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Background: It has been previously shown that blockade of the type 1 insulin-like growth factor receptor (IGF1R) signaling combined with mTOR inhibition decreased neuroblastoma proliferation in vitro. MYC-N inactivation occurs through phosphorylation by downstream elements of the IGF1R signaling pathway. It was hypothesized that inhibition of IGF1R signaling would increase the inactivation of MYC-N., Materials and Methods: BE-2(c) and IMR-32 neuroblastoma cell lines were treated with varying concentrations of alphaIR3, rapamycin and temsirolimus either alone or in combination and the expression of MYC-N and phosphorylated MYC-N proteins were evaluated by Western blotting. The number of apoptotic cells was evaluated through cleaved caspase-3 expression., Results: IGF1R signaling blockade in combination with mTOR inhibition decreased MYC-N protein expression, increased MYC-N phosphorylation and significantly increased cleaved caspase-3 expression in treated cells., Conclusion: The combination of rapamycin or temsirolimus with alphaIR3 decreases MYC-N expression, increases MYC-N phosphorylation and induces apoptosis in vitro which may have clinical relevance to children with neuroblastoma.

Background: Protein kinase C (PKC) is a family of isoenzymes that regulate a variety of functions in the central nervous system including neurotransmitter release, ion channel activity, and cell differentiation. Growing evidence suggests that specific isoforms of PKC influence a variety of behavioral, biochemical, and physiological effects of ethanol in mammals. The purpose of this study was to determine whether acute ethanol exposure alters phosphorylation of conventional PKC isoforms at a threonine 674 (p-cPKC) site in the hydrophobic domain of the kinase, which is required for its catalytic activity., Methods: Male rats were administered a dose range of ethanol (0, 0.5, 1, or 2 g/kg, intragastric) and brain tissue was removed 10 minutes later for evaluation of changes in p-cPKC expression using immunohistochemistry and Western blot methods., Results: Immunohistochemical data show that the highest dose of ethanol (2 g/kg) rapidly increases p-cPKC immunoreactivity specifically in the nucleus accumbens (core and shell), lateral septum, and hippocampus (CA3 and dentate gyrus). Western blot analysis further showed that ethanol (2 g/kg) increased p-cPKC expression in the P2 membrane fraction of tissue from the nucleus accumbens and hippocampus. Although p-cPKC was expressed in numerous other brain regions, including the caudate nucleus, amygdala, and cortex, no changes were observed in response to acute ethanol. Total PKCgamma immunoreactivity was surveyed throughout the brain and showed no change following acute ethanol injection., Conclusions: These results suggest that ethanol rapidly promotes phosphorylation of cPKC in limbic brain regions, which may underlie effects of acute ethanol on the nervous system and behavior.

Expression patterns of 5-HT(2A), 5-HT(2B) and 5-HT(2C) receptors during mouse embryogenesis were investigated using highly specific monoclonal antibodies. Differential and overlapping spatio-temporal patterns of 5-HT(2A), 5-HT(2B) and 5-HT(2C) receptor immunoreactivity were observed during active phases of morphogenesis of a variety of embryonic tissues, including neuroepithelia of brain and spinal cord, notochord, somites, cranial neural crest, craniofacial mesenchyme and epithelia, heart myocardium and endocardial cushions, tooth germs, whisker follicles, cartilage and striated muscle. The functional significance of these receptors was tested by exposing headfold stage mouse embryos to different subtype-selective 5-HT(2) receptor antagonists for 2 days in whole embryo culture. The most potent was the pan 5-HT(2) receptor antagonist ritanserin, which has high affinity for the 5-HT(2B) receptor. Ritanserin caused 100% malformed embryos at a dose of 1 microM. The 5-HT(2A/2C) receptor antagonist mianserin also caused a significant number of malformed embryos, but only when used at a 10 fold higher dose (10 microM). Ketanserin, which primarily targets 5-HT(2A) receptors, did not cause a significant number of malformed embryos at any dose tested. Together with previous evidence that 5-HT acts as an important morphoregulatory signal during mouse embryogenesis, present evidence for the early and continued expression of functional 5-HT(2) receptors throughout gestation raises the possibility that psychotropic drugs taken during pregnancy could interfere with developmental actions of 5-HT during prenatal development of neural and non-neural tissues.

The GLUT4 glucose transporter is primarily expressed in skeletal muscle, heart and adipose tissue, where its expression is postnatal, coincident with the acquisition of insulin-regulated glucose transport. In muscle, contraction also regulates GLUT4 activity in the postnatal animal. Here we demonstrate that GLUT4 is expressed in the developing mouse embryo with specific tissue and spatiotemporal patterns. From embryonic day 9 (E9; E1 = day of copulation plug) to postnatal day 70 (P70), mice were analyzed for GLUT4 mRNA and protein expression by in situ hybridization, immunohistochemistry and immunoblot. Specificity was confirmed with sense riboprobe hybridization and peptide competition, respectively. At E9, GLUT4 was detected in the cranial neural folds in the outer (mantle) layer of the neuroepithelium. At E10, expression was present throughout the developing heart and was prominent in the endocardial cushions through E12. At E10-12, GLUT4 was also prominent in craniofacial mesenchyme. GLUT4 expression in cartilage and bone was evident at E12 and was maintained throughout early postnatal life. GLUT4 was apparent throughout embryonic development in the ventricular epithelium, choroid plexus and in the developing cerebellum. At birth, cardiac expression was reduced and GLUT4 was most evident in cartilage, bone and specific brain regions. In the latter, GLUT4 expression was most evident in the cerebellum, specifically in the external granular layer through P7 and in the internal granular layer thereafter. Maximal GLUT4 protein levels in the cerebellum were measured between P14 and P21 and were reduced in the adult brain. These findings suggest that GLUT4-mediated glucose transport may play important roles during development of the brain and nonneuronal tissues in the mouse embryo., (Copyright 2000 S. Karger AG, Basel.)

Background: Biogenic amine neurons are involved in a number of mental diseases including addiction and alcohol dependence. Because chronic ethanol is known to cause supersensitivity to NMDA excitotoxicity in cortical neurons, this study sought to determine the effect of ethanol treatment on biogenic amine neurons., Methods: To determine if ethanol exposure alters the vitality of biogenic amine neurons, cultures were prepared from E14 rat brain. After 24 hr in culture, cells were divided into control or ethanol (100 mM) treatment groups, cultured an additional 48 hr, and then half of them exposed to NMDA for 25 min. The NMDA was then removed and cells cultured in fresh media for an additional 24 hr to allow for excitotoxic delayed neuronal death. Cultures were then stained with antibodies to 5-hydroxytryptamine or tyrosine hydroxylase to identify serotonin and dopamine neurons, respectively. Cultures were analyzed for cell number and neuronal morphology., Results: Ethanol treatment alone had no effect on biogenic amine cell number, soma area, number of neurites, or terminal segments, although the field area of dopamine neurons was decreased. Treatment with 30 microM NMDA had no effect on controls, but significantly decreased dopamine neurons in ethanol-treated cultures as well as reduced soma area, field area, number of neurites and number of terminal segments. Treatment with higher concentrations of NMDA reduced dopamine and serotonin neurons in both controls and ethanol-treated groups, and ethanol treatment significantly enhanced NMDA excitotoxic effects. Treatment with Brain Derived Neurotrophic Factor (BDNF) prevented ethanol sensitization to NMDA excitotoxicity., Conclusions: These studies suggest that ethanol treatment sensitizes biogenic amine neurons to excitotoxic insults. Ethanol sensitization of biogenic amine neurons to insults could contribute to the development of mental disease.

Interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) are cytokines with pleiotropic effects in the central nervous system (CNS), including an emerging role in neurodevelopment. This study measured the effects of cytokines on the survival of tyrosine hydroxylase (TH) immunoreactive dopamine neurons from the substantia nigra (SN), and 5-hydroxytryptamine (5-HT) immunoreactive serotonin neurons from the rostral raphe (RR), using cultures from embryonic day 14 (E14) rat brain. IL-1beta, IL-6, and TNF-alpha were added to cell cultures at 1, 10 and 100 U/ml. After 3 days in vitro, TH and 5-HT neurons were counted. The survival of 5-HT neurons was significantly reduced by 20-30% at 10 U/ml of IL-6. IL-1beta and TNF-alpha at doses of 1 and 10 U/ml appeared to have a similar effect on the survival of these neurons, but this effect was not statistically significant. Comparable non-significant reductions of survival also occurred for TH neurons at the lower doses of IL-6 and TNF-alpha. In separate experiments, SN and RR cultures were exposed to the cytokines at a higher dose (1000 U/ml), causing a significant 30-40% decrease in the survival of TH neurons, but little or no change in 5-HT neuronal survival. Taken together, these results show that IL-1beta, IL-6, and TNF-alpha can affect developing monoamine neurons at physiologically relevant concentrations, and that high doses differentially inhibit the survival of TH and 5-HT neurons after short exposures.

Three lines of transgenic (Tg) mice carrying a fusion gene linking the mouse metallothionein-I promoter to a cDNA encoding human insulin-like growth factor binding protein-1 (hIGFBP-1) were found to express the transgene in brain. As judged by comparing Tg brain weights to those of non-transgenic littermates, adult hemizygotic Tg mice of each line exhibited brain growth retardation (16.2%, 14.4% and 8.1% reductions in weight, respectively in each line). In two lines, total brain DNA and protein content were decreased. Further analysis indicated that the brain growth retardation was manifested in the second week of postnatal life. Given that the insulin-like growth factors (IGFs) stimulate cell proliferation and/or survival in neural cultures and that hIGFBP-1, when present in a molar excess, inhibits IGF interactions with their cell surface receptors, the brain growth retardation in hIGFBP-1 Tg mice likely results from hIGFBP-1 inhibition of IGF-stimulated growth-promoting actions. These hIGFBP-1 Tg mice should prove useful in defining IGF actions during postnatal brain maturation.

Expression of the c-fyn proto-oncogene was analysed in the developing and adult rat brain by subcellular fractionation and immunocytochemistry using polyclonal antibodies specific for its protein product (p59fyn). Immunoperoxidase staining revealed widespread localization of p59fyn in developing axonal tracts throughout the fetal (E18) rat brain. fyn immunoreactivity was not observed in most axon-rich regions of the adult brain, but continued to be expressed at elevated levels in the adult olfactory and vomeronasal systems. At other sites in the adult rat brain, fyn immunoreactivity was restricted to cell bodies of neuronal subpopulations, especially those in brain stem and hypothalamic nuclei, and to subpopulations of glial cells along axonal tracts in the medulla, optic nerve and white matter of the spinal cord. In the peripheral nervous system, fyn staining was also prominent in Schwann cells. Subcellular fractionation of fetal and adult rat brain confirmed the immunocytochemical localization, demonstrating an enrichment of p59fyn in membranes from a fetal brain fraction containing nerve growth cones, and lower levels in adult brain where there was only a small enrichment in synaptosomal membranes. The developmental regulation of p59fyn suggests that the fyn tyrosine kinase may serve separate cellular roles in axonal growth and specialized functions of mature neurons and glia.

Rhombencephala from rat embryos were processed as whole-mounts for immunocytochemical detection of monoaminergic cell populations, using antibodies to tyrosine hydroxylase (TH) and serotonin (5-HT). Specific advantages of the whole-mount technique over the classical serial-section method were that even isolated immunoreactive (IR) cells could be detected easily, and three-dimensional relationships could be ascertained without the need for serial reconstruction. Embryos between embryonic days (E) 12 and 16 (the day following nocturnal mating being considered as E1) were used in this study. Both TH and 5-HT immunoreactivities were already detectable at E12, even in the smallest embryos (crown-rump length: 6 mm), but there was a striking difference in the number and regional distribution of these two types of IR cells. TH was expressed in several cell groups located in the rostral rhombencephalon (the presumed anlage of the A4-7 complex) as well as in the caudal rhombencephalon (the presumed anlagen of groups A1-2 and C1-3), whereas 5-HT was expressed in very few cells located near the rostral border of the rhombencephalon (presumed anlage of the B4-9 complex). Although the three-dimensional distribution of the TH-IR cell groups underwent some modifications during the period studied, its general pattern remained relatively stable after E12. This contrasted with the sequential appearance of the 5-HT-IR cell groups and their spatial transformations during this period. Using the rhombencephalic isthmus as a landmark, we found that conspicuous 5-HT-IR fibre bundles penetrated into the mesencephalon from E13 onwards, but that the 5-HT IR cell bodies were exclusively located caudal to the borderline between the mesencephalon and the rhombencephalon (the rhombencephalic isthmus). We therefore suggest the term "rostral rhombencephalic raphe nuclei" for the rostral 5-HT cell groups instead of "mesencephalic raphe nuclei," which is a misnomer. Close spatial association between TH and 5-HT-IR elements was observed mainly in the caudal rhombencephalon, where 5-HT-IR fibres coursed through an area containing numerous TH-IR cell bodies (the presumed anlagen of groups A1-2 and C1-3).

A simple method is described for the production of glial cell cultures from specific regions of the day 13-15 embryonic rat brainstem and midbrain based on differential cell attachment to a relatively nonadhesive substrate, which inhibits the growth of neurons. Regional differences in the ability of specific populations of brainstem and midbrain cells to attach and spread on the substrate suggest that embryonic glial populations may differ in their cell surface properties even when they derive from the same general area of the developing brain. Based on observations of the spatiotemporal distribution of radial-like glial cells and astrocytes with time in vitro, we suggest that this culture system may prove useful for investigation of the radial glial lineage.