Selective vulnerability in the neonatal brain

Enteral plasma supports brain repair in newborn pigs after birth asphyxia

Newborns exposed to birth asphyxia transiently experience deficient blood flow and a lack of oxygen, potentially inducing hypoxic-ischaemic encephalopathy and subsequent neurological damage. Immunomodulatory components in plasma may dampen these responses. Using caesarean-delivered pigs as a model, we hypothesized that dietary plasma supplementation improves brain outcomes in pigs exposed to birth asphyxia. Mild birth asphyxia was induced by temporary occlusion of the umbilical cord prior to caesarean delivery. Motor development was assessed in asphyxiated (ASP) and control (CON) piglets using neonatal arousal, physical activity and gait test parameters before euthanasia on Day 4. The ASP pigs exhibited increased plasma lactate at birth, deficient motor skills and increased glial fibrillary acidic protein levels in CSF and astrogliosis in the putamen. The expression of genes related to oxidative stress, inflammation and synaptic functions was transiently altered in the motor cortex and caudate nucleus. The number of apoptotic cells among CTIP2-positive neurons in the motor cortex and striatal medium spiny neurons was increased, and maturation of preoligodendrocytes in the internal capsule was delayed. Plasma supplementation improved gait performance in the beam test, attenuated neuronal apoptosis and affected gene expression related to neuroinflammation, neurotransmission and antioxidants (motor cortex, caudate). We present a new clinically relevant animal model of moderate birth asphyxia inducing structural and functional brain damage. The components in plasma that support brain repair remain to be identified but may represent a therapeutic potential for infants and animals after birth asphyxia.

Proteasome localization and activity in pig brain and in vivo small molecule screening for activators

Introduction

Loss of proteasome function, proteinopathy, and proteotoxicity may cause neurodegeneration across the human lifespan in several forms of brain injury and disease. Drugs that activate brain proteasomes in vivo could thus have a broad therapeutic impact in neurology.

Methods

Using pigs, a clinically relevant large animal with a functionally compartmental gyrencephalic cerebral cortex, we evaluated the localization and biochemical activity of brain proteasomes and tested the ability of small molecules to activate brain proteasomes.

Results

By Western blotting, proteasome protein subunit PSMB5 and PSMA3 levels were similar in different pig brain regions. Immunohistochemistry for PSMB5 showed localization in the cytoplasm (diffuse and particulate) and nucleus (cytoplasm < nucleus). Some PSMB5 immunoreactivity was colocalized with mitochondrial (voltage-gated anion channel and cyclophilin D) and cell death (Aven) proteins in the neuronal soma and neuropil in the neocortex of pig and human brains. In the nucleus, PSMB5 immunoreactivity was diffuse, particulate, and clustered, including perinucleolar decorations. By fluorogenic assay, proteasome chymotrypsin-like activities (CTL) in crude tissue soluble fractions were generally similar within eight different pig brain regions. Proteasome CTL activity in the hippocampus was correlated with activity in nasal mucosa biopsies. In pilot analyses of subcellular fractions of pig cerebral cortex, proteasome CTL activity was highest in the cytosol and then ~50% lower in nuclear fractions; ~15-20% of total CTL activity was in pure mitochondrial fractions. With in-gel activity assay, 26S-singly and -doubly capped proteasomes were the dominant forms in the pig cerebral cortex. With a novel in situ histochemical activity assay, MG132-inhibitable proteasome CTL activity was localized to the neuropil, as a mosaic, and to cell bodies, nuclei, and centrosome-like perinuclear satellites. In piglets treated intravenously with pyrazolone derivative and chlorpromazine over 24 h, brain proteasome CTL activity was modestly increased.

Discussion

This study shows that the proteasome in the pig brain has relative regional uniformity, prominent nuclear and perinuclear presence with catalytic activity, a mitochondrial association with activity, 26S-single cap dominance, and indications from small molecule systemic administration of pyrazolone derivative and chlorpromazine that brain proteasome function appears safely activable.

Microglia and Stem-Cell Mediated Neuroprotection after Neonatal Hypoxia-Ischemia

Neonatal hypoxia-ischemia encephalopathy (HIE) refers to a brain injury in term infants that can lead to death or lifelong neurological deficits such as cerebral palsy (CP). The pathogenesis of this disease involves multiple cellular and molecular events, notably a neuroinflammatory response driven partly by microglia, the brain resident macrophages. Treatment options are currently very limited, but stem cell (SC) therapy holds promise, as beneficial outcomes are reported in animal studies and to a lesser degree in human trials. Among putative mechanisms of action, immunomodulation is considered a major contributor to SC associated benefits. The goal of this review is to examine whether microglia is a cellular target of SC-mediated immunomodulation and whether the recruitment of microglia is linked to brain repair. We will first provide an overview on microglial activation in the rodent model of neonatal HI, and highlight its sensitivity to developmental age. Two complementary questions are then addressed: (i) do immune-related treatments impact microglia and provide neuroprotection, (ii) does stem cell treatment modulates microglia? Finally, the immune-related findings in patients enrolled in SC based clinical trials are discussed. Our review points to an impact of SCs on the microglial phenotype, but heterogeneity in experimental designs and methodological limitations hamper our understanding of a potential contribution of microglia to SC associated benefits. Thorough analyses of the microglial phenotype are warranted to better address the relevance of the neuroimmune crosstalk in brain repair and improve or advance the development of SC protocols in humans.

Neuroprotection in the Striatum of Hypoxic-Ischemic Piglets by Simultaneous Inhibition of Dopamine D1 and Adenosine A2A Receptors

INTRODUCTION

Striatal neurons of term newborns are highly vulnerable to hypoxia-ischemia (H-I). In a piglet model of H-I, a dopamine D1 receptor antagonist and an adenosine A2A receptor antagonist alone preferentially protect striatonigral and striatopallidal neurons, respectively. Here, we tested the hypothesis whether the combined treatment with SCH23390, a D1 receptor antagonist, and SCH58261, an A2A receptor antagonist, is more efficacious than individual D1 and A2A receptor antagonist treatment.

METHODS

Anesthetized newborn piglets were subjected to sham operation (n = 6) or 40 min of hypoxia and 7 min of airway occlusion. At 5 min of reoxygenation, piglets received the vehicle, SCH23390, SCH58261, or the combined treatment (n = 9 in each group). At 4 days of recovery, the number of viable neurons in the entire putamen was estimated by unbiased stereology.

RESULTS

Stereological results showed that sham-operated piglets had an estimated 2.9 × 106 neurons in the putamen, and the number of viable neurons in hypoxic-ischemic piglets was significantly reduced by 80% to 0.6 × 106/putamen. Treatment with SCH23390, SCH58261, and the combination increased the numbers of viable neurons to 1.4 × 106/putamen, 1.4 × 106/putamen, and 2.1 × 106/putamen, respectively. Notably, the combined treatment improved neuroprotection compared to individual therapy.

CONCLUSION

We conclude that simultaneous inhibition of dopamine D1 receptors and adenosine A2A receptors saves more neurons than individual treatment in the highly vulnerable putamen of a large-animal neonatal H-I model.

Sulforaphane Protects Piglet Brains from Neonatal Hypoxic-Ischemic Injury

The striatal, primary sensorimotor cortical, and thalamic neurons are highly vulnerable to hypoxia-ischemia (HI) in term newborns. In a piglet model of HI that exhibits similar selective regional vulnerability, we tested the hypothesis that early treatment with sulforaphane, an activator of the Nrf2 transcription factor, protects vulnerable neurons from HI injury. Anesthetized piglets (aged 3-7 days) were subjected to 45 min of hypoxia and 7 min of airway occlusion. At 15 min after resuscitation, the piglets received intravenous vehicle or sulforaphane. At 4 days of recovery, the density of viable neurons in the putamen of vehicle-treated piglets was 31 ± 34% (±SD) that of sham-operated controls. Treatment with sulforaphane significantly increased viability to 77 ± 31%. In the sensorimotor cortex, neuronal viability was also increased; it was 59 ± 35% in the vehicle-treated and 89 ± 15% in the sulforaphane-treated animals. Treatment with sulforaphane increased the nuclear Nrf2 and γ-glu-tamylcysteine synthetase expression at 6 h of recovery in these regions. We conclude that systemic administration of sulforaphane 15 min after HI can induce the translocation of Nrf2 to the nucleus, increase expression of an enzyme involved in glutathione synthesis, and salvage neurons in the highly vulnerable putamen and sensorimotor cortex in a large-animal model of HI. Therefore, targeting Nrf2 activation soon after recovery from HI is a feasible approach for neuroprotection in the newborn brain.

Markers of perinatal hypoxia-ischaemia and neurological injury: assessing the impact of insult duration

Hypoxic-ischaemic insults occurring during or after birth can cause both acute and long-term neurological impairment. The duration of the insult is a critical factor, but most published reports of duration have important limitations. After the onset of a persistent bradycardia in 125 term born infants, abnormal outcomes occurred in two by 10 minutes, in 12 out of 47 (26%) delivered between 11 and 20 minutes, and in 55 out of 65 (85%) delivered after 20 minutes. Series with unspecified gestation or including infants born preterm give comparable results in over 500 additional cases. Before 20 minutes there was little correlation with severity, while after 20 minutes most were severely impaired. Limited neuroimaging data suggest that damage restricted to the basal ganglia and thalamus may begin to occur after 10 minutes, associated Rolandic damage after 15 minutes, and other cortical involvement after 20 minutes. Associated white matter damage can occur after any duration. There were little data for other patterns of damage. WHAT THIS PAPER ADDS: Some term born infants can withstand 20 minutes of fetal bradycardia without acute or chronic damage. Durations in humans are not the same as in animal models.

Perinatal hypoxic-ischemic brain injury in large animal models: Relevance to human neonatal encephalopathy

Perinatal hypoxia-ischemia resulting in death or lifelong disabilities remains a major clinical disorder. Neonatal models of hypoxia-ischemia in rodents have enhanced our understanding of cellular mechanisms of neural injury in developing brain, but have limitations in simulating the range, accuracy, and physiology of clinical hypoxia-ischemia and the relevant systems neuropathology that contribute to the human brain injury pattern. Large animal models of perinatal hypoxia-ischemia, such as partial or complete asphyxia at the time of delivery of fetal monkeys, umbilical cord occlusion and cerebral hypoperfusion at different stages of gestation in fetal sheep, and severe hypoxia and hypoperfusion in newborn piglets, have largely overcome these limitations. In monkey, complete asphyxia produces preferential injury to cerebellum and primary sensory nuclei in brainstem and thalamus, whereas partial asphyxia produces preferential injury to somatosensory and motor cortex, basal ganglia, and thalamus. Mid-gestational fetal sheep provide a valuable model for studying vulnerability of progenitor oligodendrocytes. Hypoxia followed by asphyxia in newborn piglets replicates the systems injury seen in term newborns. Efficacy of post-insult hypothermia in animal models led to the success of clinical trials in term human neonates. Large animal models are now being used to explore adjunct therapy to augment hypothermic neuroprotection.

Pathogenesis, neuroimaging and management in children with cerebral palsy born preterm

With advances in obstetric and perinatal management, the incidence of intraventricular hemorrhage in premature infants has declined, while periventricular leukomalacia remains a significant concern. It is now known that brain injury in children born preterm also involves neuronal-axonal disease in supratentorial and infratentorial structures. The developing brain is especially vulnerable to white matter (WM) injury from 23 to 34 weeks gestation when blood vessels serving the periventricular WM are immature. Oligodendrocyte progenitors, which are beginning to form myelin during this time, are susceptible to attack from oxygen free radicals, glutamate, and inflammatory cytokines. Advances in imaging techniques such as diffusion tensor imaging provide a more complete picture of the location and extent of injury. Effective management of children born preterm with cerebral palsy is predicated on an understanding of sequential links from etiological antecedents to brain neuropathology as revealed with neuroimaging techniques to clinical phenotypes, toward focused interventions with measurable outcomes.

Neuroprotective effect of melatonin: a novel therapy against perinatal hypoxia-ischemia

One of the most common causes of mortality and morbidity in children is perinatal hypoxia-ischemia (HI). In spite of the advances in neonatology, its incidence is not diminishing, generating a pediatric population that will require an extended amount of chronic care throughout their lifetime. For this reason, new and more effective neuroprotective strategies are urgently required, in order to minimize as much as possible the neurological consequences of this encephalopathy. In this sense, interest has grown in the neuroprotective possibilities of melatonin, as this hormone may help to maintain cell survival through the modulation of a wide range of physiological functions. Although some of the mechanisms by which melatonin is neuroprotective after neonatal asphyxia remain a subject of investigation, this review tries to summarize some of the most recent advances related with its use as a therapeutic drug against perinatal hypoxic-ischemic brain injury, supporting the high interest in this indoleamine as a future feasible strategy for cerebral asphyctic events.

Endocannabinoids reduce cerebral damage after hypoxic-ischemic injury in perinatal rats

Hypoxic-ischemic (HI) insult during the perinatal period remains as one of the most common causes of brain injury and produces long-term neurological deficits, and there is a growing need for effective therapies. The aim of the present work was to perform a prospective study designed to assess the possible protector effect of two endocannabinoids: 2-arachidonoylglycerol (2AG) and anandamide (AEA) in the brain after HI injury in perinatal rat model. We evaluate their effects on cell death and check several cellular parameters. 7-days-old Wistar rats were assigned to four different experimental groups (n=7-10): Sham, HI, and HI treated with 2AG or AEA. The injury was induced by the left carotid artery ligature and subsequent exposure to 8% O(2) for 120 min. Immediately after the injury, treated groups received a single dose of 2AG (1mg/kg) or AEA (5mg/kg) and then animals were sacrificed 24, 72 h or 7 days after the HI event. Brains fixed by perfusion were stained with Nissl for morphological studies, and non-fixed brains were dissociated and analyzed by flow cytometry to quantify apoptosis, mitochondrial state, intracellular calcium and reactive oxygen species. Our results show that both 2AG and AEA have beneficial effects after HI injury in this rat model, producing a remarkable amelioration of brain injury, reducing apoptotic cell death, contributing to the maintenance of mitochondrial functionality, and improving cellular parameters such as the influx of calcium and ROS production.

Correlation between periventricular leukomalacia and retinopathy of prematurity

PURPOSE

To investigate the correlation between periventricular leukomalacia (PVL) and retinopathy of prematurity (ROP), which are complications of perinatal and postnatal hypoxic-ischemic insults in premature infants.

METHODS

In this retrospective case series study, from 1996 to 2008, after excluding cases with follow-up of less than 3 months, we reviewed medical charts of babies who had gestational age (GA) less than 30 weeks or birthweight (BW) less than 2000 g. A total of 195 patients were diagnosed with ROP and/or PVL and were enrolled in this analysis. We investigated the correlation between ROP and PVL with Pearson chi-square test and evaluated BW, GA, and Apgar scores at 1 minute and 5 minutes after birth as risk factors by independent t test.

RESULTS

There were no significant differences in the prevalence of PVL between patients who received ROP treatment and those who did not receive ROP treatment. The BW was significantly lower in patients with PVL than in patients without PVL. Gestational age, BW, and Apgar scores significantly differed between patients who did and did not receive retinal treatment for ROP.

CONCLUSIONS

Periventricular leukomalacia did not increase the severity of ROP or requirement of ROP treatment. Birthweight, GA, and Apgar scores were the principal factors that determined the necessity of ROP treatment.

Effect of granulocyte-colony stimulating factor on expression of selected proteins involved in regulation of apoptosis in the brain of newborn piglets after cardiopulmonary bypass and deep hypothermic circulatory arrest

OBJECTIVE

The study objective was to investigate the effect of granulocyte-colony stimulating factor on the expression of proteins that regulate apoptosis in newborn piglet brain after cardiopulmonary bypass and deep hypothermic circulatory arrest.

METHODS

The newborn piglets were assigned to 3 groups: (1) deep hypothermic circulatory arrest (30 minutes of deep hypothermic circulatory arrest, 1 hour of low-flow cardiopulmonary bypass); (2) deep hypothermic circulatory arrest with prior injection of granulocyte-colony stimulating factor (17 μg/kg 2 hours before cardiopulmonary bypass); and (3) sham-operated. After 2 hours of post-bypass recovery, the frontal cortex, striatum, and hippocampus were dissected. The expression of proteins was measured by gel electrophoresis or protein arrays. Data are presented in arbitrary units. Statistical analysis was performed using 1-way analysis of variance.

RESULTS

In the frontal cortex, only Fas ligand expression was significantly lower in the granulocyte-colony stimulating factor group when compared with the deep hypothermic circulatory arrest group. In the hippocampus, granulocyte-colony stimulating factor increased Bcl-2 (54.3 ± 6.4 vs 32.3 ± 2.2, P = .001) and serine/threonine-specific protein kinase (141.4 ± 19 vs 95.9 ± 21.1, P = .047) when compared with deep hypothermic circulatory arrest group. Caspase-3, Bax, Fas, Fas ligand, death receptor 6, and Janus protein tyrosine kinase 2 levels were unchanged. The Bcl-2/Bax ratio was 0.33 for deep hypothermic circulatory arrest group and 0.93 for the granulocyte-colony stimulating factor group (P = .02). In the striatum, when compared with the deep hypothermic circulatory arrest group, the granulocyte-colony stimulating factor group had higher levels of Bcl-2 (50.3 ± 7.4 vs 31.8 ± 3.8, P = .01), serine/threonine-specific protein kinase (132.7 ± 12.3 vs 14 ± 1.34, P = 2.3 × 10(6)), and Janus protein tyrosine kinase 2 (126 ± 17.4 vs 77.9 ± 13.6, P = .011), and lower levels of caspase-3 (12.8 ± 5.0 vs 32.2 ± 11.5, P = .033), Fas (390 ± 31 vs 581 ± 74, P = .038), Fas ligand (20.5 ± 11.5 vs 57.8 ± 15.6, P = .04), and death receptor 6 (57.4 ± 4.4 vs 108.8 ± 13.4, P = .007). The Bcl-2/Bax ratio was 0.25 for deep hypothermic circulatory arrest and 0.44 for the granulocyte-colony stimulating factor groups (P = .046).

CONCLUSIONS

In the piglet model of hypoxic brain injury, granulocyte-colony stimulating factor decreases proapoptotic signaling, particularly in the striatum.

Striatal neuroprotection from neonatal hypoxia-ischemia in piglets by antioxidant treatment with EUK-134 or edaravone

Striatal neurons are highly vulnerable to hypoxia-ischemia (HI) in term newborns. In a piglet model of HI, striatal neurons develop oxidative stress and organelle disruption by 3-6 h of recovery and ischemic cytopathology over 6-24 h of recovery. We tested the hypothesis that early treatment with the antioxidants EUK-134 (a manganese-salen derivative that acts as a scavenger of superoxide, hydrogen peroxide, nitric oxide or NO and peroxynitrite) or edaravone (MCI-186, a scavenger of hydroxyl radical and NO) protects striatal neurons from HI. Anesthetized newborn piglets were subjected to 40 min of hypoxia and 7 min of airway occlusion. At 30 min after resuscitation, the piglets received vehicle, EUK-134 or edaravone. Drug treatment did not affect arterial blood pressure, blood gases, blood glucose or rectal temperature. At 4 days of recovery, the density of viable neurons in the putamen of vehicle-treated piglets was 12 ± 6% (±SD) of sham-operated control density. Treatment with EUK-134 increased viability to 41 ± 17%, and treatment with edaravone increased viability to 39 ± 19%. In the caudate nucleus, neuronal viability was increased from 54 ± 11% in the vehicle group to 78 ± 15% in the EUK-134 group and to 73 ± 13% in the edaravone group. Antioxidant drug treatment accelerated recovery from neurologic deficits and decreased oxidative and nitrative damage to nucleic acids. Treatment with EUK-134 reduced the HI-induced formation of protein carbonyl groups and tyrosine nitration at 3 h of recovery. We conclude that systemic administration of antioxidant agents by 30 min after resuscitation from HI can reduce oxidative stress and salvage neurons in the highly vulnerable striatum in a large-animal model of neonatal HI. Therefore, oxidative stress is an important mechanism for this injury, and antioxidant therapy is a rational, mechanism-based approach to neuroprotection in the newborn brain.

Neuronal cell death in neonatal hypoxia-ischemia

Perinatal hypoxic-ischemic encephalopathy (HIE) is a significant cause of mortality and morbidity in infants and young children. Therapeutic opportunities are very limited for neonatal and pediatric HIE. Specific neural systems and populations of cells are selectively vulnerable in HIE; however, the mechanisms of degeneration are unresolved. These mechanisms involve oxidative stress, excitotoxicity, inflammation, and the activation of several different cell death pathways. Decades ago the structural and mechanistic basis of the cellular degeneration in HIE was thought to be necrosis. Subsequently, largely due to advances in cell biology and to experimental animal studies, emphasis has been switched to apoptosis or autophagy mediated by programmed cell death (PCD) mechanisms as important forms of degeneration in HIE. We have conceptualized based on morphological and biochemical data that this degeneration is better classified according to an apoptosis-necrosis cell death continuum and that programmed cell necrosis has prominent contribution in the neurodegeneration of HIE in animal models. It is likely that neonatal HIE evolves through many cell death chreodes influenced by the dynamic injury landscape. The relevant injury mechanisms remain to be determined in human neonatal HIE, though preliminary work suggests a complexity in the cell death mechanisms greater than that anticipated from experimental animal models. The accurate identification of the various cell death chreodes and their mechanisms unfolding within the immature brain matrix could provide fresh insight for developing meaningful therapies for neonatal and pediatric HIE.

Early regional response of apoptotic activity in newborn piglet brain following hypoxia and ischemia

Responses of selected neuroregulatory proteins that promote (Caspase 3 and Bax) or inhibit (Bcl-2, high Bcl-2/Bax ratio) apoptotic cell death were measured in the brain of piglets subjected to precisely controlled hypoxic and ischemic insults: 1 h hypoxia (decreasing FiO₂ from 21 to 6%) or ischemia (ligation of carotid arteries and hemorrhage), followed by 0, 2 and 4 h recovery with 21% FiO₂. Protein expression was measured in cortex, hippocampus and striatum by Western blot. There were no significant differences in expression of Caspase-3 between sham operated, hypoxic and ischemic groups. There were significant regional differences in expression of Bcl-2 and Bax in response to hypoxia and ischemia. The changes in Bcl-2/Bax ratio were similar for hypoxia and ischemia except for striatum at zero time recovery, with ischemia giving lower ratios than hypoxia. The Bcl-2/Bax ratio was also lower for the striatum than for the other regions of the brain, suggesting this region is the more susceptible to apoptotic injury.

Redox control in mammalian embryo development

The development of an embryo constitutes a complex choreography of regulatory events that underlies precise temporal and spatial control. Throughout this process the embryo encounters ever changing environments, which challenge its metabolism. Oxygen is required for embryogenesis but it also poses a potential hazard via formation of reactive oxygen and reactive nitrogen species (ROS/RNS). These metabolites are capable of modifying macromolecules (lipids, proteins, nucleic acids) and altering their biological functions. On one hand, such modifications may have deleterious consequences and must be counteracted by antioxidant defense systems. On the other hand, ROS/RNS function as essential signal transducers regulating the cellular phenotype. In this context the combined maternal/embryonic redox homeostasis is of major importance and dysregulations in the equilibrium of pro- and antioxidative processes retard embryo development, leading to organ malformation and embryo lethality. Silencing the in vivo expression of pro- and antioxidative enzymes provided deeper insights into the role of the embryonic redox equilibrium. Moreover, novel mechanisms linking the cellular redox homeostasis to gene expression regulation have recently been discovered (oxygen sensing DNA demethylases and protein phosphatases, redox-sensitive microRNAs and transcription factors, moonlighting enzymes of the cellular redox homeostasis) and their contribution to embryo development is critically reviewed.

Autism spectrum disorders in survivors of extreme prematurity

Recent studies in survivors of extreme prematurity point to an increased prevalence of a previously underrecognized atypical social-behavioral profile strongly suggestive of an autism spectrum disorder. Prospective studies that incorporate early autism screening and autism diagnostic testing are needed to better delineate the sensitivity and specificity of early signs of autism in ex-premature children. Advances in neonatal MRI techniques capable of quantitative structural and functional measurements will also provide important insights into the effects of prematurity itself, and prematurity-related brain injury on the genesis of autism spectrum disorders in this population. Available evidence linking prematurity and autism spectrum disorders is reviewed in this article.

Placental HIFs as markers of cerebral hypoxic distress in fetal mice

Reduced oxygen supply during the pre- and perinatal period often leads to acquired neonatal brain damage. So far, there are no reliable markers available to assess the hypoxic cerebral damage and the resulting prognosis during the immediate postnatal period. Thus we aimed to determine whether the hypoxia-inducible transcription factors (HIF-1 and HIF-2) and/or their target genes in the placenta represent reliable indicators of hypoxic distress of the developing brain during systemic hypoxia at the end of gestation. To this end, pregnant mice were exposed to systemic hypoxia (inspired O2 fraction: 6%, 6 h) at gestational day 20. This hypoxic exposure significantly increased HIF-1α and HIF-2α protein levels in brain and placental tissue. Compared with normoxic controls, an increase of HIF-1α-immunoreactive neurons and HIF-2α-positive glial cells and vascular endothelial cells was observed in hypoxic cerebral cortex and hippocampus. In placenta, HIF-1α and HIF-2α were expressed in labyrinthine layer with increased staining intensity during hypoxia compared with normoxia. Significant upregulation of VEGF mRNA and protein in brain and placenta, as well as erythropoietin protein in placenta, indicated activity of the HIF system upon fetal hypoxia. Notably, hypoxia did not affect expression of the HIF target genes inducible nitric oxide synthase and GLUT-1. Taken together, at gestational day 20, systemic hypoxia led to upregulation of HIF-α in mouse brain that was temporally paralleled in placenta, implying that α-subunits of both HIF-1 and HIF-2 are indeed early markers of hypoxic distress in vivo. If our data reflect the situation in humans, analysis of the placenta will allow early identification of the hypoxic brain distress occurring near birth.

Rapid NMDA receptor phosphorylation and oxidative stress precede striatal neurodegeneration after hypoxic ischemia in newborn piglets and are attenuated with hypothermia

The basal ganglia of newborns are extremely vulnerable to hypoxic ischemia (HI). Striatal neurons undergo prominent necrosis after HI. The mechanisms for this degeneration are not well understood. Postasphyxic hypothermia ameliorates the striatal necrosis, but the mechanisms of hypothermia-induced neuroprotection are not known. We used a newborn piglet model of hypoxic-asphyxic cardiac arrest to test the hypotheses that N-methyl-d-aspartate receptor activation and free radical damage coexist, prior to neurodegeneration, early after resuscitation, and that these changes are attenuated with hypothermia. Piglets were subjected to 30min of hypoxia followed by 7min of airway occlusion, causing asphyxic cardiac arrest, and then were resuscitated and survived normothermically for 5min, 3h, or 6h, or hypothermically for 3h. By 6h of normothermic recovery, 50% of neurons in putamen showed ischemic cytopathology. Striatal tissue was fractionated into membrane or soluble proteins and was assayed by immunoblotting for carbonyl modification, phosphorylation of the N-methyl-d-aspartate receptor subunit NR1, and neuronal nitric oxide synthase. Significant accumulation of soluble protein carbonyls was present at 3h (196% of control) and 6h (142% of control). Phosphorylation of serine-897 of NR1 was increased significantly at 5min (161% of control) and 3h (226% of control) after HI. Phosphorylation of serine-890 of NR1 was also increased after HI. Membrane-associated neuronal nitric oxide synthase was increased by 35% at 5min. Hypothermia attenuated the oxidative damage and the NR1 phosphorylation in striatum. We conclude that neuronal death signaling in newborn striatum after HI is engaged rapidly through N-methyl-d-aspartate receptor activation, neuronal nitric oxide synthase recruitment, and oxidative stress. Postasphyxic, mild whole body hypothermia provides neuroprotection by suppressing N-methyl-d-aspartate receptor phosphorylation and protein oxidation.

Early cell death in the brain of fetal preterm lambs after hypoxic-ischemic injury

The objective of the present study was to evaluate using premature fetal lambs the effect of cerebral hypoxia-ischemia induced by partial occlusion of the umbilical cord on the type of cell death which occurs in different brain regions and to ascertain some of the neural pathways which may underlie the associated pathologies. Lambs were sacrificed either immediately after a 1 h hypoxic-ischemic insult or 3 h later. Brains were fixed by perfusion and blocks of the different brain territories were processed for light microscopy (hematoxylin-eosin, Nissl staining), electron transmission microscopy and quantification of apoptosis by the TUNEL method. Other fixed brains were dissociated and labeled by nonyl acridine orange to determine mitochondrial integrity. Non-fixed brains were also used for membrane asymmetry studies, in which cell suspensions were analyzed by flow cytometry to quantify apoptosis. In both hypoxic-ischemic groups, necrotic-like neurons were observed mainly in the mesencephalon, pons, deep cerebellar nuclei and basal nuclei, whereas apoptotic cells were extensively found both in white and gray matter and were not limited to regions where necrotic neurons were present. The 3 h post-partial cord occlusion group, but not the 0 h group, showed a generalized alteration of cell membrane asymmetry and mitochondrial integrity as revealed by Annexin V/PI flow cytometry and nonyl acridine orange studies, respectively. Our results show that the apoptotic/necrotic patterns of cell death occurring early after hypoxic-ischemic injury are brain-region-specific and have distinct dynamics and suggest that therapeutic strategies aimed at rescuing cells from the effects of hypoxia/ischemia should be aimed at blocking the apoptotic components of brain damage.

Hypoxia-induced Cell Death and Activation of Pro- and Anti-apoptotic Proteins in Developing Chick Optic Lobe

Exposure of the CNS to hypoxia is associated with cell death. Our aim was to establish a temporal correlation between cellular and molecular alterations induced by an acute hypoxia evaluated at different post-hypoxia (p-h) times and at two stages of chick optic lobe development: embryonic days (ED) 12 and 18. TUNEL assays at ED12 disclosed a significant increase (300%) in pyknotic cells at 6 h p-h, while at ED18 no morphological changes were observed in hypoxic versus controls. At ED12 there was a significant increase (48%) in Bcl-2 levels at the end of the hypoxic treatment, followed by a significant increase of active caspase-9 (49%) and active caspase-3 (58%) at 30 and 60 min p-h, respectively, while at ED18 no significant changes were observed. These findings indicate that prenatal hypoxia produces an equilibrated imbalance in both pro- and anti-apoptotic proteins that culminates in a process of cell death, present at earlier stages of development.

Early continuous video-EEG in acute near-total intrauterine asphyxia

The evolution of electroencephalographic changes after acute hypoxic-ischemic injury is poorly understood, as a clear time of insult is often absent and continuous electroencephalographic monitoring in the first 3 days after such injury has not been previously reported. Infants who suffer sudden profound asphyxia, often termed "acute near-total intrauterine asphyxia", have evidence of damage to the deep gray matter. In these infants it is possible to time the onset and duration of cerebral ischemia. This report describes early continuous video-electroencephalography from 3 hours after birth in an infant with the characteristic clinical and radiologic features of acute near-total intrauterine asphyxia.

Antegrade cerebral perfusion reduces apoptotic neuronal injury in a neonatal piglet model of cardiopulmonary bypass

OBJECTIVE

Neonates with congenital heart disease might require surgical repair with deep hypothermic circulatory arrest, a technique associated with adverse neurodevelopmental outcomes. Antegrade cerebral perfusion is thought to minimize ischemic brain injury, although there are no supporting experimental data. We sought to evaluate and compare the extent of neurologic injury in a neonatal piglet model of deep hypothermic circulatory arrest and antegrade cerebral perfusion.

METHODS

Neonatal piglets undergoing cardiopulmonary bypass were randomized to deep hypothermic circulatory arrest or antegrade cerebral perfusion for 45 minutes. Animals were killed after 6 hours of recovery, and brain tissue was stained for evidence of cellular injury and for the apoptotic markers activated caspase 3 and cytochrome c translocation from mitochondria to cytosol.

RESULTS

Piglets from the antegrade cerebral perfusion group exhibited less apoptotic or necrotic injury (4 +/- 3 vs 29 +/- 12 cells per field, P = .03). The piglets undergoing antegrade cerebral perfusion also had less evidence of apoptosis, with fewer cells staining for activated caspase 3 (57 +/- 8 vs 93 +/- 9 cells per field, P = .001) or showing cytochrome c translocation (6 +/- 2 vs 15 +/- 4 cells per field, P = .02).

CONCLUSIONS

The use of antegrade cerebral perfusion in place of deep hypothermic circulatory arrest reduces evidence of apoptosis and histologic injury in neonatal piglets. Neonates with congenital heart disease might benefit from antegrade cerebral perfusion during complex cardiac surgery to improve their overall neurologic outcome.

Vermis and lateral lobes of the cerebellum in adolescents born very preterm

Adolescents born before 33 weeks' gestation have reduced cerebellar volume compared with term-born controls, and this is related to their cognitive performance. We wished to determine whether this relationship is regionally specific. We measured midline and lateral cerebellar volumes in magnetic resonance imaging scans from 67 very preterm adolescents and 50 term-born controls at 14-15 years. Volumes of vermis and lateral lobes were reduced in the preterm group, after controlling for whole-brain volume. Lateral cerebellar volume decrease was associated with reduced cerebral white matter volume, and with reduced executive, visuo-spatial and language function. Vermis volume was less strongly related to cognitive function. Volume decrement of the lateral lobes, rather than the vermis, is associated with neuropsychological dysfunction in very preterm individuals.

CREB phosphorylation following hypoxia and ischemia in striatum of newborn piglets: Possible role of dopamine

The goal of the present study was to determine the effects of hypoxia and ischemia and the role of dopamine on phosphorylation of cAMP response element binding protein (CREB) in striatum of newborn piglets. Piglets, with and without prior injection of alpha-methyl-p-tyrosine (AMT), an inhibitor of dopamine (DA) synthesis, were subjected to 1 h of hypoxia (decreased inspired oxygen pressure, FiO2, from 21 to 6%) or 1 h of ischemia (ligation of both carotid arteries and hemorrhage to reduce the systemic arterial pressure to about 40 mmHg), followed by 2 h recovery. Microvascular oxygen pressure in the cortex (pCO2) was measured by quenching of phosphorescence. Extracellular DA was determined by in vivo microdialysis. Striatal levels of phosphorylated CREB (pCREB) and total CREB were determined by Western blots. In sham-operated animals, pCO2 was 49.7 +/- 8.2 mmHg. During hypoxia and ischemia, pCO2 decreased to 6.3 +/- 1.8 mmHg and 10.2 +/- 2.7 mmHg, respectively. There was statistical difference in the level of extracellular DA during hypoxia versus ischemia. At the end of ischemia and hypoxia, the levels of DA were 96 x 10(3) +/- 24 x 10(3)% and 26 x 10(3) +/- 12 x 10(3)% of control, respectively. The pCREB measured after 2 h recovery was not changed after hypoxia but was decreased to 47.8 +/- 24% of control after ischemia. Depletion of endogenous DA abolished the ischemia-induced decrease in pCREB level. Total CREB did not change after either condition. It can be concluded that observed decreases of CREB phosphorylation following ischemia can be at least partially due to the high extracellular DA level.

Late gestation cerebellar growth is rapid and impeded by premature birth

OBJECTIVE

Cognitive impairments and academic failure are commonly reported in survivors of preterm birth. Recent studies suggest an important role for the cerebellum in the development of cognitive and social functions. The objective of this study was to examine the impact of prematurity itself, as well as prematurity-related brain injuries, on early postnatal cerebellar growth with quantitative MRI.

METHODS

Advanced 3-dimensional volumetric MRI was performed and cerebellar volumes were obtained by manual outlining in preterm (<37 weeks) and healthy term-born infants. Intracranial and total brain volumes were also calculated.

RESULTS

A total of 169 preterm and 20 healthy full-term infants were studied; 145 had preterm MRI (pMRI), 75 had term MRI (tMRI), and 51 underwent both pMRI and tMRI. From 28 weeks' postconceptional age to term, mean cerebellar volume (177%) in preterm infants increased at a much faster rate than did mean intracranial (110%) or mean brain (107%) volumes. Smaller cerebellar volume was significantly related to lower gestational age at birth and to intracranial and total brain volumes. Mean cerebellar volume of preterm infants at tMRI was significantly smaller than the volumes of term-born infants. Cerebellar growth impairment was correlated strongly with associated brain injuries, even in the absence of direct cerebellar injury.

CONCLUSIONS

Our data suggest that the growth of the immature cerebellum is particularly rapid during late gestation. However, this accelerated growth seems to be impeded by premature birth and associated brain injury. The long-term neurodevelopmental disabilities seen in survivors of premature birth may be attributable in part to impaired cerebellar development.

Differential vulnerability of immature murine neurons to oxygen-glucose deprivation

In vivo studies support selective neuronal vulnerability to hypoxia-ischemia (HI) in the developing brain. Since differences in intrinsic properties of neurons might be responsible, pure cultures containing immature neurons (6-8 days in vitro) isolated from mouse cortex and hippocampus, regions chosen for their marked vulnerability to oxidative stress, were studied under in vitro ischemic conditions-oxygen-glucose deprivation (OGD). Twenty-four hours of reoxygenation after 2.5 h of OGD induced significantly greater cell death in hippocampal than in cortical neurons (67.8% vs. 33.4%, P = 0.0068). The expression of neuronal nitric oxide synthase (nNOS) protein, production of nitric oxide (NO), and reactive oxygen species (ROS), as well as glutathione peroxidase (GPx) activity and intracellular levels of reduced glutathione (GSH), were measured as indicators of oxidative stress. Hippocampal neurons had markedly higher nNOS expression than cortical neurons by 24 h of reoxygenation, which coincided with an increase in NO production, and significantly greater ROS accumulation. GPx activity declined significantly in hippocampal but not in cortical neurons at 4 and 24 h after OGD. The decrease in GSH level in hippocampal neurons correlated with the decline of GPx activity. Our data suggest that developing hippocampal neurons are more sensitive to OGD than cortical neurons. This finding supports our in vivo studies showing that mouse hippocampus is more vulnerable than cortex after neonatal HI. An imbalance between excess prooxidant production (increased nNOS expression, and NO and ROS production) and insufficient antioxidant defenses created by reduced GPx activity and GSH levels may, in part, explain the higher susceptibility to OGD of immature hippocampal neurons.

Neuroimaging in cerebral palsy

Parents and clinicians concerned about high-risk infants and children with motor delay or cerebral palsy seek information on cause, treatment, prognosis, and recurrence risk. Used in combination with history and examination, neuroimaging studies can improve diagnosis and management. In premature infants, cranial ultrasound is a reliable, noninvasive diagnostic modality. Nuclear magnetic resonance techniques including magnetic resonance imaging and diffusion weighted imaging can be used effectively in neonatal encephalopathies. In children with motor delay and cerebral palsy syndromes including spastic diplegia, quadriplegia, hemiplegia, and extrapyramidal movement disorders, conventional magnetic resonance imaging has become an important determinant of diagnosis and management. The aim of this article is to help clinicians select and interpret imaging studies of benefit in clinical care.

Patterns of cerebral injury in a series of infants with congenital diaphragmatic hernia utilizing magnetic resonance imaging

BACKGROUND

Congenital diaphragmatic hernia (CDH) is a condition with significant mortality and respiratory morbidity. Long-term neurodevelopmental outcome is not yet well documented.

METHODS

The authors examined all cases of CDH at their institution over a 12-month period and performed magnetic resonance imaging (MRI) of the brain postoperatively.

RESULTS

Eight of 10 patients survived to have an MR brain scan. All 8 patients had cerebral injury detected on MRI, with a predominance of white matter and deep nuclear gray matter injury.

CONCLUSIONS

Cerebral injury detected with MRI is common in infants with congenital diaphragmatic hernia. The long-term significance of these MRI abnormalities is unknown, although the need for good long-term neurodevelopmental follow-up of infants with CDH is highlighted.

Development of a postnatal 3-day-old rat model of mild hypoxic-ischemic brain injury

Improvements in both obstetric and paediatric care have been responsible for a continuing reduction in mortality in extremely premature infants. However, higher survival rates have been at the expense of more long-term neurological damage. Various animal models have been developed to study the effect of hypoxic-ischemic insults on the brain. However, established models like the postnatal day 7 rat model represent damage found in term infants rather than in preterm infants of 24-28 weeks' gestation, and produce a severe form of injury resulting in high mortality rates. In this study we developed a reliable model of minor hypoxic-ischemic brain injury in postnatal day 3 rats. At this maturity, the pattern of damage represents that expected in a preterm infant suffering a non-lethal perinatal insult. We found that minor changes in duration of insult and both temperature and humidity produced wide fluctuations in the degree of injury observed. By maintaining strict control over experimental conditions including duration of insult, temperature and humidity, we produced a reliable model of minor injury primarily affecting all five areas of the cerebral cortex, and also the thalamus (area 7) and basal ganglia (area 8). Differences were significant compared to normal controls and sham-operated animals (p<0.05). These areas represent the primary motor, insular, visual and temporal cortices. The overall mortality rate in this study was 12.3%.

MRI measurements of the pons and cerebellum in children born preterm; associations with the severity of periventricular leukomalacia and perinatal risk factors

Our purpose was to measure the size of the pons and cerebellum in preterm babies with periventricular leukomalacia (PVL), and to study their relationship with the severity of PVL and with perinatal risk factors. We examined 33 premature children, mean gestational age 31 weeks, range 26-36 weeks with PVL on MRI, and 27 full-term controls. On MRI at 0.4-5.5 years (mean 1.4 years) we measured the area of the corpus callosum and vermis, the anteroposterior diameter of the pons and the volume of the cerebellum. The area of the corpus callosum was used as a marker of white matter loss and PVL severity. All regional brain measurements except that of the vermis were significantly lower in patients than controls: corpus callosum (mm(2)): 239.6+/-92.5 vs 434.8+/-126.8, P <0.01; pons (mm): 14.8+/-3.0 vs 17.9+/-1.4, P <0.01]; cerebellum (cm(3)): 68.2+/-31.6 vs 100.6+/-28.3, P <0.01; vermis (mm(2)): 808.1+/-292.2 vs 942.2+/-246.2, NS. Significant reduction in the area of the vermis: 411.3+/-203.3 vs 935+/-252.6 mm(2); cerebellar volume: 16.3+/-12.5 vs 96.6+/-20.2 mm(3); and the diameter of the pons: 10.1+/-2.2 vs 17.5+/-1.3 mm ( P<0.01) were observed in seven children with gestational age < or =28 weeks, severe hypotension and large patent ductus arteriosus (PDA). There was a significant correlation between the duration of mechanical ventilation and the size of the vermis, pons and cerebellum (R=-0.65, -0.57 and -0.73, respectively, P <0.01).

The effect on motor cortical neuronal development of focal lesions to the sub-cortical white matter in the neonatal rat: a model for periventricular leukomalacia

Periventricular leukomalacia (PVL) is either a diffuse or cystic lesion of the periventricular white matter that leaves the overlying cortical grey matter largely intact. It is believed to result from hypoxia occurring pre- or perinatally and is a major cause of cerebral palsy. We have modelled PVL in rats comparing the effects of discrete injections of 3-nitropropionic acid (3-NP), a mitochondrial toxin, ibotenic acid (IBA), a glutamate analogue, or saline into the sub-cortical white matter on postnatal day 7 (P7). Following recovery times ranging from 3 days to 4 weeks, forebrain sections were Nissl stained or immunostained for Bax, cJun, calbindin (CB), parvalbumin (PV) or non-phosphorylated neurofilaments (NPNF). Compared to saline injections, ibotenic acid caused large lesions of both grey and white matter not characteristic of periventricular leukomalacia. 3-Nitropropionic acid injections caused small focal lesions restricted to the sub-cortical white matter. 3-Nitropropionic acid treatment initially increased expression of the apoptosis promoting proteins Bax and cJun, as well as non-phosphorylated neurofilaments in cortical layer V overlying the injection site. Non-phosphorylated neurofilament expression distal to the lesion was decreased representing a loss of cortical axons, but persisted and even increased with time within the cortex, demonstrating persistence of the parent cell bodies and local sprouting of neurites. There were significantly fewer calbindin and parvalbumin positive neurones in the motor cortex (MC) side ipsilateral to the 3-nitropropionic acid injection compared to the contralateral side. These persistent differences in expression of activity sensitive calcium binding proteins suggest alterations in local cortical circuitry without substantial loss of grey matter as is characteristic of periventricular leukomalacia. Changes in expression of Bax, cJun and non-phosphorylated neurofilaments during normal development are also described.

Selective vulnerability of subplate neurons after early neonatal hypoxia-ischemia

Neonatal hypoxia-ischemia in the preterm human leads to selective injury to the subcortical developing white matter, which results in periventricular leukomalacia (PVL), a condition associated with abnormal neurodevelopment. Maturation-dependent vulnerability of late oligodendrocyte progenitors is thought to account for the cellular basis of this condition. A high frequency of cognitive and sensory deficits with decreasing gestational age suggests pervasive abnormalities of cortical development. In a neonatal rat model of hypoxic-ischemic injury that produces the characteristic pattern of subcortical injury associated with human PVL, selective subplate neuron death is seen. The premature subplate neuron death occurs after thalamic axons have reached their targets in cortex. Thus, as expected, thalamocortical connections form normally, including patterned connections to somatosensory cortex. However, deficits in motor function still occur, as in babies with PVL. Subplate neuron cell death in PVL provides another mechanism for abnormal neurodevelopment after neonatal hypoxia-ischemia.

Altered expression and phosphorylation of N-methyl-D-aspartate receptors in piglet striatum after hypoxia-ischemia

The mechanisms for the profound degeneration of striatal neurons after hypoxia-ischemia in newborns are not understood. We hypothesized that this striatal neurodegeneration is related to N-methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity. Using a 1-week-old piglet model of hypoxia-ischemia, we evaluated whether the expression and phosphorylation of NMDA receptor subunits in striatum are modified with severity of evolving neuronal injury after hypoxia-ischemia. Protein levels of NR1, phosphorylated NR1 897serine, NR2A and NR2B in striatum were measured by immunoblotting after piglets underwent hypoxic-asphyxic cardiac arrest, cardiopulmonary resuscitation, and recovery for 3, 6, 12 or 24 h. In membrane fractions isolated from total striatum, mean NR1 and NR2A levels did not change significantly with time after hypoxia-ischemia compared to control; however, the levels of both NR1 and phosphorylated NR1 897serine correlated with neuronal injury in putamen, with higher levels associated with greater neuronal injury in individual animals. NR2B levels were increased at 24 h after hypoxia-ischemia. Astrocyte expression of NR2B was prominent after hypoxia-ischemia. We conclude that NMDA receptors are changed in striatum after neonatal hypoxia-ischemia and that abnormal NMDA receptor potentiation through increased NR1 phosphorylation may participate in the mechanisms of striatal neuron degeneration after hypoxia-ischemia.

Mechanisms of hypoxic neurodegeneration in the developing brain

Asphyxia and other insults to the developing brain are responsible for several human neurodevelopmental disorders. The pattern of neonatal brain injury differs from that seen in the adult nervous system, and there are wide differences in regional vulnerability. Recent evidence suggests that two events that contribute to this pattern of selective vulnerability are developmental changes in excitatory glutamate-containing neurotransmitter circuits and the propensity for immature neurons to die by apoptosis rather than necrosis. Developmental up-regulation of NMDA receptors with enhanced function and increased expression of caspase-3 at critical periods in development are linked to these mechanisms. Although these molecular changes enhance the developing brain's capacity for plasticity by helping to prune redundant synapses and neurons, they can become "Achilles heels" in the face of a brain energy crisis.

Perinatal expression of heat shock proteins HSC 70 and HSP 70 in neural and non neural tissues of the piglet

Stress of different kinds during early perinatal life can result in severe consequences for further development. To determine possible involvement of heat shock proteins in brain development, the expression of HSC 70 and HSP 70 was determined in brain regions (cerebellum, cortex, hippocampus, hypothalamus and striatum) and non neural tissues (liver, lungs and kidneys) at birth and during early development of the piglet. In brain regions, HSC 70 expression was decreased during the few hours following birth. With the exception of cortex, hippocampus and kidney where a decrease of expression was observed, HSP 70 did not show significant changes during early development. These results are discussed in terms of using the piglet model of development to study the effect of different kinds of stress like hypoxia or temperature changes on brain development.

Neurobiology of hypoxic-ischemic injury in the developing brain

Hypoxic ischemia is a common cause of damage to the fetal and neonatal brain. Although systemic and cerebrovascular physiologic factors play an important role in the initial phases of hypoxic-ischemic injuries, the intrinsic vulnerability of specific cell types and systems in the developing brain may be more important in determining the final pattern of damage and functional disability. Excitotoxicity, a term applied to the death of neurons and certain other cells caused by overstimulation of excitatory, mainly glutamate, neurotransmitter receptors, plays a critical role in these processes. Selected neuronal circuits as well as certain populations of glia such as immature periventricular oligodendroglia may die from excitotoxicity triggered by hypoxic ischemia. These patterns of neuropathologic vulnerability are associated with clinical syndromes of neurologic disability such as the extrapyramidal and spastic diplegia forms of cerebral palsy. The cascade of biochemical and histopathologic events triggered by hypoxic ischemia can extend for days to weeks after the insult is triggered, creating the potential for therapeutic interventions.

Cognitive and motor function and the size of the cerebellum in adolescents born very pre-term

Individuals born before 33 weeks' gestation are at risk of brain lesions, which have the potential to disrupt subsequent neurodevelopment. As a result they manifest an increased incidence of neuromotor signs and cognitive deficits, which can still be detected in adolescence. The cerebellum is known to be involved in both the co-ordination of movement and in cognitive processes. We therefore set out to establish whether cognitive and motor impairments in adolescents born very pre-term are associated with abnormalities of the cerebellum as revealed by volumetric analysis of brain MRI scans. The volume of the whole cerebellum was determined manually using a PC-based Cavalieri procedure in 67 adolescents born very pre-term and 50 age-matched, full-term born controls. Cognitive and neurological assessments were performed at 1, 4, 8 and 14-15 years of age as part of the long-term follow-up of the pre-term subjects. The pre-term-born subjects had significantly reduced cerebellar volume compared with term-born controls (P<0.001). This difference was still present after controlling for potential confounders. There was no association between cerebellar volume and motor neurological signs. However, there were significant associations between cerebellar volume and several cognitive test scores, in particular the Wechsler Intelligence Scale for Children-Revised, the Kaufman Assessment Battery for Children and the Schonnel reading age. This provides further evidence implicating the cerebellum in cognition and suggests that cerebellar abnormalities may underlie some of the cognitive deficits found in individuals born very pre-term.

Neuronal death in newborn striatum after hypoxia-ischemia is necrosis and evolves with oxidative stress

The mechanisms for neurodegeneration after hypoxia-ischemia (HI) in newborns are not understood. We tested the hypothesis that striatal neuron death is necrosis and evolves with oxidative stress and selective organelle damage. Piglets ( approximately 1 week old) were used in a model of hypoxia-asphyxia and survived for 3, 6, 12, or 24 h. Neuronal death was progressive over 3-24 h recovery, with approximately 80% of putaminal neurons dead at 24 h. Striatal DNA was digested randomly at 6-12 h. Ultrastructurally, dying neurons were necrotic. Damage to the Golgi apparatus and rough endoplasmic reticulum occurred at 3-12 h, while most mitochondria appeared intact until 12 h. Mitochondria showed early suppression of activity, then a transient burst of activity at 6 h, followed by mitochondrial failure (determined by cytochrome c oxidase assay). Cytochrome c was depleted at 6 h after HI and thereafter. Damage to lysosomes occurred within 3-6 h. By 3 h recovery, glutathione levels were reduced, and peroxynitrite-mediated oxidative damage to membrane proteins, determined by immunoblots for nitrotyrosine, occurred at 3-12 h. The Golgi apparatus and cytoskeleton were early targets for extensive tyrosine nitration. Striatal neurons also sustained hydroxyl radical damage to DNA and RNA within 6 h after HI. We conclude that early glutathione depletion and oxidative stress between 3 and 6 h reperfusion promote damage to membrane and cytoskeletal proteins, DNA and RNA, as well as damage to most organelles, thereby causing neuronal necrosis in the striatum of newborns after HI.

Periventricular leukomalacia: relationship between lateral ventricular volume on brain MR images and severity of cognitive and motor impairment

PURPOSE

To evaluate the utility of lateral ventricular volume measurements in predicting motor and cognitive impairment severity in children with periventricular leukomalacia (PVL), with or without seizures.

MATERIALS AND METHODS

The charts of children with spastic cerebral palsy and PVL documented on brain magnetic resonance (MR) images were reviewed. Affected children were grouped by motor and cognitive impairment severity and seizure disorder. An age-matched control group was established. Lateral ventricular volumes were measured on two-dimensional T2-weighted spin-echo MR images. Analysis of variance was used to identify significant differences in mean lateral ventricular volume between groups. Paired analyses of differences were performed with the Bonferroni t method.

RESULTS

Thirty-six children (24 boys, 12 girls) with spastic cerebral palsy and PVL and 21 age-matched control subjects (14 boys, seven girls) were identified. Mean lateral ventricular volumes of the moderate and marked motor deficit groups were significantly larger than those of the control and mild motor deficit groups (F = 29.24; alpha = .01). Mean lateral ventricular volumes of all cognitive impairment groups were significantly larger than those of the control and no-cognitive-impairment groups (F = 21.101 alpha = .01). There was no difference in mean lateral ventricular volume between children with PVL with or without seizures.

CONCLUSION

Lateral ventricular volume measurements can be used as quantitative markers of clinical impairment severity and as clinical outcome predictors before formal testing is possible.

Functional corticospinal projections are established prenatally in the human foetus permitting involvement in the development of spinal motor centres

From studies of subhuman primates it has been assumed that functional corticospinal innervation occurs post-natally in man. We report a post-mortem morphological study of human spinal cord, and neurophysiological and behavioural studies in preterm and term neonates and infants. From morphological studies it was demonstrated that corticospinal axons reach the lower cervical spinal cord by 24 weeks post-conceptional age (PCA) at the latest. Following a waiting period of up to a few weeks, it appears they progressively innervate the grey matter such that there is extensive innervation of spinal neurons, including motor neurons, prior to birth. Functional monosynaptic corticomotoneuronal projections were demonstrated neurophysiologically from term, but are also likely to be present from as early as 26 weeks PCA. At term, direct corticospinal projections to Group Ia inhibitory interneurons were also confirmed. Independent finger movements developed much later, between 6 and 12 months post-natally. These data do not support the proposal that in man, establishment of functional corticomotoneuronal projections occurs immediately prior to and provides the capacity for the expression of fine finger movement control. We propose instead that such early corticospinal innervation occurs to permit cortical involvement in activity dependent maturation of spinal motor centres during a critical period of perinatal development. Spastic cerebral palsy from perinatal damage to the corticospinal pathway secondarily involves disrupted development of spinal motor centres. Corticospinal axons retain a high degree of plasticity during axon growth and synaptic development. The possibility therefore exists to promote regeneration of disrupted corticospinal projections during the perinatal period with the double benefit of restoring corticospinal connectivity and normal development of spinal motor centres.

Measurement of the urinary lactate:creatinine ratio for the early identification of newborn infants at risk for hypoxic-ischemic encephalopathy

BACKGROUND

Newborn infants with perinatal asphyxia are prone to the development of hypoxic-ischemic encephalopathy. There are no reliable methods for identifying infants at risk for this disorder.

METHODS

We measured the ratio of lactate to creatinine in urine by proton nuclear magnetic resonance spectroscopy within 6 hours and again 48 to 72 hours after birth in 58 normal infants and 40 infants with asphyxia. The results were correlated with the subsequent presence or absence of hypoxic-ischemic encephalopathy.

RESULTS

Hypoxic-ischemic encephalopathy did not develop in any of the normal newborns but did develop in 16 of the 40 newborns with asphyxia. Within six hours after birth, the mean (+/-SD) ratio of urinary lactate to creatinine was 16.75+/-27.38 in the infants who subsequently had hypoxic-ischemic encephalopathy, as compared with 0.09+/-0.02 in the normal infants (P<0.001) and 0.19+/-0.12 in the infants with asphyxia in whom hypoxic-ischemic encephalopathy did not develop (P<0.001). A ratio of 0.64 or higher within six hours after birth had a sensitivity of 94 percent and a specificity of 100 percent for predicting the development of hypoxic-ischemic encephalopathy. The sensitivity and specificity of measurements obtained 48 to 72 hours after birth were much lower. The mean ratio of urinary lactate to creatinine was significantly higher in the infants who had adverse outcomes at one year (25.36+/-32.02) than in the infants with favorable outcomes (0.63+/-1.50) (P<0.001).

CONCLUSIONS

Measurement of the urinary lactate: creatinine ratio soon after birth may help identify infants at high risk for hypoxic-ischemic encephalopathy.