Normal Brain Growth Research Articles

Delivering Drugs Into the Brain: Barriers and Possibilities

Delivering Drugs Into the Brain: Barriers and Possibilities

Magnetic resonance microscopy-based analyses of the brains of normal and ethanol-exposed fetal mice.

The application of magnetic resonance microscopy (MRM) to the study of normal and abnormal prenatal mouse development has facilitated discovery of dysmorphology following prenatal ethanol insult. The current analyses extend this work, providing a regional brain volume-based description of normal brain growth and illustrating the consequences of gestational day (GD) 10 ethanol exposure in the fetal mouse. To assess normal growth, control C57Bl/6J fetuses collected on GD 16, GD 16.5, and GD 17 were scanned using a 9.4-T magnet, resulting in 29-μm isotropic resolution images. For the ethanol teratogenicity studies, C57Bl/6J dams were administered intraperitoneal ethanol (2.9 g/kg) at 10 days, 0 hr, and 10 days, 4 hr, after fertilization, and fetuses were collected for analyses on GD 17. From individual MRM scans, linear measurements and regional brain volumes were determined and compared. In control fetuses, each of the assessed brain regions increased in volume, whereas ventricular volumes decreased between GD 16 and GD 17. Illustrating a global developmental delay, prenatal ethanol exposure resulted in reduced body volumes, crown-rump lengths, and a generalized decrease in regional brain volumes compared with GD 17 controls. However, compared with GD 16.5, morphologically matched controls, ethanol exposure resulted in volume increases in the lateral and third ventricles as well as a disproportionate reduction in cortical volume. The normative data collected in this study facilitate the distinction between GD 10 ethanol-induced developmental delay and frank dysmorphology. This work illustrates the utility of MRM-based analyses for developmental toxicology studies and extends our knowledge of the stage-dependency of ethanol teratogenesis.

C-myc and N-myc in the developing brain

Murine knockouts (KO) of myc genes have provided substantial insight into not only their normal functions during development, but also shed light on their tumorigenic functions when they are misregulated. c-myc and N-myc genes both are essential neural stem and precursor cells (NSC) for normal mouse brain growth[1,2]. The fact that mutation of N-myc also causes microcephaly humans Feingold Syndrome[3], suggests common Myc-regulated pathways are at work during mouse and human brain growth. Earlier studies indicate that N-Myc drives brain growth by maintaining widespread domains of euchromatin [4] required for NSC proliferation and pluripotency. Such events may be locked in during tumorigenesis driving Myc-associated neuronal tumors such as neuroblastoma and medulloblastoma as N-Myc regulates global euchromatin neuroblastoma as well [5]. A substantial obstacle to understanding the respective functions of different myc genes neurogenesis is their redundancy and coexpression. To overcome these problems and explore Myc function brain development as well as tumorigenesis, here we generated a double KO (DKO) for c- and N-myc using nestin-cre. Overall brain growth is strongly impaired DKO mice, a phenotype associated with decreased cell cycling and migration of NSC, which are profoundly decreased number. Interestingly, the midbrain of DKO mice appeared unaffected by loss of c- and N-myc, suggesting that L-myc controls midbrain growth, while both c- and N-myc regulate fore- and hindbrain development (Figure ​(Figure1).1). Overall, N-myc is the main conductor of brain growth. Surprisingly, survival was not clearly affected by the loss of c- and N-myc NSC. Changes gene expression the DKO include downregulation of genes involved protein and nucleotide metabolism, mitosis, and chromatin structure as well as upregulation of genes associated with differentiation. Very few changes gene expression were observed the midbrain, further supporting the notion that c- and N-myc are dispensable for midbrain development. These are the first vivo studies of Myc regulation of gene expression the nervous system. Our findings suggest a model of neuronal tumorigenesis which excess myc aberrantly enforces a developmentally active chromatin state characterized by rapid cell cycling, hyperactive metabolism, and blocked differentiation. We refer the readers to the full text paper [6]. Figure 1. Model of regulation of brain architecture by the myc gene family.

Turner syndrome and schizophrenia: A further hint for the role of the X-chromosome in the pathogenesis of schizophrenic disorders

Abnormalities of sex chromosomes are associated with various forms of neuropsychiatric disorders, such as schizophrenia. Turner syndrome occurs approximately threefold more frequently in female schizophrenics compared to the general female population. A single case is reported. We report on a case of a 41-year-old woman with Turner syndrome, schizophrenia, mental retardation, and hypothyroidism. A polymorphism of the HOPA gene within Xq13 termed HOPA12bp is associated with schizophrenia, mental retardation, and hypothyroidism. Interestingly, Xq13 is the X-chromosome region that contains the X-inactivation center and a gene escaping X-inactivation whose gene product may be involved in the X-inactivation process as well as in the pathogenesis of sex chromosome anomalies such as Turner syndrome. These genes that escape X-inactivation may produce their gene products in excess, influencing normal brain growth and differentiation. Our case gives a further hint for an involvement of the X-chromosome in the pathogenesis of schizophrenia.

Cerebellar Brain-Derived Neurotrophic Factor, Nerve Growth Factor, and Neurotrophin-3 Expression in Male and Female Rats Is Differentially Affected by Hypergravity Exposure During Discrete Developmental Periods

We previously reported that the effects of perinatal exposure to hypergravity on cerebellum and motor functions in rat neonates are strongly dependent on the specific developmental period of exposure. In the present study, we explored the hypothesis that neurodevelopmental changes are associated with altered expression of brain neurotrophins critical for normal brain growth and differentiation. We compared the effects of hypergravity exposure during four developmental periods: period I extended from gestational day (G) 8 through G15; period II from G15 to birth, period III from birth to postnatal day (P) 6; and period IV extended from G8-P12. For comparison we used stationary control (SC) neonates not exposed to hypergravity. Neurotrophins, brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and neurotrophin 3 (NT-3) levels were measured in cerebellar homogenates prepared from postnatal day 12 male and female rat neonates using specific ELISAs. Hypergravity exposure affected individual neurotrophins differently and the effect was further determined by the period of hypergravity exposure. ANOVA showed: (1) a significant effect of the period of exposure to hypergravity on cerebellar BDNF (p = 0.009), with maximal decrease of 28.7% in males and 32.1% in females following exposure during period III; (2) a significant effect on NGF (p < 0.0001), with maximal decrease of 35.6% in male and 48.8% in female neonates following exposure during period III; (3) no statistically significant effect on NT-3 expression with a trend towards decreased expression in female rats following exposure during period IV. Although the molecular mechanisms underlying the differential neurotrophins' response to hypergravity are not clear, an altered pattern of their expression is likely to contribute to neurodevelopmental changes and impaired sensorimotor behavior in exposed neonates.

Increase in Cerebellar Neurotrophin-3 and Oxidative Stress Markers in Autism

Autism is a neurodevelopmental disorder characterized by social and language deficits, ritualistic-repetitive behaviors and disturbance in motor functions. Data of imaging, head circumference studies, and Purkinje cell analysis suggest impaired brain growth and development. Both genetic predisposition and environmental triggers have been implicated in the etiology of autism, but the underlying cause remains unknown. Recently, we have reported an increase in 3-nitrotyrosine (3-NT), a marker of oxidative stress damage to proteins in autistic cerebella. In the present study, we further explored oxidative damage in the autistic cerebellum by measuring 8-hydroxydeoxyguanosine (8-OH-dG), a marker of DNA modification, in a subset of cases analyzed for 3-NT. We also explored the hypothesis that oxidative damage in autism is associated with altered expression of brain neurotrophins critical for normal brain growth and differentiation. The content of 8-OH-dG in cerebellar DNA isolated by the proteinase K method was measured using an enzyme-linked immunosorbent assay (ELISA); neurotrophin-3 (NT-3) levels in cerebellar homogenates were measured using NT-3 ELISA. Cerebellar 8-OH-dG showed trend towards higher levels with the increase of 63.4% observed in autism. Analysis of cerebellar NT-3 showed a significant (p = 0.034) increase (40.3%) in autism. Furthermore, there was a significant positive correlation between cerebellar NT-3 and 3-NT (r = 0.83; p = 0.0408). These data provide the first quantitative measure of brain NT-3 and show its increase in the autistic brain. Altered levels of brain NT-3 are likely to contribute to autistic pathology not only by affecting brain axonal targeting and synapse formation but also by further exacerbating oxidative stress and possibly contributing to Purkinje cell abnormalities.

Dual mechanism of brain injury and novel treatment strategy in maple syrup urine disease

Maple syrup urine disease (MSUD) is an inherited disorder of branched-chain amino acid metabolism presenting with life-threatening cerebral oedema and dysmyelination in affected individuals. Treatment requires life-long dietary restriction and monitoring of branched-chain amino acids to avoid brain injury. Despite careful management, children commonly suffer metabolic decompensation in the context of catabolic stress associated with non-specific illness. The mechanisms underlying this decompensation and brain injury are poorly understood. Using recently developed mouse models of classic and intermediate maple syrup urine disease, we assessed biochemical, behavioural and neuropathological changes that occurred during encephalopathy in these mice. Here, we show that rapid brain leucine accumulation displaces other essential amino acids resulting in neurotransmitter depletion and disruption of normal brain growth and development. A novel approach of administering norleucine to heterozygous mothers of classic maple syrup urine disease pups reduced branched-chain amino acid accumulation in milk as well as blood and brain of these pups to enhance survival. Similarly, norleucine substantially delayed encephalopathy in intermediate maple syrup urine disease mice placed on a high protein diet that mimics the catabolic stress shown to cause encephalopathy in human maple syrup urine disease. Current findings suggest two converging mechanisms of brain injury in maple syrup urine disease including: (i) neurotransmitter deficiencies and growth restriction associated with branched-chain amino acid accumulation and (ii) energy deprivation through Krebs cycle disruption associated with branched-chain ketoacid accumulation. Both classic and intermediate models appear to be useful to study the mechanism of brain injury and potential treatment strategies for maple syrup urine disease. Norleucine should be further tested as a potential treatment to prevent encephalopathy in children with maple syrup urine disease during catabolic stress.

Reduce, Recycle, Reuse — Iodotyrosine Deiodinase in Thyroid Iodide Metabolism

Thyroid hormones are essential for normal brain development, growth, and metabolism. Their synthesis is dependent on a normally developed thyroid gland, an adequate nutritional intake of iodide, an...

‘State-of-the-Art’ Neonatal Cranial Ultrasound

Cranial ultrasound (cUS) provides bedside imaging access to the neonatal brain. Modern scanners and the use of various acoustic windows give detail not only of the well known pathologies met in the preterm infant, but also allow assessment of more subtle aspects of normal and abnormal brain growth and development. cUS is also very helpful in the early diagnosis of the many aetiologies of neonatal encephalopathy and seizures in the term infant and the subsequent monitoring of progress of hypoxic-ischaemic brain injury. Training issues in cUS need to be addressed.

Insulin-Like Growth Factor-I Stimulates Histone H3 and H4 Acetylation in the Brainin Vivo

IGF-I is essential to normal brain growth and exerts actions on neural stem cells and each major neural cell lineage. Whereas many studies show that IGF-I regulates gene expression, mechanisms by which it modulates transcription have not been explored. Chromatin modifications, such as histone phosphorylation, acetylation, and methylation, are known to be important initial steps in gene regulation, and acetylation of histone H3 and H4 is associated with gene activation. In this study, we show that IGF-I modulates the acetylation of H3 and H4 histones in the brain of two transgenic mouse lines and that these effects are associated with activation of the phosphoinositide 3-kinase/Akt signaling pathway. This provides evidence that the chromatin architecture modification contributes to the action of IGF-I on gene expression in the mammalian central nerve system.

Early Brain Growth

After completing this article, readers should be able to: 1. Discuss the roles of macronutrients (protein and energy) in neuronal and glial structure and neurotransmitter synthesis and function. 2. Delineate the neonates at risk for protein-energy malnutrition. 3. Characterize the neurodevelopment handicaps that occur in infants who experience intrauterine growth restriction. 4. Describe the mechanism by which protein and energy malnutrition alter the size of the brain. 5. Explain the effects of mild-to-moderate malnutrition on brain growth. Pediatric clinicians and researchers have long understood the importance of providing adequate nutritional intake to infants and children to promote appropriate neurodevelopmental outcome. Studies describing the untoward effects of nutritional microcephaly in humans date back to the seminal work of Winick and Rosso in the 1960s, ( 1) but the concept of loss of brain growth during periods of malnutrition was well known before that time. In this review, we assess the potential mechanisms by which macronutrients interact with the developing brain, including a discussion of the molecular, biochemical, structural, and behavioral effects of protein-energy malnutrition on the brain. Further, we examine the neurodevelopmental effects of clinical conditions that result in decreased head growth velocity between 24 and 40 weeks postconception, including intrauterine growth restriction (IUGR) and failure to thrive in preterm infants. Finally, we consider nutritional and non-nutritional strategies that have the potential to preserve normal brain growth. The brain is a dynamic structure throughout the lifespan ( 2) that is constantly remodeling itself, guided by the interaction between an intrinsic, apparently experience-independent set of factors and extrinsic experiences. The former frames a basic blueprint of predictable neurobehavioral milestone development that typically developing humans follow. The latter translates into the methods by which daily positive and negative experiences mold and shape the brain, providing variability in the developmental trajectory among humans. Fundamentally, within any developmental time period, …

Intracranial Volume Changes in Craniosynostotic Rabbits: Effects of Age and Surgical Correction

The premature fusion of one or more cranial sutures, termed craniosynostosis, alters normal brain growth patterns and results in compensatory changes in the cranial vault. The authors previously reported that bilateral coronal suture fusion resulted in a reduction in intracranial volume in a rabbit model of nonsyndromic, familial coronal suture synostosis. The current follow-up study involved collecting cross-sectional three-dimensional computed tomographic head scans from 142 rabbits (70 normal, 44 with uncorrected synostosis, and 28 synostosed rabbits with coronal suturectomy) at 0, 10, 25, 42, 84, and 126 days of age. Intracranial contents were reconstructed, and indirect intracranial volume was calculated. Results revealed a significant (p < 0.05) postsynostotic reduction of intracranial volume (23 percent) by 25 days of age in rabbits with uncorrected craniosynostosis compared with normal controls, which continued through 84 days of age. Also, rabbits with surgically released synostosis, using a simple strip suturectomy, showed significantly (p < 0.05) greater intracranial volume at 25 days of age compared with unoperated synostosed rabbits. However, no changes in intracranial volume were noted between 42 and 84 days of age in rabbits with surgically released synostosis, at which point their intracranial volume was 30 percent less than that in normal control rabbits. These data suggest that in rabbits with uncorrected craniosynostosis, compensatory changes in the neurocranium were not capable of compensating for the loss of sutures as growth sites. The results also showed that that surgical release of the synostosed suture improved intracranial volume in the short term (25 to 42 days) but failed to change it in the long term (42 to 84 days), possibly because of rapid resynostosis of the suturectomy site. This study suggests that surgical release of the suture fusion site alone may not be adequate to allow for normal intracranial volume growth in synostotic rabbits. For this reason, it may be efficacious to design and develop adjunct protein and gene therapies to prevent resynostosis and improve postoperative intracranial volume in craniosynostotic individuals.

A High Inorganic Phosphate Diet Perturbs Brain Growth, Alters Akt-ERK Signaling, and Results in Changes in Cap-Dependent Translation

Inorganic phosphate (Pi) plays a key role in diverse physiological functions. Recently, considerable progress has been made in our understanding of the function and regulation of the brain-specific sodium-dependent inorganic phosphate transporter 1 (NPT1), which is found to exist principally in cerebrum and cerebellum. The potential importance of Pi as a novel signaling molecule and the poor prognosis of diverse neurodegenerative diseases that involve brain-specific NPT1 have prompted us to define the pathways by which Pi affects mouse brain growth. A high phosphate diet caused an increase in serum Pi accompanied by a decrease in calcium, and a decrease in body weight coupled with a decreased relative weight of cerebellum. A high phosphate diet caused a significant increase in protein expression of NPT1, both in cerebrum and cerebellum. Additionally, the high phosphate diet increased Homo sapiens v-akt murine thymoma viral oncogene homolog 1 (Akt) phosphorylation at Ser473 in cerebrum and cerebellum, whereas suppression of Akt phosphorylation at Thr308 was observed only in cerebellum. Selective suppression of eukaryotic translation initiation factor-binding protein (eIF4E-BP1) in cerebrum was induced by high levels of Pi, which induced cap-dependent and cap-independent protein translation in cerebrum and cerebellum, respectively. Phosphorylation of extracellular regulated kinase 1 (ERK1) in comparison with that of ERK2 was significantly reduced in both cerebrum and cerebellum. High levels of Pi reduced protein expressions of proliferating cell nuclear antigen (PCNA) and cyclin D1 in cerebrum and cerebellum. In conclusion, the results indicate that high dietary Pi can perturb normal brain growth, possibly through Akt-ERK signaling in developing mice.

Susceptibility to seizure-induced injury and acquired microencephaly following intraventricular injection of saporin-conjugated 192 IgG in developing rat brain

To study the role of neurotrophin-responsive neurons in brain growth and developmental resistance to seizure-induced injury, we infused saporin-conjugated 192-IgG (192 IgG-saporin), a monoclonal antibody directed at the P75 neurotrophin receptors (p75 NTR), into the ventricles of postnatal day 8 (P8) rat pups. 7–10 days after immunotoxin treatment, loss of p75 NTR immunoreactivity was associated with depletion of basal forebrain cholinergic projection to the neocortex and hippocampus. Kainic acid (KA)-induced seizures on P15 resulted in hippocampal neuronal injury in the majority of toxin-treated animals (13/16), but only rarely in saline-injected controls (2/25) ( P < 0.001). In addition, widespread cerebral atrophy and a significant decrease in brain weight with preserved body weight were observed. Volumetric analysis of the hippocampal hilar region revealed a 2-fold reduction in perikaryal size and a 1.7-fold increase in cell packing density after 192 IgG-saporin injection. These observations indicate that neurotrophin-responsive neurons including basal forebrain magnocellular cholinergic neurons may be critical for normal brain growth and play a protective role in preventing excitotoxic neuronal injury during development.

The Sonic Hedgehog-Gli pathway regulates dorsal brain growth and tumorigenesis.

The mechanisms that regulate the growth of the brain remain unclear. We show that Sonic hedgehog (Shh) is expressed in a layer-specific manner in the perinatal mouse neocortex and tectum, whereas the Gli genes, which are targets and mediators of SHH signaling, are expressed in proliferative zones. In vitro and in vivo assays show that SHH is a mitogen for neocortical and tectal precursors and that it modulates cell proliferation in the dorsal brain. Together with its role in the cerebellum, our findings indicate that SHH signaling unexpectedly controls the development of the three major dorsal brain structures. We also show that a variety of primary human brain tumors and tumor lines consistently express the GLI genes and that cyclopamine, a SHH signaling inhibitor, inhibits the proliferation of tumor cells. Using the in vivo tadpole assay system, we further show that misexpression of GLI1 induces CNS hyperproliferation that depends on the activation of endogenous Gli1 function. SHH-GLI signaling thus modulates normal dorsal brain growth by controlling precursor proliferation, an evolutionarily important and plastic process that is deregulated in brain tumors.

Molecular genetics of human microcephaly

Human microcephaly comprises a heterogeneous group of conditions that are characterized by a failure of normal brain growth. Microcephaly can be caused by many injurious or degenerative conditions, or by developmental malformations in which the growth of the brain is impaired as a result of defects in pattern formation, cell proliferation, cell survival, cell differentiation, or cell growth. These latter forms of congenital microcephaly are frequently inherited, usually as recessive traits, and are associated with mental retardation and sometimes epilepsy. Some of the genes that cause congenital microcephaly are likely to control crucial aspects of neural development, and may also be involved in the evolutionary explosion of cortical size that characterizes primates. There has recently been a rapid advance in the use of genetic mapping techniques to identify genetic loci responsible for microcephaly. Although several loci have been mapped, the condition is clearly genetically and clinically heterogeneous.

The role of long-chain polyunsaturated fatty acids in infant cognitive development

Dietary long-chain polyunsaturated fatty acids (LCPUFA) in infancy are necessary for normal brain growth and development, and may play an important role in the development of infant cognition. Several randomized, controlled studies have evaluated the effects of feeding both term and preterm infants formula containing LCPUFA or no LCPUFA on a variety of measures of cognitive behaviour. Studies of the relation of LCPUFA to performance on tests of psychomotor development have produced inconsistent results, with supplemented infants demonstrating either higher scores or no differences in comparison to controls. This pattern suggests that global tests of development may be insufficiently sensitive for detecting the effects of LCPUFA on infant cognitive function. In contrast, studies assessing the influence of LCPUFA on development of specific cognitive behaviours have shown a significant advantage for supplemented infants on measures of visual attention and problem solving. These results suggest that LCPUFA may enhance more efficient information processing or attention regulation in infants. Whether there are any long-term effects of dietary LCPUFA in infancy on childhood cognition is not known.

Normal intelligence with severe insulin-like growth factor I deficiency due to growth hormone receptor deficiency: a controlled study in a genetically homogeneous population.

Superior school performance was reported for 52 Ecuadorian probands with severe deficiency of insulin-like growth factor I (IGF-I) due to GH receptor deficiency (GHRD) resulting from homozygosity for the E180 splice mutation of the GHR. In contrast, subnormal intelligence was reported in a study of 18 genetically heterogeneous Israeli patients, attributed to frequent hypoglycemia or IGF-I dependence of brain development. This study is the first controlled evaluation of the intellectual ability of patients with GHRD. We compared the intelligence of 18 patients of school age (mean +/- SD age, 11.5 +/- 2.8 yr), 42 of their relatives (11.5 +/- 2.8 yr), and 28 community controls (10.0 +/- 0.8 yr), using a battery of intelligence tests that have been validated in cross-cultural research, designed to minimize the effects of physical size, motor coordination, and cultural background. Because all patients had the same GHR mutation, for which the carrier state could be determined, this study also investigated whether heterozygosity for mutation of the GHR among unaffected relatives is associated with intelligence. The intellectual ability of the patients with GHRD was not significantly different from that of their relatives (P > 0.05) on the psychometric tests of intelligence and was comparable to that of the community controls on the chronometric tests. Homozygosity or heterozygosity for the mutation in the GHR gene common to Ecuadorian patients was unrelated to intelligence (P > 0.05). These results indicate that the gene defect causing GHRD is not related to intelligence in the Ecuadorian population. They also indicate that GH-induced IGF-I production is not required for normal brain growth in utero or for postnatal intellectual development.

Insulin-like growth factor-I modulation of cerebellar cell populations is developmentally stage-dependent and mediated by specific intracellular pathways

Although development of transgenic animals overexpressing insulin-like growth factor-I has allowed the establishment of a role of this trophic factor in brain growth, detailed knowledge of the action of insulin-like growth factor-I on different brain areas is still lacking. We now provide evidence for a pleiotrophic role of this growth factor on cerebellar development. Insulin-like growth factor-I produced by cerebellar cultures is a survival factor for Purkinje cells and a mitogen/differentiation factor for cerebellar glioblasts. Trophic effects of insulin-like growth factor-I were observed only during specific developmental stages. In addition, insulin-like growth factor-I increased intracellular Ca2+ levels in Purkinje cells and c-Fos in dividing glioblasts. Survival-promoting effects of insulin-like growth factor-I on Purkinje cells required activation of protein kinase C, while glioblast division induced by insulin-like growth factor-I depended on phosphatidylinosytol 3-kinase activation.We conclude that insulin-like growth factor-I is a paracrine/ autocrine pleiotrophic factor for both glia and neurons in the cerebellum. Its effects are mediated by distinct intracellular signals and appear to be specific to the developmental stage of the target cell. Since development of the different cell populations that compose a specific brain territory is not synchronized, the pleiotrophic action of growth factors such as insulin-like growth factor-I may be essential to ontogenetic processes underlying normal brain growth.

VITAMIN B12 STATUS AND PEDIATRIC HIV ENCEPHALOPATHY. 685

Low holotranscobalamin II (holotc II) has been shown to be the earliest marker for subnormal vitamin B12 absorption in AIDS and can have neuropsychiatric sequelae. OBJECTIVES: The main objectives of this pilot study were to measure levels of vitamin B12 and holotc II in sera of pediatric HIV patients (pts) with encephalopathy or CNS dysfunction and compare these to controls with normal brain growth and no neuropsychological abnormalities both with and without HIV infection. METHODS: HIV(-) controls were either born to HIV(+) mothers or were siblings of HIV (+) pts. Laboratory measurement of vitamin B12, (including TC I, II, and III B12) and folate levels was performed by the Hematology and Nutrition Research Laboratory, VAMC, Bronx, NY. RESULTS: No pts were deficient in total vitamin B12. 5 of 8 pts with encephalopathy or CNS dysfunction had low holotc II; the mean +/- s.d. was 39.9 +/- 38.6 pg/ml,(n1 > 50 pg/ml). 4 of 7 HIV(+) pts with normal neurologic function had low holotc II; mean 51.5 +/- 53.4 pg/ml. 3 of 12 HIV(-) pts with normal neurologic function had low holotc II (2 of which were normal on repeat); the mean for HIV(-) pts was 77.6 +/- 51.5 pg/ml. The mean holotc II for encephalopathic children was not significantly different than that of either HIV(+) or (-) controls. The apparent trend towards lower vitamin B12 levels in HIV infected versus non-infected pts did not achieve statistical significance, possibly because of small numbers. No HIV(+) pts were folate deficient. 7 of 12 HIV(-) pts were frankly deficient (<3 ng/ml, n=3) or borderline (3-5 ng/ml, n=4) in folate status. CONCLUSIONS: This pilot study suggests widespread malabsorption of vitamin B12 in our HIV(+) pts, consistent with that previously described in adult AIDS. We were unable to demonstrate an association between vitamin B12 deficiency and HIV encephalopathy specifically. The majority of HIV(-) controls demonstrated borderline or deficient vitamin B12 and/or folate status. More studies of vitamin B12 and folate status in children with HIV infection are indicated.