Self-injurious behavior: gene-brain-behavior relationships.

This paper summarizes a conference held at the National Institute of Child Health and Human Development on December 6-7, 1999, on self-injurious behavior [SIB] in developmental disabilities. Twenty-six of the top researchers in the U.S. from this field representing 13 different disciplines discussed environmental mechanisms, epidemiology, behavioral and pharmacological intervention strategies, neurochemical substrates, genetic syndromes in which SIB is a prominent behavioral phenotype, neurobiological and neurodevelopmental factors affecting SIB in humans as well as a variety of animal models of SIB. Findings over the last decade, especially new discoveries since 1995, were emphasized. SIB is a rapidly growing area of scientific interest to both basic and applied researchers. In many respects it is a model for the study of gene-brain-behavior relationships in developmental disabilities.

Weaning, body weight, and postpartum amenorrhea duration in pigtailed macaques (Macaca nemestrina).

Early permanent infant separation or weaning decreases the time interval between pregnancies and interbirth intervals for many female primates. At least part of the interpregnancy interval consists of postpartum amenorrhea, a period of non-menstruation lasting from the time of birth until the female begins to ovulate. This study investigated the effects of weaning age and dam's body weight on the duration of the interval between pregnancies, the duration of postpartum amenorrhea, and the number of cycles to conception in a year-round breeder. Female pigtailed macaques (Macaca nemestrina) have an observable perineal swelling that fluctuates throughout the menstrual cycle and provides a means of detecting ovulation. The perineal swelling records of socially housed pigtailed macaques were studied from July 1996 to September 1998. Postpartum amenorrhea data were obtained on 44 females who gave birth to normal, viable infants. As weaning age increased and dam's weight decreased, postpartum amenorrhea, and consequently the interval between pregnancies, increased in duration. The interpregnancy interval consisted almost entirely of the postpartum amenorrhea phase. Our finding that a higher dam's body weight decreased the length of postpartum amenorrhea duration lends support to the hypothesis that a minimum body weight is necessary for menstrual cycles to occur. Most females became pregnant on their first ovulation regardless of weaning age and whether or not they were carrying an infant. As the weaning age of the infant and the dam's weight increased, ovulation went from occurring after separation to occurring before separation.

Demographic analysis of the washington regional primate research center pigtailed macaque colony, 1967-1996.

This work presents the results of a demographic analysis of 30 years of breeding records from the University of Washington's recently closed Primate Field Station at Medical Lake, Washington. Summaries of population growth, age-specific fertility and mortality rates, first-year survival, and seasonality of reproduction are presented, as well as an analysis of survival by decade. In addition, we present data on interbirth intervals in this population. In general, pigtailed macaques represent a typical Old World monkey pattern of age-specific fertility and mortality, with a few minor exceptions. We suggest that pigtailed macaques are most similar to rhesus and Barbary macaques, and that Japanese and bonnet macaques differ somewhat in their demographics.

Social housing and pregnancy outcome in captive pigtailed macaques.

We present a retrospective analysis of 30 years of breeding records from a colony of pigtailed macaques at the University of Washington's Regional Primate Research Center, specifically examining the effects on pregnancy outcome of sire presence, presence of other pregnant females, group stability, overall group size, and dam age and parity. Data on 2,040 pregnancies (1,890 live births) of socially housed pigtailed macaques (Macaca nemestrina) were obtained from the Washington Regional Primate Research Center's animal colony records from 1967 to 1996. Our results suggest that the presence of the sire and other pregnant females, fewer moves, and lower parity increases the probability of a viable birth. In viable and nonviable births, gestation length was positively related to contact with the sire and other pregnant females, number of moves, and dam age. Once the effect of gestational age was taken into account, birthweight increased with increasing parity and decreased with dam age. Clinical treatment of the dam decreased as sire presence and group size increased and number of moves decreased. The length of treatment was dependent on the number of moves experienced by the dam, with more moves associated with longer treatments. Sire presence was the single most important factor in nearly all measures of reproductive outcome.

Behavioral measurement of temperament in male nursery-raised infant macaques and baboons.

We define temperament as an individual's set of characteristic behavioral responses to novel or challenging stimuli. This study adapted a temperament scale used with rhesus macaques by Schneider and colleagues [American Journal of Primatology 25:137-155, 1991] for use with male pigtailed macaque (Macaca nemestrina, n = 7), longtailed macaque (M. fascicularis, n = 3), and baboon infants (Papio cynocephalus anubis, n = 4). Subjects were evaluated twice weekly for the first 5 months of age during routine removal from their cages for weighing. Behavioral measures were based on the subject's interactions with a familiar human caretaker and included predominant state before capture, response to capture, contact latency, resistance to tester's hold, degree of clinging, attention to environment, defecation/urination, consolability, facial expression, vocalizations, and irritability. Species differences indicated that baboons were more active than macaques in establishing or terminating contact with the tester. Temperament scores decreased over time for the variables Response to Capture and Contact Latency, indicating that as they grew older, subjects became less reactive and more bold in their interactions with the tester. Temperament scores changed slowly with age, with greater change occurring at younger ages. The retention of variability in reactivity between and within species may be advantageous for primates, reflecting the flexibility necessary to survive in a changing environment.

Fetal, infant, and maternal toxicity of zidovudine (azidothymidine) administered throughout pregnancy in Macaca nemestrina.

The toxicity of azidothymidine (AZT) was studied in monkey dams and fetuses that were exposed to the drug over the entire gestational period. Fourteen virus-free female macaques (Macaca nemestrina) were randomly assigned to AZT or control groups. AZT animals received the drug through a gastric catheter at a dose of 1.5 mg/kg every 4 hours, which produced plasma concentrations similar to those in humans taking 500 to 600 mg/day of AZT. Control animals received water placebo, also through gastric catheter. Some animals participated in both groups. All females were mated with the same male; 41 matings produced 20 pregnancies, of which 16 were carried to term (9 in AZT females; 7 in control females). The AZT animals developed an asymptomatic macrocytic anemia, but hematologic parameters returned to normal when AZT was discontinued. Total leukocyte count decreased during pregnancy and was further affected by AZT administration. AZT-exposed infants were mildly anemic at birth. AZT caused deficits in growth, rooting and snouting reflexes, and the ability to fixate and follow near stimuli visually, but the deficits disappeared over time. These data indicate that early exposure to AZT in utero should have no irreversible adverse effects on the fetus.

Multiple-spell, discrete-time survival analysis of developmental data: object concept in pigtailed macaques.

To measure cognitive development in 123 pigtailed macaques, we calculated medians and quartiles for the milestones of classical (Piagetian) object concept development (plain reach, partial-hide, full-hide, and A-not-B) in both 2-dimensional (screen) and 3-dimensional (well) tasks. Using multiple-spell, discrete-time survival analysis, we examined the influence of 4 independent variables (starting age, sex, birth weight, and task) on the probability of completing the milestones on any given test. The significant predictors for completion of the well sequence were birth weight and task. The best predictors for completion of the screen sequence were birth weight, number of test sessions, and interaction between birth weight and task. Birth weight had a greater predictive relationship in the earlier stages. This analysis provided information that cannot be obtained with traditional parametric methods.

Social development in nursery-reared pigtailed macaques (Macaca nemestrina).

The social development of 240 nursery-reared pigtailed macaques (Macaca nemestrina) was studied from postnatal weeks 4 to 32. The objectives of the study were to document developmental trends and evaluate social behavior in laboratory-reared M. nemestrina raised at the University of Washington Infant Primate Laboratory, and to identify husbandry factors that might affect early social development. Only infants who had not undergone invasive postnatal experimental manipulation and had no chronic illness or injuries were included in the study. Infants were separated from their mothers and housed singly, but had access to peers for 30 min a day, 5 days a week, in a large playroom. Play and social behaviors emerged early in development, increased during the developmental period studied and occupied a large portion of the infants' time budgets. Although disturbance behaviors occurred with some frequency and duration early in development, they occupied a very small portion of the infants' time budget at 8 months of age. Weaning from infant formula at 16-19 weeks retarded development of play behavior. Permanent removal of a cloth comforter (diaper) during weeks 20-24 had no long-term behavioral effects. It was concluded that at 8 months of age these infants showed relatively normal species-typical behavioral repertoires.

Pair-rearing infant monkeys (Macaca nemestrina) using a "rotating-peer" strategy.

Appropriate rearing conditions for captive primates are important for both research and breeding purposes. In an earlier study, pigtailed macaque infants that were pair-reared with a single continuous partner exhibited excessive social clinging and could not adapt to living in large social groups at 8-10 months of age. In the present study, eight macaques were pair-reared until they were 6 months old. Each member of an animal's four-monkey social group served as a home-cage partner. In an attempt to reduce excessive mutual clinging, the pairs were rotated every 2-3 days to increase the variability of social stimulation in the home cage. However, these infants developed abnormal social behaviors that were in some cases even more extreme than those exhibited by infants pair-reared with a single continuous partner. A second goal of this experiment was to study interlaboratory reliability for the development of social behavior. The animals were divided into two groups, one housed in a nursery and the other in a biological safety level 3 virus laboratory. Some differences were detected between the two groups, demonstrating the necessity of controls in biobehavioral developmental research.

Parental MHC antigen sharing and pregnancy wastage in captive pigtailed macaques.

Among some human populations, immunogenetic similarity between mates is associated with increased risk of pregnancy loss. To investigate the relationship between histocompatibility and reproductive performance in non-human primates, 128 pigtailed macaque couples were classified as 'reproductively successful' or 'unsuccessful' according to previous breeding performance. These couples were arranged into 64 triads composed of individual females, and a 'successful' and 'unsuccessful' mate. Individuals were typed for class I MHC antigens using a microcytotoxicity technique and species-specific alloantisera. Matched-pair analysis revealed that significantly more 'unsuccessful' couples shared MnLA-A antigens than did the matched 'successful' couples. Conditional matched-pair logistic regression analysis further revealed that parental sharing of MnLA-A antigens is an even more significant predictor of pregnancy wastage than is advanced maternal age. In our study population, sharing of MnLA-A antigens predicted 72% of pregnancy loss among 'unsuccessful' couples (P < 0.009). Identification of histocompatibility-associated factors influencing pregnancy success could have profound clinical implications for chronic spontaneous abortion, intra-uterine growth retardation and birth defects in humans. Among captive primates, identification of MHC or MHC-linked genes affecting reproductive outcome could lead to more efficient colony management strategies as well as development of a model for understanding human immunologically-mediated reproductive failure.

Reproduction and sera embryotoxicity after immunization of monkeys with the laminin peptides YIGSR, RGD, and IKVAV.

Monkeys with excellent reproductive histories were immunized with the laminin peptides YIGSR, RGD, IKVAV, and YD, a control sequence with no known biological function. Sera from the YIGSR-immunized monkey became toxic, causing neural tube defects in whole rat embryo cultures, and this monkey experienced fetal loss after immunization. Sera from the RGD-immunized monkey also became embryotoxic in culture after immunization, but this monkey appeared to become infertile as she failed to initiate a pregnancy for at least 2 years after immunization. In contrast, embryos cultured on sera from the IKVAV- or YD-immunized monkeys were predominantly normal and both monkeys completed successful pregnancies. Antibody levels to the respective peptides or to laminin were not predictive of embryotoxicity, but antibody binding to homogenized yolk sacs as well as to yolk sacs of cultured embryos was associated with sera embryotoxicity and reproductive outcomes in vivo. These observations suggested that the laminin sequences YIGSR and RGD may play a role in immune-mediated reproductive failure by reacting directly with embryonic tissue and could provide a basis for identifying individuals at risk for both spontaneous abortion and infertility.

Social preferences by and for pigtailed macaques (Macaca nemestrina) with trisomy 18.

Social choices of trisomic macaques (macaca nemestrina) were compared with those of age-matched controls and of infants and adult females without handicaps. All groups chose social over nonsocial stimuli and showed few differences in their preferences for stimulus animals with and without handicaps. On initial encounter, the trisomic monkeys were socially interesting to age-matched controls and to younger animals and adult females. Thus, avoidance of individuals with handicaps probably is not a general primate trait. Even though the trisomic monkeys showed inappropriate social and motor behavior in play groups, their preference for social stimuli demonstrates that the presence of mental retardation and physical handicaps need not reduce positive social motivation even when prior social experiences have been largely negative.

Fetal toxicity of zidovudine (azidothymidine) in Macaca nemestrina: preliminary observations.

The objective of this study was to determine the dam, fetal, and infant toxicity of zidovudine (AZT) administered to pigtailed macaques during pregnancy. Pregnant macaques were administered AZT (1.5 mg/kg/dose every 4 h) or water via gastric catheter throughout pregnancy. AZT concentration and hematological changes were monitored in the dam, and fetal growth was monitored via ultrasound. Infant hematocrit was assessed at birth, and the neurological, perceptual, and motor development of the offspring were assessed for 9 to 10 months. Twelve pregnancies were brought to term. Mean plasma concentrations of AZT were comparable to those in human studies. Hemoglobin dropped significantly in pregnant dams and remained low, whereas platelets increased during treatment but returned to normal before the end of the study. There were no significant differences in any ultrasound measure of fetal growth, and AZT-exposed infants exhibited little behavioral delay or impairment. We predict no significant toxic effects of prenatal AZT exposure at this dosage in humans.

Postnatal growth and skeletal maturation of experimental preterm macaques (Macaca nemestrina).

The growth and skeletal maturation of nine preterm female pigtailed macaques (Macaca nemestrina) obtained by C-section at less than or equal to 155 postconceptional days were followed through six months of age. At C-section they were of normal size and maturation for gestational age. Compared with 50 normal females born at term (mean = 173 +/- 6.4 postconceptional days), preterm infants were also of normal size at term, but delayed in skeletal maturation, requiring about one month to achieve the standard.

Methylmercury effects on the social behavior of Macaca fascicularis infants.

Observations of the social behavior of Macaca fascicularis exposed in utero to methylmercury (MeHg) and nonexposed control infants were performed as part of a study of the toxic, reproductive and developmental effects of maternal MeHg intake. Infants were tested twice weekly from 2 weeks to 8 months of age. Data were summarized into 6 categories of social behavior and 7 categories of nonsocial behavior. Analysis of the most prevalent behavior indicated that MeHg-exposed offspring exhibited a decrease in social play behavior and a concomitant increase in nonsocial passive behavior. The MeHg effect on social play behavior tended to decrease with age, while the group differences in nonsocial passive behavior tended to increase. The results indicate that maternal intake of MeHg during pregnancy can affect the social development of infant primates by suppressing social interactions and increasing nonsocial behavior.

Laminin immunized monkeys develop sera toxic to cultured rat embryos and fail to reproduce.

In a previous study antilaminin antibodies in a monkey with a poor reproductive history were found to be the cause of serum toxicity to cultured rat embryos. In the present study four monkeys were immunized with murine tumor laminin and a fifth with bovine serum albumin. Subsequently, sera from only the laminin immunized monkeys became toxic to cultured rat embryos. This serum toxicity was not mediated by complement but did require the antibody to have a divalent structure. Finally, mating trials were conducted with two of the laminin immunized monkeys that previously had excellent reproductive histories. Based on progesterone levels and observation the monkeys continued to have normal menstrual cycles but failed to initiate a successful pregnancy following immunization in over 2 years of mating trials. These data demonstrated that antibodies against laminin could have prevented conception or could have interrupted pregnancy because of embryotoxicity or failure of implantation.

Deficits in visual recognition in low birth weight infant pigtailed monkeys (Macaca nemestrina).

15 low birth weight and 15 normal birth weight pigtailed monkey infants were administered an adaptation of a standardized test of visual recognition memory, originally developed for human infants. Animals were given a series of problems in which 2 identical black-and-white patterns were presented for a familiarization period. The previously exposed pattern was then paired with a novel one, and looking time to each pattern was recorded. The normal birth weight animals directed a significant amount of their visual attention to the novel stimuli, thus demonstrating recognition abilities. As a group, the performance of the low birth weight infants remained at chance. These findings have important implications for an animal model to examine factors contributing to poor cognitive outcome in low birth weight human infants.

Prenatal psychological stress, dermatoglyphic asymmetry and pregnancy outcome in the pigtailed macaque (Macaca nemestrina).

The relationships between maternal psychosocial stress during pregnancy and asymmetry in dermal ridge count, gestation length, birth weight percentile and survival were examined in 68 pigtailed macaque offspring. Twenty-five pregnant females were stressed daily by capture from 30 through 130 days postconception; 43 control unstressed females were housed under conditions of minimal disturbance. The difference between total intercore dermal ridge counts between right and left hands of the offspring was used as a measure of the perturbed development that theoretically occurs in the presence of a prenatal stressor. Dermatoglyphic asymmetry was significantly higher in the stressed offspring than in the unstressed group (mean asymmetry = 7.3 +/- 2.8 and 5.4 +/- 2.5, respectively; t = 2.85, p less than 0.01). Although maternal stress alone was not related to differential gestation length, birth weight, or survival, high asymmetry (8-13 residual dermal ridges) was significantly associated with increased perinatal mortality.

Diagnosis of early pregnancy by ultrasound in Macaca fascicularis.

Real-time ultrasonography was used to detect early pregnancy in 32 longtailed macaques (Macaca fascicularis). In 92% of the successful conceptions, a correct diagnosis was made. The earliest sign of pregnancy was an intrauterine ringlike structure (11 days). A "line swelling" (14 days) preceded definite fetal echoes (21 days), and fetal heart motion (30 days) proved fetal viability. Ultrasound is a rapid, noninvasive, and relatively cost-effective method of diagnosing and monitoring early pregnancy in M. fascicularis.

Volumetric growth of the major brain divisions in fetal Macaca nemestrina.

Brains from 22 age-dated fetal Macaca nemestrina were embedded in celloidin and prepared for histological serial sections. A computer-based morphometric system was used to digitize contours of neural structures and to calculate their areas and volumes. Shrinkage of the brain sections was corrected by a multiplication factor relating pre-processed brain volume to the computer-calculated volume of the processed brain. Volume growth of the telencephalon, mesencephalon and pons-medulla was linear over the fetal period of 60 days postconception to near-term at 166 days postconception. Volume growth of the total brain, diencephalon and cerebellum, was curvilinear with respect to age, with slower growth initially and faster growth in the later stages of gestation. Total brain and body grew with an almost 1:1 relation during the fetal period. The proportionate growth of the brain was largely accounted for by telencephalic growth. The other brain divisions all showed different growth rates in relation to growth of the body.