Maternal and neonatal risk factors for mental retardation: defining the 'at-risk' child.

OBJECTIVE: To determine how mental retardation at age seven is related to certain maternal, perinatal, and neonatal characteristics. METHOD: A sample of 35,704 children followed from the prenatal period to age 7 years in the Collaborative Perinatal Project provided data on nine maternal and pregnancy characteristics and 12 neonatal factors. RESULTS: Low socioeconomic status of the family (SES) accounted for 44-50% of mental retardation and a low level of maternal education accounted for 20%. Other prenatal factors with significantly elevated relative risks, (P < 0.05) were maternal IQ score less than 70, weight gain in pregnancy less than 10 pounds and multiple birth. Maternal anemia in pregnancy accounted for 14% of mental retardation in blacks, and, urinary tract infections accounted for 6% of mental retardation in whites. Significant elevations in relative risk were found for major genetic and post-infection syndromes, CNS malformations, cerebral palsy, seizures, abnormal movements or tone, and low birth weight. Relative risk was also significantly increased with low 1 minute APGAR, primary apnea, and head circumference and length more than 2 SD below average but only in the low SES black subgroup. CONCLUSION: Early developmental events can be ranked on the basis of the strength of their association with mental retardation and such rankings can be used as a guide for defining risk status in early infancy.

Fatiguing isometric contraction of hind-limb muscles results in the release of immunoreactive neurokinins from sites in the rostral medulla in the anesthetized cat.

Antibody-coated microprobes were used to determine whether immunoreactive neurokinins (irNK) were released from sites in the brainstem during fatiguing isometric contractions of the triceps surae muscles in cats anesthetized with alpha-chloralose. Contractions were generated by stimulating the tibial nerve using a microprocessor-controlled stimulator. Microprobes were inserted into the periaqueductal grey (P 0.5-1.0 mm) or the medullary brainstem (either 3.0 or 3.5 mm rostral to the obex) prior to, during and following fatiguing contractions. No release of irNK was detected from the periaqueductal grey as a result of fatiguing isometric contractions. When probes were inserted 3.0 mm rostral to the obex, a basal release of irNK was detected from the medulla but this was inhibited during isometric contractions from sites corresponding to the lateral tegmental field. When probes were inserted into the more rostral site in the medulla (3.5 mm rostral to the obex), irNK were released in response to contractions from sites corresponding to lateral reticular nucleus, ventral regions of the nucleus tractus solitarius and the medial vestibular nucleus. No irNK were released from this site (3.5 mm rostral to obex) either during passive leg flexing, during nerve stimulation following gallamine injection and muscle paralysis or during stimulation of the central end of the cut tibial nerve. These results demonstrate that neurokinins are released from discrete sites in the medulla in response to fatiguing muscle contractions and suggest that tachykinin neurons may be a component of the pathways regulating blood pressure during ergoreceptor activation.

Detection of immunoreactive substance P-like substances from cat brainstem sites during fatiguing isometric contractions.

Isometric contractions were generated on the left hindlimb muscles from adult cats (n = 11) anesthetized with alpha-chloralose (75 mg/kg) to determine whether immunoreactive substance P (irSP) was released from either the right periaqueductal grey (PAG) or ventrolateral medulla (VLM), sites shown to be involved with the integration of the muscle pressor response. The release of immunoreactive SP was measured using SP antibody-coated microelectrodes that were inserted into the PAG or the VLM during periods of rest, fatiguing isometric contractions and post-contraction. Mean arterial pressure increased by 78 +/- 11 mmHg during the contractions. There was a release of irSP from sites in the medulla during the contractions compared to the non-contraction periods but none was detected from the PAG in response to muscle stimulation. These results provide further evidence that SP-like substances may be involved with the central integration of the muscle pressor response.

Assessment of sex differences for multifactorial traits using path analysis: application to learning difficulties.

A general model of multifactorial inheritance is described which allows for sex-specific transmission from parent to offspring, sex-specific correlations in the rearing environments of full siblings, and different prevalences for males and females for qualitative traits. Formulas for the correlations between several types of relatives are given in terms of an underlying path model, and a computer program, available upon request, is described. The model is applied to the Collaborative Perinatal Project sample of siblings and first cousins of children with learning difficulties. No sex differences were found either in transmission or in correlated sibling environments for learning difficulties. Evidence is given that the correlation between the rearing environments of siblings is negative, possibly due to differential allocation and family resources.

Offspring of schizophrenics. III. Hyperactivity and neurological soft signs.

Twenty-nine male offspring of "continuous schizophrenics" (chronic, borderline, and chronic schizoaffective schizophrenics), plus controls, were given neurological and psychological examinations at age 7. Eight of the 29 were found to have high ratings on a factor score that was termed "hyperactive" (increased activity, impulsivity, distractibility, and emotional lability), and three of these boys had high ratings for neurological signs as well. These frequencies were significantly greater than the control values. Mild incoordination, such as awkwardness in performing rapidly alternating movements, was the neurological soft sign most elevated in the index group. Fifteen female offspring of schizophrenics were not found to differ from their controls on these measures. Previous studies of the childhood of male schizophrenics have found behavior patterns similar to the behavior of the boys who scored high on our hyperactive factors. It is thus likely that the "hyperactive cases" in this sample are even more at risk for developing schizophrenia in later life than the other offspring of schizophrenic parents.

Intellectual development of twins -- comparison with singletons.

Analysis of mental and motor tests scores and intelligence test performance of twins born in the Collaborative Perinatal Project shows that twins perform more poorly than singletons from the same population and that the differences are greater in Negroes than in whites. The poor performance of twins relative to that of singletons is of complex etiology. It is partly due to poor prenatal environment, for twins brought up as singletons perform at the intelligence level of twins and not of singletons. It may also be partly due to the higher incidence of congenital malformations in twins, especially those of the central nervous system. But the performance of twins, relative to that of singletons, tends to improve as they get older, at least from 4 to 7 years, suggesting that prematurity is also a contributing factor, whose detrimental effects may be reversible.