In vivo effect of chronic hypoxia on the neurochemical profile of the developing rat hippocampus

Preterm babies treated with lengthy continuous positive airway pressure are associated with moderate auditory abnormality

AIMS

Continuous positive airway pressure (CPAP) has been used for the prevention and treatment of neonatal respiratory distress for over four decades, but it remains very poorly understood whether there is any brainstem auditory abnormality in babies treated with CPAP. We aimed to detect brainstem auditory abnormality at 34-35 weeks of corrected age in preterm babies treated with CPAP and define any difference between different durations of CPAP treatment.

STUDY DESIGN

Preterm babies were recruited and dichotomized to those with CPAP treatment (CPAP group, n = 67) and those without CPAP treatment (n-CPAP group) (n = 49). Brainstem auditory evoked response (BAER) was studied at 34-35 weeks of corrected age.

RESULTS

Compared with the n-CPAP group, the CPAP group manifested moderately elevated BAER threshold and significantly prolonged latencies of BAER waves III and V and I-V interval. The prolongation was generally more significant in the babies with longer duration of CPAP treatment than those with shorter duration. The I-V interval in the babies with CPAP treatment for >30 days were significantly longer than those with fewer days of CPAP treatment.

CONCLUSION

At 34-35 weeks of corrected age, preterm babies treated with CPAP are associated with moderate auditory abnormality. Further study is warranted to explore more detail of the auditory abnormality in babies treated with CPAP.

Neonatal hyperbilirubinemia differentially alters the neurochemical profiles of the developing cerebellum and hippocampus in a preterm Gunn rat model

Neonatal hyperbilirubinemia (NHB) can lead to brain injury in newborn infants by affecting specific regions including the cerebellum and hippocampus. Extremely preterm infants are more vulnerable to bilirubin neurotoxicity, but the mechanism and extent of injury is not well understood. A preterm version of the Gunn rat model was utilized to investigate severe preterm NHB. Homozygous/jaundiced Gunn rat pups were injected (i.p.) on postnatal day (P) 5 with sulfadimethoxine, which increases serum free bilirubin capable of crossing the blood-brain barrier and causing brain injury. The neurochemical profiles of the cerebellum and hippocampus were determined using in vivo ¹ H MRS at 9.4 T on P30 and compared with those of heterozygous/non-jaundiced control rats. Transcript expression of related genes was determined by real-time quantitative PCR. MRI revealed significant morphological changes in the cerebellum of jaundiced rats. The concentrations of myo-inositol (+54%), glucose (+51%), N-acetylaspartylglutamate (+21%), and the sum of glycerophosphocholine and phosphocholine (+17%) were significantly higher in the cerebellum of the jaundiced group compared with the control group. Despite the lack of morphologic changes in the hippocampus, the concentration of myo-inositol (+9%) was higher and the concentrations of creatine (-8%) and of total creatine (-3%) were lower in the jaundiced group. In the hippocampus, expression of calcium/calmodulin dependent protein kinase II alpha (Camk2a), glucose transporter 1 (Glut1), and Glut3 transcripts were downregulated in the jaundiced group. In the cerebellum, glial fibrillary acidic protein (Gfap), myelin basic protein (Mbp), and Glut1 transcript expression was upregulated in the jaundiced group. These results indicate osmotic imbalance, gliosis, and changes in energy utilization and myelination, and demonstrate that preterm NHB critically affects brain development in a region-specific manner, with the cerebellum more severely impacted than the hippocampus.

Female and male C57BL/6J offspring exposed to maternal obesogenic diet develop altered hypothalamic energy metabolism in adulthood

Maternal obesity is exceedingly common and strongly linked to offspring obesity and metabolic disease. Hypothalamic function is critical to obesity development. Hypothalamic mechanisms causing obesity following exposure to maternal obesity have not been elucidated. Therefore, we studied a cohort of C57BL/6J dams, treated with a control or high-fat-high-sugar diet, and their adult offspring to explore potential hypothalamic mechanisms to explain the link between maternal and offspring obesity. Dams treated with obesogenic diet were heavier with mild insulin resistance, which is reflective of the most common metabolic disease in pregnancy. Adult offspring exposed to maternal obesogenic diet had no change in body weight but significant increase in fat mass, decreased glucose tolerance, decreased insulin sensitivity, elevated plasma leptin, and elevated plasma thyroid-stimulating hormone. In addition, offspring exposed to maternal obesity had decreased energy intake and activity without change in basal metabolic rate. Hypothalamic neurochemical profile and transcriptome demonstrated decreased neuronal activity and inhibition of oxidative phosphorylation. Collectively, these results indicate that maternal obesity without diabetes is associated with adiposity and decreased hypothalamic energy production in offspring. We hypothesize that altered hypothalamic function significantly contributes to obesity development. Future studies focused on neuroprotective strategies aimed to improve hypothalamic function may decrease obesity development.NEW & NOTEWORTHY Offspring exposed to maternal diet-induced obesity demonstrate a phenotype consistent with energy excess. Contrary to previous studies, the observed energy phenotype was not associated with hyperphagia or decreased basal metabolic rate but rather decreased hypothalamic neuronal activity and energy production. This was supported by neurochemical changes in the hypothalamus as well as inhibition of hypothalamic oxidative phosphorylation pathway. These results highlight the potential for neuroprotective interventions in the prevention of obesity with fetal origins.

The interplay of hypoxic and mental stress: Implications for anxiety and depressive disorders

Adequate oxygen supply is essential for the human brain to meet its high energy demands. Therefore, elaborate molecular and systemic mechanism are in place to enable adaptation to low oxygen availability. Anxiety and depressive disorders are characterized by alterations in brain oxygen metabolism and of its components, such as mitochondria or hypoxia inducible factor (HIF)-pathways. Conversely, sensitivity and tolerance to hypoxia may depend on parameters of mental stress and the severity of anxiety and depressive disorders. Here we discuss relevant mechanisms of adaptations to hypoxia, as well as their involvement in mental stress and the etiopathogenesis of anxiety and depressive disorders. We suggest that mechanisms of adaptations to hypoxia (including metabolic responses, inflammation, and the activation of chemosensitive brain regions) modulate and are modulated by stress-related pathways and associated psychiatric diseases. While severe chronic hypoxia or dysfunctional hypoxia adaptations can contribute to the pathogenesis of anxiety and depressive disorders, harnessing controlled responses to hypoxia to increase cellular and psychological resilience emerges as a novel treatment strategy for these diseases.

Anorexia disrupts glutamate-glutamine homeostasis associated with astroglia in the prefrontal cortex of young female rats

Anorexia nervosa (AN) is an eating disorder characterized by self-starvation and excessive weight loss with a notorious prevalence in young women. The neurobiology of AN is unknown but murine models, like dehydration induced anorexia (DIA), reproduce weight loss and avoidance of food despite its availability. Astrocytes are known to provide homeostatic support to neurons, but it is little explored if anorexia affects this function. In this study, we tested if DIA disrupts glutamate-glutamine homeostasis associated with astrocytes in the prefrontal cortex (PFC) of young female rats. Our results showed that anorexia reduced the redox state, as well as endogenous glutamate and glutamine. These effects correlated with a reduced expression of the glutamate transporters (GLT-1 and GLAST) and glutamine synthetase, all of them are preferentially expressed by astrocytes. Accordingly, the expression of GFAP was reduced. Anorexia reduced the astrocyte density, promoted a de-ramified morphology, and augmented the de-ramified/ramified astrocyte ratio in the medial prefrontal cortex (mPFC) and orbitofrontal cortex (OFC), but not in the motor cortex (M2). The increase of a de-ramified phenotype correlated with increased expression of vimentin and nestin. Based on these results, we conclude that anorexia disrupts glutamate-glutamine homeostasis and the redox state associated with astrocyte dysfunction.

GABA and glutamate in the preterm neonatal brain: In-vivo measurement by magnetic resonance spectroscopy

Cognitive and behavioral disabilities in preterm infants, even without obvious brain injury on conventional neuroimaging, underscores a critical need to identify the subtle underlying microstructural and biochemical derangements. The gamma-aminobutyric acid (GABA) and glutamatergic neurotransmitter systems undergo rapid maturation during the crucial late gestation and early postnatal life, and are at-risk of disruption after preterm birth. Animal and human autopsy studies provide the bulk of current understanding since non-invasive specialized proton magnetic resonance spectroscopy (¹H-MRS) to measure GABA and glutamate are not routinely available for this vulnerable population due to logistical and technical challenges. We review the specialized ¹H-MRS techniques including MEscher-GArwood Point Resolved Spectroscopy (MEGA-PRESS), special challenges and considerations needed for interpretation of acquired data from the developing brain of preterm infants. We summarize the limited in-vivo preterm data, highlight the gaps in knowledge, and discuss future directions for optimal integration of available in-vivo approaches to understand the influence of GABA and glutamate on neurodevelopmental outcomes after preterm birth.

The Effects of Early-Life Iron Deficiency on Brain Energy Metabolism

Iron deficiency (ID) is one of the most prevalent nutritional deficiencies in the world. Iron deficiency in the late fetal and newborn period causes abnormal cognitive performance and emotional regulation, which can persist into adulthood despite iron repletion. Potential mechanisms contributing to these impairments include deficits in brain energy metabolism, neurotransmission, and myelination. Here, we comprehensively review the existing data that demonstrate diminished brain energetic capacity as a mechanistic driver of impaired neurobehavioral development due to early-life (fetal-neonatal) ID. We further discuss a novel hypothesis that permanent metabolic reprogramming, which occurs during the period of ID, leads to chronically impaired neuronal energetics and mitochondrial capacity in adulthood, thus limiting adult neuroplasticity and neurobehavioral function. We conclude that early-life ID impairs energy metabolism in a brain region- and age-dependent manner, with particularly strong evidence for hippocampal neurons. Additional studies, focusing on other brain regions and cell types, are needed.

Impact of perinatal hypoxia on the developing brain

Perinatal hypoxia is still one of the greatest threats to the newborn child, even in developed countries. However, there is a lack of works which summarize up-to-date information about that huge topic. Our review covers a broader spectrum of recent results from studies on mechanisms leading to hypoxia-induced injury. It also resumes possible primary causes and observed behavioral outcomes of perinatal hypoxia. In this review, we recognize two types of hypoxia, according to the localization of its primary cause: environmental and placental. Later we analyze possible pathways of prenatal hypoxia-induced injury including gene expression changes, glutaminergic excitatory damage (and a role of NMDA receptors in it), oxidative stress with ROS and RNS production, inflammation and apoptosis. Moreover, we focus on the impact of these pathophysiological changes on the structure and development of the brain, especially on its regions: corpus striatum and hippocampus. These brain changes of the offspring lead to impairments in their postnatal growth and sensorimotor development, and in their motor functions, activity, emotionality and learning ability in adulthood. Later we compare various animal models used to investigate the impact of prenatal and postnatal injury (hypoxic, ischemic or combinatory) on living organisms, and show their advantages and limitations.

PRESS timings for resolving 13 C4 -glutamate 1 H signal at 9.4 T: Demonstration in rat with uniformly labelled 13 C-glucose

MRS of ¹³ C₄ -labelled glutamate (¹³ C₄ -Glu) during an infusion of a carbon-13 (¹³ C)-labelled substrate, such as uniformly labelled glucose ([U-¹³ C₆ ]-Glc), provides a measure of Glc metabolism. The presented work provides a single-shot indirect ¹³ C detection technique to quantify the approximately 2.51 ppm ¹³ C₄ -Glu satellite proton (¹ H) peak at 9.4 T. The methodology is an optimized point-resolved spectroscopy (PRESS) sequence that minimizes signal contamination from the strongly coupled protons of N-acetylaspartate (NAA), which resonate at approximately 2.49 ppm. J-coupling evolution of protons was characterized numerically and verified experimentally. A (TE₁ , TE₂ ) combination of (20 ms, 106 ms) was found to be suitable for minimizing NAA signal in the 2.51 ppm ¹ H ¹³ C₄ -Glu spectral region, while retaining the ¹³ C₄ -Glu ¹ H satellite peak. The efficacy of the technique was verified on phantom solutions and on two rat brains in vivo during an infusion of [U-¹³ C₆ ]-Glc. LCModel was employed for analysis of the in vivo spectra to quantify the 2.51 ppm ¹ H ¹³ C₄ -Glu signal to obtain Glu C4 fractional enrichment time courses during the infusions. Cramér-Rao lower bounds of about 8% were obtained for the 2.51 ppm ¹³ C₄ -Glu ¹ H satellite peak with the optimal TE combination.

Assessing therapeutic response non-invasively in a neonatal rat model of acute inflammatory white matter injury using high-field MRI

Perinatal infection and inflammatory episodes in preterm infants are associated with diffuse white matter injury (WMI) and adverse neurological outcomes. Inflammation-induced WMI was previously shown to be linked with later hippocampal atrophy as well as learning and memory impairments in preterm infants. Early evaluation of injury load and therapeutic response with non-invasive tools such as multimodal magnetic resonance imaging (MRI) would greatly improve the search of new therapeutic approaches in preterm infants. Our aim was to evaluate the potential of multimodal MRI to detect the response of interleukin-1 receptor antagonist (IL-1Ra) treatment, known for its neuroprotective properties, during the acute phase of injury on a model of neonatal WMI. Rat pups at postnatal day 3 (P3) received intracerebral injection of lipopolysaccharide with systemic IL-1Ra therapy. 24 h later (P4), rats were imaged with multimodal MRI to assess microstructure by diffusion tensor imaging (DTI) and neurochemical profile of the hippocampus with ¹H-magnetic resonance spectroscopy. Astrocyte and microglial activation, apoptosis and the mRNA expression of pro-inflammatory and necroptotic markers were assessed. During the acute phase of injury, neonatal LPS exposure altered the concentration of hippocampus metabolites related to neuronal integrity, neurotransmission and membrane integrity and induced diffusivity restriction. Just 24 h after initiation of therapy, early indication of IL-1Ra neuroprotective effect could be detected in vivo by non-invasive spectroscopy and DTI, and confirmed with immunohistochemical evaluation and mRNA expression of inflammatory markers and cell death. In conclusion, multimodal MRI, particularly DTI, can detect not only injury but also the acute therapeutic effect of IL-1Ra suggesting that MRI could be a useful non-invasive tool to follow, at early time points, the therapeutic response in preterm infants.

Early-Life Iron Deficiency Alters Glucose Transporter-1 Expression in the Adult Rodent Hippocampus

BACKGROUND

Early-life iron deficiency (ID) impairs hippocampal energy production. Whether there are changes in glucose transporter (GLUT) expression is not known.

OBJECTIVE

The aim of this study was to investigate whether early-life ID and the treatment iron dose alter brain regional GLUT expression in adult rats and mice.

METHODS

In Study 1, ID was induced in male and female Sprague Dawley rat pups by feeding dams a 3-mg/kg iron diet during gestation and the first postnatal week, followed by treatment using low-iron [3-10 mg/kg; formerly iron-deficient (FID)-10 group], standard-iron (40-mg/kg; FID-40 group), or high-iron (400-mg/kg; FID-400 group) diets until weaning. The control group received the 40 mg/kg iron diet. GLUT1, GLUT3, hypoxia-inducible factor (HIF)-1α, and prolyl-hydroxylase-2 (PHD2) mRNA and protein expression in the cerebral cortex, hippocampus, striatum, cerebellum, and hypothalamus were determined at adulthood. In Study 2, the role of hippocampal ID in GLUT expression was examined by comparing the Glut1, Glut3, Hif1α, and Phd2 mRNA expression in adult male and female wild-type (WT) and nonanemic hippocampal iron-deficient and iron-replete dominant negative transferrin receptor 1 (DNTfR1-/-) transgenic mice.

RESULTS

In Study 1, Glut1, Glut3, and Hif1α mRNA, and GLUT1 55-kDa protein expression was upregulated 20-33% in the hippocampus of the FID-10 group but not the FID-40 group, relative to the control group. Hippocampal Glut1 mRNA (-39%) and GLUT1 protein (-30%) expression was suppressed in the FID-400 group, relative to the control group. Glut1 and Glut3 mRNA expression was not altered in the other brain regions in the 3 FID groups. In Study 2, hippocampal Glut1 (+14%) and Hif1α (+147%) expression was upregulated in the iron-deficient DNTfR1-/- mice, but not in the iron-replete DNTfR1-/- mice, relative to the WT mice (P < 0.05, all).

CONCLUSIONS

Early-life ID is associated with altered hippocampal GLUT1 expression in adult rodents. The mouse study suggests that tissue ID is potentially responsible.

Living High and Feeling Low: Altitude, Suicide, and Depression

After participating in this activity, learners should be better able to:• Assess epidemiologic evidence that increased altitude of residence is linked to increased risk of depression and suicide• Evaluate strategies to address hypoxia-related depression and suicidal ideation ABSTRACT: Suicide and major depressive disorder (MDD) are complex conditions that almost certainly arise from the influences of many interrelated factors. There are significant regional variations in the rates of MDD and suicide in the United States, suggesting that sociodemographic and environmental conditions contribute. Here, we review epidemiological evidence that increases in the altitude of residence are linked to the increased risk of depression and suicide. We consider the possibility that chronic hypobaric hypoxia (low blood oxygen related to low atmospheric pressure) contributes to suicide and depression, which is suggested by animal models, short-term studies in humans, and the effects of hypoxic medical conditions on suicide and depression. We argue that hypobaric hypoxia could promote suicide and depression by altering serotonin metabolism and brain bioenergetics; both of these pathways are implicated in depression, and both are affected by hypoxia. Finally, we briefly examine treatment strategies to address hypoxia-related depression and suicidal ideation that are suggested by these findings, including creatine monohydrate and the serotonin precursors tryptophan and 5-hydroxytryptophan.

Altitude and risk of depression and anxiety: findings from the intern health study

Multiple studies suggest that the risks of depression and suicide increase with increasing altitude of residence, but no studies have assessed whether changing altitude changes these risks. To address this gap, this study used data from the Intern Health Study, which follows students from the end of medical school through the first year of residency, recording depression via the 9-item Patient Health Questionnaire (PHQ-9), anxiety via the 7-item Generalized Anxiety Disorder Questionnaire (GAD-7), and multiple risk factors for these symptoms. Data from 3764 medical students representing 46 schools and 282 residencies were available. Odds ratios (OR) representing the effects of altitude on psychiatric symptoms were estimated using generalized linear models. After excluding participants with missing altitude data, 3731 medical students were analyzed. High altitude residence (> 900 m) was significantly associated with PHQ-9 total score (OR = 1.32, 95% CI = 1.001-1.75, p < 0.05), and PHQ-9 suicidal ideation (OR = 1.79, 95% CI = 1.08-0.02, p = 0.02). Moving from low to high altitude was significantly associated with PHQ-9 total score (OR = 1.47, 95% CI = 1.087-1.98, p = 0.01), GAD-7 total score (OR = 1.40, 95% CI = 1.0040-1.95, p < 0.05), and PHQ-9 suicidal ideation (OR = 1.10, 95% CI = 1.01-1.19, p = 0.02). The data suggest that moving from low to high altitude is associated with increasing symptoms of depression, anxiety, and suicidal ideation.

Anemia of prematurity and cerebral near-infrared spectroscopy: should transfusion thresholds in preterm infants be revised?

OBJECTIVE

To determine the impact of progressive anemia of prematurity on cerebral regional saturation (C-rSO₂) in preterm infants and identify the hemoglobin threshold below which a critical decrease (>2SD below the mean) in C-rSO₂ occurs.

STUDY DESIGN

In a cohort of infants born ≤30 weeks EGA, weekly C-rSO₂ data were prospectively collected from the second week of life through 36 weeks post-menstrual age (PMA). Clinically obtained hemoglobin values were noted at the time of recording. Recordings were excluded if they were of insufficient duration (<1 h) or if the hemoglobin was not measured within 7 days. Statistical analysis was performed using a linear mixed effects-model and ROC analysis. ROC analysis was used to determine the threshold of anemia, where C-rSO₂ critically decreased >2SD below the mean normative value (<55%) in preterm infants.

RESULTS

In total 253 recordings from 68 infants (mean EGA 26.9 ± 2.1 weeks, BW 1025 ± 287 g, 49% male) were included. Approximately 29 out of 68 infants (43%) were transfused during hospitalization. Mixed-model statistical analysis adjusting for EGA, BW, and PMA revealed a significant association between decreasing hemoglobin and C-rSO₂ (p < 0.01) in transfusion-naive infants but not in transfused infants. In the transfusion naive group, using ROC analysis demonstrated a threshold hemoglobin of 9.5 g/dL (AUC 0.81, p < 0.01) for critical cerebral desaturation in preterm infants.

CONCLUSIONS

In transfusion-naive preterm infants, worsening anemia was associated with a progressive decrease in cerebral saturations. Analysis identified a threshold hemoglobin of 9.5 g/dL below which C-rSO₂ dropped >2SD below the mean.

Improved resolution of glutamate, glutamine and γ-aminobutyric acid with optimized point-resolved spectroscopy sequence timings for their simultaneous quantification at 9.4 T

Glutamine (Gln), glutamate (Glu) and γ-aminobutyric acid (GABA) are relevant brain metabolites that can be measured with magnetic resonance spectroscopy (MRS). This work optimizes the point-resolved spectroscopy (PRESS) sequence echo times, TE₁ and TE₂ , for improved simultaneous quantification of the three metabolites at 9.4 T. Quantification was based on the proton resonances of Gln, Glu and GABA at ≈2.45, ≈2.35 and ≈2.28 ppm, respectively. Glu exhibits overlap with both Gln and GABA; in addition, the Gln peak is contaminated by signal from the strongly coupled protons of N-acetylaspartate (NAA), which resonate at about 2.49 ppm. J-coupling evolution of the protons was characterized numerically and verified experimentally. A {TE₁ , TE₂ } combination of {106 ms, 16 ms} minimized the NAA signal in the Gln spectral region, whilst retaining Gln, Glu and GABA peaks. The efficacy of the technique was verified on phantom solutions and on rat brain in vivo. LCModel was employed to analyze the in vivo spectra. The average T₂ -corrected Gln, Glu and GABA concentrations were found to be 3.39, 11.43 and 2.20 mM, respectively, assuming a total creatine concentration of 8.5 mM. LCModel Cramér-Rao lower bounds (CRLBs) for Gln, Glu and GABA were in the ranges 14-17%, 4-6% and 16-19%, respectively. The optimal TE resulted in concentrations for Gln and GABA that agreed more closely with literature concentrations compared with concentrations obtained from short-TE spectra acquired with a {TE₁ , TE₂ } combination of {12 ms, 9 ms}. LCModel estimations were also evaluated with short-TE PRESS and with the optimized long TE of {106 ms, 16 ms}, using phantom solutions of known metabolite concentrations. It was shown that concentrations estimated with LCModel can be inaccurate when combined with short-TE PRESS, where there is peak overlap, even when low (<20%) CRLBs are reported.

Myo-inositol Effects on the Developing Respiratory Neural Control System

Myo-inositol is a highly abundant stereoisomer of the inositol family of sugar alcohols and forms the structural basis for a variety of polyphosphate derivatives including second messengers and membrane phospholipids. These derivatives regulate numerous cell processes including gene transcription, membrane excitability, vesicular trafficking, intracellular calcium signaling, and neuronal growth and development. Myo-inositol can be formed endogenously from the breakdown of glucose, is found in a variety of foods including breastmilk and is commercially available as a nutritional supplement. Abnormal myo-inositol metabolism has been shown to underlie the pathophysiology of a variety of clinical conditions including Down Syndrome, traumatic brain injury, bronchopulmonary dysplasia (BPD), and respiratory distress syndrome (RDS). Several animal studies have shown that myo-inositol may play a critical role in development of both the central and peripheral respiratory neural control system; a notable example is the neonatal apnea and respiratory insufficiency that manifests in a mouse model of myo-inositol depletion, an effect that is also postnatally lethal. This review focuses on myo-inositol (and some of its derivatives) and how it may play a role in respiratory neural control; we also discuss clinical evidence demonstrating a link between serum myo-inositol levels and the incidence of intermittent hypoxemia (IH) events (a surrogate measure of apnea of prematurity (AOP)) in preterm infants. Further, there are both animal and human infant studies that have demonstrated respiratory benefits following supplementation with myo-inositol, which highlights the prospects that nutritional requirements are important for appropriate development and maturation of the respiratory system.

Early postnatal exposure to intermittent hypoxia in rodents is proinflammatory, impairs white matter integrity, and alters brain metabolism

BackgroundPreterm infants are frequently exposed to intermittent hypoxia (IH) associated with apnea and periodic breathing that may result in inflammation and brain injury that later manifests as cognitive and executive function deficits. We used a rodent model to determine whether early postnatal exposure to IH would result in inflammation and brain injury.MethodsRat pups were exposed to IH from P2 to P12. Control animals were exposed to room air. Cytokines were analyzed in plasma and brain tissue at P13 and P18. At P20-P22, diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS) were performed.ResultsPups exposed to IH had increased plasma Gro/CXCL1 and cerebellar IFN-γ and IL-1β at P13, and brainstem enolase at P18. DTI showed a decrease in FA and AD in the corpus callosum (CC) and cingulate gyrus, and an increase in RD in the CC. MRS revealed decreases in NAA/Cho, Cr, Tau/Cr, and Gly/Cr; increases in TCho and GPC in the brainstem; and decreases in NAA/Cho in the hippocampus.ConclusionsWe conclude that early postnatal exposure to IH, similar in magnitude to that experienced in human preterm infants, is associated with evidence for proinflammatory changes, decreases in white matter integrity, and metabolic changes consistent with hypoxia.

Abnormal findings in brainstem auditory evoked response at 36-37weeks of postconceptional age in babies with neonatal chronic lung disease

AIM

To examine brainstem auditory function at 36-37weeks of postconceptional age in preterm infants who are diagnosed to have neonatal chronic lung disease (CLD).

STUDY DESIGN

Preterm infants, born at 31 and less weeks of gestation, were studied at 36-37weeks of postconceptional age when they were diagnosed to have neonatal CLD. Brainstem auditory evoked response (BAER) was recorded and analyzed at different click rates.

RESULTS

Compared with healthy controls at the same postconceptional age, the CLD infants showed a slightly increase in BAER wave V latency. However, the I-V, and III-V interpeak intervals in the CLD infants were significantly increased. The III-V/I-III interval ratio was also significantly increased. The amplitudes of BAER waves III and V in the CLD infants tended to be reduced. These BAER findings were similar at all 21, 51 and 91/s clicks, although the abnormalities tended to be more significant at higher than at low click rates.

CONCLUSION

At 36-37weeks of postconceptional age, BAER was abnormal in preterm infants who were diagnosed to have neonatal CLD. This suggests that at time when the diagnosis of CLD is made there is functional impairment, reflecting poor myelination, in the brainstem auditory pathway in preterm infants with neonatal CLD.

In Vivo Neurochemical Characterization of Developing Guinea Pigs and the Effect of Chronic Fetal Hypoxia

The guinea pig is a frequently used animal model for human pregnancy complications, such as oxygen deprivation or hypoxia, which result in altered brain development. To investigate the impact of in utero chronic hypoxia on brain development, pregnant guinea pigs underwent either normoxic or hypoxic conditions at about 70 % of 65-day term gestation. After delivery, neurochemical profiles consisting of 19 metabolites and macromolecules were obtained from the neonatal cortex, hippocampus, and striatum from birth to 12 weeks postpartum using in vivo (1)H MR spectroscopy at 9.4 T. The effects of chronic fetal hypoxia on the neurochemical profiles were particularly significant at birth. However, the overall developmental trends of neurochemical concentration changes were similar between normoxic and hypoxic animals. Alterations of neurochemicals including N-acetylaspartate (NAA), phosphorylethanolamine, creatine, phosphocreatine, and myo-inositol indicate neuronal loss, delayed myelination, and altered brain energetics due to chronic fetal hypoxia. These observed neurochemical alterations in the developing brain may provide insights into hypoxia-induced brain pathology, neurodevelopmental compromise, and potential neuroprotective measures.

Neuropsychological Impairment in School-Aged Children Born to Mothers With Gestational Diabetes

The aim of this study was to determine whether school-aged children born to mothers with gestational diabetes show delays in their neuropsychological development. Several key neuropsychological characteristics of 32 children aged 7 to 9 years born to mothers with gestational diabetes were examined by comparing their performance on cognitive tasks to that of 28 children aged 8 to 10 years whose mothers had glucose levels within normal limits during pregnancy. The gestational diabetes group showed low performance on graphic, spatial, and bimanual skills and a higher presence of soft neurologic signs. Lower scores for general intellectual level and the working memory index were also evident. Our results suggest that gestational diabetes is associated with mild cognitive impairment.

Phlebotomy-induced anemia alters hippocampal neurochemistry in neonatal mice

BACKGROUND

Phlebotomy-induced anemia (PIA) is common in preterm infants. The hippocampus undergoes rapid differentiation during late fetal/early neonatal life and relies on adequate oxygen and iron to support oxidative metabolism necessary for development. Anemia shortchanges these two critical substrates, potentially altering hippocampal development and function.

METHODS

PIA (hematocrit <25%) was induced in neonatal mice pups from postnatal day (P)3 to P14. Neurochemical concentrations in the hippocampus were determined using in vivo (1)H NMR spectroscopy at 9.4T and compared with control animals at P14. Gene expression was assessed using quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

PIA decreased brain iron concentration, increased hippocampal lactate and creatine concentrations, and decreased phosphoethanolamine (PE) concentration and the phosphocreatine/creatine ratio. Hippocampal transferrin receptor (Tfrc) gene expression was increased, while the expression of calcium/calmodulin-dependent protein kinase type IIα (CamKIIα) was decreased in PIA mice.

CONCLUSION

This clinically relevant model of neonatal anemia alters hippocampal energy and phospholipid metabolism and gene expression during a critical developmental period. Low target hematocrits for preterm neonates in the neonatal intensive care unit (NICU) may have potential adverse neural implications.

Differential Effects of Intrauterine Growth Restriction on the Regional Neurochemical Profile of the Developing Rat Brain

Intrauterine growth restricted (IUGR) infants are at increased risk for neurodevelopmental deficits that suggest the hippocampus and cerebral cortex may be particularly vulnerable. Evaluate regional neurochemical profiles in IUGR and normally grown (NG) 7-day old rat pups using in vivo ¹H magnetic resonance (MR) spectroscopy at 9.4 T. IUGR was induced via bilateral uterine artery ligation at gestational day 19 in pregnant Sprague-Dawley dams. MR spectra were obtained from the cerebral cortex, hippocampus and striatum at P7 in IUGR (N = 12) and NG (N = 13) rats. In the cortex, IUGR resulted in lower concentrations of phosphocreatine, glutathione, taurine, total choline, total creatine (P < 0.01) and [glutamate]/[glutamine] ratio (P < 0.05). Lower taurine concentrations were observed in the hippocampus (P < 0.01) and striatum (P < 0.05). IUGR differentially affects the neurochemical profile of the P7 rat brain regions. Persistent neurochemical changes may lead to cortex-based long-term neurodevelopmental deficits in human IUGR infants.

Advanced magnetic resonance spectroscopy and imaging techniques applied to brain development and animal models of perinatal injury

Magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) are widely used in the field of brain development and perinatal brain injury. Due to technical progress the magnetic field strength (B0) of MR systems has continuously increased, favoring (1)H-MRS with quantification of up to 18 metabolites in the brain and short echo time (TE) MRI sequences including phase and susceptibility imaging. For longer TE techniques including diffusion imaging modalities, the benefits of higher B0 have not been clearly established. Nevertheless, progress has also been made in new advanced diffusion models that have been developed to enhance the accuracy and specificity of the derived diffusion parameters. In this review, we will describe the latest developments in MRS and MRI techniques, including high-field (1)H-MRS, phase and susceptibility imaging, and diffusion imaging, and discuss their application in the study of cerebral development and perinatal brain injury.

Rare complications of pediatric diabetic ketoacidosis

The incidence of type 1 diabetes (T1D) among youth is steadily increasing across the world. Up to a third of pediatric patients with T1D present with diabetic ketoacidosis, a diagnosis that continues to be the leading cause of death in this population. Cerebral edema is the most common rare complication of diabetic ketoacidosis in children. Accordingly, treatment and outcome measures of cerebral edema are vastly researched and the pathophysiology is recently the subject of much debate. Nevertheless, cerebral edema is not the only sequela of diabetic ketoacidosis that warrants close monitoring. The medical literature details various other complications in children with diabetic ketoacidosis, including hypercoagulability leading to stroke and deep vein thrombosis, rhabdomyolysis, pulmonary and gastrointestinal complications, and long-term memory dysfunction. We review the pathophysiology, reported cases, management, and outcomes of each of these rare complications in children. As the incidence of T1D continues to rise, practitioners will care for an increasing number of pediatric patients with diabetic ketoacidosis and should be aware of the various systems that may be affected in both the acute and chronic setting.

Postnatal treadmill exercise alleviates short-term memory impairment by enhancing cell proliferation and suppressing apoptosis in the hippocampus of rat pups born to diabetic rats

During pregnancy, diabetes mellitus exerts detrimental effects on the development of the fetus, especially the central nervous system. In the current study, we evaluated the effects of postnatal treadmill exercise on short-term memory in relation with cell proliferation and apoptosis in the hippocampus of rat pups born to streptozotocin (STZ)-induced diabetic maternal rats. Adult female rats were mated with male rats for 24 h. Two weeks after mating, the pregnant female rats were divided into two groups: control group and STZ injection group. The pregnant rats in the STZ injection group were administered 40 mg/kg of STZ intraperitoneally. After birth, the rat pups were divided into the following four groups: control group, control with postnatal exercise group, maternal STZ-injection group, and maternal STZ-injection with postnatal exercise group. The rat pups in the postnatal exercise groups were made to run on a treadmill for 30 min once a day, 5 times per week for 2 weeks beginning 4 weeks after birth. The rat pups born to diabetic rats were shown to have short-term memory impairment with suppressed cell proliferation and increased apoptosis in the hippocampal dentate gyrus. Postnatal treadmill exercise alleviated short-term memory impairment by increased cell proliferation and suppressed apoptosis in the rat pups born to diabetic rats. These findings indicate that postnatal treadmill exercise may be used as a valuable strategy to ameliorate neurodevelopmental problems in children born to diabetics.

Neonatal hypoxia, hippocampal atrophy, and memory impairment: evidence of a causal sequence

Neonates treated for acute respiratory failure experience episodes of hypoxia. The hippocampus, a structure essential for memory, is particularly vulnerable to such insults. Hence, some neonates undergoing treatment for acute respiratory failure might sustain bilateral hippocampal pathology early in life and memory problems later in childhood. We investigated this possibility in a cohort of 40 children who had been treated neonatally for acute respiratory failure but were free of overt neurological impairment. The cohort had mean hippocampal volumes (HVs) significantly below normal control values, memory scores significantly below the standard population means, and memory quotients significantly below those predicted by their full scale IQs. Brain white matter volume also fell below the volume of the controls, but brain gray matter volumes and scores on nonmnemonic neuropsychological tests were within the normal range. Stepwise linear regression models revealed that the cohort's HVs were predictive of degree of memory impairment, and gestational age at treatment was predictive of HVs: the younger the age, the greater the atrophy. We conclude that many neonates treated for acute respiratory failure sustain significant hippocampal atrophy as a result of the associated hypoxia and, consequently, show deficient memory later in life.

Metabolomic analysis of cerebrospinal fluid indicates iron deficiency compromises cerebral energy metabolism in the infant monkey

Iron deficiency anemia affects many pregnant women and young infants worldwide. The health impact is significant, given iron's known role in many body functions, including oxidative and lipid metabolism, protein synthesis and brain neurochemistry. The following research determined if (1)H NMR spectroscopy-based metabolomic analysis of cerebrospinal fluid (CSF) could detect the adverse influence of early life iron deficiency on the central nervous system. Using a controlled dietary model in 43 infant primates, distinct differences were found in spectra acquired at 600 MHz from the CSF of anemic monkeys. Three metabolite ratios, citrate/pyruvate, citrate/lactate and pyruvate/glutamine ratios, differed significantly in the iron deficient infant and then normalized following the consumption of dietary iron and improvement of clinical indices of anemia in the heme compartment. This distinctive metabolomic profile associated with anemia in the young infant indicates that CSF can be employed to track the neurological effects of iron deficiency and benefits of iron supplementation.

Iron deficiency on neuronal function

Because of the intrinsic ability of iron to catalyze the formation of reactive oxygen species, it has been associated with oxidative stress and neurodegenerative diseases. However, iron deficiency (ID) also negatively impacts various functions of the brain, suggesting that iron plays an important physiological role in neuronal processes such as myelination, synaptogenesis, behavior and synaptic plasticity (SP). ID not only produces changes in the hippocampus, striatum, amygdale or prefrontal cortex, it also affects the interaction among these systems. In both humans and rodents, the perturbations of these structures are associated to cognitive deficits. These cognitive alterations have been well correlated with changes in neural plasticity, the possible cellular substrate of memory and learning. Given that SP is strongly affected by early ID and the lasting-neurological consequences remain even after ID has been corrected, it is important to prevent ID as well as to seek effective therapeutic interventions that reduce or reverse the long-term effects of the ID in the nervous system. This review will give an overview of the literature on the effects of iron deficit in neuronal functions such as behavior, neurotransmission and SP. We also discuss our recent data about the possible oxidative effect of iron on the mechanisms involved in neural plasticity.

Evidence of endoplasmic reticulum stress and protein synthesis inhibition in the placenta of non-native women at high altitude

Pregnancy at high altitude is associated with a reduction in birth weight of ∼100 g/1000 m of ascent. The underlying mechanisms are unclear but may involve alteration in energy-demanding activities, such as protein synthesis. To test this hypothesis, both in vivo and in vitro approaches were used. Placental tissues from pregnant women residing at 3100 m were studied, and placental cells were incubated under hypoxia. In the 3100-m placentas, we observed dilation of endoplasmic reticulum (ER) cisternae, increased phosphorylation of eukaryotic initiation factor 2 subunit α (P-eIF2α), reduced AKT phosphorylation, and reduced P-4E-BP1 but increased 4E-BP1 protein compared to sea level controls. These findings suggest the presence of ER stress and protein synthesis inhibition. Hypoxia (1% O(2)) reduced proliferation of trophoblast-like JEG-3 cells, BeWo cells, and placental fibroblasts by ∼40, ∼60, and ∼18%, respectively. Sublethal dosage of salubrinal, an eIF2α phosphatase inhibitor, increased P-eIF2α and reduced BeWo cell and placental fibroblast proliferation by ∼50%. Administration of the PI-3K inhibitor LY294002 also reduced JEG-3 proliferation. Our results demonstrate that exposure to chronic hypobaric hypoxia causes mild placental ER stress, which, in turn, modulates protein synthesis and slows proliferation. These effects may account for the reduced placental villous volume, and contribute to the low birth weight that typifies high-altitude populations.

Postnatal morphine administration alters hippocampal development in rats

Morphine is frequently used as an analgesic and sedative in preterm infants. Adult rats exposed to morphine have an altered hippocampal neurochemical profile and decreased neurogenesis in the dentate gyrus of the hippocampus. To evaluate whether neonatal rats are similarly affected, rat pups were injected twice daily with 2 mg/kg morphine or normal saline from postnatal days 3 to 7. On postnatal day 8, the hippocampal neurochemical profile was determined using in vivo (1)H NMR spectroscopy. The mRNA and protein concentrations of specific analytes were measured in hippocampus, and cell division in dentate gyrus was assessed using bromodeoxyuridine. The concentrations of γ-aminobutyric acid (GABA), taurine, and myo-insotol were decreased, whereas concentrations of glutathione, phosphoethanolamine, and choline-containing compounds were increased in morphine-exposed rats relative to control rats. Morphine decreased glutamic acid decarboxylase enzyme levels and myelin basic protein mRNA expression in the hippocampus. Bromodeoxyuridine labeling in the dentate gyrus was decreased by 60-70% in morphine-exposed rats. These results suggest that recurrent morphine administration during brain development alters hippocampal structure.

Measuring multiple neurochemicals and related metabolites in blood and brain of the rhesus monkey by using dual microdialysis sampling and capillary hydrophilic interaction chromatography-mass spectrometry

In vivo measurement of multiple functionally related neurochemicals and metabolites (NMs) is highly interesting but remains challenging in the field of basic neuroscience and clinical research. We present here an analytical method for determining five functionally and metabolically related polar substances, including acetylcholine (quaternary ammonium), lactate and pyruvate (organic acids), as well as glutamine and glutamate (amino acids). These NMs are acquired from samples of the brain and the blood of non-human primates in parallel by dual microdialysis, and subsequently analyzed by a direct capillary hydrophilic interaction chromatography (HILIC)-mass spectrometry (MS) based method. To obtain high sensitivity in electrospray ionization (ESI)-MS, lactate and pyruvate were detected in negative ionization mode whereas the other NMs were detected in positive ionization mode during each HILIC-MS run. The method was validated for linearity, the limits of detection and quantification, precision, accuracy, stability and matrix effect. The detection limit of acetylcholine, lactate, pyruvate, glutamine, and glutamate was 150 pM, 3 μM, 2 μM, 5 nM, and 50 nM, respectively. This allowed us to quantitatively and simultaneously measure the concentrations of all the substances from the acquired dialysates. The concentration ratios of both lactate/pyruvate and glutamine/glutamate were found to be higher in the brain compared to blood (p < 0.05). The reliable and simultaneous quantification of these five NMs from brain and blood samples allows us to investigate their relative distribution in the brain and blood, and most importantly paves the way for future non-invasive studies of the functional and metabolic relation of these substances to each other.

Chronic hypoxia impairs murine hippocampal development and depletes the postnatal progenitor pool by attenuating mammalian target of rapamycin signaling

Chronic hypoxia (CH) is a major risk factor for impaired cognitive function in various disease states, particularly in the context of cyanotic congenital heart disease. Although most brain development occurs prenatally, the dentate gyrus (DG) of the hippocampus harbors progenitor stem cells that contribute to its ongoing development postnatally. It is unclear how exposure to CH might affect postnatal hippocampal development, so we used a transgenic mouse that expresses enhanced green fluorescent protein (eGFP) within this progenitor population to determine the effect of CH on the DG. We find that exposure to 10% oxygen from postnatal d 3 to 28 results in a smaller DG with long-term impairment of hippocampal neurogenesis. Because the mammalian target of rapamycin (mTOR) pathway is a well-known regulator of cell proliferation and growth and is sensitive to hypoxia, we investigated its activation on exposure to CH and find it to be attenuated specifically in neural progenitor cells. Systemic inhibition of the mTOR pathway using rapamycin also caused impairment of hippocampal neurogenesis that mimics exposure to CH. Our findings demonstrate that CH results in long-term impairment of hippocampal neurogenesis and is mediated, in part, by attenuation of the mTOR pathway.

Developmental and metabolic brain alterations in rats exposed to bisphenol A during gestation and lactation

In recent years, considerable research has focused on the biological effect of endocrine-disrupting chemicals. Bisphenol A (BPA) has been implicated as an endocrine-disrupting chemical (EDC) due to its ability to mimic the action of endogenous estrogenic hormones. The aim of this study was to assess the effect of perinatal exposure to BPA on cerebral structural development and metabolism after birth. BPA (1mg/l) was administered in the drinking water of pregnant dams from day 6 of gestation until pup weaning. At postnatal day 20, in vivo metabolite concentrations in the rat pup hippocampus were measured using high field proton magnetic resonance spectroscopy. Further, brain was assessed histologically for growth, gross morphology, glial and neuronal development and extent of myelination. Localized proton magnetic resonance spectroscopy ((1)H MRS) showed in the BPA-exposed rat a significant increase in glutamate concentration in the hippocampus as well as in the Glu/Asp ratio. Interestingly these two metabolites are metabolically linked together in the malate-aspartate metabolic shuttle. Quantitative histological analysis revealed that the density of NeuN-positive neurons in the hippocampus was decreased in the BPA-treated offspring when compared to controls. Conversely, the density of GFAP-positive astrocytes in the cingulum was increased in BPA-treated offspring. In conclusion, exposure to low-dose BPA during gestation and lactation leads to significant changes in the Glu/Asp ratio in the hippocampus, which may reflect impaired mitochondrial function and also result in neuronal and glial developmental alterations.

Consequences of low neonatal iron status due to maternal diabetes mellitus on explicit memory performance in childhood

Diabetic pregnancies are characterized by chronic metabolic insults, including iron deficiency, that place the developing brain at risk for memory impairment later in life. A behavioral recall paradigm coupled with electrophysiological measures was used to assess the longevity of these effects in 40 3(1/2)-year-old children. When memory demands were high, recall was significantly impaired in the at-risk group and correlated with perinatal measures of iron. Electrophysiological results suggested both encoding and retrieval processes were compromised. These findings support the hypothesis that prenatal iron deficiency leads to alterations in neural development that have a lasting impact on memory ability.

Diabetic ketoacidosis and memory dysfunction in children with type 1 diabetes

OBJECTIVE

We tested the hypothesis that diabetic ketoacidosis (DKA) results in memory deficits typical of hypoxic/ischemic injury because recent studies suggest that cerebral metabolic changes similar to those observed in hypoxic/ischemic cerebral injury are observed in children with DKA, even without symptoms suggesting cerebral injury.

STUDY DESIGN

Thirty-three children with type 1 diabetes mellitus (T1DM) and a history of DKA and 29 children with T1DM without a history of DKA were enrolled from an academic hospital pediatric endocrinology clinic. These groups were comparable on demographic and disease-related variables. These groups' ability to recall events in association with specific details, the memory function most directly affected by mild hypoxia/ischemia, was compared on 2 tasks (ie, event-color associations and event-spatial position associations).

RESULTS

In multivariate analyses controlling for other critical variables, children with DKA history had significantly lower rates of accurate memory on both tasks (mean, 0.34 +/- 0.13 on the color task and 0.57 +/- 0.15 on the spatial task) than did children without DKA history (mean, 0.44 +/- 0.11 and 0.65 +/- 0.18, P < .01).

CONCLUSIONS

DKA disrupts memory function, underscoring the importance of DKA prevention when T1DM is known and prompt diagnosis of children with new onset of T1DM.

Human placental metabolic adaptation to chronic hypoxia, high altitude: hypoxic preconditioning

We have previously demonstrated placentas from laboring deliveries at high altitude have lower binding of hypoxia-inducible transcription factor (HIF) to DNA than those from low altitude. It has recently been reported that labor causes oxidative stress in placentas, likely due to ischemic hypoxic insult. We hypothesized that placentas of high-altitude residents acquired resistance, in the course of their development, to oxidative stress during labor. Full-thickness placental tissue biopsies were collected from laboring vaginal and nonlaboring cesarean-section term (37–41 wk) deliveries from healthy pregnancies at sea level and at 3,100 m. After freezing in liquid nitrogen within 5 min of delivery, we quantified hydrophilic and lipid metabolites using ³¹P and ¹H NMR metabolomics. Metabolic markers of oxidative stress, increased glycolysis, and free amino acids were present in placentas following labor at sea level, but not at 3,100 m. In contrast, at 3,100 m, the placentas were characterized by the presence of concentrations of stored energy potential (phosphocreatine), antioxidants, and low free amino acid concentrations. Placentas from pregnancies at sea level subjected to labor display evidence of oxidative stress. However, laboring placentas at 3,100 m have little or no oxidative stress at the time of delivery, suggesting greater resistance to ischemia-reperfusion. We postulate that hypoxic preconditioning might occur in placentas that develop at high altitude.

Neurochemical changes after acute binge toluene inhalation in adolescent and adult rats: a high-resolution magnetic resonance spectroscopy study

Inhalant abuse in young people is a growing public health concern. We reported previously that acute toluene intoxication in young rats, using a pattern of exposures that approximate abuse patterns of inhalant use in humans, significantly altered neurochemical measures in select brain regions. In this study, adolescent and young adult rats were exposed similarly to an acute (2 x 15 min), high dose (8000-12,000 ppm) of toluene and high-resolution magic angle spinning proton magnetic resonance spectroscopy (HR-MAS 1H-MRS) was used to assess neurochemical profiles of tissue samples from a number of brain regions collected immediately following solvent exposure. The current investigation focused on N-acetyl-aspartate (NAA), choline-containing compounds, creatine, glutamate, GABA, and glutamine. Contrary to our predictions, no significant alterations were found in the levels of NAA, choline, creatine, glutamate, or glutamine in adolescent animals. In contrast to these minimal effects in adolescents, binge toluene exposure altered several neurochemical parameters in young adult rats, including decreased levels of choline and GABA in the frontal cortex and striatum and lowered glutamine and NAA levels in the frontal cortex. One of the more robust findings was a wide-ranging increase in lactate after toluene exposure in adult animals, an effect not observed in adolescents. These age-dependent effects of toluene are distinct from those reported previously in juvenile rats and suggest a developmental difference in vulnerability to the effects of inhalants. Specifically, the results suggest that the neurochemical response to toluene in adolescents is attenuated compared to adults, and imply an association between these neurochemical differences and age-influenced differences in solvent abuse in humans.

Why iron deficiency is important in infant development

Infants who experience iron deficiency during the first 6-12 mo of life are likely to experience persistent effects of the deficiency that alter functioning in adulthood. A lack of sufficient iron intake may significantly delay the development of the central nervous system as a result of alterations in morphology, neurochemistry, and bioenergetics. Depending on the stage of development at the time of iron deficiency, there may be an opportunity to reverse adverse effects, but the success of repletion efforts appear to be time dependent. Publications in the past several years describe the emerging picture of the consequences of iron deficiency in both human and animal studies. The mechanisms for iron accumulation in the brain and perhaps redistribution are being understood. The data in human infants are consistent with altered myelination of white matter, changes in monoamine metabolism in striatum, and functioning of the hippocampus. Rodent studies also show effects of iron deficiency during gestation and lactation that persist into adulthood despite restoration of iron status at weaning. These studies indicate that gestation and early lactation are likely critical periods when iron deficiency will result in long-lasting damage.

Gene-environment interaction and covariation in schizophrenia: the role of obstetric complications

While genetic factors account for a significant proportion of liability to schizophrenia, a body of evidence attests to a significant environmental contribution. Understanding the mechanisms through which genetic and environmental factors coalesce in influencing schizophrenia is critical for elucidating the pathways underlying psychotic illness and for developing primary prevention strategies. Although obstetric complications (OCs) remain among the most well-documented environmental indicators of risk for schizophrenia, the pathogenic role they play in the etiology of schizophrenia continues to remain poorly understood. A question of major importance is do these factors result from a genetic diathesis to schizophrenia (as in gene-environment covariation), act additively or interactively with predisposing genes for the disorder in influencing disease risk, or independently cause disease onset? In this review, we evaluate 3 classes of OCs commonly related to schizophrenia including hypoxia-associated OCs, maternal infection during pregnancy, and maternal stress during pregnancy. In addition, we discuss several mechanisms by which OCs impact on genetically susceptible brain regions, increasing constitutional vulnerability to neuromaturational events and stressors later in life (ie, adolescence), which may in turn contribute to triggering psychosis.

Neonatal alcohol-induced region-dependent changes in rat brain neurochemistry measured by high-resolution magnetic resonance spectroscopy

BACKGROUND

Maternal drinking during pregnancy can lead to a range of deleterious outcomes in the developing offspring that have been collectively termed fetal alcohol spectrum disorders (FASDs). There is interest and recognized value in using non-invasive neuroimaging techniques such as magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) to characterize, respectively, structural and biochemical alterations in individuals with FASDs. To date, however, results with MRS have been inconsistent regarding the degree and/or nature of abnormalities.

METHODS

High-resolution magic angle spinning (HR-MAS) proton ((1)H) MRS is an ex vivo neuroimaging technique that can acquire spectra in small punches of intact tissue, providing clinically relevant neurochemical information about discrete brain regions. In this study, HR-MAS (1)H MRS was used to examine regional neurochemistry in frontal cortex, striatum, hippocampus, and cerebellum of young rats previously exposed to ethanol as neonates. Key neurochemicals of interest included N-acetyl-aspartate (NAA), glutamate, GABA, glutamine, creatine, choline and myo-inositol.

RESULTS

Daily neonatal alcohol exposure from postnatal day 4 (PN4) through PN9 significantly reduced levels of NAA and taurine in the cerebellum and striatum, and induced sex-dependent reductions in cerebellar glutamate when measured on PN16. In addition, myo-inositol was significantly increased in cerebellum. The frontal cortex and hippocampus were virtually unaffected by this neonatal alcohol exposure.

CONCLUSION

Results of this research may have implications for understanding the underlying neurobiology associated with FASDs and aid in testing treatments in the future. Ongoing studies are assessing the developmental persistence of and/or maturational recovery from these changes.

Melatonin attenuates hypoxia-induced ultrastructural changes and increased vascular permeability in the developing hippocampus

Hypoxic injury in the perinatal period may be involved in damaging the developing hippocampus. The damage may be mediated by excess production of vascular endothelial growth factor (VEGF) and nitric oxide (NO). We examined the hippocampus of neonatal Wistar rats subjected to hypoxia for VEGF and NO production. The mRNA and protein expression of hypoxia inducible factor-1alpha, endothelial, neuronal, inducible nitric oxide synthase and VEGF was found to be up-regulated significantly after the hypoxic exposure. Tissue VEGF concentration and NO production were also increased. By electron microscopy, swollen dendrites, vacuolated axons and hypertrophic astrocyte end feet associated with blood vessels were observed in hypoxic animals. In hypoxic rats, the passage of rhodamine isothiocyanate (RhIC) and horseradish peroxidase, administered intraperitoneally or intravenously, was observed through vascular walls. Furthermore, immunoglobulin G was localized in the neuropil and neurons. We suggest that increased VEGF and NO production in hypoxia had resulted in increased vascular permeability, leading to structural alteration of the dendrites and axons. Melatonin administration reduced VEGF and NO levels as well as leakage of RhIC, suggesting that it has a therapeutic potential in reducing hypoxia-associated damage in the developing hippocampus.

Effects of chronic hypoxia in developing rats on dendritic morphology of the CA1 subarea of the hippocampus and on fear-potentiated startle

Chronic hypoxia (CH) present in infants with cyanotic congenital heart disease may be responsible for subsequent cognitive deficits seen in these children. In a rat model of CH [10% O(2) between postnatal day (P) 3 and 28], we have demonstrated significant alterations in energy metabolism and excitatory neurotransmission in the developing hippocampus. These alterations may adversely affect dendritic morphology, which is a highly energy-dependent and excitatory neurotransmitter-mediated event, and hippocampus-mediated behaviors. We measured the apical segment length of dendrites in pyramidal neurons of the CA1 region of the hippocampus using microtubule-associated protein-2 (MAP-2) histochemistry on P28 while the animals were hypoxic (n=8 in CH and n=6 in control), and on P56 after the animals had been normoxic for 4 weeks (n=8/group). We also compared dorsal hippocampus-dependent trace fear conditioning and dorsal hippocampus-independent delay fear conditioning on P56. Developmental trajectory of the apical segment length was similar in CH and controls, decreasing between P28 and P56. However, when compared with the controls, the apical segment length was longer in the CH group on both P28 [55.11+/-2.30 microm (CH) vs. 40.52+/-1.20 microm (control), p<0.001] and P56 [44.01+/-1.56 microm (CH) vs. 31.75+/-1.31 microm (control), p<0.001], suggesting the persistence of an immature dendritic architecture. Both trace and delay fear conditioning were decreased in the CH group, suggesting functional abnormality beyond the dorsal hippocampus. These structural and functional alterations may contribute to the cognitive deficits seen in infants at risk for CH.

Perinatal hypoxia induces subsequent retinal degeneration in the offspring of ovoviviparous fish, Xiphophorous maculates

OBJECTIVE

This experiment evaluated the perinatal hypoxic effect on the retina of offspring of the ovoviviparous fish.

ANIMAL STUDIED

The ovoviviparous fish Xiphophorous maculates was used for the experiment.

PROCEDURE

The mothers were kept in a hypoxic environment of 3.5% oxygen for 6 h, starting 30 h before hatching. Subsequently, the retinae of the offspring were fixed, sectioned at 6 microm and evaluated microscopically from the age of 1 to 35 days.

RESULTS

Degeneration of the outer nuclear layer of the retina was noted on the 3rd day and severe retinal degeneration was observed on the 35th day. Immunocytochemistry confirmed apoptosis by TUNEL reaction. There was no difference in neovascularization, as revealed by vascular endothelial growth factor, between controls (group 1) and hypoxic fish (group 2).

CONCLUSIONS

Perinatal hypoxia could have long-lasting effects on the central nervous system in some species.

Cerebral glutamine and glutamate levels in relation to compromised energy metabolism: a microdialysis study in subarachnoid hemorrhage patients

Astrocytic glutamate (Glt) uptake keeps brain interstitial Glt levels low. Within the astrocytes Glt is converted to glutamine (Gln), which is released and reconverted to Glt in neurons. The Glt-Gln cycle is energy demanding and impaired energy metabolism has been suggested to cause low interstitial Gln/Glt ratios. Using microdialysis (MD) measurements from visually noninjured cortex in 33 neurointensive care patients with subarachnoid hemorrhage, we have determined how interstitial Glt and Gln, as a reflection of the Glt-Gln cycle turnover, relate to perturbed energy metabolism. A total of 3703 hourly samples were analyzed. The lactate/pyruvate (L/P) ratios correlated to the Gln/Glt ratios (r=-0.66), but this correlation was not stronger than the correlation between L/P and Glt (r=0.68) or the correlation between lactate and Glt (r=0.65). A novel observation was a linear relationship between interstitial pyruvate and Gln (r=0.52). There were 13 periods (404 h) of 'energy crisis', defined by L/P ratios above 40. All were associated with high interstitial Glt levels. Periods with L/P ratios above 40 and low pyruvate levels were associated with decreased interstitial Gln levels, suggesting ischemia and failing astrocytic Gln synthesis. Periods with L/P ratios above 40 and normal or high pyruvate levels were associated with increased interstitial Gln levels, which may represent an astrocytic hyperglycolytic response to high interstitial Glt levels. The results imply that moderately elevated L/P ratios cannot always be interpreted as failing energy metabolism and that interstitial pyruvate levels may discriminate whether or not there is sufficient astrocytic capacity for Glt-Gln cycling in the brain.