bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of homospecific activity of GABA‐transaminase in the mouse cerebral cortex and cerebellum and in neurons cultured from these brain areas
Authors: Schousboe Inger , Larsson Orla M. , Schousboe Arne 
Published: April 2003

AbstractThe homospecific activity of GABA‐transaminase (EC 2.6.1.19; GABA‐T) in brain or neurons was determined as a function of development in vivo or in culture by measuring the enzyme activity together with the relative amount of GABA‐T apoenzyme by the aid of a monospecific anti‐GABA‐T antibody. It was observed that both in cerebral cortex and cerebellum in vivo and in neurons cultured from these brain regions the homospecific activity of GABA‐T changed during development. By incubation of tissue extracts with similar extracts in which GABA‐T activity had been selectively and irreversibly destroyed with gamma‐vinyl GABA (Vigabatrin) it was established that this change in homospecific activity was at least partly due to the presence of an endogenous activator of GABA‐T. The results point towards a rather complex endogenous regulation of GABA‐T during development in vivo and in vitro.
Developing rat cerebellum—II. Effects of abnormal thyroid states and undernutrition on hyaluronic acid
Authors: Normand G. , Vitiello F. , Clos J. , Gombos G. 
Published: April 2003

AbstractThe early postnatal pattern of hyaluronic acid (HA) deposition in rat cerebellum is affected by thyroid deficiency, thyroxine treatment and undernutrition. The modification of HA ontogenesis apparently reflects the smaller number of cells formed in undernourished rats, or alterations of cell maturation (accelerated in thyroxine‐treated and slowed down in thyroid‐deficient rats). The developmentally regulated:loss of tissue water is also affected in the three conditions; this can be correlated with the roughly simultaneous disappearance of extracellular, but not of total, HA.
Vimentin‐GFAP transition in primary dissociated cultures of rat embryo spinal cord
Authors: Bignami Amico , Dahl Doris 
Published: April 2003

AbstractPrimary dissociated cultures derived from 15‐day‐old rat embryo spinal cord with or without dorsal root ganglia (DRG) were grown on polylysine, Primaria® and laminin substrates. On polylysine and Primaria substrates, spinal cord neurons formed aggregates connected by bundles of neurites in a distinctive pattern similar to that observed in cultures derived from embryonal rat brain and neonatal rat cerebellum. After 2 days in culture, the number of cells stained with GFAP antibodies progressively increased within the vimentin‐positive monolayer surrounding the neuronal aggregates. These astrocytes had the typical appearance of astrocytes in primary dissociated cultures derived from late fetal or early neonatal murine brain, i.e. large flat or stellate cells with thick processes staining equally well with GFAP and vimentin antibodies. Astrocytes found within the neuronal aggregates in 4–5 day cultures were markedly different, i.e. small stellate cells with slender processes forming a delicate mesh throughout the aggregate. These GFAP‐positive cells stained only weakly with vimentin antibodies. Spinal cord neurons formed aggregates on laminin substrates but failed to extend neurites and rapidly degenerated. The large flat cells in the surrounding monolayer gradually invaded the aggregates. These cells stained with both GFAP and vimentin antibodies. DRG neurons developed equally well on Primaria and laminin substrates, extending their neurites on the vimentin‐positive flat cells forming the monolayer regardless of their reactivity with GFAP antibodies.
Growth promoting effects of IGF‐I on fetal hypothalamic cell lines under serum‐free culture conditions
Authors: Torres‐Aleman Ignacio , Naftolin Frederick , Robbins Richard J. 
Published: April 2003

AbstractRecent evidence indicates that the insulin‐like family of peptides may act as endogenous trophic factors in the central nervous system. To further examine this possibility we have investigated the effects of three insulin‐like peptides on thein vitro growth of fetal hypothalamic cell lines. Two virally transformed rat hypothalamic cell lines which have been developed in our laboratory (A‐6 and F‐12) were used. Cells were plated at varying densities and cultured in the presence or absence of either insulin‐like growth factor I (IGF‐I), insulin, or multiplication stimulating activity (MSA or IGF‐II), in serum‐free medium for 1 wk. Cell growth was assessed by counting or by measuring cellular incorporation of3H‐thymidine. Of the three peptides tested IGF‐I was the most potent in eliciting cell growth. Insulin also stimulated growth of both cell lines, but was 100 times less potent for A‐6 cells while it was equipotent with IGF‐I in F‐12 cells. MSA had no effect on either cell line. Both IGF‐I and insulin showed dose‐response effects in increasing cell growth. We also found that the two cell lines had the greatest response to IGF‐I at low cell densities. Finally, time‐course experiments suggested that a continued presence of the peptide is essential for the growth‐promoting effects. We conclude that IGF‐I is a potent growth factor for virally transformed cell lines derived from the rat fetal hypothalamus. Since both IGF‐I immunoreactivity and IGF‐I receptors have been located in this diencephalic area these results suggest that IGF‐I may constitute a mitogenic signal for hypothalamic cells during neurogenesis.
Retinoids increase perinatal spinal cord neuronal survival and astroglial differentiation
Authors: Wuarin L. , Sidell N. , de Vellis J. 
Published: April 2003

AbstractIn this report we demonstrate that retinol and retinoic acid (RA) increase the survival and morphological differentiation of rat spinal cord neurons in vitro. Micromolar amounts of retinol and RA increased the number of surviving neurons by 2‐ to 3‐fold and affected neuritic density resulting in increased secondary and tertiary processes compared to untreated sister cultures. A marked morphological differentiation of the astrocyte population in conjunction with an antiproliferative effect in the presence of retinoids were apparent. These trophic effects occurred mainly after 5 days in vitro, a time that corresponds to the time of birth in vivo. Retinoic acid exerted a direct trophic effect on spinal cord neurons in the absence of glial cells while retinol lost its effectiveness. Metabolic labeling suggested that retinol is converted to the biologically active RA within astrocytes but not in neurons. Taken together, our results have demonstrated direct trophic effects of RA on spinal cord neurons and have suggested another role for astrocytes in the maintenance of normal neural physiology by regulating RA concentrations through the oxidation of retinol.
Changes in the expression of acetylcholinesterase molecular forms during rat heart development
Authors: Nyquist‐Battie Cynthia 
Published: April 2003

AbstractThe development of the molecular forms of acetylcholinesterase was studied in rat heart during the perinatal period. In this study, the activity of acetylcholinesterase increased both per unit wet weight and per unit protein from post‐conception day 14 to day 42. Additionally, the activity of atrial acetylcholinesterase per unit wet weight increased more rapidly after birth than that of ventricular acetylcholinesterase. The percent contribution of the various molecular forms to the total acetylcholinesterase pool in heart changed dramatically from the fetal to the neonatal period. This switch primarily consisted of a decrease in the ratio of the asymmetric to globular forms. Thus, the specific activity of globular forms increased while that of the asymmetric forms remained relatively stable. When the atria and ventricles were examined separately at 19 days post‐conception, the percent contribution of the individual molecular forms in the two cardiac areas was different. The atria contained a pool of acetylcholinesterase forms similar to postnatal heart while the ventricles contained a pool of acetylcholinesterase forms with a lower globular to asymmetric ratio. Finally, this study showed that greater than half of the acetylcholinesterase pool was inhibited by incubating hearts from fetal rats with echothiopate iodide, suggesting that a large portion of acetylcholinesterase catalytic sites are externalized in fetal heart.
Developmental profiles of cholinergic activity in the habenulae and interpeduncular nucleus of the rat
Authors: Contestabile A. , Virgili M. , Barnabei O. 
Published: April 2003

AbstractCholine acetyltransferase (ChAT) was measured in the habenula and in the interpeduncular nucleus of rats from 1 to 12 weeks of age. A remarkable degree of parallelism was shown by the developmental curves in the two nuclei. In both cases the highest level of enzyme activity was reached at 3 weeks of age and was followed by some decrease towards adult values. A statistically highly significant correlation was demonstrated between ChAT levels in the two nuclei at the various developmental stages. The rise of the cholinergic marker was slightly advanced in the habenula in comparison with the interpeduncular nucleus. The present data may be useful for studies focused on neonatal synaptogenesis, plasticity and synaptic neurochemistry of this relatively simple model of brain connections.
Accelerated neuromuscular development in the rat with prenatal exposure to nicotine
Authors: Rose Kenneth J. , Strand Fleur L. 
Published: April 2003

AbstractNicotine, administered to pregnant Sprague‐Dawley rats either throughout gestation or during two selective prenatal periods before or after muscular innervation (i.e. before or after gestational day 13), accelerated the maturation of developing nerve and muscle as viewed in 2‐week‐old offspring. Prenatal treatment of rats with nicotine (tartrate salt; 0.25 mg/kg twice a day; i.p.) induced marked changes in the contractile force and speed of the developing extensor digitorum longus (EDL) muscle when tested in situ on 14 to 15‐day‐old pups. In all nicotine treatment groups isometric twitch and tetanus half contraction durations were shorter than controls. Use of 2,3,5‐triphenyltetrazolium chloride, a biochemical indicator for cellular respiration, showed that totigestational nicotine administration increases cellular metabolic activity of EDL muscle. Hypertrophy of adrenal glands in these animals also was noted. While each of the three courses of nicotine administration accelerated muscle development and maturation, nicotine during the first half of prenatal development, prior to EDL muscle innervation, produced a more dramatic effect than nicotine during the second half of prenatal life.
Multi‐determinate regulation of neuronal survival: Neuropeptides, excitatory amino acids and bioelectric activity
Authors: Brenneman Douglas E. , Chang Yu , Nelson Phillip G. 
Published: April 2003

AbstractNeuronal survival of dorsal root ganglion‐spinal cord cultures was determined after treatment with vasoactive intestinal peptide (VIP) and an antagonist to the N‐methyl‐d‐aspartate receptor (NMDA). Blockade of NMDA receptors with 2‐amino 5‐phosphonovaleric acid (AP5) produced a bi‐phasic response on neuronal survival: low concentrations (0.1 μM) resulting in greater survival and higher concentrations (100 μM) causing cell death. VIP, a substance with demonstrated neurotrophic properties in vitro, prevented the neuronal cell death associated with high concentrations of AP5, while having no additive effect on the survival‐promoting action of low levels of AP5. Electrophysiological studies indicated that APS, although reducing high frequency bursting activity, did not significantly reduce the abundant on‐going asynchronous activity present in these cultures of high density neuronal networks. These data indicate that excitatory amino acids have more than one action that can influence neuronal survival during development and that VIP can increase neuronal survival in bioelectrically active cultures when NMDA channels are blocked. Together with previous studies, these data suggest that multiple neurochemical inputs serve to determine the survival of spinal cord neurons during development, perhaps through one final common pathway: intracellular calcium regulation.
Oxidative mechanisms underlying methyl mercury neurotoxicity
Authors: Sarafian T. , Verity M. Anthony 
Published: April 2003

AbstractCerebellar granule cells from 5–12‐day‐old rats can be incubated in suspension at 37°C for up to 3 hr with minimal decline in viability. Methyl mercury was found to produce time‐ and concentrationdependent cell killing with >85% cell death after 3 hr exposure to a concentration of 20 μM. Previously characterized inhibition of protein and RNA synthesis as well as known methyl mercury‐induced defects in cellular ATP production have been shown to be incapable of causing this degree of cell death. Here we report that methyl mercury induced a concentration‐dependent increase in membrane lipoperoxidation and a rapid decline in reduced glutathione in this cerebellar neuronal preparation. Hydrogen peroxide at 5 mM was found to closely reproduce each of the cytotoxic effects manifested by methyl mercury suggesting that oxidizing conditions produced by methyl mercury may account for the observed cell death. Methyl mercury‐induced lipoperoxidation was not the cause of cell death since malonaldehyde production could be blocked by α‐tocopherol or EDTA without appreciably protecting against cell death. Significant protection from methyl mercury‐induced cell death was observed, with EGTA, deferoxamine and KCN. We propose that oxidative events contribute to the toxic mechanism of action of methyl mercury in isolated cerebellar granule neurons.
Effect of vitamin E succinate and a cAMP‐Stimulating agent on the expression of c‐myc, N‐myc and H‐ras in murine neuroblastoma cells
Authors: Cohrs Randall J. , Torelli Sylvia , Prasad Kedar N. , Edwards‐Prasad Judith , Sharma Opendra K. 
Published: April 2003

Abstractd‐Alpha‐tocopheryl succinate (vitamin E succinate) at a concentration of 11.3 μM inhibited growth and reduced the expression of c‐myc, N‐myc and H‐ras specific mRNAs in murine neuroblastoma cells (NBP2) in culture. R020‐1724 [4‐(3‐butoxy‐4‐methoxybenzyl)‐2‐imidazolidinone], an inhibitor of cyclic AMP phosphodiesterase, also inhibited growth and reduced the expression of these oncogenes. Vitamin E succinate treatment caused the formation of two c‐myc related transcripts of 1.9 and 3.7 kb; however, R020‐1724 treatment did not. These results suggest that the inhibition of growth is sufficient to reduce the expression of c‐myc, N‐myc and H‐ras in NB cells in culture, but it is not sufficient to produce two c‐myc related transcripts.
Myelination and glial ensheathment of purkinje cells in cerebellar cultures are not inhibited by antibodies to the neural cell adhesion molecule, N‐CAM
Authors: Seil Fredrick J. , Herndon Robert M. 
Published: April 2003

AbstractMouse cerebellar cultures were exposed to anti‐N‐CAM antibodies throughout their in vitro development. Some cultures were stripped of myelinating oligodendrocytes and functionally competent astrocytes by treatment with cytosine arabinoside (Ara C), while others were left untreated and were potentially capable of forming myelin around axons and astrocytic sheaths around Purkinje cell somata and dendrites. As expected, the antibodies inhibited axonal fasciculation in the Ara C treated cultures. However, the same antibodies had no discernible effect on formation of myelin or astrocytic sheaths in cultures not treated with Ara C. N‐CAM is expressed on the surfaces of neurons, oligodendroglia and astrocytes, and has been proposed as the signal molecule governing both kinds of neuron‐glia interactions. The observations of the present study strongly suggest, however, that N‐CAM does not have an indispensable role in such interactions.
Parallel expression of synaptophysin and evoked neurotransmitter release during development of cultured neurons
Authors: Ehrhart‐Bornstein Monika , Treiman Marek , Hansen Gert H. , Schousboe Arne , Thorn Niels A. , Frandsen Aase 
Published: April 2003

AbstractPrimary cultures of GABAergic cerebral cortex neurons and glutamatergic cerebellar granule cells were used to study the expression of synaptophysin, a synaptic vesicle marker protein, along with the ability of each cell type to release neurotransmitter upon stimulation. The synaptophysin expression and neurotransmitter release were measured in each of the culture types as a function of development for up to 8 days in vitro, using the same batch of cells for both sets of measurements to obtain optimal comparisons. The content and the distribution of synaptophysin in the developing cells were assessed by quantitative immunoblotting and light microscope immunocytochemistry, respectively. In both cell types, a close parallelism was found between the temporal pattern of development in synaptophysin expression and neurotransmitter release. This temporal pattern differed between the two types of neurons. The cerebral cortex neurons showed a biphasic time course of increase in synaptophysin content, paralleled by a biphasic pattern of development in their ability to release [3H]GABA in response to depolarization by glutamate or elevated K+ concentrations. In contrast, a monophasic, approximately linear increase in the synaptophysin content and stimulated [3H]D‐aspartate release was found in the cerebellar granule cells. These results, particularly regarding the GABAergic neurons, offer correlative evidence in support of the notion that a vesicular pool of these amino acid neurotransmitters may be intimately involved in their release, subsequent to depolarization stimuli.
Chronic blockade of bioelectric activity in neonatal rat cortex grown in vitro: Morphological effects
Authors: Ruijter J.M. , Baker R.E. , De Jong B.M. , Romijn H.J. 
Published: April 2003

AbstractCulture thickness, numerical density of neurons and neuronal survival were studied in timed series of control and tetrodotoxin‐silenced neocortical cultures to provide information on the role of bioelectric activity on neuronal development. In control cultures, culture thickness and number of surviving neurons decrease during the first weeks in vitro, but remain constant between 2 and 3 weeks indicating that the cultures are essentially mature. In the 4th week in vitro a further decrease in surviving neurons was observed. In tetrodotoxin‐treated cultures the number of surviving neurons decreased significantly between 1 and 2 weeks in vitro, to remain constant thereafter. However, culture thickness significantly increased at 3 and 4 weeks in vitro after an initial drop between 1 and 2 weeks. Compared to age‐matched controls at 2 and 3 weeks in vitro, only ca 50% of the neurons survived the loss of bioelectric activity. Similar differences were present between 1 and 2 weeks. Thus, the loss of all measurable bioelectric activity induces neuronal death in neocortical explants, but promotes neuropil formation by the surviving cells.
Extrafusal and intrafusal motor units in the kitten
Authors: Gregory J.E. , Proske U. 
Published: April 2003

AbstractIn the lateral flexor digitorum longus muscle (FDL) of anaesthetized kittens aged 3–21 days, alpha (α) and gamma (γ) motoneurone conduction velocities were measured together with motor unit tensions. Conduction velocity lay in the range 8–27 msec−1 for α motoneurones and 2–10 msec−1 for γ motoneurones. Motor unit tetanic tensions were 3–47 mN with the largest units being 2–2.2% of whole muscle tension. The hypothesis was tested that motor axons conducting within the γ range and presumed to be innervating the intrafusal fibres of muscle spindles, on stimulation, produced measurable tension. Stimulating γ motoneurones in the adult produces no tension. The hypothesis was based on histological observations that while in the adult, intrafusal fibres were about one third of the size of extrafusal fibres, in kittens the two were nearly equal, both in length and diameter. It was shown by means of signal averaging during stimulation of ventral root filaments that whenever tension was recorded in the muscle an impulse could be detected in the muscle nerve conducting at α motoneurone tempo. It is concluded that in the kitten, despite the fact that intrafusal and extrafusal fibres are of similar size, stimulating single γ motoneurones does not develop measurable tension.
Activation of muscarinic cholinergic receptors stimulates inositol phosphates synthesis in the developing avian cochlear duct
Authors: Bartolami Sylvain , Mayat Ebrahim , Lippe William R. , Rebillard Guy , Pujol Rémy 
Published: April 2003

AbstractWe previously reported that the inositol phosphates (IPs) synthesis is induced by muscarinic agonists in the rat cochlea and that this stimulation is maximal at postnatal day 12. This peak response is concomitant with the onset of the efferent synaptogenesis at the outer hair cell level. Whether the correlation between this neuronal plasticity and the enhanced IPs formation is unique to the rat or a general feature of the developing vertebrate cochlea is not known. To examine this question, we measured, in the presence of LiCl, the accumulation of (3H)‐IPs induced by carbachol, in the developing chick cochlear duct during a period ranging from embryonic day (E) 8 to post‐hatching day (P) 20. Carbachol (1 mM) causes a significant increase of IPs formation relative to basal values at all ages. This IPs accumulation is maximal at E8 (1854% of the basal level), then, rapidly decreases until P13 when it reaches a steady‐state level of 294% of the basal level. Strikingly, this gradual decline in IPs formation is interrupted between E15 and E19, by a transient increase in IPs synthesis. This rise peaks at E16 with a stimulation value of 757% of the control level. This maximal stimulation is inhibited by atropine in a dose‐dependent manner, as is the case at E9, suggesting the involvement of muscarinic receptors. Interestingly, the occurrence of the peak response is concomitant with the plastic events associated with the maturation of the efferent innervation of the cochlear duct. Thus, these results suggest that there may be a correlation between cochlear plasticity and enhanced IPs synthesis, which is not species‐specific. The possible significance of the overall decrease in IPs formation, occurring during embryonic development, is discussed.
Different degradation rates of junctional and extrajunctional acetylcholine receptors of human muscle cultured in monolayer and innervated by fetal rat spinal cord neurons
Authors: Braun Serge , Askanas Valerie , Engel W. King 
Published: April 2003

AbstractIt is well demonstrated that in intact animals the degradation rate of the junctional acetylcholine receptor (AChR) is significantly slower than that of the extrajunctional receptor. Such data, however, are not available for human AChRs because the required experimentation cannot be performed in humans. We have now studied the degradation rate of the junctional and extrajunctional AChRs, utilizing our tissue culture model, in which well‐differentiated neuromuscular junctions (NMJs) form on human muscle cultured in monolayer and innervated long‐term by fetal rat spinal cord neurons. Half‐life of AChRs was studied by a method utilizing the autoradiography of 125I‐αbungarotoxin and computerized video image analysis. Extrajunctional AChRs degraded with a half‐life of 1.3 days whereas junctional AChRs degraded with a half‐life of 3.5 days. Our studies demonstrate for the first time that in innervated cultured human muscle: (a) the life span of human junctional AChR, is approximately 3 times longer than that of the extrajunctional AChR and (b) the stability of human AChR is neuronally regulated. This system can now be applied to evaluate the influence of pharmacologie agents on the stability of human junctional AChR, which is of potential importance in the treatment of myasthenia gravis and other diseases of the NMJ.