bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plasminogen activator secretion in relation to Schwann cell activities
Authors: Krystosek Alphonse , Verrall Shahla , Seeds Nicholas W. 
Published: April 2003

AbstractThe molecular characterization of neural secretory plasminogen activators and their possible association with two well‐defined Schwann cell activities (mitosis and migration) were investigated. Schwann cells from peripheral sensory ganglion roots were established as primary cultures of high purity. Conditioned culture medium was fractionated by gel electrophoresis and assayed for plasminogendependent in situ caseinolytic activity. Both tissue‐type and urokinase‐type plasminogen activators were detected early in culture. The amount of the tissue‐type form decreased with increasing time in culture. Proliferative ability measured as [3H]thymidine incorporation into the nucleus varied under several culture conditions and was lowest in defined serum‐free medium; however, these serum‐free cultures expressed the highest level of plasminogen activator secreting cells. Combined autoradiography/fibrin overlay assays allowed for a direct analysis at the single cell level; interestingly the findings did not support the idea of an obligatory expression of the enzyme in replicating cells. Cell motility was assayed in combined gold particle clearing/fibrin overlay assays and likewise no obligatory association of protease secretion and cell movement could be demonstrated. The results are discussed in relation to previous tudies in this field.
Ontogeny of the opiate phenotype: An approach to defining transsynaptic mechanisms at the molecular level in the rat adrenal medulla
Authors: La Gamma E. F. , De Cristofaro J. D. , Agarwal B. L. , Weisinger G. 
Published: April 2003

AbstractTransmitter phenotypic expressions is a dynamic cellular process governed by multiple interactions with the neuronal environment. During sympathoadrenal development the arrival of presynaptic nerve terminals at the adrenal chromaffin cell (in the immediate postnatal period), coincides with the acquisition and subsequent development of a variety of transmitter biosynthetic capacities. Data discussed herein supports the contention that synaptic connections serve a central role in triggering the ontological cascade. Disruption of the normal timing of innervation events is detrimental to subsequent function and results in permanent deficiencies in development. In addition, alteration of transmitter biosynthetic regulatory mechanisms appears to reside at the level of gene expression. In view of this, additional molecular approaches are necessary to further elucidate the fundamental basis of neuronal transmitter phenotypic plasticity. Our approach to this problem represents a logical extension of previous research in this area and ultimately, will involve characterizing transcription activator molecules important in transmitter gene expression at various ontological ages.
Co‐localization and plasticity of transmitters in peripheral autonomic and sensory neurons
Authors: Morris J. L. , Gibbins I. L. 
Published: April 2003

AbstractImmunohistochemical studies have shown that most peripheral autonomic and sensory ganglia are heterogeneous, consisting of several populations of neurons which can be distinguished by their content of peptide and non‐peptide transmitters and transmitter‐associated enzymes. Many neurons contain several different potential transmitters, especially neuropeptides. Some neuropeptides have been localized in more than one population of autonomic and sensory neurons. However, the peptide often occurs together with a distinctive combination of additional transmitters in each neuronal class. The precise combination of transmitters found in any individual neuron is highly correlated with the peripheral target of the neuron. This indicates that immunohistochemically defined neuronal populations represent distinct functional classes of neurons. In an increasing number of cases, many of the potential transmitters contained in a particular neuron have been shown to be released from the nerve terminals, and to contribute to presynaptic or postsynaptic effects of nerve activation. Despite this association between the combination of potential transmitters contained in a neuron, and the function of the neuron, not all transmitters or transmitter‐associated enzymes are expressed equally at all times in the life of a neuron: the levels of some substances change dramatically during development; some are detected only after experimental alteration of the environment of the developing or mature neurons. Taken together, these results indicate that, during development, pathway‐specific information influences the differentiation of peripheral autonomic and sensory neurons. Furthermore, the expression of neuropeptides and transmitter‐associated enzymes in a particular neuron appears to be under continuous regulation. These phenomena demonstrate the complexity and precision involved in development and maintenance of the peripheral autonomic and sensory nervous systems.
Influence of glycosaminoglycans on neurite morphology and outgrowth patterns in vitro
Authors: Verna Jean‐Marc , Fichard Agnes , Saxod Raymond 
Published: April 2003

AbstractThe neuritic growth patterns obtained on substrates made of several glycosaminoglycans (GAGs) bound to type I collagen were analysed and compared in primary cultures of chick embryo dorsal root ganglion grown in serum‐free supplemented medium. In 2‐day cultures grown on type I collagen or heparan sulphate (HS)‐ collagen surfaces, ganglionic expiants exhibit a dense, symmetrical network of long, parallel neuritic processes and very few flat migrating non‐neuronal cells. In contrast, on either dermatan sulphate (DS), chondroitin‐6‐sulphate (C6S) or hyaluronic acid (HA)‐bound collagen substrates, neurons form irregular nerve fibre patterns; indeed, neuntes follow convoluted paths and often, after abrupt turns, totally reverse their direction of extension. Experiments were carried out in which a choice was given to growing neural processes between collagen or GAG‐collagen substrates. While growth cones elongating over type I collagen easily cross the border with HS‐bound collagen surface and indiscriminately extend on this substrate, in contrast, neurites generally avoid surfaces coated with DS, C6S or HA and change their direction of growth in order to stay on collagen. The binding of DS, C6S or HA, but not HS, to type I collagen thus decreases its ability to promote neurite elongation. The interaction of neuronal cells with these extracellular matrix components by restricting neurites in their paths of extension may, therefore, play a role in the patterning of the nervous circuitry.
Characterization of resting membrane potential and its electrogenic pump component in cultured chick myotubes
Authors: Brodie Chaya , Sampson S. R. 
Published: April 2003

AbstractThe role of the electrogenic Na+‐K+ pump in the determination of the level of the resting membrane potential in cultured chick limb muscle was investigated. Transmembrane resting potential and ouabain‐sensitive86Rb‐uptake were measured in myotubes at different ages in culture from 2 to 10 daysin vitro. Inhibition of the Na+‐K+ pump with ouabain prevented the developmental increase in membrane potential which normally follows fusion of myotubes (day 2–3). In mature myotubes, ouabain caused a dose‐related decrease in both membrane potential and86Rb‐uptake, with values for EC50 and maximal effect being nearly the same on both variables. The decrease in membrane potential by ouabain, up to 20 mV maximum, occurred within 2–5 sec and was not accompanied by detectable changes in input resistance. Membrane potential was also reduced by a decrease in temperature of the recording medium and removal of extracellular K+, both of which reduce Na+‐K+ pump activity. We also found that the relation between membrane potential and extracellular K+ concentration was completely attenuated by ouabain in the physiological range (2–10 mM). We conclude that the electrogenic Na+‐K+ pump plays an important role in the determination of the resting membrane potential of chick myotubes and that regulation of its level is not entirely explained by the diffusion potential hypothesis.
Glial‐conditioned medium and attachment to ConA are essential for long‐term culture of cortical neurons
Authors: Bauer H. C. , Tontsch U. 
Published: April 2003

AbstractCortical brain cells from 14‐day‐old mouse embryos were seeded on various substrates and cultivated in serum‐free medium with or without conditioned medium from astrocytes or C6 glioma cells. Poly‐l‐lysine was shown to be the best substrate for cell attachment followed by Concanavalin A (ConA) and adhesion particles derived from glia cells. Cells grown on ConA sprouted rapidly and formed large networks. Survival of neurons was greatly prolonged when glia‐conditioned medium (GCM) was present in the culture medium. Cells grown on ConA were then viable for more than 4 weeks. Without GCM, neurons survived in culture for about 2 weeks, regardless of the substrate. Endothelial cell growth supplement or acidic fibroblast growth factor increased survival of neurons but also stimulated proliferation of astrocytes.
Calcium and calmodulin levels in late embryonic and early hatched japanese quail brain
Authors: Alston‐Mills Brenda , Shankarappa Basavaraju , Douglass Larry 
Published: April 2003

AbstractCharacterizing the last phases of embryonic avian brain development are increased brain activity and increased absorption of shell calcium. The calcium‐binding protein, calmodulin, regulates many activities of calcium. In neural tissue, calmodulin modulates neural transmission, and is required for the phosphorylation of synaptosomal proteins. Therefore, the objective was to compare levels of brain calcium and calmodulin in the Japanese quail. Brain extracts from embryonic days 11, 15, hatch, and 5 days post‐hatch (n = 7/group) were analysed for calcium, protein and calmodulin. Despite increases in protein between embryonic ( = 0.126 and 0.145 mg/mg wet wt) and hatched groups ( = 0.183 and 0.221 mg), no significant increases in calmodulin were observed (237–279 ng/mg protein). Calcium levels in the brain were U‐shaped with low levels at embryonic day 1 (341 μg/mg wet wt) and post‐hatch day 5 (315 μg/mg wet wt) with higher levels on embryonic day 15 (425 μg/mg wet wt) and at hatch (433 μg/mg wet wt). Calmodulin levels do not show a developmental pattern similar to calcium and protein levels or with reports of brain activity.
Postnatal development of the excitatory amino acid system in visual cortex of the rat. Changes in ligand binding to NMDA, quisqualate and kainate receptors
Authors: Erdö Sandor L. , Wolff Joachim R. 
Published: April 2003

AbstractThe postnatal development of the ligand binding to N‐methyl‐d‐aspartate (NMDA), quisqualate and kainate receptor sites was examined in whole homogenates of the visual cortex of rats, aged 2–360 days. As selective ligands, [3H]CPP (3‐(2‐carboxypyperazine‐4‐yl)‐propyl‐1‐phosphonic acid, [3H]AMPA (RS‐alpha‐amino‐3‐hydroxy‐5‐methyl‐isoxazole‐4‐propionic acid) and [3H]KA (kainic acid) were used, respectively. The binding of CPP was low in newborns, rapidly increased from the second postnatal week, reached its maximum between weeks 2 and 3, then slowly declined up to the age of 1 year. In contrast, the binding of AMPA and kainate was high perinatally, increased rapidly up to day 6 after birth to reach an early maximum value, then gradually decreased to adult values which were attained at an age of 3–4 weeks. These age‐related changes were derived from alterations in the density of binding sites, which, in the case of AMPA, was accompanied by an increase in binding affinity. The results, compared with the developmental time‐course of excitatory synapses, indicate that, in the immature cerebral cortex, NMDA receptors may be primarily involved in synaptic transmission, whereas quisqualate and kainate receptors may play some other (e.g. trophic) roles.
Aging increases calcium influx at motor nerve terminal
Authors: Alshuaib Waleed B. , Fahim Mohamed A. 
Published: April 2003

AbstractTo determine whether increased transmitter release from soleus nerve terminals of old C57BL/6J mice is caused by an altered Ca2+ regulation, the time course of post‐tetanic potentiation of miniature endplate potential (MEPP) frequency was used as an indicator of the kinetics of Ca2+ metabolism in young (10 months) and old (24 months) mice. Post‐tetanic potentiation properties were studied in either (1) 0.2 mM Ca2+, 5.0 mM Mg2+ Krebs; or (2) Ca2+‐free/EGTA Krebs to eliminate Ca2+ influx, and thereby isolated Ca2+ buffering. In the 0.2 mM Ca2+ Krebs, the time constants of decay of augmentation (TA) and potentiation (TP) were longer in old (TA = 10.3 ± 1.0 sec, TP = 195.3 ± 5.4 sec) than in young (TA = 7.0 ± 0.7 sec, TP = 78.8 ± 6.6 sec) nerve terminals. Evoked transmitter release was measured in 0.4 mM Ca2+, 2.75 mM Mg2+ Krebs. Quantal content of the endplate potential was positively correlated with TA (r = 0.95) and with TP (r = 0.98). In the Ca2+‐free/EGTA Krebs, there was no difference in post‐tetanic potentiation properties between young and old terminals. These results suggest that Ca2+ influx into the soleus nerve terminal increases with aging. This may explain, at least in part, the increased quantal content observed at old terminals.
Glia protect hippocampal neurons against excitatory amino acid‐induced degeneration: Involvement of fibroblast growth factor
Authors: Mattson Mark P. , Rychlik Barbara 
Published: April 2003

AbstractLow density cell cultures of embryonic rat hippocampus containing astrocyte‐like glia and neurons were used to test the hypothesis that glia can alter ‘natural’ and excitatory amino acid (EAA)‐induced neuronal death. Neurons contacting glia survived for longer time periods than did neurons not contacting glia. Neurons associated with glia were also protected against glutamate and kainate neurotoxicity. Fibroblast growth factor (FGF)‐like immunoreactivity was associated with the glia. Addition to the cultures of an antiserum raised against an internal peptide fragment of FGF greatly reduced the protective effect of glia against both spontaneous and EAA‐induced neurotoxicity. Contact with glia, or exposure to exogenous FGF, also protected the hippocampal neurons against Ca2+ ionophore‐induced degeneration indicating that FGF enhanced the ability of neurons to handle a Ca2+ load. Taken together, these results suggest that glia surface‐associated FGF may play important roles in hippocampal development, and in neurodegenerative conditions that involve EAAs.
Regional ontogeny of a unique glutamate recognition site in rat brain: An autoradiographic study
Authors: Greenamyre J. Timothy , Higgins Donald S. , Young Anne B. , Penney John B. 
Published: April 2003

AbstractThe developmental pattern of l‐[3H]glutamate binding to rat brain in the presence of saturating concentrations of unlabeled N‐methyl‐d‐aspartate (NMDA), kainate (KA) and quisqualate (OQA) was examined in an autoradiographic assay. The unique glutamate binding site defined by this assay displayed four distinct, regionally specific patterns of development. (1) In reticular nucleus of thalamus there was an initial very high level of binding at postnatal day 1 (PND1) followed by a progressive 80% decline in binding during maturation. (2) In entorhinal cortex, a progressive 500–1100% increase in binding was seen during development. (3) In ventral posterior medial nucleus of thalamus, there was an initial transient 200–300% increase in binding, peaking at PND10, followed by a steady decline in binding. (4) In frontal cortex, binding remained relatively stable throughout development. At all stages of development, the distribution of these recognition sites was different from NMDA, KA or QQA receptors. The function of this glutamate binding site remains to be determined, but the distinct regional and temporal patterns of binding suggest that it may be important in normal development of the central nervous system.
Fetal alcohol effects: Decreased synaptic formations in the field CA3 of fetal hippocampus
Authors: Tanaka Harumi , Nasu Fumio , Inomata Kenichirou 
Published: April 2003

AbstractThe effects of prenatal ethanol exposure on the synaptic formation in the field CA3 of the hippocampus of fetal rats have been investigated on gestational day 21. Significantly decreased number of synaptic junctions was observed in the fetus showing decreasing cerebral weight either with or without decreasing body weight. The administration of 0.01% zinc with ethanol or 0.02% α‐tocopherol acetate with ethanol during pregnancy resulted in an increased cerebral weight, but did not result in an increased synaptic formation compared to ethanol alone. This result indicates that one of the most vulnerable factors in rat fetus exposed to ethanol in utero is the synaptic formation in the hippocampus. In conclusion, ethanol exposure in utero during a period of brain development roughly equivalent to the first and second human trimesters can produce consistent dysforming effect of synapses and may be associated with the functional impairment of the central nervous system in the fetal alcohol effects.
Chronic blockade of bioelectric activity in neonatal rat neocortex in vitro: Physiological effects
Authors: Baker Robert E. , Ruijter Jan M. 
Published: April 2003

AbstractWe have examined what effect the loss of spontaneous bioelectric activity has on neural network formation in organotypic rat neocortical explants grown under serum‐free culture conditions. Explants were taken from dorsal midline (presumptive visual) and lateral (presumptive auditory) occipital cortex and chronically exposed to tetrodotoxin which blocked all measurable bioelectric activity between change of medium. Extracellular recordings revealed complex, rhythmic spontaneous and evoked multiunit discharges in all explants examined (following tetrodotoxin washout in the experimental group). Control auditory explants had significantly more sites from which electric activity could be recorded compared with control visual explants. Auditory cultures showed no effect of the tetrodotoxin treatment, whereas visual explants showed significant increases over control values, equalling the auditory values. This increased level of spontaneous bioelectric activity was maintained for at least 10 days following transfer of the cultures to control growth medium. There was no significant difference between control visual and auditory explants regarding the number of sites from which evoked activity was seen. Nor did either cortex group show an effect of tetrodotoxin on the number of sites from which evoked activity was seen. The frequency with which spontaneous bioelectric discharges occurred per site increased with age in auditory vs visual cortex. These differences, however, were abolished in the tetrodotoxin‐treated groups. It was concluded that neocortical explants which have experienced chronic suppression of spontaneous electric activity did not suffer deficits in neural network formation, though there is an effect on the incidence and frequency with which such activity is given.
Muscle‐derived factors enhance cholinergic neuronal expression in the chick embryo—II. In culture studies
Authors: Brodie Chaya , Vernadakis Antonia 
Published: April 2003

AbstractThe effects of muscle‐derived factors on the cholinergic and GABAergic neuronal phenotypes were studied in cultures derived from 3‐day‐old whole chick embryo (E3WE) consisting of proliferating neuroblasts and 8‐day‐old chick embryo cerebral hemispheres (E8CH) consisting of differentiated neurons. The effects of limb muscle extract (LME) were examined either when added to the culture medium or to the polylysine coating substratum cultures. We also compared the effects of LME derived from 8‐ to 15‐day‐old chick embryos. We found that LME added to the medium not only increased choline acetyltransferase activity, a marker for cholinergic neurons throughout the development of neurons in E3WE or E8CH culture, but also delayed the decline in the activity observed in untreated cultures. The marked increase in choline acetyltransferase activity in E8CH cultures grown on substratum‐bound LME as compared to those grown in medium‐containing LME, suggests that LME factors may be adhesion‐promoting substances stimulating neuronal growth. These findings provide evidence that muscle‐derived factors may be important in early cholinergic phenotypic expression and support our previous in ovo studies indicating that target‐derived factors in limb muscle extract have general cholinotrophic effect.
Matrigel enhances myotube development in a serum‐free defined medium
Authors: Lyles Joan M. , Amin Waheeda , Weill Cheryl L. 
Published: April 2003

AbstractPreviously reported serum‐free defined media for muscle cell culture require supplementation with hormones, purified growth factors or attachment factors. This report describes a culture system that enhances embryonic chick, skeletal muscle cell growth and differentiation in a serum‐free defined medium, without added specialized trophic factors. Myoblasts adhered more to and proliferated more rapidly on a reconstituted basement membrane substrate, Matrigel, than on rat‐tail collagen. Matrigel contains several basement membrane attachment molecules which apparently obviate the need for added purified attachment factors. Matrigel also appeared to play a trophic role in subsequent development by enabling the serum‐free growth of myotubes which suggests that Matrigel mediates the cellular interaction of growth or attachment factors. Collagen, on the other hand, did not support serum‐free myotube growth. Supplementation of defined medium with increasing levels of horse serum enhanced total protein in myotubes grown on both substrates; protein was higher in Matrigel cultures for each medium tested. The serum‐free defined medium supported complete morphological differentiation of myotubes grown on Matrigel and maintained myotube cultures up to 22 days. Fibroblast proliferation was higher in cultures on collagen in defined medium with high serum levels, but was virtually eliminated in cultures on Matrigel in serum‐free defined medium. The culture system described supports the differentiation of embryonic muscle cells in a simple, serum‐free defined medium, thus providing an in vitro model of developing myotubes which should be particularly useful for studies of regulation mediated by extracellular factors.
Distribution of cholinergic neurons in the chick spinal cord during embryonic development. Comparison of ChAT immunocytochemistry with AChE histochemistry
Authors: Thiriet G. , Kempf J. , Ebel A. 
Published: April 2003

AbstractThe location of cholinergic neurons was studied during the development of the chick embryo spinal cord. A comparison between choline acetyltransferase (ChAT) immunocytochemistry and acetylcholinesterase (AChE) histochemistry was performed. ChAT‐positive neurons could be detected only from embryonic day 9 (E9) onwards by the FITC technique and from E12 onwards by the PAP technique. These neurons were located mainly in the medial and lateral motor columns in the ventral horn of the gray matter and some of them were observed in the intermediate region of the spinal cord. AChE‐containing cell bodies were much more numerous than the ChAT immunoreactive ones and were distributed in the ventral horn of the gray matter, the intermediate gray region and mostly off the apical part of the dorsal horn. ChAT should provide a reliable and specific marker for cholinergic neurons.