Influence Of Maternal Environment Research Articles

Bayesian analysis reveals the influence of maternal effect on pre-weaning body weights in Landlly piglets.

The present study was undertaken to estimate the (co)variance components and genetic parameters of body weights recorded in Landlly piglets from birth to weaning at weekly intervals (w0 to w6). The data pertained to body weights of 2462 piglets, born to 91 sires and 159 dams across different generations during a 7-year period from 2014 to 2020. Five animal models (I-V), differentiated by inclusion or exclusion of maternal effects with or without covariance between maternal and direct genetic effects, were fitted on the data using the Bayesian algorithm. The analyses were implemented by Gibbs sampling in the BLUPF90 program and Markov chain Monte Carlo (MCMC) methodology was used to draw samples of posterior distribution pertaining to (co)variance components. Based on deviance information criteria (DIC), model V with inclusion of direct additive genetic, direct maternal genetic and permanent environmental effect of dam as random factors along with covariance between direct additive and maternal effects best fitted the data on pre-weaning traits (w0 to w5). Whereas, model I incorporating only the direct additive genetic effect best fitted the weaning weight (w6) data in Landlly piglets. The posterior mean estimates of direct heritability under the best models for W0 to W6 were 0.13, 0.19, 0.29, 0.13, 0.26, 0.32 and 0.46, respectively. Inclusion of the maternal component helped in better partitioning of variance for different body weights in Landlly piglets. The maternal heritability ranged from 0.06 to 0.14, while the litter heritability ranged from 0.11 to 0.15 for pre-weaning weights (W0 to W5) under the best-fit models. The influence of maternal environment was greater than maternal genetic effect from birth to 4th week of age. The results implied that variations in body weight of Landlly pigs were genetically controlled to moderate levels (especially w2 and w4) with contributions from direct additive and maternal genotype that can be exploited by designing efficient breeding programmes.

Who listens to mother? A whole-family perspective on the evolution of maternal hormone allocation.

ABSTRACTMaternal effects, or the influence of maternal environment and phenotype on offspring phenotype, may allow mothers to fine‐tune their offspring's developmental trajectory and resulting phenotype sometimes long after the offspring has reached independence. However, maternal effects on offspring phenotype do not evolve in isolation, but rather within the context of a family unit, where the separate and often conflicting evolutionary interests of mothers, fathers and offspring are all at play. While intrafamilial conflicts are routinely invoked to explain other components of reproductive strategy, remarkably little is known about how intrafamilial conflicts influence maternal effects. We argue that much of the considerable variation in the relationship between maternally derived hormones, nutrients and other compounds and the resulting offspring phenotype might be explained by the presence of conflicting selection pressures on different family members. In this review, we examine the existing literature on maternal hormone allocation as a case study for maternal effects more broadly, and explore new hypotheses that arise when we consider current findings within a framework that explicitly incorporates the different evolutionary interests of the mother, her offspring and other family members. Specifically, we hypothesise that the relationship between maternal hormone allocation and offspring phenotype depends on a mother's ability to manipulate the signals she sends to offspring, the ability of family members to be plastic in their response to those signals and the capacity for the phenotypes and strategies of various family members to interact and influence one another on both behavioural and evolutionary timescales. We also provide suggestions for experimental, comparative and theoretical work that may be instrumental in testing these hypotheses. In particular, we highlight that manipulating the level of information available to different family members may reveal important insights into when and to what extent maternal hormones influence offspring development. We conclude that the evolution of maternal hormone allocation is likely to be shaped by the conflicting fitness optima of mothers, fathers and offspring, and that the outcome of this conflict depends on the relative balance of power between family members. Extending our hypotheses to incorporate interactions between family members, as well as more complex social groups and a wider range of taxa, may provide exciting new developments in the fields of endocrinology and maternal effects.

Influence of maternal environment in developing different levels of physical dormancy and its ecological significance

There is considerable literature on the ecology of seeds with impermeable coats, i.e., physical dormancy (PY), but the factors controlling the development of PY and their ecological importance have received little study. The differences in relative humidity, temperature, and rainfall of the maternal environment during seed development, which vary within year at different sites or between years within the same site, contribute to the number and level of PY are reviewed. These factors all influence the development of PY by lowering the level of moisture content in the seeds. Based on moisture content reached during maturation drying, two levels of PY can be recognized: (1) shallow and (2) absolute. Seeds with shallow PY are shed at higher water content, while seeds with absolute PY have lower moisture content at the time of shedding. However, if the moisture content maintained is higher than the ‘shallow dormant’ level, the seed coat remains permeable to water. It is suggested that this variation in the level of PY subsequently affects the dormancy loss mechanisms and determines the ability of seeds to establish a long-term persistent seed bank or germinate within few years of shedding.

Genetic parameters and non-genetic influences related to birth weight in farmed white-tailed deer

SUMMARYStudying and understanding the sources of variation in early life traits in farmed deer are fundamental for management and/or breeding purposes. Data from a captive white-tailed deer population were analysed to identify non-genetic and genetic factors affecting the birth weight (BW) of fawns. The year, type of birth and sex were included in a fixed linear model to examine their significance. All of the examined non-genetic factors had a highly significant effect on BW (P<0·001). The examined years showed variation attributed to food availability affecting the gestational conditions of does. Male fawns were 193 g heavier than female fawns at birth (P<0·001), and singleton births were associated with a higher BW (2·97±0·043 kg) compared with twin (−0·261 g) and triplet (−0·642 g) fawning (P<0·001). The best-fitting animal model was selected by comparing reduced and complete models. Based on the selected animal model, which included direct genetic and common maternal effects, genetic components and parameters were estimated. The direct heritability was found to be 0·28±0·126, and a small but important contribution of common maternal environmental effects was identified (c2=0·15±0·062). The results support the importance of certain environmental factors affecting BW and indicate the relevance of direct genetic and maternal environmental influences to sustained genetic changes in BW and positively correlated traits in farmed white-tailed deer populations.

Environmental maternal effects mediate the resistance of maritime pine to biotic stress.

The resistance to abiotic stress is increasingly recognised as being impacted by maternal effects, given that environmental conditions experienced by parent (mother) trees affect stress tolerance in offspring. We hypothesised that abiotic environmental maternal effects may also mediate the resistance of trees to biotic stress. The influence of maternal environment and maternal genotype and the interaction of these two factors on early resistance of Pinus pinaster half-sibs to the Fusarium circinatum pathogen was studied using 10 mother genotypes clonally replicated in two contrasting environments. Necrosis length of infected seedlings was 16% shorter in seedlings grown from favourable maternal environment seeds than in seedlings grown from unfavourable maternal environment seeds. Damage caused by F. circinatum was mediated by maternal environment and maternal genotype, but not by seed mass. Mechanisms unrelated to seed provisioning, perhaps of epigenetic nature, were probably involved in the transgenerational plasticity of P. pinaster, mediating its resistance to biotic stress. Our findings suggest that the transgenerational resistance of pines due to an abiotic stress may interact with the defensive response of pines to a biotic stress.

Prenatal androgen excess programs metabolic derangements in pubertal female rats

Owing to the heterogeneity in the clinical symptoms of polycystic ovary syndrome (PCOS), the early pathophysiological mechanisms of PCOS remain unclear. Clinical, experimental, and genetic evidence supports an interaction between genetic susceptibility and the influence of maternal environment in the pathogenesis of PCOS. To determine whether prenatal androgen exposure induced PCOS-related metabolic derangements during pubertal development, we administrated 5α-dihydrotestosterone (DHT) in pregnant rats and observed their female offspring from postnatal 4 to 8 weeks. The prenatally androgenized (PNA) rats exhibited more numerous total follicles, cystic follicles, and atretic follicles than the controls. Fasting glucose, insulin, leptin levels, and homeostatic model assessment for insulin resistance were elevated in the PNA rats at the age of 5-8 weeks. Following intraperitoneal glucose tolerance tests, glucose and insulin levels did not differ between two groups; however, the PNA rats showed significantly higher 30- and 60-min glucose levels than the controls after insulin stimulation during 5-8 weeks. In addition, prenatal DHT treatment significantly decreased insulin-stimulated phosphorylation of AKT in the skeletal muscles of 6-week-old PNA rats. The abundance of IR substrate 1 (IRS1) and IRS2 was decreased in the skeletal muscles and liver after stimulation with insulin in the PNA group, whereas phosphorylation of insulin-signaling proteins was unaltered in the adipose tissue. These findings validate the contribution of prenatal androgen excess to metabolic derangements in pubertal female rats, and the impaired insulin signaling through IRS and AKT may result in the peripheral insulin resistance during pubertal development.

Relationship of folate, vitamin B12 and methylation of insulin-like growth factor-II in maternal and cord blood

Background/ObjectiveOne of the speculated mechanisms underlying fetal origin hypothesis of breast cancer is the possible influence of maternal environment on epigenetic regulation, such as changes in DNA methylation of the insulin-like growth factor-2 (IGF2) gene. The aim of the study is to investigate the relationship between folate, vitamin B12 and methylation of the IGF2 gene in maternal and cord blood.Subjects/MethodsWe conducted a cross-sectional study to measure methylation patterns of IGF2 in promoters 2 (P2) and 3 (P3).ResultsThe percentage of methylation in IGF2 P3 was higher in maternal blood than in cord blood (p<0.0001), while the methylation in P2 was higher in cord blood than in maternal blood (p=0.016). P3 methylation was correlated between maternal and cord blood (p<0.0001) but not P2 (p=0.06). The multivariate linear regression model showed that methylation patterns of both promoters in cord blood were not associated with serum folate levels in either cord or maternal blood, while the P3 methylation patterns were associated with serum levels of vitamin B12 in mother’s blood (MC=−0.22, p=0.0014). Methylation patterns in P2 of maternal blood were associated with serum levels of vitamin B12 in mother’s blood (MC=−0.23, p=0.012), exposure to passive smoking (MC=0.46, p=0.034) and mother’s weight gain during pregnancy (MC=0.23, p=0.019).ConclusionsThe study suggests that environment influences methylation patterns in maternal blood, and then the maternal patterns influence the methylation status and levels of folate and vitamin B12 in cord blood.

6th World Congress on Developmental Origins of Health and Disease

Objective: While genomic variation explains only a modest proportion of the risk of cardiovascular and metabolic disease, animal models demonstrate that maternal environmental influences alter epigenetic processes in the offspring, with important effects on their later body composition and cardiometabolic function. Whether such processes operate in humans has not been examined. Methods: Using DNA extracted from stored umbilical cord tissue from healthy neonates who were subsequently extensively phenotyped, we related the DNA methylation status of specific CpGs 5’ from candidate genes to body composition measured by DXA scanning at age 9 years. Appropriate institutional ethics committee clearance and participants’ informed consent were obtained. Results: Methylation, measured by the Sequenom MassARRAY system, varied greatly at particular CpG sites. Of 68 CpGs studied, 31 had a median methylation >5% and a 5-95% range >10%. Independently of sex, there were strong correlations of the degree of methylation in specific CpGs in eNOS with childhood fat mass (Pearson correlation rp 50.42, n566) and trunk/limb fat ratio (rp 50.33, n566), and in RXRA methylation with fat mass and percentage fat mass (rp 50.32 and 0.29, respectively, n564) (all p,0.005, taking account of methylation at other CpG sites). Methylation at these sites was not linked to birth weight. Controlling for sex, perinatal epigenetic marks explained more than 40% of the variance in body composition at age 9 years. Conclusions: Epigenetic marks at birth predict a significant proportion of the variance in later childhood adiposity, indicating that substantial components of later metabolic disease risk are induced before birth. Perinatal epigenetic analysis may have utility in identifying individual vulnerability to later chronic non-communicable disease. MAH and JSJ are supported by the British Heart Foundation. PDG and AS are funded by the National Research Centre for Growth and Development (New Zealand). BSE is supported by the Agency for Science, Technology and Research (Singapore). This work was supported by the charity WellChild (previously Children Nationwide), by the University of Southampton, by the UK Medical Research Council and the EpiGen consortium.

Immediate and delayed life-history responses of Daphnia ambigua to conspecific cues

Studies of planktonic organisms have shown that various life-history traits, and consequently population growth rate, can be affected by chemical cues released by high densities of conspecifics. In this work we test for potential delays in population responses to conspecific cues in the cladoceran Daphnia ambigua through: (i) evaluating the influence of maternal environment on life-history traits of their daughters, and (ii) identifying the developmental stages that need to be exposed to conspecific cues to observe significant changes in life-history attributes. Our results revealed that exposure to conspecific cues decreased population growth rate of D. ambigua, mainly due to reduced offspring number and delayed maturation. Growth rate reduction was also dependent on the mother’s environment, and interaction effects arose between current generation and past-generation environments. The observed variations in maturity and fertility were triggered by exposure to conspecific cues during early development. We hypothesize that conspecific cues are able to induce delayed life-history effects and therefore delayed density dependence at the population level.

School-Age Children With Diabetes

The purpose of this study was to examine the relationships between maternal environment (child behavior and coping resources), diabetes self-efficacy, diabetes management behaviors, and child glycemic control. Study participants were recruited from 3 outpatient clinics in the Midwest and included 41 mothers of children with type 1 diabetes, ages 6 to 10. All participants completed the following measures: Coping Resources Inventory, Behavioral Assessment System for Children-Parent Report, Maternal Self-Efficacy for Diabetes Scale, Diabetes Management Scale-Parent, and 24-hour diabetes behavior recall. Downloaded glucose data and child HgbA1c were obtained by chart review. Stepwise multiple regression was used to determine the influence of maternal environment on maternal diabetes self-efficacy and diabetes management behavior. Pearson product moment correlations were used to determine if relationships existed between maternal self-efficacy, diabetes management behaviors, and child metabolic control. Coping resources contributed significantly to mothers' diabetes self-efficacy. No significant relationship was found between the mothers' environment and diabetes management behavior. Self-efficacy did not predict maternal diabetes management behaviors. The blood glucose testing and maternal recall of diabetes behaviors were correlated to metabolic control. Mothers with coping resources felt more confident in managing their children's diabetes. Child behavior did not influence a mother's diabetes management behaviors. Mothers who were consistent in their diabetes management behaviors had children in better metabolic control. More information is needed to determine what mothers view as barriers in providing diabetes care for their children.

Maternal Environment Alters Social Interactive Traits But Not Open-Field Behavior in Fischer 344 Rats

Although it is recognized that the genetic background governs behavioral phenotypes, environmental factors also play a critical role in the development of various behavioral processes. The maternal environment has a major impact on pups, and the cross-fostering procedure is used to determine the influence of early life experiences. The present study examined the influence of maternal environment on behavioral traits in inbred Fischer 344 (F344) rats. F344/DuCrlCrlj and Wistar (Crlj:WI) pups were fostered from postnatal day 1 as follows: Wistar pups raised by Wistar dams, F344 raised by Wistar, Wistar raised by F344, and F344 raised by F344. At 10 weeks of age, rats were randomly assigned to an open-field test and social interaction test. In the open-field test, irrespective of the rearing conditions, the activity during the first 1 min was significantly lower in F344 rats than in Wistar rats. Latency to the onset of movement showed no difference between groups. In the social interaction test, the recognition performance during the first 1 min in F344 raised by F344 was significantly shorter than that in the other groups. The onset of recognition to a novel social partner in F344 raised by F344 was significantly delayed, and the delay disappeared upon cross-fostering by Wistar dams. These results raise the possibility that the behavioral phenotype of F344 rats results from the interplay of genetic factors and maternal environment during early life, and that F344 rats are a strain with high susceptibility to rearing conditions for the formation of their emotionality.

Maternal Enrichment during Pregnancy Accelerates Retinal Development of the Fetus

The influence of maternal environment on fetal development is largely unexplored, the available evidence concerns only the deleterious effects elicited by prenatal stress. Here we investigated the influence of prenatal enrichment on the early development of the visual system in the fetus. We studied the anatomical development of the rat retina, by analyzing the migration of neural progenitors and the process of retinal ganglion cell death, which exerts a key role in sculpturing the developing retinal system at perinatal ages. The number of apoptotic cells in the retinal ganglion cell layer was analyzed using two distinct methods: the presence of pyknotic nuclei stained for cresyl violet and the appearance of DNA fragmentation (Tunel method). We report that environmental enrichment of the mother during pregnancy affects the structural maturation of the retina, accelerating the migration of neural progenitors and the dynamics of natural cell death. These effects seem to be under the control of insulin-like growth factor-I: its levels, higher in enriched pregnant rats and in their milk, are increased also in their offspring, its neutralization abolishes the action of maternal enrichment on retinal development and chronic insulin-like growth factor-I injection to standard-reared females mimics the effects of enrichment in the fetuses. Thus, the development of the visual system is sensitive to environmental stimulation during prenatal life. These findings could have a bearing in orienting clinical research in the field of prenatal therapy.

Genetics of Dermatoglyphic Asymmetry in Vaidyas of West Bengal, India

In this study of the genetics of dermatoglyphic asymmetry, we collected bilateral finger and palm prints of 824 individuals from 200 families including 2 generations from an endogamous caste (Vaidya) in Barasat, North 24-Parganas District, West Bengal. Two main types of asymmetry (fluctuating asymmetry and directional asymmetry) were calculated between the two hands. The study includes familial correlation between first-degree relatives, principal-components analysis, and maximum-likelihood-based heritabilities (by pedigree analysis). We found, first, that familial correlations in all possible pairs of relationships (except spouse correlation) were weak but positive; some were even statistically significant. No indication of assortative mating was observed, but the influence of maternal environment could not be discarded. The results also showed that X-chromosome linkage does not seem to be involved. A second major finding is that five principal factors could be extracted from all these asymmetric traits, explaining 74.207% of the overall cumulative variance. Asymmetry of finger and palmar areas were clearly separated by factor. In addition, the heritabilities of the extracted five factors were in the range of 8-24%. These estimates are in agreement with some previously published data. The heritabilities of the factors describing palmar asymmetry are slightly lower than those describing finger asymmetry. The present results support the hypothesis that both types of asymmetry have a genetic basis and are influenced by the intrauterine environment.

Genetic contributions to social impulsivity and aggressiveness in vervet monkeys

Background Impulsivity contributes to multiple psychiatric disorders and sociobehavioral problems, and the more serious consequences of impulsivity are typically manifest in social situations. This study assessed the genetic contribution to impulsivity and aggressiveness in a social context using a nonhuman primate model. Methods Subjects were 352 adolescent and adult vervet monkeys from an extended multigenerational pedigree. Behavior was assessed in the Intruder Challenge Test, a standardized test that measures impulsivity and aggressiveness toward a stranger. Genetic and maternal contributions to variation in the Social Impulsivity Index and its two subscales, impulsive approach and aggression, were estimated using variance components analyses. Results The results found significant genetic contributions to social impulsivity (h 2 = .35 ± .11) and to each of the subscales, with no significant influence of maternal environment. There was a high genetic correlation between the impulsive approach and aggression subscales (rho = .78 ± .12). Conclusions This is the first study to demonstrate heritability of social impulsivity in adolescents and adults for any nonhuman primate species. The high genetic correlation suggests the same genes may influence variation in both impulsive approach and aggression. These results provide a promising basis for identification of susceptibility loci for impulsivity and aggressiveness.

Unopposed orexic pathways in the developing fetus

Fetal swallowing has important roles in fetal gastrointestinal development, and perhaps fetal somatic growth and maturation. Ingestive behavioral responses must develop in utero to provide for acquisition of water and food intake during the neonatal period. At birth, the rat, ovine and human fetus have developed mechanisms to acquire food via intact mechanisms of taste, suckling and swallowing. Our preliminary studies suggest that in sheep and likely in human fetuses, putative orexic-mediated ingestive responses are present near term gestation. We hypothesize that both orexic (appetite) and satiety mechanisms develop during the last third of gestation and the related neurotransmitters involved in this process are functional. The potential in utero imprinting of orexic mechanisms may influence infant, childhood and ultimately adult appetite “set-points”. Thus, dysfunctional appetite, and perhaps obesity, may result from maternal environmental influences during critical stages of development.

Influence of maternal environment on the number of transferable embryos obtained in response to superovulatory FSH treatments in ewes.

In a first experiment, embryo viability was estimated after recovery in the uterus or the oviduct of 70 Manchega ewes following a treatment of superovulation with decreasing doses of OVAGEN. Fewer viable embryos (5.6 +/- 0.9 vs. 8.3 +/- 0.8, P < 0.05) and more degenerative embryos (31.3% vs. 6.8%, P < 0.005) were obtained from the uterus than from the oviduct respectively. In a second experiment performed on 14 ewes, embryo viability was analyzed in relation to the follicular population estimated by ultrasonography (follicles > or = 2 mm) at the first FSH administration. Progesterone (P4) and oestradiol 17beta (E2) concentrations were also determined from the beginning of the superovulation treatment to the recovery of the embryos. The number of viable embryos (4.3 +/- 1.4) was positively correlated (r = 0.824) with of 2-4 mm diameter follicles (P < 0.05), and with E2 concentrations at -12 h (r = 0.891, P < 0.01) , 0 h (r = 0.943, P < 0.0001) and +24 h (r = 0.948, P < 0.05) from estrus detection. Prolonged high levels of E2 up to 72 h with low levels of P4 on days 3 and 4 after estrus had a negative (P < 0.05) effect on embryo viability. These results indicate that ovarian response to superovulatory protocols is related to the individual variations in the number of follicles of 2-4 mm at the start of FSH treatment, and that embryo viability is conditioned by the steroid patterns during the time spent in the genital tract of the super-ovulated ewes.

Effects of selection for production and maternal diet on maiden dairy heifer fertility

AbstractThe objectives of this study were to investigate reproductive performance and the influence of maternal environment on reproductive performance in two genetic lines of maiden heifers. These were given food and managed in the same way at the Langhill Dairy Cattle Research Centre. The two genetic lines were established in 1973; one has been selected for high combined yield of fat plus protein (selection line; S) and the other has been maintained at around the UK average for genetic merit of yield of fat plus protein (control line; C). Analysis of the reproductive performance of 988 heifers born between 1981 and 1998 showed that S heifers were poorer (all P &lt; 0·05) than C heifers for all reproductive measures: conception at first service (S: 0·64, s.e. 0·02; C: 0·71, s.e. 0·03), interval between first and last service (S: 18·2 days, s.e. 2·2; C: 13·4 days, s.e. 2·2) and number of services per conception (S: 1·49 services, s.e. 0·06; C: 1·39 services, s.e. 0·06). S heifers were also younger at first service than C heifers (474·9 days v. 480·1 days, s.e. 1·9, for S and C respectively; P • 01). Fertility of service sires may have had some influence on these results, but this could not be investigated here, as S heifers were mated only to high merit bulls and C heifers to average merit bulls. However, within genetic line, the yearly downward trend in the average number of services per conception of heifers was significantly different from zero for the S line, but not the C line. There were no statistically significant relationships between conception rates in maiden heifers and their subsequent reproductive performance in first lactation. The effect of maternal environment on the reproductive performance of daughters as maiden heifers was investigated. There were no statistically significant relationships between daughter reproductive performance and dam parity or the feeding system of the dam (either a high or low level of concentrates). Within the limited range of nutritional status of dams during the periods post calving and in early pregnancy, there was no statistically significant effect of maternal nutrition on daughter reproductive performance.

Timing of preweanling maternal effects on development of hypertension in SHR rats

Cross-fostering of litters was used to determine the timing of preweanling maternal influences on the development of high blood pressure in spontaneously hypertensive (SHR) rats. The SHR litters were either reared by their natural mothers or reciprocally cross-fostered to normotensive Wistar-Kyoto (WKY) mothers for postnatal days 1–7, 1–14, 1–21, 8–21, or 15–21. All SHR litters were weaned at 21 days of age and males were housed in groups of two to three per cage until physiological measures were obtained at 100 days of age. At 100 days of age, all rats were surgically prepared with tail artery catheters and, on the day after surgery, direct measures of mean arterial pressure (MAP, mmHg) and heart rate (HR, bpm) were obtained while rats were resting and undisturbed in their individual home cages. Our findings indicate that cross-fostering SHR pups to WKY foster mothers was attended by significant effects on body weights at weaning and on adult MAPs. Compared to control SHRs, cross-fostered SHRs, with the exception of the 15–21-day group, were significantly heavier at weaning. By 100 days of age, body weights of SHRs were similar across treatment groups. Basal MAPs of SHRs cross-fostered for days 1–7, 1–14, 1–21, and 8–21, but not days 15–21, were reduced significantly compared to SHR controls reared by their natural mothers. In contrast, basal HRs were not affected in any of the cross-fostered SHR groups. These data indicate that maternal environmental influences on the development of high blood pressure in SHRs are limited to the first 2 weeks of postnatal life. This corresponds to the time prior to weaning when rat pups receive all of their nourishment from their mothers.

Maternal Environment Effects on Plant Growth and Germination of Two Strains of Thlaspi arvense L.

The influence of maternal environment on plant development and seed germination of early- and late-flowering strains of Thlaspi arvense L. was studied. Compared to plants grown at 30^⚬/10^⚬C, those grown at 15^⚬/10^⚬C and 20^⚬/10^⚬C flowered more slowly, were shorter, and grew fewer leaves; seed production, however, was greatest at 20^⚬/10^⚬C. Plants of the late-flowering strain produced more leaves than those of the early-flowering strain, but there were no differences between strains in vegetative dry weight or height at harvest. On average, fresh seeds from plants of the late-flowering strain germinated at a faster rate than those from plants of the early-flowering strain. Seed dormancy increased with increasing temperature in which they developed, thus explaining some of the differences reported in the literature regarding germination of fresh seeds of T. arvense. The evolutionary implications of these results are discussed in relation to the single gene differences between the two strains.

Shared maternal influences in the development of high blood pressure in the spontaneously hypertensive (SHR) and Dahl salt-sensitive (SS/Jr) rat strains

The influence of maternal environment on the development of high blood pressure in spontaneously hypertensive (SHR) and Dahl salt-sensitive (SS/Jr) rats was examined using the technique of reciprocal cross-fostering. Previous experiments from this laboratory demonstrated that adult blood pressures of the SHR and SS/Jr strains were significantly attenuated when hypertensive-strain pups were fostered to a dam of the respective normotensive control strain during the preweaning period. In this study, SHR and SS/Jr pups were assigned to either a cross-fostered (fostered to a dam of the opposite hypertensive strain) or control-reared condition within 24 h of birth. Adult resting blood pressures were similar in control and cross-fostered SHR rats and in control and cross-fostered SS/Jr rats. Heart rates and heart, adrenal, and kidney weights were also similar in control and cross-fostered rats of each strain. However, body weights of SHR rats reared by an SS/Jr dam were somewhat lower compared to control-reared SHR rats. These data indicate that the maternal environments provided by SHR and SS/Jr mothers are similar in some way such that they permit the development and full expression of the hypertensive phenotype in both same-strain and opposite-strain pups.