Brain Imaging Studies of the Anatomical and Functional Consequences of Preterm Birth for Human Brain Development

Unicellular Ca2+ signaling 'toolkit' at the origin of metazoa

Ca(2+) signaling pathways control many physiological processes in almost all types of animal cells such as fertilization, muscle contraction, hormone release, and learning and memory. Each animal cell type expresses a unique group of molecules from the Ca(2+) signaling 'toolkit' to control spatiotemporal patterns of Ca(2+) signaling. It is generally believed that the complex Ca(2+) signaling 'toolkit' has arisen from the ancestral multicellular organisms to fit unique physiological roles of specialized cell types. Here, we demonstrate for the first time the presence of an extensive Ca(2+) signaling 'toolkit' in the unicellular choanoflagellate Monosiga brevicollis. Choanoflagellates possess homologues of various types of animal plasma membrane Ca(2+) channels including the store-operated channel, ligand-operated channels, voltage-operated channels, second messenger-operated channels, and 5 out of 6 animal transient receptor potential channel families. Choanoflagellates also contain homologues of inositol 1,4,5-trisphosphate receptors. Furthermore, choanoflagellates master a complete set of Ca(2+) removal systems including plasma membrane and sarco/endoplasmic reticulum Ca(2+) ATPases and homologues of 3 animal cation/Ca(2+) exchanger families. Therefore, a complex Ca(2+) signaling 'toolkit' might have evolved before the emergence of multicellular animals.

Developmental characteristics of very low-birthweight infants at 18 months' corrected age according to birthweight

BACKGROUND

The objective of the present study was to describe developmental profiles of very low-birthweight (VLBW) infants compared by birthweight, because those of infants with birthweight <750 g might be different from other VLBW infants.

METHODS

VLBW infants from four medical centers were followed at each site with the same protocol at 18 months' corrected age. The protocol by the Society for the Study of Follow up for High-Risk Infants, which includes a standardized developmental test, the Kyoto Scale of Psychological Development (KSPD), was used. Five hundred and sixty-four VLBW infants without neurological or neurosensory impairment were divided into four groups using 250 g birthweight intervals and outcomes were compared between the four groups.

RESULTS

Developmental characteristics of extremely low-birthweight infants (birthweight <750 g) in comparison with other VLBW infants were as follows: (i) more infants were judged clumsy in their fine motor skills; (ii) fewer were able to speak meaningful words although they were able to understand oral simple orders; (iii) developmental quotients (DQ) of KSPD was significantly lower; and (iv) more infants were judged as hyperactive.

CONCLUSION

Developmental profiles of VLBW infants without major handicaps at 18 months' corrected age correlated significantly with their birthweight sequence. These results provide useful information on developmental outcomes of VLBW infants.

Low birthweight and preterm birth in young people with special educational needs: a magnetic resonance imaging analysis

BACKGROUND

Although neuroanatomical and cognitive sequelae of low birthweight and preterm birth have been investigated, little is understood as to the likely prevalence of a history of low birthweight or preterm birth, or neuroanatomical correlates of such a history, within the special educational needs population. Our aim was to address these issues in a sample of young people receiving additional learning support.

METHODS

One hundred and thirty-seven participants aged 13-22 years, receiving additional learning support, were recruited via their schools or colleges and underwent structural magnetic resonance imaging (MRI). Obstetric records, available in 98 cases, included birthweight and gestational data in 90 and 95 cases, respectively. Both qualitative and quantitative voxel-based analyses of MRI data were conducted.

RESULTS

A history of low birthweight and preterm birth was present in 13.3% and 13.7% of cases, respectively. Low birthweight and preterm birth were associated with specific qualitative anomalies, including enlargement of subarachnoid cisterns and thinning of the corpus callosum. Low birthweight was associated with reduced grey matter density (GMD) in the superior temporal gyrus (STG) bilaterally, left inferior temporal gyrus and left insula. Prematurity of birth was associated with reduced GMD in the STG bilaterally, right inferior frontal gyrus and left cerebellar hemisphere. Comparison of subjects with no history of low birthweight or preterm birth with a previously defined control sample of cognitively unimpaired adolescents (n = 72) demonstrated significantly greater scores for several anomalies, including thinning of the corpus callosum, loss of white matter and abnormalities of shape of the lateral ventricles.

CONCLUSION

Although a two-fold increased prevalence of a history of low birthweight and preterm birth exists within the special educational needs population, other aetiological factors must be considered for the overwhelming majority of cases. Neuroanatomical findings within this sample include qualitative anomalies of brain structure and grey matter deficits within temporal lobe structures and the cerebellum that persist into adolescence. These findings suggest a neurodevelopmental mechanism for the cognitive difficulties associated with these obstetric risk factors.

Different types of nutritional deficiencies affect different domains of spatial memory function checked in a radial arm maze

Several studies using animal models have suggested that the effects of nutritional insult on the developing brain are long-lasting and lead to permanent deficits in learning and behavior. Malnutrition can refer to the availability of all the nutrients but in insufficient quantities or it may imply that one or more of essential nutrients is either missing or is present, but in the wrong proportions in the diet. The hypothesis addressed in this study is that different domains of cognitive functioning can be affected by malnutrition and this can be related to the type of nutritional deficiency that the brain has been exposed to during development. To study the effect of nutritional deprivation during brain development, a paradigm of maternal malnutrition during the period of gestation and lactation was used and its effects were studied on the F1 offspring using Swiss albino mice. Three different types of malnutrition were used, that involve, caloric restriction, inadequate amount of protein in the diet and condition of low iron content. Our results show that the domain of spatial memory affected in the F1 generation depended on the kind of malnutrition that the mother was subjected to. Further our study shows that although hippocampal volume was reduced in all F1 pups, hippocampal subregions of the F1 animals were differentially vulnerable depending on type of malnutrition that the mother was subjected to. These results highlight the importance of qualifying the kind of malnutrition that is suffered by the mother during the period of gestation and lactation as it has consequences for the cognitive domain affected in the offspring. Awareness of this should inform prevention strategies in trying to reverse the effects of adverse maternal nutrition during critical periods in brain development.

White matter hyperintensities and their associations with suicidality in patients with major affective disorders

INTRODUCTION

A large body of evidence suggests that predisposition to suicide, an important public health problem, is mediated to a certain extent by neurobiological factors. The objective of this cross-sectional study was to compare the prevalence of white matter hyperintensities (WMH) in patients with major affective disorders with and without histories of suicide attempts.

METHODS

T2-weighted magnetic resonance images (MRI) of 65 psychiatric inpatients with major depressive disorder or bipolar disorder were rated for the presence of WMH. Diagnoses, presence or absence of suicide risk and substance abuse were determined by the Mini International Neuropsychiatric Interview (MINI). Medical charts were reviewed to ascertain history of suicide attempt and basic clinical variables. Fisher's Exact Tests and logistic regression modeling were used to test the association between WMH and suicidality. Suicidal patients and controls were not matched for demographic variables and exposure to some risk factors.

RESULTS

Bivariate analysis showed that the prevalence of WMH was significantly higher in subjects with past suicide attempts (Fisher's Exact Test, p = 0.01) and other clinical indicators of elevated suicide risk. Logistic regression analyses controlling for age, sex, and several clinical risk factors supported this finding (odds ratio = 4.7; 95% confidence interval: 1.4, 16.1).

CONCLUSIONS

The increased prevalence of WMH in adults with major affective disorders and a history of suicide attempt, compared to similar patients without such a history, is consistent with previous findings in depressed children, youth and young adults. However, the association between WMH and suicidality holds true for both, depressed and bipolar patients. Our results suggest that WMH in patients with major affective disorders might be useful biological markers of suicidality.

Gestational age at preterm birth in relation to corpus callosum and general cognitive outcome in adolescents

Prematurity is associated with corpus callosum abnormalities and low general cognitive functioning. The present study explores the specific relationship between gestational age, corpus callosum, and intelligence quotient (IQ) in a sample of preterm-born adolescents. Sixty-four adolescents born at a gestational age of 36 weeks or less were divided into 4 groups attending to their gestational age (GA) (group 1, < or = 27; group 2, 28-30; group 3, 31-33; group 4, 34-36). These individuals were compared with 53 adolescents born at term and of similar age, gender, and sociocultural status. Individuals born at a gestational age of 27 or less (group 1) presented a generalized corpus callosum reduction in the posterior part (posterior midbody, isthmus, and splenium) as well as in the anterior part (anterior midbody and genu), a reduced total white-matter volume, and a low Full-Scale IQ. Group 2 (GA between 28 and 30) also showed a low IQ, but corpus callosum reduction was only found in the splenium, without total white-matter volume reductions. Group 3 (GA between 31 and 33) did not present differences in corpus callosum size or a reduced total white- matter volume, but they showed a low Full-Scale IQ. Group 4 (GA between 34 and 36) did not show a smaller corpus callosum or a lower general cognitive performance. Specific significant correlations were found between corpus callosum subregions and gestational age. These results suggest the importance of gestational age in prematurity in relation to brain structural and functional outcome. Premature babies born at a gestational age of 27 weeks or less are the target group for long-term corpus callosum and white-matter anomalies and for a low IQ.

Clinical findings and white matter abnormalities seen on diffusion tensor imaging in adolescents with very low birth weight

Very low birth weight (VLBW) children are at high risk of perinatal white matter injury, which, when subtle, may not be seen using conventional magnetic resonance imaging. The relationship between clinical findings and fractional anisotropy (FA) measurements in white matter of adolescents born prematurely with VLBW was studied in 34 subjects (age = 15 years, birth weight </=1500 g) and 47 age-matched controls born at term, who were examined both clinically and with diffusion tensor imaging (DTI). Perceptual and cognitive functions were evaluated by visual motor integration (VMI) with supplementary tests and sub-tests from WISC-III, motor function by movement ABC and Grooved Pegboard test and psychiatric symptoms by the schedule for affective disorders and schizophrenia for school-age children semistructured interview, the Autism Spectrum Screening Questionnaire and attention deficit hyperactivity disorder (ADHD) rating scale IV. Overall functioning was scored on the children's global assessment scale. DTI scans were performed for calculation of FA maps and areas of significant differences in mean FA values between subjects and controls were compared with their clinical data. The VLBW children had reduced FA values in the internal and external capsule, corpus callosum and superior, middle superior and inferior fasciculus. Within this group of children, visual motor and visual perceptual deficits were associated with low FA values in the external capsule, posterior part of the internal capsule and in the inferior fasciculus. Children with low IQ had low FA values in the external capsule and inferior and middle superior fasciculus. Fine motor impairment was related to low FA values in the internal and external capsule and superior fasciculus. Eight VLBW children with inattention symptoms or a diagnosis of ADHD had significantly lower FA values in several areas. Mild social deficits correlated with reduced FA values in the external capsule and superior fasciculus. We conclude that DTI was able to detect differences in FA between VLBW adolescents and controls in several white matter areas at risk of periventricular leucomalacia in VLBW newborns. Our results show that low FA values in these areas were associated with perceptual, cognitive, motor and mental health impairments. These conclusions indicate that perinatal injury of white matter tracts persist with clinical significance in adolescence.

Epidemiology and burden of malaria in pregnancy

We reviewed evidence of the clinical implications and burden of malaria in pregnancy. Most studies come from sub-Saharan Africa, where approximately 25 million pregnant women are at risk of Plasmodium falciparum infection every year, and one in four women have evidence of placental infection at the time of delivery. P falciparum infections during pregnancy in Africa rarely result in fever and therefore remain undetected and untreated. Meta-analyses of intervention trials suggest that successful prevention of these infections reduces the risk of severe maternal anaemia by 38%, low birthweight by 43%, and perinatal mortality by 27% among paucigravidae. Low birthweight associated with malaria in pregnancy is estimated to result in 100,000 infant deaths in Africa each year. Although paucigravidae are most affected by malaria, the consequences for infants born to multigravid women in Africa may be greater than previously appreciated. This is because HIV increases the risk of malaria and its adverse effects, particularly in multigravidae, and recent observational studies show that placental infection almost doubles the risk of malaria infection and morbidity in infants born to multigravidae. Outside Africa, malaria infection rates in pregnant women are much lower but are more likely to cause severe disease, preterm births, and fetal loss. Plasmodium vivax is common in Asia and the Americas and, unlike P falciparum, does not cytoadhere in the placenta, yet, is associated with maternal anaemia and low birthweight. The effect of infection in the first trimester, and the longer term effects of malaria beyond infancy, are largely unknown and may be substantial. Better estimates are also needed of the effects of malaria in pregnancy outside Africa, and on maternal morbidity and mortality in Africa. Global risk maps will allow better estimation of potential impact of successful control of malaria in pregnancy.

Apoptosis and impairment of neurite network by short exposure of immature rat cortical neurons to unconjugated bilirubin increase with cell differentiation and are additionally enhanced by an inflammatory stimulus

Nerve cell injury induced by unconjugated bilirubin (UCB) has been implicated in brain damage during severe neonatal hyperbilirubinemia, although the molecular mechanisms underlying UCB neurotoxicity are still not clarified. It has been suggested recently that there is an association between hyperbilirubinemia and long-term neurologic dysfunctions. We incubated immature neurons with UCB to evaluate the short- and long-term effects of UCB on apoptotic death and on neuritic outgrowth and ramification. We also evaluated whether mature neurons, exposed previously to UCB in an early stage of differentiation, are more sensitive to apoptosis or to neuritic breakdown when treated with inflammatory agents, such as lipopolysaccharide and tumor necrosis factor-alpha. Results show that exposure of immature neurons to UCB increased apoptosis and provoked a reduction of both neurite extension and number of nodes. These injurious effects observed in immature cells treated with UCB were increasingly perpetuated along cell differentiation, as compared to neurons incubated in the absence of UCB. In addition, neurons that were exposed to UCB when immature showed an increased susceptibility to death by apoptosis, as well as an additional decrease in neurite outgrowth when incubated with an inflammatory agent afterward. This work shows, for the first time, that UCB induces neurite changes consistent with neurodevelopment abnormalities. Furthermore, pre-exposure to UCB followed by an inflammatory stimulus leads to an enhanced susceptibility to long-term apoptosis, as well as a greater neuritic breakdown. These data support the association between neonatal hyperbilirubinemia and the later development of mental illness, such as schizophrenia.

Sex Differences in the Pathway from Low Birth Weight to Inattention/hyperactivity

Inattention/hyperactivity is a childhood outcome of low birth weight. However, the mechanisms by which low birth weight leads to inattention/hyperactivity are unclear. This study examined arousal, activation, motor speed, and motor coordination as possible mechanisms, attending to sex differences. 823 children (400 males) from Detroit and surrounding suburbs were assessed with the Child Behavior Checklist and the Teacher Report Form and completed experimental tasks to assess vigilance and activation (Continuous Performance Test signal detection parameters) and motor output speed and control (Grooved Pegboard) at 6 years of age. The relationship between birth weight and inattention/hyperactivity was slightly, but not significantly, stronger for boys than for girls. Arousal, motor speed, and motor coordination significantly partially mediated the relationship between birth weight and inattention/hyperactivity for boys and girls. Moderated mediation was found for the pathway between motor coordination and inattention/hyperactivity such that this relationship was stronger for boys than for girls. Sex differences in the associated features of attention symptoms may reflect partially distinct etiological pathways.

Perinatal risk factors altering regional brain structure in the preterm infant

Neuroanatomical structure appears to be altered in preterm infants, but there has been little insight into the major perinatal risk factors associated with regional cerebral structural alterations. MR images were taken to quantitatively compare regional brain tissue volumes between term and preterm infants and to investigate associations between perinatal risk factors and regional neuroanatomical alterations in a large cohort of preterm infants. In a large prospective longitudinal cohort study of 202 preterm and 36 term infants, MR scans at term equivalent were undertaken for volumetric estimates of cortical and deep nuclear grey matter, unmyelinated and myelinated white matter (WM) and CSF within 8 parcellated regions for each hemisphere of the brain. Perinatal correlates analysed in relation to regional brain structure included gender, gestational age, intrauterine growth restriction, bronchopulmonary dysplasia, white matter injury (WMI) and intraventricular haemorrhage. Results revealed region-specific reductions in brain volumes in preterm infants compared with term controls in the parieto-occipital (preterm mean difference: -8.1%; 95% CI = -13.8--2.3%), sensorimotor (-11.6%; -18.2--5.0%), orbitofrontal (-30.6%; -49.8--11.3%) and premotor (-7.6%; -14.2--0.9%) regions. Within the sensorimotor and orbitofrontal regions cortical grey matter and unmyelinated WM were most clearly reduced in preterm infants, whereas deep nuclear grey matter was reduced mainly within the parieto-occipital and subgenual regions. CSF (ventricular and extracerebral) was doubled in volume within the superior regions in preterm infants compared with term controls. Cerebral WMI and intrauterine growth restriction were both associated with a more posterior reduction in brain volumes, whereas bronchopulmonary dysplasia was associated with a more global reduction across all regions. In contrast degree of immaturity was not related to regional brain structure among preterm infants. In summary, preterm birth is associated with regional cerebral tissue reductions, with the adverse pattern varying between risk factors. These findings add to our understanding of the potential pathways leading to altered brain structure and outcome in the preterm infant.

Heavy chain of cytoplasmic dynein is a major component of the postsynaptic density fraction

A protein with an apparent molecular size of 490 kDa was found in the postsynaptic density (PSD) fraction isolated from porcine cerebral cortices and rat forebrains, and this 490 kDa protein accounted for approximately 3% of the total protein of these samples. Matrix-assisted laser desorption ionization-time of flight mass spectrometric and Western blotting analyses consistently indicated that this 490 kDa protein consisted primarily of the heavy chain of cytoplasmic dynein (cDHC). Immunocytochemical analyses showed that cDHC was found in 92% and 89% of the phalloidin-positive protrusions that were themselves associated with discrete clusters of synaptophysin, a presynaptic terminal marker, and PSD-95, a postsynaptic marker, on neuronal processes, respectively. Quantitative Western blotting analyses of various subcellular fractions isolated from porcine cerebral cortices and rat forebrains further showed that not only the heavy but also the intermediate chains of dynein are enriched in the PSD fraction. Cytoplasmic dynein is a microtubule-associated motor protein complex that drives the movement of various cargos toward the minus ends of microtubules and plays many other diverse functions in the cell. Our results that cDHC is a major component of the PSD fraction, that both dynein heavy and intermediate chains are enriched in the PSD fraction and that cDHC is present in dendritic spines raise the possibilities that cytoplasmic dynein may play structural and functional roles in the postsynaptic terminal.

The role of chronic hypoxia in the development of neurocognitive abnormalities in preterm infants with bronchopulmonary dysplasia

Bronchopulmonary dysplasia is the most common pulmonary morbidity in preterm infants and is associated with chronic hypoxia. Animal studies have demonstrated structural, neurochemical and functional alterations due to chronic hypoxia in the developing brain. Long-term impairments in visual-motor, gross and fine motor, articulation, reading, mathematics, spatial memory and attention skills are prevalent in survivors of bronchopulmonary dysplasia, and impairments appear to correlate with the severity of hypoxia. However, due to the simultaneous occurrence of multiple neurodevelopmental risk factors, a primary or potentiating role for chronic hypoxia in these impairments has yet to be conclusively established.

Early risk, attention, and brain activation in adolescents born preterm

The relations among early cumulative medical risk, cumulative environmental risk, attentional control, and brain activation were assessed in 15-16-year-old adolescents who were born preterm. Functional magnetic resonance imaging found frontal, temporal, and parietal cortex activation during an attention task with greater activation of the left superior-temporal and left supramarginal gyri associated with better performance. Individual differences in early cumulative risk are related to patterns of brain activation such that medical risk is related to left parietal cortex activation and environmental risk is related to temporal lobe activation. The findings suggest that early risk is related to less mature patterns of brain activation, including reduced efficiency of processing and responding to stimuli.

Corpus callosum size and neuropsychologic impairment in adolescents who were born preterm

Prematurity is associated with cerebral abnormalities that might account for poorer cognitive performance. The aim of our study was to investigate the correlations between corpus callosum reductions and neuropsychologic performance in adolescents who were born preterm. Twenty-five subjects born before 33 weeks' gestation were compared with 25 subjects born at term and of similar age, gender, and sociocultural status. All subjects underwent magnetic resonance imaging and neuropsychologic examinations. Premature subjects performed worse than controls in global cognitive functioning, verbal memory, and verbal fluency. Corpus callosum measurements showed a global reduction owing mainly to thinning in the splenium, posterior midbody, and genu. Corpus callosum size significantly correlated with gestational age, Wechsler Performance IQ, and memory performance. These results suggest that cerebral growth during infancy does not compensate for corpus callosum reduction and that this reduction reflects neuropsychologic deficit. The cognitive impairment can arise from the paucity of the complex interneuronal connections owing to fiber damage, particularly myelinated fibers.

A “deficient environment” in prenatal life may compromise systems important for cognitive function by affecting BDNF in the hippocampus

The intrauterine environment has the capacity to mold the prenatal nervous system. Particularly, recent findings show that an adverse prenatal environment produces structural defects of the hippocampus, a critical area sub-serving learning and memory functions. These structural changes are accompanied by a disruption in the normal expression pattern of brain-derived neurotrophic factor (BDNF) and its cognate tyrosine kinase B (TrkB) receptor. The important role that the BDNF system plays in neural modeling and learning and memory processes suggests that fetal exposure to unfavorable intrauterine conditions may compromise proper cognitive function in adult life. These findings have implications for disorders that involve a dysfunction in the BDNF system and are accompanied by cognitive deficits.

Metabolic consequences of hypoxia from birth and dexamethasone treatment in the neonatal rat: comprehensive hepatic lipid and fatty acid profiling

Neonatal hypoxia is a common condition resulting from pulmonary and/or cardiac dysfunction. Dexamethasone therapy is a common treatment for many causes of neonatal distress, including hypoxia. The present study examined the effects of dexamethasone treatment on both normoxic and hypoxic neonatal rats. We performed comprehensive hepatic fatty acid/lipid profiling and evaluated changes in pertinent plasma hormones and lipids and a functional hepatic correlate, i.e. hepatic lipase activity. Rats were exposed to hypoxia from birth to 7 d of age. A 4-d tapering dose regimen of dexamethasone was administered on: postnatal day (PD)3 (0.5 mg/kg), PD4 (0.25 mg/kg), PD5 (0.125 mg/kg), and PD6 (0.05 mg/kg). The most significant finding was that dexamethasone attenuated nearly all hypoxia-induced changes in hepatic lipid profiles. Hypoxia increased the concentration of hepatic triacylglyceride and free fatty acids and, more specifically, increased a number of fatty acid metabolites within these lipid classes. Administration of dexamethasone blocked these increases. Hypoxia alone increased the plasma concentration of cholesterol and triacylglyceride, had no effect on plasma glucose, and only tended to increase plasma insulin. Dexamethasone administration to hypoxic pups resulted in an additional increase in plasma lipid concentrations, an increase in insulin, and a decrease in plasma glucose. Hypoxia and dexamethasone treatment each decreased total hepatic lipase activity. Normoxic pups treated with dexamethasone displayed increased plasma lipids and insulin. The effects of dexamethasone on hepatic function in the hypoxic neonate are dramatic and have significant implications in the assessment and treatment of metabolic dysfunction in the newborn.