Gabriele R. Lubach

Growth and Development Following Prenatal Stress Exposure in Primates: An Examination of Ontogenetic Vulnerability

Previous studies have found that stressful events during pregnancy can influence the developing fetus, resulting in attentional and neuromotor problems. This prospective study examined whether periods of vulnerability exist for neurobehavioral impairments associated with prenatal stress, using a nonhuman primate model. Twenty-eight rhesus monkey infants were born to mothers in 3 groups: (1) early gestation stress involving mild psychological stress from gestational days 45-90, (2) mid-late gestation stress from days 90-145, and (3) undisturbed controls. Infants were separated from their mothers on days 4, 9, 15, and 22 (+/- 1) postpartum for growth and neurobehavioral assessments. Results indicated that infants from the early gestation stress condition weighed less than infants from mothers stressed during mid-late gestation. Moreover, whereas both groups scored lower than controls on measures of attention and neuromotor maturity, early gestation stress was associated with more pronounced and more pervasive motor impairments than mid-late gestation stress. These results suggest sensitivity to prenatal stress effects peaks during early gestation, tapering off during mid-late gestation. Clarifying the period of greatest vulnerability to prenatal stress moves toward elucidating the underlying mechanism for prenatal stress effects and may lead to more successful intervention and/or prevention.

Prenatal stress alters bacterial colonization of the gut in infant monkeys.

Objective: The hypothesis that prenatal stress lowers the levels of protective microflora and increases the risk for postpartum Gram-negative pathogens was tested in infant monkeys. Methods: Female monkeys were left undisturbed or were stressed during pregnancy using an acoustical startle paradigm for 6 weeks either early or late in their 24-week gestation. Several types of intestinal microflora were repeatedly enumerated by fecal culture while infants were reared normally by their mothers. Results: Significant changes in microflora concentrations occurred during the first 6 months of life. The profile of total aerobes and facultative anaerobes was biphasic, with peak concentrations occurring between 2 and 16 weeks of age. The numbers of bifidobacteria and lactobacilli were low at 2 days after birth but rapidly increased to a peak between 8 and 16 weeks of age. Although similar temporal patterns were evident in all infants, prenatal stress reduced the overall numbers of bifidobacteria and lactobacilli. Conclusions: Moderate disturbance during pregnancy was sufficient to alter the intestinal microflora in the newborn infant. These alterations could result in enhanced susceptibility to infection and suggest a mechanism for some effects of maternal pregnancy conditions on infant health.

Maternal Influenza Infection During Pregnancy Impacts Postnatal Brain Development in the Rhesus Monkey

BACKGROUND Maternal infection with influenza and other pathogens during pregnancy has been associated with increased risk for schizophrenia and neurodevelopmental disorders. In rodent studies, maternal inflammatory responses to influenza affect fetal brain development. However, to verify the relevance of these findings to humans, research is needed in a primate species with more advanced prenatal corticogenesis. METHODS Twelve pregnant rhesus monkeys were infected with influenza, A/Sydney/5/97 (H3N2), 1 month before term (early third trimester) and compared with 7 control pregnancies. Nasal swabs and blood samples confirmed viral shedding and immune activation. Structural magnetic resonance imaging was conducted at 1 year; behavioral development and cortisol reactivity were also assessed. RESULTS Maternal infections were mild and self-limiting. At birth, maternally derived influenza-specific immunoglobulin G was present in the neonate, but there was no evidence of direct viral exposure. Birth weight and gestation length were not affected, nor were infant neuromotor, behavioral, and endocrine responses. However, magnetic resonance imaging analyses revealed significant reductions in cortical gray matter in flu-exposed animals. Regional analyses indicated the largest gray matter reductions occurred bilaterally in cingulate and parietal areas; white matter was also reduced significantly in the parietal lobe. CONCLUSIONS Influenza infection during pregnancy affects neural development in the monkey, reducing gray matter throughout most of the cortex and decreasing white matter in parietal cortex. These brain alterations are likely to be permanent, given that they were still present at the monkey-equivalent of older childhood and thus might increase the likelihood of later behavioral pathology.

Prenatal origins of individual variation in behavior and immunity

The in utero environment plays a critical role in initiating the normal ontogeny of many physiological systems. As a consequence, disturbances during prenatal life can affect the babys maturational trajectory and sometimes cause chronic alterations that influence health postpartum. Our review summarizes a series of studies in rhesus monkeys supporting these conclusions. Psychological disturbance or pharmacological stimulation of the gravid females pituitary-adrenal axis affected the infants neurological development: monkeys evinced immature neuromotor reflexes at birth, greater emotionality during the first year of life, and a smaller hippocampus as juveniles. Immune responses of the infants were also affected: lymphocyte proliferation, natural killer activity and cytokine production were reduced. Several mediating pathways were implicated, including the placental transfer of hormones and nutrients, and a differential response of the infant monkey to the rearing environment. For example, the establishment of beneficial types of microflora in the gastrointestinal tract was significantly reduced, which was associated with a greater risk for enteric infection. These findings indicate that events during fetal life can persistently influence physiology after birth and tilt the balance away from health and toward illness.

Prenatal stress alters brain biogenic amine levels in primates

In this study, we assessed behavioral responses to social separation at 8 months of age and cerebrospinal fluid (CSF) concentrations of biogenic amines and metabolites at 8 and 18 months of age in 12 rhesus monkeys derived from either stressed or undisturbed pregnancies. Compared to controls from undisturbed pregnancies, prenatal stress-derived monkeys had higher concentrations of 3-methoxy-4-hydroxyphenylglycol (MHPG), and 3,4-dihydroxyphenylacetic acid in CSF than controls. Norepinephrine and MHPG response to stress were both correlated between 8 and 18 months of age. There were few group differences in behavior during social separation; however, several behavioral differences between groups were found when monkeys were reunited with cage mates. Prenatally stressed monkeys spent more time clinging to their surrogates and exploring (including eating and drinking), while controls showed more locomotion and social play with their cage mates. Collectively, our findings suggest that chronic unpredictable psychological stress during pregnancy has long-lasting effects on noradrenergic and dopaminergic activity and behavior in the offspring of gestationally stressed primate mothers.

Influence of early rearing on lymphocyte proliferation responses in juvenile rhesus monkeys.

Lymphocyte proliferation responses and natural killer cell activity were evaluated in 35 juvenile rhesus monkeys derived from five different rearing conditions. Nursery-reared monkeys had proliferation responses which were significantly higher than those of mother-reared subjects. Reexamination of the nursery-reared monkeys 1.5 years later indicated that an abnormally high response to concanavalin A was still evident at 2.5 years of age, but both PHA and PWM responses had shown an age-appropriate decrease into the normal range for this species. Proliferation responses in monkeys that had been weaned early from their mothers at 6 months of age were also higher than values for control monkeys that remained with their mothers, but below those of the nursery-reared monkeys. In contrast, monkeys that had received multiple separations from the mother between 3 and 7 months of age showed lymphocyte proliferation responses that were below normal. These results indicate that early rearing conditions can have a lasting effect on certain immune responses in the developing primate.

Prenatal Endocrine Activation Alters Postnatal Cellular Immunity in Infant Monkeys

Cellular immune responses were evaluated in 35 infant rhesus monkeys generated from two types of pregnancy conditions. Pregnant females were administered either saline or adrenocorticotropic hormone (ACTH) for 2 weeks between Days 120 and 133 postconception, approximately 1 month before parturition. After birth, lymphocytes obtained from infants in the ACTH condition failed to respond as readily to allogeneic cells in mixed lymphocyte cultures, proliferated less to Con A, exhibited lower suppressor function following stimulation with Con A, and showed lower cytolytic activity against target cells. For some measures, the prenatal effect was observed more consistently in male infants. Differences were evident with these in vitro immune assays through 6 months of age, indicating that acute disturbance during the prenatal period can have lingering effects on postnatal immunity.

Maturational Trajectories of Cortical Brain Development through the Pubertal Transition: Unique Species and Sex Differences in the Monkey Revealed through Structural Magnetic Resonance Imaging

Characterizing normal brain development in the rhesus macaque is a necessary prerequisite for establishing better nonhuman primate models of neuropathology. Structural magnetic resonance imaging scans were obtained on 37 rhesus monkeys (20 Male, 17 Female) between 10 and 64 months of age. Effects of age and sex were analyzed with a cross-sectional design. Gray matter (GM) and white matter (WM) volumes were determined for total brain and major cortical regions using an automatic segmentation and parcellation pipeline. Volumes of major subcortical structures were evaluated. Unlike neural maturation in humans, GM volumes did not show a postpubertal decline in most cortical regions, with the notable exception of the prefrontal cortex. Similar to humans, WM volumes increased through puberty with less change thereafter. Caudate, putamen, amygdala, and hippocampus increased linearly as did the corpus callosum. Males and females showed similar maturational patterns, although males had significantly larger brain volumes. Females had a proportionately larger caudate, putamen, and hippocampus, whereas males had both an absolute and relatively larger corpus callosum. The authors discuss the possible implications of these findings for research using the rhesus macaque as a model for neurodevelopmental disorders.

Moderate Alcohol Consumption and Psychological Stress during Pregnancy Induce Attention and Neuromotor Impairments in Primate Infants

This study examined the effect of moderate alcohol and/or psychological stress during prenancy on off-spring growth and behavior in 33 rhesus monkey infants (Macaca mulatta). Infants were derived from 1 of 3 groups of female: (1) alcohol-consuming,0.6g/Kg, Daily throughou gestation (equivalet, to 1-2 drinks), beginning 5 day prior to breeding;(2) alcohol-consuming (as above) and exposed to mild psychological stress(removal from home cage and exposed to 3 random noise bursts); (3) sucrose-consuming, equivolemic, and equicaloric to the alcohol solution.Beginning on day 4 postpartum, intantrs underwent brief weekly separations from their mother for assessment of growth, behavior, and facial dimensions. Results indicated that moderate alcohol consumption throughout pregnancy was sufficient to affect attention and neuromotor functioning, even though the infants were normol in birthweight, gestational length, and facial dimensions, Moreover, alcohol-induced neuromotor impairments were exacerbated by maternal exposure to psychological stress, and males from the alcohol/stress condition had reduced birthweights. Finally, although all females consuming alcohol produced viable offspring, alcohol accompanie by stress during gestation resulted in 23% fetal losses (abortion and stillbirths).

Developmental consequences of antenatal dexamethasone treatment in nonhuman primates

Research assessing fetal exposure to dexamethasone and betamethasone in animals has raised concerns about the potential for adverse side effects following antenatal treatments, not withstanding the beneficial and desired improvement in lung function. Some of the inhibitory effects on physical growth and the long-term alterations in endocrine, immune and neural physiology may reflect species differences in the fetal sensitivity of rodents and monkeys to corticosteroids or perhaps could be attributed to the higher drug doses often used in animal studies. However, since steroidal drugs can be administered for extended periods in clinical practice, and also are occasionally given in the range found to cause significant effects on the brain and immune responses of infant monkeys, the simian studies have important cautionary implications for obstetrical and pediatric practice.