Aberrant Central Nervous System Research Articles

Maternal Hypoxia Increases the Excitability of Neurons in the Entorhinal Cortex and Dorsal Hippocampus of Rat Offspring.

Prenatal hypoxia is a widespread condition that causes various disturbances in later life, including aberrant central nervous system development, abnormalities in EEG rhythms, and susceptibility to seizures. Hypoxia in rats on the 14th day of embryogenesis (E14) disrupts cortical neuroblast radial migration, mainly affecting the progenitors of cortical glutamatergic neurons but not GABAergic interneurons or hippocampal neurons. Thus, hypoxia at this time point might affect the development of the neocortex to a greater extent than the hippocampus. In the present study, we investigated the long-term effects of hypoxia on the properties of the pyramidal neurons in the hippocampus and entorhinal cortex (EC) in 3-week-old rats subjected to hypoxia on E14. We observed a reduction in the total number of NeuN-positive neurons in EC but not in the CA1 field of the hippocampus, indicating an increased cell loss in EC. However, the principal neuron electrophysiological characteristics were altered in the EC and hippocampus of animals exposed to hypoxia. The whole-cell patch-clamp recordings revealed a similar increase in input resistance in neurons from the hippocampus and EC. However, the resting membrane potential was increased in the EC neurons only. The recordings of field postsynaptic potentials (fPSPs) in the CA1 hippocampal area showed that both the threshold currents inducing fPSPs and population spikes were lower in hypoxic animals compared to age-matched controls. Using the dosed electroshock paradigm, we found that seizure thresholds were lower in the hypoxic group. Thus, the obtained results suggest that maternal hypoxia during the generation of the pyramidal cortical neurons leads to the increased excitability of neuronal circuitries in the brain of young rats. The increased excitability can be attributed to the changes in intrinsic neuronal properties.

Gadd45 in Neuronal Development, Function, and Injury.

The growth arrest and DNA damage-inducible (Gadd) 45 proteins have been associated with numerous cellular mechanisms including cell cycle control, DNA damage sensation and repair, genotoxic stress, neoplasia, and molecular epigenetics. The genes were originally identified in in vitro screens of irradiation- and interleukin-induced transcription and have since been implicated in a host of normal and aberrant central nervous system processes. These include early and postnatal development, injury, cancer, memory, aging, and neurodegenerative and psychiatric disease states. The proteins act through a variety of molecular signaling cascades including the MAPK cascade, cell cycle control mechanisms, histone regulation, and epigenetic DNA demethylation. In this review, we provide a comprehensive discussion of the literature implicating each of the three members of the Gadd45 family in these processes.

Targeting Systemic Innate Immune Cells as a Therapeutic Avenue for Alzheimer Disease.

Alzheimer disease (AD) is the first progressive neurodegenerative disease worldwide, and the disease is characterized by an accumulation of amyloid in the brain and neurovasculature that triggers cognitive decline and neuroinflammation. The innate immune system has a preponderant role in AD. The last decade, scientists focused their efforts on therapies aiming to modulate innate immunity. The latter is of great interest, since they participate to the inflammation and phagocytose the amyloid in the brain and blood vessels. We and others have developed pharmacological approaches to stimulate these cells using various ligands. These include toll-like receptor 4, macrophage colony stimulating factor, and more recently nucleotide-binding oligomerization domain-containing 2 receptors. This review will discuss the great potential to take advantage of the innate immune system to fight naturally against amyloid β accumulation and prevent its detrimental consequence on brain functions and its vascular system. SIGNIFICANCE STATEMENT: The focus on amyloid β removal from the perivascular space rather than targeting CNS plaque formation and clearance represents a new direction with a great potential. Small molecules able to act at the level of peripheral immunity would constitute a novel approach for tackling aberrant central nervous system biology, one of which we believe would have the potential of generating a lot of interest.

C21orf91 Regulates Oligodendroglial Precursor Cell Fate-A Switch in the Glial Lineage?

Neuropathological diseases of the central nervous system (CNS) are frequently associated with impaired differentiation of the oligodendroglial cell lineage and subsequent alterations in white matter structure and dynamics. Down syndrome (DS), or trisomy 21, is the most common genetic cause for cognitive impairments and intellectual disability (ID) and is associated with a reduction in the number of neurons and oligodendrocytes, as well as with hypomyelination and astrogliosis. Recent studies mainly focused on neuronal development in DS and underestimated the role of glial cells as pathogenic players. This also relates to C21ORF91, a protein considered a key modulator of aberrant CNS development in DS. We investigated the role of C21orf91 ortholog in terms of oligodendrogenesis and myelination using database information as well as through cultured primary oligodendroglial precursor cells (OPCs). Upon modulation of C21orf91 gene expression, we found this factor to be important for accurate oligodendroglial differentiation, influencing their capacity to mature and to myelinate axons. Interestingly, C21orf91 overexpression initiates a cell population coexpressing astroglial- and oligodendroglial markers indicating that elevated C21orf91 expression levels induce a gliogenic shift towards the astrocytic lineage reflecting non-equilibrated glial cell populations in DS brains.

Neuroinflammatory contribution of microglia and astrocytes in fetal alcohol spectrum disorders

Ethanol exposure to the fetus during pregnancy can result in fetal alcohol spectrum disorders (FASD). These disorders vary in severity, can affect multiple organ systems, and can lead to lifelong disabilities. Damage to the central nervous system (CNS) is common in FASD, and can result in altered behavior and cognition. The incidence of FASD is alarmingly high, resulting in significant personal and societal costs. There are no cures for FASD. Alcohol can directly alter the function of neurons in the developing CNS. In addition, ethanol can alter the function of CNS glial cells including microglia and astrocytes which normally maintain homeostasis in the CNS. These glial cells can function as resident immune cells in the CNS to protect against pathogens and other insults. However, activation of glia can also damage CNS cells and lead to aberrant CNS function. Ethanol exposure to the developing brain can result in the activation of glia and neuroinflammation, which may contribute to the pathology associated with FASD. This suggests that anti-inflammatory agents may be effective in the treatment of FASD.

Central Pain in Patient with Cancer (GP789)

• Understand what central pain is and why it is important to recognize it.• Review the results from a small survey study designed to assess the prevalence of central pain in an advanced cancer population. Despite the current efforts to manage cancer pain with opioids, a significant number of cancer patients still experience pain. One reason may be that such patients have pain that comes from problems with the brain’s processing of pain rather than nociception, neuropathy, or inflammation. Pain related to aberrant central nervous system processing is called “central pain.” Central pain is the key pathway in many chronic pain syndromes (e.g. fibromyalgia). To demonstrate that central pain is common among cancer patients receiving palliative care. To demonstrate that cancer patients with greater severity of centralization also have elevated levels of other symptoms as well. This was a small observational study of data routinely gathered during visits to the Supportive Oncology Clinic at the University of Michigan. Patients were administered the 2011 Fibromyalgia Survey (2011 FMS) which is used to diagnose central pain and grade its severity. Patients also received the ESAS. Patients were classified as having central pain (y/n) based on 2016 American College of Rheumatology criteria for fibromyalgia and further grouped into terciles based on their 2011 FM Score. Among 55 subjects, 13 (24%) met established criteria for central pain. Subjects with central pain had the same number of symptoms and severity of pain as those without central pain, but higher severity (0-10) of anxiety (5.4 vs. 3.6), cognitive difficulties (3.6 vs. 2.7), memory difficulties (4.5 vs. 3.0), and depressed mood (4.7 vs. 3.6). Higher terciles of central pain associated with constipation (coef. 0.182 P=0.040), fatigue (coef. 1.368, P=0.010), and dyspnea (coef. 0.243, P=0.010). There is evidence of central pain among patients with cancer seen in Supportive Oncology

Functional Magnetic Resonance Imaging Detects Between-Group Differences in Neural Activation Among Men with Delayed Orgasm Compared with Normal Controls: Preliminary Report

BackgroundMechanisms underlying delayed orgasm (DO) are poorly understood; however, known effects of psychotropic medications on sexual function provides a rationale for aberrant central nervous system signaling as a cause. AimTo compare brain activation between men with normal orgasm and those with lifelong DO during sexual stimulation using brain fMRI algorithms. Methods3 subjects with self-reported life-long DO and 6 normal controls were included in this study. The International Index of Erectile Function, Male Sexual Health Questionnaire, and self-reported time to orgasm were used to assess sexual function. Subjects underwent a 3-T fMRI study while viewing 3 video clips: a neutral control (NC), a positive emotional control (EC), and a sexual condition (SC). Each video sequence was repeated 5 times, with 50-second clips presented in a randomized fashion. fMRI data were analyzed in a block design manner to determine areas of differential brain activation between groups. The Allen Brain Atlas of gene expression in the human brain was used to identify signaling pathways in the areas of differential fMRI activation between the DO and control groups. OutcomesThe primary outcome was differential activation of fMRI neural activation between groups. ResultsAnalysis of differential activation in the SC compared with the NC and EC revealed increased activation in the right frontal operculum (P = .003), right prefrontal gyrus (P = .003), and inferior occipital gyrus (P = .003). Increased activation in the right fusiform gyrus of the occipital lobe and the right hippocampus (P = .0004) was seen in the DO group compared with controls. Using the Allen Atlas of Human Brain Expression, we identified corresponding neurotransmitter receptors to this region, including adenosine receptors, muscarinic and nicotinic cholinergic receptors, cannabinoid receptors, and dopamine receptors, among others. Clinical ImplicationsLifelong DO in men may be due to abnormal neurotransmitter signaling leading to poor progression of arousal due to aberrant processing of sexual cues. Identification of neurotransmitter pathways by fMRI will aid the development of pharmacotherapeutic agents. Strengths & LimitationsStrengths of this study include the novel application of functional neuroimaging to investigate the pathogenesis of DO. Limitations include the small sample size, making this study exploratory in nature. ConclusionThis study revealed differences in brain activation on visualization of sexual stimuli in men with a history of DO compared with controls. Identified regions are rich in numerous neurotransmitter receptor subtypes and may be amenable to pharmacologic targeting to identify novel therapies for these men.Flannigan R, Heier L, Voss H, et al. Functional Magnetic Resonance Imaging Detects Between-Group Differences in Neural Activation Among Men with Delayed Orgasm Compared with Normal Controls: Preliminary Report. J Sex Med 2019:16;1246–1254.

Is fibromyalgia a cause of arthroscopic subacromial decompression failure?

Isolated arthroscopic subacromial decompression (IASD) is a widely used surgical procedure with high success rates. However, up to 25% of patients experience residual pain. It is unclear whether aberrant central nervous system processing of pain as described in fibromyalgia (FM) could have a detrimental effect on outcomes.To test this hypothesis, the authors conducted a retrospective case–control study of patients undergoing IASD. Material and methodsBetween 2008 and 2015, 26 patients with preoperative diagnosis of fibromyalgia and an IASD procedure were identified. Six patients were lost to follow-up. Each fibromyalgia patient was matched with one control patient (n=20) recruited from the remainder with IASD. Outcomes were assessed by DASH score (Disability Arm Shoulder and Hand), Constant (CS), relative Constant score (rCS) and Visual Analogue Scale (VAS). Patient satisfaction was determined with a single 2-level question. Failure of the IASD was defined as persistent pain (VAS>3) at last follow-up. ResultsThe average age of the sample was FM/Control group 51/48, with a mean follow-up of 36/42 months respectively. Both groups exhibited significant clinical improvement in the pain VAS, DASH and rCS at final follow-up (p<001) compared with the preoperative scores.Mean postoperative scores FM/Control group were: Constant 63.5/74 (p=.07), rCS 82/88 (p=18), DASH 38.9/20.7 (p=009), VAS 3.8/2.8 (p=2). Eighty-five percent of patients in the control group were satisfied with the surgery compared with 55% in the FM group (p=03). Failure of the procedure was 60% in the FM group, and 30% in the control group (p=.056). ConclusionsFibromyalgia can be considered a prognostic factor of a poor postoperative outcome after an IASD. However the clinical improvement experienced by these patients over their preoperative situation leads us to recommend their surgical treatment when indicated.

¿Es la fibromialgia causa de fracaso de una descompresión subacromial artroscópica?

Isolated arthroscopic subacromial decompression (IASD) is a widely used surgical procedure with high success rates. However, up to 25% of patients experience residual pain. It is unclear whether aberrant central nervous system processing of pain as described in fibromyalgia (FM) could have a detrimental effect on outcomes.To test this hypothesis, the authors conducted a retrospective case- control study of patients undergoing IASD. Material and methodsBetween 2008 and 2015, 26 patients with preoperative diagnosis of fibromyalgia and an IASD procedure were identified. Six patients were lost to follow-up. Each fibromyalgia patient was matched with one control patient (n=20) recruited from the remainder with IASD. Outcomes were assessed by DASH score (Disability Arm Shoulder and Hand), Constant (CS), relative Constant score (rCS) and Visual Analogue Scale (VAS). Patient satisfaction was determined with a single 2-level question. Failure of the IASD was defined as persistent pain (VAS>3) at last follow-up. ResultsThe average age of the sample was FM/Control group 51/48, with a mean follow-up of 36/42 months respectively. Both groups exhibited significant clinical improvement in the pain VAS, DASH and rCS at final follow-up (P<.001) compared with the preoperative scores.Mean postoperative scores FM/Control group were: Constant 63.5/74 (P=.07), rCS 82/88 (P=.18), DASH 38.9/20.7 (P=.009), VAS 3.8/2.8 (P=.2). Eighty-five percent of patients in the control group were satisfied with the surgery compared with 55% in the FM group (P=.03). Failure of the procedure was 60% in the FM group, and 30% in the control group (P=.056). ConclusionsFibromyalgia can be considered a prognostic factor of a poor postoperative outcome after an IASD. However the clinical improvement experienced by these patients over their preoperative situation leads us to recommend their surgical treatment when indicated.

Sensory sensitivity and symptom severity represent unique dimensions of chronic pain: a MAPP Research Network study.

Chronic overlapping pain conditions (COPCs) are characterized by aberrant central nervous system processing of pain. This "centralized pain" phenotype has been described using a large and diverse set of symptom domains, including the spatial distribution of pain, pain intensity, fatigue, mood imbalances, cognitive dysfunction, altered somatic sensations, and hypersensitivity to external stimuli. Here, we used 3 cohorts, including patients with urologic chronic pelvic pain syndrome, a mixed pain cohort with other COPCs, and healthy individuals (total n = 1039) from the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network to explore the factor structure of symptoms of centralized pain. Using exploratory and confirmatory factor analysis, we identified 2 general factors in all 3 cohorts, one characterized by a broad increased sensitivity to internal somatic sensations,environmental stimuli, and diffuse pain, termed Generalized Sensory Sensitivity, and one characterized by constitutional symptoms-Sleep, Pain, Affect, Cognition, Energy (SPACE). Longitudinal analyses in the urologic chronic pelvic pain syndrome cohort found the same 2-factor structure at month 6 and 1 year, suggesting that the 2-factor structure is reproducible over time. In secondary analyses, we found that Generalized Sensory Sensitivity particularly is associated with the presence of comorbid COPCs, whereas SPACE shows modest associations with measures of disability and urinary symptoms. These factors may represent an important and distinct continuum of symptoms that are indicative of the centralized pain phenotype at high levels. Future research of COPCs should accommodate the measurement of each factor.

Preventive effects of dextromethorphan on methylmercury-induced glutamate dyshomeostasis and oxidative damage in rat cerebral cortex.

Methylmercury (MeHg) is a well-known environmental pollutant leading to neurotoxicant associated with aberrant central nervous system (CNS) functions, but its toxic mechanisms have not yet been fully recognized. In the present study, we tested the hypothesis that MeHg induces neuronal injury via glutamate (Glu) dyshomeostasis and oxidative damage mechanisms and that these effects are attenuated by dextromethorphan (DM), a low-affinity and noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist. Seventy-two rats were randomly divided into four groups of 18 animals in each group: control group, MeHg-treated group (4 and 12μmol/kg), and DM-pretreated group. After the 4-week treatment, we observed that the administration of MeHg at a dose of 12μmol/kg significantly increased in total mercury (Hg) levels, disrupted Glu metabolism, overexcited NMDARs, and led to intracellular calcium overload in the cerebral cortex. We also found that MeHg reduced nonenzymatic and enzymatic antioxidants, enhanced neurocyte apoptosis, induced reactive oxygen species (ROS), and caused lipid, protein, and DNA peroxidative damage in the cerebral cortex. Moreover, glutamate/aspartate transporter (GLAST) and glutamate transporter-1 (GLT-1) appeared to be inhibited by MeHg exposure. These alterations were significantly prevented by the pretreatment with DM at a dose of 13.5μmol/kg. In conclusion, these findings strongly implicate that DM has potential to protect the brain from Glu dyshomeostasis and oxidative damage resulting from MeHg-induced neurotoxicity in rat.

Transcript Diversification in the Nervous System: A to I RNA Editing in CNS Function and Disease Development

RNA editing by adenosine deaminases that act on RNA converts adenosines to inosines in coding and non-coding regions of mRNAs. Inosines are interpreted as guanosines and hence, this type of editing can change codons, alter splice patterns, or influence the fate of an RNA. A to I editing is most abundant in the central nervous system (CNS). Here, targets for this type of nucleotide modification frequently encode receptors and channels. In many cases, the editing-induced amino acid exchanges alter the properties of the receptors and channels. Consistently, changes in editing patterns are frequently found associated with diseases of the CNS. In this review we describe the mechanisms of RNA editing and focus on target mRNAs of editing that are functionally relevant to normal and aberrant CNS activity.

Protective effect of a novel peptide against methylmercury-induced toxicity in rat primary astrocytes

Methylmercury (MeHg) is an environmental neurotoxicant associated with aberrant central nervous system (CNS) functions. In this study, we examined the protective effect of a novel anti-inflammatory and cytoprotective nonapeptide, termed IIIM1, against MeHg-induced toxicity in cultured rat neonatal primary astrocytes. Astrocytes were pretreated for 66h with 5μg/ml IIIM1 (4.95μM) followed by 6h exposure to MeHg (5μM). MeHg significantly increased F2-isoprostane generation, a lipid peroxidation biomarker of oxidative injury and this effect was significantly reduced upon pre-treatment with IIIM1. The MeHg-induced increase in levels of prostaglandin E2 (PGE2), biomarkers of inflammatory responses, was also decreased in the peptide-treated cells. Mass spectrometry analysis revealed no chemical or binding interaction between MeHg and IIIM1, indicating that intracellular cytoprotective mechanism of action accounts for the neuroprotection rather than direct intracellular neutralization of the neurotoxicant with the peptide. These findings point to therapeutic potential for IIIM1 in a plethora of conditions associated with reactive oxygen species (ROS) generation. The implication of these findings may prove beneficial in designing new treatment modalities that efficiently suppress neurotoxicity, triggered not only by MeHg, but also by other metals and environmental agents, as well as chronic disease conditions that inherently increase reactive radical production and inflammatory signaling.

Selective, quantitative measurement of releasable synaptic zinc in human autopsy hippocampal brain tissue from Alzheimer's disease patients

Aberrant central nervous system zinc homeostasis has been reported in Alzheimer's disease (AD). However, there are conflicting reports describing zinc concentration either increased or decreased in the brain of AD patients. Such discrepancies may be due to differences in the brain area examined, zinc detection method, and/or tissue composition. Furthermore, detection and measurement of the releasable zinc pool in autopsy tissue is difficult and usually unreliable. Obtaining an adequate assessment of this releasable zinc pool is of particular significance in AD research in that zinc can coordinate with and stabilize toxic amyloid beta oligomers, which are believed to play a key role in AD neuropathology. In addition, zinc released into the synaptic cleft can interact with the postsynaptic neurons causing altered signaling and synaptic dysfunction, which is a well established event in AD. The method presented here combines two approaches, biochemical fractionation and atomic absorption spectrophotometry, to allow, in addition to extracellular zinc concentration, the reliable and quantitative measurement of zinc specifically localized in synaptic vesicles, which contain the majority of the neuronal releasable zinc. Using this methodology, we found that synaptic vesicle zinc concentrations were increased in AD hippocampi compared to age-matched controls and that this increase in releasable zinc matched increased concentration of zinc in the extracellular space.

Alterations in pain responses in treated and untreated patients with restless legs syndrome: Associations with sleep disruption

Objective There has been recent interest in characterizing potential abnormalities of pain processing in patients with sleep disorders such as Restless Legs Syndrome (RLS). The aim of this study was to evaluate psychophysical responses to noxious heat and pressure stimuli in both treated and untreated RLS patients, compared to matched controls. Methods This study is a cross-sectional group comparison of RLS patients with matched controls. A total of 31 patients (15 treated, 16 untreated) with a confirmed diagnosis of RLS were compared to 18 controls with no history of RLS or related sleep disorders. Results RLS patients (both treated and untreated) demonstrated reduced pain thresholds and reported greater clinical pain relative to controls. Moreover, RLS patients demonstrated enhanced temporal summation of heat pain ( p < .05), which may reflect aberrant central nervous system facilitation of pain transmission. Both treated and untreated RLS patients reported disrupted sleep relative to controls, and mediation analyses suggested that the reduced pain thresholds in RLS were attributable to sleep disturbance. However, the effect of RLS on the magnitude of temporal summation of heat pain was independent of sleep disturbance. Conclusions These findings suggest that central nervous system pain processing may be amplified in RLS, perhaps partially as a consequence of sleep disruption. RLS patients, even those whose symptoms are managed pharmacologically, may be at elevated long-term risk for the development or maintenance of persistent pain conditions. Further studies in larger samples could help to improve the prospects for pain management in RLS patients.

Possibilities and limitations of pharmacological fMRI

Functional magnetic resonance imaging (fMRI) techniques allow to investigate non-invasively and in-vivo the function of the central nervous system (CNS). They have the potential to provide sensitive and specific biomarkers about aberrant CNS functions. Combing drug administration and fMRI, which is termed as pharmacological fMRI (phFMRI), is particularly suited to investigate the CNS effects of pharmacological agents, for example on pain processing. In this talk phFMRI studies are presented that have already used this technique to study the effects of analgesic compounds.

CREB Binding and Activity in Brain: Regional Specificity and Induction by Electroconvulsive Seizure

The transcription factor cyclic adenosine monophosphate response element binding protein (CREB) orchestrates diverse neurobiological processes including cell differentiation, survival, and plasticity. Alterations in CREB-mediated transcription have been implicated in numerous central nervous system (CNS) disorders including depression, anxiety, addiction, and cognitive decline. However, it remains unclear how CREB contributes to normal and aberrant CNS function, as the identity of CREB-regulated genes in brain and the regional and temporal dynamics of CREB function remain largely undetermined. We combined microarray and chromatin immunoprecipitation technology to analyze CREB-DNA interactions in brain. We compared the occupancy and activity of CREB at gene promoters in rat frontal cortex, hippocampus, and striatum before and after a rodent model of electroconvulsive therapy. Our analysis identified >860 CREB binding sites in rat brain. We identified multiple genomic loci enriched with CREB binding sites and find that CREB-occupied transcripts interact extensively to promote cell proliferation, plasticity, and resiliency. We discovered regional differences in CREB occupancy and activity that explain, in part, the diverse biological and behavioral outputs of CREB activity in frontal cortex, hippocampus, and striatum. Electroconvulsive seizure rapidly increased CREB occupancy and/or phosphorylation at select promoters, demonstrating that both events contribute to the temporal regulation of the CREB transcriptome. Our data provide a mechanistic basis for CREB's ability to integrate regional and temporal cues to orchestrate state-specific patterns of transcription in the brain, indicate that CREB is an important mediator of the biological responses to electroconvulsive seizure, and provide global mechanistic insights into CREB's role in psychiatric and cognitive function.

In vivo inactivation of pRb , p107 and p130 in murine neuroprogenitor cells leads to major CNS developmental defects and high seizure rates

Nestin-positive cells were targeted for pRb, p107 and p130 (pRb f) inactivation by expression of T 121, a truncated SV40 large T antigen that selectively binds to and inactivates pRb f. Cre expression was initiated under GFAP control, resulting in T 121 expression restricted to neuroprogenitor cells beginning at embryonic day 11.5 (E11.5). Bi-transgenic embryos showed aberrant central nervous system (CNS) cell proliferation and apoptosis by E13.5. Defects in cortical development were evident with primary effects resulting in depletion of neural progenitors and aberrant cellular migration. Consequently, juvenile and adult brain morphology was reproducibly abnormal, including disorganization of neocortical, hippocampal and cerebellar regions. These aberrations resulted in behavioral phenotypes, including ataxia and seizures. The data indicate that inactivation of pRb f in radial glial cells, a population of neuroprogenitor cells, leads to specific disruptions in CNS patterning. The neuroprogenitor-restricted transgene expression provides a model in which to explore both developmental mechanisms and functional neurological outcomes.

A targeted gain of function screen in the embryonic CNS of Drosophila

In order to identify genes involved in the development of the central nervous system (CNS) we have undertaken a gain of function screen in the embryonic CNS of Drosophila. Transposable P-elements and the UAS/GAL4 system were used to initiate transcription of genes in a pan-neural pattern using scaGAL4. Over 4100 individual P-element insertion lines were screened with monoclonal antibodies BP102 and 1D4 to visualize axon pathways. Twenty-five P-element insertions corresponding to 18 genes resulted in aberrant CNS axon pathfinding when misexpressed with scaGAL4. Genes involved in axon guidance, embryonic patterning, and cell cycle regulation were isolated. In addition, we identified several zinc finger transcription factors not previously implicated in axon guidance or CNS development. This group includes Squeeze, Kruppel homolog-1, Hepatocyte nuclear factor 4, and two uncharacterized genes, CG11966 and CG9650. Calnexin99A, a putative molecular chaperone, was isolated as well.

Developmental Aspects of Blood–Brain Barrier (BBB) and Rat Brain Endothelial (RBE4) Cells as in vitro Model for Studies on Chlorpyrifos Transport

The mammalian central nervous system (CNS) is characterized by the blood–brain barrier (BBB), a restrictive barrier endowed with the maintenance of homeostatic control of an optimal milieu within the brain. Whereas in tissues other than the CNS, concentrations of various metabolites (amino acids, K +) can undergo frequent fluctuations, the CNS must keep rigorous control over the extracellular cerebral fluid composition, preventing the mirroring of transient fluctuations in blood, because abrupt changes in these metabolites can translate to aberrant CNS function. The BBB is a specialized structure accomplished by individual endothelial cells that are continuously linked by tight junctions. This brief review will address pertinent issues to development of the BBB. Particular emphasis will be directed at the role of astrocytes in the induction and maintenance of the restrictive properties of this barrier, and the utility of in vitro culture models in surveying transport kinetics, exemplified by recent studies with the pesticide, chlorpyrifos.