Behavioral consequences of ovarian atrophy and estrogen replacement in the APPswe mouse.

Cognitive performance was evaluated in a longitudinal study of APPswe2576 transgenic mice (APP) and a wildtype (WT) comparison group. Subgroups of the APP mice were treated with the ovarian toxicant 4-vinylcyclo-hexene diepoxide (VCD) at 60-75 days of age to induce ovarian atrophy and/or given estrogen (estradiol, 4 microg/day) continuously by pellet from 76 days of age. APP mice had a generally poorer radial maze performance than WT at 4.5, 7.5, 10.5 and 15 months of age. In separate tests, APP mice had a slight motor impairment, higher incidence of homecage stereotypy, hyperactivity in an open field and reduced object exploration relative to the WT group. Ovarian atrophy led to better maze performance at 7.5 months. The effect of estrogen on maze performance with aging could not be effectively evaluated due to poor survival (30%) of these mice. No effects of ovarian atrophy or estrogen treatment were identified for amyloid-beta accumulation or plaque formation at 15 months. Long-term longitudinal studies in animal models are needed to explore the consequences of menopause and hormone replacement on Alzheimer's disease, but they are complicated by considerations of survival, pre-aging deficits, testing experience and selection of appropriate estrogen treatment levels.

Iron deprivation during fetal development changes the behavior of juvenile rhesus monkeys.

Sensitive periods for induction of behavioral impairments by developmental iron deficiency were studied in a nonhuman primate model. Rhesus monkey infants were deprived of iron prenatally (n = 14) via the dam's diet (10 microg Fe/g) or postnatally (birth-4 mo, n = 12) via infant formula (1.5 mg Fe/L). They were compared with controls (n = 12) with adequate dietary iron throughout development in a series of cognitive tests and related assessments from 6 to 12 mo of age, a developmental stage corresponding approximately to 2-4 y of age in humans. Health, growth, and hematological status were not affected. Auditory brainstem response and white matter volumes in the cerebrum were similarly unaffected. Male infants in the prenatally deprived group had reduced spontaneous daytime activity relative to controls, as monitored by actimeter. On cognitive tests, prenatally deprived juveniles had similar level of correct responding, but showed more completed trials, and shorter latencies during early phases of the tests. Juveniles deprived of iron as infants showed a similar pattern of behavioral change, but most differences from controls were not as great. Inadequate iron nutrition during pregnancy was reflected in the juvenile period primarily as attenuated inhibitory response. This finding may be relevant to individual differences in temperament or to behavior disorders in children involving reduced inhibitory control.

Diet-induced iron deficiency anemia and pregnancy outcome in rhesus monkeys.

BACKGROUND: Iron deficiency anemia (IDA) is relatively common in the third trimester of pregnancy, but causal associations with low birth weight and compromised neonatal iron status are difficult to establish in human populations. OBJECTIVE: The objective was to determine the effects of diet-induced IDA on intrauterine growth and neonatal iron status in an appropriate animal model for third-trimester IDA in women. DESIGN: Hematologic and iron-status measures, pregnancy outcomes, and fetal and neonatal evaluations were compared between pregnant rhesus monkeys (n = 14) fed a diet containing 10 microg Fe/g diet from the time of pregnancy detection (gestation days 28-30) and controls (n = 24) fed 100 microg Fe/g diet. RESULTS: By the third trimester, 79% of the iron-deprived dams and 29% of the control monkeys had a hemoglobin concentration <11 g/dL. There were also significant group differences in hematocrit, mean corpuscular volume, transferrin saturation, serum ferritin, and serum iron. At birth, the newborns of monkeys iron-deprived during pregnancy had significantly lower hemoglobin, mean corpuscular volume, and mean corpuscular hemoglobin values and a lower ratio of erythroid to total colony-forming units in bone marrow than did the control newborns. Pregnancy weight gain did not differ significantly between the iron-deprived and control dams, and the fetuses and newborns of the iron-deprived dams were not growth retarded relative to the controls. Gestation length, the number of stillbirths, and neonatal neurobehavioral test scores did not differ significantly by diet group. CONCLUSION: These data indicate that an inadequate intake of iron from the diet during pregnancy in rhesus monkeys can lead to compromised hematologic status of the neonate without indications of growth retardation or impaired neurologic function at birth.

Behavioral consequences of developmental iron deficiency in infant rhesus monkeys.

Human studies have shown that iron deficiency and iron deficiency anemia in infants are associated with behavioral impairment, but the periods of brain development most susceptible to iron deficiency have not been established. In the present study, rhesus monkeys were deprived of iron by dietary iron restriction during prenatal (n=14, 10 microg Fe/g diet) or early postnatal (n=12, 1.5 mg Fe/L formula) brain development and compared to controls (n=12, 100 microg Fe/g diet, 12 mg Fe/L formula) in behavioral evaluations conducted during the first four months of life in the nonhuman primate nursery. Iron deficiency anemia was detected in the pregnant dams in the third trimester and compromised iron status was seen in the prenatally iron-deprived infants at birth, but no iron deficiency was seen in either the prenatally or postnatally iron-deprived infants during the period of behavioral evaluation. Neither prenatal nor postnatal iron deprivation led to significant delays in growth, or gross or fine motor development. Prenatally deprived infants demonstrated a 20% reduced spontaneous activity level, lower inhibitory response to novel environments, and more changes from one behavior to another in weekly observation sessions. Postnatally deprived infants demonstrated poorer performance of an object concept task, and greater emotionality relative to controls. This study indicates that different syndromes of behavioral effects are associated with prenatal and postnatal iron deprivation in rhesus monkey infants and that these effects can occur in the absence of concurrent iron deficiency as reflected in hematological measures.

Neurobehavioral evaluation of rhesus monkey infants fed cow's milk formula, soy formula, or soy formula with added manganese.

The possible neurobehavioral effects of excess manganese in soy formula were studied. Male rhesus monkeys (n=8/group) were fed a commercial cow's milk based formula (Control), a commercial soy protein based formula (Soy), or the soy formula with added manganese (Soy+Mn) from birth to 4 months of age. Soy formulas naturally have higher manganese (Mn) content than cow's milk formulas. Monkeys received behavioral evaluations, growth measurements, and cerebrospinal fluid (CSF) sampling from birth to 18 months of age. Soy and Soy+Mn groups engaged in less play behavior and more affiliative clinging in social dyadic interactions. These groups also had shorter wake cycles and shorter periods of daytime inactivity than controls. An impulsivity test was sensitive to the Soy group diet. The Soy+Mn group also had a blunted response to the dopamine agonist apomorphine. Groups did not differ significantly in CSF dopamine and serotonin metabolite concentrations, but these concentrations were correlated with several tasks affected by experimental formula. This experiment suggests that components of soy formula, including Mn, may influence brain development as reflected in behavioral measures.

Movement disorders in the Hfe knockout mouse.

The Hfe(- /-) mouse is a model for human hereditary hemochromatosis (HHH). The accumulation of tissue iron in this condition has led to the suggestion that HHH patients may be at higher risk for neurodegenerative diseases. In this study, adult male Hfe(-/-) mice and wildtype controls (n = 12/group) were evaluated for impairment with motor tests (stride length, landing footsplay, rotarod) as well as a general observational battery (Functional Observational Battery, FOB). Hfe(-/-) mice were characterized by more falls from the rotarod, wider forelimb landing footsplay and hypersensitivity to proximal stimulation. Iron accumulation in brain was not detected by histopathology. These data suggest that a motor syndrome may be associated with HHH that could be further understood through the Hfe(-/-) mouse model.

Endocrine disruption in adolescence: immunologic, hematologic, and bone effects in monkeys.

Environmental contaminants with estrogenic properties have the potential to alter pubertal development. In addition to the reproductive system, other systems that mature under the influence of estrogen could be affected. This study examined the effect on immune, hematologic, and bone mass parameters of treatment with estrogenic agents (methoxychlor, MXC, 25 and 50 mg/kg/day; diethylstilbestrol, DES, 0.5 mg/kg/day) given in the peripubertal period to female rhesus monkeys. DES had striking effects on several parameters assessed measures CBC and clinical chemistry including hematocrit, hemoglobin, serum albumin, liver transaminases, and lipids. Circulating lymphocytes, particularly B cells, were depressed by DES, and a maturational shift in a memory T-cell population was altered. Bone mass and length, as measured after a 9-month recovery period, were significantly lower in the DES group and bone mass tended to be reduced in the femur of the MXC50 group relative to controls. In conclusion, the data indicate that DES had a clear effect on immunohematology and bone growth, while MXC influenced fewer parameters. Disruption in these systems during puberty could alter adolescent risk for anemia and infectious disease and subsequent adult risk for diseases such as osteoporosis, heart disease, and autoimmune disease.

Endocrine disruption and cognitive function in adolescent female rhesus monkeys.

Female rhesus monkeys (n=8/group) received daily oral doses of exogenous estrogen [diethylstilbestrol (DES), 0.5 mg/kg, methoxychlor (MXC), 25 or 50 mg/kg] for 6 months before and after the anticipated age of menarche. Behavior was assessed during and for 9 months after dosing. Visual discrimination performance (simultaneous nonmatch-to-sample with trial-unique stimuli) conducted during dosing demonstrated delayed improvement and poorer performance in the MXC50 group, with some similar effects in the DES group. Visual recognition memory, assessed with delays of < or = 3 s, was not apparently affected. Spatial working memory, assessed after dosing, also showed acquisition deficits and possible working memory difficulties in the MXC50 group. Spontaneous motor activity, monitored at 6-month intervals, was not affected by treatment. Late peak latencies of the auditory brainstem response (ABR) were shorter in the DES group 6 months after treatment, suggesting long-term effects on brain. The study suggests that some aspects of brain function can be modified by exposure to exogenous estrogen during pubertal development. Although DES is a more potent estrogen, the high-dose MXC group was more affected behaviorally. Differential effects of the two agents at the estrogen receptor subtypes (ER alpha and ER beta) may be relevant to the differential behavioral outcomes.

Behavioral characteristics of a nervous system-specific erbB4 knock-out mouse.

ErbB4 is an important brain receptor for the neuregulin1 growth factor. A conditional knock-out mouse was developed lacking both alleles of the erbB4 gene in neurons/glia, and one allele in other cells. The conditional mutant mice were compared to heterozygous null (one null allele and one wildtype allele in all tissues) and wildtype control (no gene deletion) littermates in a battery of behavioral tests. Conditional mutants displayed a lower level of spontaneous motor activity and reduced grip strength compared to wildtype control mice. Group mean scores of heterozygous nulls were intermediate on these measures. However, heterozygous nulls were delayed in motor development and male heterozygous nulls demonstrated altered cue use in a Morris maze learning and memory task relative to both wildtype control and conditional mutant mice. These findings were interpreted based on more detailed analysis of the behavioral data and considerations of the complex nature and multiple roles of the neuregulin/erbB4 system in the nervous system.

Developmental aluminum toxicity in mice can be modulated by low concentrations of minerals (Fe, Zn, P, Ca, Mg) in the diet.

Female Swiss Webster mice were fed diets containing 7 (control) or 1000 microg Al/g diet from conception to weaning. Pregnancy weight gain, birth weight, litter size, postnatal mortality, and weaning weight were measured. In different groups, diets low in Fe, Zn, P, or Ca and Mg (CaMg) were used as basal diets, to which Al was added. Relative to controls, who received NRC recommended levels of these nutrients, all diets with marginal essential trace elements impacted development, as demonstrated by effects on birth weight (CaMg, Fe) or weaning weight (Fe, Zn, P). Compared to diets low in Al, the 1000-mg Al/g diet led to reduced weaning weight regardless of the essential element content of the diet. Other end points were influenced by Al only within the basal diet group; pregnancy weight gain with the low-P diet, litter size with the low-Fe diet, pregnancy completion with the low-Zn diet, and postnatal mortality with the low-CaMg or low-Zn diet. Thus, diets marginal in selected minerals can differentially alter the toxicological profile of developmental Al exposures. A basal diet was also used in which the NRC diet was supplemented with ascorbic acid, which promotes Al absorption. No modification of Al toxicity was seen with ascorbic acid supplementation.

Effects of exogenous estrogenic agents on pubertal growth and reproductive system maturation in female rhesus monkeys.

Concern has been raised that environmental contaminants with estrogenic properties can alter normal sexual maturation. Monkeys, like humans, undergo a long and complex period of development during adolescence, which makes them important models for understanding exogenous estrogen effects during this period. This study examined the consequences of treatment with estrogenic agents (methoxychlor, MXC, 25 and 50 mg/kg/day; diethylstilbestrol, DES, 0.5 mg/kg/day) given in the peripubertal period (6 months before and after the expected age at menarche) to female rhesus monkeys. These treatments increased estrogen activity of serum as determined with an in vitro estrogen receptor alpha (ERa) transcription assay. DES completely suppressed adolescent growth (weight and height) and menses in a reversible manner; smaller effects of MXC on the timing of growth and menarche were also detected. Both DES and MXC led to premature emergence of a secondary sex characteristic, reddening and swelling of skin, but retarded growth of the nipple. As evaluated by ultrasound after an 8-month recovery period, uterine size was not affected by exogenous estrogen, but there was some indication of increased incidence of ovarian cysts/masses in MXC- and DES-treated groups. Ovarian cyclicity, as reflected in urinary hormone metabolites, demonstrated shorter follicular stages in the MXC-treated monkeys. In conclusion, the data indicate that DES had a striking effect on adolescent maturation and that the estrogenic pesticide MXC also altered development during this period. The pattern of effects across agents and doses may be based on specifics of estrogenic action, such as relative ERalpha and ERbeta binding and activation. Long-term consequences of this disruption of pubertal development are being studied in this cohort of monkeys as adults.