bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organization and expression of the human myelin basic protein gene
Authors: Kamholz J. , Toffenetti J. , Lazzarini R. A. 
Published: January 2005

AbstractThe human brain contains four isoforms of myelin basic protein (MBP), previously identified by cDNA cloning. We have now isolated and characterized genomic clones encoding the human MBP gene. The gene is 45 kb in extent and consists of seven exons. Alternative splicing of the primary MBP transcript can account for all four human MBP isoforms. The intron‐exon boundaries of the gene have also been determined, and all conform to the known consensus splice sequences. These sequences, however, do not explain the alternative splicing pattern found in human brain.Transcription of the human MBP gene begins at a single site within the MBP promoter, and all four MBP isoforms are transcribed from this same site. The promotor region does not contain any known sequence elements, but does have a 12‐bp sequence also found in the JC virus 98‐bp tandem repeat. A relative gradient of MBP transcription is found from caudal to rostral within the developing human brain, which parallels the known sequence of myelination found in these areas. RNase protection of brain RNA demonstrates more of the 21.5‐kD and 20.5‐kD MBP mRNAs in neonatal brain than in the adult frontal cortex, which suggests that alternative splicing of the primary MBP transcript is also regulated temporally during myelin development. These data show that regulation of myelination is complex, involving regional cellular interactions and trans activation of transcription, as well as modulation of alternative splicing. Comparison of the human and mouse data also suggests that alternative splicing plays an important role in myelin biogenesis.
Basic fibroblast growth factor and epidermal growth factor exert differential trophic effects on CNS neurons
Authors: Morrison R. S. , Keating R. F. , Moskal J. R. 
Published: January 2005

AbstractEpidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) are potent mitogenic proteins capable of inducing cell division in a wide variety of cell types. In addition to their mitogenic properties, both proteins have recently been shown to enhance survival and process outgrowth from neurons of central nervous system origin. The full spectrum of neuronal subtypes responding to these factors has not been elucidated. In the present study, EGF was found to enhance survival and process outgrowth of primary cultures of cerebellar neurons of neonatal rat brain. This effect was dose‐dependent and was observed with EGF concentrations as low as 100 pg/ml. In marked contrast, bFGF was ineffective in enhancing survival or neurite elongation from cerebellar neurons when tested in the range of 0.1 to 10.0 ng/ml. However, within this concentration range, bFGF did prove effective in stimulating an increase in [3H]thymidine incorporation into primary cultures of cerebellar astrocytes, demonstrating that bFGF was active and that cells in the cerebellum do respond to bFGF. These results suggest that EGF or an EGF‐like peptide may act as a neurite elongation and maintenance factor for cerebellar neurons. EGF has now been shown to support striatal, cortical, and cerebellar neurons, suggesting that this factor may have trophic activity throughout the central nervous system. bFGF, in contrast, appears to exert its effects on limited populations of neurons.
Distribution of the mineralocorticoid and the glucocorticoid receptor mRNAs in the rat hippocampus
Authors: Van Eekelen J. A. M. , Jiang W. , De Kloet E. R. , Bohn M. C. 
Published: January 2005

AbstractThe cellular localization of mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) gene expression in the rat hippocampus was studied by in situ hybridization using 35S‐labeled RNA‐probes, complementary to either 513 bases of the rat brain mineralocorticoid receptor (MR)‐mRNA or 500 bases of the rat liver glucocorticoid receptor (GR)‐mRNA.Neurons in CA1, CA2, and the dentate gyrus expressed both receptor genes at high levels. The MR‐mRNA was demonstrated in all pyramidal cell fields (CA1–4) of the hippocampal formation and the granular neurons of the dentate gyrus. In contrast, GR‐mRNA was mainly restricted to CA1 and CA2 pyramidal cell fields and the dentate gyrus. This pattern of hybridization was found to agree with the cellular distribution of the two types of corticosteroid receptors detected previously in the hippocampus by autoradiography of the radio‐labeled receptors and by immunocytochemistry of the receptor protein. These observations suggest that the corticosteroid receptors described previously as type 1 and type 2 are encoded by MR‐ and GR‐mRNA, respectively.Although both the MR and GR genes are co‐expressed in some hippocampal neurons, the unique patterns of distribution of the two receptor mRNAs in the hippocampal formation suggest that the genes for these receptors are differentially regulated. Moreover, the microanatomy of MR and GR expression provides insight into molecular mechanisms underlying the characteristic action of various steroids on behaviors involved in stress and circadian regulation.
Simple method for the culture of glial cells from embryonic rat brain: Implications for regional heterogeneity and the radial glial lineage
Authors: Wilkie M. B. , Lauder J. M. 
Published: January 2005

AbstractA 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.
Developmental expression of neural cell type‐specific mRNA markers in the myelin‐deficient mutant rat brain: Inhibition of oligodendrocyte differentiation
Authors: Kumar S. , Gordon M. N. , Espinosa de los Monteros M. A. , de Vellis J. 
Published: January 2005

AbstractWe have studied gene expression of neuroglial cell markers in the myelin‐deficient (md) rat brain during postnatal development. Northern blots and slot blots of poly(A)+ RNA from developing brain were sequentially probed with cDNAs specific for the oligodendrocyte markers glycerol phosphate dehydrogenase (GPDH), myelin basic protein (MBP), and proteolipid protein (PLP), for the neuronal marker glutamic acid decarboxylase (GAD), and for the astrocyte markers glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS). GPDH mRNA levels were also examined in two peripheral tissues, liver, and skeletal muscle (hindlimb).Despite a lack of CNS myelin in the md mutant, transcripts of all oligodendroglial markers were detectable except the 1.6‐kb PLP message. Brain GPDH mRNA levels were initially equivalent in md and unaffected littermates at postnatal day 15 (PI5), but the mutants failed to display the normal developmental increase in gene expression. By P25, GPDH mRNA expression in md rat brain was approximately 20% of control levels. GPDH mRNA expression in peripheral tissues was less affected than in brain and was lower in md mutants only at the later developmental ages. Expressions of GAD, GFAP, and GS mRNAs in developing md rat brain were not altered. The mRNA levels of the two myelin markers, MBP and PLP, were severely impaired in md rat brain during the entire myelinating period and represented less than 10% of control mRNA levels at P25. The most important observation was that the large PLP transcript (3.2 kb) was slightly shorter in size in md rat brain as compared to normals. These data indicate that the md mutation does not affect the normal development of astrocytes or GABAergic neurons but severely inhibits the normal differentiation of oligodendrocytes, possibly because of an alteration in the PLP mRNA.
Development of identified glia that ensheathe axons in Hirudo medicinalis
Authors: Morrissey A. M. , McGlade‐McCulloh E. 
Published: January 2005

AbstractInteraction between neurons and glia may contribute to the formation of characteristic nerve bundles formed by axon elongation along stereotypic pathways. This study reports the temporal and spatial distribution of identified ensheathing glia during embryonic development in the leech. The development of connective glia was followed (1) using an immnohistochemical probe (monoclonal antibody Lan3–13), which recognized connective glia, and (2) using electron microscopy. Embryonic glia were initially located in the medial region of the lateral connectives and contained intermediate filaments. Glia cells continued to develop throughout embryogenesis; the number and size of glial processes increased, and they ensheathed smaller bundles of axons. The glial cell recognized by Lan3–13 first appeared after axons had already begun to form the connectives. This suggests that these particular glial cells may not function in the initial guidance of axons along stereotypic pathways. However, another cell that contained small bundles of intermediate filaments and glycogen granules was present at early stages of connective formation. These cells may be undifferentiated or transient glia, which could contribute to the formation of characteristic nerve bundles.
Anti‐200 kDa neurofilament antibody cross‐reacts with microtubule‐associated protein‐2 (MAP‐2)
Authors: Allende M. L. , Krauss R. Y. , Tremblay C. , Alvarez J. , Inestrosa N. C. 
Published: January 2005

AbstractAn antibody prepared against purified 200‐kDa neurofilament (NF) subunit was found to cross‐react with a high molecular weight polypeptide present in rat brain cytoskeletal extracts starting from early postnatal development. This polypeptide was found to be highly concentrated in microtubule preparations and was specifically recognized as the 280‐kDa microtubule‐associated protein‐2 (MAP‐2). Our results, besides suggesting the existence of common epitopes between the heavy NF subunit and MAP‐2, suggest the possibility of an interaction between two of the most important neuronal cytoskeletal organelles: NFs and microtubules.
Protein kinase C activators reduce the inositol trisphosphate‐Induced outward current and the CA2+‐activated outward current in identified neurons of aplysia
Authors: Sawada M. , Ichinose M. , Maeno T. 
Published: January 2005

AbstractEffects of intracellularly injected activators of protein kinase C on the InsP3‐induced K+current and the Ca2+‐activated K+current recorded from identified neurons (R9—R12) ofAplysia kurodaiwere investigated with conventional voltage‐clamp and pressureinjection techniques. Intracellular injection of InsP3into identified neurons produced a 4‐aminopiridine (4‐AP)‐resistant, tetraethylammonium (TEA)‐sensitive, and quinidine‐sensitive K+current similar to the Ca2+activated K+current elicited by direct injection of Ca2+ions into the same neurons.The diacylglycerol analogue 1,2‐oleoylacetylglycerol (OAG) at an intracellular concentration of 65 nM produced irreversible decreases in both the InsP3‐induced K+current and the Ca2+‐activated K+current. The phorbol 12,13‐dibutyrate (PDBu) at an intracellular concentration of 150 nM also decreased irreversibly both the InsP3‐induced K+current and the Ca2+‐activated K+current. These results suggest that protein kinase C activators reduce both the InsP3‐induced K+current and the Ca2+‐activated K+current recorded from certain identified neurons ofAplysiaand that protein kinase C reduces the ability of Ca2+to open K+channels rather than affecting the ability of InsP3to release Ca2+from intracellular stores.
Modulation of acetylcholine release by nicotinic receptors in the rat brain
Authors: De Sarno P. , Giacobini E. 
Published: January 2005

AbstractSince physostigmine (Phy) is presently used in the experimental treatment of Alzheimer disease (AD) patients by means of intracerebral ventricular (i.c.v.) administration, we designed a study to determine the effect of the drug administered by the same route on the cholinergic system of the rat brain. Particularly, we studied the involvement of nicotinic cholinergic function. The specific conditions required in this experiment were achieved by a series of short‐lasting periods of acetylcholinesterase (AChE) inhibition leading to short‐lasting increases of acetylcholine (ACh). These were produced by periodic i.c.v. injections of Phy. At 7 days of Phy administration, a small effect on 3H‐nicotine binding was seen only in the striatum of the injected side. In rats treated for 13 days, we observed a 120% increase in the stimulated release of 3H‐ACh in hippocampal slices of the injected side of the brain. There also was a significant 88% increase in 3H‐nicotinic binding in the hippocampus of the same side while muscarinic binding was unchanged. These results suggest a process of upregulation of presynaptic nicotinic autoreceptors in the hippocampus modulating ACh release but no effect on the muscarinic receptors. Our results also suggest that pulses of ACh in analogy to nicotinic stimulation can cause protracted desensitization and eventually inactivation of the receptor leading to its up‐regulation. These results are consistent with findings on the release of ACh from cortical biopsies and of a sustained ACh release in the CSF of AD patients following the same treatment.
Conditioned media of regenerating fish optic nerves modulate laminin levels in glial cells
Authors: Cohen A. , Schwartz M. 
Published: January 2005

AbstractAdult injured optic nerves of mammals show an increased distribution of laminin in the extracellular matrix after application of soluble substances in the form of conditioned media originating from growing nerves (Zak, et al., 1987). This increase could result from direct or an indirect activation of glial cells or from activation of other cellular elements. In the present study, we show that the conditioned media derived from regenerating fish optic nerves contain factors that directly modulate the level of laminin in C‐6 glioma cells. The identity of the laminin was confirmed by metabolic labeling of the treated cells with [35S]methionine and by subsequent immunoprecipitation and gel electrophoresis. The level of other extracellular matrix proteins, such as fibronectin, is also increased. The significance of the presence of glialactivating substances in the conditioned media of regenerating nerves for the process of regeneration is discussed.
Inhibition of the synthesis of glycosphingolipids affects the translocation of proteolipid protein to the myelin membrane
Authors: Pasquini J. M. , Guarna M. M. , Besio‐Moreno M. A. , Iturregui M. T. , Oteiza P. I. , Soto E. F. 
Published: January 2005

AbstractBrain slices obtained from young rats were incubated with different radioactive precursors, in the presence and absence of L‐cycloserine (an inhibitor of the synthesis of sphingosine) in order to explore the possibility that transport of proteolipids—and specifically of the major myelin proteolipid PLP—to the myelin membrane could be coupled to the transport of cerebrosides or sulfatides. At a concentration of 0.15 mM L‐cycloserine, the incorporation of [3H] glycine into total proteins, proteolipid apoproteins (APL), PLP, and myelin basic proteins (MBP) of the total homogenate was unaffected by the presence of the inhibitor, whereas the incorporation of [3H] serine into glycosphingolipids decreased markedly. Under similar incubation conditions, the entry of labeled APL and of PLP into the myelin membranes in the presence of L‐cycloserine decreased markedly (50%) in comparison to controls. Entry of MBP was not affected by the inhibitor. These results indicate that when synthesis of glycosphingolipids is inhibited by L‐cycloserine, thus decreasing the availability of cerebrosides and sulfatides, the translocation of PLP to myelin is disrupted, suggesting that its transport through the oligodendroglial cell could be coupled to the transport of glycosphingolipids and, most probably, of sulfatides.
Pre‐ and post‐natal ontogeny of serotonergic projections to the rat spinal cord
Authors: Rajaofetra N. , Sandillon F. , Geffard M. , Privat A. 
Published: January 2005

AbstractThe development of 5‐hydroxytryptamine (5‐HT) innervation in the spinal cord was studied from embryonic day 14 (E14) to adulthood. Sprague‐Dawley rats were fixed by perfusion with 5% glutaraldehyde in cacodylate‐sodium metabisulfite buffer, and vibratome sections were processed for immunocytochemistry with a 5‐HT antiserum. For electron microscopy, the sections were flat‐embedded in araldite, and thin sectioning was performed. 5‐HT neurons caudally directed from raphe nuclei invade the spinal cord at E14 and reach the caudalmost levels by E16‐E17. In longitudinal sections, axons are seen by E15, at cervical and upper thoracic levels, to invade the presumptive gray matter from the anterior and lateral funiculi. The invasion process occurred either by sharp angulation of the axon or by branching of a collateral. By E16, at thoracic level the anterior horn and the intermediolateral columns are profusely innervated by very thin, varicose fibers; synapses are seen at E17 and E18 using EM. 5‐HT immunoreactive boutons are involved here. After birth, 5‐HT innervation of these two areas evolves progressively from a diffuse network to a more restricted pattern, especially at the thoracic level for the intermediolateral column and at cervical and lumbar levels for the anterior horn. The adult pattern is reached by postnatal day 21 (P21). The growth of axons toward the dorsal horn becomes noticeable by E19 at all spinal levels, when fibers invade the neck of the horn from the lateral funiculus, and innvervation proceeds diffusely until P5. At P7, thin fibers course dorsally and laterally along the border of the gray matter and ramify profusely in layers I and II. The adult pattern is also reached in the dorsal horn by P21. These results are discussed in relation to the postnatal maturation of motor and sensory circuits and to the development of transplanted raphe neurons in the rat spinal cord.
Developmental and regional expression of three new members of the ras‐gene family in the mouse brain
Authors: Ayala J. , Olofsson B. , Touchot N. , Zahraoui A. , Tavitian A. , Prochiantz A. 
Published: January 2005

AbstractWe have examined the expression in the mouse nervous system of three new members of the ras protooncogene family: rab1, rab2, and rab3. Each of these genes was transcribed into messenger RNAs with different molecular weights. These transcripts had specific developmental and regional patterns of expression. In particular, for the three genes, the ratio between the heavy and light mRNAs depended strongly on developmental stage and brain region. The use of pure neuronal and glial cultures revealed that the high molecular weight transcripts were enriched in neurons and that, in the case of rab2 and rab3, their expression increased with neuronal differentiation. These results are discussed considering the sequence identities between these genes and the yeast YPT1 and sec‐4 genes, which are known to be implicated in post‐Golgi vesicular transport and cytoskeletal stabilization. We propose that the rab genes might be of importance in the regulation of these two processes within the developing and adult nervous system.
Glucose transport in primary cultured neurons
Authors: Heidenreich K. A. , Gilmore P. R. , Garvey W. T. 
Published: January 2005

AbstractIn this study, we have examined glucose uptake and its regulation by insulin in primary cultured neurons. Glucose transport was assessed by measuring the initial rate of uptake of 3H‐2‐deoxyglucose, a glucose analog that is transported and phosphorylated but not further metabolized. The uptake of 2‐deoxyglucose was saturable; measurements of the intracellular concentration of 2‐deoxyglucose and 2‐deoxyglucose‐6‐phosphate revealed that hexokinase activity rather than membrane transport is the rate‐limiting step for glucose uptake. Insulin had no effect on 2‐deoxyglucose uptake at low (0.2 mM) or high (20 mM) concentrations of substrate. The order of potency of other hexoses to competitively inhibit the accumulation of 2‐deoxyglucose was D‐glucose (0.2 mM) = D‐mannose (0.2 mM) > 30‐methylglucose (9 mM) > D‐galactose (90 mM). Cytochalasin B was a potent inhibitor of 2‐deoxyglucose uptake (IC50 = 500 nM) and phloretin was more potent than ploridzin in inhibiting uptake. The structure of glucose transporters was examined by photoaffinity labeling using 3H‐cytochalasin B and by immunologic detection using antibodies raised against the human erythrocyte transporter. 3H‐cytochalasin B labeled two proteins of 55 kDa and 43 kDa and the antibody recognized primarily a 43 kDa protein. The subcellular distribution of glucose transporters, estimated by measuring the number of specific cytochalasin B binding sites in subfractions of neuronal homogenates, showed 3.62 pmol/mg protein in the 11,000g pellet and 1.34 pmol/mg protein in the 200,000g pellet.In conclusion: (1)Neuronal glucose transport is not acutely regulated by insulin. (2) The kinetics of 2‐deoxyglucose uptake into neurons are determined largely by hexokinase activity rather than membrane transport. (3) The apparent molecular weight of neuronal glucose transporters is similar to transporters in other tissues. (4) The number of glucose transporters per milligram of protein is relatively low in neurons compared to other tissues.
Role for the oligodendrocyte cytoskeleton in myelination
Authors: Wilson R. , Brophy P. J. 
Published: January 2005

AbstractEnriched cultures of rat brain oligodendrocytes were extracted with a buffer that separated the cells into a Triton X‐100—soluble fraction and an insoluble cytoskeleton (CSK) residue. The buffer was optimised so that intact microtubules were preserved in the CSK residue. The partition of four myelin proteins between the soluble and the CSK fractions was determined by immunoblotting and immunofluorescence. Immunoblotting showed that two integral membrane proteins of myelin, the proteolipid protein (PLP) and the DM‐20 protein, were completely extracted under these conditions. By contrast, a substantial amount of myelin basic protein (MBP) and to a lesser extent 2,3‐cyclic nucleotide‐3‐phosphohydrolase (CNP) remained associated with the CSK residue. The association of these proteins with the CSK was confirmed by immunofluorescence. A remarkable difference in the distribution of microfilaments and microtubules was observed in oligodendrocytes. Immature cells possessed many fine processes that were rich in microfilaments. The cell body of these oligodendrocytes was devoid of microfilaments but did contain microtubules. Furthermore, a close association between CNP and microfilaments and between MBP and microtubules was revealed after detergent lysis. The strong interaction between CNP and filamentous actin was underlined by their concomitant disappearance from the extremeties of the cell at a later stage of development when extensive membrane sheets had formed. Mature cells had fewer, thicker processes than younger cells and their processes contained microtubules, not microfilaments. MBP was present throughout the thick processes and the membrane sheets. These observations suggest roles for CNP and MBP at distinct stages of myelin process formation and support a directive role for the oligodendrocyte's CSK in the formation of myelin.