Infant arousal in an en-face exchange with a new partner: effects of prematurity and perinatal biological risk.

Very low birth weight (VLBW) infants of higher (n = 18) and lower (n = 29) perinatal biological risk were contrasted at 4 months adjusted age with healthy full-term infants (n = 32) in their arousal during a standardized peekaboo game with an examiner. VLBW infants showed less positive arousal, more negative arousal, and 3 mixtures of behavioral cues across the peekaboo game seldom seen for full-term infants-strong cues of both positive and negative arousal, strong cues of negative arousal alone, and no strong cues of either positive or negative arousal. Contrary to expectations, perinatal biological risk did not strongly predict variations in arousal within the VLBW group. Possible changes in how internal and external sources of arousal are integrated provide one explanation for the presence of strong relationships between perinatal biological risk and social responsiveness near term age and their disappearance by 4 months of age.

Probability of reinforcement and the development of stimulus control.

Pigeons were trained with a successive discrimination procedure in which responding during the negative stimulus was never reinforced and responding during the positive stimulus was reinforced according to one of four probability values. This discrimination training followed extensive training with a single, neutral stimulus and the same temporal distribution of reinforcements. The development of stimulus control was studied by tracing the difference in rate of responding between the positive and negative stimuli over the course of discrimination training. Response rate during the positive stimulus remained constant, while that during the negative stimulus decreased to zero. The probability of reinforcement associated with the positive stimulus affected both the total number of responses emitted during the negative stimulus and the number of negative stimulus presentations during which responding occurred. However, the number of reinforcements during the positive stimulus preceding the attainment of various degrees of stimulus control was similar for all probability values.

Lessons drawn from observing young peers together.

Based on studies during the past 13 years of what transpires between young peers, lessons are drawn about the nature of human sociability and the development of social skill during the first three years of life. Peer encounters have proven especially helpful for discovering the forms of sociability and social skill the infant is capable of without the aid of a more skillful social partner. From early in infancy, children are quite sociable with peers (age-mates), both in novel play settings and in their own home or customary group care settings, both with an unfamiliar peer and with those quite familiar, both at the start of acquaintanceship with a particular peer and after many encounters with that peer. Their sociability is seen in their attraction to peers, their directing to peers of such distinctively social behaviors as vocalizations, smiles, and gestures, and the predominantly friendly nature of their behavior. Peer encounters in the absence of customary play materials refute claims that attraction to peers is a by-product of interest in toys and the inanimate spectacles peers create through their actions on toys. Distinctions should be drawn between sociability and social skills, especially interactive skills. Interactive skills are systematic ways the young child relates his/her own behavior to the details of a partner's behavior that function to facilitate such valued social outcomes as the generation of a cooperative game or a conversation or the resolution of a dispute. Observations of young peers highlight the distinctive nature of the infant's interactive skills. Social influence between peers is present from 6 months, but rarely takes the form customary for older children. Joining a peer and manipulating the same play material as the peer are rudimentary interactive skills that emerge by 12 months. Interactive skills enabling the generation of extended sequences of social interaction on a common cooperative theme progress rapidly during the third year of life. The distinctive form of the young child's interactive skills produces distinctive patterns of interaction among young peers. Their interactions are managed largely nonverbally well into the third year of life, and extended cooperative interactions most often take the form of games in which one or both children imitate each other's actions. Despite the predominance of imitation, their encounters are also marked by complementary role relationships. The distinctive features of peer encounters prompt speculations about the role peer encounters can play in early development.

Toys and social interaction between infant peers.

Claims that young infants fail to react in a social manner to one another and that toys preempt attention to peers were assessed by comparing the interactions observed between infant peers when they met in the presence of toys versus in their absence. 44 pairs of unacquainted infants (either 10--12 or 22--24 months of age) came with their mothers to an unfamiliar room. Without toys available in the room, infants of both ages more often contacted one another, smiled at and gestured to one another, and duplicated each other's actions. With toys, they showed and exchanged toys and spent more time synchronously manipulating similar play material. The results document that infants as young as 10 months of age are responsive to the person and behavior of an unfamiliar peer and that they are no less responsive than older infants to the social versus nonsocial aspects of a novel setting.

Normative early head growth in very-low-birth-weight infants.

Normative head growth curves were developed from serial weekly measurements of head circumference in 50 infants with birth weights less than 1500 gm who had good neurodevelopmental outcome at 2 years of age (assessed by neurologic examination and by the Bayley Mental Developmental Scale). Forty-one of the infants with good outcome were normocephalic at birth; after head shrinkage during the first week of life, increments in head circumference averaged 0.49 cm during the second week, 0.79 cm during the third week, and 0.95 cm per week thereafter. Nine infants with good outcome were microcephalic at birth; these infants had no head shrinkage during the first week of life and had a significantly greater mean weekly increment in head circumference of 0.98 cm (P less than 0.008). In contrast, 10 normocephalic and seven microcephalic infants with poor outcome had significantly less postnatal head growth (P less than 0.02 and p less than 0.001, respectively). Head growth curves developed from measurements in infants with documented good short-term developmental outcome are the most appropriate standards for head growth for very-low-birth-weight infants.

Toddlers' emerging ways of achieving social coordinations with a peer.

14 peer dyads were observed longitudinally at 16, 20, 24, 28, and 32 months to assess developmental changes in social coordinations (both action-to-action thematic relations and extended games). Each child's movements through the playroom, actions upon play material, vocalizations, verbalizations, and gestures were coded for their relation to the concurrent or immediately prior behavior of the peer: Unrelated, Tangential, Coordinated, Interfering. There was a marked increase with age in acts coordinated with those of a peer, and imitations of the peer's nonverbal actions accounted for most of the developmental change. The use of words to direct the peer in a coordinated way increased with age but remained infrequent. Developmental change in the frequency of games paralleled that for imitative acts, and imitative acts both established and set the theme for most of the games. Thus, imitating another's nonverbal actions is a core behavioral strategy for achieving social coordinations during the developmental period preceding reliance on verbal communication in peer interaction.

A genetic analogue of 'mark-recapture' methods for estimating population size: an approach based on molecular parentage assessments.

Molecular polymorphisms have been used in a variety of ways to estimate both effective and local census population sizes in nature. A related approach for estimating the current size of a breeding population, explored here for the first time, is the use of genetic 'marks' reconstructed for otherwise unknown parents in paternity or maternity analyses of progeny arrays. This method provides interesting similarities and contrasts to traditional mark-recapture methods based on physical tags. To illustrate, this genetic method is applied to a population of painted turtles on the Mississippi River to estimate the number of successfully breeding males. Non-genetic mark-recapture approaches were also applied to animals trapped at this location. Results demonstrate that such genetic data on parentage can be helpful not only in estimating contemporary population sizes, but also in providing additional information, not present in customary mark-recapture data, about possible extended movements of breeding individuals and the size of the pool of mates which they encounter.

Mother-child conversational interactions as events unfold: linkages to subsequent remembering.

The study reported here was designed to examine linkages between mother-child conversational interactions during events and children's subsequent recall of these activities. In this longitudinal investigation, 21 mother-child dyads were observed while they engaged in specially constructed activities when the children were 30, 36, and 42 months of age. Analyses of the children's 1-day and 3-week recall of these events indicated that at all age points, features of the activities that were jointly handled and jointly discussed by the mother and child were better remembered than were features that were either (1) jointly handled and talked about only by the mother, or (2) jointly handled and not discussed. Potential linkages were also explored between incidental memory for personal experiences and deliberate recall of familiar but arbitrary materials. In this regard, children's recall of the special activities was positively correlated with their recall of objects in a deliberate memory task performed at 42 months.

Nursery Neurobiologic Risk Score: important factor in predicting outcome in very low birth weight infants.

We developed a nursery Neurobiologic Risk Score (NBRS) based on potential mechanisms of brain cell injury in preterm infants and correlated it with developmental outcome at the corrected ages of 6, 15, and 24 months. The NBRS was determined at 2 weeks of age and at the time of discharge from intensive care in 58 preterm infants with birth weights less than or equal to 1500 gm. The NBRS correlated significantly with the Bayley Scales of Infant Development, Mental Development Index (MDI) (r = -0.61 to -0.40) and Psychomotor Development Index (PDI) (r = -0.59 to -0.46), and with abnormal neurologic examination findings (r = 0.59 to 0.73) at the three testing periods. Although 12 of the 13 items composing the NBRS individually correlated with one or more outcome variables, seven items (infection, blood pH, seizures, intraventricular hemorrhage, assisted ventilation, periventricular leukomalacia, and hypoglycemia) accounted for almost all of the explained variance. Logistic regression of individual items demonstrated intraventricular hemorrhage to be the most important item for predicting the MDI at 24 months; pH was the most influential item for predicting the PDI at every testing period. A shorter, revised NBRS that included only the seven significant items demonstrated as strong a correlation with developmental outcome as the original NBRS. A revised 2-week score of greater than or equal to 5 or a discharge score of greater than or equal to 6 demonstrated 100% specificity and had a 100% positive predictive value for an abnormal outcome at 24 months of age in this group of infants. We conclude that the NBRS identifies during the intensive care nursery stay those infants at highest risk for an abnormal outcome related to nursery events. In addition, analysis of NBRS items provides insight into the relative importance of individual factors for influencing mental, motor, and neurologic outcome.

Uptake and metabolism of hydroxymatairesinol in relation to its anticarcinogenicity in DMBA-induced rat mammary carcinoma model.

The chemopreventive effects of hydroxymatairesinol (HMR), a lignan extracted from Norway spruce (Picea abies), on the development of mammary carcinoma induced by 7,12-dimethylbenz[a]anthracene (DMBA) was studied in rats. HMR administered via diet in an average daily dose of 4.7 mg/kg body wt starting before DMBA induction reduced tumor volume and tumor growth, but no significant reduction in tumor multiplicity (number of tumors/rat) was observed. The predominant histological type in the control group was type B (well-differentiated adenocarcinoma, 78%). The proportion of type B tumors decreased to 35% in the HMR group, while the type A (poorly differentiated) and type C (atrophic) tumor proportions increased. Anticarcinogenic effects of dietary HMR (4.7 mg/kg) were also evident when the administration started after DMBA induction and was seen as growth inhibition of established tumors. Dietary HMR supplementation significantly increased serum and urinary enterolactone and HMR concentrations but had no significant effect on the uterine weight, suggesting that HMR or its major metabolite enterolactone did not have an antiestrogenic effect. Further studies are warranted to further clarify and verify HMR action and the associated mechanisms in mammary tumorigenesis.

Hydroxymatairesinol, a novel enterolactone precursor with antitumor properties from coniferous tree (Picea abies).

The potential for the extraction of the plant lignan hydroxymatairesinol (HMR) in large scale from Norway spruce (Picea abies) has given us the opportunity to study the metabolism and biological actions of HMR in animals. HMR, the most abundant single component of spruce lignans, was metabolized to enterolactone (ENL) as the major metabolite in rats after oral administration. The amounts of urinary ENL increased with the dose of HMR (from 3 to 50 mg/kg), and only minor amounts of unmetabolized HMR isomers and other lignans were found in urine. HMR (15 mg/kg body wt po) given for 51 days decreased the number of growing tumors and increased the proportion of regressing and stabilized tumors in the rat dimethylbenz[a]anthracene-induced mammary tumor model. HMR (50 mg/kg body wt) did not exert estrogenic or antiestrogenic activity in the uterine growth test in immature rats. HMR also showed no antiandrogenic responses in the growth of accessory sex glands in adult male rats. Neither ENL nor enterodiol showed estrogenic or antiestrogenic activity via a classical alpha- or beta-type estrogen receptor-mediated pathway in vitro at < 1.0 microM. HMR was an effective antioxidant in vitro.