     

Prenatal ethanol and stress in mice: 2. Development and behavior of fostered offspring

On days 12 to 17 of gestation, B6D2F2 mice were pair-fed liquid diets containing either 25% ethanol-derived calories or an isocaloric amount of maltose-dextrin. During this time, half the mice in each dietary condition also underwent two daily one-hour periods of restraint stress. All pups were fostered at birth to untreated mothers whose pups, in turn, were fostered to the treated mothers. Two additional groups of untreated dams were included, the pups in one group being fostered to other untreated dams while the rest remained with their biological mothers. Prenatal ethanol retarded neurobehavioral development on day 32 postconception and also decreased pup body weight at birth and at weaning, and brain weight on day 32 and at weaning. Prenatal stress decreased body weight at birth in the pair-fed controls only, increased open field activity at weaning and affected retention of a learned passive avoidance task. Undernutrition due to the pair feeding procedure decreased pup birth weight. There were a few effects on untreated pups fostered to treated dams, but these were marginal. These results do not support a role of stress-induced physiological changes in ethanol teratogenicity.     

Relationships between maternal behavior of SHR and WKY dams and adult blood pressures of cross-fostered F1 pups

In this experiment SHR and WKY dams reared genetically identical F1 pups derived from SHR x WKY matings. We found that a composite maternal behavior score was positively correlated with adult blood pressures of the fostered offspring. This replicated a similar finding from our previous study in which SHR and WKY mothers reared their own pups. Unlike this previous study, WKY dams rearing F1 pups exhibited maternal behavior patterns similar to SHR dams. Finally, we found there was no effect of the strain of foster mother upon adult blood pressures of the F1 offspring. These results indicate that some aspects of maternal behavior may change as a function of pup characteristics, and support our hypothesis that the cardiovascular system may be shaped by experiences of early life which are embedded in mother/young behavioral interactions.     

Postnatal undernutrition: An alternative method

Rat pups were undernourished from birth by placing them for 12 hr/day with a normal lactating mother and 12 hr/day with a nipple-ligated mother each day for 25 days. The method resulted in a marked delay in the body growth of the undernourished pups, especially during the first 2 weeks of life. Observations of the behavior of the mothers towards the underfed pups were made at different times of the day and compared to the behavior of the mothers suckling well-fed pups. The results show that (1) nipple-ligated mothers are able to provide adequate maternal care for undernourished pups, and (2) both ligated and nonligated mothers caring for underfed pups spend more time with those pups than mothers caring for well-fed pups.     

Maternal behavior of SHR rats and its relationship to offspring blood pressures

In Part I of this study maternal behavior of 15 spontaneously hypertensive (SHR) and 11 Wistar-Kyoto (WKY) rat mothers was recorded throughout the preweaning period. SHR mothers were observed: 1) in arched-and blanket-nursing postures more often, and in passive-nursing posture less often, 2) licking their pups more often, and 3) resting less often. Further, SHR mothers retrieved their pups more quickly than did WKY. In the second part of this study we found that a composite maternal behavior score, derived from summing occurrences of mother/pup contact, arched-nursing, and pup-licking, was positively correlated with the offspring blood pressures. This relationship, which accounted for 43.5% of the variance in adult blood pressure, suggests that certain types of interactions between mothers and their pups may contribute to individual differences in cardiovascular system development.     

Assessment of the perinatal effects of maternal ingestion of Ipomoea carnea in rats

It is believed that Ipomoea carnea toxicosis induces abnormal embryogenesis in livestock. Studies on rats treated with I. carnea aqueous fraction (AF) during gestation, revealed litters with decreased body weight, but the characteristic vacuolar lesions promoted by swainsonine, its main toxic principle, were observed only in young rats on postnatal day (PND) 7. However, these alterations could have resulted as consequence of swainsonine placental passage and/or damage or even ingestion of the contaminated milk by pups. Thus, this perinatal work was performed to verify the transplacental passage of swainsonine and its excretion into milk employing the cross-fostering (CF) procedure as a tool of study. Females were treated with AF or vehicle during gestation and after birth pups were fostered between treated and untreated dams. Pup body weight gain (BWG) and histopathology to observe vacuolar degeneration were performed on PND 3 and 7. In addition, swainsonine detection was performed in amniotic fluid and milk from rats treated with the AF during gestation or lactation. BWG was significantly lower only in pups from mothers treated with the plant and fostered to other treated mothers (AF–AF group of pups). The histopathology revealed that pups from treated mothers fostered to untreated ones showed the characteristic vacuolar lesions; however, the lesions from the AF–AF pups were more severe in both periods evaluated. Amniotic fluid and milk analysis revealed the presence of swainsonine excretion into these fluid compartments. Thus, the results from CF and the chemical analysis allowed concluding that swainsonine passes the placental barrier and affects fetal development and milk excretion participates in I. carnea perinatal toxicosis.