bluuebunny/crossref_metadata_2025 huggingface dataset:
Acetylcholine sensitivity in myotubes of nerve‐muscle co‐culture cultured with anti‐muscle antibodies, α‐bungarotoxin andd‐tubocurarine
Authors: Kimura M. , Shikada K. , Nojima H. , Kimura I.
Published: April 2003

The effects of α‐bungarotoxin (α‐BuTX).d‐tubocurarine (d‐TC) and antibodies against muscle extract on acetylcholine (ACh) sensitivity were investigated in developing mouse myotubes in a nerve‐muscle co‐culture. Antibodies clearly suppressed the ACh potential amplitude in adult mouse diaphragm muscle, but antibodies in muscle pre‐treated withd‐TC (1 μg/ml) weakly suppressed it. The addition ofd‐TC to muscle extract dose‐dependently inhibited the formation of the immunoprecipitation lines. The exposure of developing myotubes to antibodies for 10 days in culture suppressed both resting potential and ACh potential, whereas co‐existence of α‐BuTX (1 μg/ml) ord‐TC (0.1 mg/ml) with antibodies suppressed ACh potential but did not affect resting potential compared with antibodies alone. The ACh potentials in myotubes cultured with α‐BuTX andd‐TC alone were also suppressed. The appearance (day 8 in culture) of this suppressive effect by α‐BuTX was faster than that (day 11 in culture) ofd‐TC. These different effects depending on the time in culture may account for the conformational change of developing ACh receptors to α‐BuTX andd‐TC.
Free amino acids of rat astrocytes in primary culture: Changes during cell maturation
Authors: Holopainen I. , Oja S. S. , Marnela Kirsi‐Marja , Kontro Pirjo
Published: April 2003

The concentrations of free amino acids were analysed in cultured primary astrocytes during cell maturation and in the starting material, i.e. the cerebral hemispheres of newborn rats. Taurine was the most abundant amino acid in all samples, the content of glutamine being comparable only in immature astrocytes (7 days in culture). The intracellular levels of most amino acids significantly decreased during the first 2 weeks in culture, remaining fairly stable during the third week.
Lactational ethanol exposure: Brain enzymes and [3h]spiroperidol binding
Authors: Lancaster F.E. , Selvanayagam P.F. , Hsu L.L.
Published: April 2003

Long‐Evans lactating rats were fed 27% calories as ethanol in a liquid diet to determine whether alcohol received through the milk would alter normal brain development in the offspring. On days 16, 21 and 30, brains of the female offspring were removed, corpus striatum dissected and assayed for choline acetyltransferase activity, glutamic acid decarboxylase activity and [3H]spiroperidol binding activity. At day 16, there were no differences among the three treatment groups for the enzyme activities assayed. At day 21, glutamic acid decarboxylase activity in the pairfed group was higher than in ET and CT groups. Choline acetyltransferase activity in the PF group was higher when compared to ad libitum controls and [3H]spiroperidol binding was not affected. At 30 days of age. animals exposed to ethanol had higher choline acetyltransferase activity and [3H]spiroperidol binding activity when compared to pairfed and ad libitum controls; and higher glutamic acid decarboxylase activity when compared to ad libitum controls.

Data from the present study suggest that ethanol exposure during the brain growth spurt has a toxic effect on the late development of dopaminergic, cholinergic and GABAergic systems in the corpus striatum. These results may be related to the clinical symptoms of hyperactivity and problems with motor control in children exposed to alcohol during the third trimester and during lactation.
Factors influencing neuronal growth in primary cultures derived from 3‐day‐old chick embryos
Authors: Mangoura Dimitra , Sakellaridis Nikos , Vernadakis Antonia
Published: April 2003

We compared neuronal growth patterns in primary cultures prepared by dissociating 3‐day‐old chick embryos, either whole embryo (E3WE) or head only (E3H) and plating the dispersed cells onto Petri dishes coated with either poly‐l‐lysine, collagen or laminin. The culture medium was Dulbecco's Modified Eagle's Medium (DMEM), supplemented with either 5 or 10% fetal bovine calf serum (FCS). As we have previously described, in E3WE cultures on poly‐l‐lysine the neuronal primary growth patterns were aggregation with neuritic fasciculation, presence of growth cones with microspikes and very few flat cells. In contrast with cultures grown on poly‐l‐lysine, in cultures grown on collagen or laminin the distinct growth pattern was extensive networks of isolated and differentiated neurons lying on acquired monolayers of flat cells. When 5% PCS was used, as compared to 10% PCS, neuronal aggregates were fewer and smaller on poly‐l‐lysine; on collagen or laminin a tendency to aggregate was observed. Several differences were observed in the E3H cultures when compared to E3WE: (a) aggregates were less numerous with the prevailing pattern being a web‐like, self‐contained aggregate; (b) aggregates connected with other aggregates or flat cells were rare and the aggregate adhesivity was minimized; (c) neurons on collagen or laminin formed networks with the exception of a few, small aggregates displaying no fasciculation; (d) flat cells did not form a monolayer but islets which hosted the neuronal meshy networks. We attribute these differences in the growth patterns between the various types of cultures to be the combined result of a variety of environmental signals, derived from the provided substrata, the serum and the nonneuronal cell factors and cell surface, all primarily regulating neuronal adhesivity.
Synapse formation and development of neurotransmitter functions in neuronal cells from chick brain cultured in a serum‐free, defined medium
Authors: Langui D. , Sarhan S. , Devilliers G. , Pettmann B. , Delaunoy J. P. , Seiler N. , Sensenbrenner M.
Published: April 2003

Cells dissociated from cerebral hemispheres of 8‐day‐old chick embryos were seeded on poly‐l‐lysine coated Petri dishes in serum‐containing medium. After 24 hr the culture medium was switched to a serum‐free, chemically defined medium. These cultures contain mainly neuronal cells until day 14, characterized by the presence of acetylcholinesterase activity and neurofilament proteins. After 2 weeks glial cells progressively contaminated the neuronal culture. Cultures were maintained for a period of 4 weeks. From day 6 on numerous synapses with clear vesicles were observed. The activity of choline acetyltransferase remained low throughout the culture period, while GABA levels increased in parallel with synaptogenesis. Our observations indicate that chick cerebral hemisphere neuronal cultures grown in serum‐free, chemically defined medium contain GABAergic neurons that undergo maturation.
Age‐dependent variation in the sensitivity of rat brain glutamine synthetase to l‐methionine‐dl‐sulfoximine
Authors: Rao V. L. Raghavendra , Murthy R. K.
Published: April 2003

Effects of a subacute dose (150 mg/kg body wt) of methionine sulfoximine was studied on the behavioural changes and glutamine synthetase activity in cerebral cortex, cerebellum and brain stem of rats of four different age groups. Animals of 10 days and 90 days age groups were less vulnerable to the toxic effects of methionine sulfoximine. Rats of 180 days age exhibited various behavioural changes upon the administration of methionine sulfoximine and entered into convulsions at the end of 17 hr. In rats of 360 days age group these changes appeared quite early and the animals convulsed at the end of 13 hr. Animals of these two age groups failed to recover from toxic effects of methionine sulfoximine. Methionine sulfoximine inhibited glutamine synthetase activity in the brains of rats of all age groups. Maximum inhibition of activity was noticed at the end of 12 hr in 10‐day‐old rats while in the animals of other age groups it was seen at the end of 3 hr. In animals of all age groups the enzyme activity was inhibited by 60–70% except in 360‐day‐old rats where the inhibition was 95%. Behavioural changes and inhibition of glutamine synthetase were out of phase with each other. It is suggested that the toxicity of methionine sulfoximine may not be due to its effect on glutamine synthetase alone. Further, these results also suggest that the toxic effects of methionine sulfoximine vary with the age of the animal.
Binding properties, regional ontogeny and localization of adrenergic receptors in chick brain
Authors: Dermon C. R. , Kouvelas E. D.
Published: April 2003

The pharmacological properties of [3H]‐WB4101, [3H]‐clonidine and [3H]‐dihydroalprenolol binding in chick brain membranes display the characteristics known for α1‐, α2‐ and β‐adrenergic binding sites, respectively. Kinetic studies performed at different embryonic and post‐hatching ages have shown one binding component for each one of the above radioactive ligands.

The ontogeny of α1, α2 and β binding sites was studied in cerebral hemispheres, optic lobes, brain stem and cerebellum. In all brain regions studied, the development of α2 binding sites precedes that of α1 and β, and a very significant decrease of α2 number was observed in the cerebellum, brain stem and optic lobes afterwards. The autoradiographic localization of adrenergic receptors was studied in the optic lobes and cerebellum. In the optic lobes the superficial layers of stratum griseum and fibrosum showed a strong selective labelling of α1, α2 and β binding sites and the strong selective labelling of α2 binding sites extended to the layer of stratum opticum. Among the nuclei located in the optic lobe only the nucleus mesencephalis lateralis pars dorsalis (MLD) exhibited a strong selective labelling for α1 binding sites while, for β binding sites, not only the MLD, but also the nucleus isthmic pars parvocellularis (Ipc) and the nucleus isthmic pars magnocellularisa (Imc) exhibited strong labelling. In the cerebellum strong selective labelling for α1 and β receptors was seen in the molecular layer. Labelling of the granule cell layer was almost equally strong for α1 but significantly less for β binding sites. No significant labelling could be detected for α2 binding sites.
Acetylcholinesterase in the development of chick dorsal root ganglia
Authors: Biagioni S. , Odorisio T. , Poiana G. , Scarsella G. , Augusti‐Tocco G.
Published: April 2003

Acetylcholinesterase is expressed in chick dorsal root ganglia neurons very early in development. Since the physiological role of the enzyme in these cells is still obscure, it appeared of interest to investigate its modifications in the course of development.

The specific activity of acetylcholinesterase in chick dorsal root ganglia increases, during in ovo development, from day E5 to day E13; after day E13 there is a decrease. Conversely, when acetylcholinesterase activity was expressed on a per ganglion basis, a continuous increase in the level of the enzyme until day E20 was observed.

Acetylcholinesterase is a polymorphic enzyme and its molecular forms have different cellular localizations. Two globular forms, a tetramer (G4) and a dimer (G2), are present in the ganglia, as in chick brain. G4 is the major form at day E5, where it represents about 85% of the activity. This form shows a progressive decrease since day E8, and at day E20 exhibits activity levels similar to those of G2.

It is known that acetylcholinesterase‐producing cells are also able to release the enzyme in the extracellular space. We determined the release of acetylcholinesterase by cultured dorsal root ganglia neurons at various developmental stages: acetylcholinesterase release is significantly increased at day E20, as compared to younger stages, and 90% of the enzyme released is G4.
Satellite cells in developing spinal ganglia. An immunohistochemical study
Authors: Lauriola Libero , Michetti Fabrizio , Coli Antonella , Bigotti Giulio , Cocchia Domenico
Published: April 2003

The present immunohistochemical study investigates the presence and distribution of S‐100‐containing glial cells in the early stages of development in human spinal ganglia. From the earliest ages investigated immunoreactive cells could be detected in a continuous layer at the periphery as well as inside ganglionic rudiments in close relationship with neural elements, both at the light and ultrastructural levels. The possibility that these glial cells, exhibiting such a distinctive distribution, play a modulatory role on microenvironmental influences during maturation could be taken into account. Neither glial fibrillary acidic protein nor myelin basic protein could be detected at the ages investigated.
Development and distribution of serotonin in the central nervous system of Manduca sexta during embryogenesis II. The ventral ganglia
Authors: Radwan Wafaa A. , Lauder Jean M. , Grange Noelle A.
Published: April 2003

The distribution of serotonin (5‐HT) immunoreactive cells and their projections was mapped in the ganglia of the ventral nerve cord of the tobacco hornworm, Manduca sexta, during embryonic development, using an antiserum to 5‐HT. Immunoreactive cells were first seen at 60% development. By 75% of embryonic development, a total of 94 immunoreactive cells were found in the ventral ganglia, including the suboesophageal ganglion. This number decreased to 80 neurons by 100% of development. About 50% of these cells were arranged in the abdominal ganglia and the rest were located in both the suboesophageal and thoracic ganglia. The suboesophageal ganglion exhibited immunoreactive segmentai interneurons in areas corresponding to the mandibular, maxillary and labial neuromeres. Two pairs of immunoreactive interneurons were also observed to occur bilaterally in each of the thoracic and abdominal ganglia, with the exception of the prothoracic ganglion. This ganglion contained three pairs of bilaterally arranged immunoreactive neurons as early as 60% of embryonic development. Serotonin immunoreactivity was also found in a number of efferent neurons in the mandibular and labial neuromeres of the suboesophageal ganglion and in the prothoracic, mesothoracic and posterior abdominal ganglia. The occurrence of 5‐HT in these efferent neurons suggests an involvement of serotonin in foreand hindgut function via its effect on the visceral muscles. Immunoreactive lateral longitudinal fibers extended along the entire length of the ventral nerve cord together with dense segmentai arborizations. The latter had regressed by the time the embryo was fully developed. This regression of the arborizations in the ganglia at the end of embryonic development indicates that a reorganization of 5‐HT innervation occurs to support new larval functions. The time of appearance of 5‐HT immunoreactive cells and fibers suggests that serotonin may play a role in the development of the ventral nerve cord.
Laminin and other basal lamina proteins with neurite promoting activity in medium conditioned by C6 glioma cells
Authors: Westermann R. , Mollenhauer J. , Johannsen M. , Unsicker K.
Published: April 2003

Neurite promoting activities (NPFs) are essential factors in neuronal differentiation. Some of them are associated with proteins of the extracellular matrix (ECM). C6 cells, a rat glioma cell line, release NPF activities into the cell culture medium. We used antibodies against ECM‐proteins for enrichment and partial characterization of these activities. Results show that, (1) C6 cells express and release laminin; (2) the C6‐laminin consists of 260 kD chains only and is therefore different from typical basal lamina laminin (220 and 440 kD chains), but comparable to other laminins of glial origin (chains in the 200 kD range only); (3) C6‐laminin partially purified by affinity chromatography shows NPF‐activity; (4) laminin concentration in C6 cell‐conditioned medium is not sufficient to account for the total neurite promoting activity of the medium, and (5) in addition to laminin C6 cells express and release fibronectin and possibly type IV collagen.
Expression of muscle‐specific isozymes of phosphorylase and creatine kinase in human muscle fibers cultured aneurally in serum‐free, hormonally/chemically enriched medium
Authors: Pegolo Giovanna , Askanas Valerie , Engel W. King
Published: April 2003

Primary cultures of muscle cells derived from a biopsied adult human skeletal muscle were grown up to 6 weeks in a hormonally/chemically enriched serum‐free medium. The expression of musclespecific isozymes of creatine kinase, glycogen phosphorylase, and phosphoglycerate mutase, indicative of muscle cell maturation, was studied after 1,4 and 6 weeks of growth. The maturation of muscle fibers cultured in serum‐free medium was comparable to that achieved by muscle fibers cultured in medium containing 10% serum and supplemented with growth factors (insulin, epidermal growth factor, and fibroblastic growth factor) and was greater than that achieved in medium containing 10% serum only.

Our study demonstrates that adult human muscle can be cultured aneurally for a long period of time in a serum‐free medium, and that it can achieve a high degree of maturation. This study provides an important basis for investigations related to: (1) assessment of the influence of individual components of the medium on human muscle maturation in culture; (2) studies of regulation of abnormal gene expression in diseased human muscle cultured in serum‐free medium.
Interactive effects involving different classes of excitatory amino acid receptors and the survival of cerebellar granule cells in culture
Authors: Balázs R. , Hack N. , Jørgensen O. S.
Published: April 2003

Differentiating granule cells develop survival requirements in culture which can be met by treatment with high K+ or N‐methyl‐d‐aspartate (NMDA) and, according to our recent findings, also with low concentrations of kainic acid (KA, 50 μM). We have now attempted to elucidate the mechanism(s) underlying the trophic effect of KA.

KA rescue of cells was completely suppressed by blockers of voltage‐ sensitive calcium channels, such as nifedipine in low concentrations (5×10−7 M), indicating that the promotion of cell survival is mediated through the activation of these channels by membrane depolarization. Thus the trophic influences of KA and NMDA share a common mechanism, increased Ca2+ influx (albeit through different routes), a conclusion that is supported by the observation that the effects of these agonists at concentrations causing maximal promotion of cell survival were not additive.

Interactive effects involving different classes of excitatory amino acid receptors were revealed by the potentiation of the KA rescue of cells by the NMDA receptor antagonists, 2‐amino 5‐phosphonovalerate (APV) or (+)‐5‐methyl‐10,11‐dihydro‐5H‐dibenzo[a,d]cyclohept‐5,10‐imine hydrogen maleate (MK‐801), which on their own failed to promote, but rather reduced cell survival. The potentiation of the KA effect by the competitive NMDA antagonist APV was counteracted by the weak NMDA agonist, quinolinic acid. These observations suggest that KA alone has both trophic and toxic effects, the latter being mediated secondarily through an NMDA‐like glutamate receptor, which is distinct from the conventional NMDA, KA and quisqualate preferring subtypes.
Taurine‐induced neuronal differentiation: the influence of calcium and the ganglioside gm1
Authors: Spoerri P. E. , Caple C. G. , Roisen F. J.
Published: April 2003

Taurine‐induced differentiation was examined in the murine neuroblastoma Neuro‐2a cell line in the presence or absence of the monosialoganglioside GM1 and under conditions in which Ca2+ levels were manipulated. Taurine (4 mM), GM1 (200 μg/ml), or taurine with GM1 were applied to culture media that contained either various concentrations of Ca2+ or the Ca2+ ionophore A23187. Taurine or GM1 and taurine with GM1 increased the number of cells emitting neuntes above that found for controls. A significant interaction was found between treatment (taurine, GM1 or taurine+GM1) and the manipulations of Ca2+ levels, affecting the number of neuntes and producing changes on the neuritic and perikaryal surfaces. Treatment with both taurine and taurine+GM1 and the various concentrations of Ca2+ resulted in a significant increase in neurite elongation. The Ca2+ ionophore A23187 in the presence of taurine or taurine+GM1 caused neuntes to grow longer than observed in media containing Ca2+, either in a low concentration (about 125 μM) or at 1–2 mM. Taurine‐treated cultures in the presence of extracellular Ca2+ or A23187 were characterized by surfaces with numerous microvillar, spine‐like projections. This effect was enhanced with GM1 and was less pronounced in the medium containing low levels of Ca2+. Transmission electron microscopy of the taurine‐stimulated neurons revealed an excessive number of clear‐core vesicles (40–200 nm in diameter) in perikarya, neuntes and neuritic varicosities and growth cones. In addition, numerous aggregates of intermediate filaments were seen. They were most abundant in the taurine+GM1 treated cultures. The taurine+A23187 cultures also exhibited numerous microtubules within the elongated processes. The different neuritic patterns induced by taurine under conditions in which Ca2+ levels were manipulated and/or when cells were exposed to exogenous GM1 suggest that taurine's actions depend in part on Ca2+ flux.
Thyroidal stimulation of tubulin and actin in primary cultures of neuronal and glial cells of rat brain
Authors: De Arunangsu , Chaudhury Sukanya , Sarkar Pranab Kumar
Published: April 2003

The influence of triiodothyronine (T3) on the level of tubulin and other proteins in primary cultures of neuronal (N) and glial (G) cells from rat brain has been investigated. Quantitation of tubulin by [3H]colchicine binding assay revealed that when cells from 1 day rat brain were cultured for 18 hr with physiological doses (0.5–5 nM) of T3, the hormone elicited 35–40% increase in the soluble (30,000 g supernatant) tubulin content of G cells only. This stimulation was age‐dependent and occurred neonatally at a time corresponding to the onset of synaptogenesis. In mouse and chick brain also, [3H]colchicine binding assay showed a similar selective stimulation of the soluble tubulin content of G cells by T3 with virtually no effect on N cells. However, SDS‐polyacrylamide gel electrophoresis of the total proteins in the 30,000 g supernatants from N and C cells of rat brain, labeled for 18 hr with [14C]leucine in the presence of T3, revealed that T3 elicited 2–3‐fold enhancement of radiolabeled tubulin in the N cells which is relatively greater than the 1.5‐fold increase seen in the G cells. Analysis of the autoradiograms of these labeled proteins also revealed that in addition to tubulin, T3 stimulated the accumulation of radiolabeled actin by 1.5‐ and 2‐fold in N cells and G cells respectively. Similar electro‐phoretic analysis of the solubilized labeled proteins in the 30,000 g pellets from N and G cells indicated that the failure to detect the stimulation of tubulin in the 30,000 g supernatants from N cells by [3H]colchicine binding assay could be at least partly due to rapid translocation of the dimeric soluble tubulin into insoluble membrane fractions or due to presence of higher oligometric forms of tubulin which are insensitive to [3H]colchicine binding assay.
An immunohistochemical study of neurotransmitter profiles in developing human visual cortex
Authors: Masood Farzana , Wadhwa Shashi , Bijlani Veena
Published: April 2003

The temporal pattern of development and distribution of gamma aminobutyric acid, serotonin, substance P and neuropeptide Y immunoreactive profiles was studied in the human visual cortex from 16 to 26 weeks of gestation, using an immunohistochemical technique. The immunoreactive profiles showed an increase in number and a change in their morphology and distribution pattern over the time period studied. A large number of neurons, fibers and terminals were stained with GABA antibody at 17–18 weeks and were distributed throughout the five zones of the developing visual cortex. GABA neurons were non‐pyramidal and bipolar in form at 17–18 weeks while at 18–19 and 20–21 weeks the cells of subplate and intermediate zones were multipolar. Substance P and serotonin immunopositive fibers were present mainly in the intermediate zone at 16 and 17–18 weeks, where they were oriented in a horizontal manner. At subsequent ages they invaded the other zones also. Substance P positive neurons could be visualized only at 26 weeks of gestation in the intermediate, subventricular and ventricular zones; no cell bodies, however, stained with serotonin antibody. Neuropeptide Y immunoreactive cells and fibers were first seen in the intermediate zone but later were found to be distributed in other zones too. The observations indicate that the intermediate zone of the visual cortex in which the transmitters and peptides appear earlier assumes importance in the normal development as also noted in other mammals.
Butyrylcholinesterase activity in the developing auditory brainstem, the choroid plexus and the pituitary of the perinatal rat
Authors: Krupnik Eduardo , Paterson J.A.
Published: April 2003

The butyrylcholinesterase activity in the vasculature of the brain, choroid plexus, and pituitary, was studied histochemically in rats during postnatal days 1,7,14,21 and 28. The brainstem auditory nuclei were used for comparison of vessels at different ages. We found intense butyrylcholinesterase activity in all intraparenchymal blood vessels, especially capillaries, in all ages. In the meningeal vessels, activity was especially prominent in 1 and 7 day old animals when the perineural meninges was relatively thick. In the pituitary, reaction for the enzyme was found in nonvascular elements, especially in the intermediate and posterior lobes. Vessels of the choroid plexus were associated with punctate regions of butyrylcholinesterase activity. These results do not support the suggestion of a major role for butyrylcholinesterase in the blood‐brain barrier.
Histochemical study by lectin binding of surface glycoconjugates in the developing olfactory system of rat
Authors: Franceschini Valeria , Lazzari Maurizio , Revoltella Roberto Paolo , Ciani Franco
Published: April 2003

Lectin‐binding histochemistry was used to investigate the distribution and density of defined carbohydrate sequences on the cell surface glycoproteins of the olfactory receptors of rat during development. The olfactory and vomeronasal receptors showed a positive labelling after biotinylated Lycopersicum esculentum lectin binding on embryonic day 16 (E16), while horseradish peroxidase‐labelled Glycine max, Bandeiraea simplicifolia (BS A‐I) and its B4 isomer BSA‐I‐B4 agglutinins started to label from day 18 (E18). From this stage onward there was a progressive increase in the intensity and number of lectin‐binding olfactory receptors. The first lectin‐labelled bundles of axons penetrating the olfactory bulb were observed on E20; from E21 it was possible to identify the first labelled glomeruli that, on the first day (P1) of postnatal life, showed a feature very similar to that of the adult. The lectin staining patterns indicate that during development there are differences in the kind and distribution of saccharidic moieties on the surface of rat olfactory neurons. The possible role of carbohydrate‐containing glycoproteins in the reception and transduction of the odours and in the modulation of the cell‐cell interactions in the olfactory system is discussed.
Serum factors and hydrocortisone influence the synthesis of myelin basic proteins in mouse brain primary cultures
Authors: Byravan Sujatha , Campagnoni Anthony T.
Published: April 2003

Mouse brain primary cultures were used to study the influence of serum factors and hydrocortisone on myelin basic protein (MBP) gene expression. Serum factors increased the synthesis of the MBP isoforms in 18‐day and older cultures. Synthesis of the 17 and 18.5 kDa MBPs steadily increased from 14 to 26 DIV (daysin vitro). Synthesis of the 14 kDa MBP reached a peak at 22 days, after which it fell off rapidly. Addition of serum to the medium also stimulated MBP mRNA expression. However, in the presence of serum, maximal stimulation of MBP mRNA expression occurred at 16–20 days, significantly earlier than maximal stimulation of 17 and 18.5 kDa MBP synthesis by serum. These observations suggest that serum influences both transcriptional and post‐transcriptional steps in the expression of the MBP genes in primary cultures. Hydrocortisone increased the synthesis of the 14,18.5 and 17 kDa MBP isoforms by two‐ to three‐fold. This effect was seen in cultures older than 15 DIV. This effect of hydrocortisone on the synthesis of the MBPs may be responsible for the increase in the steady state levels of MBP in the presence of hydrocortisone. These studies suggest a role for serum factors and hydrocortisone in the transcriptional and post‐transcriptional steps of MBP gene expression. They also suggest that this role may be developmentally regulated.
Loss of activity of the selenoenzyme thioredoxin reductase causes induction of hepatic heme oxygenase‐1
Authors: Mostert Volker , Hill Kristina E , Burk Raymond F
Published: April 2003

The stress response enzyme heme oxygenase (HO)‐1 is induced in livers of selenium‐deficient rodents, probably to compensate for loss of certain selenoproteins. We sought to identify those selenoproteins. Selenium‐replete mice with genetic deletion of selenoprotein P or glutathione peroxidase‐1 did not have elevated hepatic HO activity, thus ruling out involvement of those selenoproteins in HO‐1 induction by selenium deficiency. However, inhibition of thioredoxin reductase (TrxR) by a low dose of gold in the form of aurothioglucose led to induction of hepatic HO activity. Moreover, further induction by phenobarbital was observed. This HO‐1 induction pattern is also seen in selenium‐deficient mice. In the rat hepatoma cell line H4IIE, inhibition of TrxR by aurothioglucose or by 1‐chloro‐2,4‐dinitrobenzene led to induction of HO‐1. We conclude that loss of TrxR is responsible for the induction of HO‐1 by selenium deficiency.
DNA target sequence and FNR‐dependent gene expression
Authors: Scott Colin , Partridge Jonathan D , Stephenson James R , Green Jeffrey
Published: April 2003

FNR proteins are global transcription regulators that respond to fluctuations in environmental oxygen. They recognise a DNA target consisting of an inverted repeat, TTGATN1N2N3N4ATCAA (where N1–4 represents a non‐conserved tetrad, NCT). Analysis of 68 known and predicted FNR sites from the Escherichia coli K12 genome revealed a bias toward A or T at positions N2 and N3 of the NCT. The effect of the NCT sequence on FNR‐dependent transcription in vivo was assessed using a series of class II and class I model promoters with different NCT sequences. Changing the NCT sequence did not affect basal activity but altered anaerobic induction by as much as an order of magnitude. Thus, the NCT sequence is a fundamental component in setting the dynamic range of the FNR switch.
Solution structure of an antimicrobial peptide buforin II
Authors: Yi Gwan-Su , Park Chan Bae , Kim Sun Chang , Cheong Chaejoon
Published: April 2003

The structure of 21‐residue antimicrobial peptide buforin II has been determined by using NMR spectroscopy and restrained molecular dynamics. Buforin II adopts a flexible random structure in H2O. In trifluoroethanol (TFE)/H2O (1 : 1, v/v) mixture, however, buforin II assumes a regular α‐helix between residues Val12 and Arg20 and a distorted helical structure between residues Gly7 and Pro11. The model structure obtained shows an amphipathic character in the region from Arg5 to the C‐terminus, Lys21. Like other known cationic antimicrobial peptides, the amphipathic structure might be the key factor for antimicrobial activity of buforin II.
5 S rRNA: structure and interactions
Authors: SZYMAŃSKI Maciej , BARCISZEWSKA Mirosawa Z. , ERDMANN Volker A. , BARCISZEWSKI Jan
Published: April 2003

5S rRNA is an integral component of the large ribosomal subunit in all known organisms. Despite many years of intensive study, the function of 5S rRNA in the ribosome remains unknown. Advances in the analysis of ribosome structure that have revealed the crystal structures of large ribosomal subunits and of the complete ribosome from various organisms put the results of studies on 5S rRNA in a new perspective. This paper summarizes recently published data on the structure and function of 5S rRNA and its interactions in complexes with proteins, within and outside the ribosome.
Role for AMP-activated protein kinase in glucose-stimulated insulin secretion and preproinsulin gene expression
Authors: da SILVA XAVIER Gabriela , LECLERC Isabelle , VARADI Aniko , TSUBOI Takashi , MOULE S. Kelly , RUTTER Guy A.
Published: April 2003

AMP-activated protein kinase (AMPK) has recently been implicated in the control of preproinsulin gene expression in pancreatic islet β-cells [da Silva Xavier, Leclerc, Salt, Doiron, Hardie, Kahn and Rutter (2000) Proc. Natl. Acad. Sci. U.S.A. 97, 4023–4028]. Using pharmacological and molecular strategies to regulate AMPK activity in rat islets and clonal MIN6 β-cells, we show here that the effects of AMPK are exerted largely upstream of insulin release. Thus forced increases in AMPK activity achieved pharmacologically with 5-amino-4-imidazolecarboxamide riboside (AICAR), or by adenoviral overexpression of a truncated, constitutively active form of the enzyme (AMPKα1.T172D), blocked glucose-stimulated insulin secretion. In MIN6 cells, activation of AMPK suppressed glucose metabolism, as assessed by changes in total, cytosolic or mitochondrial [ATP] and NAD(P)H, and reduced increases in intracellular [Ca2+] caused by either glucose or tolbutamide. By contrast, inactivation of AMPK by expression of a dominant-negative form of the enzyme mutated in the catalytic site (AMPKα1.D157A) did not affect glucose-stimulated increases in [ATP], NAD(P)H or intracellular [Ca2+], but led to the unregulated release of insulin. These results indicate that inhibition of AMPK by glucose is essential for the activation of insulin secretion by the sugar, and may contribute to the transcriptional stimulation of the preproinsulin gene. Modulation of AMPK activity in the β-cell may thus represent a novel therapeutic strategy for the treatment of type 2 diabetes mellitus.
Differential effects of hyperphosphorylation on splicing factor SRp55
Authors: LAI Ming-Chih , LIN Ru-Inn , TARN Woan-Yuh
Published: April 2003

Members of the serine/arginine-rich (SR) protein family play an important role in both constitutive and regulated splicing of precursor mRNAs. Phosphorylation of the arginine/serine dipeptide-rich domain (RS domain) can modulate the activity and the subcellular localization of SR proteins. However, whether the SR protein family members are individually regulated and how this is achieved remain unclear. In this report we show that 5,6-dichloro-1β-d-ribofuranosyl-benzimidazole (DRB), an inhibitor of RNA polymerase II-dependent transcription, specifically induced hyperphosphorylation of SRp55 but not that of any other SR proteins tested. Hyperphosphorylation of SRp55 occurs at the RS domain and appears to require the RNA-binding activity. Upon DRB treatment, hyperphosphorylated SRp55 relocates to enlarged nuclear speckles. Intriguingly, SRp55 is specifically targeted for degradation by the proteasome upon overexpression of the SR protein kinase Clk/Sty. Although a destabilization signal is mapped within the C-terminal 43-amino acid segment of SRp55, its adjacent lysine/serine-rich RS domain is nevertheless critical for the Clk/Sty-mediated degradation. We report for the first time that SRp55 can be hyperphosphorylated under different circumstances whereby its fate is differentially influenced.
Three-dimensional Weibel instability in astrophysical scenarios
Authors: Fonseca Ricardo A. , Silva Luı́s O. , Tonge John W. , Mori Warren B. , Dawson John M.
Published: April 2003

Near equipartition magnetic fields are predicted by gamma ray bursters models and astronomical observations, in general associated with shocks or regions with colliding streams of particles. These scenarios require the conversion of kinetic energy in the outgoing plasma shells into B-fields. How the magnetic fields are generated and how particles are accelerated is still an open question, that can only be definitely addressed via fully kinetic three-dimensional (3D) numerical simulations. These shocks are collisionless because dissipation is dominated by wave–particle interactions, i.e., it is accomplished by particle scattering in turbulent electromagnetic fields generated at the shock front, or equivalently the mean free path is much longer than the shock front thickness (a few collisionless skin depths or a few Larmor radii, in magnetized plasmas). Plasma instabilities driven by streaming particles, such as the Weibel instability, are responsible for the excitation of these turbulent electromagnetic fields. Three-dimensional fully kinetic electromagnetic relativistic particle-in-cell simulations for the collision of two interpenetrating plasma shells were performed using the code OSIRIS [Fonseca et al., Lect. Notes Comput. Sci. 2331, 342 (2002)], showing (i) the generation of long-lived near-equipartition quasistatic (electro)magnetic fields, (ii) nonthermal particle acceleration, and (iii) short-scale to long-scale B-field evolution. These results may be important to understand magnetic field generation and particle acceleration in relativistic collisionless shock fronts, in gamma ray bursters, pulsar winds, and radio supernovae, and open the way to the full 3D kinetic modeling of relativistic shocks.
Formation of electron internal transport barrier and achievement of high ion temperature in Large Helical Device
Authors: Takeiri Y. , Shimozuma T. , Kubo S. , Morita S. , Osakabe M. , Kaneko O. , Tsumori K. , Oka Y. , Ikeda K. , Nagaoka K. , Ohyabu N. , Ida K. , Yokoyama M. , Miyazawa J. , Goto M. , Narihara K. , Yamada I. , Idei H. , Yoshimura Y. , Ashikawa N. , Emoto M. , Funaba H. , Inagaki S. , Isobe M. , Kawahata K. , Khlopenkov K. , Kobuchi T. , Komori A. , Kostrioukov A. , Kumazawa R. , Liang Y. , Masuzaki S. , Minami T. , Morisaki T. , Murakami S. , Muto S. , Mutoh T. , Nagayama Y. , Nakamura Y. , Nakanishi H. , Narushima Y. , Nishimura K. , Noda N. , Ohdachi S. , Ozaki T. , Peterson B. J. , Sagara A. , Saito K. , Sakakibara S. , Sakamoto R. , Sasao M. , Sato K. , Sato M. , Seki T. , Shoji M. , Suzuki H. , Tamura N. , Tanaka K. , Toi K. , Tokuzawa T. , Watanabe K. Y. , Watari T. , Xu Y. , Yamada H. , Yoshinuma M. , Itoh K. , Ohkubo K. , Satow T. , Sudo S. , Uda T. , Yamazaki K. , Hamada Y. , Matsuoka K. , Motojima O. , Fujiwara M. , Notake T. , Takeuchi N. , Torii Y. , Yamamoto S. , Yamamoto T. , Akiyama T. , Goncharov P. , Saida T. , Kawazome H. , Nozato H.
Published: April 2003

An internal transport barrier (ITB) was observed in the electron temperature profile in the Large Helical Device [O. Motojima et al., Phys. Plasmas 6, 1843 (1999)] with a centrally focused intense electron cyclotron resonance microwave heating. Inside the ITB the core electron transport was improved, and a high electron temperature, exceeding 10 keV in a low density, was achieved in a collisionless regime. The formation of the electron-ITB is correlated with the neoclassical electron root with a strong radial electric field determined by the neoclassical ambipolar flux. The direction of the tangentially injected beam-driven current has an influence on the electron-ITB formation. For the counter-injected target plasma, a steeper temperature gradient, than that for the co-injected one, was observed. As for the ion temperature, high-power NBI (neutral beam injection) heating of 9 MW has realized a central ion temperature of 5 keV with neon injection. By introducing neon gas, the NBI absorption power was increased in low-density plasmas and the direct ion heating power was much enhanced with a reduced number of ions, compared with hydrogen plasmas.
Recent results from the electron cyclotron heated plasmas in Tokamak à Configuration Variable (TCV)
Authors: Henderson M. A. , Alberti S. , Angioni C. , Arnoux G. , Behn R. , Blanchard P. , Bosshard P. , Camenen Y. , Coda S. , Condrea I. , Goodman T. P. , Hofmann F. , Hogge J.-Ph. , Karpushov A. , Manini A. , Martynov An. , Moret J.-M. , Nikkola P. , Nelson-Melby E. , Pochelon A. , Porte L. , Sauter O. , Ahmed S. M. , Andrèbe Y. , Appert K. , Chavan R. , Degeling A. , Duval B. P. , Etienne P. , Fasel D. , Fasoli A. , Favez J.-Y. , Furno I. , Horacek J. , Isoz P. , Joye B. , Klimanov I. , Lavanchy P. , Lister J. B. , Llobet X. , Magnin J.-C. , Marlétaz B. , Marmillod P. , Martin Y. , Mayor J.-M. , Mylnar J. , Paris P. J. , Perez A. , Peysson Y. , Pitts R. A. , Raju D. , Reimerdes H. , Scarabosio A. , Scavino E. , Seo S. H. , Siravo U. , Sushkov A. , Tonetti G. , Tran M. Q. , Weisen H. , Wischmeier M. , Zabolotsky A. , Yhuang G.
Published: April 2003

In noninductively driven discharges, 0.9 MW second harmonic (X2) off-axis co-electron cyclotron current drive deposition is combined with 0.45 MW X2 central heating to create an electron internal transport barrier (eITB) in steady plasma conditions resulting in a 1.6-fold increase of the confinement time (τEe) over ITER-98L-mode scaling. The eITB is associated with a reversed shear current profile enhanced by a large bootstrap current fraction (up to 80%) and is sustained for up to 10 current redistribution times. A linear dependence of the confinement improvement on the product of the global shear reversal factor (q0/qmin) and the reversed shear volume (ρq-min2) is shown. In other discharges heated with X2 the sawteeth are destabilized (respectively stabilized) when heating just inside (respectively outside) the q=1 surface. Control of the sawteeth may allow the avoidance of neoclassical tearing modes that can be seeded by the sawtooth instability. Results on H-mode and highly elongated plasmas using the newly completed third harmonic (X3) system and achieving up to 100% absorption are also discussed, along with comparison of experimental results with the TORAY-GA ray tracing code [K. Matsuda, IEEE Trans. Plasma Sci. PS-17, 6 (1989); R. H. Cohen, Phys. Fluids 30, 2442 (1987)].
Transport by intermittency in the boundary of the DIII-D tokamak
Authors: Boedo J. A. , Rudakov D. L. , Moyer R. A. , McKee G. R. , Colchin R. J. , Schaffer M. J. , Stangeby P. G. , West W. P. , Allen S. L. , Evans T. E. , Fonck R. J. , Hollmann E. M. , Krasheninnikov S. , Leonard A. W. , Nevins W. , Mahdavi M. A. , Porter G. D. , Tynan G. R. , Whyte D. G. , Xu X.
Published: April 2003

Intermittent plasma objects (IPOs), featuring higher pressure than the surrounding plasma, are responsible for ∼50% of the E×BT radial transport in the scrape off layer (SOL) of the Doublet III D (DIII-D) tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] in L- and H-mode discharges. Conditional averaging reveals that the IPOs are positively charged and feature internal poloidal electric fields of up to 4000 V/m. The IPOs move radially with E×BT/B2 velocities of ∼2600 m/s near the last closed flux surface (LCFS), and ∼330 m/s near the wall. The IPOs slow down as they shrink in size from 2 cm at the LCFS to 0.5 cm near the wall. The skewness (i.e., asymmetry of fluctuations from the average) of probe and beam emission spectroscopy data indicate IPO formation at or near the LCFS and the existence of positive and negative IPOs which move in opposite directions. The particle content of the IPOs at the LCFS is linearly dependent on the local density and decays over ∼3 cm into the SOL while their temperature decays much faster (∼1 cm).
Basis set dependent SCα exchange-only and exchange-correlation calculations
Authors: González I. , González C. , Karasiev V. V. , Ludeña E. V. , Hernández A. J.
Published: April 2003

The SCα method [V. V. Karasiev and E.V. Ludeña, Phys. Rev. A 65, 062510 (2002)], has been implemented into a local version of the GAUSSIAN 98 program package. Using this modified code we have calculated total energies of selected atoms and molecules belonging to the G2 set within the KS-exchange-only and KS-exchange-correlation approximations. In these calculations we have used the exchange functionals LDA, B1, and PW91 and their SCα counterparts: SCα-LDA, SCα-B1, and SCα-PW91. The corresponding exchange-correlation functionals are B3LYP and SCα-B3LYP. We have also explored the basis set dependence of the SCα method by calculating the KS-exchange-only atomization energies using the following hierarchy of basis set functions: STO-3G, 6-31G*, 6-31G**, and 6-311++G(3df,3pd). The average error values of the SCα calculations (with respect to exact exchange EXX values) are 121, 133, and 128 kJ mol−1 (for the SCα-LDA, SCα-PW91, and SCα-B1 methods, respectively) for the STO-3G basis set; 20, 27, and 19 kJ mol−1 (for the SCα-LDA, SCα-PW91, and SCα-B1 functionals) for the 6-31G**; and 7, 10, 5 kJ mol−1, respectively, for the 6-311++G(3df,3pd). Hence, it is seen that the application of the SCα method to LDA, B1, and PW91 exchange functionals, yields atomization energies in close agreement with the EXX ones as long as a large enough basis set is used. Moreover, the SCα atomization energies calculations performed using the modified GAUSSIAN 98 code (for the spin unrestricted case), are much closer to the EXX values than those obtained using a spin-restricted numerical code.
High-pressure, high-strain-rate lattice response of shocked materials
Authors: Kalantar Daniel H. , Belak J. , Bringa E. , Budil K. , Caturla M. , Colvin J. , Kumar M. , Lorenz K. T. , Rudd R. E. , Stölken J. , Allen A. M. , Rosolankova K. , Wark J. S. , Meyers M. A. , Schneider M.
Published: April 2003

Laser-based shock experiments have been conducted in thin Si and Cu crystals at pressures above the published Hugoniot Elastic Limit (HEL) for these materials. In situ x-ray diffraction has been used to directly measure the response of the shocked lattice during shock loading. Static film and x-ray streak cameras recorded x rays diffracted from lattice planes both parallel and perpendicular to the shock direction. In addition, experiments were conducted using a wide-angle detector to record x rays diffracted from multiple lattice planes simultaneously. These data showed uniaxial compression of Si (100) along the shock direction and three-dimensional compression of Cu (100). In the case of the Si diffraction, there was a multiple wave structure observed. This is evaluated to determine whether there is a phase transition occurring on the time scale of the experiments, or the HEL is much higher than previously reported. Results of the measurements are presented.
Magnetohydrodynamic-activity-induced toroidal momentum dissipation in collisionless regimes in tokamaks
Authors: Shaing K. C.
Published: April 2003

It is shown that in the presence of magnetohydrodynamic (MHD) activities, such as resistive wall mode, the toroidal symmetry in tokamaks is broken. This results from the modification on |B|, and the variation of |B| on the distortion of the magnetic surface due to the MHD activities. Here, B is the magnetic field. The toroidal plasma viscosity in the collisionless regime for the nonresonant MHD modes is calculated. It scales like (δB/|B|)2 with δB, the typical magnitude of the perturbed magnetic field strength. The theory is applied to determine the toroidal flow speed in the presence of these modes.
Bound-exciton-induced current bistability in a silicon light-emitting diode
Authors: Sun J. M. , Dekorsy T. , Skorupa W. , Schmidt B. , Helm M.
Published: April 2003

A bound-exciton-induced current bistability is observed under forward bias in an efficient silicon light-emitting diode at low temperatures. Two stable states of the S-type differential conductivity correspond to empty and filled states of bound excitons, respectively. The relationship between the current–voltage characteristic and the bound-exciton population can be accounted for using a rate equation model for bound and free excitons. The consistency between the theoretical and experimental results indicates that bound excitons, despite their neutral-charged states, contribute to the current bistability in silicon p–n junction diodes.